Tesis sobre el tema "Nonlinear static (pushover) analysis"

The main objective of this investigation is to examine how various material properties, governed by code specification, affect the seismic response of a twelve- story reinforced concrete building. This study incorporates the pushover and response history analysis to examine how varying steel yield strength (Fy), 28 day nominal compressive concrete strength (f’c), modes, and ground motions may affect the base shear capacity and displacements of a reinforced concrete structure. Different steel and concrete strengths were found to have minimal impact on the initial stiffness of the structure. However, during the post-yielding phase, higher steel and concrete compressive strengths resulted in larger base shear capacities of up to 22%. The base shear capacity geometric median increased as f’c or Fy increased, and the base shear capacity dispersion measure decreased as f’c or Fy increased. Higher mode results were neglected in this study due to non-convergent pushover analyses results. According to the response history analysis, larger yield and concrete compressive strengths result in lower roof displacement. The difference in roof displacement was less than 12% throughout. This displays the robustness of both analysis methods because material properties have insignificant impact on seismic response. Therefore, acceptable yield and compressive strengths governed by seismic code will result in acceptable building performance.

En la presente investigación se realizará el análisis y diseño estructural de una torre de 40 pisos y 4 sótanos de concreto armado siguiendo normas peruanas y el cálculo de desempeño sísmico en el distrito de Santiago de Surco, Lima. Para esto, la hipótesis plantea sí las normas peruanas cumplen con el desempeño sismorresistente deseado para una torre alta como esta. Para un entendimiento progresivo, primero se hará una descripción de la torre alta a estudiar, su arquitectura, estructura, suelo y otros. En la segunda parte se darán los conceptos necesarios para comprender los tipos de análisis lineal estático, lineal dinámico y no lineal estático. Se definirán los materiales, los diagramas momento – rotación también se explicará la obtención de la curva de capacidad del edificio. Se tocarán conceptos de viento y nivel de desempeño. En la tercera parte, se procederá con en análisis sísmico cumpliendo las exigencias de sismorresistencia, también se hará el análisis por viento para comparar ambos efectos. En el capítulo cuarto se procederá a hacer el diseño estructural usando las normas de concreto armado. En el capítulo cinco se hará el análisis por desempeño usando el método pushover para finalmente conseguir los resultados de este proyecto y a las conclusiones de este desarrollo.
In the present investigation, the analysis and structural design of a 40-storey tower and 4 reinforced concrete basements will be carried out following Peruvian regulations and the calculation of seismic performance in the Santiago de Surco district, Lima. For this, the hypothesis states whether the Peruvian standards meet the desired seismic resistance performance for a tall tower like this one. For a progressive understanding, first a description will be made of the tall tower to study, its architecture, structure, soil and others. In the second part, the concepts necessary to understand the types of static linear analysis, dynamic linear analysis and static non-linear analysis will be given. The materials will be defined, the moment - rotation diagrams will also explain the obtaining of the building capacity curve. Wind and performance level concepts will be discussed. In the third part, we will proceed with seismic analysis complying with the seismic resistance requirements, we will also do the wind analysis to compare both effects. In the fourth chapter, the structural design will be carried out using the reinforced concrete standards. In chapter five the performance analysis will be done using the pushover method to finally get the results of this project and the conclusions of this development.
Tesis

Debido al alto peligro de ocurrencia de sismo, al que está expuesto el balneario de Pucusana y el crecimiento poblacional que ha tenido en los últimos años, hace necesario conocer los efectos que producirían un sismo de gran magnitud en esta localidad, según (Silgado, 1978), en el año 1746 ocurrió un sismo de magnitud estimada de 9.0 MW, seguido de un maremoto que destruyó el puerto del callao y según (Tavera, 2008), el área de estudio ocupa una zona de peligro estimado, se espera un sismo de magnitud 8.8 MW, producto de estos estudios se consideró escoger esta localidad como representativa para elaborar un escenario de riesgo sísmico. Ante esta realidad, se hace necesario elaborar escenarios de Riesgo para el balneario de Pucusana. Este trabajo de investigación pretende realizar una mejora a la propuesta realizada por el CENEPRED, en su manual de estimación del riesgo, utilizando el Análisis “PUSHOVER”, mediante la metodología ATC-40, el ASCE41-13 y SEAOC VISION 2000, que permitirá determinar la calidad de la estructura a detalle y compararla con el nivel de peligro de sismo que se tiene producto de los trabajos del proyecto SIRAD 2012. Se ha escogido para realizar este estudio el Mercado Municipal, debido a que es una de las estructuras más importantes del Balneario. Finalmente, el aporte de esta tesis es determinar el nivel de desempeño del mercado municipal de Pucusana, para la determinación del nivel de vulnerabilidad del mismo.
Due to the high danger of earthquake occurrence, to which the Pucusana city is exposed and the population growth that it has had in recent years, it is necessary to know the effects that a large earthquake would produce in this locality, according to (Silgado, 1978 ), in the year 1746 an earthquake of estimated magnitude of 9.0 MW occurred, followed by a tsunami that destroyed the port of Callao and according to (Tavera, 2008), the study area occupies an estimated danger zone, an earthquake of magnitude 8.8 MW, as a result of these studies, it is considered to choose this locality as representative to elaborate a seismic risk scenario. Given this reality, it is necessary to develop Risk scenarios for the Pucusana spa. This research work aims to make an improvement to the proposal made by CENEPRED, in its risk estimation manual, using the “PUSHOVER” Analysis, using the ATC-40 methodology, ASCE41-13 and SEAOC VISION 2000, which will determine the quality of the structure in detail and compare it with the level of earthquake danger that exists as a result of the work of the SIRAD 2012 project. The Municipal Market has been chosen to carry out this study, because it is one of the most important structures in the Spa. Finally, the contribution of this thesis is to determine the level of performance of the municipal market of Pucusana, to determine its level of vulnerability.
Tesis

Pushover analysis involves certain approximations and simplifications that some amount of variation is always expected to exist in seismic demand prediction of pushover analysis. In literature, some improved pushover procedures have been proposed to overcome the certain limitations of traditional pushover procedures. The effects and the accuracy of invariant lateral load patterns utilised in pushover analysis to predict the behavior imposed on the structure due to randomly selected individual ground motions causing elastic and various levels of nonlinear response were evaluated in this study. For this purpose, pushover analyses using various invariant lateral load patterns and Modal Pushover Analysis were performed on reinforced concrete and steel moment resisting frames covering a broad range of fundamental periods. Certain response parameters predicted by each pushover procedure were compared with the '
exact'
results obtained from nonlinear dynamic analysis. The primary observations from the study showed that the accuracy of the pushover results depends strongly on the load path, properties of the structure and the characteristics of the ground motion. Pushover analyses were performed by both DRAIN-2DX and SAP2000. Similar pushover results were obtained from the two different softwares employed in the study provided that similar approach is used in modeling the nonlinear properties of members as well as their structural features. The accuracy of approximate procedures utilised to estimate target displacement was also studied on frame structures. The accuracy of the predictions was observed to depend on the approximations involved in the theory of the procedures, structural properties and ground motion characteristics.

Thesis (M.S. in civil engineering)--Washington State University, December 2008.
Title from PDF title page (viewed on Apr. 10, 2009). "Department of Civil and Environmental Engineering." Includes bibliographical references (p. 127-133).

Beams are structural members with one dimension much larger than the other two. Examples of beams include propeller blades, helicopter rotor blades, and high aspect-ratio aircraft wings in aerospace engineering; shafts and wind turbine blades in mechanical engineering; towers, highways and bridges in civil engineering; and DNA modeling in biomedical engineering. Beam analysis includes two sets of equations: a generally linear two-dimensional problem over the cross-sectional plane and a nonlinear, global one-dimensional analysis. This research work deals with a relatively new set of equations for one-dimensional beam analysis, namely the so-called fully intrinsic equations. Fully intrinsic equations comprise a set of geometrically exact, nonlinear, first-order partial differential equations that is suitable for analyzing initially curved and twisted anisotropic beams. A fully intrinsic formulation is devoid of displacement and rotation variables, making it especially attractive because of the absence of singularities, infinite-degree nonlinearities, and other undesirable features associated with finite rotation variables. In spite of the advantages of these equations, using them with certain boundary conditions presents significant challenges. This research work will take a broad look at these challenges of modeling various boundary conditions when using the fully intrinsic equations. Hopefully it will clear the path for wider and easier use of the fully intrinsic equations in future research. This work also includes application of fully intrinsic equations in structural analysis of joined-wing aircraft, different rotor blade configuration and LCO analysis of HALE aircraft.

This thesis investigates the torsional performance of steel structures with and without rigid diaphragm constraints through numerical simulations and evaluates the appropriateness of relevant design provisions in current seismic design codes. In the first part of the work, six theme structures with different (1) in-plane stiffness of diaphragm, and (2) horizontal configurations of vertical braced frames were designed and their performance evaluated through both nonlinear static and dynamic analyses. Comparisons of the analytical results between the structures with and without rigid diaphragm constraints indicate that the in-plane rigidity of the diaphragms affects the efficiency of in-plane force transfer mechanisms, resulting in different global ductility and strength demands. Rigid diaphragm structures exhibit higher global strengths as well as higher torsional rotation capacity because of the infinite in-plane stiffness of the diaphragm. Semi-rigid diaphragm structures have higher ductility demands due to the finite in-plane diaphragm stiffness. The inclusion of bi-axial forces in the analyses reduces the structural strength and increases the ductility demands on the peripheral frames. The axial forces in the collectors and chords that make up the diaphragm depend on (1) the sequence of brace buckling and (2) vertical configuration of the braced frames. The results show higher axial forces in collectors in the roof diaphragms, and higher chord axial forces in the third floor diaphragms. The shear connections in the beams that make up both the collectors and chords are susceptible to failure due to the significant increment of axial forces in those members. The conventional beam analogy used in design can severely underestimate the axial forces in chords and collectors when the structures step into the inelastic stage.
Ph. D.

The analysis procedures employed in earthquake engineering can be classified as linear static, linear dynamic, nonlinear static and nonlinear dynamic. Linear procedures are usually referred to as force controlled and require less analysis time and less computational effort. On the other hand, nonlinear procedures are referred to as deformation controlled and they are more reliable in characterizing the seismic performance of buildings. However, there is still a great deal of unknowns for nonlinear procedures, especially in modelling the reinforced concrete structures. Turkey ranks high among all countries that have suffered losses of life and property due to earthquakes over many centuries. These casualties indicate that, most regions of the country are under seismic risk of strong ground motion. In addition to this phenomenon, recent studies have demonstrated that near fault ground motions are more destructive than far-fault ones on structures and these effects can not be captured effectively by recent nonlinear static procedures. The main objective of this study is developing a simple nonlinear dynamic analysis procedure which is named as &ldquo
Dynamic Pull Analysis&rdquo
for estimating the seismic response of multi degree of freedom (MDOF) systems. The method is tested on a six-story reinforced concrete frame and a twelve-story reinforced concrete frame that are designed according to the regulations of TS-500 (2000) and TEC (1997).

Nonlinear static analysis is an efficient tool for performance assessment of masonry structures. In particular, it facilitates the accurate prediction of seismic response of a structure to earthquakes. Numerical models based on Equivalent Frame Method allow to predict realistic failure modes observed after preceding seismic events with reasonable computational effort, a characteristic which is suitable for engineering practice. This thesis deals with nonlinear incremental static (pushover) analysis of masonry buildings and the subsequent discussion of the obtained results. TreMuri software is used for developing the numerical models, which are then analysed on the basis of elastic acceleration response spectra obtained according to the Nepal National Building Code. Different structural improvement techniques are implemented in the models and compared in order to determine their impact on seismic performance. Elastic stiffness obtained with the nonlinear analysis is examined in contrast to analytical estimation of the same, made with various mathematical models.

The analysis of stiffened plate structures subject to complex loads such as air-blast pressure waves from external or internal explosions, water waves, collisions or simply large static loads is still considered a difficult task. The associated response is highly nonlinear and although it can be solved with currently available commercial finite element programs, the modelling requires many elements with a huge amount of input data and very expensive computer runs. Hence this type of analysis is impractical at the preliminary design stage. The present work is aimed at improving this situation by introducing a new philosophy. That is, a new formulation is developed which is capable of representing the overall response of the complete structure with reasonable accuracy but with a sacrifice in local detailed accuracy. The resulting modelling is relatively simple thereby requiring much reduced data input and run times. It now becomes feasible to carry out design oriented response analyses. Based on the above philosophy, new plate and stiffener beam finite elements are developed for the nonlinear static and dynamic analysis of stiffened plate structures. The elements are specially designed to contain all the basic modes of deformation response which occur in stiffened plates and are called super finite elements since only one plate element per bay or one beam element per span is needed to achieve engineering design level accuracy at minimum cost. Rectangular plate elements are used so that orthogonally stiffened plates can be modelled. The von Karman large deflection theory is used to model the nonlinear geometric behaviour. Material nonlinearities are modelled by von Mises yield criterion and associated flow rule using a bi-linear stress-strain law. The finite element equations are derived using the virtual work principle and the matrix quantities are evaluated by Gauss quadrature. Temporal integration is carried out using the Newmark-β method with Newton-Raphson iteration for the nonlinear equations at each time step. A computer code has been written to implement the theory and this has been applied to the static, vibration and transient analysis of unstiffened plates, beams and plates stiffened in one or two orthogonal directions. Good approximations have been obtained for both linear and nonlinear problems with only one element representations for each plate bay or beam span with significant savings in computing time and costs. The displacement and stress responses obtained from the present analysis compare well with experimental, analytical or other numerical results.
Applied Science, Faculty of
Civil Engineering, Department of
Graduate

This thesis introduces a versatile finite element package, which is tailored for the static and dynamic analysis of radial tyres. A new axisymmetric solid-of-revolution element which takes into consideration, large deformation, the influence of composite orthotropic material and the viscoelasticity and the nonlinearity of the material properties, has been developed for a general loaded tyre. The finite element package has been verified by comparing its results with available analytical, numerical and experimental results. A full static and dynamic investigation has been carried out for a commercial tyre 175 HR 14 and results obtained by using the package have been compared with available experimental results developed by DUNLOP or carried out at Cranfieid. The package has proved to be reliable, flexible, efficient, economic and accurate. The numerical instability problems which are prevalent in this type of analysis have been overcome by the derivation of a developed Newton-Raphson iterative scheme.

This study presents a new straight pipe element that enables the efficient computation of large, three-dimensional deformations in pipes with circular cross-sections. Existing pipe elements have difficulties in applications including three-dimensional large deformations. To overcome these diffculties, the new element (called RC pipe element in this work), which supports rigid-body and constant-strain modes, is modeled using curvilinear shell coordinates and sinusoidal interpolation functions. This new element captures all stresses except the normal stress across the shell thickness (i.e. small thickness is assumed). Euler parameters are used to describe rotational rigid-body modes and are incorporated into the element's vector of degrees of freedom. Under general loading (axial, transverse, bending and torsion), the element allows large ovalization of its cross section and large, three-dimensional angular changes in the orientation of its reference axis. The formulation used to derive the element incorporates the nonlinear coupling between torsional and bending deformations. Results of the static analysis are presented for the stresses and deformations produced by combined bending and torsional loads. A comparison of these results to corresponding quantities generated by ABAQUS using a large number of 24 degree-of-freedom shell elements indicates excellent agreement and significant gains in computational efficiency because of a reduction in number of degrees of freedom. Results are also presented for the behaviour of the element in the presence of large rotational motion with internal pressure.

Nonlinear response history analysis is accepted as the most accurate analytical tool for seismic response determination. However, accurate estimation of displacement responses using conceptually simple, approximate analysis procedures is preferable, since there are shortcomings in the application of nonlinear response history analysis resulting from its complexity. An equivalent linearization procedure, which utilizes the familiar response spectrum analysis as the analysis tool and benefits from the capacity principles, is developed in this thesis study as an approximate method for predicting the inelastic seismic displacement response of MDOF systems under earthquake excitations. The procedure mainly consists of the construction of an equivalent linear system by reducing the stiffness of structural members which are expected to respond in the inelastic range. Different from similar studies in literature, equivalent damping is not explicitly employed in this study. Instead, predetermined spectral displacement demands are utilized in each mode of the equivalent linear system for the determination of global displacement demands. Response predictions of the equivalent linearization procedure are comparatively evaluated by using the benchmark nonlinear response history analysis results and other approximate methods including conventional pushover analysis and modal pushover analysis (MPA). It is observed that the proposed procedure results in similar accuracy with approximate methods which employ nonlinear analysis. Considering the conceptual simplicity of the procedure and the conventional analysis tools used in its application, presented equivalent linearization procedure can be suggested as a practically applicable method for the prediction of inelastic seismic displacement response parameters with sufficient accuracy.

Existing design provisions in design standards and conventional analysis methods for structural steel members are based on the simplifying kinematic Vlasov assumption that neglects cross-sectional distortional effects. While the non-distortional assumption can lead to reasonable predictions of beam static response and buckling strength in common situations, past work has shown the inadequacy of such assumption in a number of situations where it may lead to over-predicting the strength of the members. The present study thus develops a series of generalized theories/solutions for the static analysis and buckling analysis of steel members with wide flange cross-sections that capture distortional effects of the web. Rather than adopting the classical Vlasov assumption that postulates the cross-section to move and rotate in its own plane as a rigid disk, the present theories assume the web to be flexible in the plane of the cross-section and thus able to bend laterally, while both flanges to move as rigid plates within the plane of the cross-section to be treated as Euler-Bernouilli beams. The theories capture shear deformation effects in the web, as well as local and global warping effects. Based on the principle of minimum potential energy, a distortional theory is developed for the static analysis of wide flange steel beams with mono-symmetric cross-sections. The theory leads to two systems of differential equations of equilibrium. The first system consists of three coupled equilibrium differential equations that characterize the longitudinal-transverse response of the beam and the second system involves four coupled equilibrium differential equations of equilibrium and characterizes the lateral-torsional response of the beam. Closed form solutions are developed for both systems for general loading. Based on the kinematics of the new theory, two distortional finite elements are then developed. In the first element, linear and cubic Hermitian polynomials are employed to interpolate displacement fields while in the second element, the closed-form solutions developed are adopted to formulate special shape functions. For longitudinal-transverse response the elements consist of two nodes with four degree of freedom per node for longitudinal-transverse response and for lateral-torsional response, the elements consist of two nodes with eight degrees of freedom per node. The solution is able to predict the distortional deformation and stresses in a manner similar to shell solutions while keeping the modeling and computational effort to a minimum. Applications of the new beam theory include (1) providing new insights on the response of steel beams under torsion whereby the top and bottom flanges may exhibit different angles of twist, (2) capturing the response of steel beams with a single restrained flange as may be the case when a concrete slab provides lateral and/or torsional restraint to the top flange of a steel beam, and (3) modelling the beneficial effect of transverse stiffeners in reducing distortional effects in the web. The second part of the study develops a unified lateral torsional buckling finite element formulation for the analysis of beams with wide flange doubly symmetric cross-sections. The solution captures several non-conventional features. These include the softening effect due to web distortion, the stiffening effect induced by pre-buckling deformations, the pre-buckling nonlinear interaction between strong axis moments and axial forces, the contribution of pre-buckling shear deformation effects within the plane of the web, the destabilizing effects due to transverse loads being offset from the shear centre, and the presence of transverse stiffeners on web distortion. Within the framework of the present theory, it is possible to evoke or suppress any combination of the features and thus isolate the individual contribution of each effect or quantify the combined contributions of multiple effects on the member lateral torsional capacity. The new solution is then applied to investigate the influence of the ratios of beam span-to-depth, flange width-to-thickness, web height-to-thickness, and flange width-to-web height on the lateral torsional buckling strength of simply supported beams and cantilevers. Comparisons with conventional lateral torsional buckling solutions that omit distortional and pre-buckling effects quantify the influence of distortional and/or pre-buckling deformation effects. The theory is also used to investigate the influence of P-delta effects of beam-columns subjected to transverse and axial forces on their lateral torsional buckling resistance. The theory is used to investigate the load height effect relative to the shear centre. Comparisons are made with load height effects as predicted by non-distortional buckling theories. The solution is adopted to quantify the beneficial effect of transverse stiffeners in controlling/suppressing web distortion in beams and increasing their buckling resistance.

In this thesis, a new concept of finite strip elements is introduced. Lagrangian, Hermitian and spline-type interpolations have been used independently along the two axes of the plate mid-plane. Different plate-bending theories; Mindlin, Reissner and Kirchhoff theories have been applied in the derivations of the new finitestrip elements, for isotropic and composite materials. The new elements have also been extended to work as faceted shell elements for the analysis of cylindrical shells, folded plates and stiffened plates. An efficient modular programming package based on those elements was designed, and it is capable of performing linear and non-linear stress analysis, buckling analysis and natural frequency analysis. The modular package, which was coded in FORTRAN has different solvers and a built-in mesh generator for different types of plate structures. A number of case studies have been employed for the validation of the package and testing its different capabilities. The package has proved to be an efficient tool for numerical modelling of plates, cylindrical shells, folded plates and stiffened plates made of isotropic and composite layered materials.

Dans le cadre de la protection du bâti face au risque sismique, les techniques d’analyse simplifiées, basées sur des calculs quasi-statiques en poussée progressive, se sont fortement développées au cours des deux dernières décennies. Le travail de thèse a pour objectif d’optimiser une stratégie d’analyse simplifiée proposée par Chopra et al. (2001) et adoptée par les normes américaines FEMA 273. Il s’agit d’une analyse modale non linéaire découplée, dénommée par les auteurs UMRHA qui se caractérisent principalement par : des calculs de type pushover selon les modes de vibration dominants de la structure, la création de modèles à un degré de liberté non linéaire à partir des courbes de pushover, puis le calcul de la réponse temporelle de la structure en recombinant les réponses temporelles associées à chaque mode de vibration. Dans ce travail, la méthode UMRHA a été améliorée en investiguant les points suivants. Tout d’abord, plusieurs modèles à un degré de liberté non linéaire déduits des courbes de pushover modal sont proposés afin d’enrichir la méthode UMRHA originelle qui emploie un simple modèle élasto-plastique : autres modèles élasto-plastiques avec des courbes enveloppes différentes, le modèle de Takeda prenant en compte un comportement hystérétique propre aux structures sous séismes, et enfin, un modèle simplifié basé sur la dégradation de fréquence en fonction d’un indicateur de dommage. Ce dernier modèle à un degré de liberté privilégie la vision de la chute de fréquence au cours du processus d’endommagement de la structure par rapport à une description réaliste des boucles d’hystérésis. La réponse totale de la structure est obtenue en sommant les contributions non linéaires des modes dominants aux contributions linéaires des modes non dominants. Enfin, la dégradation des déformées modales, due à l’endommagement subi par la structure au cours de la sollicitation sismique, est prise en compte dans la méthode M-UMRHA proposée dans ce travail, en généralisant le concept précédent de dégradation des fréquences modales en fonction d’un indicateur de dommage : la déformée modale devient elle-aussi dépendante d’un indicateur de dommage, le déplacement maximum en tête de l’ouvrage ; l’évolution de la déformée modale en fonction de cet indicateur est directement identifiée à partir des calculs de pushover modal. La pertinence de la nouvelle méthode M-UMRHA est investiguée pour plusieurs types de structures, en adoptant des modélisations éprouvées dans le cadre de la simulation des structures sous séismes : portique en béton armé modélisé par des éléments multifibres pour le béton et les armatures, remplissage en maçonnerie avec des éléments barres diagonales résistant uniquement en compression, bâti existant contreventé (Hôtel de Ville de Grenoble) avec des approches coques multicouches. Les résultats obtenus par la méthode simplifiée proposée sont comparés aux résultats de référence issus de l'analyse temporelle non linéaire dynamique
In the context of building’s protection against seismic risk, simplified analysis techniques, based on quasi-static analysis of pushover, have strongly developed over the past two decades. The thesis aims to optimize a simplified method proposed by Chopra and Goel in 2001 and adopted by American standards FEMA 273. This method is a nonlinear decoupled modal analysis, called by the authors UMRHA (Uncoupled Modal for Response History Analysis) which is mainly characterized by: pushover modal analysis according to the dominant modes of vibration of the structure, setting up nonlinear single degree of freedom systems drawn from modal pushover curves, then determining the history response of the structure by combining of the temporal responses associated with each mode of vibration. The decoupling of nonlinear history responses associated with each mode is the strong assumption of the method UMRHA. In this study, the UMRHA method has been improved by investigating the following points. First of all, several nonlinear single degree of freedom systems drawn from modal pushover curves are proposed to enrich the original UMRHA method, in which a simple elastic-plastic model is used, other elastic-plastic models with different envelope curves, Takeda model taking into account an hysteretic behavior characteristic of structures under earthquakes, and finally, a simplified model based on the frequency degradation as a function of a damage index. The latter nonlinear single degree of freedom model privileges the view of the frequency degradation during the structure damage process relative to a realistic description of hysteresis loops. The total response of the structure is obtained by summing the contributions of the non linear dominant modes to those of linear non dominant modes. Finally, the degradation of the modal shapes due to the structure damage during the seismic loading is taken into account in the new simplified method M-UMRHA (Modified UMRHA) proposed in this study. By generalizing the previous model of frequency degradation as a function of a damage index: the modal shape becomes itself also dependent on a damage index, the maximum displacement at the top of the structure; the evolution of the modal shape as a function of this index is directly obtained from the modal pushover analysis. The pertinence of the new method M-UMRHA is investigated for several types of structures, by adopting tested models of structures simulation under earthquakes: reinforced concrete frame modeled by multifibre elements with uniaxial laws under cyclic loading for concrete and steel, infill masonry wall with diagonal bars elements resistant only in compression, existing building (Grenoble City Hall) with multilayer shell elements and nonlinear biaxial laws based on the concept of smeared and fixed cracks. The obtained results by the proposed simplified method are compared to the reference results derived from the nonlinear response history analysis

Although performance based assessment procedures are mainly developed for reinforced concrete and steel buildings, URM buildings occupy significant portion of building stock in earthquake prone areas of the world as well as in Turkey. Variability of material properties, non-engineered nature of the construction and difficulties in structural analysis of perforated walls make analysis of URM buildings challenging. Despite sophisticated finite element models satisfy the modeling requirements, extensive experimental data for definition of material behavior and high computational resources are needed. Recently, nonlinear equivalent frame models which are developed assigning lumped plastic hinges to isotropic and homogenous equivalent frame elements are used for nonlinear modeling of URM buildings. The work presented in this thesis is about performance assessment of unreinforced brick masonry buildings in Turkey through nonlinear equivalent frame modeling technique. Reliability of the proposed model is tested with a reversed cyclic experiment conducted on a full scale, two-story URM building at the University of Pavia and a dynamic shake table test on a half scale, two story URM building at the Ismes Laboratory at Bergamo. Good agreement between numerical and experimental results is found. Finally, pushover and nonlinear time history analyses of three unreinforced brick masonry buildings which are damaged in 1995 earthquake of Dinar is conducted using the proposed three dimensional nonlinear equivalent model. After displacement demands of the buildings are determined utilizing Turkish Earthquake Code 2007, performance based assessment of the buildings are done.

The seismic assessment of existing structures is considered the fundamental step to (i) estimate the seismic capacity of the initial structure (ii) predict the collapse mechanism and the structural weakness, (iii) select the most appropriate seismic retrofitting technique and determine the improved capacity of the upgraded building. Nonlinear dynamic analysis is widely recognised as the most accurate tool to predict the seismic behaviour of structures. However, this type of analysis has a high computational cost, and it is not an approach that can be extensively applied for professional purposes yet. To provide a tool that predicts the seismic behaviour of structures with a good accuracy but with a lower computational burden, nonlinear static methods of analysis were developed. The Capacity Spectrum Method (CSM) proposed by Freeman and the N2 Method proposed by Fajfar were pioneering methods and were recommended by the American and the European seismic code, respectively. Although these methods of analysis are generally reliable for the assessment of plane frames, however they neglect the contribution of higher modes of vibration to the seismic response and do not consider the progressive reduction of the structural stiffness due to the nonlinear behaviour of the structure. To improve the level of accuracy, advanced nonlinear static methods of analysis were developed, such as the Multimodal Pushover Analysis by Chopra et al., the Displacement Adaptive Puhover by Pinho et al. and the Advanced N1 method by Ghersi et al. Despite the innovative character of these methods, however they still present shortcomings. Another important aspect regarding existing structures is the presence of infill panels. Although infill panels provide the structure with a much larger stiffness and their location and mechanical properties influence the dissipative mechanism of the structure, however they are considered nonstructural elements, and their contribution to the seismic response is neglected. This thesis aims at the development of a nonlinear static method of analysis that can accurately estimate the seismic response of RC frames, with and without infill panels, keeping acceptable computation costs. To this end, the thesis proposes a multimodal adaptive procedure named overDamped Displacement Adaptive Procedure (D-DAP). This method has been developed from the combination of the approaches proposed by Pinho et al. and by Ghersi et al. The multimodal adaptive procedure to update the load vector is taken from the first, while the method for the association of the peak ground acceleration to the displacement demand without the SDOF approximation is drawn from the second. In addition, the D-DAP is equipped with an equivalent damping to consider the increase of the energy dissipation due the cumulated damage in the structure. To this end, the value of the equivalent damping is updated at each step according to a new damping law that has been properly calibrated in this work for RC frames with and without infill panels. The accuracy of the D-DAP in the seismic assessment of rc frames was compared to that of the DAP by Pinho, the MPA by Chopra, the N2 method (EC8) and the CSM (FEMA 440). To this end, a set of 54 RC frames was designed to be representative of existing buildings with various levels of seismic deficiencies, and their seismic responses were predicted by those aforementioned methods of analysis. These comparisons showed that the D-DAP applied with the proposed damping law demonstrated an accuracy in predicting the seismic response of RC frames, with and without infills, generally higher than the other nonlinear static methods of analysis. In particular, the D-DAP provided a significant improvement with respect to the other existing methods in the prediction of the response of RC frames with infill panels.

In this investigation, the elasto-plastic behavior and the seismic performance of concrete reinforced frame structures reinforced are evaluated by applying the Pushover method. This evaluation is done on several cases: with high ductility steel (Grade 40), conventional steel (Grade 60) and high strength steel (Grade 75). For the previous, the capacity curve graph obtained from the displacement coefficient method was used to measure the capacity of the structure. In addition, the performance of the structure for different levels of seismic design are evaluated with the resulting values of ductility and rigidity of each case. The results showed that reinforcing a structure with a Grade 40 reinforcing steel increases the energy dissipation capacity, and if reinforced with a Grade 75 reinforcing steel increases the strength capacity in the structure. Finally, the comparative result of the various cases are presented to demonstrate the influence of reinforcing steel on the plastic behavior of concrete reinforced frame structures.

At the design stage, column-beam connections of steel structures are assumed as fully rigid or as hinges, and the design is completed with these assumptions. On the other hand, in practice, steel column-beam connections show neither fully rigid nor fully hinge behaviour, and the characteristic behaviour of the connections lies between these two special cases. Performing realistic calculation of these forces and knowing the behaviour of structures close to reality will decrease life and goods losses to the minimum level in a probable of earthquake to be encountered in the future.  
In this study, seismic performance of 2-D steel frames were evaluated by Capacity Spectrum Method proposed in the ATC 40 document published in 1996. A new computer program was developed in order to define all geometric and loading data and to perform nonlinear analysis of rigid and semi rigid steel frames for which the performances will be evaluated. In case studies, 3-Floor Steel Frames that have different bay numbers were investigated in various forms according to the rigid and different semi rigid connection types. In addition, the performances these frames for various seismic regions and soil conditions were compared. According to the results, it was observed that semi rigidly connected frames are under the effect of smaller ground acceleration have greater displacement values. As a consequence of this ductile and energy dissipative response, it was seen that the stresses in the members of frame become considerably small, relative to the stresses in the rigid frames&rsquo
. Furthermore, the performances of semi-rigid frames can be affected negatively beyond such a low rigidity. Consequently, the most convenient design should be made according to the seismic and soil region where the structure to be constructed by performing the necessary studies on the connection details in order to achieve desired performance, serviceability and optimum member criteria.

The present work describes the finite element (FE) modeling and dynamic response of lightweight, deployable shelters (tent) to large external blast loads. Flexible shelters have been used as temporary storage places for housing equipments, vehicles etc. TEMPER Tents, Small Shelter System have been widely used by Air Force and Army, for various field applications. These shelters have pressurized Collective Protection System (CPS), liner, fitted to the frame structure, which can provide protection against explosives and other harmful agents. Presently, these shelter systems are being tested for the force protection standards against the explosions like air-blast. In the field tests carried out by Air Force Research Laboratory, it was revealed that the liner fitted inside the tent was damaged due to the air blast explosion at some distant from the structure, with major damage being on the back side of the tent. The damage comprised of tearing of liner and separation of zip seals. To investigate the failure, a computational approach, due to its simplicity and ability to solve the complex problems, is used. The response of any structural form to dynamic loading condition is very difficult to predict due to its dependence on multiple factors like the duration of the loading, peak load, shape of the pulse, the impulse energy, boundary conditions and material properties etc. And dynamic analysis of shell structures pose even much greater challenge. Obtaining solution analytically presents a very difficult preposition when nonlinearity is considered. Therefore, the numerical approach is sought which provide simplicity and comparable accuracy. A 3D finite element model has been developed, consisting of fabric skin supported over the frames based on two approaches. ANSYS has been used for obtaining the dynamic response of shelter against the blast loads. In the first approach, the shell is considered as a membrane away from its boundaries, in which the stress couple is neglected in its interior region. In the second approach, stress coupling is neglected over the whole region. Three models were developed using Shell 63, Shell 181 and Shell 41. Shell 63 element supports both the membrane only and membrane-bending combined options and include stress stiffening and large deflection capabilities. Shell 181 include all these options as Shell 63 does and also, accounts for the follower loads. Shell 41 is a membrane element and does not include any bending stiffness. This element also include stress stiffening and large deflection capabilities. A nonlinear static analysis is performed for a simple plate model using the elements, Shell 41 and Shell 63. The membrane dominated behavior is observed for the shell model as the pressure load is increased. It is also observed that the higher value of Young's modulus (E) increases the stresses significantly. Transient analysis is a method of determining the structural response due to time dependent loading conditions. The full method has been used for performing the nonlinear transient analysis. Its more expensive in terms of computation involved but it takes into account all types of nonlinearities such as plasticity, large deflection and large strain etc. Implicit approach has been used where Newmark method along with the Newton-Raphson method has been used for the nonlinear analysis. Dynamic response comprising of displacement-time history and dynamic stresses has been obtained. From the displacement response, it is observed that the first movement of the back wall is out of the tent in contrast to the other sides whose first movement is into the tent. Dynamic stresses showed fluctuations in the region when the blast is acting on the structure and in the initial free vibration zone. A parametric study is performed to provide insight into the design criteria. It is observed that the mass could be an effective means of reducing the peak responses. As the value of the Young's Modulus (E) is increased, the peak displacements are reduced resulting from the increase in stiffness. The increased stiffness lead to reduced transmitted peak pressure and reduced value of maximum strain. But a disproportionate increase lead to higher stresses which could result in failure. Therefore, a high modulus value should be avoided.
Master of Science

In the classical continuum theory of solid mechanics, the mathematical framework involves partial derivatives to represent the state of deformation of a solid body. A significant drawback due to derivatives is related to the unphysical results given near the discontinuities, because they are undefined wherever a continuous field of displacements is not verified, such as in the presence of dislocations, voids, cracks, interfaces between different phases within the same body and grain boundaries. Various techniques were employed for overcoming this incapability of the classical theory in describing material behavior in such conditions; in fact, spontaneous formation and growth of discontinuities are of great importance in solid mechanics: they lead to fractures and failures of systems that must be avoided, especially in aerospace structures, primarily, for safety reasons and, secondly, for economic purposes. One of these new approaches concerns employing nonlocal theories, based on integral formulations (more precisely integro-differential formulations), defined even when non-derivable displacement fields are involved. Peridynamics is one of these theories: it was suggested by Stewart Silling in 2000 [1] in order to adopt a consistent formulation describing material behavior not only when a continuous displacement field is provided, but also whenever discontinuities are present, avoiding partial differential equations or pre-setting of conditions which can influence the results. There are two versions of peridynamic models: bond-based, which was introduced first (see [1, 2]) and state-based. In the bond-based version, forces between two material points depend solely on their relative displacement, their relative initial position, and material properties. Due to its simplicity compared to the state-based version, most of the peridynamic applications have employed bond-based Peridynamics. However, bond-based models result in several limitations (the same of other atomistic or molecular dynamics models [3], although this is a continuum theory, not a discrete one), the most important of these is the fixed value of Poisson’s ratio: 1/4 in 3D or 2D plane strain, and 1/3 in 2D plane stress (see e.g. [1, 4]). This peculiarity implies other restrictions, such as the impossibility of reproducing plastic incompressibility in an accurate way. Nevertheless, for many purposes, bond-based Peridynamics fits the requirements and gives satisfying results. State-based peridynamic models remove these restrictions by allowing the interaction (“bond”) between a pair of points to potentially depend on all other bonds connected to the two points. Moreover, there are two types of state-based peridynamic formulations: ordi- nary and non-ordinary [2, 5, 6]. In the former, the forces between two material points act along the vector connecting the points in the deformed configuration. In the latter, such characteristic is not present. The ordinary state-based formulation requires specific derivation of constitutive models, see examples of viscoelasticity and plasticity models in [7, 8]. For non-ordinary state-based formulation, two approaches have been proposed: the development of an explicit model for the peridynamic force state [2] and the development of a map thanks to which classical mechanics constitutive relations are incorporated to indirectly establish the relationship between the interaction force and the deformation. The latter approach is called correspondence model [2]. The purpose of this thesis has been the investigation of possible advantages and drawbacks of this new and unexplored theory, so to identify some guidelines for choosing parameters fundamental for the analyses and the development of models for particular structural analyses. In the first year of the PhD course, the state of the art of this theory was studied and the bond-based linear and nonlinear static solvers developed in Matlabr were analyzed, employed and improved. During the second year of PhD course, the author of this thesis has focused her attention on the second version of the theory, based on concepts of advanced mathematics. She has become familiar with it, thanks to the functional analysis course that she had attended in the first year. One of the main original contributions of the present work to the existing literature is the development of the 2D linearization of the state-based “linear peridynamic solid” model in the state-based formulation. These models are useful whenever simplifying assumptions of plane stress and plane strain can be adopted for the simulation of a system, which, otherwise, would be described by a 3D model requiring high computational resources (time and memory). Particular attention is paid to this aspect, because, being a nonlocal model, implementing a peridynamic code is, in general, more computationally expensive than a code based on a local approach. The study of the state-based version started before going abroad and the development of the 2D models was completed during the six month stay at the University of Nebraska-Lincoln in USA. Both static and dynamic codes have been developed and the relevant parameters of these models have been analyzed. These linearized models are described in chapter 1.2.2. The study of failure criteria in state-based Peridynamics and the improvement of the algorithms in Matlabr to accelerate the codes and to optimize memory resources have been the main issues of the third year research. Some failure criteria, presented in section 1.2.3, have been proposed for brittle homogeneous linear elastic materials. They are criteria based on the maximum admissible stretch: a given bond fails at a critical stretch obtained by the work required to break that bond and this work is related to the fracture energy of the material. The results are compared to experimental data both for static and for dynamic cases, in bondbased and in state-based formulations. The detailed description of the algorithms can be found in chapter 3, while the results are illustrated in chapters 4 and 5.
Nella teoria classica della meccanica dei solidi, la formulazione matematica include derivate parziali, grazie alle quali si possono rappresentare stati di deformazione come funzioni degli spostamenti relativi dei nodi in cui è discretizzato il sistema continuo. Una carenza rilevante dovuto all’utilizzo delle derivate è legato ai risultati privi di significato fisico ottenuti in prossimità delle discontinuità perché le derivate non sono definite laddove manca un campo di spostamenti continuo, come può capitare in presenza di dislocazioni, vuoti, cricche, interfacce tra fasi differenti nello stesso corpo e bordi dei grani. Dato che la formazione spontanea e la crescita di discontinuità sono di grande importanza in meccanica dei solidi, diverse tecniche sono state utilizzate per superare questa incapacità della teoria di descrivere il comportamento dei materiali in tali condizioni, perché situazioni in cui le strutture sono incapaci di continuare a svolgere la propria funzione devono essere evitate, specialmente per strutture aerospaziali, in primo luogo, per ragioni di sicurezza ed, in secondo luogo, per motivi economici. Uno di questi nuovi approcci riguarda l’utilizzo di teorie non locali basate su formulazioni integrali (più precisamente formulazioni integro-differenziali), definite anche quando campi di spostamento non derivabili sono presenti. La teoria “Peridynamics” è una di queste teorie: è stata proposta da Stewart Silling nel 2000 [1] così da adottare una formulazione unica e coerente capace di descrivere i comportamenti dei materiali in corpi sia continui che discontinui, evitando l’uso di equazioni alle derivate parziali o la definizione a priori di alcune condizioni che possono influenzare (e in un certo senso favorire) dei risultati. Ci sono due versioni di modelli peridinamici: la state-based, e un suo caso particolare, la bond-based, che è stata introdotta per prima (vedi [1, 2]). Nella versione bond-based, le forze tra due punti materiali dependono unicamente dal loro spostamento relativo e dalla loro posizione relativa iniziale, oltre che dalle proprietà del materiale. Vista la sua semplicità a confronto con la seconda versione, la maggior parte delle applicazioni e degli articoli sulla Peridynamica ha adottato la formulazione bond-based. Tuttavia, i modelli nella formulazione bond-based sono caratterizzati da alcune limitazioni (le stesse dei modelli di altre teorie atomistiche e dei modelli di dinamica molecolare [3], anche se la Peridinamica è una teoria del continuo, non discreta), la più notevole di queste è il modulo di Poisson fisso: 1/4 nelle simulazioni 3D oppure in caso di deformazione piana 2D, e 1/3 nelle simulazioni in stato di tensione piana 2D (si veda per esempio [1, 4]). Questa particolarità implica altre restrizioni, come l’impossibilità di riprodurre la condizione di incomprimibilità plastica in maniera accurata. Tuttavia, per la maggior parte degli scopi, la formulazione bond-based è sufficiente e fornisce risultati approssimati soddisfacenti. I modelli della versione state-based rimuovono queste restrizioni, permettendo che le interazioni tra due punti possano dipendere da tutte le interazioni (i “bond”) connessi ad almeno uno dei due punti, tramite delle mappe avanzate chiamate “states”. Inoltre, ci sono due tipi di formulazioni state-based: la ordinary e la non-ordinary [2, 5, 6]. Nella formulazione ordinary, le forze tra due punti materiali agiscono lungo la congiungente i due punti nella configurazione deformata, mentre nella formulazione non-ordinary, questa caratteristica non è più vera. La formulazione ordinary della state-based necessita di modelli costitutivi appositamente derivati, come per esempio i modelli di viscoelasticità e platicità in [7, 8]. Per la formulazione non-ordinary della state-based, due approcci sono stati proposti: lo sviluppo di un modello esplicito per l’espressione dello state della forza peridinamica [2] e lo sviluppo di una mappa grazie alla quale le relazioni costitutive della meccanica classica sono incorporate per stabilire indirettamente la relazione tra la forza d’interazione e la deformazione. I modelli derivanti dal secondo approccio sono chiamati modelli correspondence [2]. L’argomento di questa tesi è lo sviluppo di modelli per particolari tipi di analisi e la ricerca di possibili vantaggi e inconvenienti di questa teoria nuova ed inesplorata, così da identificare alcune linee guida per la scelta di parametri fondamentali per le analisi. Durante il primo anno del corso di dottorato, lo stato dell’arte relativo a questa teoria è stato studiato e i solutori statici lineari e non lineari nella formulazione bond-based sviluppati precedentemente in ambiente Matlabr sono stati analizzati, usati e migliorati. Durante il secondo anno, l’autrice di questa tesi si è concentrata sulla seconda versione, basata su concetti di matematica avanzata con cui ha preso dimestichezza grazie al corso di analisi funzionale seguito il primo anno. Uno dei principali contributi originali alla letteratura esistente presenti in questa tesi è lo sviluppo dei modelli linearizzati 2D del modello solido lineare nella formulazione state-based. Questi modelli sono particolarmente utili quando semplificazioni di stato piano di tensione o di deformazione possono essere assunte per la simulazione di un sistema tridimensionale, che altrimenti verrebbe descritto da un modello 3D che necessiterebbe di risorse computazionali più elevate (in termini di tempo e memoria). Una particolare attenzione è richiesta per quest’aspetto, perché, essendo un approccio non locale, implementare un codice basato sulla teoria peridinamica richiede in generale più risorse computazionali di un codice basato su un approccio locale. Lo studio della versione state-based è iniziato prima di andare all’estero e lo sviluppo dei modelli 2D si è poi completato durante il soggiorno di sei mesi alla University of Nebraska-Lincoln negli Stati Uniti. Sono stati sviluppati sia un codice dinamico che uno statico. I parametri principali di questi modelli sono stati analizzati e i modelli linearizzati si possono trovare descritti nel capitolo 1.2.2. Lo studio dei criteri di frattura adottabili nella formulazione state-based e il miglioramento degli algoritmi in Matlabr per accelerare i codici e ottimizzare le risorse di memoria e gestione dei dati sono stati gli argomenti principali del terzo anno. Alcuni criteri di frattura, presentati nel capitolo 1.2.3, sono stati proposti per materiali lineari elastici omogenei e caratterizzati da frattura fragile. Sono criteri basati sul massimo allungamento: un’interazione non locale (“bond”) viene meno quando un valore critico di allungamento è raggiunto; questo valore di allungamento critico è calcolato dal lavoro richiesto per rompere il bond e questo lavoro è a sua volta legato all’energia di frattura. I risultati ottenuti sono stati confrontati con dati sperimentali per casi sia statici che dinamici, sia nella formulazione bondbased che in quella state-based. La descrizione dettagliata degli algoritmi si trova nel capitolo 3, mentre i risultati sono riportati nei capitoli 4 e 5.

Lateral load carrying capacities of reinforced concrete structures which are designed by considering only gravity loads or according to outdated earthquake codes can be insufficient. The most important problem for these buildings is the limited ductility of the frame elements. How to evaluate the performance of an existing structure and to what level to strengthen it had been major concerns for structural engineers. Recent earthquakes which occurred in the Marmara Region in the last decade have increased the number of seismic assessment projects drastically. However, there was no special guideline or code dealing with the assessment of existing buildings. In order to have uniformity in assessment projects, a new chapter has been included in the revised Turkish Earthquake Code (2006). In this study, the existing and retrofitted conditions of a reinforced concrete building were assessed comparatively by employing linear and nonlinear assessment procedures according to different seismic rehabilitation codes. The study was carried out on a six storey reinforced concrete telephone exchange building. Although there was no damage in the structure due to the recent earthquakes that occurred in the Marmara Region, the building was assessed and retrofitted in 2001 by using equivalent lateral load analysis results. The results of linear and nonlinear assessment procedures performed in the scope of this thesis, were also compared with the assessment results of this previous study. In the nonlinear assessment procedures, pushover analysis results were used. In addition to comparison of the assessment procedures, efficiency of a widely used approximate pushover method was also investigated.

DETAILED EVALUATION OF AN EXISTING REINFORCED CONCRETE BUILDING DAMAGED UNDER ITS OWN WEIGHT Bayraktar, Atilla M.Sc., Department of Civil Engineering Supervisor: Prof. Dr. Ahmet Yakut May 2011, 130 pages A significant part of the Turkey&rsquo
s building inventory consists of reinforced concrete frame structures. In addition to that a big part of the existing building inventory in Turkey shows insufficiency in seismic performance damage or failure of structures under their own loads has also been observed. The failure of Zü
mrü
t Apartment building that occurred in 2004 in Konya and resulted in the death of 92 people brings the necessity of researches on robustness and reserve capacities of the buildings under gravity loading to front. In the context of this thesis, the event in Konya that has resulted in the crushing of four columns in Dostlar Building Complex is studied. After the occurrence of the event, the building was visited, plans of existing condition were prepared and pre-assessment was performed. Original plans of the building, strength test results of the concrete samples and reinforcement detection results were obtained. The reasons behind the crushing of the columns have been investigated through a series of analyses based on a number of possible hypotheses. After modeling the building in SAP2000 program, demand-capacity ratios are calculated. Nonlinear behavior of the structure is determined by incremental static pushover analysis and the seismic performance of the building is evaluated by nonlinear procedure described in 2007 Turkish Earthquake Code. To determine the nonlinear behavior under gravity loading and collapse mechanism, incremental vertical pushover analysis is performed.

Perú se localiza en una zona de alta sismicidad, debido a que se encuentra encima del área de subducción entre la placa tectónica de Nazca y Sudamericana, perteneciente al cinturón de fuego del Pacífico. Perú es un país en vía de desarrollo, por lo que es de suma importancia estar preparados para auxiliar a los miles de damnificados que pueda haber ante un evento sísmico importante. La evaluación del riesgo sísmico de edificaciones esenciales como colegios y hospitales es necesario para trabajos de reforzamiento estructural en este tipo de infraestructura. En el presente artículo científico, se presenta cuán vulnerables son los colegios públicos del distrito de San Juan de Miraflores en la ciudad de Lima ante un evento sísmico. Para ello, se utilizó la metodología de Inspección Visual Rápida del FEMA P-154. Además, se analizó de forma cuantitativa el pabellón 780 Pre, un módulo educativo estandarizado y construido en los años noventa cuya presencia es frecuente en dicho distrito. Para ello, se realizó un análisis no-lineal estático y no-lineal dinámico. Los resultados de la investigación concluyen que la mayoría de las edificaciones educativas presentan una alta vulnerabilidad sísmica y no cumplen con los requerimientos de uso post-sismo como se exige en la norma sismorresistente; así como también se verificó la deficiencia del módulo 780 Pre frente a un sismo severo cuando este fue sometido a los análisis no-lineales.
Peru is located in a high seismicity zone because it is set above the subduction area between the Nazca and South American tectonic plates, both belonging to the Pacific’s Ring of Fire. Being a developing country, it is of utmost importance to be prepared to help the thousands of victims that may be in the face of a major seismic event. The assessment of the seismic vulnerability of essential buildings —such as schools and hospitals— is necessary for structural reinforcement procedures in this type of infrastructure if needed. In this thesis, it is presented how vulnerable are the public schools of the district of San Juan de Miraflores in the city of Lima to a seismic event. For this, the FEMA P-154 Rapid Visual Screening methodology was used. In addition, the “780 Pre” public school building, a standardized educational building built in the 1990s and whose presence is frequent in that district, was analyzed quantitatively. For this, a static nonlinear and dynamic nonlinear analysis were performed. The results of the investigation show that most of the educational buildings present high seismic vulnerability and do not meet the requirements of post-earthquake use as required by the Peruvian seismic design provisions. Also, the deficiency of the 780 Pre building against a severe earthquake when it was subjected to non-linear analyzes was verified.
Tesis

L'elaborato propone un metodo per la modellazione tridimensionale di interi edifici in muratura, con lo scopo di valutare le performance sismiche, mediante il programma di calcolo SAP2000. La metodologia proposta consente la modellazione di pareti in muratura simulandone il comportamento non lineare sotto azioni agenti nel piano ed allo stesso tempo permette di considerare la ripartizione delle azioni verticali e soprattutto orizzontali che avviene tra le pareti, dovuta alle zone di connessione, ai solai ed alla loro rigidezza a taglio nel piano. Per lo sviluppo del metodo di modellazione è stato utilizzato un edificio molto semplice. Successivamente la metodologia è stata applicata ad un caso più realistico sul quale si sono fatte anche considerazioni riguardo i diversi comportamenti della struttura in funzione della rigidezza dei solai.

This dissertation presents work targeted to study the effects of diaphragm flexibility on the seismic performance of light frame wood structures (LFWS). The finite element approach is considered for modeling LFWS as it is more detailed and provides a way to explicitly incorporate individual structural elements and corresponding material properties. It is also suitable for capturing the detailed response of LFWS components and the structure as a whole. The finite element modeling methodology developed herein is in general based on the work done by the other finite element researchers in this area. However, no submodeling or substructuring of subassemblages is performed and instead a detailed model considering almost every connection in the shear walls and diaphragms is developed. The studs, plates, sills, blockings and joists are modeled using linear isotropic three dimensional frame elements. A linear orthotropic shell element incorporating both membrane and plate behavior is used for the sheathings. The connections are modeled using oriented springs with modified Stewart hysteresis spring stiffnesses. The oriented spring pair has been found to give a more accurate representation of the sheathing to framing connections in shear walls and diaphragms when compared to non-oriented or single springs typically used by most researchers in the past. Fifty six finite element models of LFWS are created using the developed methodology and eighty eight nonlinear response history analyses are performed using the Imperial Valley and Northridge ground motions. These eighty eight analyses encompass the parametric study on the house models with varying aspect ratios, diaphragm flexibility and lateral force resisting system. Torsionally irregular house models showed the largest range of variation in peak base shear of individual shear walls, when corresponding flexible and rigid diaphragm models are compared. It is also found that presence of an interior shear wall helps in reducing peak base shears in the boundary walls of torsionally irregular models. The interior walls presence was also found to reduce the flexibility of diaphragm. A few analyses also showed that the nail connections are the major source of in-plane flexibility compared to sheathings within a diaphragm, irrespective of the aspect ratio of the diaphragm. A major part of the dissertation focuses on the development of a new high performance nonlinear dynamic finite element analysis program which is also used to analyze all the LFWS finite element models presented in this study. The program is named WoodFrameSolver and is written on a mixed language platform Microsoft Visual Studio .NET using object-oriented C++, C and FORTRAN. This tool set is capable of performing basic structural analysis chores like static and dynamic analysis of 3D structures. It has a wide collection of linear, nonlinear and hysteretic elements commonly used in LFWS analysis. The advanced analysis features include static, nonlinear dynamic and incremental dynamic analysis. A unique aspect of the program lies in its capability of capturing elastic displacement participation (sensitivity) of spring, link, frame and solid elements in static analysis. The programâ s performance and accuracy are similar to that of SAP 2000 which is chosen as a benchmark for validating the results. The use of fast and efficient serial and parallel solver libraries obtained from INTEL has reduced the solution time for repetitive dynamic analysis. The utilization of the standard C++ template library for iterations, storage and access has further optimized the analysis process, especially when problems with a large number of degrees of freedom are encountered.
Ph. D.

The presented thesis focuses on static analysis of plastic structures, taking into account nonlinear behaviour of the material depending on the stress. The static analysis is performed using the finite element method. The difference between material linear and material nonlinear approach is illustratively described in the introduction. A shell finite element, which is enhanced by the possibility of further delamination into layers and integration points along its thickness, is suitable to be used for a numerical analysis of a plastic structures. Separate chapters are devoted to the integration of the resulting values over the height of the cross-section. The integration of the material stiffness matrix correctly reflects the emergence of eccentricity. A part of the attention is devoted to the numerical quadrature rules. Next chapter is devoted to material nonlinear models. Two approaches are described: a simpler one, using the isotropic nonlinear elastic model, and more general one, using the orthotropic plastic model. The theoretical description is complemented by the graphic interpretation of the criteria according to the individual authors. A significant portion of this work is devoted to the algorithmization of calculation procedures described in the theoretical chapters. The algorithmization itself is implemented in Fortran language into a dynamic-link library which is part of the software program RFEM 5 which is widely used in engineering practice. A part of the work is a study comparing the performance of the different technologies applicable for the algorithmization of the described issues. The agreement of the theoretical analysis of the material models and subsequent implementation within the RFEM 5 is demonstrated on the example of the bent cantilever. The thermoplastic aboveground tank structure is subject of detailed material linear, and nonlinear analysis respectively. The various approaches are compared on the results of stress, deformation an

In Turkey, most of the existing buildings have been designed according to Turkish Earthquake codes of 1975 and 1997. It is a well known fact that, poor material quality, poor design, poor control on site and inadequate workmanship makes existing buildings vulnerable to earthquake. In addition, change in function of buildings becomes another problem. These problems increase the importance of assessment of existing buildings. For this purpose, a new chapter has been added to the new code and assessment methods of existing buildings is regulated. 2007 Turkish Earthquake Code offered two analysis methods, linear and nonlinear analysis methods. Due to comprehensive computational, modeling and assessment challenges involved in applying the code procedures that are generally not well understood by practicing engineers, the use of commercial package computer programs is preferred. There are widely used three software&rsquo
s in Turkey
Idestatik, Sta4 and Probina. These programs currently handle linear assessment method only. This study aims to compare the assessment results of the most widely used three structural analysis and design softwares in Turkey. For this purpose, four v different structures having different property and plan were employed. These buildings were selected to be representative of the mostly common building types. Each building has been modeled and identified with the same material properties, the same reinforcement details and the same geometric properties in each software. The results of the assessment are compared in order to determine the inconsistencies among the software&rsquo
s and their reliability.

Sabe-se que materiais compostos laminados são, hoje em dia, geralmente usados nas indústrias aeronáutica, aeroespacial, naval e outras, principalmente por causa de suas atrativas propriedades se comparadas aos materiais isotrópicos, como alta rigidez/peso, alta resistência, alto amortecimento e boas propriedades relacionadas ao isolamento térmico e acústico, entre outras. Porém, o comportamento de estruturas feitas de materiais compostos pode ser aperfeiçoado através da utilização de materiais inteligentes. Dentre os diferentes tipos comercialmente disponíveis de materiais inteligentes, os materiais piezelétricos são amplamente usados como sensores e atuadores para o monitoramento e controle de estruturas. O efeito piezelétrico direto define que uma deformação mecânica aplicada ao material é convertida em uma carga elétrica. Por outro lado, o efeito piezelétrico inverso define que um potencial elétrico aplicado ao material é convertido em deformação mecânica. Estes efeitos governam a interação eletromecânica nos materiais piezelétricos. O Método dos Elementos Finitos, uma ferramenta amplamente reconhecida e poderosa para a análise de estruturas complexas, é capaz de realizar a integração dos componentes inteligentes e das partes estruturais clássicas. Sendo assim, o comportamento estático e dinâmico, linear e geometricamente não-linear, de estruturas compostas laminadas delgadas com lâminas piezelétricas incorporadas é analisado neste trabalho usando o Método dos Elementos Finitos (MEF). Elementos triangulares, chamados GPL-T9, com três nós e seis graus de liberdade por nó (três componentes de deslocamento e três de rotação) e um grau de liberdade por camada piezelétrica (potencial elétrico) são usados. Para a análise estática não-linear as equações de equilíbrio são solucionadas usando o Método do Controle de Deslocamentos Generalizados (MCDG) enquanto a solução dinâmica é obtida usando o Método de Newmark com Formulação Lagrangeana Atualizada (FLA). O sistema de equações é resolvido usando o Método dos Gradientes Conjugados (MGC) e nos casos não-lineares um esquema iterativo-incremental é empregado. Diversos exemplos numéricos são apresentados e comparados com resultados obtidos por outros autores com diferentes tipos de elementos e diferentes formulações. A concordância entre estes resultados demonstra a validade e a eficácia dos modelos desenvolvidos.
It is well known that laminate composite materials are nowadays commonly used in the aeronautical, aerospace, naval and other industries mainly because their attractive properties as compared to isotropic materials, such as higher stiffness/weight, higher strength, higher damping and good properties related to thermal or acoustic isolation, among others. However, the behavior of structures made of composite materials can be improved using smart materials. Among several kinds of commercially available smart materials, the piezoelectric materials are widely used as sensors and actuators for the monitoring and control of structures. The direct piezoelectric effect states that a mechanical strain applied to the material is converted to an electric charge. On the other hand, the converse piezoelectric effect states that an electric potential applied to the material is converted to mechanical strain. These effects govern the electromechanical interaction in piezoelectric materials. The finite element method, a widely accepted and powerful tool for analyzing complex structures, is capable of dealing with the integration of smart components and classic structural parts. So, linear and geometrically nonlinear static and dynamic behavior of thin laminate composite structures embedded with piezoelectric layers are analyzed in this work using the Finite Element Method (FEM). Triangular elements, called GPL-T9, with three nodes and six degrees of freedom per node (three displacement and three rotation components) and one degree of freedom per piezoelectric layer (electrical potential) are used. For static analysis the nonlinear equilibrium equations are solved using the Generalized Displacement Control Method (GDCM) while the dynamic solution is performed using the classical Newmark Method with an Updated Lagrangean Formulation (ULF). The system of equations is solved using the Gradient Cojugate Method (GCM) and in nonlinear cases an iterative-incremental scheme is employed. Several numerical examples are presented and compared with results obtained by other authors with different kind of elements and different schemes. The agreement among these results demonstrates the validity and effectiveness of the developed models.

SEISMIC STRENGTHENING OF A MID-RISE REINFORCED CONCRETE FRAME USING CFRPs: AN APPLICATION FROM REAL LIFE Tan, Mustafa Tü
mer M.S., Department Of Civil Engineering Supervisor: Prof. Dr. Gü
ney Ö
zcebe Co-Supervisor: Assoc. Prof. Dr. BariS Binici May 2009, 162 pages FRP retrofitting allows the utilization of brick infill walls as lateral load resisting elements. This practical retrofit scheme is a strong alternative to strengthen low to mid-rise deficient reinforced concrete (RC) structures in Turkey. The advantages of the FRP applications, to name a few, are the speed of construction and elimination of the need for building evacuation during construction. In this retrofit scheme, infill walls are adopted to the existing frame system by using FRP tension ties anchored the boundary frame using FRP dowels. Results of experiments have previously shown that FRP strengthened infill walls can enhance lateral load carrying capacity and reduce damage by limiting interstory drift deformations. In previous, analytical studies, a detailed mathematical model and a simplified version of the model for compression struts and tension ties was proposed and verified by comparing model estimations with test results. In this study, an existing 9-storey deficient RC building located in Antakya was chosen to design and apply a hybrid strengthening scheme with FRPs and reduced number of shear walls. Linear elastic analysis procedure was utilized (force based assessment technique) along with the rules of Mode Superposition Method for the reftrofit design. FRP retrofit scheme was employed using the simplified model and design was conducted such that life safety performance criterion is satisfied employing elastic spectrum with 10% probability of exceedance in 50 years according to the Turkish Earthquake Code 2007. Further analytical studies are performed by using Modal Pushover and Nonlinear Time-History Analyses. At the end of these nonlinear analyses, performance check is performed according to Turkish Earthquake Code 2007, using the strains resulting from the sum of yield and plastic rotations at demand in the critical sections. CFRP retrofitting works started at October 2008 and finished at December 2008 for the building mentioned in this study. Eccentric reinforced concrete shearwall installation is still being undertaken. All construction business is carried out without evacuation of the building occupants. This project is one of the first examples of its kind in Turkey. Keywords: CFRP, Carbon Fiber Reinforced Polymers, Masonry Infill Walls, Reinforced Concrete Infill Walls, Mid-Rise Deficient Structures, Turkish Earthquake Code 2007, Modal Pushover Analysis, Nonlinear Time History Analysis, Linear Elastic Building Assessment

This thesis examines the seismic internal retrofitting of existing deficient reinforced concrete (RC) structures by using structural steel members. Both experimental and numerical studies were performed. The strengthening methods utilized with the scope of this work are chevron braces, internal steel frames (ISFs), X-braces and column with shear plate. For this purpose, thirteen strengthened and two as built reference one bay one story portal frame specimens having 1/3 scales were tested under constant gravity load and increasing cyclic lateral displacement excursions. In addition, two ½
scaled three bay-two story frame specimens strengthened with chevron brace and ISF were tested by employing continuous pseudo dynamic testing methods. The test results indicated that the cyclic performance of the Xbrace and column with shear plate assemblage technique were unsatisfactory. On the other hand, both chevron brace and ISF had acceptable cyclic performance and these two techniques were found to be candidate solutions for seismic retrofitting of deficient RC structures. The numerical simulations by conducting nonlinear static and dynamic analysis were used to estimate performance limits of the RC frame and steel members. Suggested strengthening approaches, chevron brace and ISF, were also employed to an existing five story case study RC building to demonstrate the performance efficiency. Finally, design approaches by using existing strengthening guidelines in Turkish Earthquake Code and ASCE/SEI 41 (2007) documents were suggested.

This thesis presents scaling methods for sizing a prototype micro prismatic revolute (PR) manipulator actuated by permanent magnet (PM) direct current (d.c.) gearmotors. Dimensional analysis was the principle tool used in this investigation, and addressed the problems of scaling a trajectory planner, control law, and gearmotors that exhibit internal nonlinear friction. Similitude methods were used to develop a scaleable two degree-of-freedom trajectory planner from a third order polynomial. Scaling laws were developed from Buckingham's Pi theorem to facilitate the selection process of gearmotors. Nondimensional, nonlinear, differential equations were developed to describe viscous, Coulomb and static friction in comparative PM d.c. motors. From the insights gained through dimensional analysis, a scaleable controller based on the computed torque method was developed and implemented with a cubic trajectory planner. Model and prototype PR manipulator systems were simulated using a hybrid Matlab/Simulink simulation scheme. Experimental systems were constructed with dissimilar model and prototype motors. Control was provided by an AT class PC equipped with 12-bit A/D, D/A cards operating at a sample rate of 100 Hz. The control algorithm was written in Borland 3.1 C for DOS. Results from the experimental testing showed excellent agreement between the test and simulated data and verified the viability of the scaling laws. The techniques presented in this thesis are expected to be applicable to any application that involves scaling PM d.c. micro gearmotors that have significant internal friction terms. These simple, practical tools should be especially beneficial to designers of micro robotic systems.
Master of Science

The diploma thesis is focused on the comparison of the linear and nonlinear analysis of the steel structure and the resulting differences in both the numerical results and the time needed to obtain these results These analyzes are performed on a high-rise building, which has 10 floors and is used as an administrative building. Static model construction and calculations are performed in software system from Dlubal RFEM only loads for individual load cases are calculated manually.

Despite the fact that masonry is one of the oldest and most used building materials, the number of existing studies and experimental data, as well as the applicability of its results (i.e. extrapolation), are substantially lower than those available for much more recent materials, such as concrete or steel. Furthermore, currently in Europe, a large number of residential buildings belong to masonry typologies. These circumstances justify the study of the characteristics and behaviour of the masonry to guide studies on seismic vulnerability. In particular, the Eixample district of Barcelona, in Spain, presents an urban park of functional housing made up 73% of unreinforced masonry structures, solved by means of load-bearing wall systems, without any consideration of seismic action and that, for the most part, exceed 100 years of useful life. These buildings, characteristics of Barcelona, have elements that differentiate them from other buildings of the same construction typology that can be found in other regions of Europe: 1) the number of floors significantly exceeds the average, being able to find buildings with up to 10 or 11 levels; 2) The buildings share dividing walls (e.g. lateral), thereby generating frameworks of buildings known as aggregates; 3) The properties and qualities of the different construction elements are closely linked to the production processes, not yet mechanized, of the time; 4) The level of construction techniques and the qualification of the workforce were very high. In this work, numerical 3D models of isolated structural configurations (i.e. individual building) and in aggregate, of existing buildings have been made, in order to determine and compare the behaviour between the different structural configurations. The buildings have been modelled incorporating the variability of their mechanical parameters and the seismic demand has also been selected taking into account its uncertainty. The structural analysis has been carried out using and comparing different non-linear static calculation procedures and using the incremental non-linear dynamic analysis as a reference. A discussion was carried out comparing the results and the degree of reliability of the different procedures used in relation to the typology of unreinforced masonry buildings. It can be concluded that the simplified methods (i.e. non-linear static) overestimate the damage corresponding to low values of PGA and underestimate the damage for higher values of PGA. Using different criteria, and including the probabilistic consideration of mechanical properties, as well as seismic demand, the foreseeable damage for these structures has been characterized by fragility functions and matrices and damage indices. A study of the correlation between the mechanical parameters and the observed damage is also provided, from which, a high correlation between the obtained results and the variables of interest, is observed, being the Young’s modulus, E, the variable with the highest correlation coefficients. The common difficulties, in any work that involves large samples in relation to the amount of resources and computing time, have been solved through the design of adequate and sufficiently representative samples and by using current computational methods and tools, such as parallel and distributed computing.
A pesar de que la mampostería es uno de los materiales de construcción más antiguos y usados, el número de estudios y datos experimentales existentes, así como la aplicabilidad de sus resultados (i.e. extrapolación), son substancialmente inferiores a aquellos disponibles para materiales mucho más recientes, tales como el hormigón o el acero. Además, actualmente en Europa, un gran número de edificaciones habitacionales pertenecen a tipologías de mampostería. Estas circunstancias justifican el estudio de las características y comportamiento de la mampostería para orientar estudios sobre vulnerabilidad sísmica. En particular, el distrito del Ensanche de Barcelona, en España, presenta un parque urbano de viviendas funcionales compuesto en un 73% por estructuras de mampostería no reforzada, resueltas mediante sistemas de muros de carga, sin ninguna consideración de la acción sísmica y que, en su mayoría, sobrepasan 100 años de vida útil. Estos edificios, característicos de Barcelona, tienen elementos que los diferencian de otras edificaciones de la misma tipología constructiva que pueden encontrarse en otras regiones de Europa: 1) el número de plantas supera significativamente la media, pudiendo encontrar edificios con hasta 10 u 11 niveles; 2) Los edificios comparten paredes medianeras (e.g. laterales), generando con ello entramados de edificios conocidos como agregados; 3) Las propiedades y calidades de los distintos elementos constructivos están estrechamente ligados con los procesos de producción, aún no mecanizados, de la época; 4) El nivel de las técnicas constructivas y la cualificación de la mano de obra eran muy elevados. En este trabajo se han realizado modelos numéricos 3D de configuraciones estructurales aisladas (i.e. edificio individual) y en agregado, de edificios existentes, con la finalidad de determinar y comparar el comportamiento entre las distintas configuraciones estructurales. Los edificios se han modelado incorporando la variabilidad de sus parámetros mecánicos y la demanda sísmica también se ha seleccionado teniendo en cuenta su incertidumbre. El análisis estructural se ha realizado utilizando y comparando diferentes procedimientos de cálculo estático no-lineal y utilizando el análisis dinámico no lineal incremental como referencia. Se ha realizado una discusión comparando los resultados y el grado de confiabilidad de los diferentes procedimientos utilizados en relación con la tipología de edificios de mampostería no reforzada. Se concluye que los métodos simplificados (i.e. estáticos no-lineales) sobrestiman el daño correspondiente a valores bajos de PGA, mientras que lo subestiman para valores elevados de PGA. Utilizando diferentes criterios, e incluyendo la consideración probabilista de las propiedades mecánicas, así como de la demanda sísmica, se ha caracterizado el daño predecible para estas estructuras mediante funciones de fragilidad y matrices e índices de daño y también se aporta un estudio de la correlación entre los parámetros mecánicos y el daño observado, a partir del cual se observa que existe una alta correlación entre los resultados obtenidos y las variables aleatorias seleccionadas, siendo el módulo de Young, E, aquella que presenta los coeficientes de correlación más altos. Las dificultades comunes en cualquier trabajo que involucra muestras de gran tamaño en relación con la cantidad de recursos y tiempos de computación, han sido resueltas mediante el diseño de muestras adecuadas y suficientemente representativas, así como el empleo de métodos y herramientas de cómputo actuales, como lo son el cómputo paralelo y distribuido.
Enginyeria sísmica i dinàmica estructural

El trabajo de investigación se ha denominado “Evaluación del desempeño sísmico de una nave industrial de acero para el sector minero utilizando el ATC-40”, tiene como propósito determinar el comportamiento sísmico de la nave industrial de acero para el sector minero mediante el código ATC-40. La aplicación de análisis estático no lineal como Pushover y Pushover Modal al modelo de cálculo de estructuras existentes ayuda a determinar el grado de daño y el desempeño sísmico. De esta manera, se aplicó satisfactoriamente el análisis estático no lineal al modelo de una estructura existente mediante el uso del software SAP2000, y a través de datos y gráficos proporcionados por el programa, se conoció el nivel de daño para la nave industrial de acero sometida a grandes solicitaciones sísmicas. El desarrollo de esta tesis se divide en siete capítulos: El primer capítulo es de introducción e importancia. La segunda comprende de las generalidades, objetivos generales y específicos del proyecto de tesis; en el tercero se desarrolla el marco teórico para el análisis Pushover; en el cuarto se muestra el análisis estático lineal y no lineal; el quinto comprende el diseño por el método LRFD y su validación; el sexto presenta el criterio de desempeño sísmico usando el código ATC-40; en el séptimo se muestra el análisis de resultados; el octavo muestra las conclusiones y recomendaciones. Del análisis presentado, se concluye que mediante el análisis Pushover se pudo determinar el nivel de desempeño deseado asegurando continuidad para la producción del mineral, de lo cual se puede garantizar que la estructura va tener un comportamiento aceptable ante los 3 niveles de peligro sísmico y no se verá afectada su producción de mineral.
The present research project is entitled "Evaluation of the seismic performance of a mining steel building according to ATC-40" and has the purpose of determining the seismic performance of a mining building defined in the technical report ATC-40. The application of a static nonlinear analysis to the computational model of an existing structure can determine the level of damage and the expected seismic performance. Accordingly, the nonlinear static analysis was successfully applied to the model of an existing structure using SAP2000 software, and through data and graphics provided by the program, the level of damage in the industrial building subjected to great seismic actions was determined. This thesis is divided into seven chapters: the first chapter cover the introduction and the importance of the thesis. The second chapter include the generalities, general objectives and specific objectives of the thesis project; the third reviews the Pushover analysis theoretical framework; the fourth shows the linear and nonlinear static analyses; the fifth includes the design by the LRFD method and its validation; the sixth presents the criteria of seismic performance using the ATC-40 method; the seventh shows the analysis of results; the eighth shows the conclusions and recommendations. From the presented analysis, it is concluded that it was possible to achieve the level of performance desired ensuring continuous ore production, and with this, it can be guaranteed that the structure will have an acceptable behavior for the 3 levels of seismic hazard and that the ore production will not be affected.
Tesis

En esta investigación, se evalúa el comportamiento elasto- plástico y el desempeño sísmico de estructuras aporticadas aplicando el método Pushover. Esta evaluación se hace sobre diversos casos de edificios reforzados con acero de alta ductilidad (Grado 40), acero convencional (Grado 60) y acero de alta resistencia (Grado 75). Para lo anterior, se realiza la evaluación de la capacidad de deformación de los elementos estructurales a partir de las gráficas de momento-rotación de los elementos estructurales más críticos que causa el colapso de la estructura. También, se utilizó la gráfica de curva de capacidad obtenida a partir del método de coeficientes de desplazamiento para medir la capacidad de la estructura. Teniendo en cuenta los valores resultantes de ductilidad y rigidez de cada caso, se evalúa el desempeño de la estructura para diferentes niveles de diseño sísmico. Los resultados mostraron que reforzar una estructura con un acero de Grado 40 aumenta la capacidad de disipación de energía, y si se refuerza con acero de grado 75 aumenta la capacidad de resistencia en la estructura. Finalmente, se presenta el resultado comparativo de los diversos casos para demostrar la influencia del acero de refuerzo en el comportamiento plástico de las estructuras de concreto armado.
In this investigation, the elasto-plastic behavior and the seismic performance of concrete reinforced frame structures are evaluated by applying the Pushover method. This evaluation is done on several cases: with high ductility steel (Grade 40), conventional steel (Grade 60) and high strength steel (Grade 75). For the above, the capacity curve graph obtained from the displacement coefficient method was used to measure the capacity of the structure. In addition, the performance of the structure for different levels of seismic design are evaluated with the resulting values of ductility and rigidity in each case. The results showed that reinforcing a structure with a Grade 40 reinforcing steel increases the energy dissipation capacity, and if reinforced with a Grade 75 reinforcing steel it increases the strength capacity in the structure. Finally, the comparative result of the various cases is presented to demonstrate the influence of reinforcing steel on the plastic behavior of concrete reinforced frame structures.
Tesis

This doctoral thesis focuses on the research of the pedestrian bridges formed by the flat arch. To understand the basic static behaviour of the flat arch it was necessary to make a study of the development of the direct flat arch as footbridge with large span and the impact of stiffness on its camber. For the mathematical modeling FEM software ANSYS were used. The calculation has shown that a design of purely concrete flat arch would demand enormous bending stiffness, which can be achieved only through a massive cross-section. The findings gained in this chapter were further used to design a unique pedestrian bridge formed by the curved in plan flat arch, where to transfer of the large bending moments a steel pipe was designed. Several variants with different span and rise of the arch in plan were tested. From the tested variants was then selected footbridge with a span of 45 m and with the rise of the arch 10 m, which seemed to be the best solution according to the calculations and it was further analyzed in detail. The studied structure is formed by curved concrete slab that is stiffened through the steel brackets on the inner side of a steel tube with a graded thickness. The external cables that are situated in the handrail pipe balance the dead load torsional moment. Designed structure and the static analysis procedure were verified on a fully functional 1:6 scale model. The thesis describes the model analogy used for the design of the model, its structural design and its implementation. Load tests on the model confirmed correctness of the design of the proposed curved in plan pedestrian bridge, its high carrying capacity and the accuracy of the developed procedure of static analysis. Results and experiences acquired from the design and the realization of model are the basis for a practical realization of studied structures. The last part of the thesis deals with the possibility of replacement of the steel components with concrete in pedestrian bridges formed

Ce travail de thèse a pour objet d'analyser le comportement en statique, en fatigue et en vibration linéaire et non linéaire des matériaux sandwichs en présence d'une décohésion de longueur variable. Une étude détaillée est d'abord menée pour caractériser le comportement mécanique en statique et en fatigue de ces matériaux. Les essais ont été conduits en flexion 3-points sur des poutres de ces matériaux pour plusieurs distances entre appuis et pour plusieurs longueurs de fissure. En vibration, une étude expérimentale de la réponse en fréquence à une impulsion, menée à l'aide d'un vibromètre laser a permis de mesurer les fréquences propres et les amortissements de ces matériaux autour de chaque pic de résonance en fonction de la longueur de fissure. Les résultats déduits de l'analyse expérimentale sont comparés à ceux obtenus à partir d'une analyse par éléments finis. Enfin, une méthode de vibration non linéaire a été appliquée pour caractériser le comportement des matériaux sandwichs endommagés par fissuration. Les paramètres non linéaires relatifs au décalage fréquentiel et à l'amortissement sont mesurés en faisant varier l'amplitude d'excitation. Cette étude a permis de montrer que les paramètres non linéaires sont plus sensibles à l'endommagement que les paramètres linéaires.

碩士
中國科技大學
土木與防災應用科技研究所
94
This research is to conduct a damage assessment of a nine story of RC moment- resisting frame with Capacity Spectrum Method (CSM). A bare frame and a frame with RC shear walls are analyzed to highlight the effects of RC shear walls. The nonlinear behaviors of structural members are simulated with the concentrated plastic hinges. The columns are simulated with incorporating the confined effects at the plastic hinge zones at the ends of members to reflect the flexural hinges, where Meander’s formulation is adopted herein. The identical simulation is also implemented to the beam elements, but without taking into account of confined effects at the plastic hinges. RC shear walls are converted into equivalent columns in addition to flexural hinges at the ends of members, and at the mid-length of members specified with a shear hinge account for shear failure modes. The relations of moment-curvature at the plastic hinges are achieved with a fiber element formulation. The methodology in ATC 40 procedure is adopted to perform a nonlinear pushover analysis. Demanding spectra include a seismic design earthquake (PGA=0.24g) and a maximum credible earthquake (PGA=0.32g). Story drift ratios are served as a damage indicator with damage states stipulated in HAZUS99. Even slight in-plane torsion in this building, no significant deficiency appears on either the frames or the frames with shear walls.

The presence of flexible timber diaphragms in many existing unreinforced masonry buildings poses a significant challenge for the assessment of their seismic vulnerability. When diaphragms are flexible, different parts of a structure can interact with each other dynamically, in a way not typically encountered in modern structures with rigid diaphragms. As a result, the seismic analysis methods developed for buildings with rigid diaphragms, as well as our basic understanding of the dynamic behaviours of buildings under earthquake excitations, cannot be applied directly for buildings with flexible diaphragms. This thesis addresses two issues that require immediate attention in improving the seismic analysis of unreinforced masonry buildings with flexible diaphragms, namely (1) to enhance our understanding of the dynamic response characteristics of low-rise buildings with flexible diaphragms, and (2) to investigate the applicability of an array of existing analysis methods developed for rigid diaphragm structures. The research work presented in this thesis begins with a basic analysis of the elastic behaviour of symmetric buildings with flexible diaphragms. Through an analytical study of their modal properties, it is shown that at least two dominant modes are present in the dynamic responses of buildings with flexible diaphragms. Using the results of modal analysis, an improvement to the linear static analysis method is proposed. The inelastic behaviours of symmetric- and asymmetric-plan building systems with flexible diaphragms are then investigated through a systematic parametric analysis. It is shown that the effect of diaphragm flexibility varies depending on the level of stiffness- and strength-eccentricity of the system. A general diaphragm classification is developed to explain the influence of diaphragm flexibility on the global building response. A simple numerical modelling technique to incorporate the dynamic behaviours of flexible diaphragms in a three-dimensional equivalent frame modelling approach is also investigated, and validated against shake table test data. Finally, the applicability of nonlinear static procedures utilising single-mode, multi-mode and adaptive pushover analyses are investigated. Practical recommendations are provided for the use of various pushover analysis methods for unreinforced masonry buildings with flexible diaphragms.
Thesis (Ph.D.) (Research by Publication) -- University of Adelaide, School of Civil, Environmental and Mining Engineering, 2016.