Rozprawy doktorskie na temat „MULTISTOREYED BUILDINGS”

In the past few decades, engineers have realized that an appropriate estimation of energy dissipation on the structural system is one of the important roles in aseismic design of building structures located in hazardous seismic areas H26,P26,V9. The inelastic load-deformation behaviour of the structural members and vibration of the foundations on the flexible soil medium are two important features of the energy dissipation. Soil-structure interaction is the way to refine the existing common methods in structural analysis as it able to take into account the soil-foundation energy dissipation from the structural system. Study of the response of building structures supported by a soil medium using lumped parameter methods have been carried out by some researchers. However, most of these studies used unrealistic physical or structural responses and soil-foundation models which did not have real application in modern building aseismic design. The current New Zealand code NZS 4203:1992 states that a special study should be carried out where energy dissipation in the structural system is primarily through the rocking of foundations. Analytical investigations using the same methods in more realistic applications of aseismic design in building structures was carried out. The investigations cover several inelastic damage indicators for both frames and frame-wall structures with a different numbers of storeys, numbers of frames, hysteresis rules, rigid joint lengths, supported by different foundation types, soil models, soil stiffnesses and exited by different earthquake inputs. It was found that rocking structures exhibit advantages or disadvantages and show the inadequacy of the current wall moment design envelopes for frame-wall structures. Methods to overcome the disadvantages need to be developed. A new simple wall moment design envelope for different types of foundation and soil-foundation hysteresis rules has been proposed. In addition, the minimum required static bearing capacity factor for soil-under minimum wall gravity load and the approximation of the building's lateral fixity are also discussed.

Earthquakes are one of nature’s greatest hazards; throughout historic time they have caused significant loss of life and severe damage to property, especially to man-made structures. On the other hand, earthquakes provide architects and engineers with a number of important design criteria foreign to the normal design process. From well established procedures reviewed by many researchers, seismic isolation may be used to provide an effective solution for a wide range of seismic design problems. The application of the base isolation techniques to protect structures against damage from earthquake attacks has been considered as one of the most effective approaches and has gained increasing acceptance during the last two decades. This is because base isolation limits the effects of the earthquake attack, a flexible base largely decoupling the structure from the ground motion, and the structural response accelerations are usually less than the ground acceleration. In this research, a series of dynamic analyses are carried out to investigate in detail the seismic responses for stiff and flexible 12-storey multi storey buildings to the various isolation systems and to consider the effects of foundation compliance on their responses when subjected to different earthquakes. At the same time, an investigation of the seismic response of the recently suggested segmental buildings is carried out. The segmental building concept can be considered as an extension of the conventional base isolation technique with additional flexibility distributed in the superstructure. In addition to the conventional isolation system placed at the base, the superstructure of segmental buildings is further divided into several segments which are interconnected by extra isolation systems located in the upper storeys. In general, the increase of additional viscous damping in the structure may reduce displacement and acceleration responses of the structure. This study also seeks to evaluate the effects of additional damping on the seismic response when compared with structures without additional damping for the different ground motions. In addition, analysis and design considerations for base isolated and segmental structures are suggested to enable the designer to get a better understanding at the preliminary design stage.

2017 - 2018
One of the most widespread structural systems is represented by Moment Resisting Frames (MRFs). resistant seismic frames. This structural system is made up of frames capable of resisting seismic actions through predominantly flexural tension states. The stiffness and lateral resistance of the system depend on the flexural strength of the members and the type of connection, while the development of the plastic hinges guarantee the dissipation of the seismic input energy. The location of the dissipative zones varies according to the design approach adopted, typically they develop in beams, columns and connections. The most widespread design philosophy is to have strong columns, weak beams and full-strength rigid connections with complete resistance restoration, in this way all the seismic energy tends to be dissipated by the plastic hinges at the ends of the beams and at the base of the columns of the first level. In order to overcome the traditional design approach, the present research work introduces a new type of beam-column connection capable of exhibiting a remarkable rigidity in service conditions (SLE) and able to exhibit a remarkable dissipative capacity when a rare seismic event occurs. The codes currently in force provide that for seismic events characterized by a period of return comparable with the useful life of the structure (frequent or occasional events) the structures remain in the elastic field ensuring that the seismic energy is completely dissipated through viscous damping. Vice versa, the seismic energy must be dissipated through plastic engagement of parts of the structure, with wide and stable hysteresis cycles, for rare and very rare seismic events with a return period of about 500 years. The development of the hysteresis involves structural damage that have to be such as not to lead to the collapse of the structure in order to guarantee the protection of the life of those who occupy the building. The prediction of the behaviour of the structure in non-linear field for rare seismic events represents an aspect that only experimental research can describe in depth by developing new analytical models and innovative design philosophies. The execution of quasi-static tests can provide useful information in order to investigate the nonlinear behaviour of the members and the assemblages even if the forces or the displacement histories applied during the tests do not correspond exactly to the actions that occur during a real seismic event. The information obtained through these test procedures is however useful for calibrating analytical models and comparing the behaviour of structural components. The execution of tests on real scale structures is the best way to investigate the global behaviour of a structural system. For a more complete knowledge about the response in the dynamic field, the pseudo-dynamic tests represent a test protocol able to provide information of the structural response of a component or of a structure in a dynamic field through a static test. The main purpose of this work, developed within the FREEDAM research project financed by the European Community, is to develop an innovative beam-column connection. These innovative connections are equipped with an additional damper able to dissipating the energy deriving from destructive seismic events. The FREEDAM beam-column connection, through an appropriate design of the various components, is able to withstand frequent earthquakes and rare events without causing damage to the structural elements. The thesis is divided into six chapters. The Chapter 1 reports a brief introduction to the traditional beam-column connections, specifying the characteristics of the different types of connection and their influence on the behaviour of the Moment Resisting Frames. In the last part of the chapter the FREEDAM dissipative connection is presented, specifying its peculiarities and the benefits that its introduction into the structural system brings. The Chapter 2 is devoted to the description of the results obtained from an extensive experimental campaign developed at the STRENGTH laboratory of the University of Salerno, for the choice of material for the friction dampers used in the FREEDAM connections by carrying out a statistical characterization of the static and dynamic friction coefficients. The Chapter 3 collects the results of a further experimental campaign carried out at the University of Salerno laboratory and aimed at studying the tightening losses for pre-loading bolt systems equipped with different washers. In Chapter 4 a design procedure has been define for the FREEDAM beam-column connections, then this procedure has been applied in order to design two different types of connections that have been experimentally tested at the University of Coimbra Laboratory (PT). In the same chapter, the test layouts and the results obtained from the cyclic tests carried out on the nodes equipped with FREEDAM friction dampers have been described, finally developing models to the finite elements and comparing the experimental results with the computerized models. Finally, the Chapter 5 shows the results of the pseudo-dynamic tests carried out on a full-scale steel Moment Resistant Frame equipped in a first case with traditional full strength beam-column connections (dogbone) and in a second case equipped with the innovative connections proposed. These results have been compared to each other and with the results obtained from finite element models. [edited by Author]
XXXI ciclo

Due to the very fast urban development and population growth to the most big cities all over the world, the multi-storey buildings have increased a lot in number. Increasingly, interest is growing in exploring structural systems that allow to build multi-storey buildings. As stated also in the literature and also by Ali. M., M, in his study in 1990, among the major issues that govern the design of a multi-storey building is fulfilling the architectural aspect such as space, function, light while ensuring also the building structural rigidity.Considering also the fact emphasized by Aminmansour & Moon, 2010; Elnimeiri & Gupta, in their study in 2008, that many times, the multi-storey buildings tend to be very inefficient in terms of organisations of the interior spaces. In this regard, based on engineering logical reasoning, in order to provide the sufficient structural rigidity, it requires in many cases, considerable cross section dimensions of structural elements. On the other hands, in engineering design practices there are several cases where to ensure the stability of the building, rigid elements are placed on the building perimeter. The problem is that often, in these cases, these structural elements may interrupt several architectural aspects of the multi-storey building such as its façade, interior space, or even the entire building architectural volume. This study present reinforced concrete Structural Wall elements which are recognized as one of three main structural systems putted on the perimeter of multi-storey buildings among rigid frames and bracing systems. This research aims in suggesting an innovative structural element be implemented in the design process by both being considered as an architectural and structural element.The Structural Wall patterns with different arrangement of openings, called Perforated Structural Wall Panels, are characterized by a pattern of openings in different sizes and forms. This panel should provide the required resistance from the lateral load acting on it while offering at the same time a visual resistance presence. From the architectural point of view, this element offer the possibility to create several configurations of geometric forms, through following a precise methodology explained in further detailed study analysis presented in this study. The methodology can help towards obtaining an optimized panel by creating also a common vocabulary for both the architect and the engineer. This designed vision based on collaboration between architects and engineers aims in fostering an alternative design method outlining an effective structural scheme of multi-storey buildings composed mainly by perforated Structural Wall elements in the building perimeter. Following this design methodology, vertical structural elements would be modified in terms of preserving the required structural members and cutting of the unnecessary ones. The research concludes by discussing on how perforated Structural Wall element can help in fostering the design process and facilitate the decisions steps within designers in concluding the proper building configuration, the architectural performance and the structural rigidity.

In present scenario buildings with floating column is a typical feature in the modern multistory construction in urban India. Such features are highly undesirable in building built in seismically active areas. This study highlights the importance of explicitly recognizing the presence of the floating column in the analysis of building. Alternate measures, involving stiffness balance of the first storey and the storey above, are proposed to reduce the irregularity introduced by the floating columns. The study is carried out on a building with floating columns. The plan layout of the building is shown in the figure. The building considered is a residential building having G+9. Height of each storey is kept same as other prevalent data.

ABSTRACT In the practical design applications the evaluation of seismic response is usually based on linear elastic structural behaviour. However this approach may be not sufficient in limiting the damage levels of the buildings. To this purpose more accurate methods of analyses, which can predict the real behaviour under strong seismic actions, are required. The non-linear dynamic analysis is the most rigorous method. The non-linear static pushover analysis seems to be a more rational method for estimating the lateral strength and the distribution of inelastic deformations. In this thesis Pushover analyses were performed by ETABS to predict the behaviour under strong seismic action and comparing the forces in static linear and nonlinear analysis.

碩士
國立中央大學
土木工程研究所
92
Abstract An knowledge of the dynamic properties of building structural systems is necessary besides for accurate predictions of the dynamic responses of the systems in the seismic design of building structures, health monitoring and damage detection of existing building structures. This study is concerned with the uniqueness of the results in the identification of such properties and feasibility of the identification methods proposed here in actual application using limited earthquake records. More specifically, the viscous damping and stiffness distributions, which are of importance in the linear range of response, have been investigated. During the past four decades, a great amount of system identification methods of building structures based on linear, planar shear building models are developed. In this thesis we propose three new methods of stiffness-damping simultaneous identification of lateral-torsional coupled multistory building models using limited earthquake records. It is shown that if the responses of the floor masses just above and below a specific storey are known, and the locations of moment-resisting elements, the floor masses and the floor moments of inertia are given in N-storey building structures, the storey stiffness and the viscous damping of these elements can be identified uniquely, and that for two-storey building structures if the response of the floor mass immediately above the base and the base are known, and the locations of all moment-resisting elements, all floor masses and all floor inertias are given, the storey stiffness and the viscous damping of all elements can be identified uniquely. The accuracy of the identification methods presented in this thesis is verified and investigated through the actual limited earthquake records and numerical simulation model by means of Newmark’s integration method and the technique of the FFT (Fast Fourier Transform).

In present scenario buildings with floating column is a typical feature in the modern multistory construction in urban India. Such features are highly undesirable in building built in seismically active areas. This study highlights the importance of explicitly recognizing the presence of the floating column in the analysis of building. Alternate measures, involving stiffness balance of the first storey and the storey above, are proposed to reduce the irregularity introduced by the floating columns. FEM codes are developed for 2D multi storey frames with and without floating column to study the responses of the structure under different earthquake excitation having different frequency content keeping the PGA and time duration factor constant. The time history of floor displacement, inter storey drift, base shear, overturning moment are computed for both the frames with and without floating column.

The buildings are constructed mostly based on the usual standard codes considering the gravity loads consisting of the self-weight of the structure and the live load. These structures are experiencing low magnitude loads in their design life that leads only to the elastic range response, however, strong loads such as a sudden earthquake will lead the structure beyond its elastic limit. The performance of Reinforced Concrete structures will be nonlinear under seismic loads so the nonlinear behavior of reinforced buildings will be defined by the formation of plastic hinges and loss of considerable stiffness. In this case we need a method to evaluate the performance level of the structure in the plastic range, hence we used pushover analysis to evaluate the response of the structure to the lateral loads For the explanation above the best example can be the devastating earthquake of Nepal (25th April 2015) which has affected many buildings constructed based on traditional design codes. So it’s important to use deformation based design to avoid or at least develop the ductile behavior for structure; this will avoid the collapse of the building and will surely ensure life safety. In present study pushover analysis is carried out on G+4, G+11 and G+21 Building situated in New Delhi (Zone IV) according to IS 1893:2002 classification of seismic zones in India. Pushover analysis was performed in SAP2000 after it was designed for gravity loads in STAAD Pro based on IS-456-2000. The pushover curve, capacity spectrum, demand spectrum and Performance point of the building was found from the results of SAP2000 and hence it was concluded that the building response is highly dependent on the materials used in the design. Mostly the failure was noticed in the columns of ground story of the buildings. After using increased amount of reinforcement in the ground story the buildings have reached life safety performance level

Damage to buildings during recent earthquakes caused by increased torsional response supports the need to improve upon the existing building code design guidelines through developing a better understanding of the response of asymmetric buildings with the intent to restrict the construction of torsionally precarious structures. The effects of torsion on building response is a complex problem for even single storey structures because so many parameters are involved in the description of linear and nonlinear torsional response. Discrepancies exist between the results of many previous studies due to the number of factors governing torsional response. Researchers also have varying opinions as to how to effectively incorporate torsional effects into analytical models for building design. These controversies contribute to the fact that there are wide variations between the torsional provisions of major world design codes. Current building codes torsional provisions are only applicable to buildings which are essentially uniform vertically with relatively symmetric floor plans. Most studies examining torsional response of multistorey buildings focus on shear frame structures. This study investigates the adequacy of elastic design methods to predict and control the increased displacement and ductility demand on edge-elements of vertically uniform, multistorey, shear core buildings, designed to yield in flexure, with varying degrees of asymmetric stiffness distribution. A comparison is made between the elastic and nonlinear time history response of models designed using three elastic methods of determining element strength; the NBCC static torsional provisions (NBC), revised static torsional provisions proposed by Humar and Kumar (H/K), and a dynamic analysis with a statically applied torsional moment of 0.1b (Dyn+Tl) where b is the length of the building perpendicular to the direction of earthquake motion. The elastic static methods grossly overestimate nonlinear displacements of elements on both the stiff- and flexible-edges for torsionally flexible structures. The elastic response spectrum analysis (RSA) with shifted centre of mass (CM) best estimates inelastic displacements for all elements. Inelastic displacements of stiff- and flexible-edge elements generally increase with increasing torsional flexibility for structures with a torsional to lateral frequency ratio, Q < 1. Deformation demand increases with the magnitude of static stiffness eccentricity for the flexible-edge elements. The inelastic displacements of stiff-edge elements of torsionally stiff structures (for Q = 1.25) increase for the Dyn+Tl and sometimes for the H/K design method, leading to large ductility demands for these elements. The NBC design method best controls the displacements and, therefore, ductility demand of stiff wall elements at Ω = 1.25. The displacement response of structures with a lateral period > 2 seconds is relatively insensitive to the design method used for determining element strength distribution. The ductility demand of the flexible wall elements is below the design target for all methods of design. Dynamic magnification of base shear and storey shear forces, found by the nonlinear analyses, due to the contribution from higher modes can be more than double those predicted by elastic analysis, regardless of the elastic method employed in determining wall strengths. Also, the inelastic moment demand from the nonlinear dynamic time history analyses varies substantially from that predicted by the elastic analyses. Higher mode effects are evident in the moment and shear envelopes of the stiff and flexible walls and are more pronounced for the buildings with a lateral period > 2 seconds.

One of the most widespread structural systems is represented by Moment Resisting Frames (MRFs). This structural system is made up of frames capable of resisting seismic actions through predominantly flexural tension states. The stiffness and lateral resistance of the system depend on the flexural strength of the members and the type of connection, while the development of the plastic hinges guarantee the dissipation of the seismic input energy. The location of the dissipative zones varies according to the design approach adopted, typically they develop in beams, columns and connections. The most widespread design philosophy is to have strong columns, weak beams and full-strength rigid connections with complete resistance restoration, in this way all the seismic energy tends to be dissipated by the plastic hinges at the ends of the beams and at the base of the columns of the first level. In order to overcome the traditional design approach, the present research work introduces a new type of beam-column connection capable of exhibiting a remarkable rigidity in service conditions (SLE) and able to exhibit a remarkable dissipative capacity when a rare seismic event occurs. The codes currently in force provide that for seismic events characterized by a period of return comparable with the useful life of the construction (frequent or occasional events) the structures remain in the elastic field ensuring that the seismic energy is completely dissipated through viscous damping. Vice versa, the seismic energy must be dissipated through plastic engagement of parts of the Pseudo dynamic tests and numerical analysis of free from damage multistorey steel buildings with innovative connections structure, with wide and stable hysteresis cycles, for rare and very rare seismic events with a return period of about 500 years. The development of the hysteresis involves structural damage that have to be such as not to lead to the collapse of the structure in order to guarantee the protection of the life of those who occupy the building. The prediction of the behaviour of the structure in non-linear field for rare seismic events represents an aspect that only experimental research can describe in depth by developing new analytical models and innovative design philosophies. The execution of quasi-static tests can provide useful information in order to investigate the nonlinear behaviour of the members and the assemblages even if the forces or the displacement histories applied during the tests do not correspond exactly to the actions that occur during a real seismic event. The information obtained through these test procedures is however useful for calibrating analytical models and comparing the behaviour of structural components. The execution of tests on real scale structures is the best way to investigate the global behaviour of a structural system. For a more complete knowledge about the response in the dynamic field, the pseudo-dynamic tests represent a test protocol able to provide information of the structural response of a component or of a structure in a dynamic field through a static test. The main purpose of this work, developed within the FREEDAM research project financed by the European Community, is to develop an innovative beam-column connection. These innovative connections are equipped with an additional damper able to dissipate the energy deriving from destructive seismic events. The FREEDAM beam-column connection, through an appropriate design of the various components, is able to withstand frequent earthquakes and rare events without causing damage to the structural elements.

Detailed and entire research in the comparison of seismic behaviour of reinforced concrete structures under European seismic code and Azerbaijan seismic code are not yet provided. However, there are big interests from the Azerbaijan Republic to involve European codes as state construction norms in Azerbaijan. Because of this, comparison has been made to help Azerbaijan move to European Standards. The following aspects were taken into account in order to make a comparison of seismic codes: design states, structural types, ground conditions, important classes, seismic zones, horizontal elastic response spectrum, base shear force and distribution of the horizontal seismic forces. Chapter 4 compares results of the case study in Chapter 3. To make a seismic analysis, the existing constructed structure was taken into account to apply seismic codes of Europe and Azerbaijan. The Robot Structural Analysis software was used for modelling structure and analysing it behaviour and results. The several aspects of both seismic codes are quite similar, such as design limit states, seismic zones, but the most similar aspect observed in the research is that of the characteristics of ground types. The almost 80% of difference in base shear force is observed for studied building. Also, studies show that Azerbaijan code is much more conservative in terms of shape of elastic response spectrum in poor soil conditions than European seismic code. Basically, overall results of research show that Azerbaijan Construction Norms, in terms of seismic design, are much more conservative in all aspects comparing with European codes. The main reason for this is the high seismicity of number of regions of Azerbaijan. Also, to consider is the cost of construction materials in Azerbaijan is way less that the cost in Europe.

Диссертация посвящена проблеме возникновения шума и вибрации от трубопроводных систем многоэтажных зданий. Предложен способ определения вероятности возникновения повышенных вибраций с помощью модального анализа в программном комплексеANSYS Workbench. Представлены результаты численного анализа влияния длины, диаметра и толщины стенки участка трубопровода на изменение значений частот его собственных колебаний с целью прогноза риска возможных резонансных режимов. Выполнены статистический и регрессионный анализы.
The dissertation discusses the occurrence of noise and vibration from the piping systems of multi-storey buildings. A method for determining the probability of excessive vibrations using modal analysis software complex ANSYS Workbench. The results of the digital analysis of influence of length, diameter and thickness of a wall of the pipeline’s section on change of values of frequencies of its natural oscillations are provided. Statistical and regression analyses are made.