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1
Soesianawati, M. T. "Limited ductility design of reinforced concrete columns". Thesis, University of Canterbury. Department of Civil Engineering, 1986. http://hdl.handle.net/10092/3643.
Testo completoAbstract (sommario):
This report describes an experimental and analytical investigation
of the strength and ductility of reinforced concrete columns.
Four columns of square cross-section were tested under axial
compression loading and cyclic lateral loading applied at mid-height which
simulated seismic loading.
The main variable investigated was the quantity of transverse
confining steel used, which ranged between 17 to 46 percent of the NZS
3101:1982 recommended quantity for ductile detailing.
The experimental results are reported in the form of lateral loaddisplacement
and lateral load-curvatures hysteresis loops, curvature
profiles, transverse steel strain distributions and concrete compressive
strains.
The results are discussed and compared with the analytical predictions.
A modified equation for the quantity of confining reinforcement in
rectangular columns is recommended. Conclusions are made regarding the
ductility available from columns containing substantially less transverse
confining reinforcement than recommended by the New Zealand concrete
design code.
2
Lau, Tak-bun Denvid. "Flexural ductility improvement of FRP-reinforced concrete members". Click to view the E-thesis via HKUTO, 2006. http://sunzi.lib.hku.hk/hkuto/record/B38907756.
Testo completo
3
Kim, SangHun Aboutaha Riyad S. "Ductility of carbon fiber-reinforced polymer (CFRP) strengthened reinforced concrete". Related Electronic Resource: Current Research at SU : database of SU dissertations, recent titles available full text, 2003. http://wwwlib.umi.com/cr/syr/main.
Testo completo
4
Lau, Tak-bun Denvid, e 劉特斌. "Flexural ductility improvement of FRP-reinforced concrete members". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2006. http://hub.hku.hk/bib/B38907756.
Testo completo
5
Watson, Soesianawati. "Design of reinforced concrete frames of limited ductility". Thesis, University of Canterbury. Department of Civil Engineering, 1989. http://hdl.handle.net/10092/3745.
Testo completoAbstract (sommario):
An experimental programme was carried out to investigate the flexural strength and ductility.
of reinforced concrete columns under simulated earthquake loading. The main variable
examined was the quantity of transverse reinforcement for concrete confinement. The experimental
results were described and compared with theoretical studies. It was found that
to achieve adequate ductility in columns, the current New Zealand concrete design code
NZS3101:1982 equations for concrete confinement need to be refined. Using design charts
for ductility, which were previously derived from a theory for cyclic moment-curvature behaviour,
a refined design equation to replace the current code equations is proposed.
The inelastic dynamic response of frames of limited ductility was examined, and compared
with the response of ductile frames. The analysis indicated that non-capacity designed
frames, designed for seismic forces corresponding to a limited ductility demand, performed
reasonably well. Although some plastic hinges did develop in the columns, the ductility
demand was acceptable and can be achieved by appropriate detailing. As a result, some
suggestions for the seismic design requirements of frames of limited ductility are presented.
6
Azizi, Abdul R. "Modelling moment redistribution in continuous reinforced concrete beams". Thesis, Durham University, 1996. http://etheses.dur.ac.uk/1578/.
Testo completo
7
Zaina, Mazen Said Civil & Environmental Engineering Faculty of Engineering UNSW. "Strength and ductility of fibre reinforced high strength concrete columns". Awarded by:University of New South Wales. School of Civil and Environmental Engineering, 2005. http://handle.unsw.edu.au/1959.4/22054.
Testo completoAbstract (sommario):
The main structural objectives in column design are strength and ductility. For higher strength concretes these design objectives are offset by generally poor concrete ductility and early spalling of the concrete cover. When fibres are added to the concrete the post peak characteristics are enhanced, both in tension and in compression. Most of the available experimental data, on fibre reinforced concrete and fibre reinforced high strength concrete columns, suggest that an improvement in both ductility and load carrying capacity due to the inclusion of the fibres. In this thesis the ductility and strength of fibre reinforced high strength concrete are investigated to evaluate the effect of the different parameters on the performance of columns. The investigation includes both experimental and the numerical approaches with 56 high strength fibre reinforced concrete columns being tested. The concrete strength ranged between 80 and 100 MPa and the columns were reinforced with 1, 2 or 2.6 percent, by weight, of end hooked steel fibres. The effect of corrugated Polypropylene fibres on the column performance was also examined. No early spalling of the cover was observed in any of the steel fibre reinforced column tested in this study. A numerical model was developed for analysis of fibre and non-fibre reinforced eccentrically loaded columns. The column is modelled as finite layers of reinforced concrete. Two types of layers are used, one to represent the hinged zone and the second the unloading portion of the column. As the concrete in the hinged layers goes beyond the peak for the stress verus strain in the concrete the section will continue to deform leading to a localised region within a column. The numerical model is compared with the test data and generally shows good correlation. Using the developed model, the parameters that affect ductility in fibre-reinforced high strength concrete columns are investigated and evaluated. A design model relating column ductility with confining pressure is proposed that includes the effects of the longitudinal reinforcement ratio, the loading eccentricity and the fibre properties and content and design recommendations are given.
8
Davies, Paul. "Ductility and Deformability of FRP Strengthened Reinforced Concrete Structures". Thesis, University of South Wales, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.517957.
Testo completo
9
Wassouf, Mohamad. "Bond and ductility of concrete reinforced with various steel bars surface and ductility conditions". Thesis, University of Birmingham, 2015. http://etheses.bham.ac.uk//id/eprint/6272/.
Testo completoAbstract (sommario):
Reinforced concrete is a wide field for researches and studies in civil engineering subject. It is due to the fact that reinforced concrete is the most widely used material for the infrastructure in the world. Reinforced concrete consists of two main materials: reinforcing steel and concrete, each of those two materials has its own effect on the performance of the structure. In this thesis, the change in RC performance due to different steel properties and specifications will be investigated. The study focuses on the bond interaction between steel and concrete and the flexural behaviour of RC beams. Pull-out forces have been exerted on the reinforcing bars in RC blocks to examine the impact of steel properties on the bond strength and failure mode of the blocks. In addition to that, flexural tests have been conducted on simply supported RC beams to investigate how reinforcement properties can affect the ductility of reinforced concrete. Comparison of results of the previous two tests with codes and analytical models have been carried out to verify the outcome of this research.
10
Ho, Yin Bon. "Enhancing the ductility of non-seismically designed reinforced concrete shear walls /". View abstract or full-text, 2006. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202006%20HO.
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11
Mostofinejad, Davood. "Ductility and moment redistribution in continuous FRP reinforced concrete beams". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ26859.pdf.
Testo completo
12
Zahn, Franz August. "Design of reinforced concrete bridge columns for strength and ductility". Thesis, University of Canterbury. Department of Civil Engineering, 1985. http://hdl.handle.net/10092/2872.
Testo completoAbstract (sommario):
Methods for the design of reinforced concrete bridge columns and
piers for strength and ductility are considered. The investigations cover
the following areas.
An experimental investigation of the influence of reinforcing steel
grade and amount of confining steel on the stress-strain behaviour of
confined concrete is presented. The results are discussed and compared
with theoretical models. Special attention is given to the possibility
of fracture of the confining steel.
An extensive experimental investigation into the ductile performance
of a range of reinforced concrete columns is presented. The columns were
subjected to constant axial load and cyclic lateral displacements. The
test units included four square columns with the lateral load applied
in the direction of a cross section diagonal, six circular hollow columns
with different wall thickness to diameter ratios, and four columns with
transverse reinforcement from Grade 380 steel. The available strength and
ductility of the columns is discussed and compared with the performance
of columns tested previously at the University of Canterbury, and with
theoretical predictions using monotonic as well as cyclic moment-curvature
analyses. The main variables for the solid columns were the influence of
biaxial bending, the use of Grade 380 transverse steel for confinement,
and the spacing between transverse bars along the column axis. The
circular hollow columns were unconfined on the inside face of the tube
wall, and the main variables were the influence of the axial load level
and the wall thickness.
The implications of the column test results, including the results
of other investigations, for the design of reinforced concrete columns
for strength and ductility are discussed and, where appropriate, used to
calibrate theoretical models. In particular, the influence of cyclic
loading on the strength deterioration of reinforced concrete columns with
high axial loads is emphasized. More realistic definitions of the ideal
flexural strength, of the flexural overstrength and of the yield curvature
are suggested and, together with a set of criteria for the ultimate limit
state, used to establish design charts for the available strength and
ductility of reinforced concrete columns. A cyclic moment-curvature
analysis was used for this purpose, incorporating cyclic stress-strain
models for the concrete and for the steel, thus taking into account the
cyclic strength deterioration observed for columns with high axial loads.
Finally, a rational step-by-step design procedure is presented that
will make less complex the task of considering the great number of
variables involved in the seismic design of reinforced concrete columns
for both strength and ductility.
13
Goodfellow, Roderick Gerald Charles. "Ductility of reinforced concrete flexural members constructed from high performance steel and concrete". Thesis, Imperial College London, 1999. http://hdl.handle.net/10044/1/7645.
Testo completo
14
Ozcan, Okan. "Improving Ductility And Shear Capacity Of Reinforced Concrete Columns With Carbon Fiber Reinforced Polymer". Phd thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/12611292/index.pdf.
Testo completoAbstract (sommario):
The performance of reinforced concrete (RC) columns during recent earthquakes has clearly demonstrated the possible failures associated with inadequate confining reinforcement. The confinement reinforcement requirements of older codes were less stringent than present standards. Many studies were conducted by applying different retrofitting techniques for RC columns that have inadequate confinement reinforcement. A new retrofitting technique by means of Carbon Fiber Reinforced Polymer (CFRP) was developed and tested in many countries in the last decade. This technique is performed by CFRP wrapping the critical region of columns. The effectiveness of CFRP retrofitting technique was shown in many studies conducted worldwide. In Turkey, the frame members are considerably deficient from the seismic detailing point of view. Therefore, in order to use the CFRP retrofitting technique effectively in Turkey, experimental evidence is needed. This study investigates the performance of CFRP retrofitted RC columns with deficient confining steel and low concrete strength. It was concluded by experimental and analytical results that the CFRP retrofitting method can be implemented to seismically deficient columns. Moreover, two design approaches were proposed for CFRP retrofit design of columns considering safe design regulations.
15
Adwan, Osama K. "Engineering properties and structural behaviour of high strength reinforced concrete beams". Thesis, University of Abertay Dundee, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360744.
Testo completo
16
Islam, Md Shahidul. "Shear capacity and flexural ductility of reinforced high- and normal-strength concrete beams". Thesis, Hong Kong : University of Hong Kong, 1996. http://sunzi.lib.hku.hk/hkuto/record.jsp?B1766536X.
Testo completo
17
Gravina, Rebecca Jane. "Non-linear overload behaviour and ductility of reinforced concrete flexural members containing 500MPa grade steel reinforcement". Title page, contents and abstract only, 2002. http://web4.library.adelaide.edu.au/theses/09PH/09phg777.pdf.
Testo completoAbstract (sommario):
Includes corrigenda (inserted at front) and list of publications published as a result of this research. Includes bibliographical references (leaves 192-199) Investigates the overload behaviour and modes of collapse of reinforced concrete flexural members containing 500MPa grade reinforcing steel and evaluates the adequacy of current ductility requirements for design according to AS 3600 to ensure strength and safety.
18
Denton, Stephen Richard. "The strength of reinforced concrete slabs and the implications of limited ductility". Thesis, University of Cambridge, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.274164.
Testo completo
19
Shwani, Mohamed K. "Enhancing Ductility of One-way Concrete Slabs Reinforced With Welded Wire Reinforcement". DigitalCommons@USU, 2017. https://digitalcommons.usu.edu/etd/6894.
Testo completoAbstract (sommario):
A series of research studies have recently identified an issue called strain localization in welded wire reinforced (WWR) members. This phenomenon reportedly concentrates strains at welded cross wire locations and severely limit ductility. Those that identified the phenomenon used it to imply that WWR is unsafe because it does not warn of failure. This dissertation is investigating details to mitigate the strain localization effect and demonstrate the WWR can be used safely. A moment curvature analysis is developed using Response2000 program and calibrated using experimental data. Parametric study was developed to present a recommendation of details and minimum reinforcement required for WWR slabs. The effect of different types of WWR coating on mechanical properties were investigated. The dissertation next examined the effects of strain rate on the mechanical properties of WWR and traditional rebar.
In total, fifty four slabs have been constructed using WWR and rebar with various cross wire spacing, using a realistic design. The strain localization phenomenon was not demonstrated, but WWR slabs are somewhat less ductile than traditionally reinforced members. The WWR members were shown to provide adequate ductility for warning of impending failure visually and with a well-accepted ductility measure. The WWR members were also shown the ability of load redistribution.
The effect of coating demonstrates that both galvanizing WWR and coating WWR with epoxy has a positive effect on mechanical properties, along with adding corrosion resistance.
The effect of strain rate shows that increase in loading rate tend to increase the yield and ultimate stresses and percent area reduction, however the loading rate increase does not have a significant effect on elastic modulus, elongation and uniform elongation.
20
Islam, Mohammad M. "Moment redistribution in reinforced concrete beams and one-way slabs using 500 MPa steel". Thesis, Curtin University, 2002. http://hdl.handle.net/20.500.11937/631.
Testo completoAbstract (sommario):
In the Australian Standard, AS 3600-2001, the neutral axis parameter Ku is used as a convenient, but approximate, parameter to design for moment redistribution in building frames. The research work reported herein was conducted to obtain complete information regarding moment redistribution of beams and one-way slabs using 500 MPa steel reinforcement.A computer based iterative numerical method was developed to analyse reinforced two-span continuous concrete beams and one-way slabs. The method takes into account the material and geometrical non-linearities in the calculations. The deflected shape of the beam and one-way slab was calculated by dividing the span length into a number of rigid segments. The program also calculates the failure load and extent of moment redistribution. The analytical method was verified against the test results reported in the literature. The analytical results for load-deflection graphs and moment redistribution showed a good agreement with the test results.A parametric study was conducted using analytical method. The results of this study showed that moment redistribution depends not only on the neutral axis parameter (Ku) but also on the ratio of neutral axis parameter (Ku-/Ku+), ultimate steel strain (ªsu) and concrete compressive strength (fc).
21
Lyon, Jeffrey G. "FRP CONFINED REINFORCED CONCRETE CIRCULAR CROSS SECTION SEISMIC APPLICATIONS". DigitalCommons@CalPoly, 2009. https://digitalcommons.calpoly.edu/theses/149.
Testo completoAbstract (sommario):
In recent earthquakes, structures have not performed as well as expected resulting in a need for better means of retrofitting and improvements in seismic design. Fiber Reinforced Polymers (FRP), as a material with potential to increase strength and ductility of columns in conjunction with capacity design methodology, has promise for seismic design. By investigating the displacement, ductility, and flexural strength properties of FRP confined reinforced concrete circular cross sections, this study analyzes the seismic applications of FRP confinement.
The study is performed by incorporating an FRP confined concrete stress-strain model into a developed Moment-Curvature and PM Interaction software. This software conducts a comparison between traditional steel and FRP confined sections while performing parameter studies on the 28-day unconfined concrete compressive strength, longitudinal reinforcing ratio, cross section diameter, FRP confinement jacket thickness-cross section diameter ratio, and FRP confinement system design variables. These studies validate FRP’s performance for seismic applications resulting in several design recommendations to increase displacement capacity, ductility, and flexural strength and, thus, seismic performance.
22
Chau, Siu-lee. "Effects of confinement and small axial load on flexural ductility of high-strength reinforced concrete beams". Click to view the E-thesis via HKUTO, 2005. http://sunzi.lib.hku.hk/hkuto/record/B31997661.
Testo completo
23
Chen, Mantai, e 陈满泰. "Combined effects of strain gradient and concrete strength on flexural strength and ductility design of RC beams and columns". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/206429.
Testo completoAbstract (sommario):
The stress-strain relationship of concrete in flexure is one of the essential parameters in assessing the flexural strength and ductility of reinforced concrete (RC) structures. An overview of previous research studies revealed that the presence of strain gradient would affect the maximum concrete stress and respective strain developed in flexure. Previously, researchers have conducted experimental studies to investigate and quantify the strain gradient effect on maximum concrete stress and respective strain by developing two strain-gradient-dependent factors k3 and ko for modifying the flexural concrete stress-strain curve.
In this study, the author established a new analytical concrete constitutive model to describe the stress-strain behavior of both normal-and high-strength concrete in flexure with the effect of strain gradient considered. Based on this, comprehensive parametric studies have been conducted to investigate the combined effects of strain gradient and concrete strength on flexural strength and ductility design of RC beams and columns with concrete strength up to 100 MP a by employing the strain-gradient-dependent concrete stress-strain curve using non-linear moment-curvature analysis.
From the results of the parametric studies, it is evident that both the flexural strength and ductility of RC beams and columns are improved under strain gradient effect. A design value of ultimate concrete strain of 0.0032and anew equivalent rectangular concrete stress block incorporating the combined effects of strain gradient and concrete strength have been proposed and validated by comparing the proposed theoretical strength with the strength of 198 RC beams and 275 RC columns measured experimentally by other researchers. It is apparent from the comparison that the proposed equations can predict more accurately the flexural strength of RC beams and columns than the current RC design codes.
Lastly, for practical engineering design purpose, design formulas and charts have been produced for flexural strength and ductility design of RC beams and columns incorporating the combined effects of strain gradient and concrete strength.published_or_final_version
Civil Engineering
Master
Master of Philosophy
24
Chau, Siu-lee, e 周小梨. "Effects of confinement and small axial load on flexural ductility of high-strength reinforced concrete beams". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2005. http://hub.hku.hk/bib/B31997661.
Testo completo
25
Yosefani, Anas. "Flexural Strength, Ductility, and Serviceability of Beams that Contain High-Strength Steel Reinforcement and High-Grade Concrete". PDXScholar, 2018. https://pdxscholar.library.pdx.edu/open_access_etds/4402.
Testo completoAbstract (sommario):
Utilizing the higher capacity steel in design can provide additional advantages to the concrete construction industry including a reduction of congestion, improved concrete placement, reduction in the required reinforcement and cross sections which would lead to savings in materials, shipping, and placement costs. Using high-strength reinforcement is expected to impact the design provisions of ACI 318 code and other related codes.
The Applied Technology Council (ATC-115) report "Roadmap for the Use of High-Strength Reinforcement in Reinforced Concrete Design" has identified key design issues that are affected by the use of high-strength reinforcement. Also, ACI ITG-6, "Design Guide for the Use of ASTM A1035 Grade 100 Steel Bars for Structural Concrete" and NCHRP Report 679, "Design of Concrete Structures Using High-Strength Steel Reinforcement" have made progress towards identifying how code provisions in ACI 318 and AASHTO could be changed to incorporate high-strength reinforcement.
The current research aims to provide a closer investigation of the behavior of beams reinforced with high-strength steel bars (including ASTM A615 Grade 100 and ASTM A1035 Grades 100 and 120) and high-strength concrete up to 12000 psi. Focus of the research is on key design issues including: ductility, stiffness, deflection, and cracking.
The research includes an extensive review of current literature, an analytical study and conforming experimental tests, and is directed to provide a number of recommendations and design guidelines for design of beams reinforced with high-strength concrete and high-strength steel. Topics investigated include: strain limits (tension-controlled and compression-controlled, and minimum strain in steel); possible change for strength reduction factor equation for transition zone (Φ); evaluation of the minimum reinforcement ratio (þmin); recommendations regarding limiting the maximum stress for the high-strength reinforcement; and prediction of deflection and crack width at service load levels. Moreover, this research includes long-term deflection test of a beam made with high grade concrete and high-strength steel under sustained load for twelve months to evaluate the creep deflection and to insure the appropriateness of the current ACI 318 time-dependent factor, λ, which does not consider the yield strength of reinforcement and the concrete grade.
26
Plumb, Alex David. "Seismic Behavior of GFRP-Reinforced Concrete Beams and Moment Frames". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021.
Cerca il testo completoAbstract (sommario):
The use of fiber reinforced polymer (FRP) bars as internal reinforcement for concrete structures has grown in frequency within the past thirty years, owing mainly to the material’s resistance to corrosion. This development is prevalent in coastal regions where the chemical attack from seawater can weaken steel reinforcement, the traditional reinforcing material in concrete. However, a large obstacle remains in replacing all steel reinforcement with FRP reinforcement in these areas: coastal regions are some of the most seismically active areas in the world. Research on FRP bars shows they behave linear-elastically and exhibit brittle, as opposed to ductile, failure. This is impractical for acceptable seismic design, where the ductile performance of the structure is advantageous to absorb the earthquake loads. Due to this, the outlook for FRP reinforced concrete in seismic zones is seemingly limited. But recent research, although from a small sample size, has shown promising results. This research aims to build upon these findings and expand the knowledge of FRP reinforced concrete performance under seismic loads, especially for beams and moment frames. An analytical study was performed to examine (i) the cross-section of a hybrid glass (G)FRP-steel-reinforced beam through moment-curvature analysis and (ii) two concrete moment frames with GFRP-reinforced beams and steel-reinforced columns subjected to simulated seismic loading through pushover analysis. The performance of the primarily GFRP reinforced concrete design was evaluated by parameters such as curvature ductility (9.0), structural ductility (2.1 and 5.0), and lateral drift. The results showed significant potential for the use of GFRP in seismically active regions.
27
Abdulkadir, Ramzi I. "Strength and ductility of concrete columns reinforced with welded wire fabric and/or rebars". Thesis, University of Ottawa (Canada), 1991. http://hdl.handle.net/10393/6020.
Testo completoAbstract (sommario):
Research was carried out to investigate the characteristics of concrete confined by welded wire fabric. The column reinforcement consisted of only welded wire fabric, without the use of any reinforcing bars. The increase in confinement was relatively small. The ductility enhancement was also limited. It was concluded that, unless special size welded wire fabric was used to have adequate percentage of steel, the standard size mesh was not suitable for use as column reinforcement. The test results were compared against analytical predictions obtained from the use of Saatcioglu and Razvi model for confined concrete. Having established the validity of the model, a parametric study was carried out to establish the significance of confinement parameters for columns reinforced with welded wire fabric, reinforcing bars, and a combination of the two. It was found that the combined use of reinforcing bars and welded wire fabric offered the optimum solution, where the bars formed the main reinforcement, and the mesh provided superior concrete confinement. (Abstract shortened by UMI.)
28
Carlin, Brian Patrick. "Investigation of the Strength and Ductility of Reinforced Concrete Beams Strengthed with CFRP Laminates". Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/36546.
Testo completoAbstract (sommario):
The use of fiber reinforced plastics (FRP) in repairing and strengthening bridges has been researched in recent years. In particular, attaching unidirectional FRP to the tension face of reinforced concrete beams has provided an increase in stiffness and load capacity of the structure. However, due to the brittle nature of the unidirectional FRP, the ductility of the beam decreases. One possible solution to this problem is the use of cross-ply or off-axis FRP laminates. This thesis focuses on the investigation of the flexural behavior of reinforced concrete beams strengthened with one of two different FRP orientations (0°/90° and ±45°). More particularly, the change in strength and ductility of the beams as the number of FRP layers are altered is investigated. Seven under-reinforced concrete beams were constructed and tested to failure. With the exception of the control beam, each specimen was applied with two, three, or four layers of either 0°/90° and ±45° FRP orientations. To predict the flexural behavior of the specimens, a theoretical model was derived using basic concepts, past research, and the tested properties of the concrete, steel reinforcement, and FRP. Also, two methods were used to analyze the ductility of the tested beams. Along with the test details of each specimen; the moment, deflection, CFRP strain, crack patterns, and mode of failure are discussed. The results included an increase in load capacity with respect for the number of CFRP layers applied for both orientations. Also, the ductility of the beams were reduced by adding CFRP orientations.Master of Science
29
Mohammed, Mohammed Gaber Elshamandy. "GFRP-reinforced concrete columns under simulated seismic loading". Thèse, Université de Sherbrooke, 2017. http://hdl.handle.net/11143/10242.
Testo completoAbstract (sommario):
Abstract : Steel and fiber-reinforced-polymer (FRP) materials have different mechanical and physical characteristics. High corrosion resistance, high strength to weight ratio, non-conductivity, favorable fatigue enable the FRP to be considered as alternative reinforcement for structures in harsh environment. Meanwhile, FRP bars have low modulus of elasticity and linear-elastic stress-strain curve. These features raise concerns about the applicability of using such materials as reinforcement for structures prone to earthquakes. The main demand for the structural members in structures subjected to seismic loads is dissipating energy without strength loss which is known as ductility. In the rigid frames, columns are expected to be the primary elements of energy dissipation in structures subjected to seismic loads.
The present study addresses the feasibility of reinforced-concrete columns totally reinforced with glass-fiber-reinforced-polymer (GFRP) bars achieving reasonable strength and the drift requirements specified in various codes. Eleven full-scale reinforced concrete columns—two reinforced with steel bars (as reference specimens) and nine totally reinforced with GFRP bars—were constructed and tested to failure. The columns were tested under quasi-static reversed cyclic lateral loading and simultaneously subjected to compression axial load. The columns are 400 mm square cross-section with a shear span 1650 mm. The specimen simulates a column with 3.7 m in height in a typical building with the point of contra-flexure located at the column mid-height. The tested parameters were the longitudinal reinforcement ratio (0.63, 0.95 and 2.14), the spacing of the transverse stirrups (80, 100, 150), tie configuration (C1, C2, C3 and C4), and axial load level (20%, 30% and 40%).
The test results clearly show that properly designed and detailed GFRP-reinforced concrete columns could reach high deformation levels with no strength degradation. An acceptable level of energy dissipation compared with steel-reinforced concrete columns is provided by GFRP reinforced concrete columns. The dissipated energy of GFRP reinforced concrete columns was 75% and 70% of the counter steel columns at 2.5% and 4% drift ratio respectively. High drift capacity achieved by the columns up to 10% with no significant loss in strength. The high drift capacity and acceptable dissipated energy enable the GFRP columns to be part of the moment resisting frames in regions prone to seismic activities. The experimental ultimate drift ratios were compared with the estimated drift ratios using the confinement Equation in CSA S806-12. It was found from the comparison that the confinement Equation underestimates values of the drift ratios thus the experimental drift ratios were used to modify transverse FRP reinforcement area in CSA S806-12. The hysteretic behavior encouraged to propose a design procedure for the columns to be part of the moderate ductile and ductile moment resisting frames. The development of design guidelines, however, depends on determining the elastic and inelastic deformations and on assessing the force modification factor and equivalent plastic-hinge length for GFRP-reinforced concrete columns. The experimental results of the GFRP-reinforced columns were used to justify the design guideline, proving the accuracy of the proposed design equations.L’acier et les matériaux à base de polymères renforcés de fibres (PRF) ont des caractéristiques physiques et mécaniques différentes. La résistance à la haute corrosion, le rapport résistance vs poids, la non-conductivité et la bonne résistance à la fatigue font des barres d’armature en PRF, un renforcement alternatif aux barres d’armature en acier, pour des structures dans des environnements agressifs. Cependant, les barres d’armature en PRF ont un bas module d’élasticité et une courbe contrainte-déformation sous forme linéaire. Ces caractéristiques soulèvent des problèmes d'applicabilité quant à l’utilisation de tels matériaux comme renforcement pour des structures situées en forte zone sismique. La principale exigence pour les éléments structuraux des structures soumises à des charges sismiques est la dissipation d'énergie sans perte de résistance connue sous le nom de ductilité. Dans les structures rigides de type cadre, on s'attend à ce que les colonnes soient les premiers éléments à dissiper l'énergie dans les structures soumises à ces charges. La présente étude traite de la faisabilité des colonnes en béton armé entièrement renforcées de barres d’armature en polymères renforcés de fibres de verre (PRFV), obtenant une résistance et un déplacement latéral raisonnable par rapport aux exigences spécifiées dans divers codes. Onze colonnes à grande échelle ont été fabriquées: deux colonnes renforcées de barres d'acier (comme spécimens de référence) et neuf colonnes renforcées entièrement de barres en PRFV. Les colonnes ont été testées jusqu’à la rupture sous une charge quasi-statique latérale cyclique inversée et soumises simultanément à une charge axiale de compression. Les colonnes ont une section carrée de 400 mm avec une portée de cisaillement de 1650 mm pour simuler une colonne de 3,7 m de hauteur dans un bâtiment typique avec le point d’inflexion situé à la mi-hauteur. Les paramètres testés sont : le taux d’armature longitudinal (0,63%, 0,95% et 2,14 %), l'espacement des étriers (80mm, 100mm, 150 mm), les différentes configurations (C1, C2, C3 et C4) et le niveau de charge axiale (20%, 30 % et 40%). Les résultats des essais montrent clairement que les colonnes en béton renforcées de PRFV et bien conçues peuvent atteindre des niveaux de déformation élevés sans réduction de résistance. Un niveau acceptable de dissipation d'énergie, par rapport aux colonnes en béton armé avec de l’armature en acier, est atteint par les colonnes en béton armé de PRFV. L'énergie dissipée des colonnes en béton armé de PRFV était respectivement de 75% et 70% des colonnes en acier à un rapport déplacement latéral de 2,5% et 4%. Un déplacement supérieur a été atteint par les colonnes en PRFV jusqu'à 10% sans perte significative de résistance. La capacité d’un déplacement supérieur et l’énergie dissipée acceptable permettent aux colonnes en PRFV de participer au moment résistant dans des régions sujettes à des activités sismiques. Les rapports des déplacements expérimentaux ultimes ont été comparés avec les rapports estimés en utilisant l’Équation de confinement du code CSA S806-12. À partir de la comparaison, il a été trouvé que l’Équation de confinement sous-estime les valeurs des rapports de déplacement, donc les rapports de déplacement expérimentaux étaient utilisés pour modifier la zone de renforcement transversal du code CSA S806-12. Le comportement hystérétique encourage à proposer une procédure de conception pour que les colonnes fassent partie des cadres rigides à ductilité modérée et résistant au moment. Cependant, l'élaboration de guides de conception dépend de la détermination des déformations élastiques et inélastiques et de l'évaluation du facteur de modification de la force sismique et de la longueur de la rotule plastique pour les colonnes en béton armé renforcées de PRFV. Les résultats expérimentaux des colonnes renforcées de PRFV étudiées ont été utilisés pour justifier la ligne directrice de conception, ce qui prouve l’efficacité des équations de conception proposées.
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Islam, Mohammad M. "Moment redistribution in reinforced concrete beams and one-way slabs using 500 MPa steel". Curtin University of Technology, Department of Civil Engineering, 2002. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=13212.
Testo completoAbstract (sommario):
In the Australian Standard, AS 3600-2001, the neutral axis parameter Ku is used as a convenient, but approximate, parameter to design for moment redistribution in building frames. The research work reported herein was conducted to obtain complete information regarding moment redistribution of beams and one-way slabs using 500 MPa steel reinforcement.A computer based iterative numerical method was developed to analyse reinforced two-span continuous concrete beams and one-way slabs. The method takes into account the material and geometrical non-linearities in the calculations. The deflected shape of the beam and one-way slab was calculated by dividing the span length into a number of rigid segments. The program also calculates the failure load and extent of moment redistribution. The analytical method was verified against the test results reported in the literature. The analytical results for load-deflection graphs and moment redistribution showed a good agreement with the test results.A parametric study was conducted using analytical method. The results of this study showed that moment redistribution depends not only on the neutral axis parameter (Ku) but also on the ratio of neutral axis parameter (Ku-/Ku+), ultimate steel strain (ªsu) and concrete compressive strength (fc).
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Tanaka, Hitoshi. "Effect of lateral confining reinforcement on the ductile behaviour of reinforced concrete columns". Thesis, University of Canterbury. Civil Engineering, 1990. http://hdl.handle.net/10092/1241.
Testo completoAbstract (sommario):
This thesis is concerned with the effects of lateral confining reinforcement on the ductile behaviour of reinforced concrete columns. The contents of the chapters are summarized as follows. In Chapter one, the general problems in seismic design are discussed and earthquake design methods based on the ductile design approach are described. Japanese, New Zealand and United States design codes are compared. Finally, the scope of this research project is outlined. In Chapter two, after reviewing previous research on confined concrete, the factors which affect the effectiveness of lateral confinement are discussed. Especially the effects of the yield strength of transverse reinforcement, the compressive strength of plain concrete and the strain gradient in the column section due to bending are discussed based on tests which were conducted by the author et al at Kyoto University and Akashi Technological College, Japan. In the axial compression tests on spirally reinforced concrete cylinders (150 mm in diameter by 300 mm in height), the yield strength of transverse reinforcement and the compressive strength of plain concrete were varied from 161 MPa to 1352 MPa and from 17 MPa to 60 MPa, respectively, as experimental parameters. It is found that, when high strength spirals are used as confining reinforcement, the strength and ductility of the confined core concrete are remarkably enhanced but need to be estimated assuming several failure modes which could occur. These are based on the observations that concrete cylinders with high strength spirals suddenly failed at a concrete compressive strain of 2 to 3.5 % due to explosive crushing of the core concrete between the spiral bars or due to bearing failure of the core concrete immediately beneath the spiral bars, while the concrete cylinders with ordinary strength spirals failed in a gentle manner normally observed. In addition, eccentric loading tests were conducted on concrete columns with 200 mm square section confined by square spirals. It is found that the effectiveness of confining reinforcement is reduced by the presence of the strain gradient along the transverse section of column. In Chapter three, the effectiveness of transverse reinforcement with various types of anchorage details which simplify the fabrication of reinforcing cages are investigated. Eight reinforced concrete columns, with either 400 mm or 550 mm square cross sections, were tested subjected to axial compression loading and cyclic lateral loading which simulated a severe earthquake. The transverse reinforcement consisted of arrangements of square perimeter hoops with 135° end hooks, cross ties with 90° and 135° or 180° end hooks, and 'U' and 'J' shaped cross ties and perimeter hoops with tension splices. Conclusions are reached with regard to the effectiveness of the tested anchorage details in the plastic hinge regions of columns designed for earthquake resistance. In Chapter four, the effectiveness of interlocking spirals as transverse reinforcement is studied. Firstly, the general aspects and the related problems of interlocking spirals to provide adequate ductility in the potential plastic hinge region of columns are discussed, referring to the provisions in the New Zealand code,the CALTRANS (California Transportation Authority) code and other related codes. Secondly, based on those discussions, a design method to securely interlock the spirals is proposed. Thirdly, the effectiveness of interlocking spirals is assessed based on column tests conducted as part of this study. Three columns with interlocking spirals and, for comparison, one rectangular column with rectangular hoopsandcross ties, were tested under cyclic horizontal loading which simulated a severe earthquake. The sections of those columns were 400 mm by 600 mm. In Chapter five, analytical models to investigate the buckling behaviour of longitudinal reinforcement restrained by cross ties with 90° and 135° end hooks and by peripheral hoops are proposed. The analyzed results using the proposed models compare well with the experimental observations described in Chapter three. Using those proposed models, a method to check the effectiveness of cross ties with 90° and 135° end hooks is proposed for practical design purposes. In Chapter six, a theory for the prediction of the ultimate longitudinal compressive concrete strain at the stage of first hoop fracture referred to as the "Energy Balance Theory", which has been developed by Mander, Priestley and Park at University of Canterbury, is introduced. After discussing the problems in the "Energy Balance Theory", a modified theory for the prediction of the ultimate longitudinal compressive concrete strain at the stage of first hoop fracture is proposed. The predictions from the modified theory are found to compare well with previous experimental results.
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Peng, Jun, e 彭军. "Strain gradient effects on flexural strength and ductility design of normal-strength RC beams and columns". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hub.hku.hk/bib/B48329630.
Testo completoAbstract (sommario):
The stress-strain characteristics of concrete developed in flexure is very important for flexural strength design of reinforced concrete (RC) members. In current RC design codes, the stress-strain curve of concrete developed in flexure is obtained by scaling down the uni-axial stress-strain curve to account for the strain gradient effect. Therefore, the maximum concrete stress that can be developed under flexure is smaller than its uni-axial strength, and the use of which always underestimates the flexural strength of RC beams and columns even though the safety factors for materials are taken as unity. Furthermore, the value of strength underestimation was different for RC beams and columns, which indicates that the extent of strain gradient will affect the maximum concrete stress and stress-strain curve developed under flexure.
To investigate the maximum concrete stress, 29 column specimens were fabricated and tested in this study. They were divided into 9 groups, each of which was poured from the same batch of concrete and contained specimens with identical cross-section properties. In each group, one specimen was tested under concentric load while the rest was/were subjected to eccentric or horizontal load. To study the strain gradient effects, the ratio of the maximum concrete compressive stress developed in the eccentrically/horizontally loaded specimens to the maximum uni-axial compressive stress developed in the counterpart concentrically loaded specimens, denoted by k3, is determined based on axial force and moment equilibriums. Subsequently, the concrete stress block parameters and the equivalent rectangular concrete stress block parameters are determined. It is found that the ratios of the maximum and equivalent concrete stress to uni-axial cylinder strength, denoted respectively by k3 and , depend significantly on strain gradient, while that of the depth of stress block to neutral axis depth, denoted by , remains relatively constant with strain gradient. Design equations are proposed to relate and with strain gradient for strength calculation, whose applicability is verified by comparing the strengths of RC beams and columns tested by various researchers with their theoretical strengths predicted by the proposed parameters and those evaluated based on provisions of RC codes.
Based on the test results, the stress-strain curve of normal-strength concrete (NSC) developed under strain gradient is derived using least-square method by minimising the errors between the theoretical axial load and moment and the respective measured values. Two formulas are developed to derive the flexural stress-strain curve, whose applicability is verified by comparing the predicted strength with those measured by other researchers.
Lastly, the application of the proposed stress-block parameters and stress-strain curve of NSC will be illustrated by developing some charts for flexural strength design of NSC beams and columns. The application will further be extended to develop strength-ductility charts for NSC beams and columns, which enable simultaneous design of strength and ductility. By adopting the proposed design charts, the flexural strength design, as well as that of the plastic hinge forming mechanism during extreme events, will be more accurate. The resulting design will be safer, more environmentally friendly and cost effective.published_or_final_version
Civil Engineering
Doctoral
Doctor of Philosophy
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Neela, Subhashini. "Flexural Behavior of Basalt FRP Bar Reinforced Concrete Members With and Without Polypropylene Fiber". University of Akron / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=akron1291084015.
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Araba, Almahdi M. A. A. "Behaviour of continuous concrete beams reinforced with hybrid GFRP/steel bars". Thesis, University of Bradford, 2017. http://hdl.handle.net/10454/16920.
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MACHADO, MARCELIA GOMES. "EXPERIMENTAL STUDY ON DUCTILITY OF REINFORCED CONCRETE BEAMS STRENGTHENED IN FLEXURE WITH CARBON FIBER COMPOSITES". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2004. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=5867@1.
Testo completoAbstract (sommario):
COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOREste trabalho experimental tem como objetivo estudar a ductilidade de vigas retangulares de concreto armado reforçadas à flexão utilizando compósitos com tecido de fibras de carbono. No estudo realizado são apresentados os conceitos clássicos de ductilidade e é proposta uma nova sistemática para obtenção do índice de ductilidade, baseada nas considerações da energia elástica e da energia inelástica. A ductilidade é determinada por meio de um índice energético, que se caracteriza como uma forma mais eficiente para a determinação e análise da ductilidade em elementos estruturais. O programa experimental consistiu no ensaio de sete vigas bi-apoiadas, sendo uma viga de referência e as demais reforçadas à flexão com tecido de fibras de carbono. Todas as vigas possuem as mesmas características mecânicas e geométricas e foram dimensionadas de modo a garantir a ruptura por flexão. A viga de referência, a primeira ensaiada, não foi reforçada e serviu para comparações de incremento de rigidez e resistência após a aplicação do reforço. As vigas reforçadas foram divididas em dois grupos. O grupo A é constituído de duas vigas, reforçadas inicialmente com uma e duas camadas de tecido de fibra de carbono. O grupo B é constituído por quatro vigas que foram reforçadas após um carregamento inicial. Neste grupo, duas vigas foram reforçadas com uma camada de tecido de fibra de carbono e as outras duas foram reforçadas com duas camadas de tecido de fibras de carbono, correspondendo à mesma área total de reforço das anteriores. Todas as vigas foram concretadas, instrumentadas e ensaiadas no Laboratório de Estruturas e Materiais da PUC-Rio. Os ensaios das vigas do grupo B foram realizados com as vigas pré-ensaiadas, reforçadas sob deformação constante e em seguida levadas à ruptura. A deformação foi mantida constante durante a aplicação e o período de cura do reforço. Os resultados obtidos em termos de carga, flecha, momento, curvatura, ductilidade energética e rotação plástica foram analisados. Os estudos realizados mostraram que o reforço com compósitos de fibras de carbono é uma técnica eficaz, que as vigas apresentam ductilidade adequada e que os índices energéticos propostos são adequados para este tipo de estudo.
The objective of this experimental work is to study the ductility of reinforced concrete beams strengthened in flexure using externally bonded carbon fiber fabric composites. This study presents the classic concepts of ductility and proposes a new systematic to obtain the ductility index, which is based on the considerations of elastic and inelastic energy. The ductility was determined by an energetic index, which has seen to be a more efficient method to establish and analyze the ductility of structural elements. The experimental program consisted of seven beams tests. One was used as a control beam without external reinforcement and the others were strengthened with carbon fibers in order to resist flexural load. All the beams had the same mechanical and geometrical characteristics and were designed to fail in flexure. The control beam was not strengthened and its purpose was to compare the stiffness increase and resistance after the strength. The strengthened beams were divided in two groups. Group A was constituted by two beams, initially strengthened by one and two layers of carbon fiber fabric. Group B was formed by four beams which were strengthened after the application of an initial load. In this group, two beams were strengthened by one layer of carbon fiber fabric and the other two were strengthened by two layers, which corresponded to the same area of the others. All the beams were cast, instrumented and tested in the Structural and Materials Laboratory at PUC-Rio. Group B tests were performed with the pretested beams strengthened under constant strain, and then loaded up to rupture. The strain was kept constant during the application and cure of the external reinforcement. The results obtained in terms of load, deflection, resistant moment, curvature, energetic ductility indexes and plastic rotation were analyzed. The study showed that the reinforcement using carbon fiber fabric composites is an efficient technique, the beams presented adequate ductility and the proposed energetic ductility indexes are consistent formulae for this kind of study.
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Pichardo, C., C. Pichardo, W. Tovar e V. I. Fernandez-Davila. "Evaluation of the curvature ductility ratio of a circular cross-section of concrete reinforced with GFRP bars". Institute of Physics Publishing, 2020. http://hdl.handle.net/10757/651796.
Testo completoAbstract (sommario):
The present study deals with the use of fiberglass reinforced polymer bars (GFRP) as a replacement for the common steel of a reinforced concrete circular pile, in order to avoid the corrosion of durability of reinforcing bars and thus improve them. The comparative analysis was carried out between a pile reinforced with GFRP and another with steel, where the ductility was evaluated by obtaining moment-curvature diagram. As a result, said idealized moment-curvature diagrams and ductility indices are presented, concluding the ductility of the section reinforced with GFRP in 20% more than that of steel.
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Bliuc, Radu Aerospace Civil & Mechanical Engineering Australian Defence Force Academy UNSW. "Particularities of the structural behaviour of reinforced high strength concrete slabs". Awarded by:University of New South Wales - Australian Defence Force Academy. School of Aerospace, Civil and Mechanical Engineering, 2004. http://handle.unsw.edu.au/1959.4/38749.
Testo completoAbstract (sommario):
The introduction of high strength concrete in construction demanded an assessment of the current methods of structural design. In the case of the slabs, the benefits brought about by concretes of higher strength could translate into design of slender sections. Theoretically these sections could be prone to excessive deflections. The flexural behaviour of such structural elements should be carefully assessed. The present thesis addresses a series of particular issues such as deflection at service loads, crack formation and development of tension stiffening and ductility. An experimental program on large-scale samples was conducted. Six one way and four two way slabs made of reinforced high strength concrete were tested under simulated and accurately measured equally distributed loads. Different loading stages were recorded. Crack formation, crack patterns and yield line disposition were observed. The main characteristics of concrete that influence the deflection behaviour were assessed based on collected data and on available literature results. Statistical methods were employed in order to refine empirical equations that help in the design of slabs. To improve the calculation of deflection of slabs a new equation for the effective moment of inertia was proposed. The new formula was integrated into a method of calculating deflection and verified against experimental results. Limits of the use of high strength concrete in slabs were investigated by means of a parametric study. This was designed to answer some questions as: which would be the most important characteristics of high-strength concrete that influence the design and up to what value of strength would the beneficial effect on deflection exhaust its effectiveness. Models based on the refined empirical equations for different concrete parameters were proposed. Another area that has been studied was the ductility of high strength concrete slabs. An analytical comparative study of the ductility of slabs reinforced with steel of different ductility class was conducted. Results were critically appraised and discussed.
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Adhikari, Sudeep. "Mechanical and Structural Characterization of Mini-Bar Reinforced Concrete Beams". University of Akron / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=akron1386682169.
Testo completo
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Eilers, Michael G. Thiagarajan Ganesh. "Ductility behavior of concrete flexural members reinforced with a hybrid combination of GFRP and mild steel". Diss., UMK access, 2006.
Cerca il testo completoAbstract (sommario):
Thesis (M.S.)--School of Computing and Engineering. University of Missouri--Kansas City, 2006."A thesis in civil engineering." Typescript. Advisor: Ganesh Thiagarajan. Vita. Title from "catalog record" of the print edition Description based on contents viewed Oct. 30, 2007. Includes bibliographical references (leaves 70-71). Online version of the print edition.
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Ali, Mir Mazher Carleton University Dissertation Engineering Civil and Environmental. "A new concept in achieving ductility in FRP reinforced concrete members; an analytical and experimental study". Ottawa, 1995.
Cerca il testo completo
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Mohamed, Nayera Ahmed Abdel-Raheem. "Strength and drift capacity of GFRP-reinforced concrete shear walls". Thèse, Université de Sherbrooke, 2013. http://hdl.handle.net/11143/6136.
Testo completoAbstract (sommario):
With the rise in constructing using FRP reinforcement, owing to corrosion problems in steel-reinforced structures, there is a need for a system to resist lateral loads induced from wind and earthquake loads. The present study addressed the applicability of reinforced-concrete shear walls totally reinforced with glass-fiber-reinforced polymer (GFRP) bars to attain reasonable strength and drift requirements as specified in different codes. Four large-scale shear walls - one reinforced with steel bars (as reference specimen) and three totally reinforced with GFRP bars - were constructed and tested to failure under quasi-static reversed cyclic lateral loading. The GFRP-reinforced walls had different aspect ratios covering the range of medium-rise walls. The reported test results clearly showed that properly designed and detailed GFRPreinforced walls could reach their flexural capacities with no strength degradation, and that shear, sliding shear, and anchorage failures were not major problems and could be effectively controlled. The results also showed recoverable and self-centering behavior up to allowable drift limits before moderate damage occurred and achieved a maximum drift meeting the limitation of most building codes. Acceptable levels of energy dissipation accompanied by relatively small residual forces, compared to the steel-reinforced shear wall, were observed. Finite element simulation was conducted and the analyses captured the main features of behavior. Interaction of flexural and shear deformations of the tested shear walls was investigated. It was found that relying on the diagonal transducers tended to overestimate shear distortions by 30% to 50%. Correcting the results based on the use of vertical transducers was assessed and found to produce consistent results. Decoupling the flexural and shear deformations was discussed. Using GFRP bars as elastic material gave uniform distribution of shear strains along the shear region, resulting in shear deformation ranging from 15 to 20% of total deformation. The yielding of the steel bars intensified the shear strains at the yielding location, causing significant degradation in shear deformation ranging from 2 to 40% of total deformation. The results obtained demonstrated significantly high utilization levels of such shear wall type, therefore, primary guidelines for seismic design of GFRP-reinforced shear wall in moderate earthquakes regions was presented, as no design guidelines for lateral load resistance for GFRP-reinforced walls are available in codes. The ultimate limit state was addressed by providing strength capacity that limit ductility demand to their safe flexural displacement capacity. The strength demands were derived from ground motion spectra using modification factors that depend on both the strength and energy absorption of the structure. Deformation capacity was derived by proposing new definitions for elastic (virtual yield) displacement and maximum allowable displacement. Strength modification factor was proposed based on the test results. The occurrence of "virtual plastic hinge" for GFRP-reinforced shear walls was described providing new definitions convenient with the behavior of the GFRP-reinforced shear walls. "Virtual plastic hinge" length was estimated based on observations and calculations. Subsequently, the experimental results were used to justify the proposed design procedure. The promising results could provide impetus for constructing shear walls reinforced with GFRP bars and constitute a step toward using GFRP reinforcement in such lateral-resisting systems.
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Broms, Carl Erik. "Concrete flat slabs and footings : Design method for punching and detailing for ductility". Doctoral thesis, KTH, Brobyggnad inkl stålbyggnad, 2005. http://innopac.lib.kth.se/search/.
Testo completoAbstract (sommario):
Thesis (Ph.D.)--Royal Institute of Technology (Stockholm, Sweden), 2005."ISRN KTH/BKN/B-80-SE." "Dept. of Civil and Architectural Engineering, Division of Structural Design and Bridges, Royal Institute of Technology, Stockholm. " Includes bibliographical references. Available from the Royal Institute of Technology (Sweden) Library as a .pdf document http://www.lib.kth.se/main/eng/
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Bower, Owen J. "Analytical Investigation into the Effect of Axial Restraint on the Stiffness and Ductility of Diagonally Reinforced Concrete Coupling Beams". University of Cincinnati / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1211065883.
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Tann, David Bohua. "Retrofitting of mechanically degraded concrete structures using fibre reinforced polymer composites". Thesis, University of South Wales, 2001. https://pure.southwales.ac.uk/en/studentthesis/retrofitting-of-mechanically-degraded-concrete-structures-using-fibre-reinforced-polymer-composites(efce1110-34e1-457d-8ec5-3ef5da026018).html.
Testo completoAbstract (sommario):
This research involves the study of the short term loaded behaviour of mechanically degraded reinforced concrete (RC) flexural elements, which are strengthened with fibre reinforced polymer (FRP) composites. The two main objectives have been: (a) to conduct a series of realistic tests, the results of which would be used to establish the design criteria, and (b) to carry out analytical modelling and hence develop a set of suitable design equations. It is expected that this work will contribute towards the establishment of definitive design guidelines for the strengthening of reinforced concrete structures using advanced fibre composites. The experimental study concentrated on the laboratory testing of 30 simply supported, and 4 two-span continuous full size RC beams, which were strengthened by either FRP plates or fabric sheets. The failure modes of these beams, at ultimate limit state, were examined and the influencing factors were identified. A premature and extremely brittle collapse mechanism was found to be the predominant type of failure for beams strengthened with a large area of FRP composites. A modified semi-empirical approach was presented for predicting the failure load of such over strengthened beams. Despite the lack of ductility in fibre composites, it was found that the FRP strengthened members would exhibit acceptable ductile characteristics, if they were designed to be under strengthened. A new design-based methodology for quantifying the deformability of FRP strengthened elements was proposed, and its difference to the conventional concept of ductility was discussed. The available techniques for ductility evaluation of FRP strengthened concrete members were reviewed and a suitable method was recommended for determining ductility level of FRP strengthened members. A non-linear material based analytical model was developed to simulate the flexural behaviour of the strengthened and control beams, the results were seen to match very well. The parametric study provided an insight into the effects of various factors including the mechanical properties and cross sectional area of FRP composites, on the failure modes and ductility characteristics of the strengthened beams. Based on the findings of the experimental and analytical studies, design equations in the BS 8110 format were developed, and design case studies have been carried out. It was concluded that fibre composites could effectively and safely strengthen mechanically degraded reinforced concrete structures if appropriately designed. The modes of failure and the degree of performance enhancement of FRP strengthened beams depend largely on the composite material properties as well as the original strength and stiffness of the RC structure. If the FRP strengthened elements were designed to be under-strengthened, then the premature and brittle failure mode could be prevented and ductile failure mode could be achieved. It was also found that existing steel reinforcement would always yield before the FRP composite reached the ultimate strength. Furthermore, a critical reinforcement ratio, above which FRP strengthening should not be carried out, was defined. It was concluded that FRP strengthening is most suitable for reinforced concrete floor slabs, bridge decks, flanged beams and other relatively lightly reinforced elements. The study also revealed that to avoid a brittle concrete failure, existing doubly reinforced members should not be strengthened by FRP composites.
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Osorio, Gomez Laura Isabel. "Behavior of synthetic fiber-reinforced concrete circular columns under cyclic flexure and constant axial load". Mémoire, Université de Sherbrooke, 2008. http://savoirs.usherbrooke.ca/handle/11143/1435.
Testo completoAbstract (sommario):
La ductilité et la capacité à dissiper de l'énergie sont deux qualités très importantes pour les éléments structuraux des structures situées dans les régions sismiques comme l'est du Canada. Soulignons que Montréal occupe la deuxieme place en ce qui a trait au risque sismique au Canada. De plus, la réduction des coûts de maintenance des infrastructures est un sujet d'intérêt pour les propriétaries alors que ces derniers doivent en tout temps garantir la sécurité des usagers. Or, le béton renforcé avec des fibres synthétiques semble être un matériau qui remplit ces caractéristiques. Pourtant, son utilisation est actuellement limitée aux éléments non structuraux ou structuraux mais non principaux. Afin de généraliser l'utilisation du béton fibre dans le domaine structural, il faut continuer à produire et à analyser des données expérimentales qui permettront de valider et d'améliorer les prescriptions de design et les modèles analytiques actuels pour la conception des éléments en béton armé avec des fibres dans les zones sismiques. Dans ce contexte, six poteaux circulaires à grande-échelle ont été testés sous une charge axiale constante (25% de Agf'c) et en flexion cyclique. Trois poteaux ont été confectionnés en béton normal (BN) et les trois autres en béton renforcé avec des fibres synthétiques (BRFS). La résistance à la compression du béton spécifiée à 28 jours pour les spécimens était de 30 MPa. Le volume de fibres synthétiques en polypropylène-polyéthylène utilisé a été de 1%. Les trois poteaux en BN étaient renforcés par une armature transversale constituée d'une spirale ayant un pas de 42, 75 et 100 mm respectivement. Ces trois spécimens ont été comparés avec des spécimens similaires en BRFS. Les résultats montrent que la présence des fibres synthétiques dans la matrice de béton améliore le comportement ductile et la capacité a dissiper de l'énergie des spécimens. Il a été observé que cette amélioration n'est pas directement proportionnelle à la quantité d'armature transversale. Toutefois, l'utilisation du béton fibre semble rendre possible une réduction de l'armature transversale tout en conservant un aussi bon sinon un meilleur comportement.
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Galin, Sanja. "Selection and Scaling of Seismic Excitations for Time-History Analysis of Reinforced Concrete Frame Buildings". Thesis, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/20657.
Testo completoAbstract (sommario):
Time history-analyses of building structures have been used for a quite long time for research at universities. Considering the advantage of time-history analysis relative to the equivalent static force method, the National Building of Canada and other modern building codes around the world require the use of time-history analysis in the design of specified types of buildings located in seismic regions. One of the main issues in the use of time-history analysis is related to the selection and scaling of the seismic excitations (i.e., accelerograms) to be compatible with the design spectrum for the location considered. Currently, both recorded (i.e., “real”) accelerograms and artificial accelerograms are used in the analyses.
The objective of this study is to determine the effects of the selection and scaling of seismic excitations on the response of reinforced concrete frame buildings. Three reinforced concrete frame buildings with heights of 4 storey, 10 storey and 16 storey, designed for Vancouver (high seismic zone) were used in this study. Five sets of seismic excitations were used in the analysis – one set of “real” accelerograms, and four sets of artificial accelerograms obtained by different methods. All sets were scaled to be compatible with the design spectrum for Vancouver. Both linear and nonlinear time history analyses were conducted on the buildings considered. Interstorey drifts and storey shear forces were used as response parameters.
The results from the linear analysis show that both the interstorey drifts and the shear forces are affected significantly by the type of the excitation set. Similarly, the effects of the type of the seismic excitations on the drifts from nonlinear analysis are substantial. On the other hand, the influence of the excitation sets on the storey shears from nonlinear analysis are quite small.
Based on the results from this study, sets of scaled real records are preferred for use in time-history analysis of building structures. If such records are not available, then sets of simulated accelerograms based on the regional seismic characteristics should be used.
47
Peña-Ramos, Carlos Enrique. "Three Dimensional Dynamic Response of Reinforced Concrete Bridges Under Spatially Varying Seismic Ground Motions". Diss., The University of Arizona, 2011. http://hdl.handle.net/10150/217064.
Testo completoAbstract (sommario):
A new methodology is proposed to perform nonlinear time domain analysis on three-dimensional reinforced concrete bridge structures subjected to spatially varying seismic ground motions. A stochastic algorithm is implemented to generate unique and correlated time history records under each bridge support to model the spatial variability effects of seismic wave components traveling in the longitudinal and transverse direction of the bridge. Three-dimensional finite element models of highway bridges with variable geometry are considered where the nonlinear response is concentrated at bidirectional plastic hinges located at the pier end zones. The ductility demand at each pier is determined from the bidirectional rotations occurring at the plastic hinges during the seismic response evaluation of the bridge models. Variability of the soil characteristics along the length of the bridge is addressed by enforcing soil response spectrum compatibility of the generated time history records and of the dynamic stiffness properties of the spring sets modeling soil rigidity at the soil-foundation interface at each support location. The results on pier ductility demand values show that their magnitude depends on the type of soil under the pier supports, the pier location and the overall length and geometry of the bridge structure. Maximum ductility demand values were found to occur in piers supported on soft soils and located around the mid span of long multi-span bridges. The results also show that pier ductility demand values in the transverse direction of the bridge can be significantly different than the values in the longitudinal direction and in some instances, the maximum value occurs in the transverse direction. Moreover, results also show that ignoring the effects of spatial variability of the seismic excitation, the pier ductility demand can be severely underestimated. Finally, results show that increasing the vertical acceleration component in the seismic wave will generate an increase in the pier axial loads, which will reduce the ductility range of the pier plastic zones. As result, even though the increase in pier ductility demand associated with the increase in the vertical acceleration component was found to be relatively small, the number piers exhibiting significant structural damage increased.
48
Yilmaz, Taner. "Seismic Response Of Multi-span Highway Bridges With Two-column Reinforced Concrete Bents Including Foundation And Column Flexibility". Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12610191/index.pdf.
Testo completoAbstract (sommario):
Seismic design of highway bridges has improved as a result of the experience gained from large earthquakes of the last thirty years. Ductility demand and reserved capacity are extremely important response measures used in new bridge designs to assess target damage levels. However, the application of practical design approaches specified in bridge design codes is not well-defined for bridges over flexible foundations. Within the scope of this research, thirty two bridge models having varying column aspect ratio, amount of column longitudinal reinforcement and foundation flexibility parameters are investigated through a series of analyses such as response spectrum analysis and inelastic time-history analysis under &ldquosafety evaluation earthquake&rdquo
hazard level with a return period of 1000 years, and push-over analysis. Using the results of analyses, seismic response of the investigated bridges are identified with several measures such as displacement capacity over demand ratio, global displacement ductility demand, and response modification factor, along with maximum concrete and steel strains of columns. A correlation between concrete and steel strains and seismic response measure values is constructed to estimate damage levels with commonly used response measures. The findings of this research revealed that global displacement ductility demand is not a favorable response measure for assessing damage levels. On the other hand, displacement capacity over demand ratios can be suggested for estimation of damage levels especially where foundation flexibility effects are extensive as system yielding is not taken into consideration.
49
Hinzen, Marcus, e Wolfgang Brameshuber. "Improvement of Serviceability and Strength of Textile Reinforced Concrete by using Short Fibres". Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2009. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1244046356375-03273.
Testo completoAbstract (sommario):
Nowadays, thin-walled load bearing structures can be realised using textile reinforced concrete (BRAMESHUBER and RILEM TC 201-TRC [1]). The required tensile strength is achieved by embedding several layers of textile. By means of the laminating technique the number of textile layers that can be included into the concrete could be increased. To further increase the first crack stress and the ductility as well as to optimize the crack development, fine grained concrete mixes with short fibres can be used. By a schematic stress-strain curve the demands on short fibres are defined. Within the scope of this study, short fibres made of glass, carbon, aramid and polyvinyl alcohol are investigated in terms of their ability to fit these requirements. On the basis of these results, the development of hybrid fibre mixes to achieve the best mechanical properties is described. Additionally, a conventional FRC with one fibre type is introduced. Finally, the fresh and hardened concrete properties as well as the influence of short fibres on the load bearing behaviour of textile reinforced concrete are discussed.
50
Tuken, Ahmet. "Quantifying Seismic Design Criteria For Concrete Buildings". Phd thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/12604907/index.pdf.
Testo completoAbstract (sommario):
The amount of total and relative sway of a framed or a composite (frame-shear wall) building is of utmost importance in assessing the seismic resistance of the building. Therefore, the design engineer must calculate the sway profile of the building several times during the design process.
However, it is not a simple task to calculate the sway of a three-dimensional structure. Of course, computer programs can do the job, but developing the three-dimensional model becomes necessary, which is obviously tedious and time consuming.
An easy to apply analytical method is developed, which enables the determination of sway profiles of framed and composite buildings subject to seismic loading. Various framed and composite three-dimensional buildings subject to lateral seismic loads are solved by SAP2000 and the proposed analytical method. The sway profiles are compared and found to be in very good agreement. In most cases, the amount of error involved is less than 5 %.
The analytical method is applied to determine sway magnitudes at any desired elevation of the building, the relative sway between two consecutive floors, the slope at any desired point along the height and the curvature distribution of the building from foundation to roof level.
After sway and sway-related properties are known, the requirements of the Turkish Earthquake Code can be evaluated and / or checked.
By using the analytical method, the amount of shear walls necessary to satisfy Turkish Earthquake Code requirements are determined. Thus, a vital design question has been answered, which up till present time, could only be met by rough empirical guidelines.
A mathematical derivation is presented to satisfy the strength requirement of a three-dimensional composite building subject to seismic loading. Thus, the occurrence of shear failure before moment failure in the building is securely avoided.
A design procedure is developed to satisfy the stiffness requirement of composite buildings subject to lateral seismic loading. Some useful tools, such as executable user-friendly programs written by using &ldquoBorland Delphi&rdquo
, have been developed to make the analysis and design easy for the engineer. A method is also developed to satisfy the ductility requirement of composite buildings subject to lateral seismic loading based on a plastic analysis. The commonly accepted sway ductility of &
#956
&
#916
=5 has been used and successful seismic energy dissipation is thus obtained.