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Author: Wilmar Leonardo Cortés Puentes
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Squat reinforced concrete shear walls are stiff structural elements incorporated in buildings and other structures and are capable of resisting large seismic demands. However, when not properly designed, they are prone to shear-related brittle failure. To improve the seismic behaviour of these structural elements, a retrofitting bracing system incorporating superelastic Shape Memory Alloys (SMAs) was developed. Superelastic Shape Memory Alloys (SMAs) are smart materials with the ability to sustain and recover large pseudo-plastic deformations while dissipating energy. The SMA bracing system consists of tension-only SMA links coupled with rigid steel elements. The SMA links were designed to sustain and recover the elongation experienced by the bracing system, while the steel elements were designed to sustain negligible elastic elongations. The SMA bracing system was installed on third-scale, 2000 mm {604} 2000 mm, shear walls, which were tested to failure under incremental reverse cyclic loading. The experimental results demonstrated that the tension-only SMA braces improve the seismic response of squat reinforced concrete walls. The retrofitted walls experienced higher strength, greater energy dissipation, and less permanent deformation. The re-centering properties of the SMA contributed to the reduction of pinching in the hysteretic response due mainly to the clamping action of the SMA bracings while recovering their original length. The walls were numerically simulated with the nonlinear finite element program VecTor2. The numerical simulations accurately captured the hysteretic response of both the original and the retrofitted walls. A parametric study was conducted to assess the effect of axial loading and size of the SMA braces.
Author: Wilmar Leonardo Cortés Puentes
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Squat reinforced concrete shear walls are stiff structural elements incorporated in buildings and other structures and are capable of resisting large seismic demands. However, when not properly designed, they are prone to shear-related brittle failure. To improve the seismic behaviour of these structural elements, a retrofitting bracing system incorporating superelastic Shape Memory Alloys (SMAs) was developed. Superelastic Shape Memory Alloys (SMAs) are smart materials with the ability to sustain and recover large pseudo-plastic deformations while dissipating energy. The SMA bracing system consists of tension-only SMA links coupled with rigid steel elements. The SMA links were designed to sustain and recover the elongation experienced by the bracing system, while the steel elements were designed to sustain negligible elastic elongations. The SMA bracing system was installed on third-scale, 2000 mm {604} 2000 mm, shear walls, which were tested to failure under incremental reverse cyclic loading. The experimental results demonstrated that the tension-only SMA braces improve the seismic response of squat reinforced concrete walls. The retrofitted walls experienced higher strength, greater energy dissipation, and less permanent deformation. The re-centering properties of the SMA contributed to the reduction of pinching in the hysteretic response due mainly to the clamping action of the SMA bracings while recovering their original length. The walls were numerically simulated with the nonlinear finite element program VecTor2. The numerical simulations accurately captured the hysteretic response of both the original and the retrofitted walls. A parametric study was conducted to assess the effect of axial loading and size of the SMA braces.
Author: Marina Maciel
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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This thesis investigates the seismic performance of hybrid Shape Memory Alloy (SMA)-steel reinforced concrete shear walls containing Nickel-Titanium (Ni-Ti) superelastic SMA as alternative reinforcement in the plastic hinge region. This wall system permits self-centering with high levels of energy dissipation and significant reduction of permanent deformations. Conventional steel-reinforced concrete shear walls were designed for a prototype 10-storey office building, assuming seismic design scenarios in eastern and western Canada. Equivalent hybrid SMA-steel reinforced concrete shear walls were defined following the designed cross-sections of the conventional walls. Full-scale, 2-D finite element models of the walls were developed and subjected to nonlinear, static and time-history analyses, employing historical and simulated ground motion records for the latter. The numerical results confirmed the superior self-centering capacity of the hybrid SMA-steel reinforced walls, showing potential to optimize the seismic performance of reinforced concrete buildings, particularly in high seismic zones, by controlling residual deformations and reducing damage.
Author: Michael Armando Soto Rojas
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Shape Memory Alloys (SMAs) and High-Performance Fiber Reinforced Concretes (HPFRCs) are innovative materials that provide an opportunity to improve the post-earthquake state of reinforced concrete structures, while achieving the design objective. The combination of these two materials lead to self-centering with improved damage tolerance. In this research, previously tested, Superelastic-Shape Memory Alloy (SE-SMA) and typical-steel reinforced concrete shear walls are repaired and tested under the same simulated seismic loading. The repairing method involved the removal of the heavily damaged concrete in the plastic hinge zone, replacement of ruptured and buckled steel reinforcement, and casting of Engineered Cementitious Composite (ECC) where the previous concrete was removed. The numerical modelling and experimental testing of the repair technique highlight that the brittle behavior of concrete in tension and its deformation incompatibility with reinforcing steel bars, and yielding of steel reinforcement are suppressed by establishing a composite system that integrates the self-centering phenomenon of SE-SMA and the distinctive ductility properties of ECC.
Author:
Publisher:
ISBN:
Category : Juvenile Nonfiction
Languages : en
Pages : 74
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Book Description
This renamed version of the former Uniform code for building conservation guidelines for retrofitting unreinforced masonry bearing wall buildings, reinforced concrete and reinforced masonry buildings, wood frame residential buildings, and concrete with masonry infill buildings.
Author:
Publisher: FEMA
ISBN:
Category : Buildings
Languages : en
Pages : 572
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Author: Vishesh Dr Vikas
Publisher:
ISBN:
Category : Electronic dissertations
Languages : en
Pages : 0
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Many reinforced concrete (RC) buildings built prior to implementation of seismic design provisions in the 1970s are non-ductile and are at risk of excessive damage or even collapse during a major earthquake. In this dissertation study, a low damage retrofit scheme for non-code performing RC shear walls was investigated. In the retrofit scheme, traditional monolithic RC shear walls were converted into rocking walls by introducing a cold joint at the wall foundation interface and by adding external post-tensioning. Two retrofitted rectangular RC shear walls were tested in laboratory to investigate the proposed retrofit scheme. The retrofitted shear walls showed minimized damage, improved self-centering but lower energy dissipation capacity in comparison to the benchmark shear wall. A novel scheme using Ultra-High-Performance Concrete (UHPC) was proposed and investigated using laboratory testing and finite element (FE) simulation to anchor external PT elements to existing foundation in the retrofitted shear walls. Four anchorage specimens, that were designed to anchor 2/5th of the maximum PT force expected in the retrofitted shear walls, were subjected to laboratory testing. 3D FE models were calibrated based on the measured response and were used to investigate the proposed anchorage scheme at full-scale. The current code provisions to limit residual drift and predict critical concrete strains in precast rocking shear walls were examined based on published results. The provisions on residual drift were found to be satisfactory for hybrid rocking walls. Two code-conforming rectangular hybrid rocking shear walls were tested in the laboratory to provide improve alternative for predicting plastic hinge length in rocking walls, which is critical in estimating critical concrete strain.Laboratory testing of precast rocking shear walls has been limited to rectangular cross section. This dissertation addresses the gap in literature by testing a T-shaped precast rocking shear wall. The test specimen was designed in accordance with current design guidelines, at one-third scale of a prototype wall and tested under multi-directional loading up to 1.50% drift. Test observations showed damage to be limited at the rocking corners. The measured residual drift was lower than 0.25% and the measured energy dissipation ratio exceeded the prescribed limit of 12.5%.
Author: Mena Morcos
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Superelastic Shape Memory Alloys (SE-SMA) have provided a viable novel alternative to conventional steel reinforcement for the construction of earthquake-resilient structures. The capacity of SE-SMA to recover from high strains upon unloading provides the mechanism required to develop self-centering smart structures. Shear walls are routinely used seismic force resisting systems in concrete construction, which makes them qualified candidates for the application of SE-SMA longitudinal reinforcement. The integration of SE-SMA into a hybrid-reinforced flexural system is expected to rectify inelastic lateral displacements and economize the cost of post-disaster repair. A large-scale slender superelastic Nitinol-reinforced concrete shear wall was tested numerically and experimentally, along with a control specimen, under quasi-static load reversals to assess seismic performance. The results of the SE-SMA wall demonstrated efficient dissipation of seismic energy to achieve high drift recovery and easily repairable damage, suggesting a low probability of demolition and substantial savings over the lifetime of the structure.
Author: Hamed Layssi
Publisher:
ISBN:
Category :
Languages : en
Pages :
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"This research describes an experimental and analytical investigation to evaluate the seismic performance of poorly designed and detailed reinforced concrete (RC) flexural shear walls both in their as-built conditions and after being retrofitted. Older shear walls have several deficiencies which make them vulnerable in case of moderate to severe earthquakes. Full-scale shear wall specimens were constructed and tested under reversed cyclic loading. Two different techniques were chosen to retrofit the deficient walls in order to improve the overall performance. A retrofit technique using Carbon Fibre Reinforced Polymer (CFRP), having minimum intervention, was studied to determine the seismic performance. A more labour-intensive repair technique, including the addition of a reinforced concrete jacket in the critical region (location of potential plastic hinging and lap splices of vertical bars) together with CFRP wrapping was also studied. The responses obtained from experiments were used to develop behavioural models, capable of representing the global responses of the walls, as well as critical failure modes observed in the experiments. These models provide useful tools for predicting the complete reversed cyclic loading responses of shear walls. The analytical models were used to predict the responses of a deficient prototype wall-frame structure in its original condition as well as after retrofit, subjected to different seismic hazard levels. This study enabled an evaluation of the performance of the prototype structure to determine the effectiveness of retrofit and repair measures." --
Author: James Paterson
Publisher:
ISBN:
Category :
Languages : en
Pages : 246
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"The four shear wall specimens were tested under reversed cyclic loading. Two of these walls had a lap splice in the longitudinal steel at the base of the wall and the other two had a lap splice 600 mm from the base of the wall. One of each of these specimens was tested in the 'as-built' condition and the other two were retrofit prior to testing. The test results show that the retrofit strategies were successful in improving the ductility and energy dissipation of the shear walls." --
Author: Hossam El-Sokkary
Publisher:
ISBN:
Category :
Languages : en
Pages :
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