Ductile Shear Walls Research Articles

Modelling of mid-rise concrete shear walls reinforced with superelastic shape memory alloys: Nonlinear analysis

The response of hybrid Shape Memory Alloy (SMA)-steel reinforced concrete shear walls containing Nickel-Titanium superelastic SMA as alternative reinforcement in the plastic hinge region was investigated using nonlinear finite element modelling. The hybrid wall system promotes self-centering and significant reduction of permanent deformations. Two types of conventional steel-reinforced concrete shear walls were designed for a prototype 10-storey office building according to the current Canadian concrete design standard, assuming two distinct seismic design scenarios. A moderately ductile shear wall was designed for a moderate seismic zone in eastern Canada, whereas a ductile shear wall was designed for a high seismic zone in western Canada. Equivalent, hybrid SMA-steel reinforced concrete shear walls were defined following the design of the two conventional shear walls, in terms of geometry and reinforcement layout. Full-scale, two-dimensional finite element models were developed to assess the pushover and hysteretic responses of the walls. Similarities in wall cross-section and yield force capacity of the steel and SMA reinforcement permitted a comparison between the walls, including strength, stiffness, self-centering, and energy dissipation capacities. The results indicate similar lateral strength and displacement capacities, and superior restoring capacity of the SMA-reinforced walls in comparison to the steel-reinforced walls. Furthermore, a preliminary study was conducted to investigate the effect of the SMA-bar length in the ductile wall due to concentration of damage near the base of the wall. Lengths corresponding to approximately 50% and 20% of the original SMA length were considered. Based on the analyses, a satisfactory response could be achieved with shorter SMA reinforcing bars, which reduces the quantity of SMA reinforcement without significant loss in self-centering capacity.

Effect of Ductile Shear Wall Ratio and Cross-Section Configuration on Seismic Behavior of Reinforced Concrete Masonry Shear Wall Buildings

Reinforced masonry buildings typically have a load-bearing wall structural system. Thus, the reinforced masonry shear walls must be capable of resisting both vertical forces from gravity loads and lateral forces from seismic and wind loads. Typically, because the walls are subjected to high axial loads, ensuring the ductile response becomes challenging. A possible solution at the component level would be the utilization of walls with confined ends (i.e., walls with boundary elements) to reduce the compression zone and increase the compression strain. Another solution, which is at the system level, is the introduction of a hybrid structural system composed of two types of walls: (1) ductile walls with or without boundary elements to resist the lateral forces and part of vertical forces, and (2) gravity walls that resist only axial loads. This paper proposes a combination of both solutions (i.e., at component and system levels). Additionally, it utilizes a series of linear and nonlinear static and dynamic analyses to evaluate and quantify the effect of cross-section configuration and ductile shear wall area to total floor area (i.e., ductile shear wall ratio) on the seismic response of masonry buildings. The numerical analyses are performed by a macro model detailed to simulate the nonlinear response. The primary objective is to recommend a range of ductile shear wall ratios that optimize the design and overall performance. The study targets mid-rise and high-rise masonry buildings located in regions with moderate seismic hazard. The findings emphasize that utilizing the ductile walls with boundary elements in the proposed hybrid structural system resulted in major favorable enhancements in the structural response and optimization of the design. In addition, the results demonstrate the possibility of vertically reducing and terminating the specially detailed boundary elements, thus promoting ductile reinforced concrete masonry shear wall buildings as a competitive building system.

Seismic performance and height limits of ductile reinforced masonry shear wall buildings with boundary elements

The National Building Code of Canada, NBCC-15 has recently added a new Seismic Force Resisting System (SFRS) category, ductile shear walls, for Reinforced Masonry (RM) buildings. Although it was assigned a higher ductility-related force modification factor compared to that of moderately ductile walls, NBCC-15 assigned the same building height limits for the ductile and moderately ductile RM walls. This study aims to assess (i.e. numerically) the seismic performance and collapse capacity of ductile RM buildings, having heights exceeding the code limit, built using ductile RM shear walls with boundary elements as the SFRS. The main objective is to propose height limits based on solid and objective seismic performance acceptance criteria. In this regard, six archetype buildings with varying heights are designed according to CSA S304-14 with ductile RM structural walls having confined boundary elements. The reference buildings are located in two regions representing the high and moderate seismicity levels of NBCC-15. The seismic performance is evaluated using nonlinear pseudo-static pushover and Incremental Dynamic Analyses (IDA). The quantification of seismic performance and collapse capacity is executed using the procedure outlined in FEMA P695. This research study contributes to the understanding of the seismic performance and collapse capacity of ductile RM shear wall buildings with boundary elements. It provides practical design recommendations to enhance the overall system performance. In addition, the study proposes a simple, yet efficient nonlinear numerical macro-modeling approach for RM shear walls. Finally, based on the findings of this study, it is suggested to assign a 70 m limit for the height of buildings in moderate seismicity regions and a 50 m limit for the buildings in regions with high seismic hazard.

Optimization of Shear Walls with the Combination of Genetic Algorithm and Artificial Neural Networks

Objectives: In this study, the cost of a reinforced concrete structures containing medium ductile shear walls, which were similar in plan and height, has been optimized by the combination of Genetic Algorithm and Artificial Neural Networks. Methods: The selected structure was a 13-storey building with four types of shear walls, which was supposed to be built in Tehran. The costs estimated for this research included the cost of concrete and reinforcement used in the walls. By changing the measure of shear walls, some steel rods, and cement altered. Results: Accordingly, the ranges of shear walls were recognized as the independent variables and the concrete and steel rod results were dependent variables. Beams, columns and the width of the shear walls were the same on all types. The prices of concrete and support of shear walls have been used for back propagation neural network training. Before optimization by neural network in the section of neural network training, the Genetic Algorithm steel bar function is defined. The steel bar function included the costs of concrete and steel bars used in shear walls. Conclusion: Afterwards, the best combination of four types of shear walls was selected using Genetic Algorithm. Finally, the optimum shear wall area to the plan area of regular concrete buildings with medium ductile shear walls is presented.

Seismic Response Evaluation of Ductile Reinforced Concrete Block Structural Walls. II: Displacement and Performance–Based Design Parameters

AbstractA typical seismically designed reinforced masonry building is composed of structural walls, constructed following the same prescriptive detailing requirements corresponding to a code classified seismic force resisting system (SFRS). However, due to architectural requirements (i.e. to allow for requirements such as openings and wall intersections), some of these walls might have the same overall aspect ratio but differ in their cross-section configurations. The companion paper presented the experimental results and force-based seismic design parameters for walls that fall under the Canadian Standards Association (CSA) ductile shear walls and the Masonry Standards Joint Committee (MSJC) special-reinforced walls SFRS classifications. The current paper utilizes the experimental results to extract key displacement-based seismic design parameters, including wall yield and ultimate curvatures, wall displacements at yield and at the post-yield stages, stiffness degradation, period elongation, and equivale...

Seismic Response Evaluation of Ductile Reinforced Concrete Block Structural Walls. I: Experimental Results and Force-Based Design Parameters

The reported experimental study documents the performance of six fully grouted reinforced concrete block structural walls tested under quasistatic cyclic loading. The walls fall under the ductileshear walls and the special reinforced masonry walls seismic force resisting system (SFRS) classification of the Canadian and U.S. standards, respectively. The test matrix consisted of one rectangular, one flanged, and two slab-coupled walls, all with an overall aspect ratio of 1.4. In addition, two rectangular walls, representing the individual components of the slab-coupled wall systems, were tested to quantify the wall slab coupling effects. In addition to discussing the experimental results, the study also presents key force-based seismic design (FBSD) parameters, such as the wall lateral load capacity, plastic hinge length, wall failure modes, and displacement ductility capacities. Moreover, the effects of wall cross-sectional configuration and slab coupling on the cyclic response and deformation capabilities of the walls are discussed. In general, the yield and ultimate loads were found to be accurately predicted using the Canadian Standards Association (CSA) S304-14 and Masonry Standards Joint Committee (MSJC) formulations. The wall experimental displacement ductility values (calculated at 20% strength degradation) ranged between 5.4 and 7.6, whereas the idealized displacement ductility values at the same strength degradation level ranged between 3.4 and 5.4. The analysis results reported in the paper highlight the fact that walls designed and detailed within the same SFRS classification possess significantly different FBSD parameters. The results also indicate that slab coupling, although not recognized as a wall coupling mechanism in the current editions of the CSA and MSJC, can have significant influences on the seismic response of ductile/special reinforced masonry wall systems.

Seismic demand of moderately ductile reinforced concrete shear walls subjected to high-frequency ground motions

A parametric study was performed to examine the seismic behaviour of moderately ductile (MD) reinforced concrete shear walls designed according to Canadian code provisions, including National Building Code of Canada (NBCC) 2010 and Canadian Standards Association (CSA) 23.3-04, when subjected to typical high-frequency eastern North America earthquakes. The numerical models were experimentally validated based on large specimens shaking table test results. The results obtained following the code response spectrum procedure were compared with the results from inelastic response history analyses to investigate the effect of higher modes on seismic force demands. The results indicate that current code provisions for MD shear walls need to be modified. A new base shear factor and shear force design envelop are proposed to evaluate the seismic shear force demand more realistically. This study also recommends that the current CSA 23.3-04 requirements for ductile shear walls for bending moments could be applied to constrain the location of inelastic flexural deformations at the base of MD shear walls.

SEISMIC PERFORMANCE EVALUATION OF WOOD SHEAR WALLS COMBINED VARIOUS LOAD-DISPLACEMENT RELATIONSHIPS

The main objective of this study is to confirm a current seismic performance procedure of wood house with various load-displacement relationships. As the seismic performance procedure of Japanese wood house, the amount of the standard value of shear strength has been used widely. The standard value of shear strength is defined as the smallest value calculated from four indexes. The main problem of this method is the applicability of multiple of the standard values combining various load-displacement relationships. In this study, the applicability is confirmed through the collapse analysis procedure, based on Incremental Dynamic Analysis (IDA). The same suite of 22 pairs of scaled bi-directional historical ground motion records (44records total) were used as input to the IDAs. Based on the results obtained, the following conclusions can be drawn mainly: 1) It is difficult for ductile shear wall to evaluate using the same procedure for maintaining the same performance of seismic safety as the shear wall of plywood and bracing. 2) Ductile shear wall which does not reach the limit state in displacement shall be ignored.

Performance of prefabricated high strength welded wire grids in ductile concrete shear wall boundary elements

AbstractThe performance of a new proprietary concrete reinforcement product, BauMesh, when used as confinement reinforcement in ductile concrete shear walls is discussed.Large material and labor savings are achieved when concrete shear walls are reinforced with these new high strength welded wire ladders positioned at close spacing (3 o.c.) along the length of the longitudinal reinforcement to ensure a non‐brittle ductile response to violent earthquake generated cyclic forces.Design, quality control during manufacture, installation, and the observed performance of a 17‐story San Francisco ductile shear wall building during the Loma Prieta earthquake are discussed.

The analysis and design of and the evaluation of design actions for reinforced concrete ductile shear wall structures

A comprehensive review of the state of the art in the design of earthquake resisting ductile structural walls is presented. The material has been compiled from the technical literature, the deliberations within the New Zealand National Society for Earthquake Engineering and research efforts at the University of Canterbury. The paper attempts a classification of structural types and elaborates on the hierarchy in energy dissipation. After a review of available analysis procedures, including modelling assumptions, a detailed description of capacity design procedures for both cantilever and coupled shear wall structures is given. The primary purpose of capacity design is to evaluate the critical design actions which can be used in the proportioning and reinforcing of wall actions which can be used in the proportioning and reinforcing of wall sections. An approach to the estimation of structural deformation is suggested. To satisfy the ductility demands imposed by the largest expected earthquake, detailed design and detailing recommendations are given and the application of some of these is presented in an appendix.

A Critical Review of the Seismic Design Provisions for Ductile Shear Walls of the Canadian Code and Commentary

The 1975 Canadian Building Code for the design of reinforced concrete shear wall buildings in high seismic risk areas includes provisions that are new and significant. This paper critically examines some of these provisions, especially as they apply to cantilever shear walls. Clarifications in the definitions of curvature, member, and system ductilities are attempted. The relationship between curvature and system ductility is examined. Code provisions on allowable shear stress in the wall in the plastic hinge region and the provisions for the classification of the walls are discussed. Attention of the designer is drawn to some aspects of the code and the commentary that may result in structures of doubtful safety.