Showing papers on "Shear wall published in 2002"

Seismic Behavior of Squat Reinforced Concrete Shear Walls

Abstract: The behavior of reinforced concrete walls that exhibit the shear mode of failure is studied, through the results of an experimental program that included the test of 26 full-scale specimens subjected to cyclic horizontal displacements of increasing amplitude. Test parameters were the aspect ratio of the walls, the amount of vertical and horizontal distributed reinforcement, and the compressive strength of concrete. The results include the cracking shear strength, the maximum shear strength, the drifts associated to these loads and the drift associated to a collapse limit state for each of the specimens tested. Conclusions are drawn concerning the deformation capacity, the energy absorption, the dissipation characteristics and the strength deterioration after maximum strength shown by the walls and the influence of vertical distributed reinforcement on the seismic behavior of walls. [DOI: 10.1193/1.1490353]

Performance-Based Seismic Design of Wood Framed Buildings

Abstract: An important advancement in structural engineering in recent years has been the development of performance-based seismic design. However, its application to engineered wood framed buildings remains largely unexplored. This paper discusses the application of performance-based seismic design to wood framed buildings through a direct-displacement methodology. In the first part of the paper, limitations of the current force-based seismic design procedure for wood framed buildings are outlined. Thereafter, the fundamentals of displacement-based seismic design are presented along with a description of the system parameters required for its application. For the purpose of evaluating these parameters for wood framed buildings, a simple numerical model capable of predicting the cyclic response and energy dissipation characteristics of wood shear walls under general quasi-static cyclic loading is presented. The generalization of this model to three-dimensional wood framed structures is also discussed. As an application example, the displacement-based seismic design of a simple one-story shear wall building is presented. In turn, this design approach is validated by nonlinear dynamic time-history analyses using earthquake records representative of the hazard levels that were associated with the design performance levels.

Behavior of Three-Dimensional Reinforced ConcreteShear Walls

Abstract: Results from two large-scale flanged shear walls tested under static cyclic displacements are presented. The objectives of the tests were to provide insight into the behavior of shear walls under cyclic displacements, and more importantly, to provide data to help corroborate constitutive models for concrete exposed to arbitrary loading conditions. The results indicated that the presence of an axial load, although relatively small, and the stiffness of flange walls have a significant effect on the strength, ductility, and failure mechanisms of the shear walls. Finite element analyses using provisional constitutive models are also provided to show that the procedures employed are stable, compliant, and provide reasonably accurate simulations of behavior. The analyses presented also indicated that two-dimensional analyses capture main features of behavior, but three-dimensional analyses are required to capture some important second-order mechanisms.

Performance-Based Optimization for Strut-Tie Modeling of Structural Concrete

Abstract: Conventional trial-and-error methods are not efficient in developing appropriate strut-and-tie models in complex structural concrete members. This paper describes a performance-based optimization ~PBO! technique for automatically producing optimal strut- and-tie models for the design and detailing of structural concrete. The PBO algorithm utilizes the finite element method as a modeling and analytical tool. Developing strut-and-tie models in structural concrete is treated as an optimal topology design problem of continuum structures. The optimal strut-and-tie model that idealizes the load transfer mechanism in cracked structural concrete is generated by gradually removing regions that are ineffective in carrying loads from a structural concrete member based on overall stiffness performance criteria. A performance index is derived for evaluating the performance of strut-and-tie systems in an optimization process. Fundamental concepts underlying the development of strut-and-tie models are introduced. Design examples of a low-rise concrete shearwall with openings and a bridge pier are presented to demonstrate the validity and effectiveness of the PBO technique as a rational and reliable design tool for structural concrete.

Cyclic behaviour of deep reinforced concrete coupling beams

Abstract: Six half-scale models of reinforced concrete coupling beams with span/depth ratios ≤ 2·0 were tested under reversed cyclic load by a newly developed test method that can accurately simulate the boundary conditions of coupling beams in coupled shear wall structures. Five of them were conventionally reinforced and one was diagonally reinforced. Span/depth ratio and reinforcement layout were the main structural variables studied. Test results revealed that the deep conventionally reinforced coupling beams behaved quite differently from the ordinary beams in frame structures. Generally, shear failure was more likely to occur. Moreover, the additional longitudinal reinforcement bars (those placed near the centroidal axis) could contribute significantly to bending strength and therefore lead to an increase in shear demand. Nevertheless, the measured drift ratios of the conventionally reinforced coupling beams still reached 3·6–5·7%, which are not small for deep coupling beams. On the other hand, it was found th...

Reliability-based Seismic Design of Wood Shear Walls

Abstract: This paper reports on work, conducted under Task 1.5.3 (Reliability Studies) of the CUREE-Caltech Woodframe Project, with the objective of developing a risk-based methodology for seismic design of shear walls. Along with diaphragms, shear walls are primary lateral force resisting components in woodframe structures. The methodology developed herein is based on reliability principles as well as emerging performance-based concepts for seismic design. The specific subobjectives of Task 1.5.3 were: (1) to conduct a sequence of sensitivity studies to evaluate the contributions of various sources of uncertainty to shear wall performance as predicted using the CASHEW program (developed in another task of the project); (2) to evaluate the variabilities in, and thereby statistically characterize, the peak response obtained using a suite of ordinary ground motion records taken to characterize the seismic hazard in southern California; and (3) to develop a risk-based procedure for performance-based design of wood she...

A new modelling strategy for the behaviour of shear walls under dynamic loading

Abstract: A new simplified modelling strategy to simulate the non-linear behaviour of reinforced concrete shear walls under dynamic loading is presented. The equivalent reinforced concrete (ERC) model is derived from the framework method and uses lattice meshes for concrete and reinforcement bars and uniaxial constitutive laws based on continuum damage mechanics and plasticity. Results show the capacity of the model to analyse structures having different slenderness and boundary conditions. For low reinforcement ratios however, results are sensitive to the angle formed by the diagonals of the concrete lattice and the horizontal bars. The method is compared with the shear multi-layered beam model that uses Timoshenko multi-layered 2D beam elements and biaxial constitutive laws. Comparisons for both models with experimental results of two research programs (one organized by NUPEC and the other by COGEMA and EDF) are provided. ERC is a simplified method that intends to save computer time and allows parametrical studies. Copyright © 2002 John Wiley & Sons, Ltd.

Soil-Foundation-Structure Interaction (Shallow Foundations)

Abstract: This research focuses on strip footing foundations supporting shear wall type building structures. Understanding the nonlinear behavior of shallow building foundations under large amplitude loading is an important aspect of performance-based design. The 1997 Federal Emergency Management Agency NEHRP Guidelines for the seismic retrofit of buildings (NEHRP 1997a, 1997b) and the associated Applied Technology Council document (ATC 40) (ATC 1996) discuss alternative design issues associated with the response of shear walls when subjected to lateral

Drift design of steel‐frame shear‐wall systems for tall buildings

Abstract: Drift design methods based on resizing algorithms are presented to control lateral displacements of steel-frame shear-wall systems for tall buildings. Three algorithms for resizing of structural members of the steel-frame shear-wall systems are derived by formulating the drift design process into an optimization problem that minimizes lateral displacement of the system without changing the weight of a structure. During the drift design process, cost-effective displacement participation factors obtained by the energy method are used to determine the amount of material to be modified instead of calculating sensitivity coefficients. The overall structural design model with the drift design method for the steel-frame shear-wall systems is proposed and applied to the structural design of three examples. As demonstrated in the examples, the lateral displacement and interstorey drift of a frame shear-wall system can be effectively designed by the drift design method without the time-consuming trial-and-error process. Copyright © 2002 John Wiley & Sons, Ltd.

Validation of seismic design parameters for wood- frame shearwall systems

Abstract: A methodology for assessment of seismic design parameters for a wood-frame shearwall system is developed, consisting of a test program of shearwalls and the application of nonlinear time history analyses to a four-storey wood-frame building that was designed to resist the seismic requirements for Vancouver, British Columbia. Analyses employed 22 selected earthquake accelerograms that were scaled upwards until an ultimate peak ground acceleration (Au) was reached where the shearwall reached a "near-collapse" state. The 22 values of Au were found to be greater than the "design" peak ground acceleration, indicating the adequacy of the current design procedures for the particular shearwalls investigated. The influence of gypsum wallboard on the behaviour of the shearwalls was also evaluated, and a new force modification factor "R" for walls composed of a mixture of wood-based and gypsum panels was proposed. The effect of flexibility of floor diaphragms was considered separately for a symmetric building and wa...

Strengthening URM with GFRP Composites and Ductile Connections

Abstract: Research on the use of fiber-reinforced polymer (FRP) composites for strengthening of unreinforced or inadequately reinforced hollow concrete masonry is covered in this paper. Quasi-static shear wall tests were conducted on unreinforced concrete masonry specimens that had been strengthened with unidirectional glass fiber strips applied to the surface of the masonry using a two-part epoxy to form a surface-bonded GFRP composite. The strips were strategically placed to improve both flexural and shear strength in the in-plane direction. The GFRP composite system was combined with conventional structural steel and reinforcing steel connections that were designed to yield before the composite ruptured, resulting in a ductile failure mode under cyclic testing. The drift capacities of the tested specimens ranged from 0.6% to 1.7%.

Ductile Anchorage for Connecting FRP Strengthening of Under-Reinforced Masonry Buildings

Abstract: Fiber-reinforced polymer ~FRP! composites have been examined as a convenient and cost-effective means of strengthening unreinforced masonry structures. Seismic design in the United States is almost entirely based on the assumption that the structural system provides a ductile failure mode. FRP strengthened masonry walls inherently have brittle failure modes due to the nature of the strength- ening system. The concept explored in this article is the introduction of ductility using a hybrid strengthening system. This involves the placement of structural steel or reinforcing steel at critical locations in the lateral force resisting system. This article presents the testing and analysis of a ductile structural steel connection that can be used to strengthen the connection of FRP strengthened shear walls to the foundation. The connection also increases energy dissipation. Results indicate that a ductile failure mode can be attained when the connection is designed to yield prior to the failure of the FRP strengthening.

Timber shear walls with large openings: experimental and numerical prediction of the structural behaviour

Abstract: A numerical model based on the finite element method is presented for prediction of the cyclic response of wood frame structures. The model predicts the cyclic response of shear walls. Nonlinear phenomena are assumed to be concentrated in the connections that are modelled through elements linking the structural elements including the posts, beams, and sheathing panels. Identification of model parameters relies on tests on individual connections. Connection tests on different nail lengths were conducted under monotonic and cyclic lateral loads. Based on the results from past studies that indicate the pull-through failure is an important failure mode in common nail connections with lumber and oriented strand board (OSB), washers were considered as a means to reinforce the connection. The influence of reinforced nailing on the static and dynamic performance of full-size wood frame shear walls with large openings, sheathed with OSB panels, was evaluated experimentally. Combinations of parameters were studied,...

Seismic assessment of transfer plate high rise buildings

Abstract: The assessment of structural performance of transfer structures under potential seismic actions is presented. Various seismic assessment methodologies are used, with particular emphasis on the accurate modelling of the higher mode effects and the potential development of a soft storey effect in the mega-columns below the transfer plate (TP) level. Those methods include response spectrum analysis (RSA), manual calculation, pushover analysis (POA) and equivalent static load analysis (ESA). The capabilities and limitations of each method are highlighted. The paper aims, firstly, to determine the appropriate seismic assessment methodology for transfer structures using these different approaches, all of which can be undertaken with the resources generally available in a design office. Secondly, the paper highlights and discusses factors influencing the response behaviour of transfer structures, and finally provides a general indication of their seismic vulnerability. The representative Hong Kong building considered in this paper utilises a structural system with coupled shear walls and moment resisting portal-frames, above and below the TP, respectively. By adopting the wind load profile stipulated in the Code of Practice on Wind Effects: Hong Kong-1983, all the structural members are sized and detailed according to the British Standards BS8110 and the current local practices. The seismic displacement demand for the structure, when built on either rock or deep soil sites, was determined in a companion paper. The lateral load-displacement characteristic of the building, determined herein from manual calculation, has indicated that the poor ductility (brittle nature) of the mega-columns, due mainly to the high level of axial pre-compression as found from the analysis, cannot be effectively alleviated solely by increasing the quantity of confinement stirrups. The interstorey drift demands at lower and upper zones caused by seismic actions are found to be substantially higher than those arising from wind loads. The mega-columns supporting the TP and the coupling beams at higher zones are identified to be the most vulnerable components under seismic actions.

Testing of coupling beams with equal end rotations maintained and local joint deformation allowed

Abstract: The strength and ductility of the coupling beams in coupled shear walls can significantly affect the nonlinear behaviour and earthquake resistance of the whole building structure. However, although extensive testing of coupling beams has been performed, the boundary conditions—that the rotations at the two ends of a coupling beam are equal and that local deformation occurs at the beam–wall joints, which could have substantial influence on the test results—have not been correctly simulated. Herein, a new method of testing reinforced concrete coupling beams that ensures equal rotations at the ends of the beam specimen and takes into account local deformation at the beam–wall joints is developed. The method has been successfully applied to test typical reinforced concrete coupling beams with relatively small span/depth ratios and proven to be suitable for studying the post-peak behaviour and failure characteristics of short coupling beams. Test results obtained so far indicate that reinforced concrete coupli...

The effects of axial deformation and axial force on vibration characteristics of tall buildings

Abstract: A tall building comprising frames and shear walls coupled together is idealized as a shear–flexure cantilever through the continuum approach. The effects of axial deformation as well as axial force in the frames are considered and incorporated in the formulation of the governing equations. Numerical examples are solved through the Galerkin method and the results compared with finite element solutions. The study indicates that the effect of axial deformation in the frame should be considered for tall and/or slender buildings while the effect of axial force in the column should be included for buildings with soft-storeys resulting from the termination of core walls in the lower portion of the building. Copyright © 2002 John Wiley & Sons, Ltd.

Simplified analysis of asymmetric high-rise structures with cores

Abstract: A simplified elastic hand-method of analysis for asymmetric multi-bent structures with cores subjected to horizontal loading is presented. The structures may consist of combinations of framed structures such as coupled walls, rigid frames and braced frames with planar and non-planar shear walls. Results for structures that are uniform with height compare closely with results from stiffness matrix analyses. The method is developed from coupled-wall deflection theory which is expressed in non-dimensional structural parameters. It accounts for bending deformations in all individual members, axial deformations in the vertical members as well as torsion and warping in nonplanar walls. A closed solution of coupled differential equations for deflection and rotation gives the deflected shape along the height of the building from which all internal forces can be obtained. The proposed method of analysis offers a relatively simple and rapid means of comparing the deformations and internal forces of different stability systems for a proposed tall building in the preliminary stages of the design. The derivation of equations for analysis shown in this paper are for unisymmetric stability systems only, but the method is also applicable to general asymmetric structures with cores. Copyright © 2002 John Wiley & Sons, Ltd.

Buckling analysis of buildings braced by frameworks, shear walls and cores

Abstract: A simple hand method is presented for the three-dimensional stability analysis of buildings braced by frameworks, coupled shear walls, shear walls and cores. Sway buckling behaviour is characterized by three types of deformation: the full-height ‘local’ bending of the individual columns, wall sections, shear walls and cores, the full-height ‘global’ bending of the frameworks and coupled shear walls, which is associated with the axial deformations of the column and wall sections, and the shear deformation of the frameworks and coupled shear walls. Based on the stiffnesses associated with these three types of deformation, a closed formula is derived for the calculation of the sway critical load. An analogy between bending and torsion is used to carry out the pure torsional buckling analysis. The interaction between the bending and shear modes as well as among the basic buckling modes (sway in the principal directions and torsion) are taken into account. A worked example with step-by-step instructions shows the easy use of the method. The results of a comprehensive accuracy analysis involving 73 multistorey buildings are also given together with comparisons with other analytical methods. Copyright © 2002 John Wiley & Sons, Ltd.

Sensitivity study of the finite element model for wood-framed shear walls

Abstract: A sensitivity study was performed with a nonlinear elastic finite element model for monotonie analyses of wood-framed shear walls. The objective was to provide information about simplifying a model of wood-framed shear walls with no significant loss in accuracy. The simplifications concern features such as slips in joints between frame members, slips in hold-down connections, and bearing between adjacent sheathing panels. The results from analyses of a shear wall with an opening of window shape show that the effect of constraint by the bearing between sheathing panels and slips in frame joints on the overall stiffness of the wall is limited. Thus, there are great possibilities for reducing the calculation time by not taking these phenomena into account, avoiding an excessive number of degrees of freedom and iterations. The influence of the simplifications on the distribution of vertical reaction forces along the wall is more significant. Furthermore, if each simplification is introduced separately, the effect on the overall stiffness is greater. The difference, however, is less than 10%. The failing pattern of the nail connections is also clearly influenced by the simplifications when they are introduced separately. The results from the analyses show that slips in frame joints can be sufficiently represented by those in connection with the opening.

Dynamic response and seismic testing of CMU walls rehabilitated with composite material applied to only one side

Abstract: This project consisted of an analytical investigation and seismic shake table testing of unreinforced masonry bearing and shear walls. The analytical investigation consisted of pseudo-static and dynamic analyses of existing unreinforced concrete masonry unit (CMU) walls. The shake table testing programme consisted of uniaxial and triaxial time history testing of unreinforced masonry walls retrofitted with fibreglass composite material applied as an overlay to only one side of the walls. This paper discusses the dynamic behaviour of the analytical and physical models, the performance of the overlay composite material system, recommendations on using the system for seismic rehabilitation and retrofit of unreinforced masonry walls, and comparisons of the analytical and seismic test results.

Behavior of repaired cyclically loaded shearwalls

Abstract: This paper describes a test program in which large-scale, 3-D wall systems were severely damaged under reversed cyclic loading conditions, and were then repaired and reloaded. The main aim was to present data that will be useful in calibration studies. The paper also shows that a proper repair can largely restore the strength, stiffness, and energy dissipation characteristics of a severely damaged wall. Lastly, it is shown that a proper account of previous loading and damage is essential if one is aiming to accurately model the response of a repaired wall.

Structural reinforcement system for reinforcing openings formed in structures

Abstract: In accordance with the present invention, there is provided a structural reinforcement system for reinforcing and securing an opening in a building/structure. The movable panel is further adapted to augment the shear stiffness of the building/structure when the panel is disposed in a closed position, such that the overall wall with the structural reinforcement system in accordance with the present invention has shear stiffness equal to or better than a uniform shear wall.

Unsteady bed shear stresses induced by navigation: Laboratory observations

Abstract: Time-dependent bed shear stresses induced by the passage of a barge tow have been measured with hot film shear stress sensors in a 1:25 scale model. Conditions typical of those observed for Upper Mississippi River navigation traffic were simulated in the experimental facility. Two sets of experiments were carried out: the first set consisted of simultaneous shear stress measurements at different locations for a variety of flow depths and boat operating conditions, providing space-time distributions of ensemble averaged wall shear stresses. The second set included a large number of realizations gathered for one particular flow condition at a single position, allowing analysis of the time evolution of the turbulence characteristics (i.e., standard deviation) of the bed shear stresses. The results of the first set of experiments show that for all the experimental conditions the basic patterns of the shear stress are similar, with two regions of high shear stress associated with the passage of the bow and the...

Seismic Performance of Wall-stud Shear Walls

Abstract: Sixteenth International Specialty Conference on Cold-Formed Steel Structures Orlando, Florida USA, October 17-18, 2002 Seismic Performance of Wall-Stud Shear Walls Ludovic A. Fulop!, Dan Dubina2 The ever-increasing need for housing generated the search for new and innovative building methods to increase speed, efficiency and enhance quality, one direction being the use of light steel profiles as load bearing elements and different materials for cladding. Wind and seismic behavior of these structures is influenced by the hysteretic characteristics of the shear wall panels. In this paper a review of actual research in the field and results of a full-scale shear test program on wall panels are presented. Based on tests, a numerical equivalent model for hysteretic behavior of wall panels working in shear was built to be used in 3D dynamic nonlinear analysis of cold-formed steel framed buildings.

Base isolation structure for building

Abstract: PROBLEM TO BE SOLVED: To provide a rational base isolation structure for a building with a superior degree of freedom in design and aseismatic performance. SOLUTION: In the multistory or skyscraper building 1, a lower layer building 2 is formed by a rigid frame comprising columns 2a and beams 2b. An upper layer building 3 is supported on base isolation devices 7 arranged on heads of the columns 2a. An intermediate story base isolation layer 8 is formed in the building 1. The upper layer building 3 comprises a mega-structure layer 4 and a core-wall structure layer 5. The mega-structure layer 4 is composed of mega-beams 9 with a large beam depth and columns 10 connected via the mega-beams 9. The core-wall structure layer 5 constructed in its upper part is composed of an outer circumferential rigid structure 11 comprising outer circumferential columns 11a and outer circumferential beams 11b, and core-walls 12 arranged so as to surround its center part and comprising a series of multi- story shear wall continuous from a lowermost layer to an uppermost layer of the core-wall structure layer 5. COPYRIGHT: (C)2004,JPO