Showing papers on "Shear wall published in 1994"

Closure of "Finite Element Modeling of Concrete Expansion and Confinement"

Abstract: The lateral expansion of concrete subjected to compression (i.e., the Poisson effect) is shown to be a significant factor influencing the behavior of reinforced concrete elements in tension‐compression states in which the principal tensile strain is relatively small. A method is presented by which concrete lateral expansion can be incorporated into a nonlinear finite element algorithm. The formulations presented presume the use of a secant‐stiffness‐based solution procedure, involving the concept of material prestrains. Material behavior models are described for nonlinear concrete expansion, strength reduction due to transverse cracking, strength enhancement due to confinement, and pre‐ and post ultimate stress‐strain response. The accuracy of the formulations are examined through finite element analyses of a number of shear panels and shear walls previously tested. It is shown that the inclusion of concrete lateral expansion can, in some cases, significantly alter the computed response of an element or s...

Simple Method for Approximate Analysis of Framed Tube Structures

Abstract: Framed tube structures are particularly suitable for tall buildings. They act primarily like cantilevered box beams and since they generally have much larger lateral dimensions than the internal shear wall cores, they are more effective in resisting the overturning moments of the lateral loads. However, due to flexural and shear flexibilities of the frame members, the basic beam bending actions of the framed tubes are complicated by the occurrence of shear lag, which could significantly affect the stress distributions in the frame panels and reduce the lateral stiffnesses of the structures. In this paper, a simple hand‐calculation method is proposed for approximate analysis of framed tube structures with the shear lag effects taken into account. This method is suitable for quick evaluations during the preliminary design stage and can provide a better understanding of the effects of various parameters on the overall structural behavior. Numerical examples are given to demonstrate the ease of application an...

Analysis of Free Vibrations of Tall Buildings

Abstract: An analysis of free vibrations of tall buildings, such as frame, shear-wall, and frame-shear-wall structures, is proposed and discussed in this paper. Frame buildings are treated as shear beams with varying cross sections, the solutions of mode shapes of such buildings are expressed in Bessel’s functions, and the parameter of determining the fundamental period can be found from a figure provided in the paper. Based on the fact that the shear deformation and bending deformation are all considered for shear wall and frame-shear-wall structures, the formulas for calculating free vibrations of such structures are presented. It is very simple and convenient to apply these formulas to dynamic analysis of tall buildings. The measurement results and statistical analysis of frame, shear-wall, and frame-shear-wall structures in sites, and three examples of determining free vibrations of structures are also given in this paper. The examples show that the effect of shear deformation on the first natural frequency is not significant, but the effect of that on higher natural frequencies may not be neglected.

New Methodology for Seismic Design of RC Shear Walls

Abstract: An analytical approach to determine the need to provide transverse reinforcement at boundaries of reinforced concrete structural walls with rectangular, T‐shaped, or barbell‐shaped cross sections is presented. By relating the expected displacement demands on the building system to the local deformations imposed on the wall cross section, the magnitude and distribution of wall normal strain is determined. The primary variables affecting the wall‐strain distribution are found to be the ratio of wall cross‐sectional area to the floor‐plan area, the wall aspect ratio and configuration, the wall axial load, and the wall‐reinforcement ratios. Based on the computed wall‐strain distribution, required transverse steel for concrete confinement and length of the wall cross section requiring concrete confinement is computed. The wall‐strain distribution is also used to evaluate required transverse reinforcement to restrain buckling of longitudinal reinforcement. The validity of the proposed analytical approach is dem...

Postbuckling behavior of steel-plate shear walls under cyclic loads. authors' closure

Abstract: In current design practice the capacity of a steel‐plate shear wall is limited to the elastic buckling strength of its plate panels. This practice results not only in a conservative design, but also in an undesirable one where the columns yield and may buckle before the plate reaches a fraction of its capacity. Plate buckling is not synonymous with failure and if the plate is adequately supported along its boundaries, as in the case of the shear wall, the postbuckling strength can be several times the theoretical buckling strength. Furthermore, due to the unavoidable out‐of‐plane imperfections, no change in the plate behavior will be observed at the theoretically calculated buckling load. Although the post‐buckling behavior of plates under monotonic loads has been under investigation for more than half a century, this behavior under cyclic loading has not been investigated until recently. One test was conducted at the University of Alberta and 10 tests were conducted at the University of Maine. In this pa...

Concrete structures in earthquake regions : design and analysis

Abstract: 1. An overview of earthquake resistant design 2. Choice of earthquake resisting system 3. Analysis for earthquake effects 4. Behaviour of reinforced concrete under cyclic loading 5. Design of frames, shear walls and diaphragms 6. codes of practice 7. Codes of practice 8. Soils and foundations 9. Base isolation 10. Bridges, dams and industrial chimneys

Earthquake Response of Flat-Slab Buildings

Abstract: System identification, three-dimensional linear dynamic analysis, and code-specified conventional equivalent static techniques are used to evaluate the response of a nine-story flat-slab building during the Loma Prieta Calif., earthquake of 1989. Four different models are used in the finite-element–based dynamic and static analyses. The system identification results on natural frequencies, mode shapes, and interstory drifts are used to validate the four analytical models. It is found that the model with a 30% live load included in the mass computation, a 2/3 reduction in the stiffness of slabs, and 30% reduction in stiffness of columns and shearwalls appears to give a reasonable overall approximation of the measured response. The eccentricity of the central shearwall core in the east-west direction promoted torsional response. Both the dynamic analysis and system identification results indicate that the shearwall kept the drift level at the central core within the code limit. At the east and west end of the building, where frame action dominates, the drift level reached the code limit. The horizontal forces were mostly resisted by the core shearwalls. The base shear coefficient in the north-south direction determined from the dynamic analysis was close to that of the equivalent static procedure. In the east-west direction, however, the dynamic base shear coefficient was twice as much.

Low-Rise Shear Wall Ultimate Drift Limits

Abstract: Drift limits for low aspect ratio reinforced concrete shear walls are investigated by reviewing the open literature for appropriate experimental data. Based on the geometry of structures d...

Narrow Plywood Shear Panels

Abstract: The Uniform Building Code allows plywood sheathed narrow shear panels having a height‐to‐width ratio of 3.5‐to‐one (UBC Table 25‐I) to be used as lateral force resisting elements. Previous laboratory testing has concentrated on panels having a height‐to‐width ratio of one‐to‐one. This paper presents some results from the testing of plywood shear panels with a height‐to‐width ratio of two‐to‐one. Three panels were tested; each was configured to model a different construction scenario. The panels were subjected to fully reversed cyclic pseudo‐static loads. Comparison of the results from the three panels indicate that the tie‐down anchors must be installed with careful attention to bolt tightening sequence and torque in order to better resist lateral displacements in an earthquake. Vertical dead loads were found to reduce uplift of the panel which, in turn, reduces lateral displacements resulting from panel rotation. Decreased shear values for plywood shear walls subjected to cyclic loading and addi...

Composite Walls as Shear Elements in Tall Structures

Abstract: This paper describes a system of composite walling that can be used as a lateral load resisting system in tall structures. The composite walling comprises two skins of profiled steel sheeting with an infill of concrete. The steel sheeting acts as a permanent form obviating the need for temporary shuttering and false work and acts as reinforcement once the concrete has hardened. In tall buildings the in-plane loads are transmitted via the structural floors and frame to the walls. The behaviour of the wall under in-plane loading is, therefore, important for the analysis of building sway. Analytical models for the shear stiffness of the composite wall are presented and compared with the finite element analysis.

Mode coupling in the torsional—flexural buckling of regular multistorey buildings

Abstract: An analogy is established between the mode coupling of columns under concentrated end forces and those subjected to uniformly distributed axial forces. It is demonstrated that the cubic equation derived for the mode coupling of columns under end forces can be used directly for the more practical case of cantilevers under uniformly distributed axial load. Simple closed-form formulae and design tables are given for the torsional—flexural buckling of cantilevers. These formulae can be used directly for the spatial stability analysis of core supported regular multistorey buildings. A numerical example is provided to show the step-by-step procedure to be followed in practical structural design for stability. The results of a series of tests on small-scale multistorey building models are presented. The loadbearing system of the models consists of columns, shear walls and support cores. The results indicate that the contribution of the columns to the lateral and warping stiffness of the support system may be of considerable magnitude. The more sensitive the structure is to torsion, the greater the effect of the columns.

Investigation of framed shearwall behaviour with neural networks

Abstract: To date, concrete structure modelling has involved the development of mathematical models of concrete structure behaviour derived from human observation of and reasoning with, experimental data. An alternative, discussed in this Paper, is to use a computation and knowledge representation paradigm, called neural networks, developed by researchers in connectionism (a sub-jeld of artificial intelligence) to model concrete structure behaviour. m e main benefits in using a neural-network approach are that all behaviour can be represented within a unified environment of a neural network and the network is built directly from experimental data using the self-organizing capabilities of the neural network, i.e. the network is presented with the experimental data and learns the relationships between stresses and strains. Such a strategy has important implications for modelling the behaviour of modern, complex concrete structures. In this Paper, the behaviour of reinforced concrete framed shearwalls is modelled with...

Shear wall ultimate drift limits

Abstract: Drift limits for reinforced-concrete shear walls are investigated by reviewing the open literature for appropriate experimental data Drift values at ultimate are determined for walls with aspect ratios ranging up to a maximum of 353 and undergoing different types of lateral loading (cyclic static, monotonic static, and dynamic) Based on the geometry of actual nuclear power plant structures exclusive of containments and concerns regarding their response during seismic (ie,cyclic) loading, data are obtained from pertinent references for which the wall aspect ratio is less than or equal to approximately 1, and for which testing is cyclic in nature (typically displacement controlled) In particular, lateral deflections at ultimate load, and at points in the softening region beyond ultimate for which the load has dropped to 90, 80, 70, 60, and 50 percent of its ultimate value, are obtained and converted to drift information The statistical nature of the data is also investigated These data are shown to be lognormally distributed, and an analysis of variance is performed The use of statistics to estimate Probability of Failure for a shear wall structure is illustrated

Cyclic behaviour of connecting beams in reinforced concrete slit shear walls.

Abstract: The connecting beams in slit shear walls are generally much shorter than those in ordinary coupled shear walls and may therefore behave quite differently. In order to investigate the shear behaviour of such short connecting beams, two series of shear tests, one on monotonic behaviour and the other on cyclic behaviour, were carried out. Altogether, 24 specimens were tested. The results of the monotonic shear tests have been reported in an earlier paper. This paper presents some additional information on the ductility of the beams as revealed by the monotonic shear tests, and the results of the cyclic shear tests. From the cyclic shear tests, the cracking and failure characteristics, reinforcement stress distribution, stiffness and strength degradations, ductility and damping capacity of the connecting beams are studied. The results are useful for evaluating the seismic performance of reinforced concrete slit shear walls. (A)

In-place shear wall testing method and apparatus

Abstract: A method and apparatus for the in-place testing of the shear strength of a rectangular area of a wall. The method includes affixing a first shoe to an upper corner of a rectangular area of the wall and a second shoe to the lower opposite corner of this rectangular area. A strut is placed between the two shoes and its length is increased or decreased and measurements are made along the vertical, the horizontal and the diagonal as the length of the strut is changed. Preferably this is done with a hydraulic cylinder. The shoes have holes along a vertical side and a horizontal side and several brackets may be affixed at preferred locations to the sole and a stud at the bottom corner and to the plate and a stud at the top corner. A length adjusting strut is affixed between these attached plates and preferably rests on curved surfaces on each shoe.

Accurate Estimation of Interface Shear Stresses in Composite Masonry Walls

Abstract: A composite masonry wall consists of a concrete‐block wythe, a clay‐brick wythe and a cavity (i.e., collar joint) between the two wythes that is filled with mortar or grout. The in‐plane loads on a composite wall due to gravity and/ or wind are generally applied on the block wythe and can produce large interface shear stresses in the collar joint. The composite action of the wall is ensured only if these shear stresses are less than the shear strength of the interfaces. A refined finite element procedure based on interface shear stiffness and considering stress singularity, which can accurately predict collar‐joint interface shear stresses in composite masonry walls, is proposed in this paper. This paper shows that there is no need to consider reduced shear stiffness for the interface elements. Additionally, accurate shear stresses at a collar‐joint interface can be obtained for discontinuously applied loads by disregarding stresses in the two elements closest to the point‐of‐stress singularity. Use of th...

Macroelement Model for Shear Wall Analysis

Abstract: An efficient modeling scheme for static and dynamic analysis of reinforced concrete shear walls in the inelastic range is presented. The macroelement model of the shear wall is composed of an elastic spring to model axial deformations, two inelastic rotational springs at the ends of the element to model flexure and an inelastic shear spring.

Assessment of cross-tie performance in bridge pier walls. final report

Abstract: Following the 1989 Loma Prieta earthquake, the California Department of Transportation intensified its efforts to verify and, if necessary, upgrade the seismic design of the structural components of highway bridges. The very early design procedures of pier walls assumed that these structural components behave as shear walls subjected to equivalent static loading. Lateral loads in the direction of the weak axis (flexural) of such walls were not considered in the design. As a result of this assumption, the pre-1971 pier wall design used relatively small reinforcement ratios in both the vertical and horizontal directions. The current design of bridge pier walls has employed clear measures to improve the seismic performance of pier walls, specifically in the weak direction, such as increasing the steel ratios of the vertical and the horizontal reinforcements, placing the horizontal reinforcement on the outside of the vertical bars, and extending the vertical bars into the foundation, thereby eliminating the need for lap splices. In addition, cross-ties have uniformly been distributed along the wall height to improve their flexural strength and ductility in the weak direction. The present study intended, specifically, to examine a range of cross-tie provisions with the objective of establishing whether existing standards are unnecessarily conservative and, if so, what level of confinement would be acceptable. In addition, two different ratios of the vertical steel reinforcement representing average and upper design limits in current Caltrans specifications were investigated. A computer program was developed to estimate both the pier wall ductility and strength. Furthermore, the current design method used by Caltrans designers was assessed. The calculated results were compared with the experimental findings, and recommendations for improved design procedures were devised.

Double splice plate hollow wall

Abstract: The present invention belongs to a member of wall body of building masonry structure system and a change of building method and its multifunctional application Its wall body member mainly is a trough-shaped small building plate prefabricated with concrete Said invention uses a double butt method and a specially-designed connecting through-hole and its several selectable combination modes to economically make the above-mentioned trough-shaped small building plates form the required hollow wall bodies with different functions, such as shear wall, bearing wall, fill wall and enclosing wall, etc It not only retains all advantages of existent block building, but also has the highest compression-resisting, shear-resisting and stretch-proofing capacities, and has the high construction efficiency and multifunctional property

Shear wall experiments and design in Japan

Abstract: This paper summarizes the results of recent survey studies on the available experimental data bases and design codes/standards for reinforced concrete (RC) shear wall structures in Japan. Information related to the seismic design of RC reactor buildings and containment structures was emphasized in the survey. The seismic requirements for concrete structures, particularly those related to shear strength design, are outlined. Detailed descriptions are presented on the development of Japanese shear wall equations, design requirements for containment structures, and ductility requirements.

Strut-Tie Model Design of Disturbed Regions in Concrete Structures

Abstract: The design of disturbed (highly non-linear behavior) regions in concrete structures is illustrated using strut-tie approach. The use of this approach assisted with interactive computer graphics is illustrated with two design examples, a single sided corbel and a pierced shear wall. The strut-tie approach is shown to be instrumental in understanding the function of both concrete and steel reinforcement.

Computational structural engineering for practice

Abstract: Topics include: Frame Structures Analysis and Design of Steel Structures Nonlinear Analysis of Reinforced Concrete Structures Analysis of Concrete Pavements Reinforced Concrete Structures Masonry Structures Shear Wall Structures Geotechnical Engineering and the Simulation of Flow Around Buildings.