Showing papers on "Shear wall published in 1996"

Design of Concrete Structures with Stress Fields

Abstract: 1 Introduction and Theoretical Basis.- 1.1 Introductory Remarks.- 1.2 Fundamentals of the Theory of Plasticity.- 1.2.1 Material Behaviour.- 1.2.2 Limit State Theorems of the Theory of Plasticity.- (a) Static Solution.- (b) Kinematic Solution.- 1.3 Engineering Methods.- 2 Stress Fields for Simple Structures.- 2.1 Introduction.- 2.2 Beams with Rectangular Cross-Section Subjected to Bending and Shear.- 2.2.1 Deep Beams, Concentrated Loads.- 2.2.2 Deep Beams, Several Concentrated Loads.- 2.2.3 Deep Beams, Distributed Load.- 2.2.4 Beams with Medium Slenderness Ratio, Concentrated Loads.- 2.3 Beams with I-Cross-Section Subjected to Bending and Shear.- 2.3.1 Slender Beams, Concentrated Loads.- 2.3.2 Slender Beams, Distributed Load.- 2.3.3 General Case, Practical Design.- 2.3.4 Beams of Variable Depth.- 2.3.5 Compression Flange.- 2.3.6 Tension Flange.- 2.4 Members Subjected to Torsion and Combined Action.- 2.4.1 Introduction.- 2.4.2 Warping Torsion (Open Cross-Sections).- 2.4.3 Circulatory Torsion.- 2.4.4 Circulatory Torsion Combined with Bending and Shear.- 2.5 Brackets.- 2.6 Coupling Beams.- 2.7 Joints of Frames.- 2.7.1 Corner Joint, Compression on the Inside.- 2.7.2 Corner Joint, Tension on the Inside.- 2.7.3 Joints of Frames with Three Connecting Beams.- 2.7.4 Joints of Frames with Four Connecting Beams.- 2.8 Beams with Sudden Changes in Cross-Section.- 2.9 Walls.- 2.9.1 Shear Walls.- 2.9.2 Diaphragms.- 2.10 Three-Dimensional Example.- 3 Material Strengths and other Properties.- 3.1 Reinforcing Steel.- 3.2 Concrete.- 3.2.1 Uniaxial Stress State.- 3.2.2 Three-Dimensional Stress State.- 3.2.3 Concrete with Imposed Cracks.- 3.2.4 Cracks: Aggregate Interlock.- 3.3 Force Transfer Reinforcement - Concrete.- 3.3.1 Anchorage of Reinforcing Bars.- 3.3.2 Splices of Reinforcement.- 3.3.3 Force Deviations.- 4 Additional Considerations for the Development of Stress Fields.- 4.1 Remarks on Plastic Design Applied to Reinforced Concrete.- 4.1.1 Behavior of Statically Indeterminate Beams.- 4.1.2 Selection of the Inclination of the Compression Field in the Web of Beams.- 4.1.3 Redistribution of Internal Forces and Ductility Requirements.- 4.2 Procedure for Developing Stress Fields.- 4.2.1 Introduction.- 4.2.2 Spreading of Force in a Wall Element Loaded in Tension.- 4.2.3 Spreading of Force in a Wall Element Loaded in Compression.- 4.2.4 Further Cases.- 4.3 Impaired Strength through Wide Cracks.- 4.4 Stress Distribution in Highly Stressed Compression Zones.- 4.4.1 Introduction.- 4.4.2 Stress Fields for Beam-Columns.- 4.5 Prestressed Beams.- 4.5.1 Beam with straight cable.- 4.5.2 Beam with curved cable.- 4.5.3 Anchorage zone of pretensioned beams.- 4.5.4 Unbonded prestressed beams.- 5 Plane Stress, Plate and Shell Elements.- 5.1 Plane Stress Elements.- 5.2 Slab Elements.- 5.3 Shell Elements.- 6 Outlook: Computer Programs.- References.

On the behavior and ductility of reinforced concrete coupling beams of shear walls

Abstract: The results of an experimental program on coupling beams subjected to cyclic loading are presented. Ten specimens, scaled down to 1:2, with five different reinforcement layouts and two different shear ratios (equal to α s = 0.50 and 0.83) have been tested. An attempt is made to classify the performance of the specimens according to the ductility they exhibited. The validity of various ductility criteria is also discussed.

Shear Resistance of Gypsum-Sheathed Light-Gauge Steel Stud Walls

Abstract: This paper presents detailed results on the shear behavior of 2.44 m by 2.44 m light-gauge steel stud walls for three different shear resisting systems: framed walls with 20 gauge flat strap X-bracing on the face—type A; framed walls with 12.5 mm (1/2 in.) single-ply gypsum wallboard on the back and 12.5 mm (1/2 in.) single-ply gypsum sheathing board on the face—type B; and framed walls with 12.5 mm (1/2 in.) single-ply gypsum wallboard on the back, 12.5 mm (1/2 in.) gypsum sheathing board on the face, and 20 gauge flat strap X-bracing on face—type C. The steel framing used in these tests is typical of framing used in residential construction. The behavior of the type A walls was governed by the yield strength of the straps with practically no resistance provided by flexure in the studs. In the type B and type C tests, the measured maximum load was controlled by the breaking of the wallboard along its edges. The failure mechanism was initiated by a rotation of the screws at the edges. This was followed by...

Seismic Behavior of Structures with Flexible Diaphragms

Abstract: The influence of floor flexibility on the seismic response of building structures is discussed through comparison of the computed seismic response for structures with flexible diaphragms and counterpart structures with rigid diaphragms. Case studies of three existing buildings with flexible diaphragms and analogous systems with rigid diaphragms are presented to illustrate these differences. Each building was subjected to the 1989 Loma Prieta Earthquake. The structures were: (1) A two-story firehouse in Gilroy with unreinforced masonry walls; (2) a two-story timber office building in Palo Alto with grouted and reinforced clay-unit masonry shear walls; and (3) an eight-story hotel in Oakland with unreinforced clay-unit masonry and reinforced-concrete shear walls. The analytical studies show that, in some cases, diaphragm and shear-wall accelerations can increase with the flexibility of the diaphragm. Torsional forces can reduce considerably as diaphragm flexibility increases. Further, approximate expression...

Displacement-based seismic assessment of existing reinforced concrete buildings

Abstract: Seismic assessment of existing reinforced concrete frame and shear wall buildings is discussed. Building on an earlier preliminary assessment procedure incorporating aspects of capacity design into a systems approach for assessment, suggestions are made towards a displacement-based, rather than forced-based approach to determining available capacity. Based on results from recent experimental programs, procedures are proposed for assessing member strength including column and beam-column joint shear strength, that result in less conservative estimates of performance than would result from application of existing code rules.

Horizontal connections for precast concrete shear wall panels under cyclic shear loading

Abstract: The performance of precast concrete loadbearing shear wall panel structures during an earthquake relies on the behavior and integrity of the connections between the panels. Design of these structures requires the ability to predict the behavior of the connections. This paper presents results of an experimental study of horizontal connections for precast wall panels subjected to reversed cyclic shear deformations combined with simulated gravity loads normal to the connection. The influence of mild steel reinforcement, post tensioning and shear keys was investigated. Experimental results were used to determine the cyclic behavior of the connections and to identify the contribution of the connections and to identify the contribution of the connection components. Simple rational models were proposed to predict the limit states of the connections. Two numerical design examples are included to illustrate the proposed models. Based on the study, design recommendations are presented.

Classification Methodology for Coupled Shear Walls

Abstract: This paper presents guidelines for classification of ductile coupled shear walls (CSWs). It includes two parts: the evaluation of the degree of coupling (DC) between the walls and the coupling beams, and the classification of CSWs. In present practice, DC is defined as the percentage of the base overturning moment carried by the axial tension and compression forces resulting from shears in the coupling beams. The evaluation of DC requires a structural analysis of CSW, which presents serious shortcomings during the preliminary proportioning process. A simple method is proposed in this paper for the evaluation of DC without need for structural analyses. A classification method based on the dynamic properties of CSWs is also proposed. This allows the classification of CSWs into one of the following three categories: a series of linked isolated walls, CSWs, and walls with openings (pierced walls). Finally, numerical examples demonstrate the applicability of the proposed methods. This paper is thought to be ve...

Shear Lag in Shear/Core Walls

Abstract: Shear lag occurs not only in bridge decks and framed tubes, but also in shear/core walls However, there have been relatively few studies on shear lag in wall structures Moreover, most existing theories neglect shear lag in the webs and, although they are acceptable for bridge decks that normally have flanges wider than webs, they may not be applicable to shear/core walls whose webs can be much wider than flanges To study the shear lag phenomenon in wall structures, a parametric study using finite-element analysis is carried out Unlike previous studies that neglected shear lag in the webs, many layers of elements are used for both the webs and flanges so that shear lag in the webs can also be taken into account The results indicate that the shape of the longitudinal stress distribution in an individual web or flange panel is quite independent of the dimensions of the other panels Based on this observation, design charts and empirical formulas for estimating the shear lag effects are developed for pra

Seismic Response of Flexibly Supported Coupled Shear Walls

Abstract: Results from seismic analyses performed on 20-story ductile coupled-shear-wall models designed for Montreal, Canada, are presented. A two-dimensional model was used to idealize the structure including the supporting ground. Allowances were made for nonlinearities not only in the walls and the coupling beams, but also in the soil and foundation elements. The soil foundation was modeled by equivalent massless springs (hangers), located at the base of the structures, allowing for inelastic bearing of the soil and loss of contact (uplift) of base from supporting soil. The stiffnesses of massless foundation springs were obtained using the soil properties that were derived on the basis of strain-dependent shear moduli of real borings. The study showed that the model is capable of tracing the response of coupled shear wall, taking into account the soil-structure interaction effects. Results showed that allowing for foundation flexibility lengthened the fundamental period by a maximum of 33%; it amplified deflections by a maximum of 81%. However the stresses in the walls and the coupling beams attenuated particularly in lower stories. Finally, no substantial variations were observed in the rotational ductility demands of the coupling beams.

Seismic behavior of connections in precast concrete walls

Abstract: An experimental program is summarized which is aimed at enhancing the knowledge base regarding seismic behavior, analysis and design of precast concrete shear walls. The "emulation design" and "jointed construction" philosophies are described, and an idealization of the behavior of precast shear walls is presented. A compendium of connection details for precast concrete shear walls, seven for vertical joints and four for horizontal joints, is selected for further study and the selection process is described. The connection details are proportioned for a prototype shear wall that is designed as part of a six-story precast concrete office building. A description of all connection details and test procedure is given. Highlights from the cyclic load tests of the vertical joint specimens are documented, including connection resistance, displacement response, initial stiffness and energy dissipation capacity.

Effects of Scale and Loading Rate with Tests of Concrete and Masonry Structures

Abstract: Static and dynamic response of large‐scale and reduced‐scale test structures are correlated to discern effects attributable to scale and loading rate. Three case studies are presented where reduced‐scale models were subjected to dynamic excitation using a shaking table. The test structures were: (a) multi‐story reinforced masonry building systems, (b) two‐story unreinforced masonry bearing and shear wall systems, and (c) ten‐story reinforced concrete frame‐wall systems. For each study, static testing of either critical components, or of the complete structural system, was done at a large scale to examine differences attributable to the modeling method, or to the loading procedure.

Continuous transfer beams supporting in‐plane loaded shear walls in tall buildings

Abstract: The failure mechanism and structural behavior of transfer beams supporting in-plane loaded shear walls have received added emphasis owing to their importance in connection with tall building construction. This paper presents an analysis of and investigation of the structural behavior of two-span transfer beam-shear wall systems in tall buildings. The interaction between the transfer girders and the shear wall has been investigated considering interior and exterior column interaction effects. The upper structural form has a significant effect on the failure mechanism of the transfer girders, which can act as full tension members or behave as ordinary flexural beams. Stress distributions in the shear wall interactive zone are presented. The relevant parameters that significantly influence the force transfer mechanism and structural behavior, such as the span/depth ratio of the transfer beam, the span of the shear wall and the stiffness of the support columns, are highlighted. The present paper provides a very useful reference for the design of continuous transfer girders supporting in-plane loaded shear walls in tall buildings.

Elastic analysis of spatial shear wall systems with flexible bases

Abstract: SUMMARY The static linear elastic analysis of spatial shear wall systems with flexible base foundations subjected to lateral loading is considered in this investigation. The discrete force method is adopted, in which the base flexibility is modelled by vertical and rotational springs. The soil and structure were coupled by imposing compatibility conditions along the discrete force method interfaces. The proposed method enforces compatibility of deformation on the relative vertical displacement between adjacent release positions, which are established at assumed contraflexural points of the connecting beams which link the slab together and also at storey level intervals along the intersection lines of adjoining non-coplanar walls. The solution of the compatibility conditions provides the redundant shear forces at the assumed contraflexural positions and the stress resultant solution is completed by statical considerations. The displacement solution corresponding to the stress resultants is then evaluated using the linear elasticity assumption. The objective of the current work is to provide a theoretical treatment of foundation-structure interaction, suitable for implementation in the discrete force method. In addition, the work presents results obtained with the discrete force modelling of soil interaction, and discusses its applicability to some representative problems. The majority of methods of analysis commonly used by engineers for the design of shear wall structures make the assumption that the structure is built into a rigid foundation. Such a procedure simplifies the mathematical analysis of the problem, and may often be sufficiently accurate for all practical purposes. However, depending on the form of structure and the particular soil conditions encountered, it may be considered desirable to estimate the effects of differential settlement produced by foundation movement. The first study of the effect of flexible bases was reported by Coull',2 who treated rotational and vertical base flexibility separately, employing the continuum approach, and then superimposed the results to assess the general case of coupled rotational and vertical base boundary conditions. In a subsequent study, Tso and Chan3 examined simultaneous vertical and rotational movement at the bases of the coupled walls. Pekau4 considered the importance of base flexibility on the nonlinear behaviour of coupled shear walls subjected to pseudo-static lateral loading using the classic continuum method. So far, only a few papers have dealt with the analysis of three dimensional soil-structure interaction problems. Swaddiwudhipong et aL5 were the first to investigate three dimensional

Drift-based methodology for seismic proportioning of coupled shear walls

Abstract: This paper presents a design tool for size proportioning of reinforced concrete coupled shear walls built in seismic regions. It is based on the maximum allowable drift that can be selected by the ...

Clay Brick Masonry Weight Variation

Abstract: The weight of clay brick masonry can vary by more than 30% from the minimum design dead load required by ASCE 7–95 (“Minimum” 1996). Variations in clay brick masonry weight have implications not only for structural and acoustical design, but also for design of heating, ventilating, and air conditioning systems. Incorrect assumptions about wall weight can result in excessive or inadequate seismic loads on masonry walls; insufficient resistance to uplift; increased structural framing and foundation costs; reduced factors of safety in shear walls; increased summer air conditioning costs; overestimates of acoustical transmission loss; and inefficiency in passive heating and cooling systems. Errors in wall weight estimates can penalize those who choose to build with masonry. Designers should be aware that masonry wall weight is variable and should take that variability into consideration where appropriate.

The Role of Building Foundations in Seismic Retrofit

Abstract: Existing buildings which do not satisfy modern seismic design requirements may be rehabilitated economically by the addition of steel bracing or reinforced concrete shear walls. However, steel bracing and concrete shear walls can place severe demands on the building foundation, and the existing foundations are likely to be inadequate. Strengthening of existing foundations may be exceedingly expensive, and the cost of the foundation work may dominate the seismic retrofit effort. Several foundation retrofit strategies are described and discussed. These strategies are invariably expensive, and the engineer may be tempted to place the major investment into strengthening or stiffening the structure with minimal work on the foundation. This concept may lead to increased potential for uplift and temporary overload of footings. In some cases this practice may have beneficial effect regarding the overall seismic response of the structure. It may reduce both seismic forces and maximum displacements experie...

Seismic behavior of a six-story precast concrete office building

Abstract: The work described in this paper was undertaken to demonstrate that precast concrete systems can be practically designed to resist earthquakes, to identify areas where code provisions for seismic design need to be re-evaluated to specifically address the intrinsic characteristics of precast concrete, and to recommend improvements to these areas. The research focuses on a six-story precast concrete office building with a size and layout common in the United States. The system consists of an interior gravity load-resisting frame and a dual system for lateral load resistance consisting of interior shear walls and exterior spandrel frames. A testing program comprising panel-to-panel and beam-to-column connection tests was conducted, and an inelastic dynamic analysis of the lateral load-resisting system was performed. The study shows that the seismic performance of precast systems in resisting seismic loads can be as good as or better than that of cast-in-place systems.

Elastoplastic analysis of spatial shear wall systems by a discrete force method

Abstract: The static linear elastic analysis of spatial shear wall systems subjected to lateral loading is considered. A discrete force method is developed for the solution of such problems. The proposed method enforces compatibility of deformation on the relative vertical displacement between adjacent release positions, which are established at assumed contraflexural points of the connecting beams which link the slab together and also at storey-level intervals along the intersection lines of adjoining noncoplanar walls. The solution of the compatibility conditions provides the redundant shear forces at the assumed contraflexural positions and the stress-resultant solution is completed by statical considerations. The displacement solution corresponding to the stress resultants is then evaluated using the linear elasticity assumption. The basic formulation neglects the torsional resistance of the individual wall elements which is shown to be significant in a typical open section example. An iterative procedure is adopted for the incorporation of wall element torsional stiffness and is shown to be effective. The efficiency and versatility of the discrete method are illustrated by application of the technique to the analysis of two practical, complex wall systems.

Analytical seismic response of wood shear walls using hysteresis models of nailed joints

Abstract: The nonlinear seismic response of wood shear walls as studied using six hysteris models for nailed joints : bilinear, hybrid, Clough, Q-hyst, Origin-oriented, and Kivell models. The main objectives of the study were to investigate the performance and predictions of these models and to find the major characteristics that influence the behavior of shear walls when subjected to earthquake loadings. The obtained analytical responses are compared with some existing test results. Maximum displacements, maximum reaction forces, energy dissipation, and frequency contents are the significant parameters used to compare the predictions of each model with the experimental results. It was found that models with stiffness degradation and pinching effects are the most suitable models for nailed joints.

Seismic Performance of Confined Sill Plate Connections

Abstract: In the aftermath of the 1994 Northridge earthquake, extensive field investigations revealed damage in wood frame construction in the form of splitting of the 2 × 4 or 2 × 6 wood sill plates along the line of anchor bolts that typically connect shear walls to the masonry or concrete foundation. Due to the severity of such brittle failures, the city of Los Angeles has recently restricted the use of 2× dimension lumber in sill plates and requires the use of 3× dimension lumber. This paper presents an experimental investigation of the performance of 2× dimension lumber sill plate connections at the yield and ultimate limit states during incremental quasi-static reversed cyclic loading and suggests possible cost-effective retrofit strategies for their improved seismic performance without having to increase the sill plate thickness. Proposed retrofit strategies are based on providing confinement to the sill plate using metal reinforcing straps and reinforcing clamps to increase the deformation capability and en...