Showing papers on "Shear wall published in 1990"

In‐Plane Resistance of Reinforced Masonry Shear Walls

Abstract: Flexural and shear strengths of reinforced masonry shear walls are examined, based on experimental results obtained from 22 6-ft. by 6-ft. masonry wall specimens. These results are summarized and current design formulae examined. It is found that the simple flexure theory based on the plane-section assumption can be applied to square wall panels with good accuracy. Moreover, it appears to be consistently conservative. The 1988 Uniform Building Code specifications for the shear strength tend to be very conservative for the square wall panels studied and less conservative for walls with lower aspect ratio. Furthermore, the code specifications tend to overestimate the shear strength contributed by the horizontal reinforcement and neglect the influence of axial stress. Hence, a new shear formula that takes into account the influence of axial stress and flexural reinforcement is proposed. The formula appears to have good correlation with experimental results obtained in this study as well as those of others.

Evaluation of seismic damage indices for reinforced concrete structures. technical report

Abstract: This report presents some new information about the correlation between various local and global damage indices, and the damage level. This information is obtained by analyzing the results of numerical simulations of the seismic response of reinforced concrete frames. The seismic response of three code-designed reinforced concrete frames subjected to a set of artificially generated and recorded earthquakes is computed by using an improved version of the computer code SARCF-II, described herein. This new version is tested by comparing computed results to experimental ones obtained from a reinforced concrete model tested at the University of Illinois at Urbana-Champaign. The Maximum Softening as a global damage index is compared to weighted averages of local damage indices and to traditional measures of damage such as the maximum interstory drift, the permanent interstory drift and the maximum ductility ratio for beams and columns. This Maximum Softening index is also compared to the Final Softening one. These discussed global softening indices are helpful for identifying structures that need careful inspection after an earthquake and are applicable to reinforced concrete structures with/without shear walls.

Shear Wall Resistance of Lightgage Steel Stud Wall Systems

Abstract: Experimental investigations were conducted to evaluate the lateral load‐deflection characteristics of lightgage steel stud/gypsum wallboard panel combinations subjected to lateral cyclic loads. In all, six 8′ × 8′ specimens were tested. A reasonable one‐to‐one correspondence between the strap area increase and the increase in the contribution from the strap to the overall loadcarrying capacity of the panel at intermediate and high drift ratios was observed. The panel lateral stiffness for a given stabilized cycle degraded by about 7% to 15% as compared with the lateral stiffness of the corresponding virgin cycle. Lateral stiffness degradation increased as the drift ratios became larger. The energy dissipation ability of the panels in the stabilized cycle was about 60% of the virgin cycle. An average value of equivalent viscous damping for all the cycles based on panel hysteretic behavior was about 12%.

Static and dynamic analysis of timber shear walls

Abstract: Light-frame wood structures have evolved in recent years to the point where their earthquake resistance is now questionable. Shear walls are commonly used to provide lateral stiffness and strength in wood buildings. Therefore, accurate predictions of the seismic behaviour of timber shear walls are necessary in order to evaluate the safety of existing timber buildings and improve design practice. This paper develops and validates a simple structural analysis model to predict the behaviour of timber shear walls under lateral static loads and earthquake excitations. The model is restricted to two-dimensional shear walls with arbitrary geometry. The nonlinear load –slip characteristics of the fasteners are used in a displacement-based energy formulation to yield the static and dynamic equilibrium equations. The model is embedded in a shear wall analysis program (SWAP) developed for microcomputer applications. The predictions of the model are compared with full-scale racking and shake table tests. The ability ...

Earthquake Design Practice for Buildings

Abstract: Foreword by Professor Robin Spence 1 The lessons from earthquake damage, 1.1 Damage studies, 1.2 Ground behaviour, 1.3 Structural collapse, 1.4 Important categories of damage, 1.5 Reinforced concrete, 1.6 Structural steelwork, 1.7 Masonry, 1.8 Timber, 1.9 Foundations, 1.10 Non-structural elements, 1.11 Bibliography Ground motion, 2.1 Primary and secondary sources of earthquake damage, 2.2 Earthquake basics, 2.3 Earthquake probability and return periods, 2.4 Performance objectives under earthquake loading, 2.5 Representation of ground motion, 2.6 Site effects, 2.7 Quantifying the risk from earthquakes, 2.8 Design earthquake motions, 2.9 References The calculation of structural response, 3.1 Introduction, 3.2 Basic principles of seismic analysis, 3.3 Linear elastic forms of seismic analysis, 3.4 Non-linear analysis, 3.5 Analysis for capacity design, 3.6 Analysis of building structures, 3.7 References Analysis of soils and soil-structure interaction, 4.1 Introduction, 4.2 Soil properties for seismic design, 4.3 Liquefaction, 4.4 Site-specific seismic hazards, 4.5 Soil-structure interaction, 4.6 References Conceptual design, 5.1 Design objectives, 5.2 Anatomy of a building, 5.3 Planning considerations, 5.4 Structural systems, 5.5 Cost of providing seismic resistance, 5.6 References Seismic codes of practice, 6.1 Role of seismic codes in design, 6.2 Development of codes, 6.3 Philosophy of design, 6.4 Code requirements for analysis, 6.5 Code requirements for strength, 6.6 Code requirements for deflection, 6.7 Load combinations, 6.8 Code requirements for detailing, 6.9 Code requirements for foundations, 6.10 Code requirements for non-structural elements and buildingcontents, 6.11 Other considerations, 6.12 References Foundations, 7.1 Design objectives, 7.2 'Capacity design' considerations for foundations, 7.3 Safety factors for seismic design of foundations, 7.4 Pad and strip foundations, 7.5 Raft foundations, 7.6 Piled foundations, 7.7 Retaining structures, 7.8 Design in the presence of liquefiable soils, 7.9 References Reinforced concrete design, 8.1 Lessons from earthquake damage, 8.2 Behaviour of reinforced concrete under cyclic loading, 8.3 Material specification, 8.4 Analysis of reinforced concrete structures, 8.5 Design of concrete building structures, 8.6 Design levels of ductility, 8.7 Design of reinforced concrete frames8.8 Shear walls, 8.9 Concrete floor and roof diaphragms, 8.10 Unbonded prestressed construction, 8.11 References Steelwork design, 9.1 Introduction, 9.2 Lessons learned from earthquake damage, 9.3 The behaviour of steelwork members under cyclic loading, 9.4 Materials specification, 9.5 Analysis of steelwork structures, 9.6 Design of steel building structures, 9.7 Design levels of ductility, 9.8 Concentrically braced frames (CBFs),9.9 Eccentrically braced frames (EBFs),9.10 Moment-resisting frames, 9.11 Steel-concrete composite structures, 9.12 References Masonry, 10.1 Introduction, 10.2 Forms of masonry construction and their performance inearthquakes, 10.3 Designing masonry for seismic resistance, 10.4 Analysis of masonry structures, 10.5 Simple rules for masonry buildings 10.6 References Timber, 11.1 Introduction, 11.2 Characteristics of timber as a seismic-resisting building material, 11.3 The lessons from earthquake damage, 11.4 Design of timber structures, 11.5 References Building contents and cladding, 12.1 Introduction, 12.2 Analysis and design of non-structural elements for seismicresistance, 12.3 Electrical, mechanical and other equipment, 12.4 Vertical and horizontal services, 12.5 Cladding, 12.6 References Seismic isolation, 13.1 Introduction, 13.2 Lessons from 30 years of seismic isolation, 13.3 Seismic isolation systems, 13.4 Design considerations, 13.5 Analysis of seismic isolation systems, 13.6 Testing of bearing systems, 13.7 Active and semi-active systems, 13.8 References Assessment and strengthening of existing buildings, 14.1 Introduction, 14.2 Performance of

Analytical predictions of the seismic response of friction damped timber shear walls

Abstract: A new concept for the earthquake resistant design of timber shear wall structures is proposed. By providing friction devices in the corners of the framing system of the shear wall, its earthquake resistance and damage control potential can be enhanced considerably. During severe earthquake excitations, the friction devices slip and a large portion of the seismic energy input is dissipated by friction rather than by inelastic deformation of the sheathing-to-framing connectors. A simple numerical model is developed and results of inelastic time-history dynamic analyses show the superior performance of the friction damped timber shear walls compared to conventional shear wall systems. The proposed friction devices act both as safety valves by limiting the inertia forces transmitted to the structure, and as structural dampers by dissipating a significant portion of the seismic energy input. The devices can be used in any configuration of the framing system to accommodate architectural or construction requirements. The damping system may also be conveniently incorporated in existing timber shear wall buildings to upgrade significantly their earthquake resistance.

Seismic Fragility Analysis of Shear Wall Structures

Abstract: This paper presents an analytical method to generate seismic fragility curves for shear wall structures. Uncertainties in earthquake motion and structure are quantified by evaluating uncertainties in pertinent parameters which define earthquake-structure system. For illustration, the fragility curves for a eight-story shear wall building are constructed.

Flexure and shear reponse of reinforced masonry walls

Abstract: The flexural and shear behavior of reinforced masonry shearwalls subject to both monotonic and cyclic lateral loads is examined. The study is based on the experimental results obtained from more than twenty 6 x 6 ft reinforced masonry wall panels tested under in-plane vertical and lateral loads. For the square wall panels studied, the shear strength is initially provided by the diagonal compression strut mechanism, and later by the interface shear as well as the resistance of the horizontal reinforcement. A simple shear formula, based on the latter and proposed in a prior study, appears to be reliable. In general, wall panels that failed shear exhibited a more brittle behavior than those that failed in flexure. Furthermore, based on experimental data, an empirical formula governing the degradation of shear strength under cyclic displacement reversals is developed.

Experimental behaviour of reinforced concrete walls under earthquake loading

Abstract: SUMMARY The experimental work and first results of a recently completed experimental research programme investigating the response of reinforced concrete (RC) walls under earthquake (EQ) loading are discussed in this paper. A brief literature review is given as a prelude to the outline of research objectives. The tests are presented in two groups according to the scale of models. For the 15 scale tests, a modified similitude relation for small scale reinforced concrete dynamic modelling is developed. Based on the chosen model parameters, the design of the isolated RC walls is given. The test-rig set-up and the EQ input signals suitable for testing the model on the Imperial College shake-table are also discussed. Preliminary observations regarding stiffness, strength and failure modes of the RC wall models are given. Experimental results from the shake-table are compared to tests, at the same scale, under static cyclic conditions. For the scale 1:2.5 cyclic tests a different test-rig assembly is designed. The test results are given in three pairs of flexurally similar walls followed with general observations and discussion. Finally, conclusions are drawn regarding experimental procedures and behaviour patterns of the tested models. Observations from field studies of earthquakes’-3 suggest that a level of drift control higher than that demonstrated by moment resisting frames is necessary in order to avoid excessive non-structural damage. This is shown by the extent of non-structural damage sustained by RC structures subjected to strong ground motion, primarily due to excessive storey displacements. Stiff shear resisting members such as ‘shear walls’ not only enhance the integrity of the load bearing and non-structural components but also may reduce damage to service installations. Present code requirements for earthquake-resistant design often underestimate the ductility of RC walls. This is manifested in the increased design base shear coefficient imposed on buildings with walls. The reason for this undue conservatism may be attributed to an attempt to avoid observed brittle modes of failure in walls designed in accordance with the code provisions for flexural behaviour. Reinforced concrete walls are also referred to as ‘shear’ walls because they resist a high proportion of the shear due to lateral loads. However, failures of RC walls are not necessarily dominated by shear deformations. The balance between shear and flexural loading has a very significant role in the deformational and strength characteristics. Walls with a shear ratio (M/ VL--M and V are applied moment and shear force respectively, L is total wall width) of more than about 1.5 possess flexure-dominated deformational characteristics and are termed ‘flexural’ walls. Walls with a shear ratio of less than 1.5 are referred to as ‘squat’ walls and are influenced more by the presence of high shear stresses. Even though RC walls in a building will be loaded in a complex manner according to the overall geometry, stiffness and other structural building characteristics, the highest forces are expected to occur at the lower floors. Ensuring the integrity and energy dissipation capacity of these critical portions of RC walls will lead to a safer EQ-resistant design.

Torsion and Bending of Braced Thin‐Walled Open Sections

Abstract: The paper describes a theoretical and experimental study of the flexural and torsional properties of braced, thin‐walled, open sections, such as elevator core shear walls with lintel beams across openings at each floor level. The theoretical model developed is based on an equivalent closed section, and it is consistent with established open‐section and closed‐section behavior at the two extremes of bracing. For intermediate bracing, the theoretical model incorporates the influences of bending and shear deformation of the bracing, continuous shear flow around the equivalent closed section, and out‐of‐plane bending of the side walls, which is analyzed approximately using plate theory. The theoretical model is validated, for the entire range of bracing stiffness, by comparison with a series of tests on perforated, extruded aluminum tubes. The influences of continuous shear flow around the equivalent closed section and out‐of‐plane bending of the side walls, which have not been considered previously, are show...

Cracked Coupling Slabs in Shear Wall Buildings

Abstract: A finite element analysis is performed on the effective coupling stiffness and bending stress distribution in a cracked slab coupling a pair of laterally loaded shear walls. Particular attention is focused on the effect of a transverse crack situated at the highly stressed inner edges of the walls. The influence of the length of crack on the effective stiffness and longitudinal bending stress distribution is examined for typical slab-wall configurations. It is shown that the presence of a transverse crack results in a substantial reduction in slab-coupling stiffness, especially when the wall-opening ratio is small. The distribution of longitudinal bending moments in the slab is not greatly affected by the presence of a crack, apart from the region close to the crack tip, where bending stress concentrations occur.

Stiffness and hysteretic energy loss of a reinforced-concrete shear wall

Abstract: A static, cyclic test of one of the largest reinforced concrete shear walls to be investigated in a laboratory is reported. The test was performed to study the dynamic characteristics (stiffness and hysteretic energy loss) of the shear wall. Very sensitive displacement gages are needed to measure the small deformations. The large forces required to load the structure make the test results susceptible to deformation of the support fixture. With these concerns in mind, instrumentation and data-reduction methods were developed that could separate model deformations from displacements caused by support motion. Also, model displacements were separated into shear and bending components. Results showed that prior to cracking, overall stiffness as well as the individual components of stiffness are accurately predicted by mechanics of materials beam theory that accounts for shear deformation. Equivalent viscous damping ratios that were determined from the hysteretic energy before and after cracking were similar.

Evaluation of ATC Requirements for Soil‐Structure Interaction Using Data from the 3 March 1985 Chile Earthquake

Abstract: The effect of soil‐structure interaction on building responses is investigated using data from the 3 March 1985 Chile earthquake. Four shear wall buildings located in Vin˜a del Mar, Chile and subjected to strong, long duration, earthquake ground motions during the 3 March 1985 Chile earthquake are studied. Detailed analyses are conducted on one building using available information on soil properties, measured periods, and recorded ground motions. Based on the detailed study, ATC‐3 procedures are used to incorporate soil‐structure interaction effects for three additional buildings. The analyses indicate that soil‐structure interaction is an important consideration for the stiff shear wall buildings located in Vin˜a del Mar, Chile. Reductions in base shear of 10 to 47% were computed; however, roof drift ratios generally were unchanged. For spectra representing US design ground motions (ATC), reductions in base shear are not expected to be as pronounced and roof drift ratios are expected to increase...

Plastic buckling capacity of square shear plates with circular perforations. in: structural stability research council. 1990 annual technical session, stability of bridges, st. louis, missouri, april 10-11, 1990

Abstract: This paper presents the results of a finite element buckling analysis of perforated shear plates with inelastic material behavior. The problem typically applies to the design of working platforms and support caissons of offshore steel structures that are often designed with plate boxes or plate girders. The important shear walls or shear webs must often be perforated to allow utilities, etc., to pass through. The failure mode of these large perforated shear panels is typically plastic shear buckling. In the calculations nonlinearities in material properties and geometry were taken into account. Single unreinforced round holes were considered with variations of hole size and hole location.