Showing papers on "Shear wall published in 1992"

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...

Nonlinear seismic analysis and design of reinforced concrete buildings

Abstract: Energy concepts and damage models. Issues and future directions in the use of an energy approach for seismic-resistant of design structures. Seismic design based on ductility and cumulative damage demands and capacities. On energy demand and supply in SDOF systems. Seismic design of structures for damage control. Seismic analysis of degrading models by means of damage functions concept. Seismic energy demands on reinforced concrete ductile moment-resisting frame buildings. Response of reinforced concrete moment frames to strong earthquake ground motions. An energy-based damage model for inelastic dynamic analysis of reinforced concrete frames. Seismic motion damage potential for R/C wall-stiffened buildings. Comparison of damage measures for the design of reinforced concrete flexural members. Behaviour of buildings with structural walls. Design of R/C structural walls: balancing toughness and stiffness. Advances in the design for shear of RC structural walls under seismic loading. Required shear strength of earthquake-resistant reinforced concrete shearwalls. Macroscopic/modelling for nonlinear analysis of RC structural walls. Nonlinear seismic analysis of structural walls using the multiple-vertical-line-element model. A section analysis model for the nonlinear behaviour of members under cyclic loading. Two-and three-dimensional nonlinear finite-element analysis of structural walls. Finite element modelling in structural reinforced concrete analysis. Nonlinear seismic analysis of hybrid reinforced concrete frame-wall buildings. Analysis of ultimate states of reinforced concrete wall-frame structures. Linear and nonlinear seismic response of prefabricated combined [frames-tall shear walls] systems of construction. Laboratory testing and mathematical modelling of RC coupled shear wall system for nonlinear static and dynamic response prediction with considered time varying axial forces. Nonlinear response asymmetric building structures and seismic codes: a state of the art review. Index.

Monotonic and cyclic nail connection tests

Abstract: The results of monotonic and cyclic nail connection lateral tests are presented. The tests are part of an extensive experimental and analytical study to investigate the behaviour of timber shear walls subjected to earthquakes. The results from the nail connection tests were used in a larger study of timber shear walls. The nonlinear load–deflection curves were used for modelling the nail connection between the sheathing and the framing of the shear walls. The dependency of the nail connection on the grain orientation of the timber materials is investigated along with the evidence that the material properties of the nails are the primary parameters for the load–displacement characteristics of the connection made with hot-dipped, galvanized common nails. Both the monotonic and cyclic lateral behaviours of the connections are established. The premise that the hysteresis for the nail connection is contained within an envelope defined by the monotonic load–displacement curve is confirmed. These connection char...

Monotonie and cyclic tests of timber shear walls

Abstract: The results for monotonic (ramp load) and slow cyclic racking tests of timber shear walls are presented. The tests are part of an extensive experimental and analytical study to investigate the behaviour of timber shear walls subjected to earthquakes. The results of full-size shear wall tests show the important influence of the nail connection between the sheathing and the framing on the load-displacement characteristics of shear walls. The premise that the hysteresis for the shear wall is contained within an envelope defined by the monotonic load-displacement curve for the wall is confirmed. Also, the hysteresis is studied to determine the physical behaviour that causes the shape of the hysteresis to be dependent on the maximum displacement of the wall. Both the monotonic and cyclic racking behaviours of timber shear walls are established; and the performances of plywood and waferboard sheathed shear walls are compared. Key words: full-scale monotonic and cyclic tests, plywood, waferboard, timber shear walls.

Seismic Response of Interior Slab-Column Connections With Shear Capitals

Abstract: Four interior slab-column connection subassemblies were tested under earthquake-type loads. The details of the study are described. The effect of the size of shear capital on the strength stiffness, and failure mechanisms of a slab-column connection was studied. Both punching shear failures and bending failure were observed. The current ACI Building Code (ACI 318-89) recognizes that there are two possible locations of the critical seciton of a slab, which vary in depth. Based on the test results, the critical section of a slab with shear capitals subjected to seismic loads may be at a location not recognized by the code. A shear capital must have a sufficient length with respect to the depth of the slab and be appropriately reinforced to effectively increase the shear capacity of the connection.

Incorporating Load Sharing in Shear Wall Design of Light‐Frame Structures

Abstract: A three‐dimensional nonlinear finite element model of a light‐frame wood building was created and used to determine internal forces caused by wind pressure in shear walls. Comparing the results with current design procedures led to two fundamental observations: (1) The assumption of current procedures that one‐half of the load is transferred directly to the foundation is correct; (2) calculating internal forces in the shear walls by simple‐ and continuous‐beam models does not reflect the real situation and may lead to erroneous results. Linear and nonlinear models assuming the roof diaphragm as a rigid beam on elastic supports were proposed, analyzed, and compared with the finite element solution of an experimentally verified model. Satisfactory accuracy can be achieved by using the rigid‐beam analogy if the shear stiffness of the walls is known.

Finite element model for seismic RC coupled walls having slender coupling beams

Abstract: A finite element model capable of tracing the nonlinear response of coupled shear walls to earthquake motions is proposed. The walls are idealized as an assembly of quadrilateral elements with three degrees of freedom, two translational and one-rotational, at each corner, and nonlinearities, such as cracking, crushing of concrete, and yielding of steel, are included in the model. The coupling beams are idealized as line elements, and the nonlinearities are confined to element ends through inelastic experimentally based moment-rotation relationships. Allowance has been made for stiffness degradation and bond slippage. The rotational degree of freedom to the plane stress element makes the compatibility of rotations at the coupling-beam-wall interface possible, the evaluation of coupling beams rotation straightforward and the mathematical model elegant. The model was applied to trace the response of two coupled shear walls tested elsewhere and the results achieved were in good agreements with experimental re...

Concrete Shear in Earthquake

Abstract: Experimental studies of membrane shear behaviour State-of-the-art reports Reports on tests of structures: elements and members Reports on tests of structures: shear walls Reports on tests of structures: nuclear containment structures Theoretical studies of membrane shear behaviour State-of-the-art reports Analytical models: elements and members Analytical models: shear walls Applications of finite element methods Effect of shear on energy dissipation State-of the-art-report Sources of ductility and restrictions Design for earthquake resistance Review of design philosophies for shear Design of structures Research and development needs

Development of Design Spectra for Actively Controlled Wall‐Frame Buildings

Abstract: Preliminary design of a structure controlled by active bracing or mass dampers to withstand seismic motion or high winds requires rapid means of analysis and estimates. A response spectrum technique applied to simplified models of complex structures can provide such means. The spectra required for preliminary evaluation of a controlled structure include, besides the usual response parameters (displacement, acceleration, base shear), the control resource parameters, such as the size and capacity of hydraulic actuators; power requirements; and energy consumption. This paper presents an approach to develop design spectra based on the analogy of behavior of wall frame structures with the behavior of shear‐flexural cantilever beams treated by the continuum approach. This approach is verified numerically and experimentally using simplified parameters representing the structures. The same approach is further used to develop typical response and resource spectra using simulated ground motions according to a curre...

Measuring the stiffness of concrete shear walls during dynamic tests

Abstract: Results from a series of experiments designed to measure the stiffness of low-aspect-ratio, reinforced-concrete shear walls subjected to simulated seismic inputs on a shake table are reported. The geometry of the test structures allows them to be modeled as single-degree-of-freedom systems. Forces were estimated from accelerometer measurements on masses attached to the structures. Dynamic relative-displacement measurements were obtained from groups of strain gages wired in series to act as one continuous gage. Because this method measures relative displacements, potential sources of error associated with unspecified base motion are avoided. tiffness values determined from the relative displacement measurements were compared with stiffness values determined indirectly from frequency-response functions. Measured, accelerometer data were used to calculate the frequency-response functions. The stiffness values determined from the relative-displacement measurements gave results similar to those given by mechanics-of-materials beam theory that accounts for shear deformation. The stiffness values determined from the frequency-response functions were considerably less than those from the theory.

Response of an instrumented masonry shear wall building with flexible diaphragms during the Loma Prieta Earthquake

Abstract: RESPONSE OF AN INSTRUMENTED MASONRY SHEAR WALL BUILDING WITH FLEXIBLE DIAPHRAGMS DURING THE LOMA PRIETA EARTHQUAKE The subject structure of this study is a two-story office building located at Palo Alto, California. The structure was built in 1974. Recorded peak ground accelerations were as high as O.21g and peak roof accelerations as high as O.S3g. Considerable amplifications of the peak accelerations between the ground and the roof were observed. The building withstood the Lorna Prieta Earthquake with little damage. Masonry construction used in Northern California is similar throughout the United States. Because moderate earthquakes are expected east of the Rocky Mountains, the response of the office building at Palo Alto can help foretell the earthquake hazard in the eastern and midwestern United States. The ground motions recorded at the office building at Palo Alto represent an upper bound for assessing possible hazards associated with similarly constructed buildings in the eastern United States. Since the building was not appreciably damageg, even with these high accelerations, there is hope that similar historic buildings across the nation may survive a future earthquake. However, such extrapolation is not warranted unless a detailed investigation is done to examine the reasons for the superior performance. The objectives of this study are the following: 1) Investigate the reasons of the survival of the office building at Palo Alto with the use of both simplified and state-of-the-art methods. 2) Assess the effectiveness of a discrete :MDOF dynamic model on the seismic evaluation of this building and similar masonry buildings with flexible diaphragms. 3} Correlate the recorded, observed and computed response at the office building at Palo Alto with estimates of dynamic response and prescribed strength by state-of-the-art masonry and seismic codes.

Design Considerations for Using Adhesives in Shear Walls

Abstract: The results of earthquake tests of light-frame, wood shear walls conducted by several researchers are reviewed. The effect of using adhesives to attach the sheathing material to the framing is considered, specifically, potential problems due to the adhesive strengthening and stiffening of the wall system when subjected to an inertial loading such as an earthquake. None of the current design and building codes used in the United States address the use of adhesives, and engineers may design unsafe structures. Change in probable failure modes from the traditional ductile yielding of the nail connections between the sheathing and the framing to the anchorage connections or adjacent structural components is highlighted. Recommendations for changes that should be made to the building and design codes are suggested. Changes to the seismic design procedures only are recommended and the improved performance of adhesives in shear walls subjected to wind or other applied loads is acknowledged.

Bending and torison of doubly symmetric core shear walls

Abstract: A theoretical and experimental investigation of the flexural and torsional properties of doubly symmetric core shear walls, with lintel beams providing bracing across the openings at each storey level, is described. Such structures are used in tall buildings to support gravity loads and to resist horizontal forces induced by wind and earthquakes. The theoretical model developed is based on an equivalent closed section and is consistent with established open section and closed section behaviour at the two extremes of bracing. For intermediate bracing, the model incorporates the influences of bending and shear deformation of the bracing beams, out-of-plane bending of the side walls and continuousshear flow around the contour of the assumed equivalent closed section. The theoretical model is validated by a series of tests on perforated aluminium tubes, covering a wide range of lintel beam and effective side wall stiffnesses. The results indicate clearly that side wall distortion can reduce the torsional stiffness of such sections very significantly.

A simple quadrilateral shear panel element

Abstract: A shear panel element of general quadrilateral shape is so formulated that it assumes a state of constant shear flow. This is achieved by using isoparametric shape functions to approximate the displacement field and then using the mean of the strain-displacement matrix to evaluate shear strain and the resulting stiffness matrix. Numerical examples show that the element reproduces analytical solutions when its shape is rectangular and behaves satisfactorily when its shape is not rectangular.

Masonry wall frame design and performance

Abstract: Tall masonry building in active seismic or severe wind regions have typically been designed as shear wall buildings. This paper presents an alternative lateral force resisting system cailed a wall frame. This new masonry system is particularly advantageous for seismic and windy regions because it utilizes the nonlinear inelastic load deformation characteristics of the masonry beams and is thus a ductile system. Basic design assumptions and experimental test data are presented.

Air permeability in a seismically loaded shear wall

Abstract: We performed an experimental study to measure the air leakage from a seismically damaged concrete shear wall. In this study, we used static load‐cycle testing to simulate earthquake loading and made permeability measurements by pressurizing one side of the shear wall above atmospheric conditions and recording the transient‐pressure decay. The air permeability measurements made on the shear wall before loading fell within the range of values published in the literature for concrete permeability. As long as the structure exhibited linear load‐displacement response, no variation in the air permeability was detected. Experimental results indicate that the air permeability in the shear wall increased by a factor of 40 after the wall had been damaged (cracked).

Hysteretic loops and damage assessments of R.C. shear walls with aspect ratios between 0.65 to 1.90

Abstract: This paper proposes the empirical equations for the prediction of load‐deflection curves for one‐story and two‐story R.C. shear walls under static monotonic or reversed cyclic loads plus axial compressive loads. The width of the wall is 70 cm; the thickness of the wall is 7 cm; the height of the wall for each story is either 50 cm or 75 cm; the cross‐section of boundary columns is 17 cm x 15 cm. The shear‐span to wall‐width ratios are from 0.65 to 1.90. The P‐A curves under monotonic loading are predicted first. The hysteretic rules are based on the deteriorating envelopes. The deterioration of the residual ultimate capacity of wall is a function of energy dissipation and the maximum lateral deflection of wall in the previous loading cycles. All the predicted load‐deflection curves are compared to the experimental results with reasonable accuracy. This paper also proposes the damage assessment by either the typical cracked patterns of walls or by the calculation of residual capacity of walls afte...