Showing papers in "Journal of Structural Engineering-asce in 2003"

State of the art of structural control

Abstract: In recent years, considerable attention has been paid to research and development of structural control devices, with particular emphasis on alleviation of wind and seismic response of buildings and bridges. In both areas, serious efforts have been undertaken in the last two decades to develop the structural control concept into a workable technology. Full-scale implementation of active control systems have been accomplished in several structures, mainly in Japan; however, cost effectiveness and reliability considerations have limited their wide spread acceptance. Because of their mechanical simplicity, low power requirements, and large, controllable force capacity, semiactive systems provide an attractive alternative to active and hybrid control systems for structural vibration reduction. In this paper we review the recent and rapid developments in semiactive structural control and its implementation in full-scale structures.

Nonlinear analysis of axially loaded concrete-filled tube columns with confinement effect

Abstract: Proper material constitutive models for concrete-filled tube (CFT) columns are proposed and verified by the nonlinear finite element program ABAQUS against experimental data. The cross sections of the CFT columns in the numerical analysis are categorized into three groups, i.e., circular section, square section, and square section stiffened by reinforcing ties. Via the numerical analyses, it is shown that for circular CFT columns, the tubes can provide a good confining effect to the concrete especially when the width-to-thickness ratio D/t is small (say D/t 30). The confining effect of square CFT columns with reinforcing ties is enhanced by the use of reinforcing ties especially when the tie spacing is small and the tie number (or tie diameter) is large.

Three-strut model for concrete masonry-infilled steel frames

Abstract: Masonry infill panels in framed structures have been long known to affect strength, stiffness, and ductility of the composite structure. In seismic areas, ignoring the composite action is not always on the safe side, since the interaction between the panel and the frame under lateral loads dramatically changes the stiffness and the dynamic characteristics of the composite structure, and hence, its response to seismic loads. This study presents a simple method of estimating the stiffness and the lateral load capacity of concrete masonry-infilled steel frames (CMISFs) failing in corner crushing mode, as well as the internal forces in the steel frame members. In this method, each masonry panel is replaced by three struts with force-deformation characteristics based on the orthotropic behavior of the masonry infill. A simplified steel frame model is also presented based on the documented modes of failure of the CMISF. The method can be easily computerized and included in nonlinear analysis and design of three...

Modeling Reinforced-Concrete Beam-Column Joints Subjected to Cyclic Loading

Abstract: A model is developed to represent the response of reinforced-concrete beam-column joints under reversed-cyclic loading The proposed model provides a simple representation of the primary inelastic mechanisms that determine joint behavior: Failure of the joint core under shear loading and anchorage failure of beam and column longitudinal reinforcement embedded in the joint The model is implemented as a four-node 12-degree-of-freedom element that is appropriate for use with typical hysteretic beam-column line elements in two-dimensional nonlinear analysis of reinforced concrete structures Constitutive relationships are developed to define the load-deformation response of the joint model on the basis of material, geometric, and design parameters Comparison of simulated and observed response for a series of joint subassemblages with different design details indicates that the proposed model is appropriate for use in simulating response under earthquake loading

Seismic Performance of Precast Reinforced and Prestressed Concrete Walls

Abstract: Two geometrically identical half-scale precast concrete cantilever wall units were constructed and tested under quasi-static reversed cyclic lateral loading. One unit was a code compliant conventionally reinforced specimen, designed to emulate the behavior of a ductile cast-in-place concrete wall. The other unit was part of a precast partially prestressed system that incorporated post-tensioned unbonded carbon fiber tendons and steel fiber reinforced concrete. Hysteretic energy dissipation devices were provided in the latter unit in the form of low yield strength tapered longitudinal reinforcement, acting as a fuse connection between the wall panel and the foundation beam. The conventional precast reinforced wall performed very well in terms of the ductility capacity and energy absorption capability, reaching 2.5% drift before significant strength degradation occurred. The precast partially prestressed wall unit achieved drift levels well in excess of 3% with no visible damage to the wall panel prior to failure. Test results and performance comparisons between the precast partially prestressed wall system and the precast conventionally reinforced unit are presented.

Fatigue Strength of Steel Girders Strengthened with Carbon Fiber Reinforced Polymer Patch

Abstract: Fatigue sensitive details in aging steel girders is one of the common problems that structural engineers are facing today. The design characteristics of steel members can be enhanced significantly by epoxy bonding carbon fiber reinforced polymers~CFRP! laminates to the critically stressed tension areas. This paper presents the results of a study on the retrofitting of notched steel beams with CFRP patches for medium cycle fatigue loading (R50.1). A total of 21 specimens made of S12734.5 A36 steel beams were prepared and tested. Unretrofitted beams were also tested as control specimens. The steel beams were tested under four point bending with the loading rate of between 5 and 10 Hz. Different constant stress ranges between 69 and 379 MPa were considered. The length and thickness of the patch were kept the same for all the retrofitted specimens. In addition to the number of cycles to failure, changes in the stiffness and crack initiation and growth were monitored during each experiment. The results showed that the CFRP patch not only tends to extend the fatigue life of a detail more than three times, but also decreases the crack growth rate significantly.

Lateral Stiffness of Brick Masonry Infilled Plane Frames

Abstract: In a companion paper, a new finite element technique for the analysis of brickwork infilled plane frames under lateral loads has been presented. In the present paper, the influence of the masonry infill panel opening in the reduction of the infilled frames stiffness has been investigated by means of this technique. A parametric study has been carried out using as parameters the position and the percentage of the masonry infill panel opening for the case of one-story one-bay infilled frame. The investigation has been extended to the case of multistory, fully or partially infilled frames. In particular, the redistribution of action effects of infilled frames under lateral loads has been studied. It is shown that the redistribution of shear force is critically influenced by the presence and continuity of infill panels. The presence of infills leads, in general, to decreased shear forces on the frame columns. However, in the case of an infilled frame with a soft ground story, the shear forces acting on column...

Damping Evaluation Using Full-Scale Data of Buildings in Japan

Abstract: Full-scale data on damping of buildings in Japan have been collected by the Damping Evaluation Committee of the Architectural Institute of Japan. Reliable data on 137 steel-framed buildings, 25 reinforced concrete (RC) buildings, 43 steel-framed reinforced concrete (SRC) buildings have been compiled in a database. Most of these data have been evaluated from vibration tests in a small amplitude region. This paper describes damping ratio characteristics of steel-framed buildings and RC/SRC buildings based on analyses of the database, including effects of several building factors. It is shown that the higher the building, the smaller the first-mode damping ratio. Furthermore, the damping ratios seem to be affected by building use: Those of hotels and apartments are generally larger than those of other buildings. However, damping ratios are more widely scattered than natural periods, because they are also affected by vibration amplitude, foundation type, and so on. Frequency and amplitude dependencies of damp...

Plastic analysis and design of steel plate shear walls

Abstract: A revised procedure for the design of steel plate shear walls is proposed. In this procedure the thickness of the infill plate is found using equations that are derived from the plastic analysis of the strip model, which is an accepted model for the representation of steel plate shear walls. Comparisons of experimentally obtained ultimate strengths of steel plate shear walls and those predicted by plastic analysis are given and reasonable agreement is observed. Fundamental plastic collapse mechanisms for several, more complex, wall configurations are also given. Additionally, an existing codified procedure for the design of steel plate walls is reviewed and a section of this procedure which could lead to designs with less-than-expected ultimate strength is identified. It is shown that the proposed procedure eliminates this possibility without changing the other valid sections of the current procedure.

Shear Capacity of Fiber-Reinforced Polymer-Strengthened Reinforced Concrete Beams: Fiber Reinforced Polymer Rupture

Abstract: A recent innovation in shear strengthening of reinforced concrete beams is to externally bond fiber-reinforced polymer (FRP) composites. Many studies have been undertaken on this strengthening technique. These studies have established clearly that such strengthened beams fail in shear mainly in one of the two modes: FRP rupture and FRP debonding, and have led to preliminary design proposals. This paper is concerned with the development of a simple, accurate, and rational design proposal for the shear capacity of FRP-strengthened beams which fail by FRP rupture. To this end, existing design proposals are reviewed, and their efficiencies highlighted. A new strength model is then developed, which recognizes the fundamental characteristics of FRP. The model is validated against experimental data collected from the existing literature. Finally, a new design proposal is presented.

Uniaxial Confinement Model for Normal- and High-Strength Concrete Columns

Abstract: This paper presents a new confinement model based on strain compatibility and transverse force equilibrium. This new approach is capable of predicting the effectiveness of transverse reinforcement, which is key in modeling the behavior of high-strength concrete confined with high-yield-strength steel. The model is validated on test results from more than 200 circular and square large-scale columns tested under slow and fast concentric loading. In addition, results from about 50 square and circular large-scale columns tested under constant axial load and reversed cyclic bending were also used in the assessment of the model adaptability to seismic-type loading. All the predictions are in very good agreement with the experimental results. The model is especially effective in assessing the effectiveness of high-yield-strength steel.

Phase i benchmark control problem for seismic response of cable-stayed bridges

Abstract: This paper presents the problem definition for the first generation of benchmark structural control problems for cable-stayed bridges. The benchmark problem is based on the Bill Emerson Memorial Bridge that is currently under construction in Cape Girardeau, Missouri. Construction of the bridge is expected to be completed in 2003. The goal of this study is to provide a testbed for the development of strategies for the control of cable-stayed bridges. Based on detailed drawings, a three-dimensional evaluation model has been developed to represent the complex behavior of the full scale benchmark bridge. The linear evaluation model is developed using the equations of motion generated around the deformed equilibrium position. Evaluation criteria are selected that are consistent with the goals of seismic response control of a cable-stayed bridge. Control constraints ensure that the results are representative of a control implementation on the physical structure. Each participant in this benchmark study is given...

Strengthening of Steel-Concrete Composite Girders using Carbon Fiber Reinforced Polymers Sheets

Abstract: The use of advanced composite materials for rehabilitation of deteriorating infrastructure has been embraced worldwide. The conventional techniques for strengthening of substandard bridges are costly, time consuming, and labor intensive. Many new techniques have used the lightweight, high strength, and the corrosion resistance of fiber reinforced polymers ~FRP! laminates for repair and retrofit applications. The load-carrying capacity of a steel-concrete composite girder can be improved significantly by epoxy bonding carbon fiber reinforced polymers ~CFRP! laminates to its tension flange. This paper presents the results of a study on the behavior of steel-concrete composite girders strengthened with CFRP sheets under static loading. A total of three large-scale composite girders made of W355313.6 A36 steel beam and 75-mm thick by 910-mm wide concrete slab were prepared and tested. The thickness of the CFRP sheet was constant and a different number of layers of 1, 3, and 5 were used in the specimens. The test results showed that epoxy-bonded CFRP sheet increased the ultimate load-carrying capacity of steel-concrete composite girders and the behavior can be conservatively predicted by traditional methods.

Life-cycle reliability-based maintenance cost optimization of deteriorating structures with emphasis on bridges

Abstract: The assessment of the current state and the prediction of the future condition of deteriorating structures are crucial processes in the management of civil infrastructure systems. Not only time-varying loads and resistances but also a series of maintenance interventions that are applied to keep structural systems safe and serviceable make the prediction process very difficult. In order to perform a realistic life-cycle analysis of deteriorating structures under different maintenance scenarios the uncertainties involved in this process have to be considered. This paper considers these uncertainties by providing a reliability-based framework and shows that the identification of the optimum maintenance scenario is a straightforward process. This is achieved by using a computer program for Life-Cycle Analysis of Deteriorating Structures (LCADS). This program can consider the effects of various types of actions on the reliability index profile of a group of deteriorating structures. Only the effect of maintena...

Steel-Concrete Composite Beams Considering Shear Slip Effects

Abstract: The present study investigated the effects of shear slip on the deformation of steel-concrete composite beams. The equivalent rigidity of composite beams considering three different loading types was first derived based on equilibrium and curvature compatibility, from which a general formula to account for slip effects was then developed. The predicted results were compared with measurements of six specimens tested in the present study and other available test results for both simply supported and continuous beams. It was found that including slip effects has significantly improved the accuracy of prediction. For typical beams used in practice, shear slip in partial composite beams has a significant contribution to beam deformation. Even for full composite beams, slip effects may result in stiffness reduction up to 17% for short span beams. However, slip effects are ignored in many design specifications that use transformed section method except that American Institute of Steel Construction ~AISC! specifications recommend a calculation procedure in the commentary. In the AISC procedure, stress and deflection calculations of partially composite girders are based on effective section modulus and moment of inertia to account for slip, while ignoring slip effects in full composite sections. For full composite sections, the effective section modulus and moment of inertia calculated with the AISC specifications are larger than that of present study, meaning that the specifications are not on the conservative side. For partial composite sections, the AISC predictions are more conservative than the present study.

Experimental Study on Steel Shear Wall with Slits

Abstract: A new type of earthquake-resisting element, consisting of a steel plate shear wall with vertical slits, is introduced. In this system, the steel plate segments between the slits behave as a series of flexural links, which provide a fairly ductile response without the need for heavy stiffening of the wall. Test results are presented for 42 wall plate specimens of roughly one-third of full scale, which were subjected to static monotonic and cyclic lateral loading. These tests provide data on general behavior of the walls, which provides the basis for models to calculate the wall strength and stiffness and design the out-of-plane stiffening. When properly detailed and fabricated to avoid premature failure due to tearing or out-of-plane buckling, the wall panels respond in a ductile manner, with a concentration of inelastic action at the top and bottom of the flexural links. The test data indicate that limiting the width-to-thickness ratio to less than 20 in the flexural links will ensure that the walls can sustain roughly 3% drift without substantial hysteretic degradation.

Effect of Strength and Fiber Reinforcement on Fire Resistance of High-Strength Concrete Columns

Abstract: In this paper, results from fire resistance experiments on five types of reinforced concrete columns are presented. The variables considered in the study include concrete strength [normal-strength concrete (NSC) and high-strength concrete (HSC)], aggregate type (siliceous and carbonate aggregate), and fiber reinforcement (steel and polypropylene fibers). Data from the study is used to determine the structural behavior of HSC columns at elevated temperatures. A comparison is made of the fire resistance performance of HSC columns with that of NSC and fiber-reinforced HSC columns. The factors that influence the thermal and structural behavior of HSC concrete columns under fire conditions are discussed. The results show that the fire resistance of a NSC column is higher than that of a HSC column. Also, the addition of polypropylene fibers and the use of carbonate aggregate improve fire resistance.

Seismic response of concentrically braced steel frames made with rectangular hollow bracing members

Abstract: This paper describes an experimental study on the seismic performance of concentrically braced steel frames made with cold-formed rectangular tubular bracing members. A total of 24 quasistatic cyclic tests were performed on full size X bracing and single diagonal bracing systems. Two loading sequences were considered: a symmetrical stepwise increasing deformation sequence and a displacement history obtained from nonlinear dynamic analyses of typical braced steel frames. All specimens buckled out-of the plane of the frame and the tests were interrupted when fracture of the braces occurred in the region of highest curvature. For X bracing, the results clearly show that the effective length of the braces can be used to determine their compression strength and to characterize their hysteretic response, including energy dissipation capability. Simplified models are proposed to predict the out-of-plane deformation of the braces as a function of the ductility level. These models are then used to develop an empir...

Flexural Design of Reinforced Concrete Frames Using a Genetic Algorithm

Abstract: A design procedure implementing a genetic algorithm is developed for discrete optimization of reinforced concrete frames ~RC-GA!. The design procedure conforms to the American Concrete Institute ~ACI! Building Code and Commentary. The objective of the RC-GA procedure is to minimize the material and construction costs of reinforced concrete structural elements subjected to serviceability and strength requirements described by the ACI Code. Examples are presented demonstrating the efficiency of theRC-GA procedure for the flexural design of simply-supported beams, uniaxial columns, and multi-story frames.

Experimental Study and Calculation of Fire Resistance of Concrete-Filled Hollow Steel Columns

Abstract: Hollow structural steel (HSS) columns filled with concrete offer a number of benefits and are often used in tall buildings and other industrial structures. A mathematical model was developed and used to investigate the influence of important parameters that determine the fire resistance of concrete-filled hollow steel columns. The behavior of concrete-filled HSS columns with or without fire protection subjected to axial or eccentric loads was experimentally investigated and the results presented in this paper. The parametric and experimental studies provide information for the development of formulas for the calculation of the fire resistance and fire protection thickness of the composite columns. The main objectives of this work were threefold: First, to report a series of fire tests on composite columns; second, to analyze the influence of several parameters, such as the sectional dimension, load eccentricity ratio, and fire protection thickness on the fire resistance of the composite columns. It was fo...

Control of seismically excited cable-stayed bridge employing magnetorheological fluid dampers

Abstract: This paper examines the ASCE first generation benchmark problem for a seismically excited cable-stayed bridge, and proposes a new semiactive control strategy focusing on inclusion of effects of control-structure interaction. The subject of the ASCE benchmark problem is a cable-stayed bridge in Cape Girardeau, Missouri, for which construction is expected to be completed in 2003. The goal of the benchmark study is to provide a \Itestbed\N structure on which researchers can systematically compare and evaluate the relative merits of proposed structural protection for cable stayed-bridges. In this paper, magnetorheological (MR) fluid dampers, which belong to the class of controllable fluid dampers, are proposed for use in a control strategy for protecting the bridge. A clipped-optimal control algorithm, shown to perform well in previous studies involving MR fluid dampers, is employed. A comprehensive study of the adequacy of various types of dynamic models for MR fluid dampers, such as a Bingham model, a Bouc-Wen model, and a modified Bouc-Wen model, is provided. In contrast to previous studies, models considered in this study are based on experimental data for a full-scale MR fluid damper. Because the MR fluid damper is a controllable energy-dissipation device that cannot add mechanical energy to the structural system, the proposed control strategy is fail-safe in that bounded-input, bounded-output stability of the controlled structure is guaranteed. Numerical simulation results considering several historical earthquakes scaled to various magnitudes show that the proposed semiactive control strategy using MR fluid dampers is the promising one of the applicable control methods to reduce seismic responses of cable-stayed bridges.

Flexural Design of Reinforced Concrete Frames by Genetic Algorithm

Abstract: A genetic algorithm is used to perform the discrete optimization of reinforced concrete plane frames subject to combinations of gravity loads and lateral loads. Difficulties in finding optimum sections from a semi-infinite set of member sizes and reinforcement arrangements are alleviated by constructing data sets, which contain a finite number of sectional properties of beams and columns in a practical range. Construction practice is also implemented by linking columns and beams by group and by considering “connectivity” between columns located in the same column line. It is shown that the developed genetic algorithm obtained an optimal design for reinforced concrete plane frames.

Study on Damping Reduction Factor for Buildings under Earthquake Ground Motions

Abstract: This paper discusses the rationality of the design force and damping reduction factors adopted by a few seismic design provisions for buildings with and without added passive energy dissipation systems. The issue will first be pointed out that the damping reduction factors adopted by those provisions are derived from the effects of viscous damping on displacement responses, but are used to reduce the design force of buildings. Statistical results from 1053 ground motions recorded in the U.S. show that it may lead to unconservative results, especially for systems with damping ratios greater than 10% and periods longer than 0.15 s. Furthermore, although there is no doubt that the additions of extra damping to a structure will always reduce the displacement responses, many documents argue the effect of added damping to reduce the force responses of the buildings. Therefore, this paper also addresses the effects of viscous damping on the inertial force and elastic restoring force in order to use the damping reduction factors correctly. Results of this study suggest that if the damping of structures comes from the hysteretic response of the building, the design force of the structures should be the inertial force and the damping reduction factors should be derived from the acceleration responses. Otherwise, if the additional damping of structures comes from the added energy dissipation devices, the design force should be the restoring force and the damping reduction factors should be derived from the displacement responses.

Retrofit of reinforced concrete columns using partially stiffened steel jackets

Abstract: This paper introduces an improved steel jacketing method to retrofit reinforced concrete columns with a square or rectangular section for enhanced strength and improved ductility. To retrofit an existing column, relatively thin steel plates were welded to form a rectilinear jacket for shear strength enhancement, and then additional confinement elements (stiffeners) with various types of desired configurations were welded to the potential plastic hinge regions to ensure a ductile behavior. A rational retrofit design procedure was suggested and evaluated through an experimental program. Five 1/3 scale model columns were tested under constant axial load of 0.3Agfc′ and cyclic lateral force in a double-curvature condition. Test results validated the efficiency of the partially stiffened rectilinear steel jacketing, which not only prevented brittle shear failure but also greatly improved the ductility of the column with achieving an ultimate drift ratio of more than 8%. Besides the structural merits, the parti...

Cyclic testing of built-up steel shear links for the new bay bridge

Abstract: Tests were conducted on two prototype steel shear links for the main tower of the new San Francisco-Oakland Bay self-anchored suspension bridge to evaluate the link force and deformation capacities. The links were built-up wide-flange sections, designed to yield in shear. A quasi-static loading protocol was used to test the links in reverse curvature, simulating the expected seismic demand. The link capacities exceeded the predicted demands from the Safety Evaluation Earthquake. The specimens behaved in a ductile manner until small cracks initiated at the end of the vertical fillet welds connecting the intermediate stiffeners to the link web. As the cracks propagated further, brittle fracture of the web ensued. The maximum shear strength was nearly twice the expected yield shear strength, a significantly higher overstrength than current codes recognize. Alleviating the stress concentration on the vertical fillet welds of the intermediate web stiffeners is necessary to avoid brittle fracture and to increas...

Local Buckling Tests on Cold-Formed Steel Beams

Abstract: \iC and \iZ sections are two of the most common cold-formed steel shapes in use today. Accurate prediction of the bending performance of these sections is important for reliable and efficient cold-formed steel structures. Recent analytical work has highlighted discontinuities and inconsistencies in the American Iron and Steel Institute (AISI) and Canadian Standards Association (S136) design provisions for stiffened elements under a stress gradient (i.e., the web of \iC or \iZ sections). New methods have been proposed for design, and an interim method has been adopted in the North American Specification (NAS). However, existing tests on \iC and \iZ sections do not provide a definitive evaluation of the design expressions, due primarily to incomplete restriction of the distortional buckling mode. Described in this paper is a series of flexural tests with details selected specifically to insure that local buckling is free to form, but distortional buckling and lateral-torsional buckling are restricted. The members selected for the tests provide systematic variation in the web slenderness (\Ih/t\N) while varying other relevant nondimensional parameters (i.e., \Ih/b, b/t, d/t, d/b\N). Initial analysis of the completed testing indicates that overall test-to-predicted ratios for AISI, S136, NAS, and the direct strength method are all adequate, but systematic differences are observed.

Local buckling of fiber reinforced plastic composite structural members with open and closed cross sections

Abstract: The local buckling analysis of fiber reinforced plastic (FRP) composite open and closed thin-walled section beams and columns is presented. Explicit expressions are developed for axially loaded and...

Aerodynamic Loads on Tall Buildings: Interactive Database

Abstract: Under the action of wind, tall buildings oscillate simultaneously in the alongwind, acrosswind, and torsional directions. While the alongwind loads have been successfully treated using quasi-steady and strip theories in terms of gust loading factors, the acrosswind and torsional loads cannot be treated in this manner, since these loads cannot be related in a straightforward manner to the fluctuations in the approach flow. Accordingly, most current codes and standards provide little guidance for the acrosswind and torsional response. To fill this gap, a preliminary, interactive database of aerodynamic loads is presented, which can be accessed by any user with Microsoft Explorer at the URL address http://www.nd.edu/;nathaz/. The database is comprised of high-frequency base balance measurements on a host of isolated tall building models. Combined with the analysis procedure provided, the nondimensional aerodynamic loads can be used to compute the wind-induced response of tall buildings. The influence of key parameters, such as the side ratio, aspect ratio, and turbulence characteristics for rectangular sections, is also discussed. The database and analysis procedure are viable candidates for possible inclusion as a design guide in the next generation of codes and standards.

System Reliability Assessment by Method of Moments

Abstract: The computational assessment of system reliability of structures has remained a challenge in the field of reliability engineering. Calculation of the failure probability for a system is generally difficult even if the potential failure modes are known or can be identified, because available analytical methods require determination of the sensitivity of performance functions, information on mutual correlations among potential failure modes, and determination of design points. In the present paper, a method based on moment approximations is proposed for structural system reliability assessment that is applicable to both series and nonseries systems. The point estimate method is applied to evaluate the first few moments of the system performance function of a structure from which the moment-based reliability index and failure probability can be evaluated without Monte Carlo simulations. The procedure does not require the computation of derivatives, nor determination of the design point and computation of mutual correlations among failure modes; thus, it should be computationally effective for structural assessment of system reliability.

Modeling Membrane Action of Concrete Slabs in Composite Buildings in Fire. I: Theoretical Development

Abstract: A nonlinear layered finite element procedure for predicting the structural response of reinforced concrete slabs subjected to fire is described. The proposed procedure is based on Mindlin/Reissner (thick plate) theory, and both geometric and material nonlinearities are taken into account. The complications of structural behavior in fire conditions, such as thermal expansion, cracking or crushing, and change of material properties with temperature are modeled. In this study a total Lagrangian approach is adopted throughout, in which displacements are referred to the original configuration and small strains are assumed. A numerical example, in which a rectangular reinforced concrete slab is modeled at elevated temperatures, is presented. The influences of different thermal expansion characteristics, tensile membrane action, and differential temperature distributions across the thickness of the slab are investigated. It is evident that the nonlinear layered procedure proposed in this paper can properly model...