Showing papers in "Journal of the Structural Division in 1981"
TL;DR: In this article, a model for aggregate interlock based on the behavior of micro scale is developed, where the relation between displacements and stresses across the crack faces is defined to be a function of deformation and sliding at particle level.
Abstract: A model for aggregate interlock has been developed based on the behavior of micro scale. The relation between displacements and stresses across the crack faces are defined to be a function of deformation and sliding at particle level. This relation is derived for one particle projecting from one of the crack faces with an arbitrary diameter and an arbitrary embedment depth. The most probable distribution of aggregate particles, crossed by the plane of cracking and their positions with regard to this plane are assessed by a statistical analysis. The general relations between stresses and displacements for a unit crack area are obtained by integrating all particle contributions. The model proves to give adequate results, compared with experiments, carried out on several types of (cracked) concrete. Using this model, further analysis of the mechanism of aggregate interlock has been carried out, explaining tendencies observed in tests of other investigators.
429 citations
TL;DR: In this paper, a simple analytical model for the calculation of the seismic displacement history response of reinforced concrete frame and frame-wall structures is developed, which is idealized as a single-degree system consisting of a mass mounted on a rigid bar connected to the ground by a hinge and a nonlinear rotational spring.
Abstract: A simple analytical model is developed for the calculation of the seismic displacement history response of reinforced concrete frame and frame-wall structures. The computer cost for the model is approximately three precent of that for a MDOF system. A structure is idealized as a single-degree system consisting of a mass mounted on a rigid bar connected to the ground by a hinge and a nonlinear rotational spring. The primary force-deformation relationship for the spring is obtained by a static analysis of the multistory structure. To account for stiffness changes during an earthquake, a simple hysteresis model comprising only four rules is developed. The model is examined for eight small-scale ten-story reinforced concrete test structures, and the analytical results are compared with the measured response histories. The model is shown to be successful in most instances.
223 citations
TL;DR: In this paper, the authors developed analytical models which can reproduce the behavior of reinforced concrete members under cyclic loads and checked the accuracy of the analytical models by considering a set of quasi-static cyclic load tests, and the models were found to be sufficiently accurate.
Abstract: Seismic damage in reinforced concrete frames is predicted by analytical methods. Analytical models are developed which can reproduce the behavior of reinforced concrete members under cyclic loads. Accuracy of the analytical models is checked by considering a set of quasi-static cyclic load tests, and the models are found to be sufficiently accurate. Several damage indicators such as ductility, flexural damage ratio, dissipated energy, and cumulative plastic rotation are investigated for each experiment. Based on the test results and physical grounds, flexural damage ratio and dissipated energy are chosen as damage state parameters. The results of the present study are later used to develop a probabilistic model of member failure in reinforced concrete structures.
196 citations
TL;DR: In this article, the reliability of two representative procedures is evaluated, inelastic design response spectra are obtained by modifying a linear elastic design response spectrum in terms of a specified ductility factor as suggested by Newmark and Hall and the Applied Technology council.
Abstract: After reviewing general methods available for determining seismic design forces for structures which can tolerate limited amounts of inelastic deformations, the reliability of two representative procedures is evaluated. In the methods evaluated, inelastic design response spectra are obtained by modifying a linear elastic design response spectrum in terms of a specified ductility factor as suggested by Newmark and Hall and the Applied Technology council. The effect of different accelerograms, as well as of different system damping and hysteretic characteristics, on the inelastic response of single degree-of-freedom systems designed using these methods is thoroughly investigated, considering maximum displacement ductilities, maximum and permanent drifts, number of yield events, and hysteretic energy dissipation. Application of these design methods to multistory buildings is also briefly considered. Results obtained for ideal inelastic systems indicate that these methods do not reliably limit displacement ductilities to specified values.
176 citations
TL;DR: In this article, a probabilistic model is developed that gives the distribution of peak response of buildings modified by adding a tuned mass damper in terms of the same distribution for the unmodified structures.
Abstract: Time history analysis of 1DOF systems with and without a tuned mass damper, subjected to a set of historical earthquakes, shows that the peak response ratio (ratio between the peak responses with and without damper) depends primarily on damping constants and on earthquake duration The same analysis reveals that response ratio values are widely scattered and that the mean response ratio in underestimated by conventional stationary random vibration calculations Improvement is obtained by considering response movement and broadening of the response spectral density function caused by the damper Based on these considerations, a probabilistic model is developed that gives the distribution of peak response of buildings modified by addition of a tuned mass damper in terms of the same distribution for the unmodified structures For elastic systems tuned mass dampers have small antiseismic effectiveness
171 citations
TL;DR: In this article, the behavior of outrigger-braced tall building structures is studied taking into account the flexibility of the outriggers, and expressions for the core moment distribution, the top drift and the optimum location of the outsriggers for minimum top drift are developed.
Abstract: The behavior of outrigger-braced tall building structures is studied taking into account the flexibility of the outriggers. Expressions are developed for the core moment distribution, the top drift and the optimum location of the outriggers for minimum top drift. A characteristic non-dimensional parameter is developed that takes into account the core-to-column and core-to-outrigger flexural rigidity ratios. Graphs are plotted as functions of the characteristic parameter which allow the determination of the optimum outrigger levels for minimum drift and the corresponding core base momnet for structures with up to four outriggers. The study is based on the assumption of a uniform structure and uniform horizontal distributed loading.
108 citations
TL;DR: In this article, the finite strip method was extended to include the nonlinear response of imperfect plate strips under axial compression, and the convergence and accuracy of the method was tested against accepted solutions for uniformly compressed plates with different boundary conditions.
Abstract: The finite strip method developed by Cheung is extended to include the nonlinear response of imperfect plate strips under axial compression. Local buckling and postbuckling phenomena are included in the formulation. The convergence and accuracy of the method is tested against accepted solutions for uniformly compressed plates with different boundary conditions. Studies are made of the nonlinear response of box and I-section columns. The application of the method to the interaction of local and Euler buckling of straight columns with imperfect plates is presented.
90 citations
TL;DR: In this paper, the effects of torsional coupling on the earthquake response of simple one-story structures in elastic and inelastic ranges of behavior were analyzed, and the response quantities were presented including maximum lateral and torsion deformations of the system as well as maximum deformation of individual columns.
Abstract: The effects are analyzed of torsional coupling on the earthquake response of simple one-story structures in elastic and inelastic ranges of behavior. The structures considered are symmetrical about one principal axis of resistance, resulting in coupling only between lateral displacement along the perpendicular axis and the torsional displacement. Torsional coupling arising only from eccentricity between centers of mass and elastic resistance is considered. Systems with several resisting elements are idealized by a single element model. Response of such a model to a selected earthquake ground motion are presented for a range of the basic structural parameters. The response quantities presented include maximum lateral and torsional deformations of the system as well as maximum deformations of individual columns. The response in the inelastic range of behavior is effected by torsional coupling to generally a lesser degree than elastic response.
90 citations
TL;DR: An approximate finite element method is developed for analyzing the distortional buckling of doubly symmetric I-section beam-columns and the convergence and accuracy of the buckling solutions are demonstrated.
Abstract: An approximate finite element method is developed for analyzing the distortional buckling of doubly symmetric I-section beam-columns. The method allows an analysis to be made of elastic uniform members under various conditions of loading, end support, and restraint. A computer program based on this finite element method is described, and the convergence and accuracy of the buckling solutions are demonstrated. The method is then used to investigate the significance of different end conditions on the elastic buckling of I-beams under uniform moment.
77 citations
TL;DR: In this paper, the cross-wind response amplitudes were determined from the response characteristics of a structure above which the response can not be accounted for by the random wake excitation process and that lock-in excitation is significant.
Abstract: Circular and square tower models were tested in a boundary layer wind tunnel. At close to the critical reduced velocity and particularly at low values of structural damping, displacement dependent lock-in excitation was found to cause large increases in cross-wind displacement response, especially for the circular tower, in a suburban type wind model. Critical cross-wind response amplitudes were determined from the response characteristics. These response amplitudes represent the level of cross-wind response of a structure above which the response can not be accounted for by the random wake excitation process and that lock-in excitation is significant. A prediction procedure, which consists of a random excitation model and a sinusoidal lock-in excitation model, is described. Cross-wind response predicted by these models agreed well with the measured response.
74 citations
TL;DR: In this paper, an effective width approach is presented for predicting ultimate strength of thin-walled compression elements with edge stiffeners, and a requirement for adequate stiffener rigidity is given.
Abstract: An effective width approach is presented for predicting ultimate strengths of thin-walled compression elements with edge stiffeners. In conjunction with procedures for predicting ultimate strengths, a requirement for adequate stiffener rigidity is given. Stiffener adequacy is assessed as that stiffener rigidity for which the ultimate strength of an edge-stiffened element equals that of an element of similar dimensions and material properties but supported by a web at the stiffener location. Critical and post-critical behavior of the assembly are studied analytically and experimentally; however, the stiffener requirement is based primarily on the experimental results. Simple formulations for assessing the performance of the stiffener and plate elements are presented.
TL;DR: In this article, the inelastic behavior of axially loaded steel struts subjected to repeated buckling and stretching was investigated and the effects of loading patterns, end conditions, cross-sectional shapes, and slenderness ratios on the hysteresis response of members were investigated.
Abstract: An experimental study is presented of the inelastic behavior of axially loaded steel members subjected to repeated buckling and stretching. Tests on 24 commercially available steel struts commonly used as bracing members are reported. A large variety of shapes were tested including wide flanges, structural tees, double-angles, a double-channel, and thick and thin-walled square and round tubes. The boundary conditions were of two types, pinned-pinned and fixed-pinned, while the effective slenderness ratios were either 40, 80, or 120. The effects were investigated of loading patterns, end conditions, cross-sectional shapes, and slenderness ratios on the hysteresis response of members. An explanation is given regarding the fundamental mechanisms responsible for the observed degradation in the buckling load capacity during inelastic cycling.
TL;DR: In the development of these formulas, simplified models for scabbing and for perforation were assumed; engineering mechanics principles were applied in the formulation, and the Bayesian statistics were utilized to determine coefficients in these formulas.
Abstract: Semianalytical formulas are developed to predict scabbing and perforation thicknesses for reinforced concrete panels subjected to impacts by solid steel missiles. The scabbing thickness is defined as the thickness that is just enough to prevent the peeling off of the back face of the panel opposite to the face of impact; perforation thickness is defined as the thickness that is just enough to allow a missile to pass through the panel without exit velocity. In the development of these formulas, simplified models for scabbing and for perforation were assumed; engineering mechanics principles were applied in the formulation, and the Bayesian statistics were utilized to determine coefficients in these formulas. The Bayesian approach was used because it can handle the estimation of parameters better than the classicial statistical method when suitable data are limited, as is presently the case in low velocity missile impact on concrete panels.
TL;DR: In this article, an interior penalty function is used to convert the original constrained problem into an unconstrained parametric problem, and then the search for the optimal solution to the parametric problems is based on a discrete direction gradient.
Abstract: A new method for solving discrete structural optimization problems is presented. An interior penalty function is used to convert the original constrained problem into an unconstrained parametric problem. Then the search for the optimal solution to the parametric problem is based on a discrete direction gradient. Solving an appropriate sequence of these unconstrained parametric problems is equivalent to solving the original constrained optimization problem. This method is illustrated first on a small reinforced concrete problem, and then to the design of steel building frames which are made up of standard sections. Results for a one-story four-bay unsymmetrical frame and an eight-story three-bay symmetrical frame are described.
TL;DR: In this paper, a minimum weight design of trusses is considered by including sizing and configuration variables simultaneously in the design space, and second-order Taylor series expansions of displacement quantities are used along a search direction to avoid large numbers of complete structural analyses.
Abstract: A minimum weight design of trusses is considered by including sizing and configuration variables simultaneously in the design space. Second-order Taylor series expansions of displacement quantities are used along a search direction in order to avoid large numbers of complete structural analyses. Disjoint feasible regions are recognized. Side constraints on nodal coordinates are used to avoid analyses for structures with statically unstable configurations. A primal-dual method, called the multiplier method, is employed as an optimization tool.
TL;DR: In this paper, the authors conducted strength and load reversal tests on reinforced concrete beam-column connections and found that satisfactory load reversal behavior can be achieved if the shear stress in the connection is about half of the monotonic shear strength.
Abstract: Strength and load reversal tests were conducted on reinforced concrete beam-column connections. Fourteen tests investigated the influence of the column axial compressive stress, the amount of hoop reinforcement in the connection, the size and location of transverse beams, and the geometry of the connection region. The test results indicate that the current state-of-the-art design procedure underestimates the capabilities of concrete in the beam-column connection and overestimates the contribution of hoop reinforcement in the connection. It appears that satisfactory load reversal behavior can be achieved if the shear stress in the connection is about half of the monotonic shear strength.
TL;DR: In this article, an analysis program was developed to account for the nonlinear flexibility of the girder-column connections as well as for the response to variable load histories, and the results showed the importance of including actual connection behavior for realistic prediction of sway and internal forces.
Abstract: Various simplifying assumptions, commonly used in the design of unbraced multistory steel building frames, are explored. An analysis program was developed to account for the nonlinear flexibility of the girder-column connections as well as for the response to variable load histories. Analyses were performed on three different structures. The results show the importance of including actual connection behavior for realistic prediction of sway and internal forces. The possibility of the occurrence of alternating connection plasticity is also pointed out. The inclusion of linearly-elastic connection flexibilities in the analysis appears to lead to very satisfactory results.
TL;DR: A review of the different types of shear reinforcement for concrete flate plates is presented and the difficulties encountered when these are used in practice are reviewed in this paper, where the size and shape of the anchors are examined as well as the arrangement of the shear elements around the column.
Abstract: A review of the different types of shear reinforcement for concrete flate plates is presented and the difficulties encountered when these are used in practice are reviewed. Practical shear reinforcement should efficienty increase the shear strength and ductility of the slab-column connection, and should be easy to fabricate and install. New Type of shear reinforcement which satisfies these requirements is presented. An individual reinforcing element is in the form of vertical bars with mechanical anchorages at the two ends. The size and shape of the anchors are examined as well as the arrangement of the shear elements around the column. From the results of 40 full-size tests, rules for the design of the new type of shear reinforcement are given in the form of suggested revisions to the current codes.
TL;DR: In this article, a design method based on the SSRC column curves is proposed to account for the effects of interaction buckling in I-section columns and compared with the tests performed by Kalyanaraman, Pekoz, and Winter.
Abstract: The interaction between local and Euler buckling in an imperfect I-section column produces an adverse effect on its strength. Analytical models based on the effective section method and the finite strip method which account for interaction buckling are compared with tests performed by Kalyanaraman, Pekoz, and Winter (1977). A design method based on the SSRC column curves is proposed to account for the effects of interaction buckling in I-section columns. This design method is also compared with the tests.
TL;DR: In this article, an initial approximate method is presented to evaluate the shear lag phenomenon in reinforced concrete single-box girder bridges, assuming an ideal cross-section and considering a symmetrical deformation of the top and bottom slabs, but preserving continuity conditions at the web-slab intersection points.
Abstract: An initial approximate method is presented to evaluate the shear lag phenomenon in reinforced concrete single-box girder bridges. Assuming an ideal cross-section and considering a symmetrical deformation of the top and bottom slabs, but preserving continuity conditions at the web-slab intersection points, a fourth order non-homogeneous differential equation with constant coefficients was obtained. Making further simplifications, quick results are obtained for uniformly distributed loads. In spite of all the simplifications these results were in good agreement with the German specifications for shear lag provided that midspan reduction factors are desired. the factors are the most important anyway, because they are valid practically almost for the whole span length.
TL;DR: In this paper, an automated procedure is presented for the optimum design of large frameworks having size, stress and displacement constraints, which is based on a simple redesign procedure that is derived directly from the Kuhn-Tucker conditions.
Abstract: An automated procedure is presented for the optimum design of large frameworks having size, stress and displacement constraints. The main feature of the algorithm is the use of a simple redesign procedure that is based on a generalized optimality criterion derived directly from the Kuhn-Tucker conditions. These conditions define an algorithm for the selection of improved designs for building frames in addition to being the necessary test for optimality. In addition, displacement and stress constraint derivatives are derived for multi-variable elements with several stress components. The energy-based approach for calculating behavior gradients has been extended to include the stess gradients for members of rigid plane frames. This formulation permits gradients to be determined for little cost and thus it complements the efficiency of the new generalized optimality criteria method. The efficiency of the complete algorithm has been demonstrated by optimizing the design for two relatively large frameworks, one having 30 members and the other 105 members.
TL;DR: In this paper, a method for computing the probability distribution of combined, time varying loading on a structure is presented, based on finding a close upper bound to the mean upcrossing rate of a linear combination of scalar load processes.
Abstract: A method for computing the probability distribution of combined, time varying loading on a structure is presented. The point crossing method is based on finding a close upper bound to the mean upcrossing rate of a linear combination of scalar load processes. Both smooth, continuous processes and pulse-type processes are included. The solution is a series of single convolutions of two natural descriptors of the load effect process: the first-order or arbitrary-point-in-time probability distribution and the mean upcrossing rate function. An example of the combination of three load processes is included, and the method is compared with others. Implications for load modeling and a format for combined loads in deterministic design codes are analyzed.
TL;DR: In this paper, the influence of the variations of various imperfection parameters on scattered test points of the lateral buckling is examined and the obtained test results are compared with the writers' previous test results of the rolled beams.
Abstract: Statistical buckling experiments of 34 welded beams for each group of two different lengths are carried out under a concentrated load applied vertically at the midspan of the compressive flange of simply-supported beams. The influences of the variations of the various imperfection parameters on scattered test points of the lateral buckling are examined. The obtained test results are compared with the writers' previous test results of the rolled beams. The main imperfection parameter that highly influences the variation of the ultimate strength of the welded beams is the variable value of the actual full plastic moments, as already mentioned for the rolled beams. The welded beams, however, have a lower ultimate strength in the mean value and large coefficient of variation as compared with the rolled beams. The large variations in the compressive residual stresses and the initial lateral crookednesses in the welded beams may cause the large strength variation in the welded beams.
TL;DR: In this paper, a simple method of computing the contribution of higher modes to the crosswind response is presented, and the results are compared with those of a detailed analysis, which is presented in this paper.
Abstract: In this note, a simple method of computing the contribution of higher modes to the crosswind response is presented, and the results are compared with those of a detailed analysis.
Journal Article•
TL;DR: The ASCE Committee on Loads and Forces on Bridges has studied the information available on bridge loading and made its recommendations as discussed by the authors, which significantly different to current code practice are made for long span traffic loading, braking, fatigue, wind, temperature, earthquake, snow, ice and friction forces.
Abstract: The ASCE Committee on Loads and Forces on Bridges has studied the information available on bridge loading and makes its recommendations. Recommendations significantly different to current code practice are made for long span traffic loading, braking, fatigue, wind, temperature, earthquake, snow, ice and friction forces. Little change is recommended at this time to short span traffic loading and impact.
TL;DR: In this article, a set of tentative load factors for possible use in a future edition of the A58 Standard were developed for structural reliability analyses and probability-based limit states design, which require statistical descriptions of structural load and load effect variables.
Abstract: Structural reliability analyses and probability-based limit states design require statistical descriptions of structural load and load effect variables. Frequently, data are only available for the basic variables (e.g., wind speed, ground snow load, etc.) from which the loads are calculated through mathematical relationships. These distributions have been used to develop a set of tentative load factors for possible use in a future edition of the A58 Standard.
TL;DR: The lateral-torsional buckling behavior of non-prismatic beams is not yet fully documented as discussed by the authors, but a fourth-order differential equation in the angle of twist, B, is obtained, in which the location of the transverse load with respect to the centroid is considered.
Abstract: The lateral-torsional buckling behavior of non-prismatic beams is not yet fully documented. Using the total change in potential energy during buckling, a fourth-order differential equation in the angle of twist, B, is obtained, in which the location of the transverse load with respect to the centroid is considered. Using central finite differences, this equation is transformed to a characteristic matrix eigenvalue equation. Solutions for a number of conventional tapered-beam problems are presented.
TL;DR: In this article, a section of a poststressed twin box concrete bridge is instrumented for continuous recording of temperatures within the concrete and of environmental parameters outside, with the aim of presenting it in the form suitable for analysis of similar bridges for thermal effects.
Abstract: A section of a poststressed twin box concrete bridge is instrumented for continuous recording of temperatures within the concrete and of environmental parameters outside The recorded data are processed with the aim of presenting it in the form suitable for analysis of similar bridges for thermal effects It is found that the necessary data can be represented through only two design variables, namely maximum differential temperature DTMAX and base temperature BT Analytical expressions are derived which give vertical temperature profiles as function of DTMAX and environmental parameter insolation The value of the average temperature is similarly obtained from empirical expressions which are functions of the two design variables and environmental parameter ambient air temperature The derived expressions correlate satisfactorily with the measured data, however further research is required to test the effect on stresses and curvatures A flow chart is given showing main steps in design
TL;DR: In this paper, a specific pull-out test used to determine in-situ concrete compressive strength is analyzed, which consists of a steel disc that is extracted from the structure.
Abstract: A specific pull-out test used to determine in-situ concrete compressive strength is analyzed. This test consists of a steel disc that is extracted from the structure. The finite element analysis considers cracking as well as strain hardening and softening in the pre- and post-failure region, respectively. The aim is to attain a clear insight into structural behavior. Special attention is given to the failure mode. Severe cracking occurs and the stress distribution is very inhomogeneous. However, large compressive forces run from the disc in a rather narrow band towards the support and this constitutes the load-carrying mechanism. The failure is caused by the crushing of the concrete in this region, and not by cracking.
TL;DR: In this paper, a total of 137 ultimate strength tests on simple T, Y, DT, and K tubular joints are used as a basic for development of new ultimate capacity formulas.
Abstract: A total of 137 ultimate strength tests—on simple T, Y, DT, and K tubular joints is used as a basic for development of new ultimate capacity formulas. The data are taken from a variety of sources, and only relatively large geometries are considered. Axial tension, axial compression, in-plane bending, and out-of-plane bending loads are represented. The failure condition is taken as the minimum of either maximum load, first crack load, or load at an excessive deformation limit. Several formulas are recommended to predict the capacity of the different joint and load types. The accuracy of these formulas is then studied in a statistical manner. Predictions of past and present API RP 2A formulas are compared to the same data base. The new relatively simple equations are more consistent in their level of prediction and result in less scatter.