Journal of Structural Engineering

A simple method to obtain the load distribution on the resisting elements of symmetric and eccentric setback structures subjected to lateral loading is presented. The compatible load concept is employed by the proposed method to subdivide the loading into load components, both translational and torsional. The proportional stiffness rule of force distribution can then be applied to each load component. In addition to being a practical design tool, the proposed procedure also provides an understanding of the load transfer mechanism involved in setback structures, especially in the region where the setback occurs and complication in behavior is expected. Three numerical examples are presented to illustrate the procedure and provide an insight on the load distribution pattern of such structures.

A new one‐dimensional model for random cyclic compression in concrete is developed. The model determines several geometrical loci in the uniaxial stress‐strain plane that govern the unloading‐reloading curves. The model laws for reproducing the unloading and reloading curves are presented, by which the curves may be plotted graphically with no accompanying calculations. Comparisons of the model predictions with many test results show good agreement.

A simple model for the lateral behavior of wood‐framed shear walls with stud uplifting is presented. The single‐story wall has five degrees of freedom: (1) the shear rotation of the frame; (2) two relative rotations of the sheathings; (3) the uplifting of the windward stud; and (4) the uplifting of the windward panel. For walls of two or more stories, two additional degrees of freedom are introduced for relative rotations of the sheathings in higher stories, bringing the total unknowns to seven. Results from this model are compared with the available test results. The present model is also able to show the dependence of the load‐deflection curve on the vertical load.

A simple model is presented for analyzing wood‐framed houses subjected to lateral forces from wind and earthquake. The model has been applied to the analysis of a wood‐framed house at five stages of its construction. A good and consistent agreement between the analytical and the test results is shown. The paper also presents the process through which the final model was developed. A major part of the effort went into perfecting the shear wall behavior that would be suitable for the house analysis. The earlier shear wall models that did not include any uplifting or that included the uplifting in studs only did not represent the behavior adequately. In order to achieve agreement between the test and the analysis results, it was necessary for the shear wall model to allow uplifting of sole plate also.

The first‐order second‐moment (FOSM) method and the advanced second‐moment (ASM) method are used to determine partial safety factors. Design formats based on these methods may result in engineering designs with reliability levels that are different from the ones specified in developing the design formats. The FOSM and ASM methods are evaluated in this paper, and reliability‐conditioned (RC) method is proposed in this paper. The proposed method overcomes the shortcomings of the FOSM and ASM methods, and is believed to result in partial safety factors which give engineering designs reliability levels equal to the specified ones. The calibration of existing codes can be accomplished easily by determining the safety levels of the current designs first and then the required partial safety factors for the new design format to give the same safety levels can be determined.

A rectangular plate element with rectangular cutouts was developed. The stiffness matrix of the element is formed by numerical integration in which the region of the cutout in the element is excluded during the integration process. The behavior of the newly developed element is very good, based upon comparisons with the results from a well‐established finite element program. This element can be used effectively and economically in the analysis of perforated shear walls, especially in the analysis of the integrated behavior of the entire structure.

A diagonal compression field theory was extended to study the postcracking behavior of reinforced concrete sections subjected to combined axial force, biaxial bending, and torsion. The theory assumes that when concrete cracks are formed by the torsion, the reinforced concrete member becomes a hollow section with varied wall thickness, which is then discretized into a wall element system. With the consideration of equilibrium and compatibility conditions, the theory converts the problem to that of solving a system of nonlinear equations. An examination of the model's response in limiting loading cases indicated that the proposed method provides a single model unifying the pure torsion and pure bending theories. The proposed theory was calibrated with experimental data for combined bending and torsion of both rectangular and slab sections. The comparison indicated that the post‐cracking behavior is in general well predicted by the model. The proposed theory can be employed to determine the moment/curvature and torsion/twist responses of general reinforced concrete sections subjected to combined loadings.

A simple method for the problem of uniaxially loaded orthotropic plates is presented. The analysis is approximate and is based on the energy method. It is free from tedious calculations such as those encountered when the large deflection theory is used. Formulas are derived for effective widths of plate with two different boundary conditions: (1) the two unloaded edges restrained against in‐plane displacement in the transverse direction; and (2) the two unloaded edges free to pull in transversely. Effective width curves for orthotropic plates having various elastic properties are presented.

A vertical shear connector suitable for manufacture by automated sheet metal processes from steel coil is developed in an experimental program involving 90 small area bearing tests, 18 shear tests, and 6 tension tests. A comparison of three full‐scale wall panel tests (standard cavity wall, cavity wall with an unbonded steel mullion, and cavity wall with a vertical shear connector) demonstrate that the connector significantly increases both the post‐ and pre‐cracking strength and stiffness of a vertically spanning brick masonry cavity wall under out‐of‐plane loads.

This paper investigates the feasibility of using the three active control mechanisms suggested in the literature for the control of tall buildings against wind forces. These mechanisms are the active tendon mechanism, the active tuned mass damper mechanism, and the aerodynamic appendage mechanism. The paper focuses on the size and behavior of the actuators that are used to implement the designed control law in these mechanisms. The results of investigating other aspects of feasibility such as the time delay effect, the effect of the changes in the structural parameters due to the feedback control force, and the effectiveness of the control mechanism are summarized from previous publications by the writer. By investigating these results, it becomes apparent that using a combined active control mechanism would solve many problems in structural control. From investigating the performance of several combined control mechanisms, it is concluded that a properly designed combined active tendon and active tuned mass damper mechanism would solve many structural control problems.

The static and dynamic behavior of plane frames composed of thinwalled steel members is presented. Frame analysis includes post‐local‐buckling and/or first‐order geometric nonlinearities. Post‐local‐buckling behavior is included using the effective width concept which includes both axial and bending stresses. Direct iteration is used to calculate the effective cross section properties for members that have locally buckled. An “exact” elastic stiffness matrix, finite element geometric stiffness, consistent mass and Rayleigh damping matrix formulation is used to discretize the dynamic equilibrium equations. The nonlinear dynamic equations are solved using a modified Newton‐Raphson iteration strategy coupled with Newmark's time integration scheme. Static and dynamic analyses of a two‐bay, two‐story frame are considered. Static problem results are presented to demonstrate the accuracy of the formulation and the influence of local buckling and/or first‐order geometric nonlinearities. Dynamic simulations are based on subjecting the two‐story, two‐bay frame to a sway pulse loading to simulate wind pressure. The dynamic results include linear elastic, local buckling, and/or first‐order geometric nonlinearity.

ATC3‐06 placed strict limitations on the use of precast prestressed concrete piles in severe seismic regions. Two reasons contributing to the decision were the poor level of understanding of the curvature capacity of such piles and the magnitude of the curvatures which are likely to be imposed on them by a moderate to severe earthquake. This paper describes full‐scale physical experiments to study the former and computer calculations to study the latter. The writers conclude that prestressed concrete piles containing modest amounts of spiral reinforcement should give satisfactory performance in the vast majority of applications on the west coast of the United States, and that the analysis of soil‐pile interaction described here is a useful tool for the design of pile foundations in seismic regions.

This paper attempts to select air optimum appendage design on the basis of the force or power needed to position the appendage. Three different appendage mechanisms were implemented to follow the same control law. It is shown that the mechanism that needs least power or force for its operation should be used in practice. Thus, in general, not only is the optimization of the control process required, but also important is the selection of the optimal mechanism configuration on the basis of the force or power needed for the mechanism operation. The results are shown numerically to control a tall building against wind forces.

A majority of structural failures and associated damage costs are due to errors in planning, design, construction, and utilization, rather than stochastic variability in construction material strengths and structural loads. Recently developed probability‐based load and resistance factor design methods treat uncertainties due to inherent randomness and modeling more rationally than is possible with current design methods, but still do not take errors in design and construction into account. Any meaningful attempts to reduce failure rates will need to deal with this issue. This paper reviews the status of design and construction errors in structural safety studies, summarizes some simple mathematical tools for their analysis, and demonstrates why errors are so difficult to treat in codified design.