Journal of Structural Engineering

A test program was performed on cold-formed-steel oval hollow sections under axial compression. The test specimens were cold-rolled into oval hollow sections with flat web plates and semicircular flanges. The test program included a total of 28 column specimens that were separated into four series of different cross-sectional dimensions. Each series involved at least six specimens of different lengths to obtain a column curve. The columns were compressed between fixed ends. The overall geometric imperfections of the column specimens were measured prior to testing. The failure modes of the specimens included flexural buckling, local buckling, material yielding, and interaction between local and overall buckling. Material properties of each series at the flat and curved portions were determined from tensile coupon tests. The current design specifications for cold-formed-steel structures do not cover the design of oval hollow sections. Hence, certain assumptions on the calculation of effective width have been made in this study. The test strengths were compared with the design strengths predicted by the North American, Australian/New Zealand, and European specifications for cold-formed-steel structures. The test strengths were also compared with the design strengths predicted by the American Iron and Steel Institute Specification for automotive steel that includes design rules for local instability of sections with curved and straight elements. A reliability analysis was also performed. It is shown that the design strengths predicted by the three specifications are generally conservative.

This paper presents a finite-element (FE) modeling approach to predict the deformation, softening, and failure of compression-loaded aluminum structures exposed to fire. A fully coupled thermal-mechanical FE model is outlined. The FE model can analyze the thermal profile and deformation as well as the initial and final plastic collapse of aluminum structures in fire. It calculates the temperature profile of an aluminum structure exposed to unsteady-state heating conditions representative of fire. Using the temperature profile, the elastic and plastic deformations together with the loss in the compression load capacity of an aluminum structure caused by elastic softening, time-independent plastic (yield) softening, and time-dependent plastic (creep) softening effects are analyzed by using a mechanics-based FE solution. The modeling approach is validated by structural tests on an aluminum alloy (5083 Al) plate supporting an applied compression load while locally heated at different radiant heat flux (temperature) levels. The modeling approach can estimate the deformations, initiation of plastic collapse, and final failure of the aluminum test article for heat flux levels representative of different fire types. The FE model described in this paper can be used as the basis for performing complex deformation and failure analysis of compression-loaded aluminum (and other metallic) structures in fire.

This research investigates the cyclic flexural behavior and performance of concentrically braced frame beam-column connections in the context of evaluating the reserve lateral load-resisting capacity in concentrically braced frames. Eight beam-column connections with gusset plates, employing double angle and end plate details, were studied using full-scale experiments to determine their flexural strength, stiffness, and ductility. In this paper, the effects of connection parameters, such as end plate thickness, angle thickness, bolt configuration, weld type and size, and supplementary seat angle, are evaluated. The global connection behavior and performance are quantified using normalized moment versus story drift data. In comparison to a baseline double angle detail, all connection variations increased the strength and stiffness. The end plate variations resulted in larger increases in strength, but drift capacity was limited by bolt fracture. The double angle variations increased the strength by smaller margins, but strength loss occurred more gradually, and larger drifts were sustained. The double angle connection configuration with a supplemental seat angle is shown to provide the best balance of strength and deformation capacity.

The development and implementation of the real-time hybrid simulation (RTHS), a seismic response simulation method with a combination of numerical computation and physical specimens excited by shake tables and auxiliary actuators, are presented. The structure to be simulated is divided into one or more experimental and computational substructures. The loadings generated by the seismic excitations at the interfaces between the experimental and computational substructures, in terms of accelerations and forces, are imposed by shake tables and actuators in a step-by-step manner at a real-time rate. The measured displacement and velocity responses of the experimental substructure are fed back to determine the loading commands of the next time step. The unique aspect of the aforementioned hybrid simulation method is the versatile implementation of inertia forces and a force-based substructuring. The general formulation of RTHS enables this hybrid simulation method being executed as real-time pseudodynamic (PSD) testing, dynamic testing, and a combination of both, depending on the availability of the laboratory testing equipment and their capacity. The derivation of the general formulation and the corresponding testing system are presented in this paper. Numerical simulation and physical experiment were conducted on the RTHS of a three-story structural model. Simulation and experimental results verify the concept of the proposed general formulation of RTHS and the feasibility of the developed corresponding controller platform.

This paper presents the development of models and the analytical study of the structural response of deteriorating unbonded posttensioned beams, with the aim of providing suitable tools for the evaluation of existing deteriorated structures. The corrosion phenomena of the tendons are reviewed in the introduction. Two modeling approaches are proposed: (1) beam macro finite-elements (MFE) using cross-section analysis and (2) two-dimensional (2D) nonlinear finite-element (FE) analysis. The corrosion attack modeling considers tendon-breaking and ductility-reduction of the prestressing and mild steel. Bond deterioration is also considered for the ordinary reinforcement. The models are validated by simulating three tests on corroded beams with unbonded prestressing wires, part of the Rance benchmark exposed to 40 years of attack in a natural marine environment, and then tested for imposed loading in the laboratory. The results obtained for the global response show a good agreement with the tests at all stages of loading. The model’s predictions regarding the strain in the ordinary bars and unbonded wires are discussed in relation to the ductility reduction of the reinforcement caused by pitting corrosion and the risk of stress-corrosion cracking. Both modeling approaches are adequate, with different levels of discretization and size of the output. The MFE modeling is appealing for use in practice because of its computational simplicity.

Based on fatigue experiments on eight reinforced concrete (RC) beams strengthened with the steel plate-concrete composite (SPCC) technique, the fatigue life and development trend of stiffness and strain of specimens under a constant amplitude fatigue loading were studied. The experimental results showed that the fatigue failure mode of the SPCC strengthened beams was the fatigue failure of the steel plate. The initial fatigue crack in the steel plate appeared near the weld toe of studs and then expanded through the plate. Unlike regular RC beams, the fatigue failure mode of the tested specimens was ductile. The amplitude of stress in the steel plate had the most important influence on the fatigue behavior of RC beams strengthened with the SPCC technique. The level and amplitude of stress in the steel plate should be strictly controlled in practical design, and therefore, the high-strength steel and thin steel plate were not suitable for RC beams strengthened with the SPCC technique. The prestress in the steel plate could improve the fatigue life of RC beams strengthened with the SPCC technique. The S-N curve of the tension steel plate, welded with studs specified in the British code of practice for bridge design, BS5400, was conservative for the design of steel plate in RC beams strengthened with the SPCC technique. Calculation models were presented of the residual static capacity and stiffness of RC beams strengthened with the SPCC technique after fatigue failure.

This note examines the linear response of thin, shallow curved beams to an axially-directed compressive load. The response is tracked with a rise parameter drawn from related work on linear arches through which it is shown that the curved beam behaves like an axially compressed bar for small values of the rise parameter, whereas it responds as a beam in bending for large values of the parameter. This is totally opposite to that of laterally-loaded arches.

This study aimed to evaluate the influence of beam shoulder on the moment-carrying capacity of traditional post-beam joints, dovetailed mortise, and tenon joints. The specimens were manufactured by a computer numerical controlled (CNC) cutting machine with Japanese larch six-ply glulams (glued laminated timber), and moment-carrying capacity was investigated by static loading tests. The results of the tests indicated that the moment resistance, joint stiffness, and failure modes were different with or without beam shoulder. The results also indicated that all joints types underwent significant deformation without breaking and maintained after the yield point. The failure mode, which included post splitting, shear failure of mortise branches, or embedment failure of tenon, was dependent on the presence of the beam shoulder. The results indicated that the beam shoulder significantly affected the performance of the post-beam joint. It was concluded that the beam shoulder reinforced the dovetailed mortise and tenon joints. Hence, the beam shoulder must be considered as an important factor in the structural design of traditional post-beam joints.