Papers by Keyword: Moment-Curvature

Abstract: Engineers have realized that corrugated webs enormously increase their load carrying capacity as well as stability against buckling and can result in very economical design. In this paper, the results of the experiments conducted on cold-formed steel beam with encased trapezoidally corrugated webs with a view to study their strength and ductility are presented. The ductility of cold-formed steel beam with plain web and corrugated web is compared with that of encased trapezoidally corrugated web. Data presented include the load versus deflection curves, load versus strain curves, strength capacity, displacement ductility indices and moment versus curvature curves. It is found that the beam with encased trapezoidally web not only increases the moment carrying capacity but also the ductility. The results showed that the Super elastic property of encased corrugated web beams enhances the usage of it in the earthquake resistant structures.

Abstract: Considerable amount of studies on the ductility and flexural behaviour of normal and high strength concrete elements under static load can be found in literature. However, most of the previous theoretical investigations on moment-curvature (M-φ) relationship of concrete elements to calculate curvature ductility and flexural capacity did not take account of the strain-rate effect on the material models. M-φ analysis of concrete elements under dynamic loading are often conducted with material models developed for quasi-static load by applying Dynamic Increase Factors (DIF) to the material properties to reflect the strain-rate effect. Depending on magnitude and duration of applied dynamic load, element stiffness and boundary condition strain-rate varies over the cross section. Thus, the application of DIF to modify peak material properties often fails to reflect the strain-rate effect reliably. The improvement of using material model which incorporated strain-rate in its constitutive equations has been explored in this study. The effects of reinforcement amount, grade and concrete strength on curvature ductility for different strain rates have been studied using material models which have strain-rate effects included in theirs formulation. Based on the parametric study, a simple formula to estimate curvature ductility for concrete elements under explosive loads (high strain-rates) has been proposed.

Abstract: To simplify the analysis, an elastic perfectly plastic stress-strain law was presented for UHPFRC. The post-cracking behavior was described by the average constant post-crack tensile strength. A strain parameter μ is proposed to evaluate the performance and efficiency of steel fibre reinforcement. 8 rectangular beams were tested in this investigation. Based on the proposed constitutive model, the full history of their flexural moment-curvature relationship for UHPFRC beams was calculated and compared with experimental data on prestressed UHPFRC beams. Good agreement between calculated strengths and experimental data was obtained.

Abstract: In order to model the elasto-plastic behavior of steel-concrete beams in high-rise buildings correctly and conveniently, plastic hinge method is used. Based on experimental and theoretical research on composite beams, the trilinear moment-curvature skeleton curve of steel-concrete composite beams is amended by numerical simulation and theoretical analysis. And the 4 poly-line moment-curvature skeleton curve model is suggested for elasto-plastic analysis of steel-concrete composite beams. The elastic-plastic model is then used for real composite beams under monotonic load experimental analysis to verify its precision. The suggested model can lay a foundation for the dynamic analysis under strong earthquake for the globe steel-concrete composite structures.

Abstract: The study on the hysteretic characteristics of steel reinforced concrete (SRC) members is the basis of nonlinear seismic analysis of such structures. So in this paper, by summarizing the hysteretic features of SRC members, a quadrant-linear restoring-force model is suggested. Then the model is verified with available experimental results and proved to be effective and reliable.