Study of Cyclic Behavior of Confined High-Strength Concrete Moment-Resisting Frames

本文介绍了约束高强混凝土抗弯框架的循环响应试验资料，并提出了一种评估约束高强混凝土框架破坏模式和极限水平承载能力的分析方法。试验包括6个一开间单层高强混凝土抗弯框架，由两根200×200 mm的钢管约束的方形柱和一根180×300 mm的方形柱组成。用传统箍约束的矩形梁。所有框架均由设计强度为80 mpa的高强混凝土制成，并进行了循环侧力和恒定轴向荷载的组合试验。试验结果表明，钢管约束柱可以确保高强混凝土框架在高轴向荷载作用下的非常稳定的循环性能。由于钢管约束可以将混凝土全部约束在柱中，直到大变形时，高强混凝土框架的滞回环不会发生突然的强度退化。它还拥有BECO…更明确的是，采用内加劲肋加固方钢管可以显著提高其约束效果。宽厚比(B/t)为87的方钢管加内加劲肋的约束效果与B/t比为33但无内加劲肋的方钢管的约束效果相同，而前者的含钢量仅为后者的55%。本文还提出了一种设计方法，使结构工程师可以简单地评估约束高强混凝土框架的极限水平荷载和变形能力。该方法考虑了方钢管的约束效应，简化了极限荷载的计算过程。约束高强混凝土柱和梁的荷载和变形能力。理论计算结果与实验结果的对比表明，所提出的设计方法能够很好地预测实验结果。此外，所有试验框架都按设计延性方式进行，这意味着所提出的设计方法也使工程师能够在设计阶段可靠地预测约束高强混凝土框架的破坏模式。较少

This report presents experimental information on the cyclic response of confined high-strength concrete (HSC) moment-resisting frames along with an analytical method to evaluate the failure mode as well as the ultimate lateral load capacity of the confined HSC frames. The tests involved six one bay and one-story HSC moment-resisting frames, which consisted of two 200x200mm square columns confined by steel tube and one 180x300mm. rectangular beam confined by conventional hoops. All of the frames were made of HSC with designed strength of 80MPa and were tested under combined cyclical lateral force and constant axial load.Test results have indicated that confinement of the columns by steel tube could ensure very stable cyclic performance to HSC frame even when it was under high axial load. Since confinement by steel tube can contain the whole of concrete in a column, no abrupt strength degradation occurred in the hysterestic loops of the HSC frames till large deformation. It has also beco … More me clear that strengthening the square steel tube with inner stiffener could enhance its' confinement effect significantly. The square steel tube, which had width-to- thickness ratio (B/t ratio) of 87 and was strengthened with inner stiffener, provided the same confinement effect as the steel tube with B/t ratio of 33 but without inner stiffener, while the steel amount of the former is only 55% of the latter.This report also presents a design method enabling structural engineer to simply evaluate the ultimate lateral load and deformation capacity of confined HSC frames. This method involves consideration of confinement effect by the square steel tube and simplification of calculation procedure for the ultimate. load and deformation capacity of confined HSC columns and beams. Comparison between the theoretical and the measured results has indicated that the proposed design method could predict experimental results very well. In addition, all of the test frames performed in a ductile manner as designed, which implies that the proposed design method also enables engineers to reliably predict the failure mode of the confined HSC frames at the stage of design. Less