焊接工字形截面钢支撑低周疲劳性能试验研究

通过21根铰支焊接工字形截面支撑在6倍试件的受拉屈服位移幅值下的对称循环轴向加载试验,研究了具有不同几何特性的该类支撑构件的低周疲劳和耗能性能。研究发现,支撑翼缘直到断裂的疲劳损伤发展过程可分为可见裂纹萌生,穿透裂纹形成和穿透裂纹扩展3个阶段,并根据试验数据提出了估算支撑构件疲劳寿命和循环耗能能力的经验公式。统计分析表明,裂纹萌生疲劳寿命与弹塑性局部屈曲密切相关,当支撑翼缘的宽厚比越小,支撑的长细比越大时,其裂纹萌生疲劳寿命就越长。试验还表明,低周疲劳性能较优的支撑构件亦具有较高的耗能能力。为了防止框架-中心支撑结构中的支撑构件在强震下过早发生断裂破坏,在实际设计中除要限制板件的宽厚比之外,还应适当放宽现行规范对支撑构件长细比的限制。

The low-cycle fatigue tests of welded I-section bracing members

The low-cycle fatigue behavior and energy dissipation capacity of the welded I-section bracing members with different geometry properties are investigated by 21 pin-ended bracing tests under axial harmonic cyclic loading with constant amplitudes of 6 times the tension yield deformation of specimens.It is found that the fatigue damage propagating to fracture in the flanges of the bracing members can be divided into 3 stages,the macroscopic surface crack initiation,the penetrated crack formation and the penetrated crack propagation.Some empirical formulas to estimate the fatigue life and cyclic energy dissipation capacity of the bracing members are also presented based on the experimental data.The statistical analysis indicates that the fatigue life to surface crack generation significantly depends on the inelastic local buckling and will increase with decreasing width-thickness ratios of the flanges and increasing slenderness ratios of the bracing members.The test results show that the bracing members with better low-cycle fatigue resistance also have better energy dissipation capacities.In order to avoid early fractures of the bracing members in concentrically braced frames during a severe earthquake,besides limiting the width-thickness ratios of the plates,the slenderness ratios of the bracing members limited by the current codes should be relaxed in the practical design.