配置500MPa钢筋混凝土梁长期荷载裂缝宽度试验研究

为了研究500MPa钢筋受弯构件在长期荷载作用下的裂缝宽度发展规律，对8根配置500MPa钢筋的T形截面简支梁进行了在长期荷载下的裂缝宽度试验，观测了裂缝的长期发展过程，分析了各变化参数对裂缝宽度的影响，并与同条件下配置335MPa钢筋试件的长期裂缝宽度进行了对比。试验结果表明：配置500MPa钢筋试件的裂缝形态以及裂缝分布特点与配置335MPa级钢筋试件基本相同，但长期裂缝宽度明显加宽，而在正常使用状态下，配置500MPa钢筋试件的裂缝间距实测值以及具有95%保证率下梁的长期裂缝宽度均小于GB 50010-2002《混凝土结构设计规范》的计算值；对比试验表明：在受压区配置纵向受力钢筋能够有效抑制受压区混凝土的徐变，在一定程度上抑制裂缝宽度发展。此外，尽管具有不同工作应力的钢筋试件中的裂缝宽度不同，但随时间发展裂缝宽度的变化趋势没有明显区别；根据试验结果，给出了长期裂缝宽度扩大系数τl建议值。图9表6参15

Experimental investigation on simply supported RC beams with 500MPa reinforcement under long-term loads

The crack widths of 8 simply supported RC T-beams with 500MPa reinforcement were measured under long-term loading, and the development of long-term crack width was observed. In the meantime, the effect of various parameters on crack width was analyzed. The results were compared with those of specimens reinforced by 335MPa rebars under the same condition. Test results show that the crack width of specimens with 500MPa reinforcement is significantly wider than that of specimens with 335MPa reinforcement, although the configuration and distribution of cracks are similar. However, the measured crack spacing and long-term crack widths with 95 percent confidence are smaller than the values calculated with the equations given by the GB 50010—2002 ‘Code for design of concrete structures’. It is also found from the comparing experiments that the longitudinal reinforcement in the compression zone restraints effectively the creep of concrete, and consequently limits the crack width. In addition, although the crack width varies with different working stress of reinforcement, the variation with time of crack width of respective specimen is the same. The value of amplification coefficientτl is suggested for the calculation of crack width with the equation given by the current design code.15Refs.In Chinese.