UHPC梁开裂弯矩和裂缝试验

Cracking moment and crack width of ultra-high performance concrete beams

为研究超高性能混凝土梁的开裂弯矩和裂缝特征及评估现有规范公式计算超高性能混凝土梁开裂弯矩和裂缝宽度的适用性,进行了8根超高性能混凝土T形简支梁的受弯性能试验,观察试验梁的开裂弯矩和裂缝发展.试验结果表明:预应力水平对开裂荷载影响较大;超高性能混凝土梁的弯曲裂缝细而密,加载初期最大裂缝宽度发展较慢,纵筋屈服后最大裂缝宽度发展明显加快;利用现有规范公式计算超高性能混凝土梁开裂弯矩和最大裂缝宽度过于保守.在现行规范公式的基础上引入抗裂影响系数和裂缝修正系数,给出了超高性能混凝土梁开裂弯矩和最大裂缝宽度的建议公式,建议公式的计算值和试验值吻合良好.

Eight ultra-high performance concrete T-beams subjected to bending were tested to investigate their cracking moments and cracking characteristics and evaluate the formulas for cracking moment and crack width specified in existing design codes. The test results show that the degree of prestress has a great impact on the cracking moment ; the bending cracks are dense and fine, the development of the maximum crack width is slow at the early stage of loading and speeds up remarkably when the reinforcements reach to yield strength. Predicating the cracking moment and maximum crack width by existing code formulas will lead to overly conservative results. The modified formulas of cracking moment and crack width are suggested for ultra-high performance concrete beams by introducing the anti-cracking effect coefficient and crack-correction coefficient respectively, and the calculated values by the suggested formulas agree well with the test results.