高温后足尺有粘结预应力混凝土梁板力学性能研究

针对足尺有粘结预应力混凝土梁板高温后的抗弯承栽力开展了非线性计算分析。结果表明,综合配筋指标、有效预应力对高温后极限弯矩与常温下极限弯矩比值M_u~A/M_u的影响不大,预应力度和预应力筋的保护层厚度对M_u~A/M_u影响显著。高宽比近似相同的有粘结预应力混凝土梁,当第一排钢筋的保护层厚度相同时,受火时间为3 h,高度为700 mm的梁高温后截面承栽力下降幅度最大约为30%,高度为4500 mm的梁高温后截面承栽力下降幅度不到10%,高温后大尺度梁的力学性能优于小尺度梁。给出了考虑预应力筋保护层厚度和预应力度影响的有粘结预应力混凝土板M_u~A/M_u的计算公式,以及综合考虑预应力筋、非预应力筋合力点到梁底距离和预应力筋梁侧保护层厚度影响的有粘结预应力混凝土梁M_u~A/M_u的计算公式。

The Mechanical Behavior of the Full-scale Bonded Prestressed Concrete Slabs after High Temperature

Flexural bearing capacity of the full-scale bonded prestressed concrete beams and slabs under high temperature is analyzed by nonlinear method.The result shows that composite reinforcement index and effective prestress have little effect on M~A_u/M_u of bonded prestressed concrete beams and slabs,and concrete cover of prestressed reinforcement has significant effect on M~A_u/M_u.When the ratios of height to width are similar,and the concrete covers of reinforcement in the first row are the same,the biggest descent rate of flexural bearing capacity is almost 30%for 700 mm high beam after 3 h fire duration,comparing with 10%for 4500 mm high beam.Mechanical performance of large scale beams is better than small scale beams after high temperature.The calculation formula on M~A_u/M_u of bonded prestressed concrete slabs is established introducing the effect of concrete cover of prestressed reinforcement and prestress degree. The calculation formula on M~A_u/M_u of bonded prestressed concrete beams is also established considering the distances between the bottom of beams and the force points of prestressed reinforcement and nonprestressed reinforcement.