摘要
为深入了解旧简支梁转变为连续梁的受力特性,进行了3根T形截面简支梁转变为2跨连续梁及1根对比梁的试验研究。转变方法为负弯矩区设置预应力钢绞线的后张法和使用高强钢丝顶推梁体获得预应力的先张法。试验中考虑的参数为预应力钢绞线的长度、单双支座及预应力施加的方法。试验结果表明,连续梁的破坏形态为中支座受压区混凝土压碎和新老混凝土界面间粘结滑移破坏。简支梁转变为连续梁后,开裂荷载、极限荷载和刚度得到了较大的提高。在连接处设置双支座可以有效地增加试验梁的刚度,减少裂缝数量,改善连接处混凝土的受力,应变分布更为均匀。纵向连续长度对负弯矩区的裂缝数量及间距有一定的影响,增加了预压应力区的范围,减少了负弯矩区的裂缝数量,增大了裂缝间距。由于受到两端旧混凝土的约束,新老混凝土界面间应变差及滑移值较小,可以有效地传递界面间的剪力。弯矩重分布的规律为跨中截面开裂后,弯矩向中支座截面传递,中支座截面开裂后,弯矩反向向跨中截面传递。
Three T-shaped section continuous beams and one control beam were tested to investigate the technical feasibility and the mechanical behavior of changing old simply supported beams into continuous beams. Two techniques of changing old simply supported beams into continuous beams by exerting prestressing loads in the negative moment zones are presented, one is post-tension and the other is pre-tension. Factors considered in this experimental program included length of the steel strands, single and double supports and prestressing method. Two failure modes, concrete crushing at mid-support and bond failure at the old and the new concrete interface, were revealed in the test. Comparing with the control beam, the crack loads, ultimate loads and flexural rigidities of the continuous beams were increased. The number of cracks was decreased and the flexural rigidity increased when the double supports were placed at the midsupport. The continuous length affects the number of cracks and the crack spacing. The slip between the old and new concrete interface was small and the interface shear forces could be transferred effectively. The mid-span moments were decreased and the support moments increased when cracks appeared at the mid-span. Thereafter, the support moments were decreased and the mid-span moments increased when the cracks appeared at the supports.
出处
《土木工程学报》
EI
CSCD
北大核心
2009年第6期49-54,共6页
China Civil Engineering Journal
基金
辽宁省交通厅重点资助项目(0514)
关键词
简支梁
转变
连续梁
先张法
后张法
试验研究
simply supported beams
transform
continuous beams
pre-tension
post-tension
experimental study
