摘要
研究目的:通过理论分析、试验、实践,研究混凝土箱梁腹板内竖向预应力筋预应力损失大、作用效果差的成因,提出对策与措施,以保证竖向预应力作用效果,避免腹板出现主拉应力裂纹。研究结论:设计中,对竖向筋控制应力与屈服强度的比值进行控制;计算由锚具变形和缝隙压缩等引起的预应力损失时,取1.65 mm的回缩值;增加由锚垫板安装误差引起的预应力损失,并取3.3 mm的回缩值;考虑混凝土和水泥浆水化热引起的预应力损失,施工中重视施工工艺的改进和完善;控制锚垫板安装倾角误差,做到"两平一直",控制锚垫板与螺帽的夹角在1°以内;使用扭矩扳手拧紧螺帽,对32和25竖向筋的锚固扭矩分别取1 200 N.m和600 N.m;采取二次张拉和超张拉工艺;前段梁与后段梁连接处的4组竖向筋与后段梁的竖向筋同步张拉。
Research purposes： Based on the theoretic analysis,test and practice,the research is done on the reasons for the big pretress loss and poor effect of prestressed reinforcement of the web plate of concrete box girder,and the measures for them are presented to guarantee the effect of the vertical prestress and avoid the appearance of stress crack on the web plate.Research conclusions：In design,the ratio between the stress and yield degree of vertical reinforcement should be controlled.The rebound value of 1.65 mm should be adopted when calculating the stress loss caused by anchor deformation and gap compression.The stress loss caused by installation error of anchor backer should be added and the rebound of 3.3 mm should be used.The stress loss caused by water thermalization of concrete and cement grout should be considered and the attention should be paid to improvement of the construction technique in construction.The error of incline angle should be controlled to make two flat and one straight and make the included angle within 1°when installing the anchor backer.The anchor torque of 1 200 N·m and 600 N·m with torque spanner should be used to Ф32 reinforcement and Ф25 reinforcement.The tension and super tension techniques should be used.The four groups of vertical reinforcements on the joint place of the front part and the rear part of the girder and the reinforcements on the rear part of the girder should be tensed at the same time.
出处
《铁道工程学报》
EI
北大核心
2010年第3期52-56,共5页
Journal of Railway Engineering Society
关键词
预应力混凝土
箱梁
竖向预应力
预应力损失
控制
prestressed concrete
box girder
vertical stress
prestrsess loss
control
