锚具失效后后张法预应力简支梁试验研究

Experimental study of post-tensioned prestressed simply-supported beam after anchorage failure

为研究后张法预应力混凝土简支梁桥拆除锚具后残余预应力对结构抗力的贡献,通过2根切除锚具试验梁和1根对照梁的静载试验,研究拆除锚具后预应力梁的受力性能。研究结果表明:拆除锚具后,预应力钢束通过灌浆材料对混凝土具有纵向压缩作用,混凝土与普通钢筋对结构的贡献从端部到跨中逐渐减小;切除锚具只影响开裂荷载和裂缝开展宽度,并不影响梁体最后的裂缝分布形式和跨中混凝土破坏形态,但会降低极限荷载;达到屈服荷载后,试验梁的预应力钢束与孔道灌浆开始脱离,试验梁承载能力降低,试验梁的抗裂性能以及结构延性明显降低;开裂后,在同样荷载增量下,试验梁中预应力钢束承担更多的荷载。建议在实际拆桥工程中,当拆除锚具后,在达到结构屈服荷载之前可按正常状态考虑预应力钢束对结构的作用。

For researching the contribution of residual prestress to the post-tensioned prestressed concrete simply-supported beam after the anchorage failure,two prestressed beams with failure anchorage and a normal was tested.The results show that the anchorage has longitudinal extrusion effect on the concrete,and the contribution of the concrete and steels to the structure decreases from the end to the mid-span.Excising anchorage only affects the racking load and crack width,and does not affect the final crack distribution and the concrete failure mode in the span,but will reduce the limit load.After the yield load,the pre-stressed tendons and the channel start to disengage,and the bearing capacity of the test beam falls sharply.The crack resistance and ductility of prestressed concrete beams are reduced obviously.After cracking,under the same load increment,the pre-stressed tendons share more load in the test beam.It is suggested that the contribution of pre-stressed tendons to the structure can be considered before the structural yield load after the anchorage failure.