缓粘结预应力混凝土梁钢绞线粘结性能试验研究

Experimental study on cohesive property of steel strand in retard-bonded prestressed concrete beams

为研究缓粘结预应力钢绞线与混凝土之间粘结性能,对3根截面尺寸相同、普通钢筋配筋相同、预应力不同的混凝土梁进行了试验研究,重点研究了不张拉、不锚固钢绞线预应力混凝土梁的荷载-位移关系、裂缝分布规律、最大裂缝宽度随荷载的变化规律、钢绞线内的应力大小、钢绞线与混凝土之间的粘结强度等,与不配预应力筋的普通钢筋混凝土梁和配筋相同的普通预应力混凝土梁的受力进行了对比分析。试验表明,缓粘结预应力钢绞线与混凝土之间有良好的粘结性,粘结强度与混凝土咬合处剪切破坏强度相吻合;利用粘结作用和一定传递长度,不张拉、不锚固钢绞线预应力可以达到1100MPa以上,考虑承载力检验系数后钢绞线应力设计值可取800MPa;不张拉、不锚固预应力混凝土梁的弯曲裂缝分布与普通预应力混凝土梁基本相同,破坏时端部产生的钢绞线滑动引起沿钢绞线方向的裂缝,进一步证明粘结破坏是混凝土的剪切破坏而非粘合剂破坏。

In order to investigate the cohesive property between retard-bonded prestressed steel strand and concrete,experimental studies were conducted on 3 specimens with same cross-section,same reinforcement and different prestresses.The study focused on the results of non-tensioned and non-anchoraged prestressed concrete beams,including load-displacement curve,distribution of cracks,relationship between loading and,stress of the steel strand,cohesive strength between steel strand and concrete.The results were compared with those of common reinforced concrete beams without prestressing tendon and common reinforced concrete beams with the same ratio of prestressing tendon.The experiments show that cohesive property between retard-bonded prestressed steel strand and concrete is good,and the cohesive strength agrees well with the shear strength of the concrete at the interlock section.The prestress in the steel strand without tensioning and anchorage can reach more than 1100 MPa by means of cohesive stress and certain transfer length,and the design value of the steel strand stress can be evaluated as 800 MPa when considering bearing capacity test coefficient.The distribution of the bending cracks of non-tensioned and non-anchoraged prestressed concrete beams is basically the same to that of the common prestressed concrete beam,and cracks along the direction of the strand caused by the sliding of the strands appeared at the end of the beam after the failure.It is conformed that the cohesive failure features the shear failure of concrete rather than the adhesive failure.