配置500MPa钢筋后张有粘结预应力混凝土梁裂缝形态分析

Analysis of Crack Patterns of Post-Tensioned Bonded Prestressed Concrete Beams with 500 MPa Steel Bars

目的研究配置500 MPa钢筋后张有粘结预应力混凝土梁的裂缝形态,比较各梁在纯弯段范围内的裂缝分布,得到梁侧面裂缝沿梁高的发展变化规律.方法采用两点对称集中的加载方式,对8根试验梁在短期荷载作用下进行弯曲裂缝宽度试验.结果纵向受拉非预应力筋的直径和钢绞线束的束数对裂缝分布有一定影响,而钢绞线束重心至受拉底面的距离对裂缝分布无明显影响;侧面裂缝观测点至截面受拉边缘的距离d与观测点处的裂缝宽度w(d-w)曲线在纵向受拉非预应力筋附近处出现向左凹陷的现象,而在钢绞线束附近处向左凹陷的现象不明显;d-w曲线大致呈单"Z"字形或双"Z"字形.结论在梁受拉区布置细直径钢筋有利于控制裂缝开展,纵向受拉非预应力筋对其附近裂缝有较好的约束作用,钢绞线对其周围裂缝的约束作用较纵向受拉非预应力筋要弱.

Based on flexural crack-width tests of 8 post-tensioned bonded prestressed concrete beams with 500 MPa tensile non-prestressing steel bars under two-point symmetrical concentrated short-term loading, crack patterns of beams are investigated. Crack distributions at pure bending section of beams are compared. The development of side cracks along beam height is obtained. Test results show that the diameter of tensile non-prestressing steel bar and the number of strand bundles have effect on crack distributions;however, the distance between the center of strand bundles and the tensile bottom surface has no significant influence on crack distributions. The curve of d-w （ d denotes the distance between observation points of side cracks and tensile edge of section, w denotes crack width at observation points） shows left depression near tensile nonprestressing steel bars, while no obvious left depression near strand bundles. The curve of d-w is approximately characterized by single Z or double Z alphabetic shape. The development of cracks will be well controlled if small-diameter steel bars are arranged in the tensile area of beams. The cracks in the vicinity of tensile non-prestressing steel bars can be better restrained than the ones around strands.