全预应力混凝土梁的长期变形计算

关于全预应力混凝土梁长期变形的设计计算问题,现行TB10002.3—99《铁路桥涵钢筋混凝土和预应力混凝土结构设计规范》中尚无明确条款。对此,基于大型商用软件SOFISTIK的计算结果,重点研究了预应力度、混凝土强度等级以及综合配筋指标等设计参数对全预应力混凝土梁长期变形的影响,指出按《公路钢筋混凝土及预应力混凝土桥涵设计规范(2002送审稿)》和现行GB50010-2002《混凝土结构设计规范》的计算结果偏于不安全。提出了全预应力混凝土梁的长期变形增长系数需按混凝土龄期分时段取值的设计建议。

全预应力混凝土梁长期变形计算

与部分预应力混凝土梁相比,全预应力混凝土梁全截面受压且压应力较高,由于混凝土收缩徐变产生的梁长期变形也更大。该文从按龄期调整的有效模量法出发,将梁沿长度方向细分单元,细分单元长度为截面高度的1倍~2倍,锁定单元节点,分别计算混凝土的收缩、徐变以及预应力筋的松驰对其产生的强迫力值;释放强迫力,并将其反向作用于节点上,求出此时的截面时随应变和附加曲率,进而推导出可用于求解任意时刻的全预应力混凝土梁长期变形的计算公式。基于该课题组和其他研究者试验结果,对该文及国内外规范的计算公式进行了对比分析,结果表明：该文公式计算值与试验结果吻合良好;国内外规范计算值与试验结果的平均误差则明显偏大,且计算结果偏于不安全。

预应力钢筋混凝土连续箱梁超长钢铰线双向张拉控制

现代桥梁工程中，全预应力钢筋混凝土连续箱梁结构已被广泛采用。它提高了桥梁结构的抗裂度与刚度，使桥梁的竖向剪应力和主拉应力得以减小。但是，如果在施工过程中控制不好，将会对桥的内在质量产生很大的影响。本文通过成都市三环路工程中的川陕路立交桥施工实践，对全预应力钢筋混凝土连续箱梁的预应力分析、张拉器具的选用、张拉工艺、施工中的质量检查和张拉过程中出现的病害及防治作了系统的探索。

Full-scale model tests and nonlinear analysis of prestressed concrete simply supported box girders

Full-scale model tests were carried out on a 30 m span prestressed concrete box girder and a 20 m span prestressed concrete hollow slab. Failure models were prestressed reinforcement tensile failure and crashing of roof concrete, respectively. The ductility indexes of the box girder and hollow slab were 1.99 and 1.23, respectively, according to the energy viewpoint. Based on the horizontal section hypothesis, the nonlinear computation procedure was established using the limited banding law, and it could carry out the entire performance analysis including the unloading, mainly focusing on the ways to achieve the unloading curves computation through stress-strain, moment-curvature and load-displacement curves. Through the procedure, parameters that influence on the bearing capacity, deformation performance and ductility of the structures were analyzed. Those parameters were quantity of prestressed reinforcement and tension coefficients of prestressed reinforcement. From the analysis, some useful conclusions can be obtained.