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铁路预应力混凝土简支梁,在施加预应力和自重作用下,各截面处于偏心受压状态,下缘混凝土的预压应力沿梁高按线性变化规律逐渐变小。梁体各部分长期处于不同程度的预应力作用下,各纤维层将产生不同的与时间有关的徐变变形,下缘混凝土的徐变变形最大,沿梁高逐渐变小。因此桥梁变形后会因上长下短,产生向上拱起的弯曲变形,即梁的预应力徐变上拱,其变形量为徐变上拱度。影响预应力梁徐变上拱度的主要因素有预应力度的大小、预应力束的位置、恒活载比值、混凝土弹性模量的变化和施加预应力时混凝土的强度等。综合国内外的研究成果与工程实践,下面从设计和施工工艺两个方面总结徐变上拱的控制措施。
Under the action of prestress and self-weight, the cross-section of railway prestressed concrete is under eccentric compression. The pre-compressive stress of concrete at the lower edge gradually decreases along the linear curve of beam height. Various parts of the beam body are under varying degrees of prestressing for a long period of time. Various fiber layers will have different time-dependent creep deformations. The creep deformation of the concrete at the lower edge is the largest and the beam height is gradually reduced along the beam height. Therefore, the deformation of the bridge will be due to the length of the short, resulting in upward arch bending deformation, that beam prestressed creep on the arch, the deformation of the creep camber. The main factors affecting the creep camber of prestressed beams are the magnitude of prestress, the location of prestressing beam, the ratio of constant load, the change of elastic modulus of concrete and the strength of concrete when prestressed. Comprehensive domestic and international research results and engineering practice, the following two aspects from the design and construction technology summary creep arch control measures.