混凝土箱梁早期温度裂缝的影响因素

调查研究发现,大量混凝土箱形梁桥存在严重的早期温度收缩开裂问题。本文以实际工程为背景,围绕混凝土早期温度场理论按排除法的思想,运用大型有限元分析软件ANSYS,对箱形混凝土梁的早期温度裂缝的各种因素进行了详细的分析研究。分析结果显示,该工程中由早强剂引起的温度收缩产生的拉应力高达4 MPa,蒸汽养护不当亦可产生很大拉应力。结果表明:混凝土箱梁施工,选择添加剂时要仔细考查其性能和对混凝土的影响,宜选择可降低混凝土早期温度,并引起较大收缩的添加剂;应重视温控措施,以避免混凝土早期温度过高而引起混凝土收缩,导致混凝土产生裂缝。

The influencing factors of the temperature crack of concrete box girders at the early stage

The research shows that there is a serious problem of temperature-shrinkage cracking at early period in a large number of concrete box beam bridge.According to practical engineering background,this paper adopts a large scale of finite element analysis software ANSYS to analyse the various factors in detail about the temperature cracks of concrete box girder in the early stage by temperature field theory and exclusive method.The result of analysis reveal that the temperature-shrinkage tensile stress of the project＇s concrete up to 4 MPa caused by early-strength agent,and improper maintenance-steam can be generated considerable tensile stress.The results show that when select additives they should be examined carefully on their performance and the impact for concrete.The better choice is to choose the one which can reduce the temperature-shrinkage of the concrete at the early time and gender the larger shrinkage.In addition,it should be paid attention to the measures of governing the temperature in order to prevent cracks that are caused by contracting from the high temperature of concrete at the early stage.