蒸汽养生下预制箱梁预应力张拉控制条件研究

Steam Curing System of Concrete Suitable for Rapid Construction of Precast Bridges

为缩短预制周期提高施工效率,结合相关规范及设计要求提出蒸汽养生条件下预制箱梁的预应力张拉条件。以实际工程4片箱梁为研究对象,通过对蒸汽养生条件下梁体预应力张拉后有效预应力连续测试,得到同龄期下预制梁跨中上拱度相对变化量以及混凝土抗压强度和弹性模量的测试结果。结果表明:蒸汽养生条件下预应力箱梁混凝土的抗压强度和弹性模量在龄期为40 h时达到设计值要求的90%,预应力损失在龄期5 d后基本趋于稳定,龄期9 d内跨中累计上拱度在1 mm以内,验证了蒸汽养生条件下预制梁混凝土抗压强度和弹性模量均达到设计值要求的90%及以上可一次性预应力张拉的合理性,为工程推广提供数据支撑。

In order to shorten the precast period and improve the construction efficiency, the prestressed tension condition of precast box girder under steam curing condition is proposed in combination with relevant codes and design requirements. Four pieces of box girders in the actual project are selected as the research object. The effective prestress of beam under steam curing condition after tension was continuously tested, and the test results of the relative change of camber in midspan of precast beam and the strength and elastic modulus of concrete in the same age period was carried out. The results indicate that the compressive strength and elastic modulus of the precast beam concrete reach 90% of the design requirement at the age of 40h under steam curing condition,and the prestressing tendon losses tends to be stable after the age of 5d, the cumulative camber in the mid - span is within 1mm after the age of 9d. the compressive strength and elastic modulus of precast beam concrete under steam curing condition can reach 90% of the design value and above,and the rationality of all the prestressing can be carried out at one time. This research can provide data support for its engineering application.