半预制预应力UHPC-S-NC盖梁静力性能试验及理论分析

Static Test and Theoretical Analysis of Semi-precast Prestressed

为解决大悬臂盖梁吊装重量大且难以实现预制拼装的技术难题,利用超高性能混凝土(Ultra-High Performance Concrete,UHPC)优异的力学性能,提出了采用由UHPC、钢板和型钢(Steel,S)制作的槽形组合结构作为永久模板,架设就位后浇筑普通混凝土(Normal Concrete,NC)的新型半预制预应力UHPC-S-NC盖梁.为研究其抗裂性能、刚度并对其安全性进行评估,结合实际工程,设计一片1∶2.5的大比例缩尺模型并进行全过程静力加载测试,获得了试验梁的变形特征、开裂荷载、裂缝开展、分布规律和应变等关键试验数据.分析了试验梁裂缝分布和应变发展规律;考虑材料塑性应力-应变关系,提出了结构UHPC层和NC层的开裂弯矩计算模式和计算方法;并根据截面平衡条件提出了组合结构的抗弯承载力计算模式,同时,依据规范对结构抗剪承载力的计算模式进行了探究.结果表明:新型组合盖梁结构具有施工快捷、装配化程度高等特点;开裂弯矩的计算结果与试验值吻合较好;采用平衡条件和叠加法评估结构的承载力,新型盖梁结构具有足够的承载能力,结果偏于安全;针对实际工程提出了一些具体的结构设计和施工的建议.研究成果可为半预制盖梁的应用提供参考.

To solve the technical problems of large lifting weight and difficulty to realize prefabrication and assembling of cantilevered bent caps,using the excellent mechanical properties of UHPC,a new type of semi-precast prestressed UHPC-S-NC non-demolition molded bent caps,with the use of groove-type combination structure made of UHPC,steel plate and steel section(S)as the permanent formwork,and the pouring of normal concrete(NC)after erection,were put into position.In order to study its crack resistance and stiffness and evaluate its safety,a 1∶2.5 large-scale scaled model was designed and loaded in the whole process in conjunction with the actual project,and key experimental datas such as the deformation characteristics of the test beams,the magnitude of the cracking and ultimate loads,and the pattern of crack development and distribution were obtained.The crack distribution and strain development law of the test beams were analyzed;considering the plastic stress-strain relationship of the NC material,the cracking moment calculation mode and calculation method of the structural UHPC layer and NC layer were proposed;and the bending capacity calculation mode of the combined structure was proposed based on the cross-section equilibrium condition,while the calculation mode of the structural shear capacity was explored based on the code.The results show that:the new type of bent cap structure has the characteristics of fast construction and a high degree of assembly;the calculation results of cracking bending moment are in good agreement with the test values;the new type of bent cap structure has sufficient load carrying capacity,and so it is suggested to use the equilibrium conditions and superposition method to evaluate the load carrying capacity of the structure,and the results are biased towards safety;some specific suggestions for the design and construction of the structure are put forward for the actual project.The research results can provide a reference for the application of semi-precast bent caps.