新老混凝土组合梁混凝土收缩徐变试验研究

进行了预应力作用下新老混凝土组合梁混凝土收缩徐变的试验研究,包括组合梁的挠度-时间曲线、混凝土应变-时间曲线及预应力损失的测定.试验结果表明,由于混凝土的收缩徐变,在预应力作用下组合梁的挠度、混凝土应变、新老混凝土界面间的应变差、截面曲率随时间的增长明显增加.虽然界面间的混凝土应变差值在逐渐增加,但是滑移值较小,界面间的粘结可靠.预应力前期的损失较大,随着时间的增长,损失逐渐减小.采用规范给定的混凝土收缩徐变模型分析了预应力损失.在试验研究的基础上采用随时间变化的换算弹性模量建立了新老混凝土收缩徐变的有限单元法,为了验证建立的有限单元法的正确性,对试验梁进行了分析.计算结果表明,建立的有限单元法与试验值吻合较好.

Experimental study on creep and shrinkage of old and new concrete composite beams

Two old and new concrete composite beams were tested to investigate the concrete creep and shrinkage under prestressing forces.The deflection-time curves,concrete strain-time curves and prestressed losses were observed.The test results show that the mid-span deflection,concrete strain and curvature are increased with the time extending.The bond between old and new concrete interface is strong enough to prevent interface slip.The prestressing losses are large correspondingly at initial stage and then the prestressing losses are gradually decreased with the time increasing.Based on the code for design of highway reinforced concrete and prestressed concrete bridges and culverts,the prestressing loss is calculated.A FEM(finite element method)is presented using the age adjusted effective modulus.The proposed FE model is compared to experimental beams.The calculated results show that the proposed FEM can predict the long-term structural behavior of composite beams.