无黏结预应力型钢混凝土框架梁静力性能试验研究及有限元模拟

为研究无黏结预应力型钢混凝土(UPSRC)框架梁的静力性能，对4榀UPSRC框架梁试件进行了竖向静载试验，主要的变化参数为框架梁中普通钢筋用量、型钢用量以及框架柱尺寸。对其裂缝发展、破坏模式、荷载-位移曲线、普通钢筋及型钢应变、无黏结筋应力变化等进行了分析。结果表明：UPSRC框架梁整体呈“梁铰”破坏机制，梁端及跨中出现塑性铰，截面转动能力强；达到极限荷载时，跨中及梁端受拉钢筋均屈服，部分受压钢筋屈服，型钢受拉翼缘基本屈服，受压翼缘则处于弹性工作状态；极限荷载后，UPSRC框架梁仍有较高的承载能力；无黏结筋应力增量与跨中挠度呈良好线性关系，且已有规范计算方法低估了UPSRC构件达到极限状态时无黏结筋的应力增量值；与型钢用量及框架柱截面尺寸相比，改变普通钢筋直径对UPSRC框架梁的极限荷载以及裂缝宽度的影响最为显著。利用ABAQUS有限元软件对试验进行了数值模拟。经分析发现，该模型可较好地模拟竖向荷载作用下UPSRC框架梁的力学性能。

Test and finite element study on static behaviors of unbonded prestressed steel reinforced concrete frame beams

To study the static behavior of unbonded prestressed steel reinforced concrete (UPSRC) frame beams, four UPSRC frame beam specimens were tested under vertical monotonic loads. The main parameters considered were the amount of rebar, steel shape and the dimension of column section. The development of cracks, failure mode, load-deflection curve, strain of reinforcement and steel as well as stress increment in unbonded tendons were investigated. Test results indicate that the UPSRC frame beams show a typical beam hinge failure mode and plastic hinges form at mid-span and beam ends. The rotation capacity of beam section was good. When reaching ultimate load, for UPSRC frame beams, tension rebar at mid-span and beam ends all yields, only a part of compression rebar yields, tension flanges nearly yield and all of the compression flanges are in elastic; after the ultimate load, UPSRC frame beam specimens still have a high load-carrying capacity. There is a good linear relationship between stress increment in unbonded tendons and mid-span deflection, and the method of relevant design code greatly underestimate the test results of stress increment under ultimate loading. Compared with the amount of steel shape and the dimension of frame column, the influence of rebar’s diameter on the ultimate load and crack width is much more significant. Moreover, a numerical simulation was conducted with the finite element software ABAQUS. It is found that the ABAQUS model can well simulate the mechanical behaviors of UPSRC frame beam specimens under vertical static loads.