锚贴U形钢板-混凝土组合加固RC梁的抗弯试验

为了研究锚贴U形钢板-混凝土组合加固钢筋混凝土梁的抗弯性能，设计5根加固梁和1根对比梁进行抗弯试验。试件的主要设计参数包括有无加载历史、钢板纵向加固长度、钢板厚度和螺杆间距。加载仪器采用1 000 kN梁柱加载系统，应变采集使用静态应变分析系统，挠度采用机电百分表测量。试验过程中，观测记录试验梁在荷载作用下截面应变、跨中挠度、加固部分与原混凝土之间的相对滑移、裂缝的产生与发展。基于平截面假定，推导试验梁的极限抗弯承载力计算公式，并对比模型试验与理论分析结果。试验结果表明：与未加固的对比梁相比，锚贴U形钢板-混凝土组合加固后的试验梁其开裂弯矩提高近50%，极限抗弯承载力提高约1倍；钢板纵向加固长度对梁的整体刚度有显著的影响，加固范围越大刚度提升越显著；加固范围应充分考虑加固部分截断处截面的抗剪能力，避免使试件从塑性弯曲破坏模式变成脆性剪切破坏模式；对比螺杆间距15 cm与30 cm试验梁的结果发现，只要符合构造要求的螺杆间距对试件的承载能力影响很小，但对裂缝开展有一定的影响，螺杆间距越密其裂缝开展明显变小；随着加固钢板面积增大，抗弯承载力也随之提高。针对加固后适筋破坏的RC梁，推导了极限抗弯承载力计算公式，利用公式计算出的极限抗弯承载力的理论值与试验值相对差值均在10%以内。

Bending Behavior Experiment of RC Beams with U-shaped Steel and Concrete Composite Reinforcement

To study the flexural performance of reinforced concrete beams strengthened with anchored U-shaped steel and concrete composite, five beams and one unstrengthened beam were designed for the bending test. The major design parameters were included loading history, longitudinal length of shaped-steel, thickness of shaped-steel and screw bolt space. The loading instrument was 1 000 kN beam-column loading system, the strains were collected by static strain analysis system, and the deflections were measured by electromechanical dial indicators. The section strains, mid-span section deflections, the slippages between shaped-steel and old concrete, cracking propagation of test beam under loads were respectively measured. Based on the assumption of plane cross-section, the formulas of bearing capacity of the test beam were derived, the results of model test and theoretical analysis were compared. The experimental results show that compared to unreinforced contrast beams, the cracking moment and ultimate bending capacity of RC beams strengthened by anchored U-shaped steel and concrete composite can be increased by 50% and 1 time respectively, The longitudinal reinforcement length of steel-plate have obvious effects on the reinforcement effect, the greater the range of reinforcement, the more significant the stiffness increase; The shear strength of the section at the truncated part of the reinforcement should be fully considered in the reinforcement scope to avoid the failure mode of the specimen from plastic bending to brittle shear failure mode; comparing the results of test beams with screw bolts spacing of 15 cm and 30 cm, it is found that as long as the screw bolts spacing meets the structural requirements, there is little influence on the bearing capacity of specimens, but certain obvious influence on the development of cracks; The closer the screw bolts spacing is, the smaller the development of cracks will be; With increase in the area of the added steel plates, the flexural bending capacity is also improved. In view of the flexural bending capacity of reinforced concrete beams by moderate destruct form, the calculation formula for the ultimate bending capacity is derived.The relative difference between the theoretical value and experimental value is within 10%.