预应力CFRP板加固钢-混凝土组合梁受弯性能试验

为研究钢-混凝土组合梁经预应力碳纤维板加固后的受弯性能,设计4根预应力碳纤维板加固试件和1根不加固的对比试件. 5根试件均为工字形钢-混凝土组合简支梁,采用四点弯曲静力加载.锚固装置为自主研发的装配式预应力碳纤维板锚固系统,碳纤维板与钢梁之间的锚固主要依靠端部锚具,并辅之以专用环氧胶的黏结作用.试验中考虑碳纤维板的加固量和预应力水平两种因素对加固效果的影响.结果表明:加载全过程截面应变基本符合平截面假定;增大碳纤维板的加固量能提高钢-混凝土组合梁的抗弯极限承载力;增大碳纤维板的预应力有助于提高钢-混凝土组合梁的屈服承载力,对结构抗弯刚度贡献有限;破坏阶段碳纤维板有断裂和剥离两种形式,其强度利用率可达到80%以上.所采用的锚固系统锚固力大、可靠度高,工程实用价值大;预应力碳纤维板加固钢-混凝土组合梁,能有效提高结构的抗弯承载力,是一种补强效果很好的主动加固技术.

Test on flexural behavior of steel-concrete composite beams strengthened with prestressed carbon fiber-reinforced polymer plates

To investigate the flexural behavior of steel-concrete composite beams strengthened with prestressed carbon fiber-reinforced polymer (CFRP) plates, a total of five large scale steel-concrete composite beams including one control unstrengthened beam and four strengthened beams were prepared and tested with static load in a simply supported four-point bending setup. Welded I-beam was used for the structural steel section of all specimens. An innovative fabricated anchorage system was developed to prestress the CFRP plates attached to the bottom flange of the steel beams. The connection between the CFRP plates and the steel beams both depended on flat-plate anchors and epoxy resin adhesive. The strengthening effects of the method using CFRP plates of different thicknesses and different prestressing forces were investigated. Experimental results showed that the strain distribution along the cross-section conformed to plane-section assumption during load application. The specimen strengthened with thicker CFRP plate exhibited a higher ultimate bearing capacity. The yield bearing capacity increased and the mid-span deflection slightly decreased with increase of prestressing force. The CFRP plates failed due to rupture or debonding under ultimate condition and a great portion of tensile strength was employed (up to 80% on average). The fabricated anchorage system can provide strong anchoring force and is proved to be feasible and practical. The prestressed CFRP plate for strengthening steel-concrete beams improves the flexural behavior and is an efficient technique in bridge strengthening and rehabilitation.