EXPERIMENTAL STUDY ON FLEXURAL PROPERTIES FOR SEGMENTAL PRECAST GIRDERS OF ULTRA-HIGH PERFORMANCE CONCRETE
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摘要: 为研究预应力超高性能混凝土(UHPC)拼装梁的受弯性能,完成了5片试验梁,研究参数主要为有、无拼接缝,键齿类型及预压应力。获取了试验梁的破坏模式、受拉区钢绞线应力增量、荷载-挠度曲线及应变分布规律。试验发现:试验梁均呈现典型的弯曲破坏,受压区UHPC均压碎,破坏时受压边缘的最大压应变可达7.2×10-3以上,无论是否设置拼接缝应变沿截面高度的分布规律基本满足平截面假定;与整浇梁裂缝不同,拼接梁的弯曲裂缝主要集中在拼接缝位置;UHPC试验梁均具有较好的延性,且拼接梁的延性优于整浇梁;预压应力会影响试验梁的开裂荷载,但对极限荷载的影响较小;UHPC拼装梁比同条件下整浇梁的抗弯承载能力低9%~15%,接缝构造对抗弯承载能力也有一定影响,多齿构件承载力比同条件下单齿构件的低4.5%,平齿构件承载力比多齿构件的低5.7%。基于试验分析发现美国国家公路交通管理学会AASHTO标准节段梁设计提出的接缝折减系数基本适合UHPC节段拼装梁,但折减系数还应与键齿类型有关。Abstract: In order to study the flexural properties for segmental pracast girders of prestressed ultra-high performance concrete (HHPC), 5 test girders were completed, and the study parameters were mainly with or without joints, tenon forms and compressive prestress of UHPC. The failure modes, stress increments of steel strands in the tensive zones, load-deflection curves and strain development laws of the test girders were obtained. The test results showed that all the test girders presented typical flexural failure, and the UHPC in the compression zone was crushed. In the damage case, the maximum compressive strain at the compression edge could reach more than 7.2×10-3, and the strain along the section height basically met the plane-section assumption and had nothing to do with the joints. Moreover, different from the cracking characteristics of integal casting girders, the cracks of the segmental precast girders mainly occured in the joint. The UHPC girders had good ductility, and segmental precast girders had better ductility than integal casting girders. The prestress influenced the cracking load of the girders but it had little effect on the ultimate load. The flexural capacity of the precast girders were 9% to 15% lower than that of the integal casting girders subjeted to the same compressive prestress, and the forms of joints also influenced the flexural bearing capacity. The bearing capacity of girders with multi-tenon joints was 4.5% lower than that with the single-tenon joint, and the bearing capacity of the flat-tenon members was 5.7% lower than that with the multi-tenon joint. Based on the experimental analysis, it was found that the reduction factor for joints proposed by the AASHTO specification for segmental girder design was basically suitable for the UHPC precast segmental girders, but the reduction coefficient should further considered the type of joint.
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Key words:
- segmental precast girders /
- UHPC /
- flexural capacity /
- joint /
- unbonded prestressing tendon
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