预应力RPC-NC结合梁裂缝试验研究

Experimental Study of Cracks in Prestressed RPC-NC Composite Beams

为研究预应力活性粉末混凝土(RPC)-普通混凝土(NC)结合梁的开裂性能,以铁路32m的T形梁为原型,制作10根RPC-NC结合梁和1根纯NC梁进行抗弯试验。对比分析试验梁的裂缝分布形态、裂缝间距及短期裂缝最大宽度,并在铁路规范的基础上推求适合于预应力RPC-NC结合梁裂缝宽度的计算公式。结果表明:预应力度增大,RPC-NC结合梁裂缝分布的范围减小;RPC-NC结合梁的裂缝间距明显小于NC梁,RPC加入后裂缝更加密集,并伴随产生大量细小裂缝;RPC高度对于RPC-NC结合梁裂缝出现及稳定发展阶段影响很小,进入失稳扩展阶段后随着RPC高度的增加,RPC-NC结合梁裂缝宽度增长速率降低;纯NC梁裂缝进入稳定扩展阶段后的扩展速率和裂缝最大宽度都明显高于RPC-NC结合梁;在铁路规范中引入结合梁裂缝修正系数后,能合理计算RPC-NC结合梁短期裂缝宽度。

To study the cracking behavior of the prestressed reactive powder concrete（RPC）-normal concrete（NC）composite beams,a 32-m span railway T-beam was taken as the prototype,10 prestressed RPC-NC composite beams and 1pure prestressed NC beam were cast and the flexural tests for these beams were made.The crack distribution patterns,crack spacing and the shortterm maximum crack width of the tested beams were compared and analyzed and the formulas that were appropriate for calculation of the crack width of the RPC-NC composite beams were derived on the basis of the railway codes.The results show that the scopes of the crack distribution of the composite beams diminish as the degrees of prestress increase.The crack spacing of the composite beams is obviously smaller than that of the NC beam and when the RPC is added,the cracks become denser and are accompanied with a great amount of the minute cracks.The depth of the RPC has very little effect on the occurrence and stable propagation stages of the cracks of the composite beams,however,after the cracks come into the instable propagation stage,the increase rates of the crack width of the composite beams decrease with the increase of the depth of the RPC.For the cracks in the NC beam,the propagation rates and the maximum width of the cracks in the stable propagation stage are all obviously higher than those of the cracks in the composite beams.The introduction of the correction coefficients of the cracks in the composite beams in the railway codes can properly calculate the short-term maximum crack width of the composite beams.