钢筋高强再生混凝土足尺梁长期荷载作用下变形性能试验研究

Experimental study on deformation performance of full-sized high strength recycled reinforced concrete beams under long-term loading

为研究钢筋高强再生混凝土梁长期荷载下的变形性能,进行了6根足尺梁试件变形性能试验研究。梁截面尺寸为200 mm×300 mm,长3 300 mm,净跨3 000 mm;各梁配筋相同,纵筋配筋率1.13%,体积配箍率0.54%,纵筋净保护层厚度20 mm;混凝土为再生粗骨料混凝土,细骨料为天然砂,再生粗骨料取代率分别为0%、33%、66%、100%,再生混凝土设计强度等级为C55~C60;针对两种不同持荷水平,进行了长期荷载试验。试验中得到了荷载、梁挠度、温度、湿度随时间的变化情况。分析了不同持荷水平、不同再生粗骨料取代率梁的挠度随时间变化的规律;拟合得到了挠度-时间关系曲线及其表达式。研究表明:低持荷水平下(加载弯矩与屈服弯矩比值为0.29)高强再生混凝土梁徐变挠度比天然骨料混凝土梁的略大,挠度增大系数比高持荷水平下(加载弯矩与屈服弯矩比值为0.46、0.47)的梁挠度增大系数略大;再生粗骨料混凝土梁长期荷载下挠度增大系数可按普通混凝土梁挠度增大系数的1.1倍采用;曲线拟合及分段线性拟合得到挠度计算值与实测值吻合较好。

To investigate the deformation performance of high strength recycled reinforced concrete beams under longterm loading,the long-term deflection tests of six recycled reinforced concrete beams were carried out. The beam cross section was 200 mm × 300 mm,and the length was 3 300 mm and the span was 3 000 mm. The reinforcement details of specimens were the same. The longitudinal reinforcement ratio was 1. 13% and the stirrup volumetric ratio was0. 54%. The concrete cover depth of longitudinal reinforcement was 20 mm. The strength level of recycled concrete was C55 ~ C60. The concrete was recycled coarse aggregate（ RCA） concrete,and the fine aggregate was natural sand. The replacement ratio of RCA included 0%,33%,66%,100%,and there were two loading levels. The test has already continued under long-term loading,and the load value,deflection,temperature and humidity have been recorded. The developing rule of beams＇ deflection of different loading levels and different replacement ratios of RCA were analyzed. The formula between deflection and time was obtained by fitting curves. Results show that： the creep deflection of high strength recycled reinforced concrete beams is slightly larger than the creep deflection of natural aggregate concrete beams under low loading level（ The ratio of loading moment to yield moment is 0. 29）. The deflection increasing coefficient under low loading level is slightly higher than that under high loading level（ The ratio of loading moment to yield moment is 0. 46 and 0. 47）. The deflection increasing coefficient of recycled concrete beams could adopt 1. 1 times of the deflection increasing coefficient of normal concrete beam. The calculated values of deflection obtained by curve fitting and piecewise linear fitting are in good agreement with the measured values.