冻融环境下GFRP管混凝土柱轴压性能试验研究

Axial compression performance test of concrete-filled GFRP tube columns in freezing-thawing environment

通过对21个玻璃纤维增强聚合物(GFRP)管混凝土柱和21个素混凝土柱分别在水溶液和质量分数为3.5%的氯化钠(NaCl)溶液中进行冻融循环试验及轴压试验,且对冻融后的GFRP管混凝土柱进行了超声波检测,研究冻融环境下不同冻融介质和冻融循环次数对GFRP管混凝土柱轴压性能的影响。结果表明,冻融介质相同的情况下,随着冻融循环次数的增加,质量损失率增大,相对动弹性模量降低,GFRP管混凝土柱内异常点增多,承载力下降,极限应变下降;冻融次数相同的情况下,经盐冻作用的GFRP管混凝土柱轴压极限承载力降低更为明显。GFRP管混凝土柱盐冻循环150次后极限承载力下降了29.45%,下降量是相同条件下水冻结果的2.19倍。盐冻循环后的GFRP管混凝土柱极限应变小于相同条件下的水冻循环极限应变。

The purpose of this study is to evaluate the effects of different freeze-thaw agents and freeze-thaw cycles on the axial compression performance of concrete-filled GFRP tube columns. A freeze-thaw cycle experiment and an axial compression experiment were conducted on 21 concrete-filled GFRP tube columns and 21 plain concrete columns in aqueous solution and NaCl solution with a mass fraction of 3. 5 %. The ultrasonic experiment for the concrete-filled GFRP tube columns after freeze-thaw cycles was also performed. The results indicated that the mass loss rate and abnormal points of the GFRP tube columns increased with an increase in the freeze-thaw cycles in the same freeze-thaw agents, whereas the relative dynamic modulus, bearing capacity, and ultimate strain decreased. At the same freeze-thaw cycle numbers, the GFRP tubular columns showed a more significant decrease in the axial ultimate compressive strength after exposed to a saline environment. The GFRP tube columns also presented a decrease in the ultimate compressive strength by 29. 45 %after 150 saline freezing-thawing cycles. This result is 2. 19 times in water under the same conditions. The ultimate strain of the concrete-filled GFRP tube columns after the salt freezing cycle was less than that after the water freezing cycle under the same conditions.