Behavior of square pultruded GFRP tube filled with seawater and sea sand concrete beam

The behavior of square GFRP tube beams filled with seawater and sea sand concrete under the four-point test was studied with 48 specimens. The main test parameters of this study included cross section size, GFRP tube thickness, and sea sand replacement ratio. The failure process of the specimen during the four-point test was studied. The reslut indicated that the effect of GFRP tube strengthening core concrete on the failure process was significant. There was no apparent elastoplastic stage before the specimen failed, thus the failure mode was brittle under test, which could be found from the load-displacement curve. In addition, the effects of these test parameters on the ultimate capacity, flexural rigidity, and ductility were analyzed in this study. The test results indicated that the effects of GFRP tube thickness on the ultimate capacity and flexural rigidity were significant. The replacement of normal concrete with sea sand concrete had no obvious negative effect on the mechanical properties of the GFRP tube beams filled with concrete. Furthermore, the calculated formula of the ultimate capacity of the GFRP tube beams filled with seawater and sea sand concrete was proposed in this study. The calculated results were compared with the test results, which indicated that the calculated formula was greatly agreed with the test.