Papers by Author: Xu Jun Chen

Abstract: The fatigue failure modes of reinforced concrete beams externally strengthened with basalt fiber reinforced polymer(BFRP) sheets was examined in an experimental and analytical study. One strengthened beam failed due to the debonding and fracture of U-wraps FRP sheet at the anchors,and the others failed the fatigue fracture of the longitudinal tensile reinforcements. Based on Code for Design of strengthening concrete structure, the fatigue failure of RC bending members strengthened with FRP was analysed,and the indicate that with reinforcement ratio of 0.612% and fatigue stress ratio of 0.3, only the fatigue fracture of steel bars occured rather than the crushing of concrete in the compression zone.

Abstract: Many studies have focused on the flexural behavior of conventional reinforced concrete (RC) beams strengthened with fiber reinforced polymer (FRP) bonded on the bottom surface; however, rare attempt is made to strengthen RC beams with FRP bonded on the side surface, furthermore, as for the comparative study of the both is even more scarce.Based on the existing bending experimental data of RC beams externally strengthened with FRP, the flexural capacity calculation formula of normal section of RC beams strengthened with FRP bonded on the side or bottom surface was deduced in the paper. In addition, a comparative analysis on the strengthening effect between bottom bonded FRP and side bonded FRP was made. The results indicated that the ultimate load-carrying capacity of the former was slightly lower than the later.

Abstract: The flexural capacity formula of reinforced concrete structure strengthened with FRP in Code for Design of strengthening concrete structure(GB 50367—2013) was introduced, and the rationality of the formula was analyzed. The results showed that the concrete compression height is independent of the tension strength of Fiber Reinforced Plastic (FRP), and the concrete compression height decreases with the increase of the tension strain of FRP, which is contrary to fact. The flexural capacity formula of reinforced concrete structure strengthened with FRP in Code for Design of strengthening concrete structure (GB 50367—2013) is worth discussing.

Abstract: The influences which were caused by difference of produced methods and original concrete on the performance of recycled aggregate have been studied in this paper. Moderate reprocessing of recycled aggregate can effectively improve the performance. Higher strength matrix concrete, better the performance of recycled aggregate, and the recycled concrete strength will be higher also. Original concrete has little effect on the performance of recycled aggregate.

Abstract: Based on the fatigue test for flexural performance of five reinforced concrete beams, the variation characteristics of the crack development, concrete strain, steel strain, fiber strain with the cycle number of the fatigue load were analyzed, and the effect of hybrid fiber sheets and basalt fiber reinforced polymer(BFRP)sheets on flexural fatigue performance of the strengthened beam was studied. The results show that the accumulated damage of RC beams strengthened with hybrid fiber sheets was slowed down significantly, the anti-crack property was much improved, and the fatigue life was greatly prolonged. Compared with the ordinary RC beam and the RC beam strengthened with double BFRP sheets, the fatigue life of RC beams strengthened with hybrid CFRP/BFRP(C/BFRP) sheets and hybrid CFRP/GFRP(C/GFRP) sheets was increased by 291.26%, 298.63% and 10.73%, 13.53%.

Abstract: An optimum reticulated shell structure is selected and its dynamic properties are analyzed. In this paper analyses the dynamic feature and gains the elementary parameters from the analysis of free vibration. The frequencies and modes are compared by two finite element methods. The paper analyzes the dynamic responses of the reticulated shell structure subjected to two-dimensional and three-dimensional earthquake waves respectively. Simultaneously analyses the linear，geometric nonlinear and both geometric and material nonlinear dynamic responses in two situations. The nodal displacements and stresses of members are compared and analyzed. The characteristics of elastoplastic seismic responses of the structure are revealed and the basic rules are obtained.