Test On Mechanical Performance Of Steel Fire Reinforced Tunnel Segment And Analysis On Its Fire-resistance

In this paper, an extensive investigation was conducted to evaluate the mechanical behavior of tunnel segments. And the post-fire behavior of the segments was preliminarily analyzed. The main research work was summarized in the following:(1) Cube and prism specimens were designed and fabricated by C50 concrete with steel fiber or polypropylene fiber (PP) or both of them. With series temperature ranging from 20℃ to 800℃, the cooled specimens were tested and the degradation of the residual compressive strength and flexural strength were studied. It is found from this experimental investigation that the steel fiber is beneficial to both residual compressive and flexural strength.(2) 36 pieces of steel fiber reinforced concrete (SFRC) segments, especially for the low- reinforced SFRC segments were tested to evaluate the mechanical behavior and the results have been compared with those of normal reinforced concrete (NRC). It is shown that, the cracking load value of low-reinforced SFRC segments is about 240kN, while the NRC segments is about 220kN. The load when the crack width equal to 0.2mm is decreased 440kN to 420kN. The deformation of low-reinforced SFRC segments is better than that of the NRC segments.(3) The internal force and crack of segments at a certain case were calculated. It is proved that SFRC segments can improve the performance of segments in serviceability limit state and reduce the maximal crack width.(4) According to code of railway tunnel design and specification of SFRC, the formulae for the capacity calculation of NRC segments and SFRC segments were given both under room temperature and after elevated temperature, respectively. It is concluded that the SFRC segments have a better performance for the carrying capacity after high temperatures.