The Reliability Analysis Of The SFRC Segments Based On The Serviceability Limit States

Presently, the reinforced concrete (RC) segments are used as the shield linings are heavy and easy to breakage in the course of conveyance and installation, so it destroys the global property of the lining and it is easy to occur the phenomenon of leakage and corrosion, they bring the disadvantageous influences to the security and durability of the tunnel structure. The unique capabilities of the steel fibre reinforced concrete (SFRC) can remedy the disadvantages of RC segments preferably, but the researches and applications of the SFRC segments are restricted interiorly. Therefor, this thesis analyses the reliability of the SFRC segments in the serviceability limit states based on tests to obtain the specific comparing data of the SFRC segments and the RC segments and confirm the principal influence factors of reliability index and the optimal mix quantity of the steel fibre.According to the calculating equation of the crack width of concrete structural element, the thesis establishes the limits tate equation and confirms the random variable;then basing on the cube resisting compression test of the concrete, the bend test of the SFRC trabecula and the eccentric compression test of SFRC constructional element and segments, considering the serviceability limit states of the SFRC structural element controlled by the cross crack width (relative to the length direction of the segments), handling the test data and combining with the codes and literature cites to get the statistical results of the random variable;using the center point method as the reliability calculating method to carry through the reliability analysis of the SFRC structural element.The results of the reliability analysis indicate that the reliability index of the SFRC structural element basing on the serviceability limit states controlled by the cross crack width is relatively low;the influencing factors of the reliability index of the SFRC structural element are plenty, but the major factors are the load, the elastic ratio of the reinforcing steel bar, the tensile strength of the concrete, the effective height of the section, the influencing coefficient to the crack width of the steel fibre and the characteristic coefficient of the steel fibre content;when changing the RC segments used in the shield tunnel to the SFRCsegments and reducing the diameter of the reinforcing steel bar and adding proper quantities of the steel fibre, it will improve the reliability index;basing on the reliability index of the serviceability limit states and the cost of the segments, the optimal breed and the mix quantity is G62-35.Basing on the capability of the regular service, the thesis carries through the contrast research on the RC segments and the SFRC segments and it makes some active effect to popularize the application of the SFRC segments.