# Review on the Service Safety Assessment of Main Cable of Long Span Multi-Tower Suspension Bridge
## 5 Research Trends in Service Safety Assessment of Main Cable  
Load-bearing safety and anti-sliding safety of main cable are evaluated by the load-bearing safety factor and anti-sliding safety factor, respectively. At present, the load-bearing safety factor of main cable is mostly based on the determined suspension bridge model and designer experience, which causes the unknown actual safety degree of main cable, uneconomic design, and difficulty in maintenance decision-making [47]. The formula of anti-sliding safety factor is based on [PERSON]'s formula of friction transmission of flexible body, which only considers the dry friction between main cable and the bottom surface of saddle groove of the saddle [42]. Therefore, the calculated value is difficult to evaluate the anti-sliding safety between main cable and saddle accurately. In fact, the load-bearing and anti-sliding safety factors of main cable of long-span multi-tower suspension bridge over the sea and river are both affected by design parameters of suspension bridge and environmental conditions such as temperature, wind (wind load, wind speed, wind attack angle), and electrolyte corrosion solution (salt concentration and pH value). At present,  
\begin{table}
\begin{tabular}{l c c} \hline \hline
**Bridges** & **Tested Coefficients of Friction** & **Brief Introduction** \\ \hline George Washington Bridge and Forth Road & 0.30 & Measured value of real bridge \\ Bridge [54] & 0.19–0.21 & During loading and measuring processes of the three bridges, \\ Kan-mon Bridge [54] & 0.15–0.21 & the slip time is not clear enough and the error is large \\ Honshu-Shikoku Bridge [54] & 0.16–0.44 & Testing results corresponding to the saddles with inorganic \\ Tokyo Port Link Bridge [54,55] & 0.31/0.60 & zinc rich paint and zinc coating, respectively \\ Yangluo Bridge in Wuhan [56] & 0.14–0.33 & The contact stress between cable strand and saddle during \\  & & the test is smaller as compared to the real bridge \\ Yingwuzhou Yangtze River Bridge [25] & 0.27–0.33 & Sliding tests between main cable and saddle with different \\  & & diaphraggs \\ Taizhou Yangtze River Bridge [57,58] & 0.53 & Mean value of test results of 10 strands \\  & 0.31 & Mean value of test results of a strand \\ \hline \hline \end{tabular}
\end{table}
Table 1: Testing results of coefficients of friction.  
we are not clear about the relationships between loading-bearing capacity/safety factor and tribo-corrosion-fatigue damage of main cable. Meanwhile, dynamic contact and micro slip mechanisms between main cable and saddle and the anti-sliding safety factor under coupled roles of temperature, electrochemical corrosion and time-varying dynamic load have not been reported yet. Besides, main factors affecting the service safety of the main cable are still not clear. Therefore, it is of great importance to obtain relationships between load-bearing/anti-sliding safety factors of main cable and influencing factors of temperature, time-varying dynamic loads and tribo-corrosion-fatigue damage. Moreover, we have to associate the load-bearing capacity and anti-sliding safety factor with environmental conditions and design parameters of suspension bridge. Finally, optimized design parameters of a suspension bridge are proposed to improve the service safety of the main cable of long-span multi-tower suspension bridges. This is of great theoretical significance to improve the service safety of main cable and to ensure the structural safety of long-span multi-tower suspension bridge.