# Review on the Service Safety Assessment of Main Cable of Long Span Multi-Tower Suspension Bridge
## 4 The Service Safety Assessment  
Considering the load-bearing safety of main cable, [PERSON] and [PERSON] [45] evaluated the safety factor of main cable of long-span suspension bridge based on the inverse reliability method. [PERSON] [46] calculated relevant parameters of main cable at typical locations according to standards in different countries (Table 2 in Ref. [46]) and suggested the safety factor of 2.3 of main cables for Chinese long-span suspension bridges. Meanwhile, he proposed the calculation method for the safety factor of main cable considering secondary stress and verified the enough safety reserve of main cable when selecting the safety factor of 2.3. [PERSON] et al. [47] proposed the factors affecting the bearing capacity of main cable at stages of cable design, cable construction, operation phase of bridge and maintenance phase of main cable. During the stage of cable design, the safety factor was introduced to ensure the cable safety, while the safety factor is based on the suspension bridge model and designer's experience, and the actual safety degree of main cable is undetermined. During the cable construction stage, he indicated considerations of the control of main cable shape, the wire fracture caused by construction process, damages of outer steel wires of main cable attributed to the excessive clamping force of cable clamp, and secondary stresses of main cable caused by constraints of cable clamp and saddle. During the operation phase of a bridge, corrosion, fracture of steel wires, and moment of inertia of the bending section of the main cable at bending segment greatly affected the loading conditions of main cable. [PERSON] [48] proposed that the wrapping angle of main cable around the saddle greatly affected the performance of main cable at the saddle; it was found that maximum equivalent stresses of main cable and clamp with the clamping force was greater than that without clamping force (Table 5.1 in Ref. [48]). [PERSON] et al. [49] dynamically monitored tension forces of separate cable strands of main cable of the long-span suspension bridge, derived the overall tension force of a main cable, and conducted the load bearing capacity assessment using concept of safety factor. With long-term monitoring data, monitoring-based evaluation methods could provide critical information to assess safety and serviceability performance of main cables. In the aspect of anti-sliding safety of main cable, [PERSON] et al. [7] studied the effect of middle tower stiffness on the critical span of sliding instability between main cable and saddle of multi-tower suspension bridge, and found that the anti-sliding safety coefficient was related to the span and ratio of dead load to live load. [PERSON] [21], [PERSON] et al. [50], and [PERSON] et al. [51] proposed analytical calculation methods for anti-sliding safety factor between main cable and saddle of middle tower of multi-tower suspension bridge, studied effects of sag-span ratio, span, middle tower stiffness and ratio of dead load to live load on the anti-sliding safety factor of main cable. It was found that an increase of the ratio of tower stiffness to cable stiffness caused a decrease in the anti-slip factor. The effect of sag-span ratio on the anti-sliding factor depended on the tower stiffness. Increases of span length and ratio of dead load to live load induced an increase in the anti-sliding factor. [PERSON] et al. [52] proposed that the anti-sliding safety factor was equal to the ratio of friction force between main cable and saddle to the tension difference of main cable at both sides of saddle, and discussed the effects of saddle design parameters on anti-sliding safety factor. [PERSON] et al. [53] evaluated anti-sliding safety between main cable and saddle of middle tower of long-span suspension bridge. He found that the assessment of anti-sliding safety of saddle was more conservative when geometric nonlinearity of live load was not included.