Safety Assessment of Fire Damaged Cable-Stayed Bridge

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During winter thunderstorm on the evening of December 2015, one of the longest upper cables of a cable-stayed bridge caught a fire. The 990-m long cable-stayed bridge consists of three cable-stayed spans of 200 m + 470 m + 200 m and two 60-m long end spans of simply-supported composite girders. The fire started almost 80m above the bridge deck and lasted more than two hours. As fire progressed, the cable was completely severed and two more cables were partially damaged. Because of fire and severe damage, the bridge was immediately closed to traffic for 15 days for safety assessment and cable replacement. To check the structural safety and operability of the fire-damaged bridge, the detailed structural analysis using a three-dimensional finite element model was carried out considering dead and live loads. The tension forces of the cable and compressive stresses of the stiffening girder were especially studied in detail. The tension force level of the cables and overall geometry of the bridge was also studied using the measured data from the structural health monitoring systems (SHMS). The structural health monitoring system has been continuously monitored changes in cable tensions as well as overall geometry of the bridge since the bridge was constructed.