Structural Safety Assessment and Traffic Control Strategies of Widened Highway Bridges under Maintenance Works Requiring Partial Lane Closure

Abstract

An increasing number of existing bridges need to be widened due to the rapid growth of road transport. Owing to the discontinuities in design specifications for the new and old structures in the widened bridges, it is expected that the old bridge might fail to meet the new design standard, leading to a potential need for vastly retrofit or even totally reconstruction. However, the new and old bridges carry slow and fast traffic lanes respectively, resulting in an uneven distribution of traffic loads between them. A previous study indicated that most components of the old bridge possessed adequate security reserves under normal traffic conditions of all lanes open. However, there are occasional scenarios that the new bridge requires closing traffic lanes to perform maintenance works. Under such circumstances, the traffic is completely diverted from the new bridge to the old bridge, and the safety of the old bridge becomes a critical issue. This study proposes a numerical approach to investigate the structural safety of widened bridges under maintenance works requiring partial lane closure on the new bridge and recommends traffic control measures to ensure bridge safety. The results show that several old slabs are unsafe under the maintenance works requiring lane closure. The weight restriction with a limit value not exceeding 35 t can ensure the safety of the widened bridge, whereas speed control is not effective. The hybrid uses of weight restriction and speed control further enhance the safety of the bridge. When the speed limit is 60 km/h, the weight limits should be not greater than 50 t and 45 t for the one-lane and two-lane closure scenarios, respectively. The research findings are of benefit to bridge engineers when maintenance works requiring lane closures are planned on widened bridges.