Evaluation Of Load-bearing Capacity And Strengthening Techniques For In-service Deck Reinforced Concrete Arch Bridges

Reinforced concrete arch bridges are aesthetically pleasing,have clear forces and are easy to construct,making this bridge type widely used in China in the early days.Before repair and strengthening,it is necessary to carry out reasonable calculations and analysis,so as to assess the bridge bearing capacity and finally propose effective repair and strengthening measures.This paper summarises the current research results on load carrying capacity assessment and strengthening at home and abroad,assessing the current situation of existing reinforced concrete arch bridges,exploring the applicability of strengthening methods,and analysing and comparing the load carrying capacity before and after strengthening.The main research contents and conclusions are as follows.（1）According to the current code,the appearance inspection and load test were carried out on site,and finite element model was established,from which the bearing capacity check coefficients Z1 and Z2 were assumed,and theoretical analysis was made on the control section of the structure to comprehensively assess the actual condition and bearing capacity of the arch bridge in service.The results show that the bridge is rated as a Class IV bridge,the load carrying capacity of the foot of the main arch ring is seriously inadequate,the hollow slab of the main bridge and the T-beam of the approach bridge have insufficient bending capacity in the span,and need to be strengthened for the foot of the main arch ring,the hollow slab of the main bridge and the T-beam of the approach bridge.（2）The reinforcement scheme is proposed.The arch footings are reinforced by the increased section method,and the hollow slab of the main bridge and the T-beam of the approach bridge are reinforced by the paste method.Using finite element software MIDAS/FEA to establish a model for refinement analysis,considering material non-linearity and geometric non-linearity,through the most unfavourable vehicle axle weight increase,define the tensile zone reinforcement reaches yield strength,at this time,the bridge is in the limit state,and according to the"Specification for Strengthening Deign of Highway Bridge"（JTG/T J22-2008）to calculate the design bearing capacity of the reinforced section,the calculation results show that.The bearing capacity after reinforcement is greatly improved,the reinforcement effect is obvious,the bearing capacity at the foot of the arch meets the design requirements,and the safety factor of the hollow slab as well as the T-beam is further improved.（3）Continuing with the testing and load testing programme before strengthening,the load carrying capacity of the reinforced concrete arch bridge in service after strengthening was determined as Z₁ and Z₂,and the load carrying capacity of the bridge after strengthening was indirectly assessed,and it was found that the safety factor of the bridge was improved compared with that before strengthening.（4）On this basis,considering the large traffic flow of the bridge,different special heavy-duty convoys were given a passage scheme.The results of the study showed that:through strengthening,the bridge bearing capacity meets the design requirements,three-axle,five-axle and six-axle vehicles are allowed to pass in a single lane,the spacing between convoys is 15m or more,70t crawler crane,hanging-100 and hanging-120 can only pass one at a time,and generator stator The generator stator is not allowed to pass.