The Application of Stiffness-Internal Force Adjustment Method in Widening and Reinforcement of Old Highway Bridges

Stiffness-internal force adjustment is a method which is applied in widening and reinforcement of old highway bridges. This method is that two new beams with larger rigidity are respectively built on both sides of the old bridge in order to make the old bridge unloading through the stiffness-internal force adjustment. This me- thod was successfully used for the reinforcement of Yingjing Bridge. Based on calculation by the SAP, the bending moment and shearing force of the bridge´s side beams reduced more than 40% under the live load and the bending moment reduced about 30% under the most unfavorable load. The load test after reinforcement showed that everything of Yingjing Bridge is normal, without traffic interruption during the construction period, and the cost of reinforcement was only 44% of the conventional reinforcement´s. This method was also succ- essfully used for the reinforcement of Guanlanhe Bridge. Based on calculation by ANSYS, the maximum stress of the old beam´s top and bottom unloaded more than 50% and the overall stress of the old beam unloaded more than 20% under the most unfavorable load. The calculation also showed that the maximum crack width of whole bridge decreased to 0.06 mm, the traffic wasn´t interrupted during the construction period and the economic benefit was high. These achievements provide some references for widening and reinforcement of this kind of bridge in the future.