Numerical Analysis Of Converting Simply-supported Beams Into Continuous Beams For Strengthening Old Bridges With Self-stressing Method

During the sixties and seventies in the 20th century, there were large numbers of unitconstruction simply-supported bridges of reinforced concrete built in our country. During theoperating period, a goodly part of the bridges were damaged with different degrees, at thesame time the defect and disease of the bridges exposed day after day. Now the bearingcapacity of the bridges is not able to adopt the need of the vehicular load and need to bestrengthened and reconstructed immediately. The reconstructing and strengthening techniqueof changing multi-span simply-supported T-beams of old bridges into continuous beams is aneffective method to increase their class of loading, which is applied widely in strengtheningsimply-supported bridges of moderate and small spans. This paper focuses on calculating andanalyzing the effects of actions on the models before and after strengthening by the largefinite element analysis software ANSYS. The details are listed as follows:1. Based on ANSYS software and taking an old simply-supported T-beams bridge withfive spans (5~*22.2m) changed into continuous bridge for example, the author puts forward thebearing capacity of the bridge after strengthening, as well as rechecks and compares theinternal force and displacement of the structure before and after strengthening.2. To reduce negative moment and to avoid too much reinforcement nearby supports,which is bad for construction, the steel fiber reinforced self-stressing concrete is suggested tobe used, for its expansive action is able to restrict the shrinkage of concrete. The computedresults indicate that it is much effective.3. The number of diaphragms for models of simply-supported beams and continuousbeams is changed, and the transverse distribution coefficient of each beam under vehicularload is calculated. According to the transverse distribution coefficient, the effects of thenumber of diaphragms for lateral rigidity of bridges are analyzed. Based on the analysis, thereasonable number of diaphragms for continuous beams is proposed.4. The number of spans for models of continuous beams is changed from 2 spans to 5spans, and the design value of combination for worst-case actions effects at control sectionsof each beam is calculated. According to the results of calculation, the design value of moment for different models is compared. Based on the difference, a reasonable model ofcontinuous beams is proposed.