Analysis Of Health State On A T-shaped Rigid Frame Bridge During Operation Period

It has been very widely used as soon as the appearance of T-shaped rigid frame bridge in the second half of the last century. With the growth of operating time and long-term vehicle load effects, T-shaped rigid frame bridges are easy to generate diseases of deflection, displacement, etc., which will affect the safe use of the bridge structures. It has a certain theoretical and practical engineering significance to provide the basis for conservation, reinforcement and repair of bridges by assessment of health state on T-shaped rigid frame bridges during operation period, analysis of the degree of damage to bridge structures, evaluation of load capacity and safety of bridges according to periodic inspection and long-term monitoring data of bridges.In this paper, based on long-term deformation monitoring and periodic testing on a T-shaped rigid frame bridge in Guangdong Province, MIDAS CIVIL is used for finite element modeling and analysis calculations. This article also analyzes the health state of the bridge combined with regular testing bridges, long-term deformation monitoring and static load test. The result shows:(1) Two diseases are obvious. One is down deflection of the cantilever end in this bridge, another is transverse displacement of the suspended girder. The main factors of down deflection of cantilever end are shrinkage and creep, pre-stressing loss and temperature effects, etc., and the main factors of transverse displacement of suspended girder may be asymmetric down deflection of corbel, bearing separation and transverse loading.(2) The affection of the bridge deflection with shrinkage and creep of concrete is time-dependent, and the deflection occurs mainly within one year after the completion of the bridge, then gradually stabilized. The amount of down deflection in pre-stress loss condition substantially has a linear correlation with pre-stress reduction factor. Warming effect will slightly increase the deflection in the side span and generate substantial arch to offset the disease of down deflection in the main span of the bridge. Vice versa when cooling effect.(3) Asymmetric down deflection of corbel has an inconspicuous influence with transverse displacement of suspended girder. Bearing separation will increase transverse displacement, and the influence of a bearing separation is more obvious than two bearing separations. The transverse displacement is bigger while the wind speed is faster, but the winds blowing from the outside are good for the suspended girder outward disease on the side span.(4) This bridge has operated safety for 20 years. Since 2007, the bridge has a smooth linear and a small change with deflection. Regular testing results shows that the bridge still has some diseases, such as sands in expansion joints, a slight separation in bearing, peeling of concrete cover for the components and corrosion of steel, etc.. Static load test results indicate that currently structural performance could meet the design requirements.Analysis of this paper proves that transverse displacement of the suspended girder and deflection changes of main bridge are the result of many factors working together. Although the bridge deflection monitoring shows that both deflection changes and transverse displacement are not large, and the stress state is good since the reinforcement of the bridge. We still need to detect and predict structure diseases timely and to ensure the safety of the bridge during operation period by long-term health monitoring and periodic checks.