Research On Pile Cap Cracking Resistance Of A Large-tonnage T-type Rigid Frame Bridge Constructed By Rotation Method

In recent years, with the development of the bridge construction, more andmore bridges with large-span and large-tonnage chose rotation construction method.In order to ensure the rotation construction completed perfectly, it is essential tomonitor the process of rotation system. These large-tonnage rotation bridges not onlyneed accurate rotation system, but also need large scale, high quality, and excellentstability pile caps. This paper introduced systematically the monitoring of theJingbao Railway Disconnect-type overpass Bridge program, and analyzing thecracking resistance of pile cap. The main research work of this paper includes suchaspects:(1)This paper introduced the main factor of early cracking of large-scaleconcrete. It is the hydration heat of cement which causes uneven tension stressinterior of the concrete. The temperature field and temperature stress field after theconcrete pouring ten days were simulated by ANSYS software, and comparisonbetween the calculation results and the field test results was made to verify thenumerical simulation method was feasible.(2)Compared two main design methods of pile cap: control section method andthe spatial truss model method. The bearing capacity of the pile cap had beenanalyzed separately based on the effective height of pile cap, for effective heights ofpile cap in rotation construction were different in the construction process. Moreover,the key parts in the pile cap were analyzed subtly to ensure the global pile cap wasmet the requirements of design.(3)Three typical conditions: stage before the weighing test, stage after theweighing test, and stage after packaged were chosen to analyze and to illustrate thestress path model and the failure mechanism of pile cap in rotation construction.(4)Random load was simulated through the field measured random vibrationdata. The responses of the pile cap under the random load were studied, and themaximum stress points of the steel plate were found.(5)With the specification and the measured field temperature data, temperature cracking resistance recommendations were provide; with the software results and thestress path model, the load cracking resistance recommendations were provide.This research indicated: the temperature stress and the large vertical load werethe two main factors cause pile cap cracking in rotation construction oflarge-tonnage T-type rigid frame bridges. The pile cap stress in the stage beforeweighing test was the most disadvantageous stress state. These cracking resistancerecommendations provided through the analysis of the rotation construction processcould guarantee the safety of the pile cap.