Decay Law of Prestress at Concrete Box Girder End Under Fire Condition(PDF)
《建筑科学与工程学报》[ISSN:1673-2049/CN:61-1442/TU]
- Issue:
- 2016年03期
- Page:
- 65-71
- Research Field:
- Publishing date:
Info
- Title:
- Decay Law of Prestress at Concrete Box Girder End Under Fire Condition
- Author(s):
- ZHANG Gang; LIU Tian-long; SHI Ying; XUAN Ji-ming
- School of Highway, Chang’an University
- Keywords:
- bridge engineering; concrete box girder; finite element method; prestress; fire condition; high temperature
- PACS:
- -
- DOI:
- -
- Abstract:
- In view of the problem of prestress loss at girder end caused by section damage of concrete beam bridge under fire, the conduction mode of high temperature in fire and the mixed boundary conditions of heat conduction were studied. The fire scene in prestressed concrete box girder was set, and the decay model for strength and stiffness of concrete in high temperature and calculation method of burning damage layer were proposed. The timehistory variation curves of steel strands prestress at concrete box girder end in different fire scenes were calculated by means of thermomechanical coupled method and submodel analysis method. The time varying state of different steel strands prestress of concrete box girder end section was analyzed through engineering example. The decay law of prestress at concrete box girder end under fire condition was revealed. The calculation formula of prestress decay at concrete box girder end was put forward through comparison and analysis of the best and worst fitting curves. The results show that the variation trend of steel strands prestress in the upper part of web at box girder end is affected by fire area. The prestress increases with the increase of fire time when the fire area is smaller at the bottom of beam, and the increase trend is gentle. The prestress gradually decays with fire time extension when fire area enlarges at the bottom of beam. The steel strands prestress in the middle of web at box girder end always decreases with the increase of fire time. The steel strands prestress in the lower part of web decreases obviously with the increase of fire time. The final decay value of steel strand prestress at girder end is 94%96% of initial value at normal temperature when fire time is 120 min. The proposed calculation formula of prestress decay at concrete box girder end is simple, and can provide basic data for fire resistance design of similar end structure of prestressed concrete box girder.
Last Update: 2016-06-01