Construction Monitoring Of Continuous Double-layer Box Girder Bridge And Study On Hydration Heat Of Block Zero

Prestressed concrete continuous beam bridges are widely used due to their advantages such as large spanning capacity,beautiful linetype,and smooth driving.This type of bridge is usually constructed by the cantilever method.In order to ensure that the construction linetype and internal force meet the design requirements,it must be monitored.This project case—Jiyin Avenue across the Qinhuai River Bridge is a continuous concrete beam bridge of equal section.Due to the large span,large dead weight,and complicated forces,the section size of block zero is large,so the hydration heat is higher and more serious,it is necessary to carry out special research on it.Based on the linearity,stress,and temperature monitoring of the engineering case,this thesis combines model tests,finite element simulation,and theoretical analysis to conduct a systematic and in-depth study on the hydration heat of block zero.First of all,carry out construction monitoring on engineering cases: in terms of line shape control,adjust the full bridge line shape to meet the design requirements through line shape control of each segment;in terms of stress monitoring,stress monitoring is performed on the four stages of cantilever construction before the bridge closing.Later,the closed section is continuously monitored for stress during the prestressed tension;in terms of temperature monitoring,corresponding construction measures are taken in time according to the internal temperature of block zero in real time.Then the finite element software Midas Civil is used to simulate and analyze the zero block of the bridge.A 1/4 model of the block zero is established,and the correctness and accuracy of the 1/4model are verified comparising with the full model and the measured data.Finally,hydration heat parameter of block zero is analyzed,and the effects of the cement number and the amount of admixture on the temperature and stress of hydration heat in the concrete mix ratio are studied.The results show that the hydration heat can be effectively reduced by changing the amount of admixture.The influence in the temperature of the mold is analyzed,and the results show that the temperature of the mold has a greater effect on the peak internal temperature.The results show that the thickness of the web has a greater effect on the heating and cooling of the hydration heat of the web;the effects of the four types of cooling water pipe layout on the hydration heat are studied,and a recommended scheme is proposed.The effects of the cooling water flow and the cooling water temperature are also analyzed.