Study On Influence Of Mid-Span Deflection Of The Continuous Rigid Frame Bridge By The Concrete Elastic Modulus

Continuous rigid frame bridge has the advantages of low expansion joint,the good continuity deck.Meanwhile,it is convenient for operation as well as big stiffness.Last but not the least,it has a good earthquake resistance,which are the main reason for it’s widely used and build in bridges.However,in the operation we found that this type of bridge easily down-warped on the cross.According to the research,the loss of prestress,concrete creep and the decrease of the main girder stiffness are the main cause of downwarped on the cross.while the elastic modulus of concrete and the construction phase is the important influential factor.Elastic modulus is one of the important parameters which reflect the stress and deformation of concrete.continuous rigid-frame bridge structure,as a prestressed concrete structure.Whether the prestress have influence on the beam body,mainly to see whether the concrete have enough stiffness to fight the tensile deformation during the prestress’ resistance to its tension.This paper takes the bridge under construction as the engineering background,mainly finished the following work by surrounding the concrete elastic modulus:1.To make the concrete specimen by following the construction progress.research concrete elastic modulus according to the early and late two stages.First,study the concrete’s modulus of elasticity at the age of 3 d,4 d,7 d,14 d and 28 d.Secondly,to make specimen in production of each segment.Analysis the development situation of concrete elastic modulus in each segment of the whole bridge at the late stage and the final development value.2.During construction,following the concrete age phases to test each section of the concrete strength,get the law of development of different concrete strength at different ages from the cantilever to pouring out.3.According to measured the concrete strength of the push to get the modulus of elasticity,we can see the construction of the modulus of elasticity in 3 days time can reach about 69.3% of the design value,after that the development is very slow.It will needed at least five months to meet the design value.4.According to the engineering situation bridge model is established by using Midas Civil software,analysis of the bridge’s across the middle of the scratch in different concrete elastic modulus and different load combinations,the result shows that the value is bigger under the condition of elastic modulus of deviation,the continuous rigid frame bridge across the middle and lower torsion is serious,especially at 0.6 E.5.By analyzing the effect of the combination of elastic modulus and strength of concrete on the mid-span deflection,the results show that the effect of strength on midspan deflection is less than the influence of elastic modulus on deflection6.Because the concrete elastic modulus of the impact is embodied by shrinkage and creep,and the annual average relative humidity is an important factor that calculation of creep and shrinkage.Analysis the bridges through the software under different humidity across the middle of the scratch.the result shows that with the increase of relative humidity,across the middle and lower torsion decreases.7.During construction,the deflection of concrete modulus of elasticity under construction age is mastered by measuring the deformation of concrete at each section before,after and after prestressing,results show that the elastic modulus in the design rules fluctuate in construction process is not obvious influence on downwarping.