Research On The Bending-torsion Behaviors Of The Curved Composite Beams In Construction Stage

When the curved composite beam construction without supports the wet weightof concrete completely borne by the steel beam.The steel beams not only subjected tobending-torsional coupling but also as low stiffness it appeared the danger of largedeformation or buckling.This paper relies on the National Natural Science FundProject "Research on the effect of diaphragm and the mechanism of bending-torsionbehaviors of the curved composite beams "(51108281), the main work andconclusions are as follows:(1)We make6pieces of curved composite beams for the construction phasestatic load test. Through experiments we find that the ratio of span to radius have littleeffect on bending moment and have more effect on torque but the number ofdiaphragm have little effect on the bending moment and torque,phased pour is greaterthan one-time pour of torque. Tangential strain along the cross section vertical accordwith flat section assumption. Tangential strain at a diaphragm along the cross sectionlateral changes in linear form. Tangential strain at no diaphragm in the form of twolarge middle small line changes. But they all show the curve of the lateral large andsmall inside;(2)Test results and ANSYS calculations show that the strain and displacement inall directions with the number of diaphragms, beam height increases, the increase inthe thickness of the diaphragm is reduced, but with the increase ratio of span to radiusit is increases, in phased pour it is smaller than one-time pour. Diaphragms for steelbeam webs have a significant role in lateral restraint, both ends of the diaphragms andmiddle span diaphragm to its larger role, when the diaphragms over five their impactdecreases;(3)The M/R method can better analysis curve girder torsion effect.Under theaction of in the distributed torque, vertical displacement, radial displacement, warpingnormal stress, warping stresses and bending stress ratio with the increase ratio ofspan to radius increases linearly, it is a non-linear decrease with increasing the number of the diaphragms and decreasing calculation of span, This suggests that thespan ratio is a dominant index reflects the degree of torsion of curved beam;(3)When phased pour method is used in curved composite beams constructionstage the Beam strain and displacement in all directions is smaller than the one-timepour,this description between steel beam and concrete slab early combination. Whenphased pouring time intervals between0.25~7d, we should be credited to earlycombined action between steel beam and concrete slab, and consider it along withconcrete age and growth characteristics. When the section have casted we must takeinto account the combination surface slip, otherwise it would cause a large error.