Prestressed Concrete Skew Box Girder Analysis Of Experimental And Theoretical Studies

This paper studies the analyzing method, the linear and nonlinear behaviors and the ultimateload of prestressed concrete skewed box girders by means of the derivation of formula deduction, numerical calculation and model tests. The main proposals are as following1.Presenting the calculating method of the space displacement model of skewed box girder, whit main ideas of~ dispersing the skewed box girder into some skewed beam segments and further dividing those segments into some plate pieces according to their forms; describing the displacement functions in the plane of plate piece by assuming that the space displacements of any point in the joint line between the plate pieces are described by using Hermite interpolation functions and that two displacements in the plane of plate piece are linear in the cross direction; Using l-lermite interpolation functions to describe the bending the displacement of the unit length transverse frame cutting longitudinal from the skew box girder segment; Finally, describing the space displacements of a point in the plate pieces by two displacements in the plane of the plate and one bending displacement of plate. There is no the global angular rotation but only the space displacements of the nodes (induding the cantilever plate) in this space displacement field. Thus, greatly simplify the calculation of the geometric nonlinear analysis by not necessarily adopting the coordinate transformation using Euler angle.2.Presenting the method describing the space displacements of the element in the skew coordinate system by means of building the formula of coordinate transformation between the orthogonal coordinate and the skew coordinate.3.Presenting the method of calculating the elastic strain energies of skewed box girder element according to the deformation of the middle plane of the plate and the bending of the plate. This method simultaneously indudes various strain energies due to the flexure, tensile and compressive deformation, shear, warp of the box section and shear lag etc and can overcome the disadvantages caused by calculating strain energy according to single deformation.4.Based on stationary potential principal and?sit-in-right-position 搉ile, presenting the finite element method of plate beam segment of skewed box girder to analyze the orthogonal or skewed box girders and the composite element of the tendons, reinforcements and concrete to analyze the nonlinearity of prestressed concrete structures.5.Presenthe the analyis method of the ultimate load ofskeWd box girders which sedates andanalpses the process from the beginnin of loading, ereck, vielding to destrUchon by comhan thedrite segment valled shffuess integh method and the stress reease of concrete crack, basing onthe drite elernent method of plate beam segInent of skewd box girder the prestressed concretecomPosite eletnent, mechhocs of plashdty and the mated conshtUtive relation. Presendrigclementary comParative stUdy betWeen Chen--Chen thre parameter concrete modd and Hintondoublc parameter concrete model u1 the nonlineary anhais.6. Having vcofied and oproved the "skewed beam drite eletncnt" and doned the formch ofthe drite e1ernent of skewed restrAnt orthogonal beam element wtth l2 dopes. T'Iha elernentintroduces sedtaneously 3-D opd ans, which can amLhate the eccentrioty of node.7. Destwg and constrUcdrig the lf8 modcl beam of 3 spans skewd continuous bearn. Thebehavors of the modd under the semce 1oads and failurc load are obsewed. and the distribuhonsof stress, displacemcnt reachon force, crack distribuhon diagram and load-displacement ores areobdried. The perfect accordance of theorehcal analysis and the resultS of the eapments vertfythe reliability of theorehcal method of linear and norilinear analyis and the prOgrams.8. Developmp two pWs: the hoear and nodriear analysis prOgram PBS of skewd boxghder Plate bearn segrnent bote elernent and the elashc analysis prOgrams SB of skewd restrhotorthogOnal beatn drite elernent. Antheing some d...