Study On Calculation Method Of Spacing Space Of Steel-concrete Combined Box Girder For Railway

As the steel-concrete composite beam has the advantage of saving steels,construction convenience,low cost,high load ability,good seismic performance and structural stability,it has developed into the third type of structure besides steel structure and concrete structure,which is widely used in highway,railway and building structure currently.However,when the curved composite beam with a flat curve under load,it will generate complicated bending,shearing and torsional coupling effect.At present,the domestic and foreign research on this aspect still needs to be further deepened.This paper is based on national natural science foundation of china research on bending-torsion coupling mechanism and the calculation theoretic study of prestressed concrete curvde composite beams with corrugated steel webs(51778377),The torsional distortion effect of single-box single-chamber and single-box multi-chamber curved composite beams was studied and The suggested formula for calculating the spacing of diaphragm is derived,the major jobs and conclusions are as follows:(1)For curved composite beam with single box single chamber which center line bisects the middle vector,namely curved beam straight do.The finite element model of elastic foundation beam with constant section is established.The secion of mid-span and maximum torsion-bending ratio(1m cross-section from the support)were considered as the most unfavorable loading positions to be loaded respectively,we can come up with that the distortion stress and the distortion angle of the midspan section are large but the distortion stress ratio is small.When the number of diaphragm increases gradually,The concentrated stress will produce distortion stress concentration at the section with diaphragm;(2)For curved composite beam with single box double chamber,the curved beam is also used to make the straight beam.The plate element model consistent with the actual structure is established.It is found that the distortion effect reaches its maximum near the bearing.The first distortion is larger than the second distortion stress,which indicates that the first distortion is the main distortion and the second distortion is the secondary distortion.At the cross section of the diaphragm,there is a sudden change of distortion stress and torsion stress,which proves the effect of the diaphragm on distortion and torsion;(3)The single-box and double-chamber curved composite beam is made of curved beam,that is,the center line of the left line along the beam body is arranged,and the support is arranged in the radial direction.The plate element model consistent with the middle span of the continuous beam is established.It is verified that the M/R method is also applicable to the continuous curved composite beam exemplified in this paper.The M/R method is used to simplify the middle span into a straight beam;when the 1/4 span of mid-span is used as the most unfavorable loading position,the torsion-bending ratio has the maximum value;the first distortion stress and the torsional stress obtained under different loads are antisymmetrically distributed along the cross section,and the second distortion stress is symmetrically distributed along the cross section;(4)The regression analysis method is used to explore the relationship among the number of the diaphragms,the ratio of the calculated span to the radius of curvature,the spacing of the diaphragms and the distortion stress ratio of the curved composite beams.The formula for calculating the spacing of the diaphragm and the diaphragm is obtained by derivation.And establish a number of finite element models to verify it,and the results are in agreement with the results of the proposed formula.It is stated that when the desired distortion stress ratio is given arbitrarily,the proposed diaphragm formula can be used to calculate the spacing of the diaphragms required for the railway curved composite beam.