| In 2016,the Ministry of Transportation officially issued relevant documents to further promote the application of the steel structure and the steel-concrete composite structure,which shows that these kinds of bridges have broad application prospects in China.The steel-concrete composite bridge makes full use of the mechanical properties of the two materials.And the research on the key mechanical problems has also made abundant achievements,but the existing researches on the construction techniques and the flexural capacity of the steel plate-concrete composite beam are not sufficient.Meanwhile,the contributions of the concrete slabs and the steel flange slabs to the web boundary constraints are not considered for the local stability of composite structures.Therefore,relying on the standard section of a 40m span steel composite bridge of the Tiansheng bridge in Yunnan Province,and on the basis of the existing research results,this paper mainly focused on the the bending mechanics of the steel plate-concrete composite beam with the following works completed.1.Research on the influence of the composite time on structural stress and economic benefit of the composite structure.Based on the engineering background,four different construction techniques were proposed while considering the composite time of the steel plate and the concrete slab.Then,the corresponding finite element models were established to study the influence of the composite time on structural stress and a relative evaluation formula of the bridge economic benefit was put forward to evaluate the economy of each construction technique.The results show that the construction technique of“combining steel with the precast concrete bridge deck first,and then hoisting and erecting”have the advantages of a good stress state,low steel consumption,and the significant total economic benefit.Therefore,the composite girder bridge can be widely constructed by this technique in the practical engineering.2.Comparative study on the flexural capacity of the steel plate-concrete composite beam under different theories.Based on the plastic flexural capacity calculation theory in the codes at home and abroad,this paper improved the calculation method of the elastic calculation theory,and put forward the elastoplastic flexural capacity calculation theory after considering the steel strain strengthening.Then,the flexural capacity of the relying project bridge was calculated under these theories.The results show that the plastic flexural capacity of the same section is about 1.2 times of the elastic flexural capacity.And the section flexural capacity is increased by 10%after considering the steel strain strengthening and the actual section stress distribution.It is also proved that the calculation method in this paper is in good agreement with the finite element results,which can provide a reference for the flexural capacity calculation of composite structures.3.Study on the shear buckling after considering the influence of the restraints from the concrete slab and the steel flange slab.Firstly,in this paper,the relationship between the dimensions of the composite structure and the rotational restraint coefficientβwas established,and the critical shear buckling stress under differentβcases was studied.The results show thatτcr is increased by 1.20 times after considering the influence of the restraints from the concrete slab and the steel flange slab.Besides,a large number of numerical analysis shows that when 0<β<10,τc r increases with the increase ofβ,and whenβ>10,τcrtends to be constant.Then,the suggested formula of the fixed coefficient was put forward,and the calculation error was less than 1%.Finally,taking the relying bridge as an example,the maximum spacing of transverse stiffeners was calculated.The calculation method in this paper can effectively reduce the number of transverse stiffeners,which is beneficial to economic benefits of the composite bridge and relatively reliable. |
