ABSTRACT
Based on the classic Newmark model, variational method, the Timoshenko beam theory and the Hamilton principle, a set of vertical bending vibration differential equations of the steel-concrete composite small box girder connected by group studs is deduced and established by taking account of the shear lag effect, shear deformation of the beam and the slip effect between concrete slab and steel beam. Comparing The values obtained by the proposed theoretical method with the results by the finite element method and experiment test verified its effectiveness and accuracy. In final, the depth-span ratio and shear stiffness of group studs parameters analysis show that the increase of depth-span ratio in combination box girder make the 1st -4th order vertical natural frequencies of the girder significantly increase. Taking the natural vibration frequency of the beam at the depth-span ratio of 0.06 as the reference, when the depth-span ratio increases from 0.06 to 0.13, the 1st -4th order natural vibration frequency of the composite girder increases to 220.9%, 223.7%, 199.9% and 208.0% of the original frequency values respectively. When the relative stiffness K/KSPB3 of studs varies from 1×10-5 to 1×104, the first-order frequency variation range of the composite girders is 0.591∼1.033.The second-order frequency ranges from 0.822 to 1.370.
