Abstract:To study the dynamic response law of large diameter variable cross-section single pile in liquefaction sites under different ground motion intensities， shaking table tests were conducted. Employing the 5010 wave and subjecting the system to ground motion strengths ranging from 0.10g to 0.45g， this study examined the evolution of sand pore pressure ratio， horizontal displacement at the top of the piles， bending moment along the pile body， as well as the time history response of pile acceleration and foundation damage. The test results show that the pore pressure ratio of saturated sand increases obviously with the increase of ground motion strength. The pore pressure ratio of saturated sand increases obviously with the increase of ground motion intensity. When the ground motion intensity is ≥0.30g， the stable value of the pore pressure ratio of saturated sand is near 0.9， and the sand is completely liquefied. Under the action of 0.45g ground motion， the acceleration of pile body， the horizontal displacement of pile top and the bending moment of pile body all reach the maximum. The peak acceleration at different positions along the pile body lags behind that of the input seismic wave， and the acceleration response of the pile top and variable cross-section is weaker than that of the pile tip. The maximum bending moment of the pile appears at the boundary between the liquefied soil layer and the non-liquefied soil layer， and the bending moment at variable cross-section is smaller than that at the soil layer interface. When the ground motion strength reaches 0.30g， the damage of a large diameter variable cross-section single pile occurs. Therefore， in the seismic design of the single pile foundation of a large diameter variable cross-section bridge under a liquefaction site， the bending capacity at the boundary of the saturated sand layer and variable section should be considered to ensure that the strength of the single pile meets the anti-seismic requirements.

Abstract:To study the shear performance of segmental prefabricated continuous composite box girder with corrugated steel webs， two scaled test beams were made， including segmental continuous box girder with variable section corrugated steel webs and monolithic continuous box girder with variable section corrugated steel webs in the same size. Through static tests and numerical analyses， the distribution of shear stress and shear ratio of corrugated steel webs are obtained. The results show that the shear stress of the corrugated steel webs of the segmental and monolithic beams at 1/4 of the mid-span is evenly distributed along the beam height， and the shear stress value of the segmental beams is greater than that of the monolithic beams. The calculation formula of shear stress of segmental assembly box girder with variable section corrugated steel webs is derived， and the effect of construction technology on shear stress is considered. The shear ratio of corrugated steel webs of two test beams is less affected by the load and maintains a constant ratio. The shear ratio of the steel web of the two test beams at the position of the middle support is about 50%， and increases along the longitudinal direction of the test beam to both sides. At the position of 1/4 of the middle span， the shear ratio of the steel web of the segment-assembled beam reaches more than 85%， and the shear ratio of the steel web of the whole beam is about 75%. The shear ratio of the two testing beams at the corresponding position of the side span is not much different. The shear strength calculation formula of the AASHTO joint applicable to segmental concrete box girder multiplied by 0.9 can be applied to the calculation of the shear bearing capacity of the joint section. The error between the above formula value and the experimental value as well as with the finite element result is about 5 %. It can better predict the shear strength of steel-concrete composite structure adhesive joints.

Abstract:In order to study the shear performance of variable cross-section corrugated steel webs, firstly, based on the theory of orthotropic plate and the theory of small deflection of thin plate, the calculation formula of elastic overall shear buckling strength of corrugated steel webs is deduced by Galerkin method. Secondly, the calculation value of the derived formula is compared with those of ANSYS finite element and code formula. Moreover, the derived value of the formula is also compared with the experimental value in the literature. Finally, the influence of different types of corrugations, web thickness and girder height on the elastic shear buckling behavior of variable cross-section corrugated steel web is studied by using the finite element method. The results show that the calculated value of the derived formula is in good agreement with that of the finite element method and test value. Because the contribution of Dxy to the global shear buckling strength of the corrugated steel web is ignored in the specifications formula, the calculation of the value of the specifications is more conservative. With the increase of the corrugated size, the shear buckling strength generally increases first and then decreases, where the shear performance of the 1600 corrugated steel web reaches the maximum. With the increase of the web thickness, the shear buckling strength increases gradually. The shear buckling strength of the variable section corrugated steel web is greater than that of the constant section corrugated steel web. With the increase of the angle β between the girder bottom and the horizontal direction, the shear buckling strength of the variable section corrugated steel web increases. The conclusion can provide a reference for the shear design of the same type of bridge.