Lateral stiffness is a basic component property in the design of a tall pier.To investigate the effects of axial compression ratio and relative height to thickness ratio of a low-yield-point(LYP)steel plate on the lateral stiffness of an innovative tall pier with rectangular concrete-filled steel tubular(CFST)columns and a replaceable LYP steel plate composite box section,quasi-static cyclic tests were conducted on four tall pier specimens.The preliminary test results indicate that the specimens with composite box sections have sufficient initial lateral stiffness to meet the displacement limit requirement at the top of the tall piers during the elastic stage,and the lateral stiffness might decrease by 32％-53％when elastic-plastic buckling occurs in the LYP steel plates.Furthermore,extensive parametric analyses were conducted to explore the influence of the key factors on the lateral stiffness of the tall piers with composite box sections by verified finite element models.The parametric analysis shows that axial compression ratio and both relative height-thickness ratio and yield strength of the LYP steel plate have little effect on the initial elastic lateral stiffness;the post-buckling lateral stiffness is closely related to the relative height-thickness ratio of the LYP steel plate:when the relative height to thickness ratio decreases from 200 to 100,the buckling and the minimum lateral stiffnesses increase by 37％and 48％,respectively.By simplifying the tall pier with a composite box section as that with multiple CFST columns linked by LYP steel plates,the practical formulas for the initial elastic and buckling lateral stiffnesses were established,respectively.The theoretical calculation results agree well with the experimental and numerical results,and the latter can be used to estimate the minimum lateral stiffness of the tall pier with medium or thick LYP steel plates after a severe earthquake ground motion input.
bridge engineeringlateral stiffnessparameter analysiscomposite tall pierpractical calculation formula
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