| As the span increases,buckling problems become increasingly prominent.Available designing equations for the stability capacity of CFST arches are in fitting forms which are not based on Perry theory.The equations are limited to the range of the finite element analysis parameters in regression analysis.In addition,in order to ensure that the prediction equations can meet the requirements of the structural safety,the reliability method should be used to evaluate the safety factor of the stability capacity of the CFST arch within the range of engineering parameters,but related research work is not systematic.In this paper,the circular cross-section parabolic CFST arch with fixed ends under uniform load along the span was adopted.The main work is as follows:(1)Based on the equivalent beam-column method,after determining the effective calculated length coefficient for the CFST arch and verifying the rationality of adopting the 1/4-span internal force as the representative value of the rib axial force,the equivalent defect factor in the Perry formula was modified by fitting available finite element analysis results to consider the difference in axial force distribution along the length of the effective arch segment and the equivalent column.By doing this,the prediction equations for in-plane and out-of-plane stability capacity of the CFST arch were proposed,which were in good agreement with the results of the finite element analysis.(2)In view of the fact that the main influence of the prebuckling deformation induced by time effects on the stability capacity is to increase the second-order effect,the creep magnification factor of the equivalent defect factor in the Perry formula for the creep buckling capacity of the CFST arch was derived to consider the preload effect on the initial deflection.Prediction equations for in-plane and out-of-plane creep buckling capacity of the CFST arch considering the effect of creep were proposed,which were in good agreement with the finite element prediction results.(3)All the basic random variables that influence the probability model for the creep buckling capacity of CFST arch were statistically determined by experimetal data from the literature,and the correlation coefficient between the model uncertainties and other random variables were obtained.Through comparative analysis,the necessity of considering the correlation between basic random variables was determined;and through sensitivity analysis,the key parameters that affect the discrete degree of creep buckling capacity were determined.Investigation shows that there is a correlation between the studied basic random variables.The standard deviation of creep buckling capacity of CFST arch will be 16% lower when ignoring the correlation,which will obtain dangerous results of reliability analysis.The key basic random variables affecting the probability model of the creep buckling capacity include the uncertainties in concrete strength and creep buckling equations for in-plane stability,and the uncertainties in concrete strength and concrete elastic modulus for out-of-plane stability.(4)Reliability analysis of CFST arch in this paper using the proposed equations with the safety factor and resistance factor given by the Technical Code for Concrete Filled Steel Tube Arch Bridges(GB 50923-2013)in China and the Bridge Design Specifications(AASHTO LRFD-2012)in the United States was conducted.And recommended safety factor and resistance factor were proposed.The research shows that,for in-plane creep buckling capacity,the safety factor provided by Chinese code can meet the requirements of the target reliability index;for out-of-plane creep buckling capacity,it is recommended to be adjusted to 2.05.The resistance factor provided by the US code cannot meet the requirements of the target reliability index,and modified values were recommended in this thesis. |
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