| The concrete-filled steel tubular(CFST)arches have been widely used in China because of its good mechanical performance and beautiful shape.More than 400 CFST arches have been built or under construction up to now,and the maximum span length of CFST arches are longer than 500 m.The increasing slenderness ratio of the arches and the decreasing width-to-span ratio of bridges induced by the increasing span length of the bridges is likely to lead to the out-of-plane buckling of the arch.For the through arch bridges,the lateral displacement of the cables is restricted at the original position by the bridge deck system,so the arches are subjected to non-directional loads.According to the available research,the out-of-plane ultimate capacity of arches subjected to the nondirectional loads can be 2.5~3.0 times higher than that of arches subjected to vertical loading.In this context,it is necessary to account for the effect of non-directional loading in the design of such arches.However,the available equations for predicting the buckling loading with the consideration of non-directional loading effects were obtained from elastic buckling theory.For the case when both the geometrical and material nonlinearities were considered,the available research only forcused on some particular arch bridge applications.No systemic analysis has been done to draw general conclusions.In this context,a parametric study using finite element analysis method has been carried out to investigate the non-directional loading effect on the ultimate loading resistance capacity of arches accounting for both geometric and material nonlinearity.The main contents include:1)Failure test was carried out on the parabolic CFST arch with single circular crosssection to investigate its mechanical behavior and failure mode.In this test,the vertical loads were equally applied on the arch by five cables evenly distributed along the arch span.The arch was fixed on the ground at both ends and the five cables were also pinned on the ground.By comparing the displacement measuring results obtained from the LVDTs and that obtained from the total station,reliable displacement measurement system was specified for the tests on the out-of-plane buckling behavior of slender CFST arches.The strains in representative sections of arch were measured to investigate the stress states and the confining effect.The results of failure test have shown that the arch finally failed in out-of-plane buckling mode,the section of the arch was subjected to small eccentricity and the confining effect already occurred before loads reaching to the peak value.2)The finite element model was established using ABAQUS.The finite element model was benchmarked against experimental data.The boundary conditions,element types,element mesh,material constitutive model,geometrical imperfection and method of analysis were determined by comparative analysis.Based on the analysis results,the concrete constitutive model considering the confining effect was suggested to be used in the finite element modelling for CFST arches subjected to non-directional loads that uniformly distributed along the arch span.The finite element model was reliable according to the good agreement between the prediction results and the test data.3)Parametric analysis was conducted to investigate the influences of the rise-to-span ratio,the slenderness ratio,the steel ratio,the concrete strength and the steel yielding strength on the stability capacity of the CFST arches subjected to non-directional loads that uniformly distributed along the arch span.Based on the analysis results,the key parameters influencing the non-directional load coefficient which is defined by the ratio of the stability capacity under non-directional loads to that under directional loads have been specified.Equations for predicting the non-directional load coefficient of the through CFST single-rib arches were proposed.The calculated results of the formula agreed well with that of the finite element analysis results. |
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