Analytical Method On Semi-rigid Joint Of Framework Based On Correlations

In traditional semi-rigid analysis of joint of framework, design variables of joint are assumed to be deterministic parameters, such as, general experiment analysis, finite element parametric analysis and theoretical analytical method. Namely, once the variation of a parameter is focused on studying influencing mode and influencing degree on structure response, the other paramerters are fixed on their basic values. The effect of correlations between parameters is neglected. Many researchers had proposed moment-roataion models of different connections. However, most of the models are determined by curve-fitting and statistically regressed with the test data, and have a lot of human elements. The moment-rotation models are close agreement with experimental results, but those parameters of the models have little physical meaning, or a negative stiffness may occur within the working range of the connection. It is therefore still necessary to propose a new analytical method based on parameters correlations to select and refine a simple and accurate mathematical expression to represent the constitutive relation of semi-rigid connection behavior for a frame analysis with flexible joints.As a part of National Natural Science Foudation of China"Standard Method Study on Behavior of Joints of Framework"(50678098), this paper is first time to propose a method study based on parameters correlations to analyze constitutive relation of joint of framework.Firstly, the influencing parameters of semi-rigid were summed up and classified for some typical joints. Bivariate correlation analysis and partial correlation analysis for geometric influencing parameters were carried out. The correlations of geometric influencing parameters were attained.Secondly, deterministic and probabilistic sensitivities of the geometric influencing parameters were analyzed based on finite element probabilistic design analysis. According to correlations and the regression lines of scatter plot between geometric parameters and rotation of the joint, an especial expression between geometric parameters and moment-rotation was discussed. An analytical method for moment-rotation elastic model was developed. The constant coefficient of the model was determined with partial derivative of the model. The parameters of the new moment-rotation model have notable physical meaning and should be accurate and acceptable.Based on the above analysis, considering influencing parameters, the probabilistic sensitivity analysis of three typical joints was carried out. They were the joint of steel beam to CFST (concrete-filled steel tubular) column with stiffening ring, the continuous web plate joint of steel beam to CFST column and the joint of extended end plate connections. The moment-rotation elastic models for three joints were put forward respectively with above moment-rotation analytical method. The moment-rotation elastic model was validated by experimental results of a frame analysis with the flexible joints. Furthermore, the probabilistic sensitivity of the frame was analyzed and good agreetment with the formulation of lateral rigidity.Finally, a new analytical method based on parameters correlation is proposed to determine a mathematical expression to represent the constitutive relation of semi-rigid for joint of framework. Applying the method, the curve-fitting and statistically regressed model could be judged renewedly. The influencing mode and influencing degree on structure responses could be more accurate. The parameters of the model have notable physical meaning. The model is simple and has the advantage over tradditional moment-rotation models, benefit to understand and use for engineer.