a b s t r a c tA bias-corrected technique for constructing the empirical likelihood ratio is used to study a semiparametric regression model with missing response data. We are interested in inference for the regression coefficients, the baseline function and the response mean. A class of empirical likelihood ratio functions for the parameters of interest is defined so that undersmoothing for estimating the baseline function is avoided. The existing data-driven algorithm is also valid for selecting an optimal bandwidth. Our approach is to directly calibrate the empirical log-likelihood ratio so that the resulting ratio is asymptotically chi-squared. Also, a class of estimators for the parameters of interest is constructed, their asymptotic distributions are obtained, and consistent estimators of asymptotic bias and variance are provided. Our results can be used to construct confidence intervals and bands for the parameters of interest. A simulation study is undertaken to compare the empirical likelihood with the normal approximation-based method in terms of coverage accuracies and average lengths of confidence intervals. An example for an AIDS clinical trial data set is used for illustrating our methods.
Finite element analysis (FEA) method is used to study the mechanical properties of headed studs for composite truss joint. The results show that the shear forces in the first few rows of headed studs are much greater than others. The shear forces in the rear headed studs decrease gradually. This study shows that the stiffness of headed studs, the layout of headed studs, and the steel backing plate are the main influencing factors on shear forces of headed studs. It is also expected that the results presented in this paper would be useful as references for the further research and the design of composite truss bridge and composite joint.
The main span is the steel truss and the side spans are the composite truss in Minpu Bridge. A 1:2.5 model is made to study the mechanical behavior of the joint segment of steel truss and composite truss. Both a model test and a numerical finite element analysis(FEA) method have been conducted. The results show that the joint segment remains in a linear elastic state under the condition. The maximum stress in the structure is less than the material allowable strength. The FEA results are in very good agreement with those of model test. This study shows that the force transformation of the joint segment is reliable and the composition details are rational. It is also expected that the results presented in this paper would be useful as references for the further research and the design of composite truss bridge and joint segment.
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