Purpose–Under different ground motion excitation modes,the spatial coupling effect of seismic response for the arch bridge with thrust,seismic weak parts and the internal force components of the control section of ma...Purpose–Under different ground motion excitation modes,the spatial coupling effect of seismic response for the arch bridge with thrust,seismic weak parts and the internal force components of the control section of main arch ribs are analyzed.Design/methodology/approach–Taking a 490 m deck type railway steel truss arch bridge as the background,the dynamic calculation model of the whole bridge was established by SAP2000 software.The seismic response analyses under one-,two-and three-dimension(1D,2D and 3D)uniform ground motion excitations were carried out.Findings–For the steel truss arch bridge composed of multiple arch ribs,any single direction ground motion excitation will cause large axial force in the chord of arch rib.The axial force caused by transverse and vertical ground motion excitation in the chord of arch crown area is 1.4–3.6 times of the corresponding axial force under longitudinal seismic excitation.The in-plane bending moment caused by the lower chord at the vault is 4.2–5.5 times of the corresponding bending moment under the longitudinal seismic excitation.For the bottom chord of arch rib,the arch foot is the weak part of earthquake resistance,but for the upper chord of arch rib,the arch foot,arch crown and the intersection of column and upper chord can all be the potential earthquake-resistant weak parts.The normal stress of the bottom chord of the arch rib under multidimensional excitation is mainly caused by the axial force,but the normal stress of the upper chord of the arch rib is caused by the axial force,in-plane and out of plane bending moment.Originality/value–The research provides specific suggestions for ground motion excitation mode and also provides reference information for the earthquake-resistant weak part and seismic design of long-span deck type railway steel truss arch bridges.展开更多
The study of mooring forces is an important issue in marine engineering and offshore structures.Although being widely applied in mooring system,numerical simulations suffer from difficulties in their multivariate and ...The study of mooring forces is an important issue in marine engineering and offshore structures.Although being widely applied in mooring system,numerical simulations suffer from difficulties in their multivariate and nonlinear modeling.Data-driven model is employed in this paper to predict the mooring forces in different lines,which is a new attempt to study the mooring forces.The height and period of regular wave,length of berth,ship load,draft and rolling period are considered as potential influencing factors.Input variables are determined using mutual information(MI)and principal component analysis(PCA),and imported to an artificial neural network(NN)model for prediction.With study case of 200 and 300 thousand tons ships experimental data obtained in Dalian University of Technology,MI is found to be more appropriate to provide effective input variables than PCA.Although the three factors regarding ship characteristics are highly correlated,it is recommended to input all of them to the NN model.The accuracy of predicting aft spring line force attains as high as 91.2%.The present paper demonstrates the feasibility of MI-NN model in mapping the mooring forces and their influencing factors.展开更多
Local domain structures of ferroelectrics have been studied extensively using various modes of scanning probes at the nanoscale,including piezoresponse force microscopy(PFM)and Kelvin probe force microscopy(KPFM),thou...Local domain structures of ferroelectrics have been studied extensively using various modes of scanning probes at the nanoscale,including piezoresponse force microscopy(PFM)and Kelvin probe force microscopy(KPFM),though none of these techniques measure the polarization directly,and the fast formation kinetics of domains and screening charges cannot be captured by these quasi-static measurements.In this study,we used charge gradient microscopy(CGM)to image ferroelectric domains of lithium niobate based on current measured during fast scanning,and applied principal component analysis(PCA)to enhance the signal-to-noise ratio of noisy raw data.We found that the CGM signal increases linearly with the scan speed while decreases with the temperature under power-law,consistent with proposed imaging mechanisms of scraping and refilling of surface charges within domains,and polarization change across domain wall.We then,based on CGM mappings,estimated the spontaneous polarization and the density of surface charges with order of magnitude agreement with literature data.The study demonstrates that PCA is a powerful method in imaging analysis of scanning probe microscopy(SPM),with which quantitative analysis of noisy raw data becomes possible.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.51768037)“Foundation of A Hundred Youth Talents Training Program of Lanzhou Jiaotong University.”。
文摘Purpose–Under different ground motion excitation modes,the spatial coupling effect of seismic response for the arch bridge with thrust,seismic weak parts and the internal force components of the control section of main arch ribs are analyzed.Design/methodology/approach–Taking a 490 m deck type railway steel truss arch bridge as the background,the dynamic calculation model of the whole bridge was established by SAP2000 software.The seismic response analyses under one-,two-and three-dimension(1D,2D and 3D)uniform ground motion excitations were carried out.Findings–For the steel truss arch bridge composed of multiple arch ribs,any single direction ground motion excitation will cause large axial force in the chord of arch rib.The axial force caused by transverse and vertical ground motion excitation in the chord of arch crown area is 1.4–3.6 times of the corresponding axial force under longitudinal seismic excitation.The in-plane bending moment caused by the lower chord at the vault is 4.2–5.5 times of the corresponding bending moment under the longitudinal seismic excitation.For the bottom chord of arch rib,the arch foot is the weak part of earthquake resistance,but for the upper chord of arch rib,the arch foot,arch crown and the intersection of column and upper chord can all be the potential earthquake-resistant weak parts.The normal stress of the bottom chord of the arch rib under multidimensional excitation is mainly caused by the axial force,but the normal stress of the upper chord of the arch rib is caused by the axial force,in-plane and out of plane bending moment.Originality/value–The research provides specific suggestions for ground motion excitation mode and also provides reference information for the earthquake-resistant weak part and seismic design of long-span deck type railway steel truss arch bridges.
基金financially supported by“Demonstration Project of Innovation and Development of Marine Economy in Fuzhou in the13th Five-Year Plan(Grant No.FZHJ16)”“2019 Subsidy Fund Project for Marine Economy Development in Fujian Province(Grant No.FJHJF-L-2019-8)”Basic Scientific Research Operating Expenses of Central Public Welfare Research Institutes(Grant No.TKS170106)。
文摘The study of mooring forces is an important issue in marine engineering and offshore structures.Although being widely applied in mooring system,numerical simulations suffer from difficulties in their multivariate and nonlinear modeling.Data-driven model is employed in this paper to predict the mooring forces in different lines,which is a new attempt to study the mooring forces.The height and period of regular wave,length of berth,ship load,draft and rolling period are considered as potential influencing factors.Input variables are determined using mutual information(MI)and principal component analysis(PCA),and imported to an artificial neural network(NN)model for prediction.With study case of 200 and 300 thousand tons ships experimental data obtained in Dalian University of Technology,MI is found to be more appropriate to provide effective input variables than PCA.Although the three factors regarding ship characteristics are highly correlated,it is recommended to input all of them to the NN model.The accuracy of predicting aft spring line force attains as high as 91.2%.The present paper demonstrates the feasibility of MI-NN model in mapping the mooring forces and their influencing factors.
基金National Key Research and Development Program of China(2016YFA0201001)US National Science Foundation(CBET-1435968)+1 种基金National Natural Science Foundation of China(11627801,11472236 and 51472037)This material is based in part upon work supported by the State of Washington through the University of Washington Clean Energy Institute.
文摘Local domain structures of ferroelectrics have been studied extensively using various modes of scanning probes at the nanoscale,including piezoresponse force microscopy(PFM)and Kelvin probe force microscopy(KPFM),though none of these techniques measure the polarization directly,and the fast formation kinetics of domains and screening charges cannot be captured by these quasi-static measurements.In this study,we used charge gradient microscopy(CGM)to image ferroelectric domains of lithium niobate based on current measured during fast scanning,and applied principal component analysis(PCA)to enhance the signal-to-noise ratio of noisy raw data.We found that the CGM signal increases linearly with the scan speed while decreases with the temperature under power-law,consistent with proposed imaging mechanisms of scraping and refilling of surface charges within domains,and polarization change across domain wall.We then,based on CGM mappings,estimated the spontaneous polarization and the density of surface charges with order of magnitude agreement with literature data.The study demonstrates that PCA is a powerful method in imaging analysis of scanning probe microscopy(SPM),with which quantitative analysis of noisy raw data becomes possible.
