Transverse opening in a beam has a reducing effect of the beam stiffness which will cause a significant increase in beam deflection in the region on the opening. In this paper, a new stiffness matrix for a beam elemen...Transverse opening in a beam has a reducing effect of the beam stiffness which will cause a significant increase in beam deflection in the region on the opening. In this paper, a new stiffness matrix for a beam element with transverse opening including the effect of shear deformation has been derived. The strain energy principle is used in the derivation process of the stiffness matrix and the fixed-end force vector for the case of a concentrated or a uniformly distributed load is also derived. The accuracy of the obtained results based on the derived stiffness matrix is examined through comparison with that of the finite element method using Abaqus package and a previous study which show a good agreement with high accuracy.展开更多
Critical crack tip opening displacement (CTODc) of concrete using experimental and analytical evaluation with seven different compressive strengths ranging from 30 up to 150 MPa was studied based on two types of fract...Critical crack tip opening displacement (CTODc) of concrete using experimental and analytical evaluation with seven different compressive strengths ranging from 30 up to 150 MPa was studied based on two types of fracture tests:three-point bending (TPB) and wedge splitting (WS).In the tests,the values of CTODc were experimentally recorded using a novel technique,in which fiber Bragg grating (FBG) sensors were used,and two traditional techniques,in which strain gauges and clip gauges were deployed.The values of CTODc of tested concrete were also predicted using two existing analytical formulae proposed by JENQ & SHAH and XU,respectively.It is found that the values of CTODc obtained by both experimental measurements and analytical formulae exhibit a negligible variation as the compressive strength of concrete increases,and the test geometry adopted has little impact on the value of CTODc.Regarding the experimental measurement of CTODc,the clip gauge method generally leads to a larger value of CTODc and shows a more significant scatter as compared with the other two methods,while the strain gauge method leads to a slightly lower CTODc as compared with the FBG sensor method.The analytical formula proposed by JENQ and SHAH is found to generally lead to an overestimation,while the analytical formula proposed by XU shows a good accuracy.展开更多
This paper comprehensively reviews China＇s openness since 1978 from three aspects： trade, foreign investment and global production sharing. We point out that the economic development of China is now standing at a hi...This paper comprehensively reviews China＇s openness since 1978 from three aspects： trade, foreign investment and global production sharing. We point out that the economic development of China is now standing at a historic turning point. Specifically, economic changes in China are discassed from four dimensions： （i） from China being a world assembly line to a world manufacturing powerhouse; （ii） from China being a world capital receiver to a world investor; （iii） from China being a world factory to a world market; and （iv） from the situation of ＂made in China＂ to ＂innovated in China.＂ At the same time, the global economic system has also reached a turning point. A ＂North America-Europe-Asia ＂ tri-polar system has formed, in which the USA, Germany and China, respectively, serve as the regional core economies.展开更多
文摘Transverse opening in a beam has a reducing effect of the beam stiffness which will cause a significant increase in beam deflection in the region on the opening. In this paper, a new stiffness matrix for a beam element with transverse opening including the effect of shear deformation has been derived. The strain energy principle is used in the derivation process of the stiffness matrix and the fixed-end force vector for the case of a concentrated or a uniformly distributed load is also derived. The accuracy of the obtained results based on the derived stiffness matrix is examined through comparison with that of the finite element method using Abaqus package and a previous study which show a good agreement with high accuracy.
基金Project(50438010) supported by the Key Program of the National Natural Science Foundation of ChinaProject(JGZXJJ2006-13) supported by the Research and Application Programs of Key Technologies for Major Constructions in the South-North Water Transfer Project Construction in China
文摘Critical crack tip opening displacement (CTODc) of concrete using experimental and analytical evaluation with seven different compressive strengths ranging from 30 up to 150 MPa was studied based on two types of fracture tests:three-point bending (TPB) and wedge splitting (WS).In the tests,the values of CTODc were experimentally recorded using a novel technique,in which fiber Bragg grating (FBG) sensors were used,and two traditional techniques,in which strain gauges and clip gauges were deployed.The values of CTODc of tested concrete were also predicted using two existing analytical formulae proposed by JENQ & SHAH and XU,respectively.It is found that the values of CTODc obtained by both experimental measurements and analytical formulae exhibit a negligible variation as the compressive strength of concrete increases,and the test geometry adopted has little impact on the value of CTODc.Regarding the experimental measurement of CTODc,the clip gauge method generally leads to a larger value of CTODc and shows a more significant scatter as compared with the other two methods,while the strain gauge method leads to a slightly lower CTODc as compared with the FBG sensor method.The analytical formula proposed by JENQ and SHAH is found to generally lead to an overestimation,while the analytical formula proposed by XU shows a good accuracy.
基金We thank Yacheng Yang and Chunrui Liu from Tsinghua University for providing very helpful research assistance. This work was supported by the National Natural Science Foundation of China （No. 71503047）, the Beijing Social Science Foundation （No. 15JGC 162）, and the Fundamental Research Funds for the Central Universities of the University of International Business and Economics （No. 16YQ02）. 1In this paper, ＂China＂ refers to ＂Chinese mainland.＂
文摘This paper comprehensively reviews China＇s openness since 1978 from three aspects： trade, foreign investment and global production sharing. We point out that the economic development of China is now standing at a historic turning point. Specifically, economic changes in China are discassed from four dimensions： （i） from China being a world assembly line to a world manufacturing powerhouse; （ii） from China being a world capital receiver to a world investor; （iii） from China being a world factory to a world market; and （iv） from the situation of ＂made in China＂ to ＂innovated in China.＂ At the same time, the global economic system has also reached a turning point. A ＂North America-Europe-Asia ＂ tri-polar system has formed, in which the USA, Germany and China, respectively, serve as the regional core economies.
