In steel-concrete composite twin-girder decks, wide concrete slab would undergo significant shear lag warping effect, including positive and negative. Some researchers have investigated the positive shear lag of compo...In steel-concrete composite twin-girder decks, wide concrete slab would undergo significant shear lag warping effect, including positive and negative. Some researchers have investigated the positive shear lag of composite decks by means of one-dimensional line model, while the studies on the negative shear lag have not yet been reported until now. In this study, a new one-dimensional analytical model of composite twin-girder decks is first proposed based on the model proposed by Dezi et al. Besides slab shear lag effect and partial connection at slab-girder interface which have been included in the model of Dezi et al., the particularity of the proposed model relies on its ability to account for variation characteristic of cross-section. Verification of the analytical model is later conducted through comparison of results from the analytical analysis and elaborate FE analysis for a simply supported composite deck with increasing depth and a two-span continuous one with decreasing depth. Finally, three kinds of structural forms of composite twin-girder decks, including cantilever, simply supported and continuous decks, are selected to carry out the analysis of positive and negative shear lag behaviors by means of the analytical model. The influences of cross-sectional variation characteristic and load type on positive and negative shear lag behaviors are mainly investigated. Additionally, a new definition on effective width for considering simultaneously positive and negative shear lag behaviors is proposed. The results from the proposed analytical model and EC4 specification are compared to provide suggestions for designers and checkers. In this study, the proposed analytical model can provide a powerful numerical tool for researchers to conduct the further investigation, and the analysis on shear lag and effective width can assist in design analysis of composite twin-girder decks.展开更多
In this paper the geometric description and general theory of mechanical twinning are reviewed, the twins in general lattices and superlattices are summarized, and the kinetic process by which mechanical twins form is...In this paper the geometric description and general theory of mechanical twinning are reviewed, the twins in general lattices and superlattices are summarized, and the kinetic process by which mechanical twins form is revisited. A case study of mechanical twinning of HfV2+Nb, (cubic) Laves phase, is presented and the synchroshear of selected atomic layers is proposed to explain the physical process of twin formation. If the twins form in this way, then long shear vectors and / or atomicshuffles are not really necessary.展开更多
Employing ab initio calculations, we systematically investigated tile energy paths of [1012] twin-related lattice reorientation in hexagonal metals Be, Mg, Sc, Ti, Co, Y, Zr, Tc, Ru, Gd, Tb, Dy, Ho, Er, Tin, Lu, Hf, R...Employing ab initio calculations, we systematically investigated tile energy paths of [1012] twin-related lattice reorientation in hexagonal metals Be, Mg, Sc, Ti, Co, Y, Zr, Tc, Ru, Gd, Tb, Dy, Ho, Er, Tin, Lu, Hf, Re, and Os. Among the studied systems, lattice reorientation energy increases in the order of Mg, Gd, Tb, Dy, Zr, Tc, Ti, Ho, Y, Co, Er, Sc, Be, Tin, Lu, Hf, Re, Ru and Os. The reorientation process consists of shear and shuffle components. Concerning the significance of shuffle, these hexagonal metals fall into two groups. In the first group, which includes Mg, Co, Ru, Re and Os, regardless of the shear amount, subsequent shuffle is an energy-uphill process, while in the second group, which includes Ti, Tc, Be, Y. Gd, Tb, Dy, Ho, Zr, Er, Sc, Hf, Lu and Tin, shuffle becomes an energy-downhill process if shear component reaches an adequate level （at least 60%）. These results qualitatively explain the present observation of lattice reorientation in hexagonal metals, and shed light upon a general understanding on the [1012] twinning behavior in the aim of improving materials properties.展开更多
There are there great advances in the research on engineering strength theories in the latter half of the 20^th Century. The first advance was the devel-opment of strength theory from the single-shear strength theor...There are there great advances in the research on engineering strength theories in the latter half of the 20^th Century. The first advance was the devel-opment of strength theory from the single-shear strength theory including the Tresca yield criterion and Mohr-Coulomb failure criterion to theoctahe-dral-shear strength theory; the second one was that from the octahedral-shear strength theory to the twin-shear strength theory; and the third wasthe theories from the single criteria to the unifiedstrength theory. These three advances are summa-rized in this paper. It is interesting and useful for re-searchers to choose an appropriate failure criterion in studying the strength of materials and struc-tures, for engineers to correctly use it and for stu-dents to understand strength theory.展开更多
The damage which represents the alternation of internal slate of material was introduced to concrete strength theory according to the theory of mechanics of continuous medium and the failure criterion of deteriorated ...The damage which represents the alternation of internal slate of material was introduced to concrete strength theory according to the theory of mechanics of continuous medium and the failure criterion of deteriorated concrete was diseussions. In the tests, ultrasonic velocity is used to establish the damage variable and to establish the damage-eoupled failure criterion of concrete under freeze-thaw. The results show that the failure surface is gradually shrinking with the increase of freeze-thaw times. Furthermore, by the comparison between the theoretical data and the testing data from the literature, the rationality of strength theory proposed in the paper acquire confirmation. The damage-coupled failure criterion presented here can indicate the influence of damage evolution on the failure surface of concrete.展开更多
The mechanical properties of CFRP-confined rectangular concrete-filled stainless steel tube(CFSST)stub columns under axial compression were experimentally studied.A total of 28 specimens(7 groups)were fabricated for t...The mechanical properties of CFRP-confined rectangular concrete-filled stainless steel tube(CFSST)stub columns under axial compression were experimentally studied.A total of 28 specimens(7 groups)were fabricated for the axial compression test to study the influences of length-to-width ratio,CFRP constraint coefficient,and the thickness of stainless steel tube on the axial compression behavior.The specimen failure modes,the stress development of stainless steel tube and CFRP wrap,and the load-strain ratio curves in the loading process were obtained.Meanwhile,the relationship between axial and transverse deformations of each specimen was analyzed through the typical relative load-strain ratio curves.A bearing capacity prediction method was proposed based on the twin-shear strength theory,combining the limit equilibrium state of the CFRP-confined CFSST stub column under axial compression.The prediction method was calibrated by the test data in this study and other literature.The results show that the prediction method is of high accuracy.展开更多
基金supported by the Fundamental Research Fund for the Central Universities(Grant No.2015JBM069)the Research Fund for Talented Scholars of Beijing Jiaotong University(Grant No.2016RC026)
文摘In steel-concrete composite twin-girder decks, wide concrete slab would undergo significant shear lag warping effect, including positive and negative. Some researchers have investigated the positive shear lag of composite decks by means of one-dimensional line model, while the studies on the negative shear lag have not yet been reported until now. In this study, a new one-dimensional analytical model of composite twin-girder decks is first proposed based on the model proposed by Dezi et al. Besides slab shear lag effect and partial connection at slab-girder interface which have been included in the model of Dezi et al., the particularity of the proposed model relies on its ability to account for variation characteristic of cross-section. Verification of the analytical model is later conducted through comparison of results from the analytical analysis and elaborate FE analysis for a simply supported composite deck with increasing depth and a two-span continuous one with decreasing depth. Finally, three kinds of structural forms of composite twin-girder decks, including cantilever, simply supported and continuous decks, are selected to carry out the analysis of positive and negative shear lag behaviors by means of the analytical model. The influences of cross-sectional variation characteristic and load type on positive and negative shear lag behaviors are mainly investigated. Additionally, a new definition on effective width for considering simultaneously positive and negative shear lag behaviors is proposed. The results from the proposed analytical model and EC4 specification are compared to provide suggestions for designers and checkers. In this study, the proposed analytical model can provide a powerful numerical tool for researchers to conduct the further investigation, and the analysis on shear lag and effective width can assist in design analysis of composite twin-girder decks.
文摘In this paper the geometric description and general theory of mechanical twinning are reviewed, the twins in general lattices and superlattices are summarized, and the kinetic process by which mechanical twins form is revisited. A case study of mechanical twinning of HfV2+Nb, (cubic) Laves phase, is presented and the synchroshear of selected atomic layers is proposed to explain the physical process of twin formation. If the twins form in this way, then long shear vectors and / or atomicshuffles are not really necessary.
基金supported financially by the National Key Research and Development Program of China(No.2016YFB0701304)the National Natural Science Foundation of China(No.51671195)the Youth Innovation Promotion Association of Chinese Academy of Sciences(No.2015151)
文摘Employing ab initio calculations, we systematically investigated tile energy paths of [1012] twin-related lattice reorientation in hexagonal metals Be, Mg, Sc, Ti, Co, Y, Zr, Tc, Ru, Gd, Tb, Dy, Ho, Er, Tin, Lu, Hf, Re, and Os. Among the studied systems, lattice reorientation energy increases in the order of Mg, Gd, Tb, Dy, Zr, Tc, Ti, Ho, Y, Co, Er, Sc, Be, Tin, Lu, Hf, Re, Ru and Os. The reorientation process consists of shear and shuffle components. Concerning the significance of shuffle, these hexagonal metals fall into two groups. In the first group, which includes Mg, Co, Ru, Re and Os, regardless of the shear amount, subsequent shuffle is an energy-uphill process, while in the second group, which includes Ti, Tc, Be, Y. Gd, Tb, Dy, Ho, Zr, Er, Sc, Hf, Lu and Tin, shuffle becomes an energy-downhill process if shear component reaches an adequate level （at least 60%）. These results qualitatively explain the present observation of lattice reorientation in hexagonal metals, and shed light upon a general understanding on the [1012] twinning behavior in the aim of improving materials properties.
文摘There are there great advances in the research on engineering strength theories in the latter half of the 20^th Century. The first advance was the devel-opment of strength theory from the single-shear strength theory including the Tresca yield criterion and Mohr-Coulomb failure criterion to theoctahe-dral-shear strength theory; the second one was that from the octahedral-shear strength theory to the twin-shear strength theory; and the third wasthe theories from the single criteria to the unifiedstrength theory. These three advances are summa-rized in this paper. It is interesting and useful for re-searchers to choose an appropriate failure criterion in studying the strength of materials and struc-tures, for engineers to correctly use it and for stu-dents to understand strength theory.
基金Supported by the National Natural Science Foun-dation of China (50578068)
文摘The damage which represents the alternation of internal slate of material was introduced to concrete strength theory according to the theory of mechanics of continuous medium and the failure criterion of deteriorated concrete was diseussions. In the tests, ultrasonic velocity is used to establish the damage variable and to establish the damage-eoupled failure criterion of concrete under freeze-thaw. The results show that the failure surface is gradually shrinking with the increase of freeze-thaw times. Furthermore, by the comparison between the theoretical data and the testing data from the literature, the rationality of strength theory proposed in the paper acquire confirmation. The damage-coupled failure criterion presented here can indicate the influence of damage evolution on the failure surface of concrete.
基金This study was generously funded by the National Natural Science Foundation of China(Grant No.51268044).
文摘The mechanical properties of CFRP-confined rectangular concrete-filled stainless steel tube(CFSST)stub columns under axial compression were experimentally studied.A total of 28 specimens(7 groups)were fabricated for the axial compression test to study the influences of length-to-width ratio,CFRP constraint coefficient,and the thickness of stainless steel tube on the axial compression behavior.The specimen failure modes,the stress development of stainless steel tube and CFRP wrap,and the load-strain ratio curves in the loading process were obtained.Meanwhile,the relationship between axial and transverse deformations of each specimen was analyzed through the typical relative load-strain ratio curves.A bearing capacity prediction method was proposed based on the twin-shear strength theory,combining the limit equilibrium state of the CFRP-confined CFSST stub column under axial compression.The prediction method was calibrated by the test data in this study and other literature.The results show that the prediction method is of high accuracy.
