Differential equation of restrained torsion for rectangular-section box bar with honeycomb core was established and solved by using the method of undetermined function.Non-dimension normal stress, shear stress acting...Differential equation of restrained torsion for rectangular-section box bar with honeycomb core was established and solved by using the method of undetermined function.Non-dimension normal stress, shear stress acting in the faceplate and shear stress acting in the honeycomb-core and warping displacement were deduced. Numerical analysis shows the normal stress attenuates quickly along x-axis. Normal stress acting on the cross section at a distance of 20 h from the fixed end is only one per cent of that acting on the fixed end.展开更多
The impact buckling of a laminated composite bar is investigated in case of one of its ends moving due to axial impact compression. The governing equations considering the first- order shear deformation effect are der...The impact buckling of a laminated composite bar is investigated in case of one of its ends moving due to axial impact compression. The governing equations considering the first- order shear deformation effect are derived by the Hamilton principle and solved by the finite difference method. The critical axial shortness is determined by the B - R cirterion. The given example is used to highlight the influences of initial imperfection, impact velocity, stress wave and coupled stiffness. It is found that the unsymmetrically laminated bar has a quite different dynamic buckling behaviour from that of the symmetrically laminated bar.展开更多
Several experiments were performed with a Kolsky Bar(Split Hop- kinson Pressure Bar)device to investigate the dynamic axial buckling of cylindrical shells.The Kolsky Bar is a loading as well as a measuring device whic...Several experiments were performed with a Kolsky Bar(Split Hop- kinson Pressure Bar)device to investigate the dynamic axial buckling of cylindrical shells.The Kolsky Bar is a loading as well as a measuring device which can subject the shells to a fairly good square pulse.An attempt is made to understand the in- teraction between the stress wave and the dynamic buckling of cylindrical shells.It is suggested that the dynamic axial buckling of the shells,elastic or elasto-plastic,is mainly due to the compressive wave rather than the flexural or bending wave.The experimental results seem to support the two critical velocity theory for plastic buck- ling,with V_c1 corresponding to an axisymmetric buckling mode and V_c2 corresponding to a non-svmmetric buckling mode.展开更多
The dynamic buckling problem of elastic bars subjected to axial impact has been investigated by many authors in different ways.In this paper the problem,in which the elastic bars are assumed to be ideally straight,is ...The dynamic buckling problem of elastic bars subjected to axial impact has been investigated by many authors in different ways.In this paper the problem,in which the elastic bars are assumed to be ideally straight,is reformulated in connection with the bifurcation due to the stress wave propagation.The example of a semi-infinite elastic bar is used for illustration.展开更多
One of the potential solutions to steel-corrosion-related problems is the usage of fiber reinforced polymer （FRP） as a replacement of steel bars. In the past few decades, researchers have conducted a large number of...One of the potential solutions to steel-corrosion-related problems is the usage of fiber reinforced polymer （FRP） as a replacement of steel bars. In the past few decades, researchers have conducted a large number of experimental and theoretical studies on the behavior of small size glass fiber reinforce polymer （GFRP） bars （diameter smaller than 20 ram）. However, the behavior of large size GFRP bar is still not well understood. Particularly, few studies were conducted on the stress relaxation of grouted entirely large diameter GFRP soil nail. This paper investigates the effect of stress levels on the relaxation behavior of GFRP soil nail under sustained deformation ranging from 30% to 60% of its ultimate strain. In order to study the behavior of stress relaxation, two B-GFRP soil nail element specimens were developed and instrumented with fiber Bragg grating （FBG） strain sensors which were used to measure strains along the B-GFRP bars. The test results reveal that the behavior of stress relaxation of B-GFRP soil nail element subjected to pre-stress is significantly related to the elapsed time and the initial stress of relaxation procedure. The newly proposed model for evaluating stress relaxation ratio can substantially reflect the influences of the nature of B-GFRP bar and the property of grip body. The strain on the nail body can be redistributed automatically. Modulus reduction is not the single reason for the stress degradation.展开更多
A flexible technique of hot working of bars by axial feed rolling was introduced. The process deformation, strain field, stress field, and temperature fie M of the parts are analyzed by finite element method （ FEM）-...A flexible technique of hot working of bars by axial feed rolling was introduced. The process deformation, strain field, stress field, and temperature fie M of the parts are analyzed by finite element method （ FEM）-simulation software DEFORM-3D. The material flow rule and tool load have been investigated.展开更多
针对焊接锚垫板齿板锚固区配筋,提出了一种锚固区新型拉压杆模型。首先对齿板锚固区6种典型效应、主应力迹线以及力流平衡关系进行分析并建立新型拉压杆模型,其次通过美国国家公路与运输官员协会(American Association of State Highway...针对焊接锚垫板齿板锚固区配筋,提出了一种锚固区新型拉压杆模型。首先对齿板锚固区6种典型效应、主应力迹线以及力流平衡关系进行分析并建立新型拉压杆模型,其次通过美国国家公路与运输官员协会(American Association of State Highway and Transportation Officials,AASHTO)Load-and-resistance Factor Design Bridge Design Specifications、Building Code Requirements for Structural Concrete and Commentary(ACI 318-19)、《公路钢筋混凝土及预应力混凝土桥涵设计规范》(JTG 3362—2018)和欧洲设计建议Practical Design of Structural Concrete进行拉压杆模型参数定量化设计,根据拉压杆几何关系推导出焊接锚垫板齿板锚固区劈裂力计算式,利用有限元分析,拟合出焊接锚垫板下齿板锚固区劈裂力合力重心计算式。最后通过算例分析,按本文建议的拉压杆方法进行焊接锚垫板齿板锚固区结构配筋设计,能较好地控制锚下典型效应问题,相比《公路钢筋混凝土及预应力混凝土桥涵设计规范》(JTG 3362—2018)给出的设计方法,拉压杆模型法能较好地反映结构传力机制且具备可行性和可应用性,可为焊接锚垫板齿板锚固区配筋设计提供参考。展开更多
文摘Differential equation of restrained torsion for rectangular-section box bar with honeycomb core was established and solved by using the method of undetermined function.Non-dimension normal stress, shear stress acting in the faceplate and shear stress acting in the honeycomb-core and warping displacement were deduced. Numerical analysis shows the normal stress attenuates quickly along x-axis. Normal stress acting on the cross section at a distance of 20 h from the fixed end is only one per cent of that acting on the fixed end.
基金The present research work was financially supported by the National Natural Science Foundation of China.(No.19472042)
文摘The impact buckling of a laminated composite bar is investigated in case of one of its ends moving due to axial impact compression. The governing equations considering the first- order shear deformation effect are derived by the Hamilton principle and solved by the finite difference method. The critical axial shortness is determined by the B - R cirterion. The given example is used to highlight the influences of initial imperfection, impact velocity, stress wave and coupled stiffness. It is found that the unsymmetrically laminated bar has a quite different dynamic buckling behaviour from that of the symmetrically laminated bar.
基金The project supported by National Natural Science Foundation of China
文摘Several experiments were performed with a Kolsky Bar(Split Hop- kinson Pressure Bar)device to investigate the dynamic axial buckling of cylindrical shells.The Kolsky Bar is a loading as well as a measuring device which can subject the shells to a fairly good square pulse.An attempt is made to understand the in- teraction between the stress wave and the dynamic buckling of cylindrical shells.It is suggested that the dynamic axial buckling of the shells,elastic or elasto-plastic,is mainly due to the compressive wave rather than the flexural or bending wave.The experimental results seem to support the two critical velocity theory for plastic buck- ling,with V_c1 corresponding to an axisymmetric buckling mode and V_c2 corresponding to a non-svmmetric buckling mode.
文摘The dynamic buckling problem of elastic bars subjected to axial impact has been investigated by many authors in different ways.In this paper the problem,in which the elastic bars are assumed to be ideally straight,is reformulated in connection with the bifurcation due to the stress wave propagation.The example of a semi-infinite elastic bar is used for illustration.
基金financially supported by the Government of Guangdong Province and the Ministry of Education of China (Grant No. 2009B09060011)
文摘One of the potential solutions to steel-corrosion-related problems is the usage of fiber reinforced polymer （FRP） as a replacement of steel bars. In the past few decades, researchers have conducted a large number of experimental and theoretical studies on the behavior of small size glass fiber reinforce polymer （GFRP） bars （diameter smaller than 20 ram）. However, the behavior of large size GFRP bar is still not well understood. Particularly, few studies were conducted on the stress relaxation of grouted entirely large diameter GFRP soil nail. This paper investigates the effect of stress levels on the relaxation behavior of GFRP soil nail under sustained deformation ranging from 30% to 60% of its ultimate strain. In order to study the behavior of stress relaxation, two B-GFRP soil nail element specimens were developed and instrumented with fiber Bragg grating （FBG） strain sensors which were used to measure strains along the B-GFRP bars. The test results reveal that the behavior of stress relaxation of B-GFRP soil nail element subjected to pre-stress is significantly related to the elapsed time and the initial stress of relaxation procedure. The newly proposed model for evaluating stress relaxation ratio can substantially reflect the influences of the nature of B-GFRP bar and the property of grip body. The strain on the nail body can be redistributed automatically. Modulus reduction is not the single reason for the stress degradation.
基金the National Natural Science Foundation of China （Nos. 50205003 ,50675014）.
文摘A flexible technique of hot working of bars by axial feed rolling was introduced. The process deformation, strain field, stress field, and temperature fie M of the parts are analyzed by finite element method （ FEM）-simulation software DEFORM-3D. The material flow rule and tool load have been investigated.
文摘针对焊接锚垫板齿板锚固区配筋,提出了一种锚固区新型拉压杆模型。首先对齿板锚固区6种典型效应、主应力迹线以及力流平衡关系进行分析并建立新型拉压杆模型,其次通过美国国家公路与运输官员协会(American Association of State Highway and Transportation Officials,AASHTO)Load-and-resistance Factor Design Bridge Design Specifications、Building Code Requirements for Structural Concrete and Commentary(ACI 318-19)、《公路钢筋混凝土及预应力混凝土桥涵设计规范》(JTG 3362—2018)和欧洲设计建议Practical Design of Structural Concrete进行拉压杆模型参数定量化设计,根据拉压杆几何关系推导出焊接锚垫板齿板锚固区劈裂力计算式,利用有限元分析,拟合出焊接锚垫板下齿板锚固区劈裂力合力重心计算式。最后通过算例分析,按本文建议的拉压杆方法进行焊接锚垫板齿板锚固区结构配筋设计,能较好地控制锚下典型效应问题,相比《公路钢筋混凝土及预应力混凝土桥涵设计规范》(JTG 3362—2018)给出的设计方法,拉压杆模型法能较好地反映结构传力机制且具备可行性和可应用性,可为焊接锚垫板齿板锚固区配筋设计提供参考。
