The lateral torsional buckling phenomenon often governs design of steel I-beams. Although web opening is often used to accommodate the required mechanical and piping works in buildings, its effect on the buckling inst...The lateral torsional buckling phenomenon often governs design of steel I-beams. Although web opening is often used to accommodate the required mechanical and piping works in buildings, its effect on the buckling instability is not considered in the design codes. In this paper, the effect of web opening on both lateral torsional buckling and local buckling behaviors has been investigated. A simply supported steel I-beam has been studied under uniform bending moment around the major axis. Buckling analysis has been performed using the finite element method. Linear regression analysis has been conducted for output data to formulate an equation for the critical moment including web opening effect. The results have shown a limited reduction in the lateral torsional buckling capacity and a significant reduction in the local buckling capacity.展开更多
This paper focuses on the seismic response of the curved and post-tensioned concrete box girder bridges. More specifically, it investigates how the curvature influences the response of a bridge subjected to earthquake...This paper focuses on the seismic response of the curved and post-tensioned concrete box girder bridges. More specifically, it investigates how the curvature influences the response of a bridge subjected to earthquake. Parametric analysis of different radius of curvature is performed and the internal forces, torsion moment, axial and shear along the bridge are calculated. Two types of connections are investigated, the monolithic connection and deck connection with bents and abutments with rubber bearing. The response spectrum seismic analysis was performed. The models were designed, according to the provisions of EC8-part 2, EC2 and the Greek regulations E39/99. Diagrams relating the curvature with the torsion moment have been obtained from the results of parametric analysis. These diagrams could be used by engineers for preliminary design of such kind of bridges.展开更多
Designing artificial structures with heterogeneous elements and manipulating their interface coupling ways usually bring in synthetic neo-nature to functional devices.For piezoceramic devices,the deformation response ...Designing artificial structures with heterogeneous elements and manipulating their interface coupling ways usually bring in synthetic neo-nature to functional devices.For piezoceramic devices,the deformation response refers to a variety of extensional,contractional,or shear modes of crystals,and also relies on boundary conditions from morphology design.However,to pursue fundamental torsion actuation in an integrated piezoceramic component is still a long-term tough task due to nil twist mode limited by microscopic crystal mirror symmetry.Herein,we demonstrate a design of cofired monolithic actuators to originally overcome this obstacle.The prototype device is composed of two sets of stacked actuation subunits that work on artificially reverse face shear modes,and their chiral stiffness couplings will synergistically contribute to synthetic twist outputs at a broad bandwidth.Finite element simulation reveals twist displacements are highly tunable by manipulating the geometrical dimensions.Transverse deflection measurements manifest the stable and sizeable linear actuation response to applied electric fields(around 3.7μm under 40 V at 1 Hz).Importantly,the design actually introduces a more general route to enable arbitrary modes and actuation states in integrated piezoceramic components.展开更多
文摘The lateral torsional buckling phenomenon often governs design of steel I-beams. Although web opening is often used to accommodate the required mechanical and piping works in buildings, its effect on the buckling instability is not considered in the design codes. In this paper, the effect of web opening on both lateral torsional buckling and local buckling behaviors has been investigated. A simply supported steel I-beam has been studied under uniform bending moment around the major axis. Buckling analysis has been performed using the finite element method. Linear regression analysis has been conducted for output data to formulate an equation for the critical moment including web opening effect. The results have shown a limited reduction in the lateral torsional buckling capacity and a significant reduction in the local buckling capacity.
文摘This paper focuses on the seismic response of the curved and post-tensioned concrete box girder bridges. More specifically, it investigates how the curvature influences the response of a bridge subjected to earthquake. Parametric analysis of different radius of curvature is performed and the internal forces, torsion moment, axial and shear along the bridge are calculated. Two types of connections are investigated, the monolithic connection and deck connection with bents and abutments with rubber bearing. The response spectrum seismic analysis was performed. The models were designed, according to the provisions of EC8-part 2, EC2 and the Greek regulations E39/99. Diagrams relating the curvature with the torsion moment have been obtained from the results of parametric analysis. These diagrams could be used by engineers for preliminary design of such kind of bridges.
基金the National Natural Science Foundation of China(51772005,51132001,and 52032012)Beijing Key Laboratory for Magnetoelectric Materials and Devices。
文摘Designing artificial structures with heterogeneous elements and manipulating their interface coupling ways usually bring in synthetic neo-nature to functional devices.For piezoceramic devices,the deformation response refers to a variety of extensional,contractional,or shear modes of crystals,and also relies on boundary conditions from morphology design.However,to pursue fundamental torsion actuation in an integrated piezoceramic component is still a long-term tough task due to nil twist mode limited by microscopic crystal mirror symmetry.Herein,we demonstrate a design of cofired monolithic actuators to originally overcome this obstacle.The prototype device is composed of two sets of stacked actuation subunits that work on artificially reverse face shear modes,and their chiral stiffness couplings will synergistically contribute to synthetic twist outputs at a broad bandwidth.Finite element simulation reveals twist displacements are highly tunable by manipulating the geometrical dimensions.Transverse deflection measurements manifest the stable and sizeable linear actuation response to applied electric fields(around 3.7μm under 40 V at 1 Hz).Importantly,the design actually introduces a more general route to enable arbitrary modes and actuation states in integrated piezoceramic components.
