• Structural Engineering and Mechanics
• /
• 제10권6호
• /
• pp.589-601
• /
• 2000

A simplified analysis procedure utilizing the strut-tie modeling technique is developed to take a close look into the post-elastic deformation capacity of beam-column connections in ductile reinforced concrete frame structures. Particular emphasis is given to the effect of concrete strength decay and quantity and arrangement of joint shear steel. For this a fan-shaped crack pattern is postulated through the joints. A series of hypothetical rigid nodes are assumed through which struts, ties and boundaries are connected to each other. The equilibrium consideration enables all forces in struts, ties and boundaries to be related through the nodes. The boundary condition surrounding the joints is obtained by the mechanism analysis of the frame structures. In order to avoid a complexity from the indeterminacy of the truss model, it is assumed that all shear steel yielded. It is noted from the previous research that the capacity of struts is limited by the principal tensile strain of the joint panel for which the strain of the transverse diagonal is taken. The post-yield deformation of joint steel is taken to be the only source of the joint shear deformation beyond the elastic range. Both deformations are related by the energy consideration. The analysis is then performed by iteration for a given shear strain. The analysis results indicate that concentrating most of the joint steel near the center of the joint along with higher strength concrete may enhance the post-elastic joint performance.

• Steel and Composite Structures
• /
• 제22권1호
• /
• pp.91-112
• /
• 2016

In this paper, post-buckling behavior of sandwich plates with functionally graded (FG) face sheets under uniform temperature rise loading is examined based on both sinusoidal shear deformation theory and stress function. It is supposed that the sandwich plate is in contact with an elastic foundation during deformation, which acts in both compression and tension. Thermo-elastic non-homogeneous properties of FG layers change smoothly by the variation of power law within the thickness, and temperature dependency of material constituents is considered in the formulation. In the present development, Von Karman nonlinearity and initial geometrical imperfection of sandwich plate are also taken into account. By employing Galerkin method, analytical solutions of thermal buckling and post-buckling equilibrium paths for simply supported plates are determined. Numerical examples presented in the present study discuss the effects of gradient index, sandwich plate geometry, geometrical imperfection, temperature dependency, and the elastic foundation parameters.

• Structural Engineering and Mechanics
• /
• 제57권4호
• /
• pp.617-639
• /
• 2016

In this work, an analytical formulation based on both hyperbolic shear deformation theory and stress function, is presented to study the nonlinear post-buckling response of symmetric functionally graded plates supported by elastic foundations and subjected to in-plane compressive, thermal and thermo-mechanical loads. Elastic properties of material are based on sigmoid power law and varying across the thickness of the plate (S-FGM). In the present formulation, Von Karman nonlinearity and initial geometrical imperfection of plate are also taken into account. By utilizing Galerkin procedure, closed-form expressions of buckling loads and post-buckling equilibrium paths for simply supported plates are obtained. The effects of different parameters such as material and geometrical characteristics, temperature, boundary conditions, foundation stiffness and imperfection on the mechanical and thermal buckling and post-buckling loading capacity of the S-FGM plates are investigated.

• Advances in nano research
• /
• 제7권6호
• /
• pp.405-417
• /
• 2019

This research is devoted to study post-buckling analysis of functionally graded carbon nanotubes reinforced composite (FG-CNTRC) micro plate with cut out subjected to magnetic field and resting on elastic medium. The basic formulation of plate is based on first order shear deformation theory (FSDT) and the material properties of FG-CNTRCs are presumed to be changed through the thickness direction, and are assumed based on rule of mixture; moreover, nonlocal Eringen's theory is applied to consider the size-dependent effect. It is considered that the system is embedded in elastic medium and subjected to longitudinal magnetic field. Energy approach, domain decomposition and Rayleigh-Ritz methods in conjunction with Newton-Raphson iterative technique are employed to trace the post-buckling paths of FG-CNTRC micro cut out plate. The influence of some important parameters such as small scale effect, cut out dimension, different types of FG distributions of CNTs, volume fraction of CNTs, aspect ratio of plate, magnitude of magnetic field, elastic medium and biaxial load on the post-buckling behavior of system are calculated. With respect to results, it is concluded that the aspect ratio and length of square cut out have negative effect on post-buckling response of micro composite plate. Furthermore, existence of CNTs in system causes improvement in the post-buckling behavior of plate and different distributions of CNTs in plate have diverse response. Meanwhile, nonlocal parameter and biaxial compression load on the plate has negative effect on post-buckling response. In addition, imposing magnetic field increases the post-buckling load of the microstructure.

• Structural Engineering and Mechanics
• /
• 제56권1호
• /
• pp.85-106
• /
• 2015

Postbuckling of thick plates made of functionally graded material (FGM) subjected to in-plane compressive, thermal and thermomechanical loads is investigated in this work. It is assumed that the plate is in contact with a Pasternak-type elastic foundation during deformation. Thermomechanical non-homogeneous properties are considered to be temperature independent, and graded smoothly by the distribution of power law across the thickness in the thickness in terms of the volume fractions of constituents. By employing the higher order shear deformation plate theory together the non-linear von-Karman strain-displacement relations, the equilibrium and compatibility equations of imperfect FGM plates are derived. The Galerkin technique is used to determine the buckling loads and postbuckling equilibrium paths for simply supported plates. Numerical examples are presented to show the influences of power law index, foundation stiffness and imperfection on the buckling and postbuckling loading capacity of the plates.

• Steel and Composite Structures
• /
• 제34권2호
• /
• pp.289-297
• /
• 2020

In the present research post-buckling of a cut out plate reinforced through carbon nanotubes (CNTs) resting on an elastic foundation is studied. Material characteristics of CNTs are hypothesized to be altered within thickness orientation which are calculated according to Mori-Tanaka model. For modeling the system mathematically, first order shear deformation theory (FSDT) is applied and using energy procedure, the governing equations can be derived. With respect to Rayleigh-Ritz procedure as well as Newton-Raphson iterative scheme, the motion equations are solved and therefore, post-buckling behavior of structure will be tracked. Diverse parameters as well as their reactions on post-buckling paths focusing cut out measurement, CNT's volume fraction and agglomeration, dimension of plate and an elastic foundation are investigated. It is revealed that presence of a square cut out can affect negatively post-buckling behavior of structure. Moreover, adding nanocompsits in the matrix leads to enhancement of post-buckling response of system.

• 소성∙가공
• /
• 제25권1호
• /
• pp.56-60
• /
• 2016

Precise prediction and control of the strip profile is crucial for automatic process set-up and operation of a hot strip mill. In the current study, we present the effect of post-deformation on the steady-state strip profile. The process was simulated by a 3-D elastic-plastic finite element (FE) analysis. Comparisons are made between the strip profile measured at the roll exit and the steady-state strip profile. The results raised an issue with regard to the importance of taking into account the effect of post-deformation.

• Advances in nano research
• /
• 제10권5호
• /
• pp.423-435
• /
• 2021

This paper examines the thermal post-buckling behaviors of graphene-reinforced metal matrix composite (GRMMC) laminated cylindrical panels which possess in-plane negative Poisson's ratio (NPR) and rest on an elastic foundation. A panel consists of GRMMC layers of piece-wise varying graphene volume fractions to obtain functionally graded (FG) patterns. Based on the MD simulation results, the GRMMCs exhibit in-plane NPR as well as temperature-dependent material properties. The governing equations for the thermal post-buckling of panels are based on the Reddy's third order shear deformation shell theory. The von Karman nonlinear strain-displacement relationship and the elastic foundation are also included. The nonlinear partial differential equations for GRMMC laminated cylindrical panels are solved by means of a singular perturbation technique in associate with a two-step perturbation approach and in the solution process the boundary layer effect is considered. The results of numerical investigations reveal that the thermal post-buckling strength for (0/90)_5T GRMMC laminated cylindrical panels can be enhanced with an FG-X pattern. The thermal post-buckling load-deflection curve of 6-layer (0/90/0)_S and (0/90)_3T panels of FG-X pattern are higher than those of 10-layer (0/90/0/90/0)_S and (0/90)_5T panels of FG-X pattern.

• Earthquakes and Structures
• /
• 제26권4호
• /
• pp.251-259
• /
• 2024

In this paper, the thermal post-buckling behavior of graphene platelets reinforced metal foams (GPLRMFs) plate with initial geometric imperfections on nonlinear elastic foundations are studied. First, the governing equation is derived based on the first-order shear deformation theory (FSDT) of plate. To obtain a single equation that only contains deflection, the Galerkin principle is employed to solve the governing equation. Subsequently, a comparative analysis was conducted with existing literature, thereby verifying the correctness and reliability of this paper. Finally, considering three GPLs distribution types (GPL-A, GPL-B, and GPL-C) of plates, the effects of initial geometric imperfections, foam distribution types, foam coefficients, GPLs weight fraction, temperature changes, and elastic foundation stiffness on the thermal post-buckling characteristics of the plates were investigated. The results show that the GPL-A distribution pattern exhibits the best buckling resistance. And with the foam coefficient (GPLs weight fraction, elastic foundation stiffness) increases, the deflection change of the plate under thermal load becomes smaller. On the contrary, when the initial geometric imperfection (temperature change) increases, the thermal buckling deflection increases. According to the current research situation, the results of this article can play an important role in the thermal stability analysis of GPLRMFs plates.

• Structural Engineering and Mechanics
• /
• 제6권6호
• /
• pp.693-710
• /
• 1998

This paper concerns studies on the shape formation of post-tensioned and shaped steel domes. The post-tensioned and shaped steel domes, assembled initially at ground level in an essentially flat condition, are shaped to a curved space form and erected into the final position by means of a post-tensioning technique. Based on previous studies on this shape formation principle, three post-tensioned and shaped steel domes have been constructed. The results of the shape formation tests and finite element analyses are reported in this paper. It is found that the first two test domes did not furnish a part-spherical shape as predicted by finite element analyses, because the movements of some mechanisms were not controlled sufficiently. With a revised post-tensioning method, the third dome obtained the theoretical prediction. The test results of the three post-tensioned and shaped domes have shown that a necessary condition to form a desired space shape from a planar layout with low joint stiffnesses is that the movements of all the existing mechanisms must be effectively controlled as indicated by the finite element analysis. The extent of the maximum elastic deformation of a post-tensioned and shaped steel structure is determined by the strength of the top chords and their joints. However, due to the semi-rigid characteristic of the top chord joints, the finite element analyses cannot give a close prediction for the maximum elastic deformations of the post-tensioned and shaped steel domes. The results of the current studies can be helpful for the design and construction of this type of structure.