Abstract
In this paper spacing and width of flexural cracks in reinforced concrete beams are determined using two-dimensional finite element analysis. At early loading stages on the beam the primary crack spacing is based on the slip length, which is the development length required to resist the steel stress increment that occurs at a cracked section on the formation of the first flexural crack. A semi-empirical formula is presented in this paper for the determination of the slip length for a given beam. At higher load levels, the crack spacing is based on critical crack spacing, which is defined as the particular crack spacing that would produce a concrete tensile stress equal to the flexural strength of concrete. The resulting crack width is calculated as the relative difference in extensions of steel reinforcement and adjacent concrete evaluated at the cracked section. Finally a comparative study is undertaken, which indicates that the spacing and width of cracks calculated by this method agree well with values measured by other investigators.
Key Words
analytical method; crack spacing; crack width; finite element analysis; reinforced concrete.
Address
School of Engineering, Griffith University-Gold Coast Campus, Australia
Abstract
Six large scale models of conventionally reinforced concrete coupling beams with span/depth ratios ranging from 1.17 to 2.00 were tested under monotonically applied shear loads to study their nonlinear behavior using a newly developed test method that maintained equal rotations at the two ends of the coupling beam specimen and allowed for local deformations at the beam-wall joints. By conducting the tests under displacement control, the post-peak behavior and complete load-deflection curves of the coupling beams were obtained for investigation. It was found that after the appearance of flexural and shear cracks, a deep coupling beam would gradually transform itself from an ordinary beam to a truss composed of diagonal concrete struts and longitudinal and transverse steel reinforcement bars. Moreover, in a deep coupling beam, the local deformations at the beam-wall joints could contribute significantly (up to the order of 50%) to the total deflection of the coupling beam, especially at the post-peak stage. Finally, although a coupling beam failing in shear would have a relatively low ductility ratio of only 5 or even lower, a coupling beam failing in flexure could have a relatively high ductility ratio of 10 or higher.
Key Words
reinforced concrete; coupling beams; shear walls.
Address
Department of Civil Engineering, Tsinghua University, Beijing, China Department of Civil Engineering, The University of Hong Kong, Hong Kong SAR, China
Abstract
The formulation of a non-linear shear deformable shell element is presented for the solution of stability problems of stiffened plates and shells. The formulation of the geometrical stiffness presented here is exactly defined on the midsurface and is efficient for analyzing stability problems of thick plates and shells by incorporating bending moment and transverse shear resultant force. As a result of the explicit integration of the tangent stiffness matrix, this formulation is computationally very efficient in incremental nonlinear analysis. The element is free of both membrane and shear locking behaviour by using the assumed strain method such that the element performs very well in the thin shells. By using six degrees of freedom per node, the present element can model stiffened plate and shell structures. The formulation includes large displacement effects and elasto-plastic material behaviour. The material is assumed to be isotropic and elasto-plastic obeying Von Mises
Key Words
assumed strain; co-rotational methods; analytical integration; large displacement elasto-plastic; stiffened plates and shells.
Address
School of Civil Engineering, Asian Institute of Technology, P.O. Box 4, Klongluang,Pathumthani, 12120, Thailand
Address
Department of Civil Engineering, Royal Military College of Canada, Kingston, Ontario, Canada K7K 5L0 Director Maritime Ship Support, Department of National Defence,Ottawa, Ontario, Canada K1A 0K2 Department of Civil & Environmental Engineering, Carleton University, 1125 Colonel By Drive, Ottawa Ontario, Canada K1S 5B6
Abstract
The dynamic response analysis of closed loop control system based on probability for the intelligent truss structures with random parameters is presented. The expressions of numerical characteristics of structural dynamic response of closed loop control system are derived by means of the mode superposition method, in which the randomness of physical parameters of structural materials, geometric dimensions of active bars and passive bars, applied loads and control forces are considered simultaneously. The influences of the randomness of them on structural dynamic response are inspected by several engineering examples and some significant conclusions are obtained.
Key Words
piezoelectric intelligent truss structures; closed loop control; random forces; random parameters; dynamic response analysis.
Address
School of Electronic Mechanical Engineering, Xidian University, Xi
Abstract
In this study, circular plates subjected to general type of loads and supported on a two-parameter elastic foundation are analysed. The stiffness, elastic bedding and soil shear effect matrices of a fully compatible ring sector plate element, developed by Saygun (1974), are obtained numerically assuming variable thickness of the element. Ring sector soil finite element is also defined to determine the deflection of the soil surface outside the domain of the plate in order to establish the interaction between the plate and the soil. According to Vallabhan and Das (1991) the elastic bedding (C ) and shear parameters (CT) of the foundation are expressed depending on the elastic constants (Es , ns) and the thickness of compressible soil layer (Hs) and they are calculated with a suitable iterative procedure. Using ring sector elements presented in this paper, permits the generalization of the loading and the boundary conditions of the soil outside the plate.
Key Words
ring sector compatible plate finite element; the coefficient of subgrade reactions; shear parameter coefficient; mode shape parameter.
Address
Faculty of Civil Engineering, Istanbul Technical University, Maslak 80626 Istanbul, Turkey
