Abstract
A reliable and accurate method has been developed to predict the flexural deformation response of structural concrete members subject to service load. The method that has been developed relates the extent of concrete cracking, measured as a function of the magnitude of applied moment in a member, to the reduction in the effective moment of inertia of cracked reinforced concrete members under service load conditions. The ratio of the area of the moment diagram where the moment exceeds the cracking moment, to the total area of the moment diagram for any loading, provides the basis for the calculation of the effective moment of inertia. This ratio also represents mathematically a probability of crack occurrence. Verification of this method for the determination of the effective moment of inertia has been achieved from an experimental test program, and has included beam tests with different loading configurations, and shear wall tests subjected to a range of vertical and lateral load levels. Further verification of this method has been made with reference to the experimental investigation of other recently published work.
Key Words
probability; flexural members; deflection; curvature; stiffness; serviceability prediction; moment of inertia; cracking; reinforced concrete.
Address
Feng Ning, Neil C. Mickleborough and Chun-Man Chan, Department of Civil Engineering, Hong Kong University of Science & Technology, Kowloon, Hong Kong
Abstract
The frictionless contact problem for a layered composite which consists of two elastic layers having different elastic constants and heights resting on two simple supports is considered. The external load is applied to the layered composite through a rigid stamp. For values of the resultant compressive force P acting on the stamp vertically which are less than a critical value Pcr and for small flexibility of the layered composite, the continuous contact along the layer - the layer and the stamp - the layered composite is maintained. However, if the flexibility of the layered composite increases and if tensile tractions are not allowed on the interface, for P > Pcr, a separation may be occurred between the stamp and the layered composite or two elastic layers interface along a certain finite region. The problem is formulated and solved for both cases by using Theory of Elasticity and Integral Transform Technique. Numerical results for Pcr, separation initiation distance, contact stresses, distances determining the separation area, and the vertical displacement in the separation zone between two elastic layers are given.
Key Words
continuous contact; discontinuous contact; separation; integral equation; elastic layer; rigid stamp; theory of elasticity; fourier transform.
Address
Ahmet Birinci and RagIp Erdol, Civil Engineering Department, Karadeniz Technical University, 61080, Trabzon, Turkey
Abstract
A numerical methodology is presented in this paper for the geometrically non-linear analysis of slender uni-dimensional structural elements under unilateral contact constraints. The finite element method together with an updated Lagrangian formulation is used to study the structural system. The unilateral constraints are imposed by tensionless supports or foundations. At each load step, in order to obtain the contact regions, the equilibrium equations are linearized and the contact problem is treated directly as a minimisation problem with inequality constraints, resulting in a linear complementarity problem (LCP). After the resulting LCP is solved by Lemke
Key Words
unilateral constraints; incremental-iterative strategies; geometric non-linearity; updated Lagrangian formulation; linear complementary problem.
Address
Ricardo Azoubel da Mota Silveira, Civil Engineering Department, Federal University of Ouro Preto (UFOP) Morro do Cruzeiro-Campus Universitario, 35400-000 Ouro Preto, MG, Brazil Paulo Batista Goncalves, Civil Engineering Department, Catholic University, PUC-Rio Rua Marques de Sao Vicente, 225 - Gavea, 22453-900 Rio de Janeiro, RJ, Brazil
Abstract
Whereas the potential of static inelastic analysis methods is recognised in earthquake design and assessment, especially in contrast with elastic analysis under scaled forces, they have inherent shortcomings. In this paper, critical issues in the application of inelastic static (pushover) analysis are discussed and their effect on the obtained results appraised. Areas of possible developments that would render the method more applicable to the prediction of dynamic response are explored. New developments towards a fully adaptive pushover method accounting for spread of inelasticity, geometric nonlinearity, full multi-modal, spectral amplification and period elongation, within a framework of fibre modelling of materials, are discussed and preliminary results are given. These developments lead to static analysis results that are closer than ever to inelastic time-history analysis. It is concluded that there is great scope for improvements of this simple and powerful technique that would increase confidence in its employment as the primary tool for seismic analysis in practice.
Key Words
seismic analysis; pushover; inelastic response.
Address
A.S. Elnashai, Engineering Seismology and Earthquake Engineering Section Civil and Environmental Engineering Department, Imperial College, London SW7 2BU, UK
Abstract
The objective of this paper is to develop a simplified method that could predict the strength of concrete filled steel tube (CFT) columns applicable to high strength material under combined axial compression and flexure. The simplified method for determining the strength of CFT columns is based on the interaction curve of the section approached by a polygonal connection of the points. These points are determined by using symmetrical properties of the CFT section. For each point, a simple equation is proposed to determine the strength of the slender columns under compression and flexure. The simple equation was adjusted with results of elasto-plastic analysis results. Validation of the simplified method is undertaken by comparison with data from the test conducted at Kyushu University. These results confirm the fact that the simplified method could accurately and reliably predict the strength of CFT columns under combined axial compression and flexure.
Key Words
concrete filled steel tubular columns; simplified design formula; high strength material.
Address
Jinan Chung, Department of Architecture, Fukuoka University, 8-19-1 Nanakuma Jonanku, Fukuoka, Japan Chiaki Matsui
Abstract
In this paper, an analytical procedure for solving several static and dynamic problems of non-uniform beams is proposed. It is shown that the governing differential equations for several stability, free vibration and static problems of non-uniform beams can be written in the from of a unified self-conjugate differential equation of the second-order. There are two functions in the unified equation, unlike most previous researches dealing with this problem, one of the functions is selected as an arbitrary expression in this paper, while the other one is expressed as a functional relation with the arbitrary function. Using appropriate functional transformation, the self-conjugate equation is reduced to Bessel
Key Words
non-uniform beam; stability; vibration; dynamic.
Address
Q.S. Li, Department of Building and Construction, City University of Hong Kong Tat Chee Avenue, Kowloon, Hong Kong
Abstract
The reliable prediction of elastic vibrations of wetted complex structures, as ships, tanks, offshore structures, propulsion components etc. represent a theoretical and numerical demanding task due to fluid-structure interaction. The paper presented is addressed to the vibration analysis by a combined FE-BE-procedure based on the added mass concept utilizing a direct boundary integral formulation of the potential fluid problem in interior and exterior domains. The discretization is realized by boundary element collocation method using conventional as well as infinite boundary element formulation with analytical integration scheme. Particular attention is devoted to modelling of interior problems with both several separate or communicating fluid domains as well as thin-walled structures wetted on both sides. To deal with this specific kind of interaction problems so-called
Key Words
fluid structure interaction; vibration analysis; coupled finite and boundary element method;
Address
Udo Rohr and Peter Moller, Department of Mechanical Engineering, University of Rostock, Albert-Einstein-Str. 2, 18059 Rostock, Germany
