Abstract
The behavior of shear-wall dominant, low-rise, multistory reinforced concrete building structures is investigated. Because there are no beams or columns and the slab and wall thicknesses are approximately equal, available codes give little information relative to design for gravity and lateral loads. Items which effect the analysis of shear-wall dominant building structures, i.e., material nonlinearity including rotating crack capability, 3-D behavior, slab-wall interaction, floor flexibilities, stress concentrations around openings, the location and the amount of main discrete reinforcement are investigated. For this purpose 2 and 5 story building structures are modelled. To see the importance of 3-D modelling, the same structures are modelled by both 2-D and 3-D models. Loads are applied first the vertical then lateral loads which are static equivalent earthquake loads. The 3-D models of the structures are loaded in both in the longitudinal and transverse directions. A nonlinear isoparametric plate element with arbitrarily places edge nodes is adapted in order to consider the amount and location of the main reinforcement. Finally the importance of 3-D effects including the T-C coupling between walls are indicated.
Key Words
finite element; nonlinear analysis; reinforced concrete; shear-walls.
Address
Department of Civil Engineering, University of Illinois at Champaign-Urbana, IL 61801, U.S.A.
Abstract
Column is usually floating on the stone base directly with or without positioning tenon in traditional Chinese timber structure. Vertical load originated by the heavy upper structure would induce large friction force and compression force between interfaces of column foot and stone base. This study focused on the mechanical behaviors of column foot joint with consideration of the influence of vertical load. Mechanism of column rocking and stress state of column foot has been explored by theoretical analysis. A nonlinear finite element model of column foot joint has been built and verified using the full-scale test. The verified model is then used to investigate the mechanical behaviors of the joint subjected to cyclic loading with different static vertical loads. Column rocking mechanism and stress distributions of column foot were studied in detail, showing good agreement with the theoretical analysis. Mechanical behaviors of column foot joint and the effects of the vertical load on the seismic behavior of column foot were studied. Result showed that compression stress, restoring moment and stiffness increased with the increase of vertical load. An appropriate vertical load originated by the heavy upper structure would produce certain restoring moment and reset the rocking columns, ensuring the stability of the whole frame.
Key Words
traditional Chinese timber structure; column foot joint; vertical load; column rocking; mechanical behavior; finite element model
Address
Juan Wang:
1) School of Civil Engineering, Beijing Jiaotong University, Beijing 100044, China
2) Beijing\'s Key Laboratory of Structural Wind Engineering and Urban Wind Environment, Beijing Jiaotong University, Beijing 100044, China
Jun-Xiao He:
1) School of Civil Engineering, Beijing Jiaotong University, Beijing 100044, China
2) Beijing\'s Key Laboratory of Structural Wind Engineering and Urban Wind Environment, Beijing Jiaotong University, Beijing 100044, China
3) School of Computing, Engineering and Mathematics, Western Sydney University, Parramatta, NSW 2150, Australia
Qing-Shan Yang:
1) Beijing\'s Key Laboratory of Structural Wind Engineering and Urban Wind Environment, Beijing Jiaotong University, Beijing 100044, China
2) School of Civil Engineering, Chongqing University, Chongqing 400044, China
Na Yang:
1) School of Civil Engineering, Beijing Jiaotong University, Beijing 100044, China
2) Beijing\'s Key Laboratory of Structural Wind Engineering and Urban Wind Environment, Beijing Jiaotong University, Beijing 100044, China
Abstract
A practical multi-spring model is proposed for a nonlinear analysis of reinforced concrete members, especially columns, taking into account the interaction of axial load and bi-directional bending moment. The parameters of the model are determined on the basis of material properties and section geometry. The axial force-moment interaction curve of reinforced concrete sections predicted by the model was shown to agree well with those obtained by the flexural analysis utilizing realistic stress-strain relations of materials. The reliability of the model was also examined with respect to the test of reinforced concrete columns subjected to varying axial load and bi-directional lateral load reversals. The analytical results agreed well with the experiment.
Address
Department of Civil Engineering, National University of Singapore, Singapore 0511, Singapore Department of Architecture, The University of Tokyo, Tokyo 113, Japan
Abstract
The motivations of the application of shakedown analysis to the earthquake-resistant design of ductile moment-resisting steel structures are presented. The problems which must be solved with this application are also addressed. The illustrative results from a series of static and time history nonlinear analyses of one-bay three-story steel frame and the related discussions have shown that the incremental collapse may be the critical design criterion in case of earthquake loading. Based on the findings, it was concluded that the inelastic excursion mechanism for alternation load pattern, such as in earthquake, should be the sidesway mechanism of the whole structure for the efficient mobilization of the structural energy dissipating capacity and that the shakedown analysis technique can be used as a tool to ensure this mechanism.
Key Words
shakedown analysis; earthquake-resistant design; incremental collapse; alternating plasticity; instantaneous plastic collapse; plastic deformation; plastic hinge; energy dissipation.
Address
Department of Architecture, Yeungnam University, Kyongsan 712-749, Korea Department of Civil Engineering, University of California, Berkeley, CA 94720, U.S.A.
Abstract
The eigen-equation of a wave traveling over repetitive structure is derived directly form the stiffness matrix formulation, in a form which can be used for the case of the cross stiffness submatrix Kab being singular. The weighted adjoint symplectic orthonormality relation is proved first. Then the general method of solution is derived, which can be used either to find all the eigensolutions, or to find the main eigensolutions for large scale problems.
Key Words
repetitive structure; eigenvalue problem; symplectic matrix; wave propagation.
Address
Research Institute of Engineering Mechanics, Dalian Univ. of Tech., P.R.C Division of Structural Engineering, School of Engineering, Univ. of Wales College of Cardiff, U.K.
Abstract
A new three-dimensional transition solid element was presented for the automated three-dimensional adaptive h-refinement or the local mesh refinement where the steep stress gradient exists. The proposed transition element was established by adding variable nodes (element nodes) to basic 8-node for an effective connection between the refined region and the coarse region with minimum degrees of freedom possible. To be consistent in accuracy with 8-node solid element with nonconforming modes, this transition element was also improved through the addition of the modified nonconforming modes. Numerical examples show that the performance of element and the applicability to 3D adaptations are satisfactory.
Abstract
The punching shear strength of concrete flat plates is one of the topics of intensive research in recent years by various concrete structures researchers. This paper reviews four current methods of analysing the punching shear strength at the corner-and edge-column positions of reinforced concrete flat plates. They include those recommended in the Australian Standard AS3600-1988, the American Concrete Institute ACI318-89 and the British Standard on Concrete Practices (BS8110) as well as the approach developed at the University of Wollongong, Australia. Based on half-scale model test results, a comparative study of these four analysis methods is made with regard to their limitation, accuracy and reliability. It is found that the Wollongong approach in general gives the best performance in predicting the punching shear strength of flat plates with torsion strips and those with spandrel beams. The Australian Standard procedure performs just as satisfactorily for flat plates with torsion strips but tends to be unsafe for those with spandrel beams. Both the ACI and the British methods are applicable only to flat plates with torsion strips; they also tend to give unsafe predictions for the punching shear strength.
Key Words
columns (supports); connections (mechanisms to transfer stress); failure; concrete flat plates; models; punching shear; reinforced concrete; shear strength; spandrel beams; strength analysis; torsion strips.
Address
Structural Engineering and Construction Group, University of Wollongong, Australia Department of Civil and Mining Engineering, University of Wollongong, Australia
Abstract
A C° continuous finite element formulation of a higher order displacement theory is presented or predicting linear and geometrically non-linear in the sense of von Karman transient responses of composite and sandwich plages. The displacement model accounts for non-linear cubic variation of tangential displacement components through the thickness of the laminate and the theory requires no shear correction foefficients. In the time domain, the explicit central difference integrator is used in conjunction with the special mass matrix diagonalization shceme with conserves the total mass of the element and includes effects due to rotary inertia terms. The parametric effects of the time step, finite element mesh, lamination scheme and orthotropy on the linear and geometrically non-linear responses are investigated. Numerical results for central transverse deflection, stresses and stress resultants are presented for square/rectangular composite and sandwich plages under various boundary conditions and loadings and these are compared with the results from other sources. Some new results are also tabulated for future reference.
Key Words
plates; elastic plates; composite plates; sandwich plates; shear-deformable theory; refined theory; higher-order theory; finite element analysis; large deflection analysis; geometrically non-linear analysis; transient dynamics; dynamics.
Address
Department of Civil Engineering, Indian Institute of Technology, Powai, Bombay-400 076, India
Abstract
The near field is discretized into finite elements, and the far field into infinite elements. Closed form far-field solutions to three fundamental problems are used as the shape functions of the infinite elements. Such infinite elements are capable of transmitting all surface and body waves. An efficient scheme to integrate numerically the stiffness and mass matrices of these elements in presented. Results agree closely with those obtained by others.
Key Words
attenuations; body waves; elasticity; finite elements; half space; impedance; infinite elements; outgoing waves; near field; P-waves; radiation; shape functions; S-waves; surface wave; vibration; viscoelasticity; wavenumbers.
Address
School of Civil Engineering, Asian Institute of Technology, Bangkok 10501, Thailand
Abstract
The paper presents a generalized optimal active control algorithm for earthquake-resistant structures. The study included the weighting matrix configuration, stability, and time-delays for achieving control effectiveness and optimum solution. The sensitivity of various time-delays in the optimal solution is investigated for which the stability regions are determined. A simplified method for reducing the influence of time-delay on dynamic response is proposed. Numerical examples illustrate that the proposed optimal control algorithm is advantageous over others currently in vogue. Its feedback control law is independent of the time increment, and its weighting matrix can be flexibly selected and adjusted at any time during the operation of the control system. The examples also show that the weighting matrix based on pole placement approach is superior to other weighting matrix configurations for its self-adjustable control effectiveness. Using the time-delay correction method can significantly reduce the influence of time-delays on both structural response and required control force.
Key Words
active control; dynamic structures; earthquakes; optimal control algorithm; pole placement technique; stability analysis; time-delay.
Address
Intelligent system Center Civil Engineering Department, University of Missouri-Rolla, MO 65401, U.S.A.
