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CONTENTS
Volume 6, Number 8, December 1998
 

Abstract
During the 1995 Hyogoken-Nanbu Earthquake, a reinforced concrete building, called Jeunesse Rokko, suffered intermediate damage by forming a beam-yielding tweak-beam strong-column) mechanism, which has been regarded as the most desirable earthquake resisting mechanism throughout the world. High cost to repair damage at many beam ends and poor appearance expected after the repair work made the owner decide to tear down the building. Nonlinear earthquake response analyses were conducted to simulate the behavior of the building during the earthquake. The influence of nonstructural members was considered in the analysis. The calculated results were compared with the observed damage, especially the location of yield hinges and compression failure of spandrel beams, and the degree of cracking in columns and in column-girder connections.

Key Words
nonlinear response analysis, beam-yielding mechanism, shear crack, non-structural elements

Address
Matsumori T, Univ Tokyo, Grad Sch Engn, Dept Architecture, Bunkyo Ku, 7-3-1 Hongo, Tokyo 1138656, Japan
Univ Tokyo, Grad Sch Engn, Dept Architecture, Bunkyo Ku, Tokyo 1138656, Japan

Abstract
This paper deals with a special class of inverse problems in discrete structural plasticity involving the identification of elastic limits and hardening moduli on the basis of information on displacements. The governing equations lead naturally to a special and challenging optimization problem known as a Mathematical Program with Equilibrium Constraints (MPEC), a key feature of which is the orthogonality of two sign-constrained vectors or so-called \"complementarity\" condition. We investigate numerically the application of two simple algorithms, both based on the use of the general purpose nonlinear programming code CONOPT accessed via the GAMS modeling language, for solving the suitably reformulated problem. Application is illustrated by means of two numerical examples.

Key Words
complementarity, elastoplasticity, inverse problems, mathematical programming, structural identification.

Address
Ferris MC, Univ Wisconsin, Dept Comp Sci, 1210 W Dayton St, Madison, WI 53706 USA
Univ Wisconsin, Dept Comp Sci, Madison, WI 53706 USA
Univ New S Wales, Sch Civil & Environm Engn, Sydney, NSW 2052, Australia

Abstract
This paper presents a new design method of truss bridges using advanced analysis. In this approach, separate member capacity checks encompassed by the specification equations are not required because the stability of separate members and the structure as a whole can be treated rigorously for the determination of the maximum strength of the structures. The method is developed and refined by modifications to the conventional elastic-plastic hinge method. Verification studies are carried out by comparing with the plastic-zone solutions. The load-deflection behavior of the truss shows a good agreement between the plastic-zone analysis. A case study is provided for a truss bridge. Member sizes determined by the proposed method are compared with those determined by the conventional method. It is concluded that the proposed method is suitable for adoption in practice.

Key Words
steel design, advanced analysis, K-factor, truss bridge, nonlinear analysis.

Address
Sejong Univ, Dept Civil & Environm Engn, Seoul 143747, South Korea

Abstract
The strength, deformation and buckling of a large engineering structure consisting of four ellipsoidal shells, two cylindrical shells with stiffening ribs and large holes, one conical shell and three pairs of large flanges under external pressure, self weight and heat sinks have been analysed by using two kinds of five different finite elements - four assumed displacement finite elements (shell element with curved surfaces, axisymmetric conical shell element with variable thickness, three dimensional eccentric beam element, axisymmetric solid revolutionary element) and an assumed stress hybrid element (a 3-dimensional special element developed by authors). The compatibility between different elements is enforced. The strength analyses of the top cover and the main vessel are described in the paper.

Key Words
shell structure with stiffening ribs, large holes, strength analyses, finite element method.

Address
Tian ZS, Univ Sci & Technol China, Chinese Acad Sci, Grad Sch, Dept Mech, Beijing 100039, Peoples R China
Univ Sci & Technol China, Chinese Acad Sci, Grad Sch, Dept Mech, Beijing 100039, Peoples R China

Abstract
Most reliability-based analyses focus on the reliability of the individual components of a structure, There are many advantages to examining the components in combination as an entire structural system. This paper illustrates an algorithm used in the computer program RELSYS (RELiability of SYStems) which computes the system reliability of any structure which can be modeled as a series-parallel combination of its components, A first-order method is used to initially compute the reliability of each individual component. The system reliability is computed by successively reducing the series and parallel systems until the system has been simplified to a single equivalent component. Equivalent alpha vectors are used to account for the correlation between failure modes during the system reduction process.

Key Words
correlation, optimization, random variables, sensitivity, structural reliability, system reliability.

Address
Estes AC, Univ Colorado, Dept Civil Environm & Architectural Engn, Boulder, CO 80309 USA
Univ Colorado, Dept Civil Environm & Architectural Engn, Boulder, CO 80309 USA

Abstract
A new four-node degenerated shell element with drilling degrees of freedom (DOF) is proposed. Allman-type displacement approximation is incorporated into the formulation of degenerated shell elements. The approximation improves in-plane performance and eliminates singularities of system matrices resulted from DOF deficiency. Transverse shear locking is circumvented by introducing assumed covariant shear strains. Two kinds of penalty energy are considered in the formulation for the purpose of suppressing spurious modes and representing true drilling rotations. The proposed element can be applied to almost all kinds of shell problems including composite laminated shell structures and folded shell structures. Numerical examples show that the element is of good accuracy and of reasonably fast convergence rate.

Key Words
degenerated shell element, drilling DOF, Allman-type displacement approximation, composite laminated shell structures, folded structures, true drilling rotation.

Address
Kim JH, Korea Adv Inst Sci & Technol, Dept Engn Mech, 373-1 Kusong Dong, Taejon 305701, South Korea
Korea Adv Inst Sci & Technol, Dept Engn Mech, Taejon 305701, South Korea

Abstract
Vibration, buckling and dynamic stability of a cantilever rectangular plate subjected to an in-plane sinusoidally varying load applied along the free end are analyzed. The thin plate small deflection theory is used. The Rayleigh-Ritz method is employed to solve vibration and buckling of the plate. The dynamic stability problem is solved by using the Hamilton principle to drive time variables. The resulting time variables are solved by the harmonic balance method. Buckling properties and natural frequencies of the plate are shown at first. Unstable regions are presented for various loading conditions. Simple parametric resonances and combination resonances with sum type are obtained for various loading conditions, static load and damping.

Key Words
dynamic stability, cantilever rectangular plate, vibration, buckling.

Address
Takahashi K, Nagasaki Univ, Dept Civil Engn, 1-14 Bunkyo Machi, Nagasaki 8528131, Japan
Nagasaki Univ, Dept Civil Engn, Nagasaki 8528131, Japan

Abstract
Engineering problems are inherently imprecision tolerant. Biologically inspired soft computing methods are emerging as ideal tools for constructing intelligent engineering systems which employ approximate reasoning and exhibit imprecision tolerance. They also offer built-in mechanisms for dealing with uncertainty. The fundamental issues associated with engineering applications of the emerging soft computing methods are discussed, with emphasis on neural networks. A formalism for neural network representation is presented and recent developments on adaptive modeling of neural networks, specifically nested adaptive neural networks for constitutive modeling are discussed.

Key Words
neural networks, soft computing, computational mechanics, constitutive models.

Address
Ghaboussi J, Univ Illinois, Dept Civil Engn, Urbana, IL 61801 USA
Univ Illinois, Dept Civil Engn, Urbana, IL 61801 USA
Exxon Prod Res Co, Offshore Div, Houston, TX 77252 USA


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