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CONTENTS
Volume 7, Number 1, January 1999
 

Abstract
Seismic evaluation of a 32-story reinforced concrete framed tube building is performed by checking damageability, safety, and toughness limit states. The evaluation is based on Standard 2800 (Iranian seismic code) which recommends equivalent lateral static force, modal superposition, or time history dynamic analysis methods to be applied. A three dimensional linearly elastic model checked by ambient vibration test results is used for the evaluation. Accelerograms of three earthquakes as well as linearly elastic design response spectra are used for dynamic analysis. Damageability is checked by considering story drift ratios. Safety is evaluated by comparing demands and capacities at the story and element force levels. Finally, toughness is studied in terms of curvature ductility of members. The paper explains the methodology selected and various aspects in detail.

Key Words
seismic vulnerability evaluation, framed tube building, response spectra, time history, ambient vibration, ductility, drift ratio, 3-D mathematical modeling.

Address
Memari AM, Penn State Univ, Dept Civil & Environm Engn, 212 Sackett Bldg, University Pk, PA 16802 USA
Penn State Univ, Dept Civil & Environm Engn, University Pk, PA 16802 USA
Int Inst Earthquake Engn & Seismol, Tehran, Iran

Abstract
The critical buckling loads of unsymmetrically laminated rectangular plates with a given material system and subjected to combined lateral and inplane loads are maximized with respect to fiber orientations by using a sequential linear programming method together with a simple move-limit strategy. Significant influence of plate aspect ratios, central circular cutouts, lateral loads and end conditions on the optimal fiber orientations and the associated optimal buckling loads of unsymmetrically laminated plates has been shown through this investigation.

Key Words
buckling, optimization, unsymmetrically laminated plates, end conditions, sequential linear programming

Address
Hu HT, Natl Cheng Kung Univ, Dept Civil Engn, Tainan 701, Taiwan
Natl Cheng Kung Univ, Dept Civil Engn, Tainan 701, Taiwan

Abstract
Realistic steel-concrete bond/slip relationships proposed in the literature are usually uniaxial. They are based on phenomenological theories of deformation and degradation mechanisms, and various pull-out tests. These relationships are usually implemented using different analytical methods for solving the differential equations of bond along the anchored portion, for particular situations. This paper justifies the concepts, and points out the assumptions underlying the construction and use of uniaxial bond laws. A finite element implementation is proposed using 2-D membrane elements. An application example on an interior beam-column joint illustrates the possibilities of this approach.

Key Words
finite element, nonlinear analysis, reinforced concrete, beam-column joints, steel-concrete bond, cyclic behavior

Address
Fleury F, Natl Inst Appl Sci, Civil Engn Res Unit URGC Struct, INSA Lyon, F-69621 Villeurbanne, France
Natl Inst Appl Sci, Civil Engn Res Unit URGC Struct, INSA Lyon, F-69621 Villeurbanne, France

Abstract
The natural frequencies and modes of free vibration of specially orthotropic elliptic and circular plates are analysed using the Rayleigh-Ritz method. The assumed functions used are two-dimensional boundary characteristic orthogonal polynomials which are generated using the Gram-Schmidt orthogonalization procedure. The first five natural frequencies are reported here for various values of aspect ratio of the ellipse. Results are given for various boundary conditions at the edges i.e., the boundary may be any of clamped, simply-supported or fret. Numerical results are presented here for several orthotropic material properties. For rectilinear orthotropic circular plates, a few results are available in the existing literature, which are compared with the present results and are found to be in good agreement.

Key Words
elliptic, orthotropic, vibration, plate, orthogonal polynomials, Rayleigh-Ritz

Address
Chakraverty S, Univ Southampton, Inst Sound & Vibrat Res, Southampton SO17 1BJ, Hants, England
Univ Southampton, Inst Sound & Vibrat Res, Southampton SO17 1BJ, Hants, England

Abstract
The purpose of this study is to propose an analytical model for the simulation of the hysteretic behavior of RC (reinforced concrete) beam-column subassemblages under various loading histories. The discrete line element with inelastic rotational springs is adopted to model the different locations of the plastic hinging zone. The hysteresis model can be adopted for a dynamic two-dimensional inelastic analysis of RC frame structures. From the analysis of test results it is found that the stiffness deterioration caused by inelastic loading can be simulated with a function of basic pinching coefficients, ductility ratio and yield strength ratio of members. A new strength degradation coefficient is proposed to simulate the inelastic behavior of members as a function of the transverse steel spacing and section aspect ratio. The energy dissipation capacities calculated using the proposed model show a good agreement with test results within errors of 27%.

Key Words
discrete line element, hysteretic model, inelastic rotational spring, plastic hinging zone, beam-column subassemblages, strength degradation, stiffness deterioration, energy dissipation capacity, cyclic loads, structural analysis

Address
You YC, Korea Inst Construct Technol, Bldg Struct & Prod Div, Lisan Gu, Koyang 411410, South Korea
Korea Inst Construct Technol, Bldg Struct & Prod Div, Lisan Gu, Koyang 411410, South Korea
Kwang Woon Univ, Dept Architectural Engn, Seoul 139701, South Korea
Hanyang Univ, Dept Architectural Engn, Seoul 133791, South Korea

Abstract
The dynamic analysis of trusses using the finite element method tends to overlook the effect of local member dynamic behavior on the overall response of the complete structure. This is due to the fact that the lateral inertias of the members are omitted from the global inertia terms in the structure mass matrix. In this paper a condensed dynamic stiffness matrix is formulated and used to calculate the exact dynamic properties of trusses without the need to increase the model size. In the examples the limitations of current solutions are presented together with the exact results obtained from the proposed method.

Key Words
dynamic stiffness matrix, local mode shape, large structure, condensed dynamic stiffness matrix, finite elements

Address
Levy E, Technion Israel Inst Technol, Fac Agr Engn, IL-32000 Haifa, Israel
Technion Israel Inst Technol, Fac Agr Engn, IL-32000 Haifa, Israel
Technion Israel Inst Technol, Fac Civil Engn, IL-32000 Haifa, Israel

Abstract
An effective moment of inertia is developed for a rectangular, prismatic elastoplastic beam with elastic, linear-hardening material behavior. The particular solution for a beam with elastic, perfectly plastic material behavior is also presented with applications for beam bending in closed-form. Equations are presented for the direct application of the virtual work method for elastoplastic beams with concentrated and distributed loads. Comparisons are made between the virtual work method deflections and the deflections obtained by using an average effective moment of inertia over two lengths of the beam in the elastoplastic region.

Key Words
elastoplastic beams, effective moment of inertia, deflections, elastic, linear-hardening, elastic, perfectly plastic, virtual work

Address
Faller RK, Univ Nebraska, Dept Civil Engn, W348 Nebraska Hall, Lincoln, NE 68588 USA
Univ Nebraska, Dept Civil Engn, Lincoln, NE 68588 USA

Abstract
The work presented here focuses on the development of suitable discretised formulations, for large-displacement shape and non-shape design sensitivity analysis (DSA), which enable the straightforward incorporation of structural optimisation into established finite element analysis (FEA) codes. For the generalised displacement-based functional the design sensitivity vector has been expressed in terms of displacement sensitivity. The Total Lagrangian formulation is utilised for modelling of large deformation of truss structures. The variational formulation of the sensitivity analysis procedure is discretised by using \"pseudo\" - finite elements, Results are presented for the sensitivity analysis and optimisation of standard truss structures. For the purposes of this work, the analysis and optimisation procedures outlined below are incorporated into the FEA code ABAQUS.

Key Words
structural optimisation, design sensitivity analysis, finite element method

Address
Bothma AS, Univ Cape Town, Dept Math & Appl Math, ZA-7700 Rondebosch, South Africa
Univ Cape Town, Dept Math & Appl Math, ZA-7700 Rondebosch, South Africa
Polish Acad Sci, Inst Fundamental Technol Res, PL-0049 Warsaw, Poland


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