Techno Press
Tp_Editing System.E (TES.E)
Login Search


sem
 
CONTENTS
Volume 9, Number 6, June 2000
 

Abstract
In this study, a new functional based on the Reissner theory, for thick plates on a Winkler foundation is obtained. This functional has geometric and dynamic boundary conditions. In deriving the new functional, the Gateaux differential is used. This functional which is in polar coordinates is also transformable into the classical potential energy equation. Bending and torsional moments, transverse shear forces, rotations and displacements are the basic unknowns of the functional. Two different sectorial elements are developed with 3x8 degrees of freedom (SEC24) and 4x8 degrees of freedom (SEC32). The accuracy of the SEC24 and SEC32 elements together are verified by applying the method to some problems taken from literature.

Key Words
sectorial clement, Reissner plate, mixed-finite element

Address
Akoz AY, Istanbul Tech Univ, Dept Civil Engn, TR-80626 Maslak Turkey, Turkey
Istanbul Tech Univ, Dept Civil Engn, TR-80626 Maslak Turkey, Turkey

Abstract
Pultruded cross-sections are always thin-walled due to constraints in the manufacturing process. Thus, the buckling strength determines the overall strength of the member. The elastic buckling of pultruded angle sections subjected to direct compression is studied. The lateral-torsional buckling, very likely to appear in thin-walled cross-sections, is investigated. Plate theory is used to allow for cross-sectional distortion. Shear effects and bending-twisting coupling are accounted for in the analysis because of their significant role. A simplified approach for determining the maximum load of equal leg angle sections under compression is presented. The analytical results obtained in this study are compared to the manufacturer\'s design guidelines for compression members as well as with the design specifications for steel structural members. Experimental results are obtained for various length specimens of pultruded angle sections. The results presented in this paper correspond to actual pultruded equal leg angle sections being used in civil engineering structures.

Key Words
pultruded, composites, angle sections, lateral, torsional, buckling

Address
Polyzois D, Univ Manitoba, Dept Civil & Geol Engn, Winnipeg, MB, Canada
Univ Manitoba, Dept Civil & Geol Engn, Winnipeg, MB, Canada

Abstract
As time-variant reliability approaches become increasingly used for service life prediction of the aging infrastructure, the demand for computer solution methods continues to increase. Effcient computer techniques have become well established for the reliability analysis of structural systems. Thus far, however, this is largely limited to time-invariant reliability problems. Therefore, the requirements for time-variant reliability prediction of deteriorating structural systems under time-variant loads have remained incomplete. This study presents a computer program for RELiability of Time-Variant SYStems, RELTSYS. This program uses a combined technique of adaptive importance sampling, numerical integration, and fault tree analysis to compute time-variant reliabilities of individual components and systems. Time-invariant quantities are generated using Monte Carlo simulation, whereas time-variant quantities are evaluated using numerical integration. Load distribution and post-failure redistribution are considered using fault tree analysis. The strengths and limitations of RELTSYS are presented via a numerical example.


Key Words
deteriorating systems, fail-safe structures, importance sampling, life prediction, Monte Carlo simulation, numerical integration, random variables, time-variant reliability

Address
Enright MP, Univ Colorado, Dept Civil Environm & Architectural Engn, Campus Box 428, Boulder, CO 80309 USA
Univ Colorado, Dept Civil Environm & Architectural Engn, Boulder, CO 80309 USA

Abstract
The plastic collapse loads and their locations are predicted for a class of tapered, initially curved, and transversely corrugated cantilevered beams subjected to static tip loading. Results of both closed form and finite element solutions for several rigid perfectly plastic and elastic perfectly plastic beam models are evaluated. The governing equations are cast in nondimensional form for efficient studies of collapse load as it varies with beam geometry and the angle of the tip load. Static experiments for laboratory-scale configurations whose taper flared toward the tip, complemented the theory in that collapse occurred at points about 40% of the beams length from the fixed end. Experiments for low speed impact loading of these configurations showed that collapse occurred further from the fixed end, between the 61% and 71% points. The results may be applied to the design of safer highway guardrail terminal systems that collapse by design under vehicle impact.

Key Words
beam dynamics, elastic buckling, cantilevered beam, corrugated cross section, curved beam, guardrail, impact loading, initial curvature, plastic collapse, plastic hinge, tapered beam

Address
Wilson JF, Duke Univ, Dept Civil & Environm Engn, Durham, NC 27708 USA
Duke Univ, Dept Civil & Environm Engn, Durham, NC 27708 USA
Cairo Univ, Dept Civil Engn, Cairo, Egypt

Abstract
This paper attempts to provide a theoretical basis for the design of high-strength concrete columns in terms of the spacing of lateral reinforcement. In order to achieve this, important concepts had to be addressed such as the choice of a measure of ductile behaviour and a realistic high-strength concrete stress-strain model, as well as limiting factors such as longitudinal steel buckling and lateral steel fracture. A design method incorporating above factors are suggested in the paper. It is shown that both buckling of longitudinal steel and hoop fracture will not demand a reduction in spacing of lateral ties with increase in compressive strength of concrete.

Key Words
high-strength concrete, columns, design, ductility, lateral reinforcement, buckling

Address
Mendis PA, Univ Melbourne, Dept Civil & Environm Engn, Parkville, Vic 3052, Australia
Univ Melbourne, Dept Civil & Environm Engn, Parkville, Vic 3052, Australia
Worley Engn Ltd, Melbourne, Vic, Australia
Monash Univ, Dept Civil Engn, Clayton, Vic 3168, Australia

Abstract
Existing models for the shear strength degradation of reinforced concrete members present varied conceptual approaches to interpreting test data. The relative superiority of one approach over the others is difficult to determine, particularly given the sparseness of ideal test data. Nevertheless, existing models are compared using a suite of test data that were used for the development of one such model, and significant differences emerge. Rather than relying purely on column test data, the body of knowledge concerning degradation of concrete as a material is considered. Confined concrete relations are examined to infer details of the degradation process, and to establish a framework for developing phenomenologically-based models for shear strength degradation in reinforced concrete members. The possibility of linking column shear strength degradation with material degradation phenomena is explored with a simple model. The model is applied to the results of 7 column tests, and it is found that such a link is sustainable. It is expected that models founded on material degradation phenomena will be more reliable and more broadly applicable than the current generation of empirical shear strength degradation models.

Key Words
reinforced concrete, shear strength degradation, earthquake engineering, columns, plastic hinges, displacement capacity, ductility capacity, bridge piers

Address
Aschheim M, Univ Illinois, Dept Civil Engn, 2118 Newmark Lab,205 N Mathews Ave, Urbana, IL 61801 USA
Univ Illinois, Dept Civil Engn, Urbana, IL 61801 USA

Abstract
Some elevated water tanks have failed due to torsional vibrations in past earthquakes. The overall axisymmetric structural geometry and mass distribution of such structures may leave only a small accidental eccentricity between centre of stiffness and centre of mass. Such a small accidental eccentricity is not expected to cause a torsional failure. This paper studies the possibility of amplified torsional behaviour of elevated water tanks due to such small accidental eccentricity in the elastic as well as inelastic range; using two simple idealized systems with two coupled lateral-torsional degrees of freedom. The systems are capable of retaining the characteristics of two extreme categories of water tanks namely, a) tanks on staging with less number of columns and panels and b) tanks on staging with large number of columns and panels. The study shows that the presence of a small eccentricity may lead to large displacement of the staging edge in the elastic range, if the torsional-to-lateral time period ratio (tau) of the elevated tanks lies within a critical range of 0.7 < tau < 1.25. Inelastic behaviour study reveals that such excessive displacement in some of the reinforced concrete staging elements may cause unsymmetric yielding. This may lead to progressive strength deterioration through successive yielding in same elements under cyclic loading during earthquakes. Such localized strength drop progressively develop large strength eccentricity resulting in large localized inelastic displacement and ductility demand, leading to failure. So, elevated water tanks should have tau outside the said critical range to avoid amplified torsional response. The tanks supported on staging with less number of columns and panels are found to have greater torsional vulnerability. Tanks located near faults seem to have torsional vulnerability for large tau.

Key Words
lateral-torsional coupling, elevated water tanks, stagings, reinforced concrete, frame-type, inelastic, strength deterioration

Address
Dutta SC, Deemed Univ, Dept Appl Mech, Bengal Engn Coll, Howrah 711103, India
Deemed Univ, Dept Appl Mech, Bengal Engn Coll, Howrah 711103, India
Indian Inst Technol, Dept Civil Engn, Kanpur 208016, Uttar Pradesh, India


Techno-Press: Publishers of international journals and conference proceedings.       Copyright © 2017 Techno-Press
P.O. Box 33, Yuseong, Daejeon 34186 Korea, Tel: +82-42-828-7996, Fax : +82-42-828-7997, Email: info@techno-press.com