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CONTENTS
Volume 5, Number 4, August 2005
 

Abstract
Many slab-on-girder bridges around the world are being assessed because they are approaching the end of their anticipated design lives or codes are permitting higher allowable loads. Current analyticalrntechniques assume that the concrete and steel components act independently, typically requiring full-scale load testing to more accurately predict the remaining strength or endurance of the structure. However, many of the load tests carried out on these types of bridges would be unnecessary if the degree of interaction resulting from friction at the steel-concrete interface could be adequately modeled. Experimental testing confirmed that interface friction has a negligible effect on the flexural capacity of a slab-on-girder beam however, it also showed that interface friction is significant under serviceability loading. This has led to the development of an improved analytical technique which is presented in this paper and referred to as the slab-on-girder mixed analysis service load assessment approach.

Key Words
: mixed analysis; service load assessment; partial-interaction; non-composite; interface friction;rnslab-on-girder beams.

Address
School of Civil and Environmental Engineering, University of Adelaide, South Australia, 5005, Australia

Abstract
The seismic behavior of two steel moment-resisting frames, which satisfy all the current seismicrndesign requirements, are evaluated and compared in the presence of pre-Northridge connections denoted asrnBWWF and an improved post-Northridge connections denoted as BWWF-AD. Pre-Northridge connectionsrnare modeled first as fully restrained (FR) type. Then they are considered to be partially restrained (PR) tornmodel their behavior more realistically. The improved post-Northridge connections are modeled as PR type,rnas proposed by the authors. A sophisticated nonlinear time-domain finite element program developed by thernauthors is used for the response evaluation of the frames in terms of the overall rotation of the connections and the maximum drift. The frames are excited by ten recorded earthquake time histories. These time histories are then scaled up to produce some relevant response characteristics. The behaviors of the frames are studied comprehensively with the help of 120 analyses. Following important observations are made. The frames produced essentially similar rotation and drift for the connections modeled as FR type and PR type represented by BWWF-AD indicating that the presence of slots in the web of beams in BWWF-AD is not detrimental to the overall response behavior. When the lateral displacements of the frames are significantly large, the responses are improved if BWWF-AD type connections are used in the frames. This study analytically confirms many desirable features of BWWF-AD connections. PR frames have longer periods of vibration in comparison to FR frames and may attract lower inertia forces. However, calculated periods of the frames of this study using FEMA 350 empirical equation is longer than those calculated using dynamic characteristics of the frames. This may result in even lower design forces and may adversely influence the design.

Key Words
seismic analysis; response; nonlinear; steel frames; post-Northridge and pre-Northridge connection; beam-column connection; drift; PR and FR connection; connection rotation; stiffness; damage.

Address
Ali Mehrabian; West Coast Research Institute, 1233 Amherst Ave, Suite 105, Los Angeles, CA 90025, USArnAchintya Haldar; Department of Civil Engineering and Engineering Mechanics, University of Arizona, Tucson, AZ 85721, USArnAlfredo Reyes-Salazar; Universidad Autonoma de Sinaloa, Culiacan, Sinaloa, Mexico

Abstract
The inelastic buckling behaviour of continuously restrained two and three-span continuous beams subjected to concentrated loads and uniformly distributed loads are studied in this paper. The restraint type considered in this paper is fully restrained against translation and elastic twist applied at the top flange. These types of restraints are most likely experienced in industrial structures, for example steel-concrete composite beams and half through girders. The buckling analysis of continuous beam consists of two parts,firstly the moment and shear distribution along the member are determined by employing force method and the information is then used for an out-of-plane buckling analysis. The finite element method is incorporated with so-called simplified and the polynomial pattern of residual stress. Owing to the inelastic response of thernsteel, both the in-plane and out-of-plane analysis, which is treated as being uncoupled, extend into thernnonlinear range. This paper presents the results of inelastic lateral-torsional and lateral-distortional buckling load and finally conclusions are drawn regarding the web distortion.

Key Words
buckling; continuous restraint; lateral-distortion; plasticity; finite elements; load-height;rnmonosymmetry.

Address
4-6 Tangarra Street Croydon Park, NSW 2133, Australia

Abstract
. This paper presents a thorough investigation into the structural performance of cold-formed steelrncolumn bases using double lipped C sections with bolted moment connections. A total of four column baserntests with different connection configurations were carried out, and it was found that section failure under combined bending and shear was always critical. Moreover, the proposed column bases were demonstrated to be structurally efficient attaining moment resistances close to those of the connected sections.rnIn order to examine the structural behaviour of the column base connections, a finite element model wasrnestablished using shell and spring elements to model the sections and the bolted fastenings respectively. Both material and geometrical non-linearities were incorporated, and comparison between the test and thernnumerical results was presented in details. The design rules originally developed for bolted momentrnconnections between lapped Z sections were adopted and re-formulated for the design of column basernconnections after careful calibration against the test data. Comparison on co-existing moments and shearrnforces at the critical cross-sections of the column bases was fully presented. It was shown that the proposed design and analysis method was structurally adequate to predict the failure loads under combined bending and shear for column bases with similar connection configurations.

Key Words
column bases; bolted moment connections; section failure under combined bending and shear; finite element modelling.

Address
Department of Civil and Structural Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong SAR, P. R. China

Abstract
The European Standards Organisation (CEN) has planned to develop a complete set of harmonized European building standards. The Eurocodes, being the design standards, form part of this total system of European standards, together with standards for fabrication and erection and product standards. After a period of experimental use of the ENV(European Pre Standard)-versions of the Eurocodes, these are now converted into official EN? (European Standards). Design of composite steel and concrete buildings and bridges is covered by Eurocode 4. An overview will be given of the historic development of Eurocode 4, the structure and contents of the EN version and the present status and planning for completion. The Eurocode treatment of some selected technical items will be presented in more detail.

Key Words
composite structures; standards; Eurocodes.

Address
Delft University of Technology, Faculty of Civil Engineering and Geosciences, PO Box 5048, 2600 GA Delft, The Netherlands


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