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CONTENTS
Volume 11, Number 1, February 2011
 

Abstract
The introduction of the Eurocodes makes plastic design criteria available also for composite bridges, leading to more economical solutions compared with previous elastic design rules. Particularly for refurbishment old bridges with higher actual traffic loads, up to date outside the scope of the Eurocodes, strengthening should therefore be avoidable or at least be necessary only to a minor extent. For bridges with smaller spans and compact cross sections, the plastic load bearing capacity is clearly justified. In this work, however, the focus is placed on long span continuous composite bridges with deep, longitudinally stiffened girders, susceptible to local buckling. In a first step, the elastic - plastic cross section capacity of the main girder in bending is studied as an isolated case, based on high preloads acting on the steel girder only, due to the common assembling procedure without scaffolding. In a second step, the effects on the whole structure are studied, because utilising the plastic section capacity at midspan leads to a redistribution of internal forces to the supports. Based on the comprehensive study of an old, actual strengthened composite bridge, some limitations for plastic design are identified. Moreover, fully plastic design will sometimes need additional global analysis. Practical recommendations are given for design purposes.

Key Words
plastic moment capacity; nonlinear global analysis; existing composite highway bridges.

Address
Institute of Steel Structures, Graz University of Technology, Lessingstra

Abstract
This study examines the influence of curved, steel, I-girder bridge configuration on girder end reactions and cross frame member forces during seismic events. Simply-supported bridge finite element models were created and examined under seismic events mimicking what could be experienced in AASHTO Seismic Zone 2. Bridges were analyzed using practical ranges of: radius of curvature; girder and cross frame spacings; and lateral bracing configuration. Results from the study indicated that: (1) radius of curvature had the greatest influence on seismic response; (2) interior (lowest radius) girder reactions were heavily influenced by parameter variations and, in certain instances, uplift at their bearings could be a concern; (3) vertical excitation more heavily influenced bearing and cross frame seismic response; and (4) lateral bracing helped reduce seismic effects but using bracing along the entire span did not provide additional benefit over placing bracing only in bays adjacent to the supports.

Key Words
Horizontally; curved, steel; I-girder; bridge; seismic; finite; element.

Address
Daniel G. Linzell : Department of Civil and Environmental Engineering, The Pennsylvania State University, 231L Sackett Bldg., University Park, PA 16802, USA
Venkata P. Nadakuditi : Stress Offshore, Inc., 13602 Westland East Blvd, Building 1, Houston, TX 77041

Abstract
The subject of the ongoing research work is to analyze the composite action of the structural elements of composite slabs with profiled steel decking by experimental and numerical studies. The mechanical and frictional interlocks result in a complex behaviour and failure under horizontal shear action. This is why the design characteristics can be determined only by standardized experiments. The aim of the current research is to develop a computational method which can predict the behaviour of embossed mechanical bond under shear actions, in order to derive the design characteristics of composite slabs with profiled steel decking. In the first phase of the research a novel experimental analysis is completed on an individual concrete encased embossment of steel strip under shear action. The experimental behaviour modes and failure mechanisms are determined. In parallel with the tests a finite element model is developed to follow the ultimate behaviour of this type of embossment, assuming that the phenomenon is governed by the failure of the steel part. The model is verified and applied to analyse the effect of embossment

Key Words
composite slab; embossment; shear action; pull-out test; numerical modelling; finite element simulation.

Address
Department of Structural Engineering, Budapest University of Technology and Economics, M egyetem rkp.3-5, H-1111 Budapest, Hungary

Abstract
Dynamic analysis of an embedded single-walled carbon nanotube (SWCNT) traversed by a moving nanoparticle, which is modeled as a moving load, is investigated in this study based on the nonlocal Timoshenko beam theory, including transverse shear deformation and rotary inertia. The governing equations and boundary conditions are derived by using the principle of virtual displacement. The Galerkin method and the direct integration method of Newmark are employed to find the dynamic response of the SWCNT. A detailed parametric study is conducted to study the influences of the nonlocal parameter, aspect ratio of the SWCNT, elastic medium constant and the moving load velocity on the dynamic responses of SWCNT. For comparison purpose, free vibration frequencies of the SWCNT are obtained and compared with a previously published study. Good agreement is observed. The results show that the above mentioned effects play an important role on the dynamic behaviour of the SWCNT.

Key Words
vibration; nonlocal Timoshenko beam theory; carbon nanotubes; moving loads.

Address
Yildiz Technical University, Department of Civil Engineering, Davutpasa Campus, 34210 Esenler-Istanbul, Turkey

Abstract
This study experimentally evaluated the seismic performance of steel knee braced frame structures with energy dissipation mechanism. A series of cyclic load tests were conducted on the steel moment resisting frames and the proposed knee braced frames. Test results validated that the demand in the beam-to-column connection designs was alleviated by the proposed design method. Test results also showed that the strength and stiffness of the proposed design were effectively enhanced. Comparisons in energy dissipation between the steel moment resisting frames and the steel knee braced frames further justified the applicability of the proposed method.

Key Words
Seismic performance; steel knee braced frame; energy dissipation; analytical model.

Address
Dept. of Civil Engineering, National Central University, Chung-Li, Taiwan 32054


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