IJBSTR RESEARCH PAPER VOL 1 [ISSUE 7] JULY 2013
ISSN 2320 – 6020
Analysis of Horizontally Curved Deck Slabs Using Simple Finite Element Method Rohit Rai ABSTRACT: A series of horizontally curved deck slabs were analyzed using simple finite-element models. The analyses included using a uniformly distributed load and the dead load as the primary forces on deck slab. In each analysis, the behavior of deck slabs was investigated, and the major internal forces developed in members were determined. Specifically, an increase in absolute stress and the existence of a torsion moment in cases where the horizontal angle of curvature is large (about 45–90°) was observed. The significance of these moments, compared with the maximum bending moment of a comparable straight bridge, was noted. Deck slab for practical purposes was assumed of sizes 90cm width and 200cm outer curves span. KEYWORDS: Curvature, Torsion Moment, Absolute Stress. INTRODUCTION Bridge superstructure with horizontal curvature generally has higher cost than comparable structures on straight alignment due to increased design fabrication and construction costs. In most instances, however, the extra cost is nominal and offset by the associated functional improvement. In the past, curved bridges had deck formed to follow the roadway curvature, but were supported a straight beams and girders with changing direction to accommodate the deck alignment. Since the early 1960s, curved spans and framing systems have become standard features of highway interchanges and urban expressways. A curved deck may still be placed on a series of straight beams or girders if the curvature is not very steep and the maximum slab overhang resulting from this arrangement is compatible with the practical slab thickness. Roadway curvature with small radius is common in access ramps and elevated roadways where the plan alignment is restricted by site conditions. In such cases clearance requirement and structural optimization may indicate a curved framing system that limits the cross-sectional variation and may also be economically competitive .The appearance of a curved framing system is more pleasing compared to straight girders placed on chord configuration. Rohit Rai
FINITE ELEMENT METHOD The finite element is a technique for analyzing complicated structures by notionally cutting up the continuum of the prototype into a number of small elements which are connected at discrete joints called nodes. For each element approximate stiffness equations are derived relating displacements of the nodes to node forces between elements and in the same way the slope –deflection equation can be solved for joints in a continuous beam, an electronic computer is used to solve the very large number of simultaneous equations that relate node force and displacements. Since the basic principle of subdivision of structure into simple elements can be applied to structures of all forms and complexity, there is no logical limit to the type of structure that can be analyzed if the computer program is written in the appropriate form. Consequently finite elements provide the more versatile method of analysis at present, and for some structures only practical method .However the quantity of computation can be enormous and expensive so that the cost cannot be justified for run of mill structures. Furthermore, the numerous different theoretical formulations of element stiffness characteristics all require approximations in different ways affect the accuracy and applicability of the method .Further research and development is required before the method will have the ease of use and reliability of the simple methods of bridge deck analysis.
Research Scholar
The technique was pioneered for two dimensional elastic structures by Turner et al and Clough during the1950s.
Department of Civil Engineering M.M.M. Engineering College Gorakhpur 273010 (UP) India Email: rohit.rai2609@gmail.com
The whole structure is divided into component elements, such as straight beams, curved beams, triangular or rectangular plate elements, which are joined at the nodes.
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