A Fatigue Damage Analysis of Composite Construction Composed Asphalt Concrete Pavement and Steel-Box Beam Deck of Steel Bridge

Asphalt concrete is road pavement material with excellent property and is widely used in the steel bridge pavement. The system of steel bridge pavement is a composite structure composed asphalt surface and steel-box beam deck. Investigation shows that steel bridge deck support the mainly load in this composite structure. Because steel has good character on resisting fatigue, damage mainly generate in the asphalt concrete pavement under the moving vehicle loads. Fatigue crack has become one of main disasters in the bridge pavement. The system of steel bridge pavement can be simplified into a model of composite beam under some condition. Based on the bending test of composite beam simple, the curve of deflection in the midspan of composite beam vs the cycle number can be gained. Due to the damage accumulation in the asphalt concrete, the varieties of bending rigidity and mid-span deflection of composite beam in the fatigue process are studied by the method of damage mechanics. The control equations of fatigue damage are also developed. The prediction method of fatigue life of steel bridge pavement is discussed initially. The theoretical predictions are in good agreement with the experimental curve. Introduction Layered composite structure is widely used in engineering. The system of steel bridge pavement composed asphalt surface layer and steel-box beam deck is a typical layered composite construction. Due to the orthotropic feature of steel-box beam deck, transverse clapboard and rib lead to stress concentration. The fatigue cracks often emerge on asphalt layer under cycle load. The fatigue destroy of asphalt layer has become one of main disasters for steel bridge pavement failure [1]. Thus, using damage analysis to understand pavement failure mechanism and to predict its fatigue life has important engineering value. Since the 1950s end, the Kachanov brought up the damage mechanics concept, continuum damage mechanics have obtained the fast development in classical continuity mechanics and irreversible thermodynamics theories frame [2]. It has been applied in the metals, composite material, concrete.etc. engineering realm. The fatigue damage on asphalt concrete has lots of works [3,4]. Tang etc [5] derived the closed solution of fatigue crack and initiation life for bituminous mixtures based on continuum damage mechanics. But they only discussed same material and structure. In this paper, the damage and failure of beam composed asphalt concrete and steel-box beam deck will be analyzed by the method of continuum damage mechanics method. The losing of bending stiffness of composite beam in the fatigue process is studied. The control equations of fatigue damage are also deduced. Then proceed to the next step, the predict method of fatigue life span of steel bridge pavement is discussed. At last, the theoretical predictions are contrasted with the experimental cure. Key Engineering Materials Online: 2004-10-15 ISSN: 1662-9795, Vols. 274-276, pp 223-228 doi:10.4028/www.scientific. net/KEM.274-276.223 © 2004 Trans Tech Publications Ltd, Switzerland All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications Ltd, www.scientific. net. (Semanticscholar.org-13/03/20,17:14:05) The Analysis Model The numerical simulation results point out that the control stress of pavement is transverse maximum tensile stress located asphalt layer over trapezoid rib, that is dot A in figure 1. We intercept the part steel bridge pavement system and act as analysis model and test sample (see Figure 1). Model size: length 300mm, width100mm, steel plate depth 14mm, asphalt concrete depth 50mm, applied load 8kN. The curve of mid-span deflection vs load for bending test is illustrated in fig.2. The deflection of the mid-span is linear with load. This indicates that the sample deformation is elastic phases and satisfies the plane hypothesis. Due to the large discrepancy of steel elastic module Es and asphalt concrete elastic module Ea, let Es /Ea>100. Fig.1 Composite beam analysis model Fig. 2 The mid-span deflection-load curve The Analysis of Fatigue Damage Asphalt Concrete without Damage. The cross-section of composed beam is shown in Fig.3, where 0 s E 、 0 a E denote respectively the elastic module of steel plate and asphalt concrete without damage, 1 h 、 2 h and h denotes respectively the depth of the steel plate and asphalt concrete and the location of neutral plane. When the composite beam is bended, the mid-span deflection, the location of neutral axis and resistance bending stiffness are given: