DYNAMIC RESPONSE ANALYSIS FOR A LARGE-SCALE RC GIRDER. UNDER A FALLING-WEIGHT IMPACT LOADING

N. Kishi1, T. Ohno2, H. Konno3, and A. Q. Bhatti1

1 Department of Civil Engineering and Architecture, Muroran Institute of Technology, Muroran 050-8585, Japan; E-mail: kishi@news3.ce. muroran-it. ac. jp 2Department of Civil Engineering, National Defense Academy, Yokosuka 239-8686, Japan 3 Structural Division, Civil Engineering Research Inst. of Hokkaido, Hiragishi, Toyohira-Ward, Sapporo 062-8602, Japan

Abstract

In order to establish a rational impact resistant design procedure for prototype reinforced concrete (RC) structures, not only experimental study but also numerical analysis study should be conducted. However, numerical analysis method on impact response analysis for those structures has not been established yet. Here, in order to establish a rational numerical analysis method for prototype RC structures under impact loading, a falling-weight impact test was conducted for prototype RC girder with 8 m clear span. Referring to the experimental response waves, numerical accuracy was invest­igated varying major parameters. From this study, following results were obtained as: (1) fine mesh should be used near supporting gigues; (2) Drucker-Prager yield criterion should be applied which gives better results than von Mises one; and (3) appropriate system damping constant should be set to h = 0.015.

Keywords: prototype RC girder, falling-weight impact test, impact response analysis, LS-DYNA, Drucker-Prager yield criterion

1. Introduction

In Japan, design method concerning infrastructures tends to be shifted from allowable stress design method to performance based design one. Under such a situation, however, impact resistant design for RC structures has been still performed based on the allowable stress design concept. To ac­complish the shift of design method for RC structures under impact resistant design, experimental and numerical researches for small-scale members have been conducted (JSCE, 2004; Kishi et al., 2001; Kishi et al., 2002). On the other hand, impact research sub-committee of JSCE in Japan was managed round-robin pre/post analysis, which was conducted to confirm the numerical accuracy and characteristics of the method applied by each institution. From those researches, following conclusions were obtained: (1) from the pre-analysis results, it is too difficult to precisely predict numerically both impact force and reaction force waves obtained from the experimental results; and

(2) on the contrary, displacement wave can be better simulated comparing with above two response waves.

In general, a basic concept for designing RC members should be constituted based on the research findings for small-scale members and the applicability should be confirmed conducting large-scale experiments. In the cases of RC structures under shock and impact, however, it is not easy to conduct the experiments because of expenses for preparing of specimens and experimental set-up fittings. On the other hand, numerical simulations for large-scale impact test for RC members may be easily per­formed by using personal computers because of an advanced development of computer technology. Then, a rational impact resistant design procedure for RC members may be better established by

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M. Pandey et al. (eds), Advances in Engineering Structures, Mechanics & Construction, 99-109.

© 2006 Springer. Printed in the Netherlands.

Fig. 1. Dimensions of RC girder and measuring items.

supporting of numerical simulations. To accomplish this, a rational numerical simulation method for large-scale impact test must be established. Authors have discussed numerical simulation method using three-dimensional elasto-plastic finite element technique for small-scale impact test of RC beams (JSCE, 2004; Kishi et al., 1999). However, numerical investigations for large-scale impact tests have not been conducted yet.

From this point of view, in this paper, in order to establish a more precise numerical analysis method for analyzing elasto-plastic impact behavior of prototype RC structures, numerical accuracy of the results obtained using a three-dimensional elasto-plastic finite element method was investig­ated for each input parameter referring to the experimental results obtained from a falling-weight impact test for large-scale RC girder which was similar to that of designing roof of RC rock-sheds constructed over the highway to ensure people and vehicles safety. In this study, a general-purpose program LS-DYNA code, which is developed based on finite element method is used for those investigations (Hallquist, 2000).