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Selected Papers

[2012] Transient pressure loading of Clamped Plates with Holes

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Author Admin 작성일12-08-04 14:05 Hit57,733 Count Comments0 Count


FABIG Newletter, SCI, Issue 60, Pages 23-29, August 2012

Transient pressure loading of Clamped Plates with Holes

Author(s): G.K. Schleyer, N.J. Underwood, H.M. Do, J.K. Paik and B.J. Kim

Introduction: The purpose of the study reported in this article is to consider the effect of penetrations in plated deck structures found on offshore topsides and ship bulkheads so as to provide improved limit states assessment criteria to industry on the design of deck structures under blast loading [1-4].

The study utilizes a differential pressure device developed at the University of Liverpool Impact Research Centre capable of producing repeatable uniform transient pressure loading on 0.5 m by 0.5 m mild steel plate specimens nominally 1.1 mm thick corresponding to a scale of approximately 1:8. The device can impart typically 200kPa under 10 ms which, at this scale, can simulate a representative rise in overpressure produced by a semi-confined gas explosion.
Details of the experimental arrangement are described later and in Figures 2 and 3. The test data generated in this study will be used to validate numerical simulations and analytical models.

Typical overpressure from accidental explosions on topside structures is between 0.3 bar and 2 bar, with load durations generally between 50 ms and 200 ms [5]. However research conducted by the Steel Construction Institute proved that these overpressures can be significantly higher [6].

Previous studies on square plates and profiled blast walls [7-12] have shown that it is possible within the limitations of the procedures to relate the dynamic, large inelastic deformation of small-scale models to full-size structures provided the laws of geometrically similar scaling are followed. The plan is to extend previous work on mild steel plates by considering the effect of a central circular hole (ф50, 75 and 100 mm) and extended circular hole (ф50 by 75, ф75 by 100 and ф100 by 125 mm) on the loading, and localized stress and deformation.
Studies on plates with openings have had very limited attention in the past. Langdon et al. [13] recently investigated plates with small openings; however this focused on using perforations to mitigate the blast loading rather than their effects on the plate.
Li et al. [14] studied the explosion resistance of square plates with openings for venting dust explosions for applications in the process industry; very limited details were however provided.
Jain [15] investigated the effect of the hole aspect ratio of rectangular plates on the normal stress, shear stress and deflection in the transverse direction when loaded statically. However, to the authors’knowledge, no experimental studies have considered dynamic transverse loading on plates with openings.

Analytical studies have demonstrated the applicability of elasticplastic and rigid-plastic analytical methods for determining inelastic response of plated structures under blast loading [16-17].
It is important to consider the conditions when one is more appropriate than the other and when more sophisticated numerical methods should be used [18]. Equivalent non-linear single-degree-of-freedom (SDOF) methods can also be used for modelling plates with large inelastic deformations provided in-plane membrane effects are included.

Some experimental results are given here and compared with an energy solution based on an approximate deformed shape of a square plate under uniform pressure loading. Membrane action governs the behaviour of the plate for displacements greater than the plate thickness. Flexural resistance is considered negligible in this problem.
The analysis holds for elastic extensional deformation and may be used to predict maximum displacements. Due to the progressive development of plastic membrane strain in the plate, an approximation is used here to account for deformation beyond an elastic limit in the membrane mode.
This approach is not rigorously correct but is used to obtain acceptable engineering solutions to a complex problem. A weighted average displacement is computed based on the combination of the large-displacement elastic analysis and a rigid-plastic analysis of the plate.
The energy approach is appropriate for the estimation of global deformation. It cannot be used to directly predict local strains around the hole.

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