Abstract
This paper reports experimental results pertaining to the effects of planar long-duration blast waves interacting with steel I-section column elements about different angles of incidence. Long-duration blast waves are typically defined by a positive pressure phase duration in excess of 100 ms, characteristic of very large explosion events such as industrial accidents. Blasts of this magnitude result in large impulses and dynamic pressures with the potential to exert high drag forces on column elements within an open frame structure. Due to relatively small dimensions in comparison to the blast wavelength, individual column elements are predominantly subjected to translational drag loading. Blast drag loading is complex to characterise, generally requiring approximation using drag coefficients, although proposed values in literature display inconsistency and typically lack provision for multi-axis interaction with I-shape geometries. Four full-scale long-duration experiments investigated blast interaction and elastic structural response of two steel I-section columns as a function of orientation to the incident shock wave. Drag coefficients were calculated as a function of I-section orientation using experimental pressure data and compared to values proposed in literature. It was found that drag coefficients proposed in literature have the potential to under-predict drag loading for certain oblique I-section orientations examined in these experiments. Importantly, intermediate oblique I-section orientations recorded higher loading and exhibited higher drag coefficients compared to orthogonal orientations, resulting in larger structural elastic response. Results from this experimental work have confirmed that I-section columns are axis-sensitive to blast wave direction giving rise to varying magnitudes of drag loading and structural response.
Highlights
This paper reports on experimental results investigating the effects of long-duration blast loading on steel I-section column elements
Recorded static and dynamic pressure-time histories were characteristic of an ideal blast wave type i.e. a Friedlander decay curve was observed some non-ideal discontinuities were observed throughout the positive phase duration (Fig. 7a and b). This occurred for all four trials and can be seen in archival pressure data for the Air Blast Tunnel (ABT) operating at maximum power, suggesting that this pattern is characteristic of the ABT facility [19,20]
It has been shown that structural blast response of an I-section column subjected to multiaxis long-duration blast loads is governed by section mechanical flexural properties and net blast drag loading, both of which are a function of the I-section orientation. These results demonstrate that multi-axis blast loading on I-section columns has a significant effect on structural response in terms of peak transient deflection
Summary
This paper reports on experimental results investigating the effects of long-duration blast loading on steel I-section column elements. Long-duration blast waves are typically defined by positive pressure durations over 100 ms, which develop in later stages of shock wave propagation i.e. in the ‘far field’ from the source of detonation Blast waves reaching this later stage of propagation with sufficient energy to cause structural damage are characteristic of very large-scale explosive events. Notable recent examples include the 2005 ‘Buncefield Disaster’, which exhibited an estimated TNT equivalence of 105–250 T TNT [1,2]. This caused damage to steel frame structures over a wide area and in many cases, the buildings had to be demolished or abandoned for prolonged time periods [3]. 150 buildings were damaged within a 4 km radius, the cost of which was estimated to exceed $100 million, 15 people were killed and ∼160 injured [5]
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