John de Dalderby, Bishop of Lincoln, 1300-1320

[Preface:] On the floor of the South Transept of Lincoln Cathedral there is a plain stone slab bearing the following words in Gothic letters of brass,DalderbyEpisc.MCCCXIXThis stone is scarcely noticed by the numerous visitors who come to admire the beauty of the famous minster, and they pass over it to see the more obvious features of interest in the Cathedral. Yet the stone marks the resting place of the body of a man who made so great an impression upon the minds of the people of the diocese in his time that pilgrimages were made to his tomb in search of healing, and petitions were sent to the Pope asking for his canonisation

Experimental analysis of small masonry panels subject to long duration blast loading

Much research has been conducted towards short duration blast loading and its interaction with structures. The positive phase duration, t+, of a typical short duration high explosive blast is often below t+= 100ms. For the purposes of this research, long duration blast is considered to be an explosive event in which t+>100ms. This type of blast load offers added complexity when dealing with its interaction with structures due to the high impulses, drag winds and associated dynamic pressures. As part of an extended research study to develop a set of predictive algorithms, this paper investigates the breakage patterns and debris distribution of masonry panels subject to long duration blast loads. Experimental trials were conducted using the Air Blast Tunnel at MoD Shoeburyness, a specialised facility for long duration blast, in which two masonry panels were tested. The trials displayed varying degrees of breakage followed by a substantial debris distribution in both cases

Steel column response to thermal and long duration blast loads inside an air blast tunnel

This paper is closed access until 11 July 2020.All explosions emit both thermal and blast energy. In recent years there have been several accidental explosive events that have emitted high thermal loads with the potential to cause thermo-mechanical damage to structures. Attempts to experimentally simulate these thermal loads and observe the response of structures to combined thermal and blast loads have not proven successful. This paper focuses on the design of, and results from a series of experimental trials investigating the response of steel columns to combined thermal loads from ceramic heating elements and long-duration blast loads within an Air Blast Tunnel (ABT). The combined effect of compressive loads from heavy-duty springs is also shown. The trials concluded that the ceramic heating elements were suitable to heat steel columns to levels initiating thermo-mechanical damage. Results from the tests showed an increased structural response in the columns subject to high thermal, compressive and blast loads compared to the isolated blast load. Numerical modelling of the columns is detailed and compared to trial results, providing validation for the computational methods. The experimental trials set a benchmark for future trials and provided results to validate the synergistic response of steel structures to combined blast and thermal loads from explosive events

Long-duration blast loading and response of steel column sections at different angles of incidence

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 100ms, 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 long-duration 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

Evaluating long-duration blast loads on steel columns using computational fluid dynamics

Long-duration blasts are typically defined by positive pressure durations exceeding 100ms (Denny & Clubley, 2019; Johns & Clubley, 2016). Such blasts can generate dynamic pressures (blast winds) capable of exerting damaging drag loads on comparatively slender structural components such as columns. With limited drag coefficient availability for specific structural geometries, Computational Fluid Dynamics (CFD) can be the only satisfactory approach for analysing blast loading on user-specified, finite geometries. The ability to analyse long-duration blasts with commercially available CFD programs is still not confidently offered, with no prior studies examining the accuracy of modelling interaction with relatively much smaller, finite geometries. This paper presents a comparative investigation between numerical and experimental results to assess the predictive capacity of inviscid Eulerian CFD as a method for calculating long-duration blast drag loading on finite cross-section geometries. Full-scale long-duration blast experiments successfully measured surface pressure-time histories on a steel I-section column aligned at four orientations. Calculated pressure-time histories on exposed geometry surfaces demonstrated good agreement although reduced accuracy and under-prediction occurred on shielded surfaces manifesting as overestimated net loading. This study provides new understanding and awareness of the numerical capability and limitations of using CFD to calculate long-duration blast loads on intricate geometries

Experimental analysis of debris distribution of masonry panels subjected to long duration blast loading

Blast loading of structures is a complex system dependent on a vast number of parameters from both the structure and blast wave. Even for the simplest of structures, small changes to its size and shape can have a large effect on the result when subjected to blast; additionally, small changes to the pressure or duration of the blast wave can drastically alter its interaction with a specific structure. This paper, as part of a larger in-depth research study, investigates the breakage patterns and debris distribution of masonry panels subjected to blast loads with a positive phase duration typically exceeding 100 ms. Three experimental trials were conducted, in which ten masonry panels of varying geometries were subjected to blast loads with peak static overpressures of approximately 55 kPa and 110 kPa, with corresponding positive phase durations of 200 ms and 150 ms respectively. All structures underwent total structural failure, followed by significant debris distribution with the results showing structural geometry, blast overpressure and impulse to be the key parameters responsible for the breakage pattern, initial fragmentation and debris distribution respectively

Establishing a predictive method for blast induced masonry debris distribution using experimental and numerical methods

When subjected to blast loading, fragments ejected by concrete or masonry structures present a number of potential hazards. Airborne fragments pose a high risk of injury and secondary damage, with the resulting debris field causing major obstructions. The capability to predict the spatial distribution of debris of any structure as a function of parameterised blast loads will offer vital assistance to both emergency response and search and rescue operations and aid improvement of preventative measures. This paper proposes a new method to predict the debris distribution produced by masonry structures which are impacted by blast. It is proposed that describing structural geometry as an array of simple modular panels, the overall debris distribution can be predicted based on the distribution of each individual panel. Two experimental trials using 41 kg TNT equivalent charges, which subjected a total of nine small masonry structures to blast loading, were used to benchmark a computational modelling routine using the Applied Element Method (AEM). The computational spatial distribution presented good agreement with the experimental trials, closely matching breakage patterns, initial fragmentation and ground impact fragmentation. The collapse mechanisms were unpredictable due to the relatively low transmitted impulse; however, the debris distributions produced by AEM models with matching collapse mechanisms showed good agreement with the experimental trials

Damage state identification for reinforced concrete columns in uplift due to internal building detonations

This paper details the development of a generalised damage identification procedure for reinforced concrete columns subjected to internal building detonations. With the successful application of advanced computational fluid dynamics and structural response modelling techniques, we have conducted a set of comprehensive parametric studies on reinforced concrete column failure when subjected to high-rate, coupled uplift and shear typically induced by internal explosive blast. The outputs of the parametric studies have been analysed using a multi-variable, non-linear curve fitting technique to develop the generalised damage identification procedure for columns, separately for two main internal blast conditions. The paper also presents a number of worked examples illustrating its application and significance in practice

Experimentally investigating annealed glazing response to long-duration blast

This paper examines the response of annealed glazing panels when subject to long-duration blast loading. In particular, it quantifies glazing response metrics while varying glazing thickness, glazing area, aspect ratio, and edge conditions. With positive phases exceeding 100 ms long-duration blasts result in significant specific impulse and dynamic pressures. The transient dynamic response of annealed glazing during these events is a complex function of structural arrangement, material properties, and explosive proximity. Twelve full-scale air blast trials using a heavily armored test structure subjected 24 glazing panels to approximately 14-kPa free-field overpressure and approximately 110-ms positive-phase duration. Results are reported where it is shown that elastic-edge supports can prevent glazing breakage better than rigidly clamped arrangements when suitable panel dimensions are employed. Fragmentation modes are also demonstrated to be a function of edge conditions, with elastically supported panels producing large, angular fragments. In contrast, rigid arrangements are shown to induce localized impulsive stress transmission at clamped edges, leading to significant cracking and small fragments. Substantially different fragment masses and geometries demonstrate the need to accurately quantify edge supports when appraising fragment hazard. Quantification of peak panel deflection, breakage time, and applied breakage impulse is then presented, with results showing the influence of edge supports and aspect ratio on glazing response to be dependent on proximity to the threshold area for a particular thickness

The influence of structural arrangement on long-duration blast response of annealed glazing

This paper investigates the influence of structural arrangement on long-duration blast loaded annealed glazing via variable thickness, area, aspect ratio and edge support conditions. Initially, the findings of eighteen full-scale air-blast trials employing 33 annealed glazing panels are reported where it is demonstrated that fracture mode and fragmentation are a strong function of edge supports. Rigidly clamped edges are shown to induce localised stress transmission, producing significant cracking and small fragments. In contrast, elastic edges are shown to produce large, angular fragments, demonstrating the importance of accurately modelling edge conditions when analysing fragment hazard. Quantification of peak centre panel deflection and breakage time is then presented where variable results indicate the influence of edge supports and aspect ratio to be dependent on proximity to the threshold area as a function of glazing thickness. An initial Applied Element Method (AEM) analysis is then employed to model the influence of structural arrangement on long-duration blast-loaded annealed glazing. AEM models are shown to reasonably predict glazing fragmentation behaviour, breakage time and peak panel deflection at the moment of breakage. Thus indicating AEM's potential suitability to provide a predictive capacity for annealed glazing response during long-duration blast