Fire-induced structural failure: the World Trade Center, New York

Fire investigation has generally concentrated on determination of the cause and origin of a fire. Methodologies developed for this purpose have thus focused on the dynamics of fire growth and investigation of its effect on different objects within the structure affected by the fire. It is unusual to see a fire investigation emphasising structural damage as a way to obtain information for fire reconstruction. The series of dramatic fire events that occurred on 11 September 2001 within the World Trade Center, New York complex have emphasised the need to introduce structural analysis as a companion to evaluation of a fire timeline. Only a combined analysis is capable of providing a complete reconstruction of the event and therefore a solid determination of causality. This paper presents a methodology to establish, by means of modern structural and fire analysis tools, the sequence of events leading to a structural failure. This analysis will be compared with classic cause and origin techniques, emphasising the importance of a comprehensive study. Specific structural features and fire conditions that lead to unique forms of failure will be discussed, establishing the complexity of linking fire, structure characteristics and failure mode. The collapse of buildings 1 and 2 of the World Trade Center will be used to illustrate different forms of failure and the fires that cause them

How taphonomic alteration affects the detection and imaging of striations in stab wounds

Stabbing with a kitchen knife is a common methodof homicide in Europe. Serrated knives may leave tool mark-ings (striations) in tissues. Documentation of striations is nec-essary for their use as forensic evidence. Traditional methods(physical casting and photography) have significant limita-tions, and micro-computed tomography (micro-CT) has beentrialled in cartilage toBvirtually cast^wounds. Previous re-search has shown the proportion of striations in cartilage fallsfollowing decomposition. This project has investigated theeffects of taphonomic alteration and documentation methodsof striations in porcine skin. Fresh, decomposed, mummified,burnt and waterlogged stab wounds in a porcine analoguewere excised and imaged using photography, stereo-opticalmicroscopy and micro-CT. The proportion of striations ineach taphonomic group was determined from the images byindependent analysts. Striations were observed more frequent-ly in serrated blade wounds, although they were also identifiedin non-serrated blade wounds. The proportion of woundsshowing striations declined following decomposition. An in-versely proportional linear correlation between advancing de-composition and proportion of striations existed. Dehydration(mummification and burning) rendered serrated and non-serrated blade wounds indistinguishable. Water compositionaffected the preservation of striations. Identification ofstriations gradually declined after decomposition in tap water,but persisted to a point when left in brackish water. All threetechniques imaged striations; however, the optimum tech-nique was stereo-optical microscopy due to practical advan-tages and specific limitations affecting photography and mi-cro-CT. This study demonstrates the effects of taphonomicalteration on striations and suggests stereo-optical microscopyis the optimum method for their documentation

Fire performance of phase change material enhanced plasterboard

Sustainable construction materials are increasingly being used to reduce the carbon footprint of modern buildings. These materials have the potential to change the fire dynamics of compartments by altering the compartment energy balance however there is little quantitative understanding of how these materials behave in the event of a real fire. The changes in fire dynamics may be due to increased fuel load in a compartment, reduced time to failure or promotion of flame spread. The objective of this research is to quantify how Phase Change Materials (PCMs) perform in realistic fire scenarios. It was found that a plasterboard product containing microencapsulated PCMs will behave similarly to a charring solid and have the potential to contribute significant fuel to a compartment fire but that they maintain integrity for the duration of flaming period. The critical heat flux for this product was determined in the cone calorimeter to be 17.5 ± 2.5 kW m−2, the peak heat release rate and mass loss rate ranged from 60.2 kW m−2 to 107 kW m−2 and 1.88 g s−1 m−2 to 8.47 g s−1 m−2 respectively for exposures between 20 kW m−2 and 70 kW m−2. Sample orientation was found to increase the peak heat release rate by up to 25%, whilst having little to no effect on the mass loss rate. These parameters, in addition to the in-depth temperature evolution and ignition properties, can be used as design criteria for balancing energy savings with quantified fire performance

Stem cell factor has contrasting effects in combination with 5-fluorouracil or total-body irradiation on frequencies of different hemopoietic cell subsets and engraftment of transplanted bone marrow

The effect of stem cell factor (SCF) given at 24, 12 and 2 h before either 5-fluorouracil (5-FU) or total-body irradiation (TBI) was investigated on a range of bone marrow hemopoietic cell subsets that included primitive stem cells capable of longterm repopulation in bone marrow transplant (BMT) recipients. At 24 h after treatment, the femoral content of transient and permanent repopulating stem cell subsets was assessed from the frequency of early- and late-developing cobblestone area-forming cells (CAFCs) growing in stroma-associated cultures. At this time untreated 3 x 10(6) congenically marked donor bone marrow cells (B6-Gpi-1(a) --> B6-Gpi-1(b)) were transplanted and the level of erythroid engraftment was followed over 1 year. Analysis of the frequencies of CAFCs in host bone marrow after treatment with SCF demonstrated a remarkable increase in the number of early-developing CAFC subsets by about 10-fold, At the same time SCF conferred a sensitization of these subsets after treatment with 5-FU, which indicated an enhanced proliferative activity, The SCF-induced increase in the number of progenitor cells, however, was the more dominant process in the irradiated animals, resulting in less overall depletion of CAFCs. These contrasting results provide an explanation for the sensitization by SCF of 5-FU-induced lethality and its converse protection against radiation-induced lethality as reported by others. Nevertheless, the number of the more primitive CAFC subsets appearing at 28 and 35 days in culture and their sensitivity to 5-FU or radiation remained unaffected by this short SCF treatment. The number of CAFCs that remained in the bone marrow largely predicted the subsequent patterns of donor marrow engraftment in the treated BMT recipients: SCF enhanced short-term engraftment after treatment with 5-FU while it reduced the need for short-term engraftment after irradiation, Only irradiation afforded long-term engraftment through depletion of primitive host stem cells, and this was moderately improved by prior treatment with SCF. (C) 1997 by Radiation Research society