iTFM: improved travelling fires methodology for structural design and the effects on steel framed buildings

Accidental fire can be disastrous, especially in buildings. Most fire deaths occur due to the toxic effects of smoke before any structural collapse. However, the effect of fire on structural stability is critical in regard to safe evacuation and safe access for fire-fighters, financial losses, and lost business. This is particularly the case in tall buildings where extended evacuation times are required due to phased evacuation practises. The understanding of fundamental mechanisms of whole building behaviour in fire has significantly increased over the last decades, in particular after the full-scale tests of various multi-storey buildings carried out in Cardington between 1994 and 1999. However, most of the current understanding and consequently the design codes are based on the assumption of uniform fire conditions in a compartment. While this assumption may be suitable for small enclosures, fires in large open-plan compartments have been observed to travel. Examples of such fires include the World Trade Centre Towers 1, 2 & 7 (2001), Windsor Tower fire in Madrid (2006) and the recent fire at the Plasco building in Tehran (Jan 2017). All of these buildings ultimately either partly of fully collapsed. Current design standards do not account for travelling fires. The standard and parametric time-temperature curves are based on small scale tests, and assume uniform burning of fire and homogeneous temperature distributions in a compartment. In the recent years a new design concept of the Travelling Fires Methodology (TFM) has been developed by G. Rein to account for the travelling nature of fires in large compartments. This design methodology considers non-uniform temperature distribution in the compartment and a wide range of burning floor areas. In this thesis the Travelling Fires Methodology is improved to account for more realistic fire dynamics and then applied to investigate the structural response of a multi-storey steel frame using finite element software LS-DYNA. This thesis is presented in a manuscript style: each chapter takes the form of an independent paper, which has been published or submitted to a journal for publication. A final chapter summarizes the conclusions, and suggests potential areas of future research. Firstly, an improved Travelling Fires Methodology (iTFM) that accounts for better fire dynamics is presented in Chapter 2. Equations are introduced to reduce the range of possible fire sizes taking into account fire spread rates from real fires. The analytical equations used to represent the far-field temperatures are presented in continuous form. The concept of flame flapping is introduced to account for variation of temperatures in the near-field region due to natural fire oscillations. iTFM is then used to analyse the effect of non-uniform heating associated with travelling fires on the thermal response of structural members and identification of the location of peak temperature along the fire path. It is found to be mainly dependent on the fire spread rate and the heat release rate. Location of the peak temperature in the compartment is found to mostly occur towards the end of the fire path. Full-scale testing of real structures is complex, expensive and time consuming. This is especially the case for structures with large compartments. There has only been a limited number of full-scale tests on real buildings carried out worldwide (e.g. Cardington tests). As a result, computational tools are commonly used to assess the structural response of complex buildings under fire conditions. However, they have to be validated first. Therefore, in Chapter 3, prior to the study of the effects of iTFM on the structural response, explicit solver of finite element software LS-DYNA used for the analyses in Chapters 4-7 is benchmarked for structural fire analyses against other static numerical codes and experiments. Four canonical problems that encompass a range of thermal and mechanical behaviours in fire are simulated. The parameter sensitivity study is carried out to study the effects of various numerical parameters on the convergence to quasi-static solutions. The results confirm that when numerical parameters are carefully considered not to induce excessive inertia forces in the system, explicit dynamic analysis using LS-DYNA provide good predictions of the key variables of structural response during fire. Finally, the structural response of a two-dimensional multi-storey steel frame subjected to uniform design fires and iTFM (presented in Chapter 2) occurring on a single floor and multiple floors is investigated in Chapters 4, 5, & 7, and Chapters 6 & 7, respectively. Fire type and the location of the fire floor in the frame are varied. The analyses and comparison of structural response mechanisms is presented in Chapter 4. Uniform fires are found to result in higher compressive axial forces in beams compared to small travelling fires. However, results show irregular oscillations in member utilization levels in the range of 2 - 38% for the smallest travelling fire sizes, which are not observed for the uniform fires. Beam mid-span deflections are similar for both travelling fires and uniform fires and depend mainly on the fire duration, but the locations in the frame where these displacements occur are found to be different. Chapter 5 extends the study presented in Chapter 4 and compares the results in the terms of the limiting temperature criteria and various structural limit states. Critical fire scenarios are found to occur on the upper floors of the frame where column sections reduce in size. Also, results show that depending on the fire scenario higher level of fire protection for different members within the frame may lead to either enhanced or worse structural response and/or resistance. During previous fire events, e.g. the World Trade Centre Towers (WTC) 1, 2 & 7 in New York (2001), flames were observed to not only travel horizontally across the floor plate but also vertically to different floors. In this thesis, the effect of vertically travelling and multiple floor fires on the structural response of a two-dimensional multi-storey steel frame is investigated in Chapter 6. The number of fire floors, and horizontal and vertical fire spread are varied. Results show that the largest stresses develop in the fire floors adjacent to cool floors, and their behaviour is independent of the number of fire floors. All, the fire type, the number of fire floors, and the location of the fire floor, are found to have a significant effect on the failure time (i.e. exceeded element load carrying capacity) and the type of collapse mechanism (Chapter 7). In the cases with a low number of fire floors (1 to 3) failure is dominated by the loss of material strength, while in the cases with larger number of fire floors (5 to 10) failure is dominated by thermal expansion. Collapse is observed to be mainly initiated by the pull-in of external columns or swaying of the frame to the side of fire origin. Analyses presented in Chapters 4 to 7 highlight that in the structural design for fires it is important to consider more realistic fire scenarios associated with travelling fires as they might trigger previously unnoticed structural mechanisms. Results on the multi-storey steel frame indicate that, depending on the structural metric examined, both travelling fires and uniform fires can be more severe than the other. A single worst case fire scenario under which a structure could be designed and deemed to be safe cannot be established. For different fire exposures failure is found to occur on different range of floors subjected to fire. Therefore, in order to ensure a safe fire resistance design of buildings with large enclosures, a range of different fires including both travelling fires and uniform fires need to be considered.Open Acces

IMPROVED TRAVELLING FIRES METHODOLOGY - iTFM

Current design codes and most of the understanding of behaviour of structures in fire are based on small enclosure fires. The World Trade Centre Tower fires in 2001 have highlighted the need of a more realistic design tools to represent fires in large compartments. Following the events Travelling Fires Methodology (TFM) has been developed by Stern-Gottfried and Rein to account for the travelling nature of fires. In this study the TFM is refined to account for more realistic fire dynamics. Equations are introduced to reduce the range of possible fire sizes. The analytical equations describing reducing far-field temperatures are presented. The concept of flame flapping is introduced to account for variation of temperatures in the near-field region due to natural fire oscillations. The need for more fundamental research and experimental evidence in large compartments for further development of and improvements on TFMis highlighted

Structural response of a steel-frame building to horizontal and vertical travelling fires in multiple floors

During previous fire events such as the World Trade Centre Towers (WTC) 1, 2 & 7 in New York (2001), the Windsor Tower in Madrid (2005), and the Plasco building in Iran (2017), flames were observed to travel horizontally across the floor plate and vertically to different floors. Such fires are not considered as part of the traditional prescriptive structural design for fire. Recently, the Travelling Fires Methodology (TFM) has been developed to account for such horizontally travelling nature of fires. A dozen of studies have investigated the structural response of steel, concrete, and composite structures to a single-floor travelling fire. 5 out of 6 of the vertically travelling fire studies have been limited to the structures with a long span composite truss system as in the WTC Towers. The aim of this work is to investigate the response of a substantially different structural system, i.e. a generic multi-storey steel frame, subjected to travelling fires in multiple floors, and varying the number of fire floors, including horizontal and vertical fire spread. A two-dimensional 10-storey 5-bay steel frame is modelled in the finite element software LS-DYNA. The number of multiple fire floors is varied between 1 and 10, and for each of these scenarios, 5 different fire types are investigated. They include four travelling fire scenarios and the standard fire. In total, 51 fire simulations are considered. The development of deflections, axial forces, bending moments and frame utilization are analysed. Results show that the largest stresses develop in the fire floors adjacent to cool floors, and their behaviour is independent of the number of fire floors. Results indicate that both the fire type and the number of fire floors have a significant effect on the failure time (i.e. exceeded element load carrying capacity) and the type of collapse mechanism. In the cases with a low number of fire floors (1–3) failure is dominated by the loss of material strength, while in the cases with larger number of fire floors (5–10) failure is dominated by thermal expansion. Collapse is mainly initiated by the pull-in of external columns (1–3-floor fires; 1–9-floor fires for 2.5% TFM) or swaying of the frame to the side of fire origin (5–10-floor fires). This study has assessed a different structural form compared to previous literature under an extensive range of multiple floor travelling fire scenarios. We find that although vertically travelling fires result in larger beam axial forces and initial deflections, simultaneous travelling fires result in shorter failure times and represent a more onerous scenario for the steel frame investigated

Effects of a travelling fire on a concrete columns - Tisova Fire Test

The Tisova Fire Test was a large fire test conducted in the Czech Republic in January 2015 inside of a 4-storey concrete frame building, with concrete and composite deck floors. The test compartment was on the ground floor and the fire compartment had a total area of ca. 230m with a height of 4.4m. The fire compartment included four columns from the original 1958 concrete construction, one of which was instrumented for temperatures, chosen due to its higher likelihood of observable structural response both during and after the fire. This paper presents selected results of the test, concentrating on the thermal environment around the column showing the variability of temperatures through the compartment height. The paper also present the columns thermal response, as well as a post-fire assessments of the columns visual condition

Access to Intrathecal Baclofen Treatment for Children with Cerebral Palsy in European Countries: An SCPE Survey Reveals Important Differences

Aim: The aim is to study access to intrathecal baclofen (ITB) for children with cerebral palsy (CP) in Europe, as an indicator of access to advanced care. Methods: Surveys were sent to CP registers, clinical networks, and pump manufacturers. Enquiries were made about ITB treatment in children born in 1990 to 2005 by sex, CP type, level of gross motor function classification system (GMFCS) and age at the start of treatment. Access to ITB was related to the country's gross domestic product (GDP) and % GDP spent on health. Results: In 2011 population-based data from Sweden, Norway, England, Portugal, Slovenia, and Denmark showed that 114 (3.4%) of 3,398 children with CP were treated with ITB, varying from 0.4 to 4.7% between centers. The majority of the children were at GMFCS levels IV-V and had bilateral spastic CP. In Sweden, dyskinetic CP was the most commonly treated subtype. Boys were more often treated with ITB than girls (p = 0.014). ITB was reported to be available for children with CP in 25 of 43 countries. Access to ITB was associated with a higher GDP and %GDP spent on health (p < 0.01). Updated information from 2019 showed remaining differences between countries in ITB treatment and sex difference in treated children was maintained. Conclusion: There is a significant difference in access to ITB for children with CP across Europe. More boys than girls are treated. Access to ITB for children with CP is associated with GDP and percent of GDP spent on health in the country.info:eu-repo/semantics/publishedVersio

Development of The Viking Speech Scale to Classify the Speech of Children with Cerebral Palsy

Surveillance registers monitor the prevalence of cerebral palsy and the severity of resulting impairments across time and place. The motor disorders of cerebral palsy can affect children’s speech production and limit their intelligibility. We describe the development of a scale to classify children’s speech performance for use in cerebral palsy surveillance registers, and its reliability across raters and across time. Speech and language therapists, other healthcare professionals and parents classified the speech of 139 children with cerebral palsy (85 boys, 54 girls; mean age 6.03 years, SD 1.09) from observation and previous knowledge of the children. Another group of health professionals rated children’s speech from information in their medical notes. With the exception of parents, raters reclassified children’s speech at least four weeks after their initial classification. Raters were asked to rate how easy the scale was to use and how well the scale described the child’s speech production using Likert scales. Inter-rater reliability was moderate to substantial (k > .58 for all comparisons). Test–retest reliability was substantial to almost perfect for all groups (k > .68). Over 74% of raters found the scale easy or very easy to use; 66% of parents and over 70% of health care professionals judged the scale to describe children’s speech well or very well. We conclude that the Viking Speech Scale is a reliable tool to describe the speech performance of children with cerebral palsy, which can be applied through direct observation of children or through case note review

How does a chronic wound change a patient's social life?:A European survey on social support and social participation

Chronic wounds can severely limit patient's social life. This cross-sectional study investigated quantitatively social support of patients with chronic wounds, its association with health-related quality of life as well as qualitatively changes in social participation of these patients. Overall, 263 patients from seven countries participated. The most frequent wound class was leg ulcer (49.2%). Results revealed generally high levels of social support (mean global score: 5.5) as measured with the Multidimensional Scale of Perceived Social Support. However, individuals differed considerably (range 1.0–7.0). All dimensions of social support differed by patients' family and living situations (p &lt; 0.001 to p = 0.040) and were positively correlated with generic health-related quality of life (r = 0.136–0.172). Having children, living with others and being in a relationship were significant predictors of having higher global social support. Patients reported great support from family members. Many participants reported no changes in relationships with friends. Wound care managers took an important role and provided additional emotional support. Patients reported a range of discontinued activities. Despite the high overall level of social support, inter-individual differences should be acknowledged. The importance of family carers should be acknowledged to be able to reduce caregiver burden and to ensure high-qualitative wound care.</p

How does a chronic wound change a patient's social life? A European survey on social support and social participation

Chronic wounds can severely limit patient's social life. This cross-sectional study investigated quantitatively social support of patients with chronic wounds, its association with health-related quality of life as well as qualitatively changes in social participation of these patients. Overall, 263 patients from seven countries participated. The most frequent wound class was leg ulcer (49.2%). Results revealed generally high levels of social support (mean global score: 5.5) as measured with the Multidimensional Scale of Perceived Social Support. However, individuals differed considerably (range 1.0–7.0). All dimensions of social support differed by patients' family and living situations (p &lt; 0.001 to p = 0.040) and were positively correlated with generic health-related quality of life (r = 0.136–0.172). Having children, living with others and being in a relationship were significant predictors of having higher global social support. Patients reported great support from family members. Many participants reported no changes in relationships with friends. Wound care managers took an important role and provided additional emotional support. Patients reported a range of discontinued activities. Despite the high overall level of social support, inter-individual differences should be acknowledged. The importance of family carers should be acknowledged to be able to reduce caregiver burden and to ensure high-qualitative wound care.</p

Towards a fragility assessment of a concrete column exposed to a real fire – Tisova Fire Test

Fires can cause substantial damage to structures, both non-structural and structural, with economic losses of almost 1% GDP in developed countries. Whilst design codes allow engineers to design for the primary design driver, property protection is rarely, if ever, designed for. Quantification and design around property protection has been used for some time in the seismic community, particularly the PEER framework and fragility analyses. Fragility concepts have now started to be researched predominantly for steel-composite structures, however, there has been little to no research into the quantification of property protection for concrete structures, whether in design or in post-fire assessments of fire damaged structures. This paper presents selected results from the thermal environment around, and the thermal response of, a concrete column from a large scale structural fire test conducted in Tisova, Czech Republic, inside a four-storey concrete frame building, with concrete and composite deck floors. From the results of the fire test, assessments of the fire intensity are made and used to model the potential thermal profiles within the concrete column and the implications that high temperature might have on the post-fire response of the concrete column. These thermal profiles are then used to assess the reduction of the columns cross-sectional area and are compared to a quantified damage scale for concrete columns exposed to fire. This analyses presented herein will also show that common methods of defining fire intensity through equivalent fire durations do not appropriately account for the complexities of the thermal and structural response of concrete columns exposed to a travelling fire