Experimental and numerical study on the fire resistance behavior of steel truss girder structure in double deck suspension bridges

A great deal of work on the behavior of composite steel-concrete structures in fire has been developed since the Cardington frame fire tests (UK) conducted in the 1990s. This has now been broadened so that the design of structures to resist fire has a real engineering basis and is not reliant on results from single element testing in the standard furnace. Several projects involving office buildings in the UK and abroad have highlighted the need for developing the understanding of whole frame behavior in fire. Since the collapse of the World Trade Center in New York City in 2001 (9/11), robust engineering solutions incorporating the response of a building to fire are in great demand. The basics of structural mechanics at high temperatures can be used in such designs to understand the fire response of many structures with the aid of computer modeling. This article provides a direct comparison between the structural response of an eleven-story office building in the city of London, when designed in a prescriptive manner with applied fire protection on all load bearing steelwork, and the response of the same structure designed using a performance-based approach leaving the majority of secondary steelwork unprotected. The intent is to demonstrate that structural stability during a fire can be maintained in specific cases without relying on passive fire protection. This study contributes to the field of structural fire engineering by extending the research work previously conducted by the author to a real design case and addresses the issues raised by approving authorities, insurers, and the client when a fire engineered approach is used to calculate structural response to fire. It also demonstrates the use of advanced analysis to understand beam-core connection

A review of the fire behaviour of pultruded GFRP structural profiles for civil engineering applications

Review and discussion on fire behavior of bridge girders

Cold-formed steel members can be assembled in various combinations to provide cost-efficient and safe light gauge floor systems for buildings. Such Light gauge Steel Framing (LSF) systems are widely accepted in industrial and commercial building construction. An example application is in floor-ceiling systems. Light gauge steel floor-ceiling systems must be designed to serve as fire compartment boundaries and provide adequate fire resistance. Fire-rated floor-ceiling assemblies formed with new materials and construction methodologies have been increasingly used in buildings. However, limited research has been undertaken in the past and hence a thorough understanding of their fire resistance behaviour is not available. Recently a new composite floor-ceiling system has been developed to provide higher fire rating under standard fire conditions. But its increased fire rating could not be determined using the currently available design methods. Therefore a research project was carried out to investigate its structural and fire resistance behaviour under standard fire conditions. In this research project full scale experimental tests of the new LSF floor system based on a composite ceiling unit were undertaken using a gas furnace at the Queensland University of Technology. Both the conventional and the new steel floor-ceiling systems were tested under structural and fire loads. Full scale fire tests provided a good understanding of the fire behaviour of the LSF floor-ceiling systems and confirmed the superior performance of the new composite system. This paper presents the details of this research into the structural and fire behaviour of light gauge steel floor systems protected by the new composite panel, and the results.

In recent years, increasing interest has been shown throughout Europe in developing and designing slim floor systems in steel-framed buildings. This paper presents the fire resistance behavior of the composite asymmetric slim floor beam as an isolated member and as a part of the frame using numerical analysis methods. Three schemes were investigated, including isolated beams, a plane subframe with semirigid beam-to-column connections, and a 3D slim floor frame system. The first scheme aimed to explore the fire resistance of the beams according to standard fire-testing methodology. The objective of the second scheme was to reveal the effect of frame continuity on the fire resistance of the slim floor beam and the mechanical interaction between the frame elements. The third scheme was to preliminarily identify the influence of the composite slab on the beam behavior in fire. The investigations show that the isolated slim floor beam has a 60-min standard fire resistance without any additional fire protection, if the load ratio is <0.5. As a part of the frame, the beam still keeps its stability even when the temperature of the bottom steel flange of the beam reaches up to 900°C (90-min ISO fire exposure). The analyzed results indicate that the axial restraints provided by the surrounding parts cause a larger deformation of the beam in the earlier ISO heating phase and a more stable behavior thereafter. The rotational restraints essentially cause the change in the applied load ratio in fire, which can be quantified using the “modified load ratio” proposed in this paper.

Historically fire resistance design of structures has been based upon single element behavior in the standard fire resistance test. Engineers have always recognized that whole frame structural behavior in fire cannot be described by a test on a single element. However, it is only in relatively recent years since the Broadgate phase 8 fire (SCI, 1991) and the subsequent Cardington frame fire tests that researchers have fully nvestigated and understood the behavior of whole structures in response to fire. The University of Edinburgh in collaboration with Imperial College and Corus (formally British Steel) have played a major role in this field of research through the UK Department of Environment and Transport in the Regions (DETR), Partners in Technology (PiT) project. Significant progress towards a complete understanding of the structural behavior of highly redundant composite steel frames in fire has been achieved (Edinburgh University, 2000). It has been shown that the fire resistance test has little relevance to the behavior of structural elements as part of highly indeterminate structures typical of modern, composite steel frame buildings. The test methods are particularly inadequate when the end conditions during service are unknown and the beam is tested as simply supported, i.e. no consideration of restraint is made. By including the effect of restraint in a simple beam model the temperature at which "runaway" occurs is greatly increased. The reasons for this, i.e. the changing load-carrying mechanisms involved as catenary action develops as a result of the deflected shape have also been explained.

The consumption of Ordinary Portland Cement (OPC) as construction material is one of the main sources of CO2 emission and global warming.. The manufacturing process of ‘clinker’ which is an essential element of cement requires burning of fossil fuels, thus increasing the CO2 emission and decreasing the global stock of fuels. Concept of a novel binding material named ‘Geopolymer’ appeared in the 1940s as a viable solution to these issues. Geopolymer concrete (GPC) is produced from industrial byproducts such as Fly Ash (FA) rich in aluminosilicate, Blast furnace slag (BFS) or natural minerals such as Kaolinite clay using alkalis as activators. In this paper, economical, social and ecological sustainability of GPC have been put forth. Comparison have been made between the behavior of low-calcium fly ash based GPC and metakaolin based GPC under different environmental conditions using alkali activators such as Sodium hydroxide (NaOH) or Potassium hydroxide (KOH) with Sodium silicate (Na2SiO3) . Evolution of GPC, hydration process as opposed to OPC, mechanical properties, structural behavior, alkali-silica resistance (ASR), fire and acid resistance behavior of GPC have also been discussed in this paper.

In Korea recently, interest is increasing in slim floor systems that have superior structural performance and fire resistance. This paper contains the results of tests to confirm the fire resistance behavior of the composite asymmetric slim floor beam. The fire resistance behavior was analyzed using the finite element program ANSYS and the finite element models were validated against the test results. The validated thermal and structural models were used to predict the fire resistance of the Korean asymmetric floor beam and the average temperature of the steel bottom flange depending on load ratio changes. As a result, the 346ASB and the 350ASB were found to have 60 minutes of fire resistance when their load ratios were under 0.47 and 0.48 respectively without additional fire protection. Also, the authors have set the average temperature of the bottom flange, which has a direct impact on the ASB system, as a limiting temperature that enables gauging of its fire resistance as a table according to the load ratio, and presented the limiting temperature as a regression equation according to the fire resistance time.

Damping in double Cables suspension bridge composed of steel reinforcement beams and reinforced concrete tower is non-classical, which leads to coupled equations of motion in main coordinate system. Based on the complex damping theory, the viscous damping ratio is solved, which can be used to describe energy dissipation characteristics of non-classical damping system approximately. Seismic response of double chains suspension bridge is analyzed through an example of double chains suspension bridge, considering the geometric nonlinearity and non-classical damping. And numerical calculation is presented for seismic response subjected to independent effect or combination effect of three orthogonal components of seismic wave. Single cable suspension bridge can be taken as a special case of double cable suspension bridge, after the main cable shape coefficient is introduced. The dynamic responses of double cable suspension bridge and single cable suspension bridge are compared to reveal the characteristics of Seismic Response of double cable suspension bridge. The study of the dynamic responses characteristics of double cable suspension bridge has a positive significance on structural form selection of such type bridge during designing, dynamic performance evaluation and reinforcement design has positive significance.

Textiles are very hazardous materials when related to fires, because of the high surface to mass ratio and the open structure, which simplify the contact with heat and oxygen. Fabrics have a great impact on the development of fatal fires because of their easy ignition and high burning rate. For the flame retardancy of fabrics several strategies have been developed throughout the years, and nowadays additives and reagents are widely used for the different kinds of textiles. The most common commercial durable finishes for cotton fabrics contain phosphorous and nitrogen compounds. These products have been predominant in the field of flame retardants for cotton for 50 years, but recently the request for a reduction of environmental impact and of formaldehyde release during manufacturing and utilisation have pushed researchers towards new kinds of finishing. This Ph.D. work aimed at investigating the effectiveness and the possibilities of the use of biomacromolecules as fire retardants for cellulosic textiles (i.e. cotton). To this aim, three biomacromolecules were taken in consideration: whey proteins, caseins and nucleic acids. Whey proteins and caseins, derived from milk, were applied on cotton fabrics and their thermal and thermo-oxidative stability and fire behaviour were assessed through thermogravimetric analysis, cone calorimetry and horizontal flame spread tests. These biomacromolecules were effective in improving the fire retardancy of the treated fabrics, slowing down the combustion rate in flame spread tests and favouring the formation of a coherent carbonaceous residue (char). Then, the fire retardant behaviour of DNA was thoroughly investigated. First, commercially-available DNA from herring sperm and testes, having different molecular weights, were applied on cotton fabrics: the experimental parameters (i.e., molecular weight of the biomacromolecules, pH of the aqueous solution, number of impregnations needed for achieving the final dry add-on on the treated fabrics) were optimized in order to achieve the highest flame retardant effectiveness. The distribution of the nucleic acids on the underlying fabric was studied through SEM analyses. Thermogravimetric analyses, cone calorimetry and horizontal flame spread tests were carried out for assessing the thermal and thermo-oxidative stability and the fire behaviour of the treated fabrics. In detail, the low-molecular-weight DNA solution prepared either at pH 4 or 8 and applied on cotton with multiple impregnation steps was the most effective flame retardant treatment. Pursuing the research, the problem related to the high cost of commercially available DNA was considered: to overcome this drawback, a novel extraction method, starting from exhausted biomasses or agro-food crops, was developed. This method focused on the extraction of high quantities of nucleic acids, exploiting a low environmental impact approach. Overall, the recovered nucleic acids showed a fire behaviour similar to that of commercially-available counterparts. Finally, the washing fastness of the cotton fabrics treated with the biomacromolecules was considered: in fact, all the selected biomacromolecules are waterborne systems, which easily come off the fabrics when subjected to washing cycles, even in hot water only. This issue was taken on by treating cotton fabrics with nucleic acids and chitosan in mixture or as separate layers and also exploiting the layer by layer technique. The washing fastness of the treated fabrics was significantly improved by subjecting them to UV-curing, thus achieving the grafting of chitosan on cotton and, at the same time, entrapping the nucleic acid in the grafted chitosan coating. Notwithstanding the achieved fire retardancy, the fabrics treated with chitosan and nucleic acids also showed an antibacterial activity, due to the presence of chitosan. Furthermore, 30 bilayers of nucleic acids and chitosan provided the fabrics with self-extinction, either before and after a water washing cycle at 55°C. As far as the effectiveness of the treatments is concerned, all the selected biomacromolecules conferred fire retardant features to cotton fabrics. In particular, low-molecular-weight nucleic acids and caseins were the most performing biomacromolecules either in forced combustion or in flame spread tests. Cotton fabrics treated with nucleic acids or caseins were able to achieve self-extinction in horizontal flame spread tests, with a reduction of the burning rate and an increase of the residue left. Similar reductions in the HRR were also observed in cone calorimetry tests. The suggested approach is quite simple and does not involve the use of particular chemicals or expensive equipment; furthermore, the selected biomacromolecules are soluble/dispersible in water. In conclusion, the proposed flame retardants for cotton may represent a new sustainable approach to face the challenges related to the increasing awareness of the health and environmental impact of traditional products and processes.

On revealing the effect of alkaline lignin and ammonium polyphosphate additives on fire retardant properties of sustainable zein-based composites

The use of dispersed reinforcement improves the properties of concrete. Recently, some studies have been conducted to explore the effect of dispersed reinforcement on the behavior of structures under a static load of the same sign or alternating static load when reinforcing with relatively long fibers.The article presents a methodology for experimental study of the behavior of beam elements with dispersed and combined reinforcement under an alternating static load, based on mathematical planning using a specially made frame.The work considers the results of experimental studies of cubes and prisms on a static load and compression. It also presents the results of an experimental study of the behavior of beam structures with dispersed and combined reinforcement with relatively short fibers under low-cycle alternating static action. The behavior of fiber-reinforced concrete and reinforced concrete beam elements under similar influences are compared.The presented results of the experimental studies allow us to show a significant effect of dispersed reinforcement with relatively short fibers on the behavior of beam structures with alternating low-cycle static loads and the feasibility of combined reinforcement of structures operating under such loads.The use of dispersed reinforcement with relatively short fibers in combined reinforced beam structures operating under alternating loads will increase crack resistance, and with a certain percentage of reinforcement, the strength of such structures. Moreover, the use of relatively short fibers will significantly reduce the complexity of manufacturing such structures.

This paper aims to study the mechanical performance of three-tower four-span suspension bridges with steel truss girders, including the static and dynamic characteristics of the bridge system, and more importantly, the influence of structural parameters including the side-main span ratio, sag-to-span ratio and the girder stiffness on key mechanical indices. For this purpose, the Oujiang River North Estuary Bridge which is a three-tower four-span suspension bridge with two main spans of 800m under construction in China is taken as an example in this study. This will be the first three-tower suspension bridge with steel truss girders in the world. The mechanical performance study and parametric analysis are conducted based on a validated three-dimensional spatial truss finite element model established for the Oujiang River North Estuary Bridge using MIDAS Civil. It is found that a relatively small side-main span ratio seems to be quite appropriate from the perspective of mechanical performance. And decreasing the sag-to-span ratio is an effective way to reduce the horizontal force subjected to the midtower and improve the antiskid safety of the main cable, while the vertical stiffness of the bridge will be reduced. However, the girder stiffness is shown to be of minimal significance on the mechanical performance. The findings from this paper can be used for design of three-tower suspension bridges with steel truss girders.

As research continues into how fire department interventions affect fire dynamics in the modern fire environment, questions continue to arise on the impact and implications of interior versus exterior fire attack on both firefighter safety and occupant survivability. Previous research into various types of fire ground ventilation, flow paths, and exterior fire streams has provided the fire service with an increased understanding of fire dynamics. However, in some instances, the information from the studies did not support current, experience-based practices. This gap between the research to date and the fire ground suppression experience has driven the need for further study. This study will build upon the fire research conducted to date by analyzing how firefighting tactics, specifically different fire suppression tools and tactics, affect the thermal exposure and survivability of both firefighters and building occupants and affect fire behavior in structures. The purpose of this study is to improve firefighter safety, fire ground tactics, and the knowledge of fire dynamics by providing the fire service with scientific information, developed from water flow and full-scale fire testing, in representative single-family homes. This study will build and expand upon the fire research conducted to date by analyzing how firefighting tactics, specifically suppression methods, affect the thermal exposure and survivability of both firefighters and building occupants in addition to impacting fire behavior in structures. The purpose of this study is to improve firefighter safety, fireground tactics, and the knowledge of fire dynamics by providing the fire service with credible scientific information, developed from both water flow and full-scale fire testing, in representative single family homes. The project is comprised of 3 parts: • Part I: Water Distribution • Part II: Air Entrainment • Part III: Full-Scale Residential Fire Experiments This report details the results and analysis from the air entrainment testing. These tests were conducted without the presence of fire to gain a fundamental understanding of how hose streams entrain air. Each set of experiments was intended to add to the understanding of air entrainment and pressure from fire service hose streams by evaluating the differences caused by various application methods, hose stream types, nozzle movements, pressures/flow rates, manufacturers, and ventilation configurations.

BackgroundFire managers tasked with assessing the hazard and risk of wildfire in Alaska, USA, tend to have more confidence in fire behavior prediction modeling systems developed in Canada than similar systems developed in the US. In 1992, Canadian fire behavior systems were adopted for modeling fire hazard and risk in Alaska and are used by fire suppression specialists and fire planners working within the state. However, as new US-based fire behavior modeling tools are developed, Alaskan fire managers are encouraged to adopt the use of US-based systems. Few studies exist in the scientific literature that inform fire managers as to the efficacy of fire behavior modeling tools in Alaska. In this study, I provide information to aid fire managers when tasked with deciding which system for modeling fire behavior is most appropriate for their use. On the Magitchlie Creek Fire in Alaska, I systematically collected fire behavior characteristics within a black spruce (Picea mariana [Mill.] Britton, Sterns & Poggenb.) ecosystem under head fire conditions. I compared my fire behavior observations including flame length, rate of spread, and head fire intensity with fire behavior predictions from the US fire modeling system BehavePlus, and three Canadian systems: RedAPP, CanFIRE, and the Crown Fire Initiation and Spread system (CFIS).ResultsAll four modeling systems produced reasonable rate of spread predictions although the Canadian systems provided predictions slightly closer to the observed fire behavior. The Canadian fire behavior prediction modeling systems RedAPP and CanFIRE provided more accurate predictions of head fire intensity and fire type than BehavePlus or CFIS.ConclusionsThe most appropriate fire behavior modeling system for use in Alaskan black spruce ecosystems depends on what type of questions are being asked. For determining the rate of fire movement across a landscape, REDapp, CanFIRE, CFIS, or BehavePlus can all be expected to provide reasonably accurate estimates of rate of spread. If fire managers are interested in using predicted flame length or energy produced for informing decisions such as which firefighting tactics will be successful, or for evaluating the ecological impacts due to burning, then the Canadian fire modeling systems outperformed BehavePlus in this case study.