Fire testing of structural elements

A research report submitted in partial fulfilment of the requirements for the degree of Master of Science in Engineering to the Faculty of Engineering and the Built Environment, School of Civil and Environmental Engineering, University of the Witwatersrand, Johannesburg, 2018This report investigates the heating conditions required by various international standards in order to conduct a standard fire test on building elements. This investigation also aims to obtain an understanding of the various methods used in order to conduct standard fire tests, and the various criteria that building elements are required to adhere to during a fire. The outcome of the investigations conducted here is an apparatus and a testing method that can be used in future investigations to conduct full scale fire tests on building elements while complying with international standards. Various tests are conducted with the use of different methods and the viability and repeatability of each method is assessed. Various methods exist in international standards that propose standard heating conditions and criteria upon which the performance of a building element in a fire is assessed. The most common temperature – time relationship used in fire tests is that of the standard temperature – time curve seen in the British Standard: BS 476 and the South African National Standard: SANS 10177. Another widely used temperature – time relationship is that seen in the American Society for Testing and Materials standard: ASTM E119. Eurocode 1 proposes a natural / parametric compartment fire model that allows one to establish a temperature – time curve specific to a particular enclosure. By conducting a fire test with temperatures regulated according to a specified temperature – time curve, one may determine the fire resistance rating of a building element. The fire resistance rating is the time period for which an element is able to adhere to certain criteria during a fire. Through a series of preliminary natural fire tests, shortfalls to the standard temperature – time curve were observed when the natural fire did not behave in a manner similar to the unnatural heating requirements described by the standardized time - temperature curve; as these temperatures will rarely be encountered in a building fire. By conducting preliminary tests with the use of flammable liquids, however, such as petroleum and diesel, the furnace temperature requirements of SANS 10177 were able to be replicated for a period of 20 to 30 minutes. A test was also conducted with the use of liquefied Petroleum Gas as the fuel type, however, this fuel did not produce a large enough flame for the purpose of achieving the desired furnace temperature. Through a series of preliminary experiments with the use of flammable liquids, a method of conducting a fire test according to SANS 10177 was developed with the use of a prototype flammable liquid burner capable of controlling furnace temperature with respect to time. A testing sheet was also proposed that can serve as a generic sheet containing the necessary instructions to conduct a fire test. The test sheet can be used to record all necessary data and observations from the test. The next series of tests conducted after the preliminary tests aimed to replicate the requirements of international standards, and to test the repeatability of the method used. These tests were conducted with the use of a diesel burner that was fabricated in such a way as to overcome shortfalls noted in the preliminary tests. The burner made use of a diesel – air mixture, to initiate a flame inside the furnace that could be controlled as necessary. An average correlation with respect to the SANS10177 time - temperature curve of 0.944 was achieved for all 8 diesel burner tests conducted. It was also clear that testing procedures improved significantly with experience as results began to correlate closer with SANS requirements for each subsequent test. Test 8 temperatures fell within the allowable temperature tolerances for 91 percent of the testing time and were also within the allowable range with respect to the ASTM E119 heating requirements. The diesel burner used in the final tests is a suitable burner to be used when conducting fire tests according to SANS 10177, BS476, and ASTM E119 requirements. A high level of repeatability was achieved in all 8 tests as all results fell within the specified temperature range. The size of the furnace used in all tests conducted in this study however does not meet the minimum dimensional requirements of any of the international standards. In order to conduct fire tests according to SANS 10177 a full sized furnace will need to be constructed using the principles and apparatus outlined in this report.XL201

Fuselage ventilation due to wind flow about a postcrash aircraft

Postcrash aircraft fuselage fire development, dependent on the internal and external fluid dynamics is discussed. The natural ventilation rate, a major factor in the internal flow patterns and fire development is reviewed. The flow about the fuselage as affected by the wind and external fire is studied. An analysis was performend which estimated the rates of ventilation produced by the wind for a limited idealized environmental configuration. The simulation utilizes the empirical pressure coefficient distribution of an infinite circular cylinder near a wall with its boundary later flow to represent the atmospheric boundary layer. The resulting maximum ventilation rate for two door size openings, with varying circumferential location in a common 10 mph wind was an order of magnitude greater than the forced ventilation specified in full scale fire testing. The parameter discussed are: (1) fuselage size and shape, (2) fuselage orientation and proximity to the ground, (3) fuselage-openings size and location, (4) wind speed and direction, and (5) induced flow of the external fire plume is recommended. The fire testing should be conducted to a maximum ventilation rate at least an order of magnitude greater than the inflight air conditioning rates

A3 Subscale Rocket Hot Fire Testing

This paper gives a description of the methodology and results of J2-X Subscale Simulator (JSS) hot fire testing supporting the A3 Subscale Diffuser Test (SDT) project at the E3 test facility at Stennis Space Center, MS (SSC). The A3 subscale diffuser is a geometrically accurate scale model of the A3 altitude simulating rocket test facility. This paper focuses on the methods used to operate the facility and obtain the data to support the aerodynamic verification of the A3 rocket diffuser design and experimental data quantifying the heat flux throughout the facility. The JSS was operated at both 80% and 100% power levels and at gimbal angle from 0 to 7 degrees to verify the simulated altitude produced by the rocket-rocket diffuser combination. This was done with various secondary GN purge loads to quantify the pumping performance of the rocket diffuser. Also, special tests were conducted to obtain detailed heat flux measurements in the rocket diffuser at various gimbal angles and in the facility elbow where the flow turns from vertical to horizontal upstream of the 2nd stage steam ejector

Suppression of Subsynchronous Vibration in the SSME HPFTP

Space Shuttle Main Engine (SSME) High Pressure Fuel Turbopump (HPFTP) hot-fire dynamic data evaluation and rotordynamic analysis both confirm that two of the most significant turbopump attributes in determining susceptibility to subsynchronous vibration are impeller interstage seal configuration and rotor sideload resulting from turbine turnaround duct configuration and hot gas manifold. Recent hot-fire testing has provided promising indications that the incorporation of roughened damping seals at the impeller interstages may further increase the stability margin of this machine. A summary of the analysis which led to the conclusion that roughened seals would enhance the stability margin is presented along with a correlation of the analysis with recent test data

Dual nozzle aerodynamic and cooling analysis study

Geometric, aerodynamic flow field, performance prediction, and heat transfer analyses are considered for two advanced chamber nozzle concepts applicable to Earth-to-orbit engine systems. Topics covered include improvements to the dual throat aerodynamic and performance prediction program; geometric and flow field analyses of the dual expander concept; heat transfer analysis of both concepts, and engineering analysis of data from the NASA/MSFC hot-fire testing of a dual throat thruster model thrust chamber assembly. Preliminary results obtained are presented in graphs

Swirl coaxial injector element characterization for booster engines

Recent hot fire testing at the Marshall Space Flight Center (MSFC) has indicated the swirl-coaxial element to be a viable candidate for the STBE injector. Plans are to test the current 40K lbf thrust injector at the higher chamber pressure and colder fuel temperature which are anticipated for STBE. A cold flow program to characterize the swirl coax element over a range of operating points was conducted. The results are presented and compared to the hot fire data. Predictions for compatibility, performance and stability are then presented for the uprated test conditions

Hot fire fatigue testing results for the compliant combustion chamber

A hydrogen-oxygen subscale rocket combustion chamber was designed incorporating an advanced design concept to reduce strain and increase life. The design permits unrestrained thermal expansion of a circumferential direction and, thereby, provides structural compliance during the thermal cycling of hot-fire testing. The chamber was built and test fired at a chamber pressure of 4137 kN/sq m (600 psia) and a hydrogen-oxygen mixture ratio of 6.0. Compared with a conventional milled-channel configuration, the new structurally compliant chamber had a 134 or 287 percent increase in fatigue life, depending on the life predicted for the conventional configuration

Fire Safety of Mass timber Buildings with CLT in USA

Multistory buildings using mass timber and cross-laminated timber (CLT) as the primary structural elements are being planned and constructed globally, with interest starting to gather momentum in the United States. Model building codes in the United States limit timber construction to a building height of 85 ft (25.9 m) because of concerns over fire safety and structural performance. Up to 85 ft, the mass timber can be exposed. Architects and developers in the United States are pushing boundaries, requesting mass timber structures are constructed as high-rises and that load-bearing mass timber such as CLT be exposed and not fully protected. This provides an opportunity for the application of recent fire research and fire testing on exposed CLT to be applied, and existing methods of analyzing the impact of fire on engineered timber structures to be developed further. Fire testing has shown that exposing large areas of CLT significantly impacts the heat release rate and fire duration. This article provides an overview of the code requirements for timber construction in the United States, provides methods for building approval for a high-rise timber structure, and summarizes recent CLT compartment fire testing that is informing the fire engineering process. Methods for solutions are also discussed

Consolidated fire testing – a framework for thermomechanical modelling

Consolidated testing facilitates the investigation of the global behavior of structures subjected to fire and therefore may become increasingly important in structural fire engineering. In order to develop a consolidated testing procedure that meets the requirements arising from structural fire engineering and considers thermal strains, thermal creep effects as well as strength and stiffness degradation, a consolidated testing benchmark problem is elaborated. The benchmark problem allows to perform coupled experimental and numerical tests that can be verified by pure physical testing. Furthermore, a framework for a consolidated test setup is developed, including a tangent stiffness update algorithm. Two preliminary tests at ambient temperature show the eligibility of the consolidated testing framework and are presented in this paper

Development of Hydrocarbon Fire Testing for Offshore Application

The use of glass fibre reinforced polymer (GFRP) in offshore oil and gas platforms has been on a rise in the recent decades mainly due to its advantages such as good strength to weight ratio, corrosive resistance and etc. Issues such as strength, durability as well as serviceability are the main issues as well. In the concern of fire testing qualification requirement set by the US Coast Guard, glass fibre reinforced polymer (GFRP) was tested under cellulosic fire which does not portray the real offshore platforms burning condition (ASTM E-119). It should instead be tested with hydrocarbon fire which simulates a higher spreading rate and a higher temperature compared to that of cellulosic fire