• Structural Engineering and Mechanics
• /
• v.59 no.5
• /
• pp.853-866
• /
• 2016

This paper examines a methodology for computing the probability of structural failure of reinforced concrete beams subjected to fire. The significant load variables considered are dead load, sustained live load and fire temperature. Resistance is expressed in terms of moment capacity with random variables taken as yield strength of steel, concrete class (or grade of concrete), beam width and depth. The flexural capacity is determined based on the design equations recommended in Indian standard IS456:2000. Simplified method named $500^{\circ}C$ isotherm method detailed in Eurocode 2 is incorporated for fire design. A transient thermal analysis is conducted using finite element software ANSYS$^{(R)}$ Release15. Reliability is evaluated from the initial state to 4h of fire exposure based on the first order reliability method (FORM). A procedure is coded in MATLAB for finding the reliability index. This procedure is validated with available literature. The effect of various parameters like effective cover, yield strength of steel, grade of concrete, distribution of reinforcement bars and aggregate type on reliability indices are studied. Parameters like effective cover of concrete, yield strength of steel has a significant effect on reliability of beams. Different failure modes like limit state of flexure and limit state of shear are checked.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2004.05a
• /
• pp.548-551
• /
• 2004

The main purpose of this study is to estimate the internal temperature of RC beam under fire. For this purpose, the finite difference method was used. In the previous studies, the structural behavior of fire damaged RC beams was investigated through experiments. The result was concluded that The high temperature affects the properties of concrete such as the elastic modulus, the compressive strength. The internal temperature Estimation of the concrete is helpful for understanding the structural behavior of fire damaged RC beams. Especially, high strength concrete has more spalling than normal strength one. So, this study is performed analysis of internal temperature of RC beam considering spalling.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2010.05a
• /
• pp.395-396
• /
• 2010

The purpose of this research is that development of fire-high resistance concrete for high-rise buildings is carried out with a test, which is for confirmation of fire-resistance capacity of 80MPa high-strength concrete. In this test, self-developed Polymix to confirm fire-resistance capacity of high-strength concrete in domestic high-rise buildings recently is applied.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
• /
• 2008.04a
• /
• pp.313-316
• /
• 2008

Nowadays, the use of high strength concrete has become increasingly popular. Thus, the theory of this study gives a definition of HSC mechanism through study factors of spalling occurrence of HSC and solutions of failure mechanism. During the fire goes on, building structure using HSC causes explosive spalling and finally it gets to the breaking of the structure down. As a result of this failure mechanism, it remains to be investigated to prevent from explosive spalling of HSC and needs to provide basic problems of HSC at high temperature.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.04a
• /
• pp.393-396
• /
• 2008

This paper presents the experimental results on the fire performance of high strength concrete(HSC) column made with different tie spacing. Three HSC columns measuring 305${\times}$305mm in cross section were prepared to evaluate the effect of tie spacing with 150, 210, 300mm, respectively. Compressive strength was 69MPa at test. As a result, the fire performance of HSC columns was greatly influenced by tie spacing. The fire resistance increases with decreasing the tie spacing.

• Steel and Composite Structures
• /
• v.50 no.3
• /
• pp.281-298
• /
• 2024

Stainless steel bolts (SSB) are increasingly utilized in bolted steel connections due to their good mechanical performance and excellent corrosion resistance. Fire accidents, which commonly occur in engineering scenarios, pose a significant threat to the safety of steel frames. The post-fire behavior of SSB has a significant influence on the structural integrity of steel frames, and neglecting the effect of temperature can lead to serious accidents in engineering. Therefore, it is important to evaluate the performance of SSB at elevated temperatures and their residual strength after a fire incident. To investigate the mechanical behavior of SSB after fire, 114 bolts with grades A4-70 and A4-80, manufactured from 316L austenitic stainless steel, were subjected to elevated temperatures ranging from 20℃ to 1200℃. Two different cooling methods commonly employed in engineering, namely cooling at ambient temperatures (air cooling) and cooling in water (water cooling), were used to cool the bolts. Tensile tests were performed to examine the influence of elevated temperatures and cooling methods on the mechanical behavior of SSB. The results indicate that the temperature does not significantly affect the Young's modulus and the ultimate strength of SSB. Up to 500℃, the yield strength increases with temperature, but this trend reverses when the temperature exceeds 500℃. In contrast, the ultimate strain shows the opposite trend. The strain hardening exponent is not significantly influenced by the temperature until it reaches 500℃. The cooling methods employed have an insignificant impact on the performance of SSB. When compared to high-strength bolts, 316L austenitic SSB demonstrate superior fire resistance. Design models for the post-fire mechanical behavior of 316L austenitic SSB, encompassing parameters such as the elasticity modulus, yield strength, ultimate strength, ultimate strain, and strain hardening exponent, are proposed, and a more precise stress-strain model is recommended to predict the mechanical behavior of 316L austenitic SSB after a fire incident.

• Steel and Composite Structures
• /
• v.33 no.1
• /
• pp.111-122
• /
• 2019

This paper presents an experimental work on the post-fire behavior of two kinds of innovative composite stub columns under eccentric compression. The partially precast steel reinforced concrete (PPSRC) column is composed of a precast outer-part cast using steel fiber reinforced reactive powder concrete (RPC) and a cast-in-place inner-part cast using conventional concrete. Based on the PPSRC column, the hollow precast steel reinforced concrete (HPSRC) column has a hollow column core. With the aim to investigate the post-fire performance of these composite columns, six stub column specimens, including three HPSRC stub columns and three PPSRC stub columns, were exposed to the ISO834 standard fire. Then, the cooling specimens and a control specimen unexposed to fire were eccentrically loaded to explore the residual capacity. The test parameters include the section shape, concrete strength of inner-part, eccentricity ratio and heating time. The test results indicated that the precast RPC shell could effectively confine the steel shape and longitudinal reinforcements after fire, and the PPSRC stub columns experienced lower core temperature in fire and exhibited higher post-fire residual strength as compared with the HPSRC stub columns due to the insulating effect of core concrete. The residual capacity increased with the increasing of inner concrete strength and with the decreasing of heating time and load eccentricity. Based on the test results, a FEA model was established to simulate the temperature field of test specimens, and the predicted results agreed well with the test results.

• Journal of the Korean Applied Science and Technology
• /
• v.11 no.1
• /
• pp.45-52
• /
• 1994

For the purpose of producing emulsified fire proofing agent for synthetic fibers, 2,3-dibromopropylmonoamido orthophosphate[DP-AOP] and bis(2,3-dibromopropyl)monoamidoorthophosphate[$(DP)_{2}AOP$] were synthesized, and their structures were identified by instrumental analysis, respectively. Using three kinds of emulsifiers, O/W emulsified fire proofing agents, DPF and DPDPF, were obtained corresponding to DP-AOP and $(DP)_{2}-AOP$, respectively. Various synthetic textiles were fire-retardant treated by prepared DPF and DPDPF, and fire retardancy and tearing strength of the resulting products were tested. The results showed that as the concentration of fire proofing agents increased, fire retardancy increased, but the tearing strength much decreased, where the tendencies of DPDPF were deeper than those of DPF. But, since the fire retardancy appeared favorable in the range of $10{\sim}20wt%$ of DPDPF, DPDPF is proven to be a fire proofing agent useful for various synthetic textiles.

• Advances in concrete construction
• /
• v.4 no.2
• /
• pp.89-105
• /
• 2016

The post - fire investigation is conducted on a fire-affected reinforced concrete shear wall building to ascertain the level of its strength degradation due to the fire incident. Fire incident took place in a three-storey building made of reinforced concrete shear wall and roof with operating floors made of steel beams and chequered plates. The usage of the building is to handle explosives. Elevated temperature during the fire is estimated to be $350^{\circ}C$ based on visual inspection. Destructive (core extraction) and non-destructive (rebound hammer and ultrasonic pulse velocity) tests are conducted to evaluate the concrete strength. X-ray diffraction (XRD) and Field Emission Scanning Electron Microscopy (FESEM) are used for analyzing micro structural changes of the concrete due to fire. Tests are conducted for concrete walls and roof slab on both burnt and unburnt locations. The analysis of test results reveals no significant degradation of the building after the fire which signifies that the structure can be used with full expectancy of performance for the remaining service life. This document can be used as a reference for future forensic investigations of similar fire affected concrete structures.

• Computers and Concrete
• /
• v.31 no.5
• /
• pp.371-384
• /
• 2023

Precast roofing systems employing prestressed elements often serve as smart structural solutions for the construction of industrial buildings. The precast concrete elements usually employed are highly engineered, and often consist in thin-walled members, characterised by a complex behaviour in fire. The present study was carried out after a fire event damaged a precast industrial building made with prestressed beam and roof elements, and non-prestressed curved barrel vault elements interposed in between the spaced roof elements. As a consequence of the exposure to the fire, the main elements were found standing, although some locally damaged and distorted, and the local collapse of few curved barrel vault elements was observed in one edge row only. In order to understand and interpret the observed structural performance of the roof system under fire, a full fire safety engineering process was carried out according to the following steps: (a) realistic temperature-time curves acting on the structural elements were simulated through computational fluid dynamics, (b) temperature distribution within the concrete elements was obtained with non-linear thermal analysis in variable regime, (c) strength and deformation of the concrete elements were checked with non-linear thermal-mechanical analysis. The analysis of the results allowed to identify the causes of the local collapses occurred, attributable to the distortion caused by temperature to the elements causing loss of support in early fire stage rather than to the material strength reduction due to the progressive exposure of the elements to fire. Finally, practical hints are provided to avoid such a phenomenon to occur when designing similar structures.