Fire Tests of Concrete Members: An Improved Method for Estimating Thermal Restraint Forces

Issen, Lionel A; Gustaferro, Armand H.; Carlson, Clinton

doi:10.1520/stp44717s

Cited by 10 publications

(9 citation statements)

References 4 publications

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“…Fire tests of restrained floor slabs at the PCA furnace [7,8] have shown that the line of thrust moves from below the depth of the slab and towards the centroidal axis during the course of the fire.…”

Section: Position Of Line Of Thrust At the Supportsmentioning

confidence: 99%

“…The external thrust from the restraining structure replaces the function of the prestressing in the tendons and maintains the prestressing effect until some of the tendons reached temperatures which would have caused unrestrained beams to collapse. Issen et al [7] showed that almost any amount of restraint greatly enhanced the fire resistance of the slabs as they were able to support their loads considerably longer than for the simply supported condition. Based on these tests conducted at the Portland Cement Association (PCA), a step-by-step method was developed to determine the amount of thrust required to prevent collapse of the floor system, and the required stiffness of the surrounding structure to provide that level of restraint [11].…”

Section: Past Researchmentioning

confidence: 99%

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Restraint of fire‐exposed concrete floor systems

2004

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SUMMARYThis paper describes the numerical analyses of restrained concrete floor slabs exposed to fire. The analyses of the slabs were carried out with the SAFIR finite element program considering a 200 mm thick slab, spanning 5 m between two end supports. The slabs were exposed to the ISO standard fire for up to 4 h and were analysed with pinned and rotationally restrained supports. Different heights of the line of thrust at the supports and different levels of axial restraint were also investigated. The analyses show that fully restrained pin-supported slabs can survive the 4 h ISO fire without collapse if the position of the line of thrust is located near the soffit of the slab. If the position of the line of thrust is located much above the soffit of the slab, the slabs will rapidly undergo large deformations and sag into a catenary, imposing axial tensile forces at the supports. The analyses have shown that even if the line of thrust is located close to the soffit, the slab can still deform into a catenary if there is insufficient horizontal axial restraint. In this study, rotationally restrained slabs experience much smaller vertical deflections than pin-supported slabs when exposed to fires. Rotationally restrained slabs with low levels of horizontal restraint do not collapse, due to the beneficial effects of moment redistribution. However, high levels of horizontal restraint can be detrimental, causing slabs to collapse at advanced stages of the fire.

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Section: Position Of Line Of Thrust At the Supportsmentioning

confidence: 99%

Section: Past Researchmentioning

confidence: 99%

Restraint of fire‐exposed concrete floor systems

2004

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“…Information on T and d T is based on experimental research by Issen, Gustaferro and Carlson (1970). The experimental program consisted of 40 standard fire resistance tests conducted by the Portland Cement Association.…”

Section: Commentary/appendixmentioning

confidence: 99%

Best practice guidelines for structural fire resistance design of concrete and steel buildings

2010

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This document is intended to provide practicing engineers and building code officials with a technical resource that contains the current "best practice" for fire-resistant design of concrete and steel structures. The report provides a review of existing U.S. and international guidelines and design standards, which use approaches that range from simple prescriptive methods to sophisticated software programs with advanced methods of analysis under a wide range of realistic fire conditions. Basic concepts of risk-informed decision making for mitigating fire risk, and a general framework for assessing fire risk to building construction and for developing structural design requirements for fire conditions are described. Current best knowledge in thermal and mechanical properties and behaviors of normal strength concrete, high strength concrete, structural steel, and several major groups of common fire protection materials at elevated temperatures, which are necessary for performance-based engineering calculation, are presented. Modern fire-resistant design methodologies for concrete and steel structures are discussed, including methods based on standard fire tests as well as performance-based engineering analysis methods that involve heat transfer and structural analysis at elevated temperatures.This report is not intended to provide step-by-step design procedures. Rather, it provides general guidance on the approaches to, and practical aspects of, implementing a fire-resistant design approach for concrete and steel buildings. The guidance includes key concepts and examples for identifying performance objectives, conducting risk analyses, selecting design fire scenarios and fire exposure curves, and implementing heat transfer and structural response analyses for the structural fire-resistant design of concrete and steel structures.The best practice guidelines document is intended to be a technical resource that provides the most complete information for structural fire-resistant design at present. The document is a nonconsensus, non-mandatory document and, as such, it does not represent a minimum standard of care.

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“…Nevertheless, the thrust is generally great enough to increase the fire resistance significantly. In most fire tests of restrained assemblies, the fire resistance is determined by temperature rise of the unexposed surface rather than by structural considerations, even though the steel temperatures often exceed 800°C (1500°F) (Abrams et al 1976, Lin and Abrams 1983, Issen et al 1970.…”

Section: Fire Resistance Of Floor Slabs and Roofs Subjected To Thermalmentioning

confidence: 99%

Structural Fire Protection

Lie¹

1992

131

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This manual, Structural Fire Protection: Manual of Practice (Manual and Report# 78), is intended to provide a basis for the development of new standards for the calculation of the fire resistance of structural members. It provides information on current techniques and developments to improve fire safety in buildings. While it deals mainly with structural fire safety, related subjects are also discussed. The manual consists of two parts.The material in Part 1, which consists of three chapters, is mainly descriptive. Chapter 1 deals with various aspects related to structural fire protection, including building codes and the role of structural fire protection. Chapter 2 discusses the development of fire in enclosures and the effect of fire on the behavior of concrete, steel, and wood, including the properties of these materials at elevated temperatures. Chapter 3 describes methods for the calculation of the fire resistance of various structural members. Part 2, which consists of Chapters 4 and 5, deals with the development of fire and the calculation of fire resistance using mathematical models, respectively. It is hoped that, in addition to providing a basis for new standards, this manual will also be useful to architects, engineers, building officials and students in any branch concerned with structural fire safety.Authorization to photocopy material for internal or personal use under circumstances not falling within the fair use provisions of the

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Fire Tests of Concrete Members: An Improved Method for Estimating Thermal Restraint Forces

Cited by 10 publications

References 4 publications

Restraint of fire‐exposed concrete floor systems

Restraint of fire‐exposed concrete floor systems

Best practice guidelines for structural fire resistance design of concrete and steel buildings

Structural Fire Protection

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