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Article
Publication date: 5 January 2022

Oluwamuyiwa Okunrounmu, Osama (Sam) Salem and George Hadjisophocleous

The fire resistance of timber structures is heavily dependent on the fire behaviour of the connections between its structural elements. The experimental study presented in this…

110

Abstract

Purpose

The fire resistance of timber structures is heavily dependent on the fire behaviour of the connections between its structural elements. The experimental study presented in this paper aimed to investigate the fire performance of glued-laminated timber beam connections reinforced perpendicular-to-wood grain with self-tapping screws (STS).

Design/methodology/approach

Two full-size fire experiments were conducted on glulam beam-end connections loaded in flexure bending. Two connection configurations, each utilizing four steel bolts arranged in two different patterns, were reinforced perpendicular to wood grain using STS. The bolt heads and nuts and the steel plate top and bottom edges were fire protected using wood plugs and strips, respectively. Each connection configuration was loaded to 100% of the ultimate design load of the weakest unreinforced configuration. The test assemblies were exposed to elevated temperatures that followed the CAN/ULC-S101 standard fire time–temperature curve.

Findings

The experimental results show that the influence of the STS was significant as it prevented the occurrence of wood splitting and row shear-out and as a result, increased the fire resistance time of the connections. The time to failure of both connection configurations exceeded the minimum fire resistance rating specified as 45 min for combustible construction in applicable building codes.

Originality/value

The experimental data show the effectiveness of a simple fire protection system (i.e. wood plugs and strips) along with the utilization of STS on the rotational behaviour, charring rate, fire resistance time and failure mode of the proposed hybrid mass timber beam-end connection configurations.

Details

Journal of Structural Fire Engineering, vol. 13 no. 4
Type: Research Article
ISSN: 2040-2317

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Article
Publication date: 5 June 2012

Lei Peng, George Hadjisophocleous, Jim Mehaffey and Mohammad Mohammad

This paper presents the results of a series of fire-resistance tests on bolted wood-steel-wood (WSW) connections and bolted steel-wood-steel (SWS) connections. In total, 16 WSW…

216

Abstract

This paper presents the results of a series of fire-resistance tests on bolted wood-steel-wood (WSW) connections and bolted steel-wood-steel (SWS) connections. In total, 16 WSW specimens and 6 SWS specimens were tested in accordance with the provisions of CAN/ULC-S101. All the specimens were subjected to a constant tensile load parallel to grain during the tests. The effects of load level, wood thickness, fastener diameter, number of fasteners, edge distance and protection were studied. The test results show that the fire-resistance ratings of all the tested WSW connections without protection were less than 45 minutes (a target rating for Canadian code compliance) and the fire-resistance ratings of all the tested SWS connections without protection were less than 25 minutes. Specimens with thicker wood side members were found to exhibit better fire resistances. Decreasing the load ratio increased the fire resistance. The test results on protected specimens show that the protection provided by a single-layer of 15.9 mm type X gypsum board increased the fire resistance by more than 30 minutes, whereas a double-layer of 12.7 mm Douglas fir plywood increased the fire resistance by 15 minutes. Furthermore, this research has generated necessary data and knowledge for the validation of a numerical heat transfer model and an analytical structural model.

Details

Journal of Structural Fire Engineering, vol. 3 no. 2
Type: Research Article
ISSN: 2040-2317

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Article
Publication date: 5 June 2012

Lei Peng, George Hadjisophocleous, Jim Mehaffey and Mohammad Mohammad

This paper presents models for calculating the fire resistance ratings of bolted timber connections based on fire-resistance test results carried out recently. In the first phase…

129

Abstract

This paper presents models for calculating the fire resistance ratings of bolted timber connections based on fire-resistance test results carried out recently. In the first phase of the work, a three-dimensional finite-element thermal model was employed to analyze heat transfer within bolted Wood-Steel-Wood (WSW) and Steel-Wood-Steel (SWS) connections. The thermal model was found to provide good predictions when comparing the calculated temperatures and residual cross-section dimensions of timber connections with the experiment results. In the next phase, an embedment strength reduction model was used to calculate the load-bearing capacity of WSW and SWS bolted connections by including the temperature profiles generated from the heat transfer model. Different relationships of wood embedding strength as a function of temperatures were used in the structural model. The comparisons with experimental results showed that Noren's approach seemed to predict fire resistances of bolted timber connections in good agreement. The structural model combined with the heat transfer model presented in this paper can be used for the parametric study of the performance of timber connections under fire exposure.

Details

Journal of Structural Fire Engineering, vol. 3 no. 2
Type: Research Article
ISSN: 2040-2317

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Article
Publication date: 17 September 2012

Osama Salem, George Hadjisophocleous and Ehab Zalok

This paper describes a series of full-scale tests performed in the fire research facilities of Carleton University, Ottawa, Canada. These tests are part of an experimental…

65

Abstract

This paper describes a series of full-scale tests performed in the fire research facilities of Carleton University, Ottawa, Canada. These tests are part of an experimental programme, whose objective is to investigate the structural performance of axially restrained tubular steel beams at elevated temperatures. The primary focus is to determine the effect of the beam end connections on the structural performance of the steel-frame assembly. Four unprotected steel-frame test assemblies, each composed of a hollow structural section (HSS) steel beam restrained between two HSS columns, were subjected to a standard fire while constantly loaded. The main parameters investigated were the end plate thickness and the degree of beam axial restraint. Two different end plate thicknesses were tested, 12.7 mm and 19.0 mm. The experimental results showed a considerable effect of the end plate thickness on the structural behaviour of the connection and the connected beam. Moreover, the fire tests have revealed different connection failure modes, such as excessive end plate deformations, column buckling, and bolts fracture.

Details

Journal of Structural Fire Engineering, vol. 3 no. 3
Type: Research Article
ISSN: 2040-2317

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Article
Publication date: 18 November 2014

Osama Salem, George Hadjisophocleous and Ehab Zalok

In this paper, experimental results of the structural fire behaviour of four large-scale steel frame test assemblies are presented. Test assemblies were made of HSS beams and…

45

Abstract

In this paper, experimental results of the structural fire behaviour of four large-scale steel frame test assemblies are presented. Test assemblies were made of HSS beams and columns connected together using an innovative extended end-plate moment connection configuration. Two different parameters were investigated, the connection end plate thickness and the degree of beam axial restraint. The fire performance of this beam-to-column configuration was compared to the behaviour of a commonly-used connection configuration with similar parameters and fire testing conditions. The newly-developed connection configuration behaved in a more flexible manner at elevated temperature than the regular configuration. In addition to improved constructability and pleasant appearance, the new connection configuration exhibits greater moment-carrying capacity and enhanced fire resistance characteristics.

Details

Journal of Structural Fire Engineering, vol. 5 no. 4
Type: Research Article
ISSN: 2040-2317

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Article
Publication date: 22 March 2013

George C. Bourantas, Eugenios D. Skouras, Vassilios C. Loukopoulos and George C. Nikiforidis

The purpose of this paper is to make a numerical study of natural convection of water‐based nanofluids in a square cavity when a discrete heat source is embedded on the bottom…

261

Abstract

Purpose

The purpose of this paper is to make a numerical study of natural convection of water‐based nanofluids in a square cavity when a discrete heat source is embedded on the bottom wall, applying a “nanofluid‐oriented” model for the calculation of the effective thermal conductivity (Xu‐Yu‐Zou‐Xu's model) and the effective dynamic viscosity (Jang‐Lee‐Hwang‐Choi's model). Another motivation is the numerical solution of the equations of the flow with a meshless method.

Design/methodology/approach

A meshless point collocation method with moving least squares (MLS) approximation is used. A test validation study of the numerical method takes place for pure water flow, as well for water/Al2O3 nanofluids. The influence of pertinent parameters such as Rayleigh number (Ra), the non‐uniform nanoparticle size keeping the mean nanoparticle diameter fixed, the volume fraction of nanoparticles and the location of heat source on the cooling performance are studied.

Findings

The presence of a discrete heat source, as well as the various thermal boundary conditions affects the characteristics of the nanofluid flow and heat transfer. When the ratio of minimum to maximum nanoparticle diameter is increased, the local Nusselt number is increased and the heat source temperature is decreased. The increase of solid volume fraction of nanoparticles causes the heat source maximum temperature to decrease and the Nusselt Number to increase.

Originality/value

The present study constitutes an original contribution to the nanofluid flow and heat transfer characteristics when a discrete heat source is presence. “Nanofluid‐oriented” models are used for the calculation of the effective thermal conductivity and dynamic viscosity.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 23 no. 2
Type: Research Article
ISSN: 0961-5539

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