Response of toe-nailed, roof-to-wall connections to extreme wind loads in a full-scale, timber-framed, hip roof

Published Date
November 2013, Vol.56:1474–1483, doi:10.1016/j.engstruct.2013.07.001

Author 

David J. Henderson ^a,b

Murray J. Morrison ^a,c

Gregory A. Kopp ^a,,,

aBoundary Layer Wind Tunnel Laboratory, Faculty of Engineering, University of Western Ontario, London, ON N6A 5B9, Canada

bCyclone Testing Station, James Cook University, Townsville, Queensland 4811, Australia

cInsurance Institute for Business & Home Safety, Richburg, SC 29729, USA

Received 27 November 2012. Revised 24 April 2013. Accepted 1 July 2013. Available online 17 August 2013.

Highlights

• A full-scale hip roof was tested using spatially and temporally varying wind loads.
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  Influence functions changed when there is withdrawal of toe-nailed connections.
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  Load sharing increases with nail withdrawal, increasing a structure’s resilience.
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  Regular trusses with toe-nails share load over 6–8 connections, jack trusses over 3.

Abstract

A full-scale, timber-framed, truss, hip roof was subjected to simulated wind loads. Spatially and temporally varying pressures were applied using an array of 58 Pressure Loading Actuators, together with air-boxes covering all roof surfaces. Load cells were incorporated at the top of the wall frame, just below the top plate, to measure the reactions at the toe-nailed roof-to-wall connections. Changes in influence functions and load sharing between adjacent trusses were observed to occur during withdrawal (slip) of the toe-nail connections caused by large magnitude, short duration peak pressures. Even for relatively small displacements, it was observed that the effective tributary area is substantially increased by the incremental withdrawals. This acts to increase the resilience of the roof by allowing more limber and/or more highly loaded connections to transfer loads to stiffer and/or less highly loaded connections. Influence functions, measured both prior to and following damage, were able to predict this behaviour.

Keywords

Wind loads

Wind damage

Wood-frame houses

Influence coefficients

Roof-to-wall connections

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 Table 1

Table 1.

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  Corresponding author. Tel.: +1 519 661 3338.

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