@article {bnh-4148, title = {Testing of simulated flood effect on the strength of selected building components}, number = {334}, year = {2017}, month = {06/2017}, institution = {Bushfire and Natural Hazards CRC}, address = {Melbourne}, abstract = {

This report presents the results of tests conducted to ascertain the resilience of selected building components to floodwater exposure. The experimental test programme was part of the Bushfire and Natural Hazards Collaborative Research Centre (BNHCRC) project entitled {\textquotedblleft}Cost-effective mitigation strategy development for flood prone buildings{\textquotedblright}.

The motivation for this project arises from the experience and observations made during the recent flooding in Australia in 2011 and 2013, which caused widespread devastation in Queensland. The objective of the project is to address the vulnerability of existing residential building stock in Australian floodplains and is targeted at assessing cost-effective mitigation strategies to reduce the vulnerability.

Geoscience Australia as the lead researcher for the project selected the Cyclone Testing Station at James Cook University in Townville, Queensland, to conduct the experimental tests. These tests aimed to address knowledge gaps in the areas of strength and durability implications of selected components of a typical brick veneer slab-on-grade house due to immersion.

The experimental programme was developed in consultation with insurance industry loss assessors from two major companies and was scoped in recognition of the available budget. The objective of the testing was to identify whether the selected components remain serviceable following inundation and subsequent drying or whether replacement was required.

The experimental programme examined the resistance to inundation of three common building components as outlined below. For each component, a number of samples were tested to attempt to provide some understanding of the variation of resistance. For each component some specimens were tested dry without wetting and some were tested after drying following inundation. For Component 3, some specimens were also tested wet immediately after inundation.

The results of the tests showed that flooding did not have any significant effect on the pull-out strength of the bond of the ceramic floor and wall tiles to their substrate, nor on the racking strength of the OSB wall sheet bracing. There was a nominal strength reduction of 10\% for the HDF wall sheet bracing when tested after wetting and drying cycle.

However, there was a significant reduction (~46\%) in load carrying capacity of the timber joists when tested in the wet condition. These results suggest that the samples whilst in the wet stage may be compromised due to reduced strength capacity and stiffness. However, if allowed to dry then the specimen could recover to nominally 96\% of average strength capacity and stiffness. Moreover, it was observed that the moisture content level after the test returned close to pre-inundation level within a week and therefore contributed to recover the strength and stiffness.

The results of the testing will inform recommendations on mitigation measures within the BNHCRC flood project. The results will also inform the selection of building materials for new construction in flood-prone areas.

}, issn = {334}, author = {Maqsood, T and Martin Wehner and Mark Edwards and Simon Ingham and David Henderson} } @article {bnh-4227, title = {Tropical Cyclone Debbie: damage to buildings in the Whitsunday Region}, number = {63}, year = {2017}, month = {06/2017}, institution = {James Cook University}, address = {Townsville}, abstract = {

Tropical Cyclone Debbie (TC Debbie) was classified by the Bureau of Meteorology (BoM) as a Category 4 cyclone and crossed the Queensland coast north east of Airlie Beach around midday on Tuesday 28 March 2017.

Before the event, the Cyclone Testing Station (CTS) deployed six mobile anemometers (SWIRLnet) in the area between Ayr and Proserpine. After the event, CTS teams investigated the performance of houses; larger residential structures such as apartments, strata properties and resort accommodation; commercial and public buildings; and sheds. The study area included the communities of Bowen, Proserpine, Airlie Beach, Hamilton Island, Dingo Beach, Wilson{\textquoteright}s Beach and Conway Beach. A wind field was developed using CTS and BoM anemometer data and showed that buildings within the study area experienced wind speeds lower than their relevant design wind speed.

CTS teams assessed the causes of damage to buildings from wind, wind-driven rainwater and storm surge. Inadequate tie-down details between battens and rafters or trusses, and between the roof structure and walls caused many of the structural failures in buildings constructed before the 1980s. Tie-down connections between roof structure and walls that had been inappropriately detailed also failed on some recently constructed buildings. Connections between verandah beams and posts on some buildings with larger verandahs also failed. \ 

This study confirmed the findings of previous damage investigations concerning the vulnerability of: windows with inadequate fixings, window and door furniture; poorly fixed flashings, gutters and soffit linings; large access doors that had not been strengthened so that they complied with AS/NZS4505; lightweight sheds; and fences.

Many occupants of newer buildings reported significant damage from wind-driven rain entering through windows and doors or under flashings even though there was no structural damage to the building. Many people reported that they mopped up water in front of windward wall windows during periods of maximum winds, which exposed them to risk of injury. Further research is required to improve performance of building elements that leak during high winds.

The storm tide generated during TC Debbie was lower than predicted because the cyclone crossed the coast after high tide. Lower-lying buildings in Wilson Beach were inundated to a height of up to 1.1 m causing damage to wall linings, built-in cupboards, floor coverings and contents. In some cases, wave action broke cladding elements and windows. Wave action and scour undercut footings in some buildings on Hamilton Island and Wilson Beach.\ 

The report provides recommendations to improve the performance of building structure and cladding systems including: adequate detailing for roof to wall connections; improved fixing of flashings, retrofitting options for older buildings; improvements in windows and door furniture under repeated wind loads; and revision of storm surge guidelines.

}, isbn = {978-0-9954470-4-2}, issn = {63}, url = {https://www.jcu.edu.au/__data/assets/pdf_file/0009/461178/TC-Debbie-report.pdf}, author = {Boughton, Geoffrey N. and Falck, D. J. and David Henderson and D. J. Smith and Korah Parackal and Thomas Kloetzke and M. S. Mason and Humphreys, M and Navaratnam, S and Bodhinayake, G and Simon Ingham and John Ginger} }