@article {bnh-3804, title = {Final report: seismic retrofit tests of URM cavity walls}, number = {249}, year = {2017}, month = {07/2017}, institution = {Bushfire and Natural Hazards CRC}, address = {Melbourne}, abstract = {

University of Adelaide researchers were engaged by Bushfire and Natural Hazards CRC to undertake an experimental campaign aiming to identify and develop seismic retrofit methods for out-of-plane loaded cavity walls. The research is a part of a broader project titled "Cost-effective mitigation strategy development for building related earthquake risk". This report presents the details of the tested cavity walls, trialed retrofitted schemes, obtained results, and discussion. The report concludes with recommendations on the seismic retrofit of this type of wall construction.

A review of the masonry literature suggested that retrofit methods have already been developed and widely researched for solid unreinforced masonry (URM) walls, but that the methods cannot be readily applied to cavity walls due to the cyclic nature of the seismic loads and the limited access to the cavity gap. The methods generally require access to both faces of the wall to attach fiber-reinforced-polymer (FRP) strips to masonry.

The broad retrofit concept for cavity walls was conceived to be using NSM FRP technique on the exposed surfaces of the cavity wall skins, e.g. to one face of each wall skin, but with the provision that the wall ties be verified/upgraded to maintain the cavity gap. For this purpose, 6 different alternatives of cavity structure were investigated. Two options involved the use of standard wall metal ties with different densities. Two other options included the use of proprietary helical mechanical anchors with different densities, and finally two configurations of expanding foam was used to partly or wholly fill the cavity gap. All of the FRP strips were near-surface-mounted (NSM).

It was found that with NSM FRP retrofit, the existing wall ties may be sufficient to maintain cavity gap depending on the location of the wall in Australia. For walls in regions with relatively higher seismic hazard, helical anchors can be added, and the anchor spacing can be proportional to seismic hazard but need not be less than 260 mm, i.e. every 3rd course.

}, issn = {249}, author = {Hossein Derakhshan and Wade Lucas and Phillip Visintin and Michael Griffith} }