MASONRY TODAY AND TOMORROW 11 - 14 February, 2018 SYDNEY AUSTRALIA www.10amc.com SECURING OF UNREINFORCED MASONRY PARAPETS AND FACADES – FROM FUNDAMENTAL RESEARCH TO NATIONAL POLICY J.M. Ingham1, D. Dizhur2, M. Giaretton3, K.Q. Walsh4, H. Derakhshan5, R. Jafarzadeh6, M.C. Griffith7 and M.J. Masia8 1 Professor, Department of Civil and Environmental Engineering, The University of Auckland, Auckland 1023, New Zealand, [email protected] 2 Lecturer, Department of Civil and Environmental Engineering, The University of Auckland, Auckland 1023, New Zealand, [email protected] 3 Post-doctoral Researcher, Department of Civil and Environmental Engineering, The University of Auckland, Auckland 1023, New Zealand, [email protected] 4 Assistant Professor of Practice, Department of Civil & Environmental Engineering & Earth Sciences, University of Notre Dame, Indiana, United States; Senior Structural Engineer, Frost Engineering and Consulting, Mishawaka, Indiana, United States, [email protected] 5 Post-doctoral Researcher, School of Civil, Environmental and Mining Engineering, The University of Adelaide, Adelaide, SA 5005, Australia, [email protected] 6 Engineer, Auckland Council, Private Bag 92300, Victoria Street West, Auckland 1142, New Zealand, [email protected] 7 Professor, School of Civil, Environmental and Mining Engineering, The University of Adelaide, Adelaide, SA 5005, Australia, [email protected] 8 Associate Professor, Centre for Infrastructure Performance and Reliability, The University of Newcastle, Callaghan, NSW 2308, Australia, [email protected] The study of unreinforced masonry buildings and their performance in earthquakes is a topic that has led to strong Australasian collaboration amongst masonry researchers over the last decade, that has resulted in significant advances in knowledge and empirical evidence, comprehensive capture of post-earthquake ‘perishable data’, the development of new numerical assessment and design procedures, and the training of a new generation of masonry researchers. These efforts have significantly influenced national policy and professional practice, particularly in New Zealand. A chronology of these events is reported. Keywords: Unreinforced masonry, parapet, façade, legislation 1 INTRODUCTION Since the time of European settlement, New Zealand has a sustained history of unreinforced masonry (URM) buildings having performed poorly in large earthquakes, with several notable examples from the mid-1800s and early 1900s shown in Figure 1. Although less seismically active, Australia also has a notable history of earthquakes having caused damage to URM buildings (see Figure 2). From the mid-1970s through until today research has been undertaken in New Zealand and Australia that has assisted in framing national policy and practice on the seismic assessment and improvement of URM buildings, with some of this research reviewed herein. (a) 1848 MW 7.8 Marlborough earthquake (b) 1929 MW 7.8 Murchison earthquake (source: http://www.geonet.org.nz/earthquake/historic- (source: http://mp.natlib.govt.nz/detail/?id=42847&recordNum=4& earthquakes/top-nz/quake-01.html) q=earthquake&f=tapuhigroupref%24PAColl-3051&s=a&l=mi) Figure 1: The poor performance of unreinforced masonry buildings in past New Zealand earthquakes (magnitude data sourced from: https://en.wikipedia.org/wiki/List_of_earthquakes_in_New_Zealand) 2 (c) 1901 ML 6.8 Cheviot earthquake (d) 1931 MW 7.8 Hawke’s Bay (Source: http://christchurchcitylibraries.com/heritage/photos/disc5/img earthquake 0067.asp) (Source: http://www.teara.govt.nz/en/historic- earthquakes/8/1) Figure FRQWLQXHG : The poor performance of unreinforced masonry buildings in past New Zealand earthquakes (magnitude data sourced from: https://en.wikipedia.org/wiki/ List_of_earthquakes_in_New_Zealand) (a) 1989 ML 5.6 Newcastle, NSW (b) 2010 MW 5.2 Kalgoorlie- earthquake Boulder, WA earthquake Figure : The poor performance of unreinforced masonry buildings in past Australian earthquakes (magnitude data sourced from https://en.wikipedia.org/wiki/1989_Newcastle_earthquake and https://en.wikipedia.org/wiki/2010_Kalgoorlie-Boulder_earthquake) HONOURING THE CONTRIBUTIONS OF PROFESSOR NIGEL PRIESTLEY Between 1974 and 1985 Professor Nigel Priestley undertook several landmark studies in New Zealand on clay brick masonry, first at the Ministry of Works Central Laboratories and then at the University of Canterbury, commencing with an investigation of reinforced clay brick masonry walls (Priestley and Bridgeman 1974) in collaboration with the New Zealand Pottery and Ceramics Research Association. In 1979 Nigel again collaborated with researchers from the New Zealand Pottery and Ceramics Research Association to investigate the dynamic performance of brick masonry veneer panels (Priestley et al. 1979). The 1979 study was motivated by the poor 3 reputation of unreinforced masonry veneers when subjected to earthquakes, with much of this reputation being attributed to the failure of brick masonry facades and walls during the 1931 Napier and the 1968 Inangahua earthquakes. Seven unreinforced and two reinforced clay brick masonry veneer walls tied to conventional timber-frame backings were subjected to out-of-plane sinusoidal accelerations in the appropriate frequency range imitating earthquake loading, see Figure 3, where the stud spacing, veneer-tie type and the initial distribution of pre-formed cracking were the main variables. Out-of-plane face loading was specifically considered because the draft Code of Practice for light timber frame construction required the entire in-plane load demands to be carried by the timber frame bracing to which the masonry veneer wall is fixed. From this testing, it was concluded that when unreinforced masonry veneers were built to the specifications prescribed in the draft Code of Practice, acceptable response could be expected for earthquake loading levels in excess of those expected for the highest seismic zone in New Zealand. Furthermore, it was found that pre- formed horizontal or diagonal panel cracking had little or no apparent influence on the ultimate performance of the veneers. Figure : Test set-up for out-of-plane dynamic loading of clay brick masonry veneer walls (Priestley et al. 1979) In 1985 Nigel added a new dimension to his masonry research by investigating the out-of-plane response of unreinforced masonry (URM) walls (Priestley 1985). This research was focused on assessing the earthquake characteristics of existing URM walls, rather than the design of new reinforced masonry buildings, and Nigel commented that: “the response of unreinforced masonry walls to out-of-plane (face load) seismic excitation is one of the most complex and ill-understood areas of seismic analysis”. It is noted that the elastic analysis technique that was commonly applied at that time was focused on masonry stress levels that were “rather insignificant for unreinforced masonry”, resulting in 4 excessively conservative results, and that the seismic capacity of URM walls responding out-of- plane is instead governed by stability and energy considerations. Load paths within unreinforced masonry buildings were discussed, as was the influence of flexible diaphragms. The conditions at wall failure were presented in terms of displacements necessary to cause instability, see Figure 4, and it was recommended that dynamic testing and corresponding analysis be undertaken to further refine the presented methodology for assessment. It was noted that the walls in the upper levels of unreinforced masonry buildings were likely to be most critical, and that adequately securing the walls to diaphragms is an essential step for ensuring satisfactory earthquake performance of face- loaded URM walls. Figure : Consideration of seismic loading and out-of-plane wall stability for unreinforced masonry buildings with flexible diaphragms (Priestley, 1985) SEISMIC RETROFIT SOLUTIONS PROJECT Between the mid-1980s and 2004 there was a period in New Zealand of roughly two decades where little formal research attention was devoted to the seismic performance of URM buildings. However, in 2004 researchers at the University of Auckland commenced a 6-year study on the earthquake response of URM buildings, with the ambitious goal of developing methodologies for detailed seismic assessment and retrofit. The study began with efforts to count and architecturally characterise the national inventory of URM buildings (Russell and Ingham, 2010), gain an understanding of representative material characteristics for the existing New Zealand URM building stock (Almesfer et al. 2014; Lumantarna et al. 2014a,b; Dizhur et al. 2016, 2017), do structural testing on URM sub-assemblages (Derakhshan et al. 2103; Dizhur and Ingham 2103; Dizhur et al. 2013; Lin 2016; Mahmood and Ingham 2011; Ismail et al. 2011; Ismail and Ingham 2012a,b, 2016; Wilson et al. 2014a) and undertake both lab and field studies on larger test specimens representative of real buildings (Giongo et al. 2013, 2015; Wilson et al. 2014b; Knox et al. 2017; Oyarzo-Vera et al. 2017). These efforts concluded in September 2010 with the release of a draft guidance document for professional engineers on how to undertake detailed seismic assessment and improvement of URM buildings. 5 THE CANTERBURY EARTHQUAKE SEQUENCE The first event in the Canterbury earthquake sequence occurred on 4 September 2010. Researchers from the University Auckland collaborated with colleagues from Adelaide and Newcastle