Architectural Considerations in the Seismic Retrofit of Unreinforced Masonry Heritage Buildings in New Zealand

Abstract

Unreinforced masonry (URM) buildings make up a significant proportion of heritage building stock in New Zealand. Many of these have historic value and contribute greatly to the character of cities, but have numerous flaws which make them seismically dangerous. Legislation now requires action on buildings below a certain strength threshold, and seismic retrofit is necessary to conserve them. The aims of this thesis are to: Explain the history and theory which have formed current attitudes to conservation. Explain the important architectural considerations when undertaking a retrofit. Analyse strengthening methods and comment on their impact and appropriateness. Devise a method to reconcile seismic strengthening and heritage ideals. If insufficient consideration is given to the historic and architectural qualities of URM buildings, a retrofit may visually damage them or remove important historic material. The extent, type, and placement of any strengthening work need careful thought. The goal is to minimise adverse effects on the fabric of the building and on the spaces in and around it. There are several principles which must be given priority: Only add as much as is necessary, and change as little as possible. Strengthening work should be reversible, and recognizable as new. One should always gain knowledge of the important characteristics of a building. Any strengthening work should respect the integrity and character of a heritage building. If these principles are applied with creativity and artfulness in the spirit in which they were intended, a strengthening solution can be reached which works with the existing material to complement the architectural character with a minimum of impact. A solution that achieves these things can be considered to be a successful and effective intervention.