Establishing the Transverse Load Capacity of a Timber-framed Classroom Block

Abstract

In 2013, longitudinal testing of single storey timber-framed classroom blocks was initiated by the Ministry of Education and completed by BRANZ to better understand the seismic resilience of timber-framed buildings within the Ministry’s portfolio. The tests demonstrated a significantly greater lateral load capacity than could be derived from engineering calculations at the time, and led to new parameters being included in the revision of the national seismic assessment guidelines in 2017. An opportunity arose during 2021 for the Ministry to evaluate the transverse performance of classroom blocks by undertaking tests on another type of standard block from the 1970s. These blocks feature timber portal frames, and had performed well during the Canterbury Earthquake Sequence. The tests undertaken by BRANZ involved laterally loading the central of five portal frames in each of two CEBUS blocks constructed at Tauhara College in Taupo in 1975 and 2000. The in-situ testing was carried out to levels of force greater than the ultimate seismic and wind loads applicable for the building, but generated very low levels of horizontal displacement at eaves levels. A subsequent phase of the testing involved testing of the bare frames at the BRANZ laboratories in Judgeford following extraction from the buildings. These frames deflected significantly more than the in-situ displacements. As well as providing further evidence about the resilience of single storey timber-framed buildings, this testing highlights the effectiveness of steel sheet roofs without engineered diaphragms as horizontal load transfer systems in buildings of light construction.