Natural Hazards have been occurring more frequently in Tonga compared to past years due to effect of
Climate Change. Before the January 2022 event, strong storm sea surges from a Tropical Cyclone
destroyed coastal areas at ‘Eua Island that acted like a tsunami disaster. After the event of January 2022,
there have been more frequent earthquakes occurred near Tonga and more coastal protection were
damaged as well as bulk of the housing stock at the coastline. The Cyclone Resilient Houses (CRH) that
had been popularized in the past 40 years for housing reconstruction programs are now questionable
after the January 2022 event. For this purpose, the study is to perform structural performance evaluation
of the CRH timber shear walls using the AS 1684.2 – 2010 Capacity of Wall Bracings on timber framed
structures. This is assessed against the demand lateral forces from tsunami in addition to wind and
earthquakes based on the Australia standard AS 1170.2 and AS 1170.5 - 2002 and tsunami force using
the Japanese guideline. The analysis result shows that the capacity of the shear walls is safe in the case
of tropical cyclones because of the adequate nailed connections. The CRH is also safe from earthquakes
because the CRH has added capacity from steel strap bracing and stud ties. As for tsunami load, it is too
big to compare against the capacity of the CRH and therefore CRH can never withstand tsunami with
inundation depth over 1m. Therefore, the priority focuses on reinforcing strength of CRH in terms of
tsunami by raising floor heights above ground to no more than 3m with concrete or wooden poles that
would not increase tsunami wave pressures when it reaches the building. Moreover, this can be ignored
if relocation can be made to build CRH on higher grounds and/or build coastal protection and planting
mangroves over the coastal area of the inundated areas. Nevertheless, this draws attention into enforcing
structural performance evaluation of buildings to suggest future disaster mitigation planning of housing.
Keywords:
Cyclone Resilient Houses, Performance evaluation, Tsunami, Earthquakes, Horizontal force