Multi-Hazard Mitigation Plan: Executive Summary

Home

Executive Summafv • The purpose of the law is to require the Department of Accounting and General Services to establish and implement a State Building Code • Creates a State Building Code Council with decision making authority • Preserves responsibilities for administration, permitting, enforcement and inspection as presently held by each county • Prohibits conflict with chapter 464, HRS, Professional Engineers, Architects, Surveyors and Landscape Architects • Requires adaption of the State Building Code by the local county government within 2 years • Permits county amendments without State Building Code Council approval • There is great importance of adopting the IBC as it relates to the County's ability to advance in FEMA's Community Rating System (CRS) program. If the iBC is not adopted, the County cannot advance past CRS Classification 8 or only a 10-percent reduction in flood insurance premiums for all Hawaii County policy holders. • HAZUS MH Earthquake Modeling with updated building inventory database The Hawaii and Maui County general building stock data was enhanced by using residential and commercial property tax databases and several state government property databases. The project incorporated the unique Hawaii building types including the vulnerable post and pier single-wall construction type that statistically exhibited much higher damage levels than conventional wood-frame construction on slab-on-grade. • Post and Pier Retrofit Study A survey of 53 post and pier houses on the island of Hawaii was performed to determine the typical structural characteristics and variations in structural properties of these houses in the most vulnerable areas. The survey also investigated the extent of damage of these homes during the 2006 earthquakes along with any attempts to retrofit the houses at the time of survey. Based on this survey, a number of prototypical models of post and pier houses were analyzed for different levels of ground motion. A number of aspects of the houses were found to require retrofitting for even moderate levels of ground motion. From the analysis, three retrofit options were developed, with the applicability of each retrofit based on the location of the house and its structural properties. The retrofits are presented in a general format that can be applied to a wide range of houses without specific input from a structural engineer, except in special cases. Retrofit Option 1 is primarily a strengthening of connections using the existing post and pier foundation system, applicable in regions of low to moderate seismic hazard and for houses with moderate differential post heights. Retrofit Option 2 uses additional plywood shear walls between the ground and first floor of a house to provide additional lateral strength and stiffness to the foundation system. This retrofit is applicable in all regions with most combinations of differential post height and other structural properties. Retrofit Option 3 uses masonry shear walls to provide additional lateral strength and stiffness. This option is applicable for any post and pier house, although in some extreme cases a structural engineer would need to be consulted if the properties of the house fall outside the range of properties considered in the report. xix Hawaii County Multi-Hazard Mitigation Plan