Predictions of Damage to Timber-Framed Houses. II: Aligning Social and Engineering Predictions of Earthquake Damage before and after Strengthening

This paper is the second of two companion papers that seeks to compare homeowners' expectations of damage and engineering predictions of damage to timber-framed houses before and after undertaking seismic structural strengthening. Part I analyzed the seismic vulnerability of wooden-framed houses located on slopes in Wellington, New Zealand, investigating factors of plan shape relative to the slope, slope variations, and wall distribution, and how they influence the final seismic performance of houses. A structural survey provided data on the form and typical details for the subfloor bracing, and this was then used as the basis for a simple strengthening solution that is numerically investigated here. This companion paper analyzes the improvement of seismic performance after undertaking strengthening to the subfloor structure using a multiple stripe analysis. In the last phase of this work, engineering-based predictions of performance as determined using the numerical models were compared to homeowners' expectations of damage before and after undertaking strengthening. This comparison paper found that although strengthened timber-framed houses located on slopes satisfy the minimum requirement of New Zealand design codes, there is still a probability of damage occurring, which would not satisfy owners' expectations of performance in all scenarios.