Lateral load tests of houses damaged in the Christchurch earthquakes –preliminary findings

A series of tests have been undertaken that showthat the strength and stiffness of typical light timberframed houses, after real and simulated earthquakedamage, are still greater than current standardsrequire.1. For House 3 the maximum deflection obtained wasapproximately 20mm and was located on the centralinternal wall, and maximum deflections were similarfor both push and pull tests.2. Test loads applied were larger than the loadsexperienced during the 2011 Christchurch earthquakes,and these were determined from average recordedaccelerations.3. The stiffness obtained from the static deflectionscorrelated with the natural frequency of the dynamicresponses. All houses were very stiff which issignificant in determining the seismic coefficients anddesign loads.4. The maximum load achieved in House 4 was wellin excess of design levels and maximum credibleloads. The loading was also much higher than strengthpredictions based on current standards wouldcalculate.5. For all houses tested the residual strength afterthe Christchurch earthquake was well beyond therequirements of the loading standards and what wouldbe required to resist further similar earthquakes.6. The damage observed after loadings greater thanrequired in the standards was adequate for loadresistance but was not cosmetically acceptable.7. Fragility of timber houses needs to be determinedand further testing is needed to evaluate more recenthouses with a focus on damage detail at serviceabilitylevel loads.8. This work contributes to an understanding of thereal loads that houses have experienced but furtherevaluation of the data is needed to determine thethresholds at which damage occurs.9. Acceptable stiffness for serviceability performanceof light timber framed buildings needs to bedetermined and further tests carried out.10. Cosmetic damage needs to be determinedrelative to loading for determining fragility curves forfinancial risk.