Vidal P. Paton-Cole

Dynamic performance of a brick veneer house with steel framing

Abstract Brick veneer construction is a very common form for residential structures in Australia and is growing in popularity in New Zealand. The structural frame is made from steel or timber, and non-structural brick walls are attached to the frame via brick ties. Under earthquake loading there is a complex interaction between the frame and veneer walls, particularly in the out- of-plane direction, where there is risk of brick wall collapse. While there is a standard component test method for assessing the seismic capacity of brick ties, this method has been developed around brick veneer on timber studs. In order to realistically assess the overall performance of brick veneer construction with steel framing, a full scale one-room test structure “Test House” was tested on a shaking table. The Test House incorporated veneer walls with different geometries. It was subjected to varying levels of the El-Centro earthquake ranging from moderate serviceability limit state ground motion to well beyond the design maximum considered earthquake for New Zealand. These levels of shaking were selected in order to ascertain the response for specific limit states to the New Zealand Loading Standard and to compare against minimum performance requirements. Comprehensive measurements on the frame and veneer walls were taken, including acceleration, drift and differential movements between the frame and veneer. The Test House performed very well, with no brick loss up to 2.6 times El-Centro earthquake, which is well in excess of all performance requirements. This paper presents a summary of the outcomes from the experimental test program.

Rocking Behavior of Irregular Free-Standing Objects Subjected to Earthquake Motion

ABSTRACT Free-standing rigid objects and structures are dominantly found to exhibit rocking behavior and can be vulnerable to overturning during an earthquake as demonstrated by numerous past earthquake events. Such objects are typically considered to be displacement sensitive with their rocking response being well presented by the Peak Displacement Demand (PDD) parameter of the supporting floor’s motion. This in turn can be directly related to an object’s width (along the direction of motion) for assessing its vulnerability to overturn. Such findings have been sufficiently justified by refined dynamic analysis supported by experimental evaluations which were based on rigid blocks with uniform geometric format (i.e., regular in their mass distribution). However, vulnerable rocking objects can be asymmetric and accordingly their sensitivity to floor displacement cannot be directly related to their width. The key parameter which defines irregular objects’ response to rocking motion is represented by the degree of eccentricity of their center of mass. In this study, the well-known rocking equation of motion is reconfigured and devised to model the rocking responses for 280 irregular objects undergoing eight earthquake motions which included artificial and recorded earthquakes. Analytical results obtained from solving the adjusted equation of motion were evaluated with sophisticated finite element (FE) models simulating the 280 irregular cases. This experimentally validated FE modeling approach was found to be time- and cost-effective for understating the rocking behavior of asymmetric objects as well as clarifying an interesting relationship between the object’s damping level and the condition of the supporting base (i.e., whether being provided with supports at the points of rotation or not). The rocking response of irregular objects was found to be highly influenced by the level of eccentricity of the object when excited by motions with high displacement amplitudes, while such influence was not found noticeable by wider objects. Based on the developed trends between the maximum top displacement of irregular objects and the PDD, an expression for estimating the rocking amplitudes is proposed which is a function of the object’s eccentricity.