Semi-quantitative seismic risk screening tool for existing buildings in Canada

The National Research Council Canada (NRC) recently developed a semi-quantitative seismic risk screening tool (SQST) for existing buildings in Canada. The SQST aims to supersede the Manual for Screening of Buildings for Seismic Investigation developed by NRC in the early 1990s. The SQST consists of three key components: (1) a structural scoring system that quantitatively assesses the structural seismic risk based on probability of collapse; (2) a non-structural component scoring system that qualitatively assesses the seismic risk of non-structural components based on seismic demand; and (3) a ranking procedure that prioritizes potentially hazardous buildings for seismic evaluations and possible upgrading. The SQST intends to inexpensively identify and exempt buildings with acceptable life safety risk and optimize the allocation of resources to assess the seismic risk of portfolios of buildings. Seismic screening with the SQST can be completed with either paper-based screening forms or a web-based application. The applicability of the SQST is demonstrated by conducting a pilot study for 33 existing buildings across Canada.

A Sensitivity Analysis Approach for Assessing the Effect of Design Parameters in Reducing Seismic Demand of Base-Isolated Storage Racks

The most used global sensitivity analysis (GSA) method is based on variance. This is performed using Monte Carlo Sampling (MCS) or Latin Hypercube Sampling (LHS). It requires a large sample to obtain accurate estimates. Density-based methods, such as the GSA PAWN, have been developed to reduce the sample size without compromising the result. PAWN is simpler than other methods because it uses cumulative density functions (CDF) instead of probability density. This method has been widely used in areas such as environmental engineering with very good results, reducing computation time. However, its use in structural engineering is incipient. The PAWN method was used to classify the design variables of the isolation system in relation to their sensitivity, and in relation to the seismic response of industrial storage racks. The above was analyzed in terms of the effectiveness of each variable to reduce the seismic demand using a novel base isolation kinematic device (BIKD). Racks with different combinations of their structural parameters such as the number of storage levels, the height between them, and isolation period, among others, were studied. The dimensions of the racks were chosen to match those that would later be experimentally tested on shaking table. An earthquake whose response spectrum matched the design spectrum of current Chilean regulations, was considered as seismic forcing. The maximum base shear load, the displacement of the top level of storage and the floor drift were considered as target responses to be studied. Fixed base racks (FBR), as reference, and base-isolated racks (BIR) were analyzed. The results showed the effectiveness of using the BIKD system in reducing all three-target responses up to one order of magnitude. Additionally, it was determined that the parameters that have the greatest influence on the response correspond to the number of storage levels and the height between them, both for FBR and BIR.