Enhanced macroseismic method for the vulnerability assessment of representative ’50–70s social housing units

Abstract

This study proposes an enhanced macroseismic method, based on RISK-UE LM1 Vulnerability Index model, for assessing the vulnerability of social housing buildings constructed between 1950 and 1975, which typically lack seismic provisions, feature repetitive architectural designs, and have either exceeded or are about to exceed their design working life. Initially, a comprehensive review of existing literature was conducted to identify relevant vulnerability parameters for calculating the Vulnerability Index. Huelva, located in southern Spain, was chosen as a pilot city due to the representativeness of its buildings and the availability of original project documents. Analysing these documents, along with microzonation studies and on-site visual inspections, facilitated an understanding of the structural types (primarily reinforced concrete moment-resistant frames or unreinforced masonry walls) and the further analysis of the selected vulnerability parameters. The new method improves upon the original by incorporating several enhancements, like integrating the number of floors into the Type of Soil Modifier, creating a Combined Modifier that amalgamates parameters based on the construction year, defining the Vertical Irregularity Modifier based on the building’s compactness ratio, and introducing a Slope of the Ground Modifier. Additionally, it considers pounding effects solely for staggered floor slabs and features adapted modifier weights for the specific building types. To address potential overestimation caused by summing multiple modifiers, the method employs a modified square root of the sum of squares (SRSS) approach, which provides a more robust estimation of their combined impact. The method was applied to buildings in Huelva using deterministic (recurrence of the 1755 Lisbon earthquake) and probabilistic (code, intensity VII) scenarios. Results reveal expected damage levels contradicting the damage control philosophy, indicating the need for preventing interventions and further research on similar structures.