Building retrofit with reduced web (RWS) and beam (RBS) section limited-ductility connections

Abstract

Softening of beams near the moment connection can be regarded as one of the most convenient methods for retrofitting non-seismically designed buildings. This can be done by drilling the beam web near the connection (aka RWS–Reduced Web Section) or cutting the beam flanges (aka RBS–Reduced Beam Section). Thus, becoming a cost-effective option for retrofitting and erection of new buildings, while optimising use of steel; making the most of this high environmental impactful material. This study presents a comprehensive investigation of the effects of using extended end-plate bolted RWS and RBS connections in building behaviour when subjected to strong ground motion. For that purpose, incremental dynamic analyses (IDA) were performed in a low height building fitted with RWS and RBS connections capable of limited ductility. This was done with the aim of characterising the seismic behaviour of buildings with deficient earthquake design after being subjected to seismic upgrade. It is observed that empirical fragility curves show that probabilities of exceeding 1%, 2% and 4% inter-story drifts are significantly lower (more than 25%) for the building that is designed with RWS connections instead of RBS connections; while the probability of collapse is reduced by at least one third. This indicates that deployment or RWS connections can reduce the risk of both; severe structural damage and, large economical loss due to damage of non-structural elements when seismic demands are moderate.