Conventional and supplementally damped light-frame timber top additions of RC structures

The paper presents the first section of a research study on light-frame timber structures to be installed on top of reinforced concrete (RC) buildings. The study has a dual objective: to evaluate the possibilities offered by traditional “platform-frame” interventions, and explore new configurations based on the incorporation of small-sized supplemental damping systems, easily hidden behind the oriented strand board sheathing panels of the light-frame structure. A representative real case study was selected for the application of the two structural solutions, consisting of a two-storey RC residential building, characterized by an eccentric position of the RC core surrounding the stairwell. This layout determines a remarkable irregularity in plan and thus significant seismic torsional response effects, making the examined case particularly challenging. The single-storey addition covers approximately 70% of the flat roof level. The paper reports: a seismic assessment analysis of the building in current conditions; the modelling criteria and the design of the light-frame timber superstructure in the traditional configuration and in the presence of the supplemental damping system, consisting of dissipative braces incorporating small-sized pressurized fluid viscous spring-dampers; and comparisons between the seismic performance of the superstructure and the entire building under the two different design hypotheses.