Dr. Oyarzo-Vera, Claudio

Vibrations on timber floors are among the most common serviceability problems in social housing projects. The presence of low damping levels on these floors could cause excessive vibrations in a range of frequency and amplitude that generate discomfort in users. This study focuses on the influence of the damping ratio in the dynamic serviceability of social housing timber floors due to walking excitations. More than 60 human-walking vibration tests were conducted on both laboratory and in-situ timber floors. The floors were instrumented with accelerometers, and fundamental modal damping ratios were estimated by applying Enhanced Frequency Decomposition Domain (EFDD) and Subspace Stochastic Identification (SSI) methods. The vibration dose value (VDV) was used to estimate the dynamic serviceability of floors. The results indicated that timber floors had an impulsive-type vibration response, with fundamental damping ratios between 1.9% and 14.8%, depending on their constructive characteristics. The in-situ floors had damping ratios between two to three times greater than the laboratory floors due to the presence of non-structural elements. Finally, it was possible to demonstrate that the floors with the highest damping ratios reached lower vibration dose values and, therefore, a better dynamic serviceability performance.

Damage progression indexes are widely used to evaluate the performance of structural elements in buildings and bridges subjected to seismic actions. Although the Park & Ang damage index is currently implemented in several computational tools, the index has not been calibrated for squat and thin reinforced concrete (RC) elements controlled by shear deformations. It has been observed that the equations originally proposed for the Park & Ang damage index are unsuited for these types of structural elements, which are characterized by a failure mode dominated by shear instead of flexural deformations. The index was evaluated in this study for squat, thin and lightly-reinforced concrete walls using experimental data from a program comprising monotonic and reversedcyclic load testing of 25 RC squat cantilever walls. The experimental program included walls, with and without openings, having height-to-length ratios equal to 0.5, 1.0 and 2.0. Full-scale wall thickness and clear height were 100 mm and 2.4 m, respectively. The specimens were built using three different types of concrete (normal-weight, light-weight and self-consolidating) with nominal compressive strength of 15 MPa. A novel formulation for the parameter β included in the Park & Ang damage index was proposed in this study using key variables of the wall specimens such as web reinforcement ratio and cumulative ductility. Comparison between the computed damage index and crack pattern evolution observed in wall specimens at different damage states demonstrated the ability of the model to numerically assess the damage of the wall specimens. Hence, this new formulation proposed for parameter β leads to a better estimation of damage for this particular type of elements when applying the broadly used Park & Ang damage index.