PRECAST BUILDINGS EQUIPPED WITH SLB SEISMIC DEVICES

Bozzo L.M.; Ramirez J.; Bairan J.; Bozzo G.; Muñoz E. · World Conference on Earthquake Engineering proceedings (2021)

Resumen

This work initially describes Shear Link Bozzo or SLB devices. These devices provide more than 104 single dissipators that combined together in parallel result in a very large set of potential structural solutions. All devices are stiff but ductile start yielding at displacements as low as 0.20mm. The paper includes modelling aspects and two automated selection procedures called: (1) direct iterative procedure and (2) inverse or fixed force iterative procedure. Both procedures are implemented in an automated selection program in a plug-in for ETABS commercial software. Under the premise that a large number of devices are required in order to assess a significant structural benefit, their unit cost is very cheap. This technique is applied to a five-story precast reinforced concrete building frame, called SLB Building. The building is made up of eleven 40cmx40cm section columns and it has hinged beams. Consequently, the structure without dissipators is very flexible but adding these devices the period shortens drastically. The interior floors are diaphanous so the structural configuration may have diverse occupancy such as housing, offices or hospitals. This building was equipped with 80 small SLB devices showing its performance for the maximum earthquake of the Peruvian seismic code. The analysis was nonlinear for the ten time-history records compatible with the S1 soil spectrum in Zone 4. All seismic energy dissipation was concentrated in the dissipation devices so there would be no structural damage. In addition, the levels of non-structural damage were controlled with initial stiffness of these devices since lateral displacements were reduced to levels below 0.007, for the maximum Peruvian design spectra. Two structural configurations were studied for the columns: fixed or hinged at their bases. The performance of both solutions is compared in terms of drifts, floors accelerations, and base shear. In all cases, the accelerations show a clear reduction with height achieved by the energy dissipated by the devices. The story shear forces divided by the structural weight is calculated for each signal resulting in values between 0.13 and 0.27 and consequently the force reduction factor (R) is between 5 and 7 without any structural and non-structural damage. It is concluded that this precast solution equipped with SLB devices is optimal for homes, schools and hospitals. Its structural performance is comparable to base isolation but with its significant simplicity, low cost and minimum or no special maintenance required using affordable technology for a widespread type of conventional buildings. Finally, the proposed general system has less uncertainty than base isolation since over strength is controlled by simple previous tensile tests for the steel plates, adjusting final device dimensions before their manufacturing and without very large base displacements.