Hernán Santa María

Optimal Strut-and-Tie Models Using Full Homogenization Optimization Method

An optimization method based on homogenization is proposed for finding optimal strut-and-tie (ST) models for reinforced concrete elements. The method uses a layout that minimizes displacement for a given loading state in a linearly elastic regime by mixing two materials. Although this optimal layout might contain fine mixtures, one can still obtain a strongly resembling ST model without mixtures that performs closely to the optimal configuration through a penalization procedure. Two examples from the ST literature are used to illustrate the application of the method: the dapped beam and the beam on beam. The reinforcement layouts obtained make the element more efficient in terms of ultimate load divided by the weight of the steel used and having smaller deflections and crack widths. It is remarkable that the used optimization method, which considers the structure in the linearly elastic regime, gives a very good performance for the nonlinear regime.

Development of a Fragility Model for the Residential Building Stock in South America

South America—in particular, the Andean countries—are exposed to high levels of seismic hazard, which, when combined with the elevated concentration of population and properties, has led to an alarming potential for human and economic losses. Although several fragility models have been developed in recent decades for South America, and occasionally used in probabilistic risk analysis, these models have been developed using distinct methodologies and assumptions, which renders any direct comparison of the results across countries questionable, and thus application at a regional level unreliable. This publication aims at obtaining a uniform fragility model for the most representative building classes in the Andean region, for large-scale risk analysis. To this end, sets of single-degree-of-freedom oscillators were created and subjected to a series of ground motion records using nonlinear time history analyses, and the resulting damage distributions were used to derive sets of fragility functions.

Data collection after the 2010 Maule earthquake in Chile

This article presents an overview of the different processes of data recollection and the analysis that took place during and after the emergency caused by the Mw 8.8 2010 Maule earthquake in central-south Chile. The article is not an exhaustive recollection of all of the processes and methodologies used; it rather points out some of the critical processes that took place with special emphasis in the earthquake characterization and building data. Although there are strong similarities in all of the different data recollection processes after the earthquake, the evidence shows that a rather disaggregate approach was used by the different stakeholders. Moreover, no common standards were implemented or used, and the resulting granularity and accuracy of the data was not comparable even for similar structures, which sometimes led to inadequate decisions. More centralized efforts were observed in resolving the emergency situations and getting the country back to normal operation, but the reconstruction process took different independent routes depending on several external factors and attitudes of individuals and communities. Several conclusions are presented that are lessons derived from this experience in dealing with a large amount of earthquake data. The most important being the true and immediate necessity of making all critical earthquake information available to anyone who seeks to study such data for a better understanding of the earthquake and its consequences. By looking at the information provided by all these data, we aim to finally improve seismic codes and engineering practice, which are important social goods.