Cristián Sandoval

Prediction of the shear strength of reinforced masonry walls using a large experimental database and artificial neural networks

Abstract This paper analyses the accuracy of a selection of expressions currently available to estimate the in-plane shear strength of reinforced masonry (RM) walls, including those presented in some international masonry codes. For this purpose, predictions of such expressions are compared with a set of experimental results reported in the literature. The experimental database includes specimens built with ceramic bricks and concrete blocks tested in partially and fully grouted conditions, which typically present a shear failure mode. Based on the experimental data collected and using artificial neural networks (ANN), this paper presents alternative expressions to the different existing methods to predict the in-plane shear strength of RM walls. The wall aspect ratio, the axial pre-compression level on the wall, the compressive strength of masonry, as well as the amount and spacing of vertical and horizontal reinforcement throughout the wall are taken into consideration as the input parameters for the proposed expressions. The results obtained show that ANN-based proposals give good predictions and in general fit the experimental results better than other calculation methods.

Numerical assessment of accumulated seismic damage in a historic masonry building. A case study

ABSTRACT The current state of damage of a two-story unreinforced masonry historic building in Santiago de Chile is mainly due to the occurrence of the earthquakes of March 3, 1985 (Mw 8.0) and February 27, 2010 (Mw 8.8). Among the modern strategies available for a structural assessment of this type of constructions, nonlinear time-history analysis offers interesting possibilities but its use remains little explored because of their high computational demand. In this context, this article investigates the capabilities of a numerical strategy, based on macro-modelling, to simulate the accumulated seismic damage of a historic masonry building subjected to large seismic events. For this purpose, longitudinal and transverse components of accelerograms of the two large earthquakes that were recorded near the building are considered. Nonlinear time-history analyses were carried out in sequence using a global finite element (FE) model of the structure. The results show that the current crack pattern observed in the building can be simulated satisfactorily by the numerical approach adopted.

Seismic Vulnerability Assessment of Unreinforced Masonry Churches in Central Chile

In the central region of Chile, the unreinforced masonry (URM) churches underwent extensive structural damage during the 2010 Maule earthquake (Mw 8.8), highlighting the importance of implementing seismic risk reduction plans. These religious buildings are characterized by profound typological and constructive peculiarities, originated by the combination of the local build culture with European architectural revivalisms(i.e., Neo-Baroque, Neo-Classic, Neo-Renaissance and Neo-Gothic)during the Spanish domination (1536–1818). The uniqueness of this heritage and the seismic risk of the Chilean territory lead to the need to define a systematic method to assess the seismic vulnerability of the Chilean URM churches. In this paper, some results of an in-depth investigation on a representative stock of churches are reported. The investigation was based on a database implementation with geometrical, constructive, and structural characteristics of 40 URM churches in the Metropolitan Region of Chile. A preliminary qualitative assessment of the seismic capacity of these churches is provided using a survey of geometric indices. Than specific damages observed after the 2010 earthquake have been related to the recurrent failure mechanisms of masonry structures, taking into account 21 local mechanisms involving the macro-elements of the churches. The average level of damage suffered by each church was calculated through the global damage index and a histogram of damage levels frequencies has been arranged. These results are preliminar suitable probabilistic tools to support seismic risk reduction plans.

Experimental cyclic response assessment of partially grouted reinforced clay brick masonry walls

As part of an ongoing research project into the seismic response of partially grouted reinforced masonry (PG-RM) walls, this article presents the analysis of the experimental results of eight full-scale walls that were tested in laboratory under cyclic lateral loading. All walls tested were constructed using multi-perforated clay bricks and horizontally reinforced with ladder-type bed-joint reinforcement. Three design parameters were investigated in this research: wall aspect ratio, axial load level, and horizontal reinforcement ratio. The combined effect of these variables on shear response of the walls tested is analyzed and discussed. In addition, the accuracy of four shear expressions available in the literature is assessed against the experimental results obtained. The study has confirmed that a rise in the horizontal reinforcement ratio may lead to an increase in lateral capacity of PG-RM walls, although this effect would be more remarkable for square and slender walls. The results obtained also suggest that the influence of axial load level becomes more relevant as the aspect ratio decreases. In addition, moderate values of displacement ductility, ranging from 2.5 to 5.5, were estimated from a bilinear idealization. At the level of maximum lateral force, the average drift level for all walls tested in this experimental program ranged between 0.2 and 0.62%. Finally, the research also confirms the need to review the shear expressions currently available for the design and assessment of this type of walls.