G. Popescu1, R. Popescu1
1 IPCT Structuri Ltd
105 Magnoliei St, Bucharest, Romania

Keywords: Unreinforced Masonry, Diagonal, Shear strength capacity, Retrofitting, Ductility.

Abstract. In the countries of Europe and the entire world are Historic Centers with buildings that are centuries old. These buildings are precious because give information about building technique, architectural style, construction materials, of the period. Unfortunately, because of their high seismic vulnerability, many of these were lost in time, especially the old buildings situated into high seismic risk areas like Romania. The seismic vulnerability of a masonry building may be improved by strengthening its structure. First of all, it is necessary to realize a technical expertise, in accordance with Romanian Seismic Code. The materials and the structural elements should be tested in situ and, after obtaining the results, the expert engineer will establish a computational structural model, the calculation methodology, and the solutions of strengthening. Usually, the old structures are realized with unreinforced masonry walls with low strength and floors which are not rigid diaphragms. The shear walls are considered subjected to in-plane seismic loading and eccentric compression. Theoretical research studies, tests in laboratory and behavior of the masonry structures at the earthquake in time, have demonstrated that the main failure criterion of the unreinforced masonry walls is diagonal cracking due to main tensile stresses. Based on this hypothesis and considering the Theory of the strength of materials, the authors have developed, longer than twenty years, the own methodology (G&R Popescu) to calculate the shear strength capacity of the masonry wall with which is determined the degree of insurance against earthquake and the seismic risk class of the structure. All of this help to choose the strengthening solution of the structure, which may decreases the vulnerability and increases seismic performance of the building. The paper does briefly presentation of the authors’ methodology and, in Case Study chapter, its application to evaluate and strengthened an old house, built around 19th century situated now in Historic and protected area but with high seismic risk. The shear walls were strengthened (jacketing with reinforced cement mortar, reinforced concrete piers and ties etc), and the wooden floors have been rebuilt in reinforced concrete. An evaluation after strengthening has showed that the degree of insurance may increase with value above 50%. Although the choosing of computational structural model was difficult and achieving the strengthening solution has had some degree of difficulty, the building was strengthened ten years ago and, until now, has past successfully through many medium intensity earthquake.