Structural upgrading of a 3-storey heritage structure of 1925 in Thessaloniki

Abstract

The structural upgrading and rehabilitation procedure of a historic building representative of 1920s construction in Thessaloniki, Greece is presented. The case study building is a listed three-storey reinforced concrete flat-slab frame structure sited in Nikis Avenue in front of the old seaside of the city of Thessaloniki. Reinforced concrete columns and beams frames along with wide infilled masonry walls are the load-bearing elements of the structure. The building was designed in 1925 without Seismic Code requirements and constructed in 1926. The ground floor was used for many years as a cinema, whereas the upper floors are areas where people may congregate since they are used as assembly halls (dining halls, reading and conference rooms). Concrete core tests and in-situ non-destructive tests were first performed to evaluate the compressive strength of the concrete and to detect - determine the existing steel reinforcements of the reinforced concrete members. The concrete strength was low and the steel reinforcement of several columns of the ground floor and slabs of the upper floors was found to be corroded. Analytical evaluations of the original and the strengthened structure were carried out in order to identify the weak members of the structural system and to justify the decisions of the strengthening methods adopted. Comparisons between the capacity of the existing or/and the strengthened members with the design requirements derived from the initial and the strengthened structural system analyses are also presented. Special attention has been given in issues regarding the simulation of actual details encountered in mixed structural system. The upgrading methods used along with the uncovering of latent defects during the strengthening works and how these were managed are also commented in this paper.