Modern Solutions for Strengthening of Masonry Structures SORIN DAN*, CORNELIU BOB*, LIANA BOB**, AURELIAN GRUIN***, CATALIN BADEA* * Civil Engineering Department "Politehnica" University of Timisoara Str. T. Lalescu, No. 2, Timisoara ROMANIA ** ICECON Research Institute Timisoara Branch Str. Oltul, No. 1, Timisoara ROMANIA *** INCERC Building Research Institute, Timisoara Branch Str. T. Lalescu, No. 2a, Timisoara ROMANIA sorin.dan@ct.upt.ro; cbob@mail.dnttm.ro; agruin@incerctm.ro; catabadea@gmail.com http://www.ct.upt.ro Abstract: The paper presents the rehabilitation methods for masonry structures. In the first part, an experimental programme concerning the technical efficiency of the masonry strengthening with different type of bars/rods is presented. The test elements are erected as models, scale 1:2, and represent shear walls with window opening. In the first stage the models are tested at vertical and horizontal actions. Finally, the models are strengthened with different types of bars / rods (Romanian High Adherence Steel Bar; Brutt Helical System – Brutt Saver BHS) as near-surface- mounted-reinforcement and Fibre Reinforced Polymer Systems CFRP and retested. In the second part, the rehabilitation of an existing church of about 150 years old is presented: a brick masonry structure with local damages was strengthened with near-surface mounted reinforcement. Key-Words: existing masonry structures, seismic zone, strengthening, near-surface-mounted reinforcement, CFRP. 1 Introduction The motivation for research and development into repairing, strengthening, and restoration of existing buildings in seismic zone is sustained by necessity to extend the life of structures. The masonry structures are the oldest and still very used type of buildings. The main target of the paper represents the rehabilitation of old masonry buildings located in seismic zones. Masonry structures present some important vulnerability in seismic zones: the overall lateral stiffness values along the two main axes are different; lack of seismic joints to divide building parts having different dynamic characteristics; lack of reinforced concrete straps at each level; defects of wall connections at corners, crossings and ramifications as well as the presence of cracks; inadequate bearing capacity at normal forces on the walls. On the other hand, structural weakness is characterised by various irregularities and discontinuities or by general structural vulnerabilities: irregular distribution of stiffness at lateral displacements; strength discontinuities; mass irregularities; vertical load discontinuities. Masonry, made with bricks, stones or other blocks, has a high compressive strength but its main disadvantage is poor tensile strength due to masonry members will crack and fail even if they are subjected to relatively small loads. The methods of strengthening existing masonry structures with the use of traditional technology are various: erection of RC cores appropriate distance combined with straps at each level, masonry lining with reinforced concrete, masonry confinement with steel profiles, interlocking of masonry walls at corners, crossing and ramifications with RC elements and/or some steel profiles, adding new inner walls and/or some outside abutments. Near-surface-mounted reinforcement implies that steel bars/rods mainly of CFRP are bonded in sawn grooves in the masonry or concrete cover. The use of this technology has a lot of advantages: no requirement for surface preparation work, installation time is minimal, no change of the existing structure dimensions, the cost compared with traditional methods is lower even thaw the material costs are higher. 2 Experimental Programme 2.1 Bond strength tests The bond between strengthening bars and substrate material like concrete, mortar, brick/stone masonry is an important factor in order to perform an efficient rehabilitation on structural members. Aim of this paper is to investigate the mechanism of bond between two types of bars and brick masonry element taking into account two parameters: type and diameter of strengthening bar. The bar types used for the experimental program are: Romanian Profiled Steel Bar PC 52 which is a hot-rolled steel and Brutt Helical System – Brutt Saver which is a special bar which gives a high bond at a small cross- sectional area. Three diameters have been used for each type of bars. The geometrical and mechanical properties of the bars are presented in Table 1. Proceedings of the 11th WSEAS International Conference on Sustainability in Science Engineering ISSN: 1790-2769 64 ISBN: 978-960-474-080-2