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Masonry is one of the oldest building construction methods used by man thousands of years ago, and one of those used today. The masonry buildings look stable and give a sense of security and comfort, leaving a lasting impression of strength. Shaking table tests are planned in order to deepen the understanding of the behaviour of confined masonry structures. This paper presents the observations from a series of shaking table tests done on a 1:1 scale confined masonry wall model without openings. The specimen was tested under constant gravity load and incrementally increasing in-plane loading seismic up to the occurrence of damage. The horizontal load applied is in-plane of the specimen. Then, the seismically damaged specimen was strengthened, using glass fiber reinforced polymers (GFRPs), and tested again. The specimen was strengthened on the surface of two sides. Hysteresis curves before and after with GFRPs wall strengthening are analysed. The tests results indicate that the GFRP system restores and increases the lateral load capacity of strengthened walls. Moreover, GFRP helps to increase the area of hysteresis curves, leading to increased seismic energy dissipation.

<p>This article reviews the possibilities of the application of Ultra-High Performance Fiber Reinforced Concrete (UHPFRC) for strengthening existing steel and concrete structures in Bulgaria. Although the application of UHPFRC in structural engineering is increasing worldwide in the last decades, both for strengthening and for new designs, in Bulgaria it is still highly restricted. This is mainly due to the lack of experience and knowledge in design engineers, contractors and clients.</p><p>In order to investigate the possibilities of its local production in concrete plants and to gain experience in its application for strengthening existing structures a research project in the University of Architecture, Civil Engineering and Geodesy in Sofia has started recently. Under this project strengthening of steel orthotropic bridge decks as well as reinforced concrete beams is envisaged. The strengthened specimens will be tested in laboratory under static loading and the results are going to be compared with the test from non- strengthened ones. All specimens are full scaled as for the orthotropic deck only a segment between two cross girders is considered.</p><p>The results and experience gained from the research project will be used in the future to promote the application of UHPFRC in Bulgaria for durable reinforced concrete repairs and strengthening of existing steel bridges with orthotropic decks.</p>

<p>In the University of Architecture, Civil Engineering and Geodesy in Sofia a research project has started in 2018 aiming to investigate the possibilities of local production and application of high- strength concrete (or even UHPFRC) for strengthening existing structures in Bulgaria. Under this project laboratory tests of steel orthotropic bridge deck specimens as well as reinforced concrete beams, strengthened with high-strength concrete are performed. All elements are strengthened with an additional layer of high-strength concrete with thickness of 50mm on top.</p><p>The results obtained from the tests are summarized in this article. Comparative analysis showing the effect of this strengthening method is also presented. At the end summary and conclusions are drawn. Future steps for enhancing and promoting this strengthening technique in Bulgaria are outlined.</p>

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