Badania krótkich wsporników żelbetowych wzmacnianych zbrojeniem wklejanym i stalowymi akcesoriami

The subject of the Bulletin is strengthening of existing reinforced concrete corbels and the proposed thesis is that it is possible to effectively increase the carrying capacity of the corbels with embedded through-section (ETS) rods.The main part of the dissertation is the author’s own experimental research. The study covers two categories of corbels: one with moderate shear slenderness (ac/d = 0;5÷0;6) and one with short span-to-depth ratios (ac/d ≈ 0,3). Prior to the start of the strengthening process, a force equivalent to about half of the ultimate load determined on the reference elements was applied to each corbel. All corbels were being strengthened under load. Threaded rods (M16, class 8.8) were used as addi-tional reinforcement. Some of the corbels were equipped with a steel accessory anchored to the concrete with post-installed screws. During the tests deformations on the reinforcement and the concrete surface were measured and the cracks and their width were recorded. A digital image correlation system (Aramis) was used during one of the test series. On the whole, nineteen corbels were tested: six reference and thirteen strengthened ones. Increase of load capacity of up to 64% (using embedded through-section rods only) and over 150% for the steel accessory was observed.As a result of calculation analyses, it was found that the methods based on the strut-and-tie models correspond very well with the results of the author’s own tests for the moderate shear slenderness corbels and the post-installed reinforcement can be treated in the same way as the cast-in bars. The situation is different in the case of corbels with short span-to-depth ratios. It has been shown that the existing calculation methods lead to more conservative results if the mechanical rein-forcement ratio of the element is smaller.Due to the different method of destruction the corbel with steel accessory (C – III) was analyzed separately. In that case the ultimate load was determined by the load capacity of anchors.As a result of the studies and analyses it was found that corbels with moderate and high shear slenderness ac/d ≈ 0,5 and low reinforcement ratio can be effectively strengthened by embedded through-section rods.Such reinforcement is less effective in corbels with short span-to-depth ratios ac/d ≈ 0,3.