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Using innovative materials or devices in techniques for strengthening or repair of RC concrete members may provide interesting alternatives for structural engineers. Laboratory tests were conducted on full scale reinforced concrete columns and a masonry wall that suffered severe damage. Carbon Fiber Reinforced Polymer - CFRP sheets and anchors were used to improve shear capacity or ductility elements. CFRP jacket were installed on column hinge regions while diagonal ties (tension braces) were used on the masonry wall. Mechanical splices were used in columns where concrete crushed and bars buckled by replacing the buckled bars and providing continuity to the longitudinal reinforcement. It was found that performance of the retrofitted members was comparable to that using conventional techniques and the performance was generally better than certain “fast” retrofit procedures reported in the literature. The choice of technique depends on the degree of damage, the cost of replacement, and performance required. Having the results of cyclic load tests of rehabilitated concrete members, envelope or backbone curves were obtained following the ASCE41-07 and proposed ASCE41-13 procedures. The backbone curves were used to develop behavioral models that can be used in the analysis and design of those types of concrete members and retrofit procedures. The inclusion of the behavioral models into current Performance Based Seismic Design procedures for strengthening of existing or repaired damaged buildings is proposed. / text

Application of refined ultimate state theories and use of high strength materials have resulted in longer spans and smaller depths of reinforced and prestressed concrete structures. Consequently, the condition of the limiting deflection rather than the strength requirement often is the governing design criterion. Long-term deflections might be up to 3 to 4 times larger than the short-term deflections. Such increments are caused by complex physical effects such as concrete creep, shrinkage and cracking, bond defects, etc. Long-term concrete creep and shrinkage deformations govern prestress losses. Structural analysis can be carried out either by traditional design code methods or numerical techniques. Although design code methods ensure safe design, they have significant limitations. Different techniques are used for strength, deflection, crack width and prestress loss analyses. Besides, most of the simplified approaches do not assess such factors as concrete shrinkage, cracking or tension stiffening. Based on a large number of empirical expressions and factors, they lack physical interpretation and do not reveal the actual stress-strain state of cracked structures. On the other hand, numerical techniques are universal and can take into account each physical effect. However, inadequacies made in the prediction of each effect might lead to significant inaccuracies when integral magnitudes such as deflection are to be assessed. Consequently, the predictions by the numerical... [to full text]