The technology of the Construction Industry is advancing constantly. Every year, new materials, equipment, and building techniques are introduced. In the specific case of reinforced and pre-stressed concrete structures, the innovations have contributed to the improvement of the properties of the concrete and the durability of the structures that incorporate this material. These advances are not restricted to the construction of new structures, however, and it is important to recognize the need to recuperate structural elements or increase their resistance, which has provided incentives for the improvement of techniques of structural reinforcement. In this context, the present study used a combined theoretical and experimental approach for the investigation of the effectiveness of the reinforcement of concrete columns by jacketing them with polymer mantles strengthened with carbon fibers. The analyses aimed to determine the effectiveness of the mantles in terms of the increase in resistance to axial compression and contribute to the understanding of the structural behavior of columns strengthened using this technique. To this end, centered axial compression tests were run on five short reinforced concrete columns, including one control column and four experimental columns with different reinforcement ratios. Numerical simulations were also run in the Abaqus software to determine the distribution of tensions inside the columns. The sum of the evidence was analyzed and it was verified that the strengthening used in the columns increased considerably their resistant capacities, thus the gain in this capacity was directly proportional to the value of the used strengthening rate-the column with the biggest strengthening rate bore a last load 42.8 % bigger than the one borne by the column of reference, with no strengthening. From these data, it was possible to obtain a simple predictive model of the increase in resistance capacity of columns strengthened with carbon fibers.

This research aimed to compare the ultimate load of 10 waffle flat slabs with different sizes of solid area and spacing between ribs. For this, a non-linear computational simulation of the slabs was carried out until their failure using the engineering software ANSYS. The failure modes and loads were analyzed, and the results showed that the models with less solid area presented less bearing capacity in comparison to the models with greater solid area when the failure mode was shearing of the ribs. The slabs with the largest solid regions experienced punching shear and behaved in a similar way as solid flat slabs, indicating compliance with the codes in relation to their punching shear strength provisions, especially with the NBR 6118. The results show that a square solid area whose length is 15% of the span is reasonable and that the ACI, Eurocode 2 and NBR 6118 provisions underestimate the shear strength of the ribs.

The application of carbon fiber reinforced polymers (CFRP) as method of strengthening for concrete structures is replacing the conventional strengthening through the bonding of steel plates. However, since it is a recent technique, several codes from different countries still do not consider this type of strengthening. In this work, seven reinforced concrete beams were tested and analyzed. One was used as a reference beam and six were strengthened through the application of CFRP, with some variations regarding the strengthening, with the aim of verifying the efficiency of each system compared to the reference beam. For the computational analysis, the software ANSYS was used along with the plugin ACP (ANSYS Composite PrepPost), by comparing the results obtained in the simulation of the experimental results. Through the laboratory tests and the finite element simulation, it was concluded that the strengthening was efficient in all situations, but it was less efficient in cases where the strengthening was extended to the regions of simple flexure without proper anchorage. It was also possible to notice that the behavior of the simulated beams properly represented the reality, with the beams behaving comparably to the beams of the experimental test.

Research on behavior of flat slabs under punching shear, performed by Kinnunen, Regan and Muttoni influenced the main design recommendations. Meanwhile, studies about strut and tie model developed by Schlaich for beams, deep beams and corbels also influenced these design codes. This work aimed to adapt the strut and tie model for the punching shear resistance analysis in flat slabs. The punching shear resistance of 30 flat slabs verified through strut and tie model was compared to the one designed following Brazilian, American and European codes recommendation. Subsequently, this same model was validated by comparing the test results of 32 flat slabs. The strut and tie model results, when compared with the test results, showed a better average than those from codes, and the modified strut and tie model can become an alternative for punching shear strength prediction.