He is a member of ACI Committees 440, Fiber-Reinforced Polymer Reinforcement; and Joint ACI-ASCE Committee 445, Shear and Torsion. His research interests include punching and post-punching of flat plates and the strengthening and rehabilitation of structures.

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.

A greater number of structures are being built with flat reinforced concrete slabs because they offer several advantages. However, many designers are still unsure about the type of slab that has the best structural performance and which building codes provide the best strength estimates. This study presents nonlinear computer simulations of 16 flat reinforced concrete slabs under symmetrical punching: 4 solid slabs, 4 waffle slabs with wide beams, and 8 waffle slabs with different numbers of ribs supported in the solid area of the slab. Geometric longitudinal reinforcement ratios ranged from 0.45% to 1.97%. The results showed that solid and beamed slabs are more resistant, and normative estimates overestimate their strengths, while the opposite outcome was found for waffle slabs, whose estimates provided in the codes were rather conservative. The most accurate code was EC2, followed by ACI 318 and NBR 6118.

Although several advantages - either constructive or architectural - are assigned to flat slabs, the continuity between consecutive spans in multifloor buildings may turn slab-column connections into a critical region, due to the limited contact between both elements. When transferring moments caused by horizontal and/or vertical eccentric loads are present, these effects are even more pronounced on external panels. Specific studies on the effects of outward eccentricities are still rather scarce, although it is recognized that the codes, in general, are concerned with eventually meeting all potential cases, seeking to improve safety structural performance. Some current recommendations are based on considerable extrapolations, whose theory was originally developed for cases of asymmetric loading at internal connections and need to be consolidated with specific test data. Thus, to investigate the structural behaviour of slabs-edge columns connections, four specimens were tested, reproducing a 2,350 mm x 1,700 mm portion of a 180 mm thick reinforced concrete slab adjacent to a 300 mm x 300 mm cross section squared edge column, with a projection at the base for the imposition of eccentricities. The position of the support under the column has determined the eccentricity, defining in physical terms the interaction between bending moment and shear force, as follows: 300 mm (inward), centred (reference) and 300 mm and 400 mm (outward). Experimental results allowed to comparatively assess the performance of the specimens relating the strain measurements in steel and concrete, vertical displacements, rotations, failure mode and ultimate loads of the slabs. Results indicate that the influence of transferring moments on failure modes is much more pronounced than the shear action in the case of edge connections subjected to outward eccentricities.

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.