Punching shear failure of concrete slabs poses a significant risk in many concrete structures. This mode of failure can be brittle and catastrophic. The ability to accurately estimate the punching shear capacity of slab column connections in existing structures is essential, especially in evaluating the suitability to new loads added to a building. Punching shear has been studied, both experimentally and analytically. However, due to the number of parameters involved and the complexities in modeling, current approaches used to estimate the punching shear capacity of reinforced concrete (RC) slabs include mechanical models and design code equations. Mechanical models are complex, while design code equations are empirical. This study investigates the ability of artificial neural networks (ANN) to predict the punching shear strength of concrete slabs. The parameters considered to be the most significant in punching shear resistance of RC slabs were: concrete strength, slab depth, shear span to depth ratio, column size to slab effective depth ratio and flexure reinforcement ratio. Using a large and homogenous database from existing experimental data reported in the literature, the ANN model is able to predict the punching shear capacity of slabs more accurately than were the code design equations.

The structural design for the East Addition to the St. Cloud Hospital facility in central Minnesota incorporated punching shear and cracked section design criteria that are not currently specified in ACI 318-05. The complexity of the column layout and shallow floor-to-floor spacing were the primary reasons for choosing a twoway 12 in. (300 mm) reinforced concrete flat slab for the 450,000 square foot (42,000 m2) addition. The use of continuous top and bottom reinforcing mats and the use of column capitals were early design decisions. Due to the complex column layout neither the Direct Design Method, nor Effective Frame Analysis would have been ideally suited to this project. A finite element analysis based program was employed to determine required flexural reinforcing, column joint forces and slab deflections. Design methodologies were investigated, and a method from the literature was chosen that incorporates slab depth, aggregate size, and reinforcement ratio when determining punching shear resistance, resulting in a reduced punching shear capacity. Another design consideration was the use of a reduced modulus of rupture to better predict deflection performance. Construction of the primary concrete structure has been completed and no performance issues have been observed.

The ductility and the strength of flat plate connections with their supporting columns are influenced by the concrete strength, the thickness of the slab and the shear and the flexural reinforcements. The present paper concentrates on the important effect of flexural reinforcement in the presence or the absence of shear reinforcement.

In reinforced concrete one-way slabs, two limit states related to shear need to be checked: beam shear over an effective width at the support and punching shear on a perimeter around the load. Current code provisions are based on shear tests on heavily reinforced slender beams under point loads. The question remains if these procedures are valid for wide beams and slabs under point loads close to the support. To evaluate the shear capacity of reinforced concrete slabs and the associated effective width, a series of experiments is carried out on eight continuous one-way slabs and twelve continuous slab strips loaded close to the simple and continuous supports. Test results are compared to current code provisions and methods to calculate the shear capacity from the literature. The influence of the shear span to depth ratio, the size of the loading plate and the overall width of the specimen are discussed. From these results follows that the behavior in shear of slabs and beams is not identical. The effective slab width, used for calculating the beam shear capacity, is recommended to be based on load spreading under 45° from the far side of the loading plate towards the support.

This paper deals with concrete slab-column connections reinforced with shearbands, covering the performance under gravity and combined gravity and cyclic lateral loads. Prior and recent test results from the U.K., U.S. and Korea are summarized. The recent tests conducted at Seoul National University revealed that the shearbands were more effective in increasing punching shear resistance, deformability and energy dissipation than headed studs under the same testing conditions (e.g., flexural and shear reinforcing ratios, gravity shear ratio = ~0.45, etc.). Engaging only a few slab bars was sufficient for anchorage. The top and bottom bends appeared to play a significant role in providing shearband anchorage. For the cyclic lateral tests (Kang and Wallace, 2008; Park et al., 2011), the constant gravity load was maintained by continuously jacking up the column bottom during seismic testing of the slab-column connections. This was the same method used for all connections in each seismic test program. The details of all the testing programs and design oversights are discussed. Finally, practical applications of shearbands in North America and Australia are introduced.