Limited research work exists on assessment of punching shear of reinforced concrete (RC) flat slabs made with blended cement incorporating ground-granulated blast-furnace slag (GGBS). This research is aimed at analyzing the punching shear strength of RC flat slabs cast from blended cement having GGBS in different proportions as partial replacement of cement. Four flat slabs supported on the ends were tested under column load such that one flat slab was cast from normal concrete with no GGBS and the remaining three flat slabs were cast with 30, 40, and 50% replacement of cement by GGBS. Experimental punching shear, midspan deflections, strain in the steel bars, and cracking pattern of the slabs were determined. The results of punching shear of flat slabs from the tests were compared with the nominal punching shear capacities proposed by BS 8110, BS EN1992-1-1/EC2, and ACI 318. The provisions of these building codes for the punching shear were observed as safe and conservative for the RC flat slab made from blended cement incorporating GGBS.

An experimental study was carried out on fiber-reinforced glass aggregate concrete slabs under a central patch load. The slab specimens were reinforced either with randomly distributed short fibers or with continuous fiber mesh with equal fiber volume ratios. The influences of fiber type, form and volume ratio on the two-way bending behavior, and punching shear capacity of the glass concrete slab were investigated. Test results revealed that fiber mesh is decidedly more effective in bending than randomly distributed fibers; however, randomly distributed fibers are somewhat more effective in punching shear. The shape and location of the critical punching shear perimeter is independent of fiber type, form, and volume ratio. But crushed glass aggregate has some influence on both strength and failure mode of the slabs.

Extensive accelerated aging tests were conducted on polymer composite bars reinforced with aramid (Technora®) fibers. Aramid fiber-reinforced polymer (AFRP) bars exhibited desirable durability characteristics under a broad range of accelerated weathering effects. They also exhibited satisfactory bond strength and dowel action in concrete. A bridge deck reinforced with AFRP bars was designed with due consideration given to the punching shear mode of failure. The design procedures were verified through scaled laboratory tests. The bridge deck reinforced with AFRP bars was constructed in Michigan. The construction and cost attributes of aramid FRPs were evaluated in this field project.

The failure load is several times greater than the wheel loads of heavy trucks and, thus, it is accepted that the ultimate load-carrying capacity of bridge decks are safe enough to resist wheel loads in service state. However, many bridge decks in Korea have failed locally due to repeated and moving traffic loading. Therefore, the bridge decks, in regards to the fatigue problem, should be designed to ensure adequate safety and durability during design life. Previous researchers who investigated the fatigue behavior of bridge decks were concerned mainly with the following topics: reinforcement ratio; reinforcing methods (orthotropic and isotropic); and loading methods (fixed pulsating loads, stepwise moving pulsating loads, and simulated moving wheel-load). These tests were conducted at the center or centerline of the bridge deck panels, which were bounded by girders and diaphragms, and, thus, the effects of the loading positions were not considered. For this reason, the fatigue life of a bridge deck is usually expressed as a function of the punching shear strength at the center of the deck panel. If the center of the deck panel is not a critical point for fatigue loading, additional fatigue tests would be needed to investigate the position of the bridge deck, which is more critical for fatigue loading than the center of the panel. This paper is aimed at investigating the variations in punching shear strength and fatigue strength of composite bridge decks at various positions. Test results are compared with previous test results, especially results obtained by Hewitt. The experimental tests were conducted on one-third-scale model deck slabs, which were modeled to simulate a typical composite bridge deck. Punching tests were conducted at six positions, and three pulsating test positions were selected among the punching test positions. These loading positions were carefully selected based on the relative magnitude of the sectional forces (compressive in-plane forces and shear forces) in the slab, which were obtained by three-dimensional finite element analysis.

This paper describes a test to failure of a two bay by two bay continuous, unbonded post-tensioned flat plate designed in accordance with the provisions of ACI 318-95, except that no supplementary bonded reinforcing steel was provided. The prestressing tendons were uniformly distributed in one direction and banded in span/3 column strips in the other direction. In both directions the average prestress on the concrete was 3.5 MPa. The dimensions of each bay were 2.7 m by 2.7 m, the slab thickness was 89 mm, and the mean concrete cylinder strength was 44 MPa. The load was applied monotonically until punching shear occurred at an edge column on the side parallel to the banded tendons. The failed column was shored and the slab reloaded until punching shear occurred at the interior column. Finally both the edge column and the interior column were shored and the slab loaded until a corner column failed. All the punching shear failures were violent and without warning. The literature was reviewed to locate experimental results of punching shear tests for isolated prestressed concrete flat plates, continuous prestressed flat plate systems and tests of flat plate column connections under shear and moment transfer. The measured punching strength capacities were compared to those calculated using the provisions of ACI 318-95, BS 8110-85, and a proposed method.