Load-induced cracking and failure of concrete deck slabs in girder-slab type bridges

An experimental study was conducted on three different groups of girder-slab type, reinforced concrete deck panels, to investigate the pattern of crack formation, crack growth and overall failure mode. Areas of study included (i) the influence of distribution steel on crack pattern and crack growth under a simulated moving wheel load; (ii) critical orientation and nucleation of cracks in panels weakened by a flaw in the form of conical inserts; and (iii) mode of failure and ultimate capacity of deck panels with varying amounts of reinforcement steel and different load areas.;The study indicated that with higher amounts of distribution steel, finer cracks spread over a larger area are produced. The flexural capacity of a deck slab of girder-slab type bridge is enhanced to an appreciable degree due to support restraints. No significant advantage is achieved by increasing the amount of steel. A hypothesis has been advanced that impairment of punching capacity occurs only when (i) the cracks developed join to form a closed envelop (a flawed zone); (ii) the crack surface geometry bears a critical orientation with regard to wheel load and has reached a critical height through the slab thickness; and (iii) the closed boundary of this flawed zone at the bottom of the slab is greater than that of the wheel print. All reinforced panels failed in punching shear type failure.