Influence of reinforcement arrangement in flexural fire behavior of hollow core slabs
Abstract This paper describes standard scale fire tests conducted on four precast prestressed hollow core slabs configurations under flexure. The influence of the reinforcement arrangement was investigated using two test parameters: the average axis distance (from 30.1 to 46.7 mm), and the type of reinforcement (5 mm diameter wires and 9.5 mm diameter strands). An ISO 834 standard fire was applied maintaining the load level in a four-point test arrangement constant. The results presented different failure mechanisms, types of cracks, spalling patterns, and fire resistance ratings and it was shown that wires displayed optimal behavior as opposed to strands. A comparison was carried out with the current verification methods provided in Eurocode 2 part 1–2, and showed that verification methods tend to overestimate the calculation of fire resistance when both wire and strands are moved away from the exposed surface.
Factors governing the shear response of prestressed concrete hollowcore slabs under fire conditions
Abstract This paper presents results from numerical studies on the effect of critical factors governing the shear response on prestressed concrete (PC) hollowcore slabs exposed to fire. A validated three dimensional finite element model is applied for evaluating failure of fire exposed prestressed concrete (PC) hollowcore slabs under different limiting states, including through shear. This model accounts for temperature induced property degradation in concrete and prestressing strands, cracking in concrete, varying fire exposure, loading and restraint conditions. The factors varied in the parametric study include, slab depth, load level, loading pattern, axial restraint, level of prestressing, and fire scenario. Results from parametric studies show that slab depth, load level, loading pattern, axial restraint, level of prestressing and fire scenario have significant influence on the fire response of PC hollowcore slabs, and failure under these conditions can occur through shear limiting state prior to reaching flexural limiting state. Results from parametric studies are further utilized to propose a simplified approach for evaluating shear capacity PC hollowcore slabs under fire conditions.
Code modelling of reinforced-concrete deep beams
Code provisions for shear design of deep beams have commonly developed from limited test results. There are also very few studies on the validity of shear-carrying capacities of concrete and shear reinforcement in code provisions including strut-and-tie models. The present study investigates the effect of different parameters on the shear-carrying capacities of concrete and shear reinforcement in four code provisions: ACI 318-99 and CIRIA Guide 2 for empirical formulae, and ACI 318-05 and Eurocode (EC) 2 for strut-and-tie models. A comprehensive database having a total of 448 simple and 73 continuous deep beam test results was compiled and compared with the code provisions. Different statistical parameters to measure the safety and accuracy of code provisions are also presented for various web reinforcement arrangements. Code provisions generally fail adequately to capture the effect of different parameters on the shear capacities of concrete and shear reinforcement in deep beams, indicating that shear ca...