I. S. T. Liu

The Gradual Formation of Hinges Throughout Reinforced Concrete Beams

ABSTRACT The rotational capacity of reinforced concrete beams is of funda-mental importance to the collapse of reinforced concrete structures. Research that started in the eighties used numerical approaches to simulate the rotational behavior using discrete and independent blocks encompassed by adjacent cracks. In this paper, these numerical approaches are taken a stage further. A numerical procedure has been developed that: allows for the interaction between the blocks along the full length of concrete beams; can cope with any number of layers of reinforcing bars; automatically predicts the occurrence of flexural cracks; and automatically allows for slip of the reinforcing bars.

MOMENT REDISTRIBUTION IN ADHESIVELY PLATED RC BEAMS AND SLABS

ABSTRACT It is common practice these days to retrofit RC beams and slabs by adhesive bonding FRP or steel plates to their surfaces. However, research has shown that these external plates can debond prematurely at relatively low strains, due to intermediate crack (IC) debonding, and in a brittle fashion. Because of these low IC debonding strains, it can be shown, through the standard use of neutral axis depth factors at ultimate, that the ability of the plated section to redistribute moment to other sections is severely limited and to such an extent that guidelines often preclude moment redistribution. This limitation may have little effect on plating RC bridges but it can, at least theoretically, severely limit the use of plating in buildings where ductility is a requirement. Tests on steel and FRP plated continuous beams have shown that moment redistribution can occur and a design procedure has been developed to determine the amount of moment redistribution for any type of plated section, such as tension face plates and side plates, and for any type of plate material, such as steel or FRP. In this paper, an analysis approach to quantify the amount of moment redistribution is described. A parametric study is then used to illustrate how the plate material and geometric properties affect moment redistribution; in particular, the study looks at the effect of using carbon FRP plates and glass FRP plates, as well as steel plates that have been designed to either debond prior to yielding or yield prior to IC debonding. In summary, the paper will show that plated sections can redistribute moment and, hence, the present restriction can be removed which should extend the use of retrofitting by plating. Furthermore, the moment redistribution analysis procedure allows the engineer the freedom to choose the properties of the plate to design for moment redistribution.