ABSTRACT
This chapter deals with item and introduces a method of placing continuous steel reinforcing ties to prevent progressive collapse, and examines why ties are needed and the resulting structural mechanisms in the event of accidental loading. The best way of providing floor ties is to provide a continuous ring of reinforcement around each bay of floor slabs bounded by beams. Floor ties must span over supporting beams, either directly as a single bar. Beam ties must span past columns, either through sleeves or pass on either side of the column. In a 3D precast concrete orthogonal slab field the tie forces will act in two mutually perpendicular directions, namely along the beam as a 'beam tie' and along the slabs as 'floor ties'. The floor ties will only act in the vicinity of the beam where the bearing is lost, which could be estimated as L/2 from the ends.
