Progressive collapse analysis of planar reinforced concrete frames using a 1D element with distributed non-linearity

In this paper, a highly efficient 1D discrete element is developed for progressive collapse analysis of reinforced concrete planar frames. The element takes advantage of the force-interpolation and total secant stiffness approach, as well as a non-local averaging technique adopted to maintain the objectivity of displacement and force responses. Dynamic load distribution, softening of concrete under compression, effect of mass type (consistent or lump) and catenary action of the beams are addressed. Concerning geometrical non-linearities, the strains are assumed to be small; however, the effect of transverse displacement on the axial strain is large and it is taken into account. The accuracy and efficiency of the element for static and dynamic progressive collapse assessment of the reinforced concrete frames is demonstrated through some numerical examples