A finite element program development is presented for elasto-plastic piping systems subjected to severe pipe rupture blowdown forces and finite deformations. The piping consists of straight and curved elements with relatively thin walls. The effects of varying internal pressure on yielding are included but remain uncoupled from the dynamic solution process. The elasto-plastic materials are modeled as bilinear with isotropic strain hardening. An incremental flow rule associated with the Von Mises yield surface completes the constitutive laws governing these materials except for the requirement that stress rates be frame indifferent (as part of a more general requirement on constitutive equations). Frame indifference is satisfied by writing the Prandtl-Reuss equations in terms of “stretching” (or strain rate) and Jaumann flux. In the context of this paper, “large deformations” result from second order effects due to gross changes in frame geometry and due to local bending and membrane strains. The solution to the typical initial value problem representing the postulated blowdown event within a nuclear piping system consists of a step-by-step integration of a set of ordinary differential equations in the time domain. The authors have chosen the Newmark Beta method with variable integration steps for this purpose. At each integration step “correction” forces P n and H n are found by determining plastic strains and rigid body rotations at Gaussian grid points within a pipe element and then performing numerical integration over appropriate pipe volumes. At regular intervals, direction cosines of applied blowdown forces are transformed to follow the rotations of traction surfaces, and the stiffness matrix is updated. The optimal interval spacing for solution accuracy appropriate and economy is under investigation. Comparisons with solutions and experiments in the open literature will be made, wherever possible.