NONLINEAR-ANALYSIS OF REINFORCED-CONCRETE SHELLS

Nonlinear finite element procedures are presented for the analysis of reinforced-concrete shell structures. Cracked concrete is treated as a n orthotropic material using a smeared rotating crack approach. The co nstitutive model adopted for concrete compression response accounts fo r reductions in strength and stiffness due to the presence of transver se cracks. The model used for concrete in tension represents the tensi on stiffening effects that significantly influence postcracking respon se. A heterosis-type degenerate isoparametric quadrilateral element is developed using a layered-element formulation, which rigorously consi ders out-of-plane shear response. Selective integration is used to avo id shear-locking and zero-energy problems. Good stability and converge nce characteristics are provided by the iterative, full-load secant st iffness solution procedure employed. Simple test elements are used to confirm the analytical procedure's ability to accurately model behavio r under conditions of membrane load, flexure, and out-of-plane shear. Plate specimens and column-slab strip specimens are used to investigat e the ability to model complex structural behavior influenced by geome tric and material nonlinearities.