Abstract The present work aims to study the nonlinear behavior of reinforced concrete structures via Refined Plastic Hinge Method (RPHM). Pseudo-springs are used at the finite element ends, where the gradual loss of stiffness is determined by the combination of the normal force and bending moment (NM) in the cross section. The limiting of the uncracked, elastic and plastic regimes is done in the NM diagram. The concrete cracking is explicitly simulated with two approaches to calculate the effective moment of inertia of the cross section. The displacement-based formulation is referenced to the co-rotational system and coupled with continuation strategies to allow to overcome the possible critical points in the equilibrium paths. For validation of the numerical simulations, the results found with the proposed formulation are confronted with experimental and numerical data present in literature.

Este trabalho investiga a resposta de dois pórticos planos de concreto armado à perda de uma coluna e sua capacidade de resistir ao colapso progressivo. A análise não linear dinâmica é realizada utilizando um elemento de viga baseado na teoria de Euler/Bernoulli com seção transversal discretizada em camadas. A não linearidade física é representada através de relações constitutivas unidimensionais, incluindo efeitos viscoplásticos. A não linearidade geométrica é incorporada através de uma formulação corrotacional. Os pórticos foram projetados de acordo com os requisitos mínimos das normas de projeto/construção de estruturas de concreto armado Europeias (fib [1-2], Eurocode 2 [3]) e Brasileiras (NBR 6118 [4]). As combinações de carregamento consideradas na análise de colapso progressivo estão de acordo com DoD [5]. O trabalho verifica se os requisitos mínimos das normas consideradas são suficientes para garantir a robustez e a segurança estrutural e aponta também as diferenças mais relevantes em termos da suscetibilidade dos pórticos ao colapso progressivo.

This work investigates the response of two reinforced concrete (RC) plane frames after the loss of a column and their potential resistance for progressive collapse. Nonlinear dynamic analysis is performed using a multilayered Euler/Bernoulli beam element, including elasto-viscoplastic effects. The material nonlinearity is represented using one-dimensional constitutive laws in the material layers, while geometrical nonlinearities are incorporated within a corotational beam formulation. The frames were designed in accordance with the minimum requirements proposed by the reinforced concrete design/building codes of Europe (fib [1-2], Eurocode 2 [3]) and Brazil (NBR 6118 [4]). The load combinations considered for PC analysis follow the prescriptions of DoD [5]. The work verifies if the minimum requirements of the considered codes are sufficient for enforcing structural safety and robustness, and also points out the major differences in terms of progressive collapse potential of the corresponding designed structures.