Implementation and Verification of an Advanced Bounding Surface Constitutive Model

Abstract

The description of the mechanical behavior of loose saturated sandy soils under large cyclic loading represents a complicated task in earthquake geotechnical engineering because of the possible occurrence of liquefaction. The physical and numerical reproduction of this phenomenon is of great support for the protection of the built environment and the assessment of new constructions. To this end, a large number of constitutive models were developed over the years and integrated into computational platforms to describe the soil response to seismic actions. The present paper deals with the implementation and testing of the constitutive model developed by Papadimitriou and Bouckovalas (2002) into the OpenSees environment with the aim of investigating its performance at the element level. The model provides some enhancements with reference to the previous common elastoplastic models, such as a non-linear elastic hysteretic Ramberg-Osgood formulation, and an empirical index that accounts for the fabric evolution. The reliability of the implementation is analyzed through the simulation of drained and undrained, cyclic and monotonic laboratory tests from literature, regarded as a benchmark for the verification and validation of the constitutive model. Overall, the implementation procedure produced satisfactory results and the OpenSees potential in hosting user-defined codes is demonstrated.