Investigation of the Constitutive Model Used in Nonlinear, Incremental Structural Analyses

摘要

Nonlinear, incremental structural analysis (NISA) has been used on Corps of Engineer projects for the last decade. An integral part of the NISA methodology is the constitutive model used when performing a NISA study. This constitutive model contains age-dependent characteristics for the modulus of elasticity, autogenous shrinkage, and creep as well as a stress-strain smeared cracking relationship. Before performing a NISA study on a project, the constitutive model is typically calibrated to laboratory tests. Despite the fact that the model is calibrated against these tests, full validation of the model requires additional comparisons to data used from past NISA studies as well as data from other sources and finally a full scale test to determine if laboratory tests capture the behavior occurring in a massive concrete structure. The report contains comparisons made as part of the validation effort. Data obtained from the literature on multi-axial creep states and on creep recovery were used to evaluate the creep relationships in the constitutive model for these conditions. Comparisons are also presented between test data from a Corps of Engineers project and the data predicted by the constitutive model with respect to the smeared cracking aspect of the constitutive model. Conclusions regarding the behavior of the constitutive model are drawn, and recommendations on how to use the model are made. Revisions to the model itself are recommended as well.