APIS - ATENA Parameter Identification Software - is an experimental parameter identification program used to determine input values of nonlinear simulations. A set of desired output values are compared to the simulation outputs and the selected optimization method is applied to provide a set of input parameters for the next iteration. Attempts to reach a solution which yields outputs closest to the desired values are carried out according to user preferences, namely the maximum number of iterations and the target error.

APIS FRC module offers an automated procedure to determine the multilinear function describing the tensile behavior of fiber reinforced concrete in ATENA models. A similar manual procedure is described in ATENA Science – GiD FRC Tutorial, including a detailed description of the ATENA material model CC3DNonLinCementitious2User used in the example.

APIS SA module provides a general inverse analysis procedure to determine values of ATENA model inputs. Given a set of desired outputs, a sensitivity analysis is performed for selected input variables, and a set of linear equations is defined and utilized in the iteration process. The sensitivities of each output to each input are calculated using FReET software and stored in a dedicated file named “SA.fre”. The error minimization function defined by the program is based on the obtained sensitivities and a Taylor expansion of outputs and inputs, which are translated to a locally linearized system. By solving the linear system, a new set of inputs is extracted and used in the next iteration.

The results presented on this website were achieved within project FV30244 "IdeMaS" by MPO TRIO3 supported by Ministry of Industry and Trade of the Czech Republic.