The work carried out and the main results obtained are as follows:
•Literature review of the available physical models employed for describing RC structural behavior at the ultimate limit state.
•Review on the ability of the available nonlinear finite element analysis packages employed for predicting RC structural response.
•Development of databases from valid published test data on the behavior of RC beam, columns and joints. The databases include information concerning the behavior of 863 RC beams with rectangular cross-sections, 89 RC T-beams, 169 RC columns and 194 external beam-column joints.
•Comparison of the predictions concerning the load-carrying capacity of beam/column elements and the joint strength of exterior beam-column joints obtained from the current design codes with the test data included in the databases.
As regards flexural capacity, the comparative study concerning the RC beams revealed that, out of around 190 specimens designed to exhibit ductile behavior, over 20% failed prematurely in a brittle manner. As regards shear capacity, the comparative study revealed that the current codes of practice underestimate by about 15% on average the shear load-carrying capacity of the specimens investigated. For the case of the RC joints, the comparative study revealed that current codes cannot provide accurate predictions concerning the joint strength or the mode of failure exhibited.
•The development of ANNs capable of predicting the load-carrying capacity of beam/column elements and the failure mode and strength of beam-column joints.
The trained ANNs provide predictions concerning load carrying capacities which correlate closely with the test data. They are found capable of predicting the failure mode of beam-column joints in over 95% of the 153 cases investigated.
•Comparison of the ANNs predictions with their counterparts provided by current codes and alternative methods.
For the case of RC beams and columns the code predictions for load-carrying capacity exhibit a significant deviation from the ANN predictions, although the test data used for training the ANNs were also used for calibrating the code methods. The alternative assessment method is found to produce values of load carrying capacity and joint strength which correlate closely with the ANN values.
• Development and validation of a new structural analysis method for assessing the behavior of RC frame structures through the use of hybrid ANN-FEA models
The main feature of this method is that each structure is subdivided into portions extending between points of maximum bending moment and points of contra-flexure or consecutive points of contra-flexure (see Fig.2) equivalent to cantilevers or simply-supported beams, respectively. These portions are identical to specimens which have been extensively experimentally investigated to date. Through the proposed framework the available test data is objectively analysed and used to develop ANNs capable of predicting the behavior of individual RC members which are in turn used to develop the hybrid ANN-FEA models. Good agreement is observed between the predictions of the proposed analysis method and those obtained from nonlinear FEA and experiments for the case RC frames.
The work carried out to date has formed the subject of four articles published or under review in scientific journals and four articles presented or to be presented in Conferences. Additional articles are under preparation. A website presenting information relevant to this project (e.g. databases, a video describing the work conducted) has been setup.
