Novel fuzzy-based optimization approaches for the prediction of ultimate axial load of circular concrete-filled steel tubes

An accurate estimation of the axial compression capacity of the concrete-filled steel tubular (CFST) column is crucial for ensuring the safety of structures containing them and preventing related failures. In this article, two novel hybrid fuzzy systems (FS) were used to create a new framework for estimating the axial compression capacity of circular CCFST columns. In the hybrid models, differential evolution (DE) and firefly algorithm (FFA) techniques are employed in order to obtain the optimal membership functions of the base FS model. To train the models with the new hybrid techniques, i.e., FS-DE and FS-FFA, a substantial library of 410 experimental tests was compiled from openly available literature sources. The new model\u2019s robustness and accuracy was assessed using a variety of statistical criteria both for model development and for model validation. The novel FS-FFA and FS-DE models were able to improve the prediction capacity of the base model by 9.68% and 6.58%, respectively. Furthermore, the proposed models exhibited considerably improved performance compared to existing design code methodologies. These models can be utilized for solving similar problems in structural engineering and concrete technology with an enhanced level of accuracy

A novel TS Fuzzy-GMDH model optimized by PSO to determine the deformation values of rock material

Since determining the rock deformation directly in the laboratory is costly and time consuming, it is important to reliably determine/estimate this parameter through the use of several simple rock index tests. This study develops a new hybrid intelligent technique according to Takagi–Sugeno Fuzzy Inference System-Group Method of Data Handling optimized by the particle swarm optimization, called TS Fuzzy-GMDH-PSO for prediction of the rock deformation. The PSO role in this advanced system is to optimize the membership functions of TS Fuzzy-GMDH model for enhancing the level of prediction capacity. In this research, four rock index tests including Schmidt hammer, p-wave velocity, porosity and point load were selected and conducted in laboratory in order to establish a suitable database for prediction purposes. To demonstrate the feasibility and applicability of the advanced hybrid model, two base models of TS Fuzzy and GMDH were also modeled to forecast rock deformation. After conducting several sensitivity analyses on the mentioned models to get the highest performance capacity, their prediction levels were evaluated using some statistical indices, such as root mean square error and correlation coefficient (R). The comparative results confirmed the superiority of the TS Fuzzy-GMDH-PSO over other two models, namely TS Fuzzy and GMDH in terms of both train and test phases. It can be concluded that the TS Fuzzy-GMDH-PSO can be recommended as a powerful, capable and new model to solve the problems related to rock strength and deformation