Liquefaction is one of the most damaging functions of earthquakes in saturated sandy soil. Therefore, clearly advancing the assessment of this phenomenon is one of the key points for the geotechnical profession for sustainable development. This study presents a new equation to evaluate the potential of liquefaction (PL) in sandy soil. It accounts for two new earthquake parameters: standardized cumulative absolute velocity and closest distance from the site to the rupture surface (CAV₅ and r_rup) to the database. In the first step, an artificial neural network (ANN) model is developed. Additionally, a new response surface method (RSM) tool that shows the correlation between the input parameters and the target is applied to derive an equation. Then, the RSM equation and ANN model results are compared with those of the other available models to show their validity and capability. Finally, according the uncertainty in the considered parameters, sensitivity analysis is performed through Monte Carlo simulation (MCS) to show the effect of the parameters and their uncertainties on PL. The main advantage of this research is its consideration of the direct influence of the most important parameters, particularly earthquake characteristics, on liquefaction, thus making it possible to conduct parametric sensitivity analysis and show the direct impact of the parameters and their uncertainties on the PL. The results indicate that among the earthquake parameters, CAV₅ has the highest effect on PL. Also, the RSM and ANN models predict PL with considerable accuracy.

In fracture mechanics, the fatigue evaluation depends on the precise provisions of the stress intensity factor (SIF), which is a quantitative factor established to evaluate the effect of stresses along the crack front. Stress intensity factor performs a definitive role in reflecting material fracture and estimating fatigue life of tubular joints. Some researchers have proposed a series of parametric equations to predict SIF values; however, it gave arguably inaccurate results. There is still a need to improve the accuracy of the SIF prediction’s equation. Thus, to overcome this shortage, this study introduced back-propagation (BP) neural network with conjunction to genetic algorithm (GA) (GA-BP) in predicting the SIF of cracked tubular T/Y-joint. To train and verify the results of the hybrid algorithm GA-BP SIFs’ database covers a wide variety of cracked tubular T/Y joints were simulated by ABAQUS and verified against experimental results. Meanwhile, the SIFs’ result produced by the GA-BP optimization method were compared with those SIF calculated from the accessible parametric equations. The comparison indicated that the GA-BP neural network optimization method is reliable, precise and capable tool in calculating the SIFs of cracked T/Y joints and it also provides higher accuracy than common methods.

Liquefaction is one of the most destructive phenomena caused by earthquakes, and it has been studied regarding the issues of risk assessment and hazard analysis. The strain energy approach is a common method to evaluate liquefaction triggering. In this study, the response surface method (RSM) is applied as a novel way to develop six new strain energy models in order to estimate the capacity energy required for triggering liquefaction (W), based on laboratory test results collected from the literature. Three well-known design of experiments (DOEs) are used to build these models and evaluate their influence on the developed equations. Furthermore, two groups of artificial neural network (ANN) and RSM models are derived to investigate the complicated influence of fine content (FC). The first group of models is based on a database without limitation on the range of input parameters, and the second group is based on a database with FC lower than the critical value of 28%. The capability and accuracy of the six presented models are compared with four existing models in the literature by using additional new laboratory test results (i.e., 20 samples). The results indicate the superior performance of the presented RSM models and particularly the second group of the models based on a limited value of FC.

Few empirical and semi-empirical approaches have considered the influence of the geology, tectonic source, causative fault type, and frequency content of earthquake motion on lateral displacement caused by liquefaction (D_H). This paper aims to address this gap in the literature by adding an earthquake parameter of the standardized cumulative absolute velocity (CAV₅) to the original dataset for analyzing. Furthermore, the complex influence of fine content in the liquefiable layer (F₁₅) is analyzed by deriving two different equations: the first one is for the whole range of parameters, and the second one is for a limited range of F₁₅ values under 28% in order to the F₁₅’s critical value presented in literature. The new response surface method (RSM) approach is applied on the basis of the artificial neural network (ANN) model to develop two new equations. Moreover, to illustrate the capability and efficiency of the developed models, the results of the RSM models are examined by comparing them with an additional three available models using data from the Chi-Chi earthquake sites that were not used for developing the models in this study. In conclusion, the RSM provides a capable tool to evaluate the liquefaction phenomenon, and the results fully justify the complex effect of different values of F₁₅.