Non-stationary dynamic structural response to thunderstorm outflows

Wind loads on structures are commonly described as stationary phenomena that occur in neutral atmospheric conditions at the synoptic scale with velocity profiles in equilibrium with the atmospheric boundary layer. Nevertheless, structural systems can be also affected by thunderstorm outflows, which are non-stationary local phenomena at the mesoscale that occur in convective conditions with totally different velocity profiles with respect to synoptic winds. This paper presents a non-stationary probabilistic model that describes the wind velocity fluctuations experienced during a thunderstorm in order to estimate its effects on the dynamic structural response. The model is first calibrated on a typical thunderstorm recorded in the north-west italian coast and it is used to generate virtual time histories in a Monte Carlo simulation approach. The potential influence of the wind load non-stationary features on the peak structural response is investigated using single degree of freedom parametric analysis and statistical estimation.     

Robust optimization of concrete strength estimation using response surface methodology and Monte Carlo simulation

A new approach is proposed for the robust optimization of concrete strength estimation using response surface methodology and Monte Carlo simulation. The essence of the suggested procedure lies in the reliable prediction of concrete strength as a simple function of unit mass, water/cement ratio, age and superplasticizer content. The derived model provides sufficiently accurate results for the calibration and verification phases, the latter of which is conducted using data that were not used for model development. The results of additional analysis indicate that residuals in the calibration and verification stages have a normal distribution. Is its also shown that the uncertainty of estimated coefficient values has a statistically insignificant effect on concrete strength, confirming the reliability of the proposed model. Moreover, analysis of the effect of laboratory measurement errors indicates the robustness of concrete compressive strength against the variation in measured parameter values.