Wind Action Analysis on Different Structures of Photovoltaic Systems Installed on Flat Rooftops of Buildings

This paper aims to analyze the velocities and pressures that the wind exerts in three different configurations of photovoltaic systems installed on flat rooftops of buildings. The Finite Element Method is used to perform thirty computer simulations for different wind speeds and directions. From the obtained results analyzes of the maximum and minimum values of pressure and velocity on the surface of the structures and the building are performed. Thus, it is possible to identify the necessary precautions regarding materials and installation so that the structure is safe and does not result in accidents and material and economic damage.

Accurate Correlation Modeling between Wind Speed and Bridge Girder Displacement Based on a Multi-Rate Fusion Method

Wind action is one of the environmental actions that has significant static and dynamic effects on long-span bridges. The lateral wind speed is the main factor affecting the lateral displacement of the main girder of the bridge. The main objective of the paper is to use the improved multi-rate fusion method to correct the monitoring data so that accurate correlation modeling of wind speed-displacement can be achieved. Two Kalman gain coefficients are introduced to improve the traditional multi-rate fusion method. The fusion method is verified by the results of simulated data analysis in time domain and frequency domain. Then, the improved multi-rate fusion method is used to fuse the monitoring lateral displacement and acceleration data of a bridge under strong wind action. The corrected lateral wind speed and displacement data is further applied to establish the correlation model through the linear regression. The improved multi-rate fusion method can overcome the inaccuracy of the high frequency stage of a Global Positioning System (GPS) sensor and the low frequency stage of acceleration sensor. The correlation coefficient of wind speed-displacement after fusion increases and the confidence interval width of regression model decreases, which indicates that the accuracy of the correlation model between wind speed and displacement is improved.

Monitoring of the “Twin Towers” of Bologna in Italy

In this contribution, in which the preliminary outcomes on the monitoring of the “Garisenda” Tower are discussed, there are also briefly presented the results already obtained from the monitoring of the “Asinelli” Tower, carried out a few years ago by the authors. The two medieval towers, recognized as the “twin towers” of Bologna, represent a remarkable symbol of the city and of Italian Architectural Heritage. The Asinelli Tower was built during the period 1109–1119. It rises to a height of 97.30 m above the ground, and shows a deviation from verticality of 2.38 m. The Garisenda Tower, built around the same time, is much smaller (48 m) but with a steeper leaning (3.22 m) due to an early and more marked subsidence of soil and foundation. The data collected during the AE monitoring period of the Asinelli Tower were analyzed to evaluate the damage progress in a certain region of the masonry structure and correlate it with other considered phenomena, such as the influence of vehicle traffic, seismic activity, and wind action. To arrive at a comprehensive and objective evaluation of the structural conditions of the Garisenda Tower, whose monitoring is still ongoing, the results obtained by the AE technique were supplemented with data obtained from other zones of the structure, subject to different stress–strain conditions or by means of other techniques. Thanks to this arrangement, the AE signals distribution is related to the data measured by optical cables and a seismometer to obtain an objective correlation between the actions generated by the environment and the tower damage.

ESTIMATING THE INFLUENCE OF THE WIND EXPOSURE ON THE MOTION OF AN EXTINGUISHING SUBSTANCE

One of the tasks to be solved when deploying fire extinguishing systems is to determine the range of the fire extinguishing agent supply to the combustion center. This problem is solved using data on the trajectory of the fire-extinguishing agent in the combustion center. The presence of wind impact on the process of supplying a fire extinguishing agent will lead to a change in its trajectory. To take into account wind impact, it becomes necessary to assess the result of such impact. Using the basic equation of dynamics for specific forces, a system of differential equations is obtained that describes the delivery of a fire extinguishing agent to the combustion center. The system of differential equations takes into account the presence of wind impact on the movement of the extinguishing agent. The presence of wind action is taken into account by the initial conditions. To solve such a system, the integral Laplace transform was used in combination with the method of undefined coefficients. The solution is presented in parametric form, the parameter of which is time. For a particular case, an expression is obtained that describes the trajectory of the supply of the extinguishing agent into the combustion center. Nomograms are constructed, with the help of which the operative determination of the estimate of the maximum range of the fire-extinguishing agent supply is provided. Estimates are obtained for the time of delivery of a fire-extinguishing agent to the combustion center, and it is shown that for the characteristic parameters of its delivery, this value does not exceed 0.5 s. The influence of wind action on the range of supply of a fire extinguishing agent is presented in the form of an additive component, which includes the value of the wind speed and the square of the time of its delivery. To assess the effect of wind impact on the movement of the fire extinguishing agent, an analytical expression for the relative error was obtained and it was shown that the most severe conditions for supplying the fire extinguishing agent to the combustion center, the value of this error does not exceed 5.5%. Taking into account the wind effect when assessing the range of supply of a fire-extinguishing agent makes it possible to increase the efficiency of fire-extinguishing systems due to its more accurate delivery to the combustion center