INFLUENCE OF BUILDING FORM ON WIND LOADS

Oblika objekta ima neposreden vpliv na obtežbe, ki nastanejo zaradi vetra, kateremu je objekt izpostavljen. Prav tako ima smer vetra, glede na objekt, velik vpliv na oblikovanje področij z največjimi obremenitvami. Za analiziranje vplivov vetra na objekte in konstrukcije v uporabi računski postopek po SISTEN 1991-1-4. V primeru zahtevnejših oblik objektov ali v primeru zahtevnejšega okolja, kateremu bo objekt izpostavljen, pa je zelo primerno orodje za izdelavo analize programski paket ANSYS. ANSYS omogoča izvajanje simulacij v navideznem okolju na navideznih modelih. S programskim orodjem ANSYS smo izvajali vzporedne simulacije, k računskim postopkom. Za namen analize vpliva vetra na objekt smo v osnovi uporabili enostaven objekt pravokotne oblike z enokapno streho in majhnim naklonom. Rezultate smo dobili po dveh postopkih, in sicer z računsko metodo po SIST EN 1991-1-4 in z izvajanjem simulacij v okolju ANSYS. Rezultati kažejo, da obstaja neposredna povezava med računsko metodo in metodo pridobivanja rezultatov s pomočjo simulacij. S programom ANSYS smo opravili tudi analizo vpliva izvedbe vogalov objekta na velikost obtežbe, ki nastane zaradi vetra. Pokazali smo, da že majhna sprememba oblike vogala lahko zmanjša obtežbo na površino neposredno ob obravnavanem vogalu za več kot 30%. Rezultati računske metode in rezultati simulacij v okolju ANSYS so pokazali, da je enokapna streha primerna oblika strehe, vendar je potrebno v primeru večjih hitrosti vetra izvesti dodatne ukrepe, ki povečujejo odpornost takšne strehe. Glavna težava pri izvedbi ravne strehe z majhnim naklonom je, da se na celotni površini strešine pojavijo srki, ki so precej veliki na zunanjem obodu. Upoštevati je potrebno dejstvo, da se na napušču, ki je neposredno izpostavljen udaru vetra, seštevata dva vpliva. Sešteti moramo srk na zgornji strani strehe in pritisk, ki se pojavi na spodnji strani strehe in je enak pritisku vetra na steno pod napuščem. Vse negativne vplive je možno v precejšni meri zmanjšati in to predvsem s pravilno izbiro izvedbe pokrivanja.The shape of a building has a direct influence on wind loads to which the building is exposed. Regarding the building, the direction of the wind also greatly influences the forming of the areas with maximum loads. The analyses of wind influence to buildings and structures are performed by the calculating procedure defined in SIST EN 1991-1-4. In case of more complex forms of building or in case of a more demanding environment influencing the building, a very suitable tool for making analyses is the ANSYS software. ANSYS enables the execution of simulations in virtual environment on virtual models. ANSYS software was used to execute simulations parallel to the calculating procedures. For the analysis of wind influence on a building, a simple rectangular object with a low single slope roof was used as a basis. The results were obtained with two procedures, namely with the calculating method defined in SIST EN 1991-1-4 and also with the execution of simulations in the ANSYS environment. The results obtained show that there is a direct link between the calculating method and the simulation method. Using the ANSYS programme, we have also executed the analysis of the influence of a building\u27s corner construction on the magnitude of wind loads. It has been proved that a minor change of a corner shape can reduce the wind load to the surface directly near the corner by more than 30%. The results of the calculating method and the results of the simulation method in the ANSYS environment have shown that a single slope roof is a suitable roof form. However, in the case of a greater wind speed, additional measures need to be taken in order to increase the wind resistance of the roof. The main problem in constructing a low slope roof is the fact that suction occurs on the entire surface of the roof. Moreover, the suction is considerably great at the circumference. It needs to be taken into account that two influences on the projecting roof directly exposed to wind are summed up. The suction at the upper level of the roof needs to be added to the pressure that appears on the lower side of the roof and is equal to the wind pressure on the wall under the projecting roof. All negative impacts can be considerably reduced with a proper choice of roofing execution