بررسي تاثير هندسه‌ي فرازش در بهبود عملكرد لرزه‌يي گنبد ديامتيك تك‌لايه

Study of Pellevation Geometry Effects on Improving Seismic Performance of Single Layer Diamatic Domes

در بين سازه‌هاي فضاكار، گنبدها به دليل دوام و پايداري بالا، جايگاه ويژه‌يي دارند. از آنجا كه در سازه‌هاي فضاكار، تغييرات هندسه، اصلي‌ترين عامل تعيين‌كننده‌ي مقادير كنش‌ها هستند، در اين نوشتار به بررسي اثر ايجاد فرازش و تغيير شرايط هندسي در عملكرد لرزه‌‌يي گنبد ديامتيك تك‌لايه پرداخته شده است. در اين راستا، نسبت‌هاي هندسي خيز به دهانه در گنبدهاي ديامتيك تك‌لايه‌ي ساده در يك گروه بررسي و سپس در سه گروه ديگر، به نحوي كه هندسه‌هاي مختلف پوشش داده شوند، فرازش در گنبدهاي ديامتيك تك‌لايه‌ي گروه اول‌ اعمال شده است. با انجام آناليز ديناميكي، تاريخچه‌ي زماني غيرخطي با استفاده از 3 شتاب‌نگاشتِ مناسب و مقياس‌شده براساس ضوابط استاندارد 2800، عملكرد لرزه‌يي مدل‌ها مورد بررسي و مقايسه قرار گرفته است. نتايج به دست‌آمده در اين نوشتار، نشان دهنده‌ي اثر مطلوب فرازش در كاهش وزن گنبدها و بهبود عملكرد سازه‌‌يي است، به گونه‌يي كه مي‌توان با ايجاد فرازش مناسب تا حدود 16% در وزن گنبدها كاهش داشت.

Among different types of space frame, the dome holds a special position because of its structural stability. Since changes in geometry play a key role in the structural response of space frames, in this paper, the effects of applied pellevation with different geometry on improving the seismic performance of single layer diamatic domes are studied. For this purpose, one group, including simple single layer diamatic domes with different ratios of rise to span, has been created, and then, in another three groups, different types of pellevation are applied to the first group. Each group contains five models, and the defined groups have been generated in such a way that different possible geometries have been covered. In formex algebra, during the pellevation process, a geometric object is used to deform a part of the given configuration by pushing the object upwards. In this paper, barrel pellevation, which can be easily matched to diamatic domes, is applied via implementing the BAPLE function. The computer program, Formian, is used as a tool to configure the pellevated single layer diamatic domes. The nonlinear dynamic time history analysis is performed for the defined models, and the structural behaviors of the different systems are compared with each other via frequencies and mode shapes. For non-linear time history dynamic analysis, three scaled ground motion records appropriate to the design hazard levels of the Iranian Seismic Code have been selected. Checking overall stability shows that dome deflection is the dominant design criteria, and, fortunately, it is possible to decrease the seismic deflection of diamatic domes via a change in geometry by applying proper pellevation. The results show the desirable effects on the weight reduction of pellevated domes. Structural performance has been improved, such as the weight of the dome can be reduced by about 16% via choosing proper pellevation.