توسعه روش اجزاء مجزا برای تحلیل غیرارتجاعی اعضاء بنایی غیرمسلح

هدف از این تحقیق توسعه رویکرد ریز مدلسازی برمبنای روش اجزای مجزا (بلوک صلب و فنر)، برای شبیه‌سازی رفتار داخل صفحه سازه‌های بنایی آجری غیرمسلح است. به منظور ارزیابی ترک‌خوردگی در آجر از فرضیات ترک دو جهته و برای رفتار پس از آن، از ایده روش ترک پخشی ثابت استفاده شده است. همچنین مشخصات فنرهای نرمال و برشی شبیه‌سازی کننده رفتار ملات و اندرکنش مابین آن با آجر، بطور مجزا از هم با ارزیابی میزان بازشدگی ترک و تغییرشکل برشی در سطح ترک تعیین می‌شوند. جهت ارزیابی میزان تنش برشی در فنرهای برشی از معیار موهرکولمب استفاده می‌شود. الگوریتم محاسباتی و نرم‌افزار توسعه یافته، تشریح و مورد اعتبارسنجی قرار می‌گیرد. مقایسه نتایج تحلیلی و آزمایشگاهی حاکی از آن است که برنامه توسعه یافته از قابلیت مناسبی برای ارزیابی رفتار غیرخطی سازه‌های بنایی به همراه مکانیزم‌های مختلف مودهای شکست و الگوهای ترک‌خوردگی برخوردار است.

Development of discrete element method for nonlinear analysis of unreinforced masonry members

One of the oldest and most durable building materials used for a large number of ancient structures by mankind is the masonry material. Few maintenance costs of masonry building, as well as its proper resistance to fire, have caused to be the boost building materials nowadays. Two major modeling approaches for simulating the behavior of masonry members are micromodeling (heterogeneous model) and macromodeling (homogeneous model). In the micromodeling approach, the failure mechanisms and cracking pattern are precisely determined; but because of the required specifications and details, it is considered as a sophisticated modeling approach. In this study, the main purpose is to develop micromodeling approach based on a discrete element method (i.e. rigid block and spring method) for simulating inplane behavior of unreinforced brick masonry buildings. For modeling each brick masonry wall in this paper, the masonry unit is defined which is consisted of just one rigid block in the transverse direction and four blocks in the horizontal direction with two different types of springs. This unit represents, in fact, two bricks and connecting mortar in real condition. According to the assumption of the rigid block and spring method, the properties of the normal and shear springs are considered independently. In this situation, it is not practically possible to accurately estimate the behavior of masonry member. In order to model cracking in brick, the twoway crack hypothesis and for subsequent behavior in each masonry unit, the idea of fixed smeared crack approach is implemented in this research. The properties of the normal and shear springs, simulating behavior of the mortar and the brickmortar interaction, are determined separately by estimating the cracking opening and shear displacement in the crack surface. The MohrCoulomb criterion is used to evaluate the behavior of mortarbrick interface. The computational algorithm and developed FORTRAN code are described and validated. Comparison of analytical and experimental results showed that the developed program by introducing the smeared crack approach and the assumed behavioral models of the masonry material is capable of accurately evaluating the nonlinear behavior of masonry structures, along with different failure mechanisms and cracking patterns.