Abstract




 
   

IJE TRANSACTIONS B: Applications Vol. 30, No. 11 (November 2017) 1388-1397    Article in Press

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  STIFFNESS-BASED APPROACH FOR PRELIMINARY DESIGN OF FRAMED TUBE STRUCTURES
 
R. Rahgozar, A. Alavi and P. Torkzadeh
 
( Received: April 09, 2017 – Accepted: September 08, 2017 )
 
 

Abstract    A parametric formulation for preliminary design of tubed-system tall buildings, in which some optimality criteria and practical constraints are considered, is presented. Here, a minimum compliance optimization formulation, developed by other researchers, is applied to a framed-tube structure. The tube behavior is modeled as a cantilevered box beam. Independent variable in this problem is thickness of the box, and a formulation for its optimal value is proposed. The challenge in this research was treatment of the lower bound constraint on thickness in an analytical manner. To deal with this constraint, a critical height parameter (CH) is introduced, and the design domain is divided into two zones of constant thickness (CT) and constant curvature (CC). This definition allows for computation of optimal thickness distribution along the structure through an analytic dimensionless equation. Different static loading patterns are considered; including the concentrated, uniform, triangular and quadratic forms. A numerical example is presented to demonstrate the ease of the proposed method in application, and the analysis results are presented by charts to validate the efficiency of it.

 

Keywords    Structural Optimization, Tall Building, Tube System, Stiffness Distribution, Preliminary Design

 

چکیده    یک فرمولبندی پارامتریک جهت طراحی سیستمهای لولهای در سازه های بلند، با در نظر گرفتن بعضی معیارهای بهینه سازی و قیود کاربردی، ارائه شده است. مساله مینیمم سازی نرمی، که قبلاً توسط بعضی محققین ارائه شده است، بر یک سیستم لولها ی اعمال می شود. رفتار سازه به صورت یک کنسول با مقطع قوطی مدل خواهد شد. متغییر مستقل در این فرمولبندی ضخامت قوطی معادل انتخاب شده است و مقدار بهینه آن ارائه خواهد شد. چالش پیش رو در این تحقیق حل مساله مقید به قیدحداقل ضخامت، با یک رویکرد تحلیلی، بوده است. در برخورد با این قید، پارامتری به نام ارتفاع بحرانی معرفی شده است که محدوده طراحی را به دو ناحیه ضخامت یکنواخت و انحنا یکنواخت تقسیم میکند. استفاده از این پارامترها امکان محاسبه ضخامت بهینه در ارتفاع سازه را در قالب یک فرمولبندی تحلیلی و بی بعد فراهم خواهد کرد. الگوهای بارگذاری استاتیکی مختلفی شامل بارگذاری متمرکز، یکنواخت، مثلثی و درجه دو مدنظر قرار گرفته اند. جهت نشان دادن سادگی روش پیشنهاد شده در عمل، یک مثال عددی ارائه شده است و برای صحت سنجی روش، نتایج تحلیل توسط چند نمودار ارائه خواهد شد.

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