ارزيابي مقاومت و شكل پذيري ساختمانهاي بتن مسلح كوتاه

Siesmic Assessment og Ductility and Strength Capacities of Low-Rise R. C. Buildings

در اين مقاله يك روش تحليلي براي ارزيابي ايمني لرزه‌اي ساختمانهاي بتني مسلح كوتاه و كم ارتفاع ارائه مي‌شود. در اين روش، ارزيابي براساس مشخصه نيرو – جابه جايي طبقه اول يا ضعيفترين طبقه انجام مي‌گيرد. معيار ارزيابي ايمني سازه براساس دو پارامتر مقاومت و شكل پذيري در حالت زلزله قوي (PGA=0.3 g) و زلزله شديد (PGA=0.45 g) استوار است. مكانيزم شكست سازه به صورت خمشي، برشي و برشي – خمشي طبقه‌بندي مي‌شود. ارزيابي ايمني در پنج گام متوالي انجام مي‌گيرد كه عبارت‌اند از: الف – مدل سازي سيستم سازه‌اي، ب – تعيين مدل تحليلي غيرخطي طبقه، ج – ارزيابي ايمني مقاومت، د – ارزيابي ايمني شكل پذيري و ه‍ - تركيب ارزيابي ايمني. نحوه ارزيابي براساس يك ماتريس معيار پيشنهاد شده استوار است.

This paper presents a methodology for the assessment of ductility and strength capacities in low-rise buildings. This method utilizes the characteristics of force-displacement for the lowest story level or considers the weakest story in any given low-rise building for its primary analysis. Calculations are based on two levels of earthquake motions, namely strong earthquakes (PGA=0.3 g), and very strong earthquakes (PGA=0.45). Failure mechanism for the structure is established based on three criteria which are: a) bending mode, b) shear mode, and c) shear-bending mode. Evaluation is then performed using a five step procedure starting with a: modeling the building, b) developing the non-linear properties of the model, c) strength calculations, d) ductility calculations, and finally, e) assessing the safety of the building under consideration. All these evaluations are performed based on a matrix format, which simplifies the whole procedure. Developed equations and step-by-step procedure are presented and described in this paper Satisfactory results are obtained from the use of the method developed. Keywords: Strength, Ductility, Failure mechanism, Low-Rise R. C. Buildings