پديد آورندگان :
مدبرسعيد، علي دانشگاه آزاد اسلامي واحد مراغه - گروه مهندسي عمران، مراغه، ايران , لطف الهي يقين، محمدعلي دانشگاه تبريز - دانشكدۀ مهندسي عمران، ايران , ملكي، احمد دانشگاه آزاد اسلامي واحد مراغه - گروه مهندسي عمران، مراغه، ايران
كليدواژه :
بتن مسلح , تيرهاي سراسري , آرماتور GFRP , مقطع T شكل , بازپخش لنگر , روش المان محدود
چكيده فارسي :
بدليل عملكرد بهتر در شرايط جوي شديد و خيلي شديد و خواص مناسب ديگري مانند: خنثي بودن در برابر ميدانهاي مغناطيسي، وزن كم و مقاومت بالا به نسبت فولاد، استفاده از آرماتورهاي GFRP بعنوان يك جايگزين قابل قبول براي آرماتورهاي فولادي معمولي در سازههاي بتني مسلح، رشدي روز افزون دارد. در سالهاي اخير مطالعات گستردهاي در مورد رفتار خمشي و برشي تيرهاي بتني مسلح شده با آرماتورهاي GFRP انجام شده است. رفتار الاستيك خطي مصالح FRP تا لحظه شكست، مانع لحاظ كردن بازپخش لنگر در تيرهاي ياد شده توسط آئين نامه هاي مختلف مي شود. تاكنون محققين متعددي وجود بازپخش لنگر در تيرهاي سراسري مسلح شده با آرماتور FRP با مقطع مستطيلي را مورد بررسي قرار داده اند، ولي تحقيقات زيادي روي تيرهاي سراسري با مقطع T شكل انجام نشده است. مطالعۀ حاضر يك تحقيق عددي است كه با استفاده از نرم افزار المان محدود ABAQUS انجام گرديده است. ابتدا صحت مدل سازي انجام شده در مقايسه با نتايج آزمايشگاهي صورت گرفته و نتايج آن ارائه شده است، سپس با در نظر گرفتن متغيرهايي مانند: درصد آرماتور طولي، تعداد آرماتور طولي با درصد ثابت، نسبت خاموت، فاصلۀ خاموت با درصد ثابت و فاصلۀ خاموت با قطر ثابت، وجود بازپخش لنگر و تاثير اين متغيرها روي درصد آن در تيرهاي سراسري بتني مسلح شده با آرماتور GFRP، با مقطع T شكل مورد بررسي قرار گرفته است. نتايج نشان ميدهد كه در تيرهاي ياد شده، با لحاظ كردن چند نكته ميتوان بازپخش لنگر را در تحليل و طراحي لحاظ كرد.
چكيده لاتين :
Reinforced concrete structures with standard steel rebar are vulnerable to corrosion and harsh environmental conditions, hence RC structures reinforced with fiber-reinforced polymer (FRP) rebar were commonly used these days. Du to FRP rebar’s better performance such as high strength, low self-weight, electromagnetic transparency and, as mentioned, non-corrodibility nature, using them as reinforcing bar is very widespread now. Because of financial matters, between different kinds of FRPs, GFRP is a better choice. Considering GFRP’s high strength and elastic behavior until failure, Although a large amount of reinforcement ratio is needed in composite beam components, the flexural stiffness of GFRP rebar reinforced beams is relatively lower compared to steel-RC, and more deflection and cracking are allowed in the serviceability design of these beams. Recently, shear and flexural behavior of continuous concrete beams reinforced with GFRP bars has been well investigated. Because of linear elastic behavior of GFRP materials until failure, considering moment redistribution in analysis and design of these beams is not allowed in almost all of cods and guidelines. Although many experimental and numerical researches investigated the moment redistribution in FRP-RC continuous beams with rectangular section, the behavior of these beams with T-section is almost unknown. This paper is a numerical investigation of existence and variety of moment redistribution in concrete continuous T-section beams reinforced with GFRP bars using finite element method with ABAQUS software. The verification of numerical models was done with some experimental beams, so the simulation can be used for further researches. The considering variables included the longitudinal reinforcement percentage, the number of main bars with constant bar ratio, transverse reinforcement ratio, stirrup space with constant ratio and constant bar size. For investigating mentioned parameters, 35 beams were modeled in software according to Canadian design and construction of building structures with FRP code, so 5 groups of beams were made which one beam is constant in each group. T-section beams were modeled assuming which failure happens because of concrete crashing not rebar failure. Deflection and serviceability were not interested, so bond-slippage behavior of GFRP rebar with concrete is not considered in modeling. Problem is indeterminate, so the percentage of moment redistribution was determined by comparing the reactions resulted from numerical and elastic analysis. Load-deflection and load-moment redistribution curves were used to discuss. The results show, as there is in steel-RC structures, moment redistribution exist in GFRP-RC continuous beams with T-section; however the amount of it is lower. Amount of bars between 2.5 times of balance reinforcement ratio and 3.5 times of it, in top and bottom of beam, shows the highest flexibility load and moment redistribution capacity. Increasing the number of main bars with constant reinforcement ratio and increasing the stirrup space with constant transverse reinforcement ratio reduce the moment redistribution capacity. It seems that the minimum amount of transverse reinforcement considered in Canadian code is not enough for preventing shear failure in these beams. So, with considering some points, the moment redistribution can be taken to account in analysis and design of GFRP-RC continuous beams with T-section.
