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Article
STRENGTHENING OF CONCRETE BEAMS WITH PRESTRESSED FRP REINFORCEMENTS

Author: Suhaib Sabah Abdulhameed
Journal: Journal of Engineering and Sustainable Development مجلة الهندسة والتنمية المستدامة ISSN: 25200917 Year: 2019 Volume: 23 Issue: 1 Pages: 13-25
Publisher: Al-Mustansyriah University الجامعة المستنصرية

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Abstract

Strengthening of reinforced concrete beams with prestressed Fiber Reinforced Polymer (FRP) sheets showed to be efficient in enhancing the serviceability of the strengthened concrete beams. Yu et al.'s develop a mechanical prestressing device to prestress FRP sheets to strengthen reinforced concrete members. Yu et al. s experimental results showed that this device overcome the shortcomings associated by using the previously developed prestressing devices. In this research program Yu et al.'s mechanical device was modified to increase the efficiency of it by using light weight material to reduce the additional weight on the strengthened beams caused by the prestressing device in addition, the end anchorage plates were installed vertically rather than horizontally to extend the prestressed FRP sheets to the end regions of the member where high shear stress occurred. This modification in the end anchorage regions is efficient to reduce the possibility of the premature debonding failure. A numerical analysis by using ANSYS (R14.5) computer program was used to simulate the prestressing device. Numerical results showed that using aluminum material is efficient to produce a prestressing mechanical device. The maximum stresses and deflection that generated in the pretressing device upon prestressing Carbon Fiber Reinforced Polymer (CFRP) sheet (51% of the ultimate tensile stress in the CFRP) to strengthen 22.5m concrete beam are 46MPa and 83mm respectively. A theoretical formula was derived based on geometric relations of the prestressing system and the deformed CFRP sheet. It was used to predict the prestressing level in the CFRP sheet. Theoretical results showed that the percentage difference between Yu et al.'s formula and the derived formula is about 1%. This value changes based on the prestressing level in CFRP sheet and the length of the strengthened beam. The theoretical prediction of prestressing level in the CFRP sheet agreed well with the experimental results.


Article
Nonlinear Analyses of Composite Preflex Steel Beams Encased in Concrete

Authors: Yousif S. Jafar --- Raad K. Al-Azawi
Journal: Journal of Engineering مجلة الهندسة ISSN: 17264073 25203339 Year: 2009 Volume: 15 Issue: 3 Pages: 3868 -3890
Publisher: Baghdad University جامعة بغداد

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Abstract

In the present study, a nonlinear three-dimensional finite element analysis has been used to predict the load-deflection and moment-rotation behaviors of composite encased beams consisting of preflex steel sections using the finite element computer program (ANSYS V. 10). Composite encased beams are analyzed and a comparison is made with available experimental moment-rotation curves, good agreement with the experimental results is observed. Camber of steel section is introduced on the steel section of the composite beams encased in concrete. It is found that using of preflex section can increase the ultimate load capacity of the composite encased beam by relatively (15%) and also it is found that rotations are nearly (65% to 80%) the rotations of the same beam without preflex steel section. Parametric studies have been carried out to study the increasing of the moment-carrying capacity due to the use of encased concrete for the laminated partially encased beams; meanwhile the slip along the composite partially encased beams length is studied. The strain distributions along the steel section and encased concrete depth are also examined. Poisson’s ratio of concrete, the effect of cambering of steel-section and the effect of mesh refinement are also investigated.

أستخدم في الدراسة الحالية, طريقة العناصر المحددة للتحليل اللاخطي ثلاثي الابعاد و ذلك لغرض تحري علاقة منحنى كل من الحمل - الهطول و كذلك العزم - الدوران للعتبات المركبة و التي تحتوي على عنصر فولاذي مثني مغلف بالخرسانة وباستخدام برنامج العناصر المحددة للتحليل الانشائي الـ(ANSYS V. 10). تم تحليل العتبات المركبة ذوات المقاطع المغلفة و تمت مقارنة نتائج منحنيات العزم –الدوران مع النتائج العملية المتوفرة, تم ملاحظة توافق جيد بين النتائج المستحصلة من البرنامج و النتائج العملية. تم توليد تحديب (أنثناء) في المقطع الفولاذي للعتبات المركبة المغلفة بالخرسانة. لقد لوحظ بأن استخدام المقاطع المثنية في العتبات المركبة و المغلفة بالخرسانة يؤدي الى زيادة قابلية تحمل تلك العتبات بمقدار (١٥٪), و كذلك لوحظ بأن الدوران يتراوح مابين (٦٥٪ الى ٨۰٪) من الدوران للعتبات التي تحتوي على مقاطع مثنية. تم دراسة تأثير وجود الخرسانة المغلفة على زيادة قابلية تحمل العزوم للعتبات القشرية المركبة و المغلفة جزئياً بالخرسانة, في تلك الاثناء تم دراسة التزحلق الذي يحدث في سطح الاتصال و على طول العتب للعتبات المركبة أيضاً. بالاظافة الى ذلك تم دراسة نمطية توزيع الانفعالات على العمق الكامل للمقاطع الفولاذية و كذلك الخرسانة المغلفة. و اخيراً, تم التحقق من تاثير كل من (Poisson’s ratio), مقدار تحدب (ثني) المقطع الفولاذي و مقدار نعومة (دقة) النموذج المعمول بالـ(ANSYS) على قابليات تحمل العتبات المركبة.

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