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Article
STRUCTURAL BEHAVIOR OF REACTIVE POWDER CONCRETE VOIDED CYLINDRICAL SHELL SEGMENTS

Authors: Ashraf Abdulhadi Alfeehan --- Fatima Ismail Al-Zubaidi
Journal: Journal of Engineering and Sustainable Development مجلة الهندسة والتنمية المستدامة ISSN: 25200917 Year: 2018 Volume: 22 Issue: 2 (Part-5) Pages: 30-40
Publisher: Al-Mustansyriah University الجامعة المستنصرية

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Abstract

Voided cylindrical shell is a sustainable reinforced concrete roof system. Two directions of the voids system with two types of the voids shape in each direction had been used in this experimental work. Circular and squared void shapes used as continuous voids in the uniaxial direction while spherical and cubic void shapes used as separate voids in the biaxial direction. The diameter of the circular or spherical void is (70mm) and an equivalent side length of about (62.5mm) was used for the squared or cubic voids. The experimental variables were included the type of the shell, direction of the voids, shape of the voids and a number of the steel reinforcing layers (bottom or top and bottom) . The cylindrical shells tested as simply supported under one-point load at the crown of the shell. By (37%) maximum reduction in the concrete volume, the ultimate load capacity decreased by (35%). As well as, use of the voids in the biaxial direction improved the structural behavior in comparison with the use of voids in the uniaxial direction as a hollow core section. The use of square section or cubic void shape gave a better structural performance than the use of circular section or spherical void shape in both directions.


Article
STRUCTURAL BEHAVIOR OF VOIDED NORMAL AND HIGH STRENGTH REINFORCED CONCRETE SLABS

Authors: Hayder T. Nimnim --- Zahraa M. J. Zain Alabdeen
Journal: KUFA JOURNAL OF ENGINEERING مجلة الكوفة الهندسية ISSN: 25230018 Year: 2019 Volume: 10 Issue: 2 Pages: 1-11
Publisher: University of Kufa جامعة الكوفة

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Abstract

The intent of this paper is to study the structural behavior of voided normal and high strength reinforced concrete two-way slabs. Voided slab is a hollow core slab which has an advantage of reducing self-weight by reducing concrete mass within the center zone of the slab section. The experimental program included testing of twelve simply supported slab specimens with dimensions of (1100 x 1100 x 100) mm, and they were subjected to vertical four patch loads. Many parameters were included, such as shape of voids (spherical and cubic), type of concrete strength (normal of 30 MPa strength and high of 60 MPa strength), and ratio of steel reinforcement (0.002, 0.0026). In addition, they have different values of dimension of void to slab thickness (D/H) ratio (0.5, 0.6 and 0.65). The experimental results showed that the use of voided slabs tends to save in self-weight up to 21.6%. The use of spherical voids in voided slabs is more effective than cubic voids due to cracking and ultimate loads capacity and the structural behavior. The use of voided slabs led to reducing the first cracking load in a range of 15%-62% and 5%-40% for high and normal strength, respectively. Also, using voided slabs tended to reduce the ultimate load capacity in a range of 8%-26% for balls and 9%-48% for cubes. Using high strength concrete in voided slabs led to reducing the crack width in a range of 18.2%27.8% for voided slabs (65 mm ball shapes). Decreasing the size of voids led to reducing the deflection for the same stages of load in a range of 20%-35.7% for high strength voided slab (ρ= 0.20% ball shapes) specimens. Increasing the reinforcement ratio from 0.2% to 0.26% led to reducing the deflection in a range of 1.6%-35.9% for high strength voided slab (ball shapes D=60mm) specimens.


Article
Improving The Voided Reinforced Concrete Beams Behavior by Strenthining The Compression Zone Concrete Using Polyvinyl Alcohol

Author: Nabeel Hasan Ali Al-Salim
Journal: Journal of University of Babylon مجلة جامعة بابل ISSN: 19920652 23128135 Year: 2018 Volume: 26 Issue: 3 Pages: 307-317
Publisher: Babylon University جامعة بابل

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Abstract

Determining dimensions of continuous RC beam depend on the critical span. Practically, changing the dimensions of others spans is difficult. So that, this work aimed to discuss the possibility of adding voids within the beams which its dimensions are more than required in order to reduce the cost and dead load. The selected percent of voids to volume of tested beams was 10%. The shape of voids was a first variable (spherical voids or conic voids). Also, the alteration in behavior when a (5cm) concrete layer thickness of compression zone was replaced with a concrete layer modified with adding polyvinyl alcohol (PVA) was investigated, as a second variable. After testing six samples, the result showed that the failure criteria of normal concrete voided beams is transformed from flexural behavior to shear behavior, while the failure criteria of control solid specimen was flexure behavior. Also, the modified beams failed in flexural behavior except the beam with conic voids failed in shear behavior. Corresponding to this transform, the ultimate load varied in the same manner. Where, the normal concrete voided beams failed with lesser ultimate load than control solid beam of about (6.4% and 18.3%) for spherical and conic voids, respectively. While, the ultimate load of modified concrete beams is increased of about (13.8%, 5.4% and 3.1%) for solid beam, spherical and conic voided beams respectively in comparing control specimen.

تحديد أبعاد العتب الخرساني المسلح المستمر يعتمد على الفضاء الحرج. من الناحية ألعملية فإن تغيير أبعاد الاعتاب الأخرى أمر صعب. يهدف هذا العمل إلى التحقق من إمكانية إضافة فراغات في المناطق الداخلية من الاعتاب التي ابعادها أكثر من المطلوب من أجل تقليل التكلفة والحمل الميت. وعليه, كانت النسبة المئوية المختارة من حجم الفراغات لحجم النماذج المفحوصة هي 10٪. كان شكل الفراغات هو المتغير الأول في الدراسة (الفراغات الكروية أو الفراغات المخروطية). كذلك تم دراسة التغير في سلوك الاعتاب عندما تم استبدال 5 سم من خرسانة منطقة الضغط بطبقة خرسانية أخرى تم تعديلها باستخدام كحول بولي فينيل كمتغير ثان. بعد فحص ست نماذج اظهرت النتائج ان صيغة الفشل تتحول من الانثناء الى القص في الاعتاب الخرسانية المجوفة في حين ان صيغة فشل العتب غير الجوف المصدري كانت بالانثناء. كذلك, كانت صيغة فشل الاعتاب ذات الخرسانة المعدلة باستخدام كحول بولي فينيل بالانثناء باستثناء العتب ذو الفراغات المخروطية فشل بالقص. ورافق هذا ألتحول, تغير الحمل الاقصى بنفس الطريقة. حيث فشلت الاعتاب الخرسانية المجوفة بحمل اقصى أقل من العتب المصدري بنسبة (6.4٪ و 18.3٪) بالنسبة للفراغات الكروية والفراغات المخروطية على التوالي. أما للاعتاب ذات الخرسانة المعدلة ازداد الحمل الاقصى لها عن الحمل الاقصى للعتب المصدري بنسبة (13.8٪ و 5.4٪ و3.1٪) بالنسبة للعتب غير المجوف والعتب ذو الفراغات الكروية والعتب ذو الفراغات المخروطية على التوالي.

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