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Article
Effect of Steel Fibers Addition on the Behavior of High Strength Concrete Circular Short Columns
تأثير إضافة ألياف الفولاذ على سلوك الأعمدة الخرسانية الدائرية عالية المقاومة و القصيرة

Authors: Zubidah Abdullateef Al-Bayati --- Riyadh Jawad Aziz --- Yasir M. W. Al-Shamma
Journal: Journal of Engineering مجلة الهندسة ISSN: 17264073 25203339 Year: 2011 Volume: 17 Issue: 4 Pages: 846-859
Publisher: Baghdad University جامعة بغداد

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Abstract

This paper presents the effects of the addition of steel fibers on the behavior of concentrically loaded reinforced concrete circular short columns. An experimental investigation into the behavior of 24 short reinforced concrete columns with and without steel fibers was carried out. The columns had a circular section (200 mm diameter and 900 mm long). Test variables include concrete strength, spacing of spiral reinforcement, and inclusion of steel fibers. The axial stress and axial strains were obtained and used to evaluate the effects of the presence of steel fibers. It was found that the addition of steel fibers slightly improves the load carrying capacity of the tested columns whereas it significantly enhances the ductility of these specimens. Test results also indicated that for the same confinement parameter psfsy/f'c , specimens with steel fibers has higher strength enhancement compared to specimens without steel fibers. For confinement parameter of 0.1 the strength enhancement equal 1.7 for specimens with fibers while it is 1.4 for nonfibrous specimens. An empirical expression is proposed and used to predict the confined strength of columns. It was shown that the proposed formula predicts the load carrying capacity of the tested columns reasonably.

يبين هذا البحث تأثير إضافة مادة ألياف الفولاذ على سلوك الأعمدة الخرسانية عالية المقاومة الدائرية و القصيرة و المفحوصة تحت تأثير أحمال انضغاط محورية. تضمّن الجزء العملي من البحث تحضير وفحص 24 أنموذجاً لأعمدة خرسانية مسلحة دائرية المقطع بقطر 200 ملم و طول 900 ملم تحتوي نصفها على مادة ألياف الفولاذ. تشمل المتغيرات مقاومة الخرسانة للإنضغاط و المسافة الشاقولية لتوزيع حديد التسليح الحلزوني و وجود ألياف الفولاذ ضمن الخرسانة. أظهرت نتائج الفحص بأن ألياف الفولاذ المضافة حسّنت بدرجة قليلة مقاومة التحمل القصوى للأعمدة في حين أن المطيلية ازدادت بشكل كبير مقارنة بالأعمدة غير الحاوية على ألياف الفولاذ. وكذلك وُجد عند تثبيت معامل الحصر فأن تحسين المقاومه للأعمده الحاويه على الياف الفولاذ أعلى من تحسين المقاومه للأعمده غير الحاويه على الألياف. حيث وجد أن تحسين المقاومة بلغ 1,7 للأعمدة الحاوية على ألياف الفولاذ بينما بلغ 1,4 للأعمدة غير الحاوية على ألياف الفولاذ عندما يكون معامل الحصر مساوياً إلى 0,1. و كذلك فقد تم إقتراح علاقة تجريبية للتنبأ بالمقاومة القصوى لخرسانة الأعمدة المحصورة. و قد وُجد أن المعادلة المقترحة تعطي نتائج جيدة مقارنة مع النتائج المختبرية.


Article
Experimental study of Circular Short Columns made from Reactive Powder Concrete

Authors: Asmaa Ali Ahmad --- Faidhi Abdul-Rahman Alkhazraji --- Sarah Mohammed Omar
Journal: Engineering and Technology Journal مجلة الهندسة والتكنولوجيا ISSN: 16816900 24120758 Year: 2016 Volume: 34 Issue: 9 Part (A) Engineering Pages: 1860-1872
Publisher: University of Technology الجامعة التكنولوجية

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Abstract

This research studies the behavior of reactive powder concrete (RPC) circular short columns with and without steel fibers of different types, as well as change of the reinforcement kinds of lateral (hoops and spiral) and the spacing between them. The experimental work consist study of fifteen short column specimens having an overall height of 1 m with circular cross-section of 150 mm diameter are loaded at ends with concentric loads. Six of the specimens are cast with the inclusion of steel fibers with aspect ratio of 75(group 1), and six of other specimens are cast with the inclusion of steel fibers with aspect ratio of 100 (group 2),and the other three specimens is without steel fibers, with hybrid steel fibers and high strength concrete. The concrete mix of fiber-reinforced samples contains 1% by volume of steel fibers of variable reinforcement longitudinal and lateral (hoops and spiral reinforcement). Experimental data for strength, failure mode, lateral, and the ductility were obtained for each test. The work concluded that the using of steel fibers in RPC was an effective way to prevent spalling of the concrete cover and increase the ductility and the using of high ratio of longitudinal reinforcement delays the pickling of the columns and increase strength. The ultimate load capacity of RPC columns of spiral lateral reinforcement is greater than the load of RPC columns of tied lateral reinforcement by about 1.25 to 1.35 times for the two groups.


Article
Proposed Formulation Using ANSYS for Estimation Axially Strength of Steel Tubes Columns Filled with Concrete

Author: Marwah S. Abdul Gbabar
Journal: Engineering and Technology Journal مجلة الهندسة والتكنولوجيا ISSN: 16816900 24120758 Year: 2016 Volume: 34 Issue: 11 Part (A) Engineering Pages: 2057-2071
Publisher: University of Technology الجامعة التكنولوجية

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Abstract

In this paper, concrete filled steel tubes columns (CFT) are investigated by using finite element program ANSYS 15.0. Analysis are done for four different shapes of columns (circular, square,hexagonal andoctagonal). Results of analytical solution (for circular and square) were compared with existing experimental data provided by [Alwash et al., 2013].Comparative resultsof failure load give 4% difference between experimental and ANSYS 15.0. Also, parametric studies have been carried out to investigate the effect of concrete filled steel tubes columns shapes (for hexagonal and octagonal) on load carrying capacity.Finally, a newformulaefor predicting the ultimate strength of CFT is proposedbased on experimental data of 148 CFT columns of different cross sections with side length ranging between 200 and 4000 mm. To check the validity of the proposed equation, the loads calculated from the designmethods (American Concrete Institute (ACI 318M-14), Eurocode (EC4),New Zealand Standard of concrete structures(NZS) and American Institute of Steel Construction (AISC)) are used to compare with it. The comparison shows least convergence percentageof the proposed equation.


Article
Strength Evaluation of Hybrid Reinforced Concrete Columns under Eccentric Loads

Authors: Ammar A. Ali --- Zaynab S. Mohammed
Journal: Engineering and Technology Journal مجلة الهندسة والتكنولوجيا ISSN: 16816900 24120758 Year: 2018 Volume: 36 Issue: 4 Part (A) Engineering Pages: 449-455
Publisher: University of Technology الجامعة التكنولوجية

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Abstract

This study presents an experimental investigation of the behavior of hybrid circular columns composed of outer precast reactive powder concrete (RPC) tubes filled with normal concrete (NC). The column specimens were subjected to an eccentric load producing both flexural and axial stresses within the section. The specimens consisting of 200 mm outer diameter with 400 mm height. The column specimens were divided into three groups, each group contains two specimens of thicknesses of outer RPC walls of 50 and 25 mm that filled with NC, in addition to RPC solid column section. The columns of first group were without any reinforcement. While the second group specimens were longitudinally reinforced, in addition to 180 mm spaced ties. The third group is composed of the same details as that of group two but with 90 mm ties spacing. The results show that, All RPC solid specimens give a higher load capacity from that of the hybrid specimens about 48%. It is noticed that increasing the RPC outer wall thickness improves the ultimate load capacity by 11% for hybrid specimens with 50 mm thickness wall than that of hybrid specimens with 25 mm thickness wall. Also, longitudinal and transverse reinforcement noticeably enhance the ductility and strength of the tested specimens compared with corresponding plain specimens.


Article
EXPERIMENTAL STUDY OF SHORT COLUMNS BEARING CAPACITY SUBJECTED TO UNIAXIAL LOADING
دراسة عملية لسعة التحمل للأعمدة القصيرة المعرضة لأحمال لامركزية باتجاه واحد

Author: Assim Mohammed Lateef عاصم محمد لطيف
Journal: DIYALA JOURNAL OF ENGINEERING SCIENCES مجلة ديالى للعلوم الهندسية ISSN: 19998716/26166909 Year: 2016 Volume: 9 Issue: 4 Pages: 11-23
Publisher: Diyala University جامعة ديالى

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Abstract

Columns can be defined as individuals that carry loads mainly in compression. Frequently, columns carry bending moments as properly, about one or each axis of the cross section. The bending moment action may produce tensile stresses over a part of the cross section. In this research, twenty-four column samples distributed into eight groups were cast to investigate the structural behavior under loading with varying bar diameter, clear cover of vertical reinforcement and concrete strength. Samples designed to fail by tension. The loading rate was set to be from fifteen to twenty percent of designed capacity. The results showed that increasing concrete strength leads to increase in bearing capacity, the load that needs to cause the first crack and decreasing in crack width. Increasing steel bars size showed rising in a column bearing capacity, the load that needs to occur the first crack, crack width and decreasing the number of cracks in tension area. While the large concrete cover caused increasing in bearing capacity, the crack width and reduce the load that needs to produce the first crack.

تعرف الأعمدة بأنها تلك الأعضاء الإنشائية التي تتحمل بصورة رئيسية قوى الانضغاط والعزوم حول أحد أو كلا محوري مساحة المقطع. عزم الانثناء يؤدي الى توليد اجهادات الشد على جزء من مساحة المقطع. في هذا البحث تم صب أربعة وعشرين عمود موزعة على ثمان مجاميع لتحري السلوك الانشائي تحت تأثير التحميل مع تغيير أقطار قضبان حديد التسليح المستخدم، الغطاء الخرساني الصافي للقضبان العمودية ومقاومة الخرسانة، العينات صممت لتفشل نتيجة الشد. نسبة التحميل كانت تتراوح ما بين خمسة عشر الى عشرين بالمئة من الحمل التصميمي. أظهرت النتائج ان الزيادة في مقاومة الخرسانة تؤدي الى زيادة تحمل العمود، الحمل اللازم لحدوث اول تشقق ونقصان في عرض الشق. الزيادة في قطر حديد التسليح أظهرت زيادة في تحمل العمود، الحمل اللازم لحصول اول تشقق، عرض الشق ونقصان في عدد الشقوق في منطقة الشد. بينما استعمال غطاء خرساني كبير سبب زيادة في تحمل العمود، عرض الشق ونقصان في مقدار الحمل اللازم لحصول اول شق.

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