327 research outputs found
Effect of fiber-reinforced polymer confinement on bond strength of hooked bars in high-strength concrete
No full textTo assess the viability of the external confinement of high-strength concrete beam-column joints with carbon fiber-reinforced polymer (CFRP) sheets in increasing the bond strength of hooked bars anchored in the joints, 12 hooked bar specimens were tested. The specimen simulated the rigid connection of a cantilever beam to a column. The variables were the beam tensile bar size, anchorage length, mode of confinement of the beam hooked bars in the beamcolumn joint, and presence or absence of fiber-reinforced polymer (FRP) wraps. The nominal or intended concrete compressive strength was 60 MPa (8.7 ksi). Test results of the study were analyzed and the effect of FRP was assessed by comparing performance of specimens whose beam-column anchorage zones were wrapped with FRP sheets with analogous specimens with no FRP. FRP sheets were found effective in increasing the anchorage capacity and the ductility of the load-deflection history. © 2009, American Concrete Institute.[Anonymous], 2005, 318 ACI COMM; *ASTM INT, 2003, A615A615M03A ASTM IN; Hamad BS, 2004, J COMPOS CONSTR, V8, P14, DOI 10.1061-(ASCE)1090-0268(2004)8:1(14); Hamad BS, 2004, ACI STRUCT J, V101, P747; Hamad BS, 2004, J COMPOS CONSTR, V8, P248, DOI 10.1061-(ASCE)1090-0268(2004)8:3(248); HAMAD BS, J COMPOSITES CONSTRU, V9, P440
Comparison of roles of FRP sheets, stirrups, and steel fibers in confining bond critical regions
No full textBased on experimental data of tension lap splices confined with fiber reinforced polymer (FRP) sheets in normal and high strength concrete (HSC) specimens, a new FRP confinement parameter, Ktr,f was recommended. It accounts for the increase in bond strength due to the presence of FRP sheets. In this paper, a correlation is presented between the confining effects of FRP flexible sheets, transverse reinforcement, and steel fibers to improve the bond capacity and ductility of the mode of failure of tension lap splices. The correlation is based on research programs conducted at the American University of Beirut in recent years using identical specimens except for the confinement method used: FRP sheets, transverse steel stirrups, or steel fibers. Other variables included the amount of confinement provided and concrete strength. Analysis of test results indicated that an equivalent improvement in bond strength of tension lap splices in normal and high strength concrete specimens is provided by an amount of FRP sheets corresponding to a Ktr,j value of 2.5, or an amount of transverse reinforcement corresponding to K tr of 1.0db. For HSC specimens, an amount of steel fibers corresponding to a volume fraction of 1percent would provide an equivalent improvement in bond strength. © ASCE.*ACI COMM, 2005, 31805ACI; AZIZINAMINI A, 1993, ACI STRUCT J, V90, P554; Azizinamini A, 1999, ACI STRUCT J, V96, P826; Darwin D, 1996, ACI STRUCT J, V93, P347; Hamad BS, 2004, J COMPOS CONSTR, V8, P14, DOI 10.1061-(ASCE)1090-0268(2004)8:1(14); Hamad BS, 2001, ACI STRUCT J, V98, P638; Hamad BS, 2002, MATER STRUCT, V35, P219, DOI 10.1007-BF02533083; Hamad BS, 2003, ACI STRUCT J, V100, P19; Hamad BS, 2004, ACI STRUCT J, V101, P747; Hamad BS, 2004, J COMPOS CONSTR, V8, P248, DOI 10.1061-(ASCE)1090-0268(2004)8:3(248); SALWAN BR, 2003, THESIS AM U BEIRUT B55
Bond strength of hot-dip galvanized hooked bars in normal strength concrete structures
No full textIn 2001, a multi-phase research program was started at the American University of Beirut (AUB) to evaluate experimentally the effect of hot dip galvanizing on bond strength of reinforcement in concrete structures. In the first two phases, 24 full-scale beam specimens were tested in positive bending to evaluate the effect of galvanizing on bond strength of tension lap splices in normal and high strength concrete specimens. The variables were bar size, concrete strength, the amount of transverse reinforcement confining the splice region, and whether the bars were galvanized or not. Test results indicated that galvanizing had a negligible effect on bond strength of reinforcement in normal strength concrete. However, galvanizing caused an average of 20percent decrease in bond strength of reinforcement in high strength concrete regardless of the amount of transverse reinforcement confining the splice region. This paper reports on a third phase of the AUB program, designed to evaluate the effect of galvanizing on anchorage performance of hooked bars in normal strength concrete structures. Up to date there has been no research work done in this area. Twelve specimens were tested. The specimen simulated the rigid connection of two cantilever beams to a column. The variables were bar size, the confinement mode of the beam bars anchored in the column, and whether the bars were galvanized or not. The effect of galvanizing was evaluated by comparing the performance of galvanized bars with black bars based on the mode of failure, ultimate load, and the general load-deflection behavior. Test results indicated that effect of galvanizing on the bond strength of hooked bars in normal strength concrete was not significant. © 2007 Elsevier Ltd. All rights reserved.[Anonymous], 2002, 318 ACI COMM; *ASTM, 2004, A615A615M03A ASTM; Azizinamini A, 1999, ACI STRUCT J, V96, P826; Hamad BS, 2005, CONSTR BUILD MATER, V19, P275, DOI 10.1016-j.conbuildmat.2004.07.008; HAMAD BS, 1993, ACI STRUCT J, V90, P210; Hamad BS, 2006, ACI STRUCT J, V103, P48; Hamad BS, 2003, ACI STRUCT J, V100, P465; LIEBER W, 1967, ZEM-KALK-GIPS, P912
Effect of FRP confinement on bond strength of hooked bars: Normal-strength concrete structures
No full textTo assess the viability of the external confinement of normal-strength concrete beam-column joints with carbon fiber-reinforced polymer (CFRP) sheets in increasing the bond strength of hooked bars anchored in the joints, 12 hooked bar specimens were tested. The variables were beam tensile bar size, anchorage length, mode of confinement of the beam hooked bars in the beam-column joint (whether the hooked bars were anchored within or outside the column reinforcement cage, denoted as confined specimens or unconfined specimens), and presence or absence of FRP wraps. The specimen simulated the rigid connection of a cantilever beam to a column. The tensile beam reinforcement consisted of two bars anchored in the base column using hooked-bar anchorages. Test results indicated that FRP sheets were effective in increasing the anchorage capacity and the ductility of the load-deflection history for both unconfined and confined specimens. However, FRP sheets had a more significant influence on unconfined specimens than companion confined specimens. As compared with unconfined specimens without FRP wrapping, unconfined FRP specimens had an average of a 23percent increase in bond strength, confined non-FRP specimens had an average 30percent increase in bond strength, and confined FRP specimens had an increase of 54percent. © 2009 ASCE.*ACI, 2005, ACI31805ACI318R05; ASTM, 2004, 2004 ANN BOOK ASTM S, V04.08; Ghobarah A, 2005, J COMPOS CONSTR, V9, P408, DOI 10.1061-(ASCE)1090-0268(2005)9:5(408); Hamad BS, 2004, J COMPOS CONSTR, V8, P14, DOI 10.1061-(ASCE)1090-0268(2004)8:1(14); Hamad BS, 2004, ACI STRUCT J, V101, P747; Hamad BS, 2005, J COMPOS CONSTR, V9, P44, DOI 10.1061-(ASCE)1090-0268(2005)9:1(44); Hamad BS, 2004, J COMPOS CONSTR, V8, P248, DOI 10.1061-(ASCE)1090-0268(2004)8:3(248); Kono S, 1998, P 2 INT C COMP INFR, P343; Pantelides CP, 2008, J COMPOS CONSTR, V12, P435, DOI 10.1061-(ASCE)1090-0268(2008)12:4(435)1
Effect of fiber-reinforced polymer confinement on bond strength of reinforcement in beam anchorage specimens
No full textThis paper reports on the fourth phase of a multiphase study undertaken at the American University of Beirut (AUB) to examine the effect of fiber-reinforced polymer (FRP) sheets in confining bond-critical regions in reinforced concrete beams. Results of the first three phases showed that glass- and carbon-fiber-reinforced polymer (GFRP and CFRP) sheets were effective in increasing the bond strength and improving the ductility of the mode of failure of tension lap splices in high-strength concrete (HSC) and normal-strength concrete (NSC) beams. The main objective of the fourth phase of the AUB study was to assess the effect of CFRP sheets in improving the serviceability and ultimate response of beam anchorage specimens. The added experimental data and the improved knowledge of the bond behavior of FRP confined concrete members will encourage the use of FRP technology to strengthen and retrofit bond anchorage zones. Ten beam anchorage specimens were tested in positive bending in two series. The variables were bar size, anchorage length, and concrete strength. For each bar size, anchorage length, and concrete strength, two companion specimens - identical except for whether the anchorage zone was wrapped with FRP sheets or not wrapped - were tested. The test results demonstrated that CFRP sheets were effective in enhancing the bond strength and ductility of anchorage zones in beam anchorage specimens where splitting failures were imminent.*ACI, 2002, 440R96 ACI; Darwin D, 1996, ACI STRUCT J, V93, P347; Hamad BS, 2004, J COMPOS CONSTR, V8, P14, DOI 10.1061-(ASCE)1090-0268(2004)8:1(14); Hamad BS, 2004, ACI STRUCT J, V101, P747; Hamad BS, 2004, J COMPOS CONSTR, V8, P248, DOI 10.1061-(ASCE)1090-0268(2004)8:3(248)107
Effect of confinement on bond strength of hot-dip galvanized lap splices in high-strength concrete
No full textGalvanizing reinforcing steel is one of the methods used to protect steel bars against corrosion. In 2001, a research program was started at the American University of Beirut (AUB), Beirut, Lebanon, to experimentally evaluate the effect of hot-dip galvanizing on the bond capacity of tension lap splices anchored in full-scale beam specimens designed to fail in bond splitting mode. The test results indicated that the use of galvanized bars had a negligible effect on bond strength of reinforcement in normal-strength concrete. Galvanizing, however, caused an average of 20percent decrease in bond strength of reinforcement in high-strength concrete. The primary objective of the research reported in this paper was to find a solution to eliminate the bond reduction of galvanized bars in high-strength concrete. It was important to evaluate the potential positive effect of the addition of transverse reinforcement in the splice region. One hypothesis to be tested was that such transverse reinforcement would ensure uniform bond stress distribution over the entire splice length, thus mobilizing all bar lugs along the splice in the stress transfer mechanism between the bar and the surrounding concrete, and hence would lead to increasing the bond strength of galvanized bars. The second hypothesis to be checked was whether the aforementioned mechanism of mobilizing all bar lugs along the splice in the stress transfer mechanism would reduce the significant decrease in bond strength of galvanized bars relative to black bars in high-strength concrete. Eighteen full-scale beam specimens, designed to fail in bond-splitting mode, were tested in positive bending. Each beam was reinforced with bars spliced in a constant moment region at midspan. The main variables were bar size and the amount of transverse reinforcement in the splice region. The test results indicated that, whereas confinement increased the bond strength of galvanized bars and black bars, confinement did not have a significant positive effect on the bond strength of galvanized bars relative to black bars. Copyright © 2006, American Concrete Institute. All rights reserved.[Anonymous], 2002, 318 ACI; *ASTM A, 2003, 615615M03A ASTM A, P318; Azizinamini A, 1999, ACI STRUCT J, V96, P826; BRESLER B, 1964, 7 C INT ASS BRIDG ST; BRODBECK H, 1954, SCHWEIZ BAUZEITUNG, P256; GUKILD L, 1965, VARMAFORSINKT ARMERI, P37; Hamad BS, 2003, ACI STRUCT J, V100, P465; KAYYALI OA, 1995, CONSTR BUILD MATER, V9, P219, DOI 10.1016-0950-0618(95)00024-A; KOCH R, BETONWERK FERTIGTEIL, V54, P64; LIEBER W, 1967, ZEM-KALK-GIPS, P91; Orangun C. O., 1977, ACI J, V74, P114; SHMEER F, 1920, DTSCH AUCHUSS EISNEB, P9; SLATER WA, 1920, 173 NBS, P922
Bond strength of tension lap splices in high-strength concrete beams strengthened with glass fiber reinforced polymer wraps
No full textThis paper presents the experimental results of the first phase of a study undertaken at the American University of Beirut to examine the effectiveness of fiber reinforced polymer (FRP) wraps to confine steel reinforcement in a tension lap splice region anchored in high-strength reinforced-concrete beams. Seven beam specimens were constructed. The specimens were reinforced on the tension side with three deformed bars spliced at midspan. The splice region was devoid of any transverse reinforcement to allow a full examination of the FRP wrap contribution. Glass fiber reinforced polymer (GFRP) sheets were used. The main test variables were the GFRP configuration in the splice region (one strip, two strips, or a continuous strip), and the number of layers of the GFRP wraps placed around the splice region (one layer or two layers). All GFRP wraps were U-shaped. Except for the epoxy adhesive, no other anchorage mechanism or bonding procedure was applied for the GFRP wraps on the concrete beam. Following the application of the GFRP wraps, the beams were tested in positive bending. The test results demonstrated that GFRP wraps were effective in enhancing the bond strength and ductility of failure mode of the tension lap splices, especially when continuous strips were applied over the splice region.*ACI, 2002, 31802ACI318R02 ACI; [Anonymous], 1996, 440R96 ACI; AZIZINAMINI A, 1993, ACI STRUCT J, V90, P554; Azizinamini A, 1999, ACI STRUCT J, V96, P922; Azizinamini A, 1999, ACI STRUCT J, V96, P826; CRAIG B, 2002, IN PRESS P 2 INT C D; Darwin D, 1996, ACI STRUCT J, V93, P347; Hamad BS, 2001, ACI STRUCT J, V98, P638; Hamad BS, 2002, MATER STRUCT, V35, P219, DOI 10.1007-BF02533083; ORANGUN OC, 1977, ACI J MAR, P114; SHARAF HA, 2002, P CSCE 30 ANN C CAN; Soudki K, 2003, J MATER CIVIL ENG, V15, P358, DOI 10.1061-(ASCE)0899-1561(2003)15:4(358); Soudki KA, 1997, SOLID MECH APPL, V54, P12598
Behavior of bond-critical regions wrapped with fiber-reinforced polymer sheets in normal and high-strength concrete
No full textThis paper reports on the third phase of a multiphase study undertaken at the American University of Beirut (AUB) to examine the effect of fiber-reinforced polymer (FRP) sheets in confining tension lap splice regions in reinforced concrete beams. Results of the first two phases showed that glass and carbon fiber-reinforced polymer (GFRP and CFRP) sheets were effective in increasing the bond strength and improving the ductility of the mode of failure of tension lap splices in high-strength concrete (HSC) beams with nominal concrete strength of 70 MPa. The experimental results of the two phases were used to propose a new FRP confinement parameter, K tr, f, that accounts for the bond strength contribution of FRP sheets wrapping tension lap splice regions in HSC beams. In this third phase of the AUB study, the trend of the results of phases 1 and 2 and the validity of the analytical model proposed were verified if normal-strength concrete (NSC) is used instead of HSC. Seven beams with nominal concrete strength of 27.58 MPa (4 ksi) were tested in positive bending. Each beam was designed with a tension lap splice in a constant moment region in the midspan of the beam. The main test variables were the configuration (1 strip, 2 strips, or a continuous strip) and the number of layers (1 layer or 2 layers) of the CFRP sheets wrapping the splice region. The test results demonstrated that CFRP sheets were effective in enhancing the bond strength and ductility of failure mode of tension lap splices in NSC in a very similar way to HSC. In addition, the FRP confinement index proposed earlier for HSC was proven to be valid in the case of NSC.[Anonymous], 1996, 440R96 ACI; [Anonymous], 2002, 44002 ACI; Darwin D, 1996, ACI STRUCT J, V93, P347; Hamad BS, 2004, J COMPOS CONSTR, V8, P14, DOI 10.1061-(ASCE)1090-0268(2004)8:1(14); Hamad BS, 2001, ACI STRUCT J, V98, P638; Hamad BS, 2002, MATER STRUCT, V35, P219, DOI 10.1007-BF0253308312111
الأحكام العامة للعقد بين المعايير الشرعية للأيوفي والقانون المدني البحريني:دراسة تحليلية مقارنة: General Provisions of Contract Between AAOIFI Sharia Standards and Bahraini Civil Law: A Comparative Analytical Study
No full textThe research sheds light on a comparison between the provisions of the Bahraini Civil Law and the Sharia standards of the Accounting and Auditing Organization for Islamic Financial Institutions (AAOIFI) with regard to the most important provisions of the contract, such as the pillars of the contract and the form of the contract. The research aims to clarify the most important points of agreement and differences between the civil law and the Sharia standards in relation to Islamic financial transactions to identify the size of the gap between them, in preparation for conducting further studies in this regard due to the subjection of financial transactions applied in Islamic banks in the Kingdom of Bahrain to Sharia standards and civil law provisions. The research relied on the qualitative approach and comparative analytical description. The research concluded that there are many points of agreement between the two references and that the points of difference in the contract and the meeting are not essential, and the researcher recommends conducting more comparative studies between local laws and Sharia standards with regard to Islamic financial formulas and products and re-conducting a comprehensive study of Sharia standards to examine the gaps and weaknesses Through which Islamic banks and their contracts may be affected, the researcher also recommends that the (AAOIFI) Institutions issue sharia standards for contract theory, contract foundations and what is related to it, and to refer in the civil law to the reference of Islamic banks to the sharia standards affiliated with (AAOIFI).
يلقي البحث الضوء على مقارنة بين أحكام القانون المدني البحريني وبين المعايير الشرعية التابعة لهيئة المحاسبة والمراجعة للمؤسسات المالية الإسلامية (الأيوفي) فيما يتعلق بأحكام التعاقد كأركان انعقاد العقد وشكل العقد، والتطرق لبعض صور التعاقد كالعربون والوعد والمواعدة والإذعان، ثم إنهاء التعاقد بالوسائل المعروفة كالانفساخ والإقالة والإبطال، ويهدف البحث إلى بيان أهم نقاط الاتفاق والاختلاف بين القانون والمعايير الشرعية فيما يتعلق بالمعاملات المالية الإسلامية للتعرف على حجم الفجوة بينهما، وذلك تمهيداً لإجراء المزيد من الدراسات في هذا الصدد بسبب خضوع المعاملات المالية المطبقة في البنوك الإسلامية في مملكة البحرين للمعايير الشرعية من جهة، وأحكام القانون المدني من جهة أخرى. وقد اعتمد البحث على المنهج النوعي والوصف التحليلي المقارن. وقد توصل البحث إلى أن هناك نقاط اتفاق كثيرة بين المرجعيتين، وأن نقاط الاختلاف في العقد والانعقاد ليست جوهرية، ويوصي الباحث بإجراء المزيد من الدراسات المقارنة بين القوانين المحلية والمعايير الشرعية فيما يتعلق بالصيغ والمنتجات المالية الإسلامية، وإعادة إجراء دراسة شاملة للمعايير الشرعية لبحث الفجوات ونقاط الضعف التي قد يتم من خلالها التأثير على البنوك الإسلامية وعقودها، كما يوصي الباحث بأن تصدر هيئة المحاسبة والمراجعة (الأيوفي) معايير شرعية خاصة بنظرية العقد وأسس التعاقد وما يتعلق فيها، وأن يشار في القانون المدني لمرجعية البنوك الإسلامية للمعايير الشرعية التابعة للأيوف
Effect of steel fibers on bond strength of hooked bars in high-strength concrete
No full textThe effect of steel fibers in improving the bond performance of hooked-bar anchorages installed in high-strength concrete (HSC) beam-column connections was evaluated by testing twelve beam-column type specimens. The specimen simulated the rigid connection of a vertical cantilever beam to a base column. The tensile beam reinforcement consisted of two bars anchored in the column outside the column reinforcement cage using hooked-bar anchorages. The variables used in the study were the beam bar size (16, 25, or 32 mm) and the volume fraction of steel fibers added and dispersed in the concrete mix (0, 0.5, 1.0, or 1.5percent). Analysis of the test results revealed that steel fibers were effective in increasing the anchorage capacity and the ductility of the load-deflection history of specimens with steel fibers as compared with companion specimens identical in geometry and bar size but without steel fibers. © 2011 American Society of Civil Engineers.*ACI COMM 318, 2008, ACI31808ACI318R08; American Society for Testing and Materials (ASTM), 2006, ANN BOOK ASTM STAND; ASTM C 29-C29M - 09, 2009, ANN BOOK ASTM STAND; Darwin D, 1996, ACI STRUCT J, V93, P347; EZELDIN AS, 1989, ACI MATER J, V86, P515; Hamad BS, 2001, ACI STRUCT J, V98, P638; Harajli MH, 1997, ACI MATER J, V94, P317; HARAJLI MH, 1994, ACI STRUCT J, V91, P511; LAWS V, 1971, J PHYS D APPL PHYS, V4, P1737, DOI 10.1088-0022-3727-4-11-318; RODRIGUEZ J, 1992, P INT C BOND CONCR R; SCOTT BD, 1982, J AM CONCRETE I, V79, P13; YEREX L, 1985, J AM CONCRETE I, V82, P400
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