Carbon Fiber Reinforced Polymer shear strengthening of reinforced concrete beams in zones of combined shear and normal stresses

Significance Statement

Shear failure of reinforced concrete beams occurs abruptly without pre-warning indicators and could lead to calamitous results. Fiber reinforced polymers laminates have emerged as substitutes for the traditional materials and techniques adopted for strengthening of concrete structures. Though expensive, the fiber reinforced polymer laminate technique is still favorable for use in reinforced and pre-stressed concrete strengthening due to its numerous advantages. Most of the current research work has concentrated on the shear capacity and response of simply supported reinforced concrete beams that are strengthened in shear with fiber reinforced polymer sheets. As of now, limited research addresses response of continuous reinforced concrete beams strengthened in shear with fiber reinforced polymer laminate.

In a recent paper published in Composite Structures, researchers led by professor Ezzeldin Yazeed Sayed-Ahmed at The American University in Cairo in Egypt used carbon fiber reinforced polymer for shear strengthening of reinforced concrete beams in zones of combined shear and normal stresses. They also investigated the applicability of the bond reduction factor in regions of combined shear and normal stresses.

In their experimentation, eight continuous reinforced concrete beams of rectangular cross sections and definite spans were selected. The beams had flexural reinforcement of 16 mm bars and 8 mm shear stirrup reinforcements. Near the middle support the stirrup spacing was increased to 200 mm from 100 mm in order to ensure failure occurs at the regions of combined shear and normal stress.

The beams were then grouped into four pairs based on the carbon fiber reinforced polymer sheets configuration. One pair was reserved as the control experiment. The other beams were wrapped with 500 mm wide carbon fiber reinforced concrete polymer sheets at different points and depths. The beams were then loaded monolithically to failure by applying the load symmetrically 550 mm away from the middle supports. Bending moments and shear forces were calculated. Strain gauges were placed near the middle support stirrups and to the carbon fiber reinforced polymers near the same locations. Deflections at the mid-spans were also monitored.

From the empirical analysis conducted the authors of this paper noted that in all the tested beams shear failure occurred with diagonal cracks extending from the point of load application and propagated toward the middle support. For the control beams a sudden increase in strain in the middle span stirrups was observed and at a lower load than all the other groups. In the other beam groups, the first diagonal shear crack appeared at higher loads where sudden increase in the carbon fiber reinforced polymer was also observed.

The researchers realized that the bonded laminate increased the failure load depending on the laminate point of placement on the beam. Continuous wrapping on the full depth of the beam yielded the greatest contribution thereby con-curing with the ACI 440.2-08 code of practice.

From the test, it is clear that the carbon fiber reinforced polymer laminate has significant contribution to the shear strength for beams wrapped along the entire length. It is also noted that post cracking strength decreases as the amount of carbon fiber reinforced polymer laminate increases. This study confirms the bond reduction factor adopted by the ACI 440.2-08 code, which at first was derived for zones of high shear stress only, is now applicable to regions of high shear and normal stresses.

CFRP shear strengthening of reinforced concrete beams in zones of combined shear normal stresses Advances in Engineering

About The Author

Ezzeldin Yazeed Sayed-Ahmed is a Professor and the Graduate Program Director in the Construction Eng. Dept. of the American University in Cairo. Ezzeldin earned his PhD in Civil Eng. in 1995 from the University of Calgary (Canada), his MSc and BSc (w. honour) from Ain Shams University (Egypt) in 1990 and 1986, respectively. He served as the Acting Director of the new credit hours engineering programs of Ain Shams University between 2007 and 2007 and as the Associate Dean of the College of Engineering of Qatar University between 2005 and 2006. Ezzeldin holds the State Award in Engineering Sciences (Egypt) of 1999 and Bruce M. Irons Memorial Scholarship (Canada) of 1994. His biography is listed in Marquis Who’s Who in Science and Engineering, in the World, and in Engineering Higher Education since 2006.

Ezzeldin is a Fellow of the Academy of Scientific Research and Technology (Egypt) and was a member in the IABSE (Switzerland), the CSCE and the CPCI (Canada), the ASCE, the SEI and TMS (USA). He is a Voting Member of the Permanent Committee of the Egyptian Code of Practice for Fibre Reinforced Polymers and the Chair of the Technical Subcommittee for Composite Polymers Structures. Ezz has a USA Patent, 141 publications of which 52 papers in refereed Journal. Ezz supervised/co-supervised 27 MSc and 8 PhD students.

His Research interests cover topics in Advanced Composite Materials, Strengthening of Structures, Seismic Behaviour of High-Rise Buildings with Transfer Floors, Steel Structures and Bridge, Mass Concrete in Dams, Structural Response to Subsurface Blasting, Concrete Masonry Structures, Biomechanics Engineering, and Engineering Education. Ezzeldin is registered Reinforced Concrete and Steel Structure Consultant. He was involved in the design and design review of many iconic projects such as the four 140 m high Minarets of Al-Haram AlMakki Extension (KSA), Al-Haram FRP Temporary Mataf (Makkah), the FRP Clock of King AdbdulAziz Endowment Tower (Makkah), Cambambe Hydroelectric Power Plant and Dam (Angola), Storm-water Drainage for Muna and Muzdalifah, (KSA).

About The Author

Noor Akroush is a Masters of Science Student in the Civil and Environmental Engineering Department of the University of Tennessee Knoxville where she earned the Chancellor’s Fellowship. Noor completed her Bachelor of Science in Construction Engineering with a concentration in Construction Management and Technology in 2015 from the  American University in Cairo, with the highest GPA on the Class of 2015, earning her the President Cup Award for that year.

About The Author

Tariq Almahallawi works as a design manager in the transportation department of Dar Consultants which is one of the world’s leading international consultancies ranked number 1 in the Middle East and number 7 worldwide. Tariq graduated Summa Cum Laude from the American University in Cairo in 2010 majoring in Construction Engineering with a minor in Business Administration and is currently pursuing his Masters of Science degree and is expecting to graduate in June 2018. Tariq works on mega infrastructure projects in the Middle East such as Dubai International Airport, Qatar Lusail City, Al Maktoum International Airport, Cairo Metro project and many other projects which tend to be challenging in nature and complexity. His duties involve preparing technical and financial proposals, setting up project management and control systems, sub-consultant administration, interface management and project scheduling, monitoring and progress reporting.

Tariq has also attained an Envision Sustainability Professional certificate for infrastructure projects in addition to Health, Safety, Security and Environment Risk Assessments. His hobbies include football, travel and squash.

About The Author

Mohamed Alaa Seif  studied Construction Engineering in the American University in Cairo focusing on project management He graduated  in 2015. During his time he co-authored a paper for the “Selection Criteria For Tunnel Construction” which was to be presented at the 2015 CSCE Annual Conference. Later on, he worked on his thesis with two of his colleagues and their findings credited them by getting published in the esteemed Composite Structures Journal. In his project management thesis project, the project was awarded, “Project of the Year” by the Egyptian Civil Engineering Syndicate in 2015.

Mohamed now is back working in his family built business in Alexandria “Seif Group”, which is considered one of the top Construction and Real Estate companies in Alexandria. During his work in the company, he oversaw the building of the apartment building “Seif Latin Building”, while investing even more time in their third company, a manufacturer of Glass Reinforced Fiber Concrete (G.R.C). Where the scope of this company includes the renovation of old, historic, and presidential buildings in Egypt; as well as enhancing aesthetics in many other apartment buildings, malls,  the Cairo Train Station, and parts of the Alexandria Port. His role in the company involves preparing financial proposals for current work, studying and presenting bids for new projects, and progress monitoring and reporting for existing projects. Mohamed competed in professional horseback riding, during his time at school and college and now his hobbies are traveling, and playing various sports namely soccer and volleyball.

Reference

Noor Akroush, Tariq Almahallawi, Mohamed Seif, Ezzeldin Yazeed Sayed-Ahmed. Carbon Fiber Reinforced Polymer shear strengthening of reinforced concrete beams in zones of combined shear and normal stresses. Composite Structures volume 162 (2017) pages 47–53.

Construction Engineering Dept., The American University in Cairo, AUC Avenue, P.O. Box 74, New Cairo 11835, Egypt.

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