STRENGTHENING OF PRESTRESSED HOLLOW CORE SLABS WITH OPENINGS USING NSM-CFRP STRIPS

2016 ◽  
Vol 3 (1) ◽  
Author(s):  
Karam Mahmoud ◽  
Steven Foubert ◽  
Ehab El-Salakawy
Keyword(s):  
Original Structure ◽  
Test Results ◽  
Hollow Core ◽  
Near Surface ◽  
Reinforced Polymer ◽  
Industrial Buildings ◽  
Near Surface Mounted ◽  
Parking Garages ◽  
Strengthening Technique

Precast, prestressed, hollow-core (HC) slabs are extensively used in many structures such as parking garages, commercial and industrial buildings. It is common for such structures to undergo changes while still in service, which may result in a reduction of their strength. One of these changes is to add in-situ openings at different locations along the slab to accommodate services such as intake/exhaust ducts or utility conduits. Near surface mounted (NSM) strengthening technique has proved to be an adequate technique that can be employed to restore or enhance the performance of the original structure. In this paper, the effect of openings and the efficiency of using NSM carbon fiber reinforced polymer (CFRP) strips as strengthening technique are investigated. A total of three full-scale prestressed HC slabs were tested; one without opening, one with an opening in the pure flexural zone and one with strengthened opening. Test results showed the presence of opening along the flexure span had a significant adverse effect on the post-cracking flexural stiffness, cracking load and the ultimate capacity of the slab. However, strengthening the opening with two strips of NSM-CFRP effectively enhanced the post-cracking stiffness, increased the ductility of the member and restored the flexural strength deficit incurred as a result of cutting the opening, and provided a net increase in flexural capacity.

scholarly journals Punching Strengthening of Concrete Slab-column Connections Using Near Surface Mounted (NSM) Carbon Fiber Reinforced Polymer (CFRP) Bars

2020 ◽  
pp. 1-14
Author(s):  
Ahmed H. Abdel-Kareem
Keyword(s):  
Carbon Fiber ◽  
Concrete Slab ◽  
Tensile Force ◽  
Shear Capacity ◽  
Punching Shear ◽  
Near Surface ◽  
Reinforced Polymer ◽  
Externally Bonded ◽  
Near Surface Mounted ◽  
Strengthening Technique

This paper investigates experimentally the effect of near surface mounted (NSM) carbon fiber reinforcement polymer (CFRP) bars as externally strengthening on the punching shear behavior of interior slab-column connections. Many researchers used NSM as a novel strengthening technique in various structural elements. However, the strengthening of slab-column connections using NSN is relatively new. Seven Reinforced concrete (RC) square slabs with a concentric column were tested over simply supported four sides. One control specimen was tested without strengthening, four specimens were strengthened using NSM-CFRP bar installed in pre-cut groove surrounded the column at the tension side of the slab, and two specimens were strengthened using externally bonded (EB) CFRP strips which have the same tensile force of the CFRP bars. The arrangement and the location of the strengthened materials were also test variables. The test results showed that using NSM strengthening technique significantly increased the punching shear capacity and ultimate stiffness compared to using EB strengthening technique. Where the increasing in the punching capacity and ultimate stiffness were 18% and 13-18%, respectively. Moreover, the NSM-CFRP bars greatly reduced the cracks in the punching shear zone around the columns. The measured ultimate punching shear capacity for the tested specimens showed very reasonable agreement with the calculated punching loads based on an analytical model for slab-column connections strengthened using FRP that account for its arrangement and location.  

Analysis of Columns Strengthened using Fibre Reinforced Cementitious Matrix Jackets

2021 ◽  
Vol 9 (9) ◽  
pp. 1795-1800
Author(s):  
Fathima Azad
Keyword(s):  
Steel Plates ◽  
Structural Elements ◽  
Near Surface ◽  
Rc Structures ◽  
Cementitious Matrix ◽  
Reinforced Polymer ◽  
Externally Bonded ◽  
Fibre Reinforced Polymer ◽  
Near Surface Mounted ◽  
Strengthening Technique

Abstract: Maintenance, repair and strengthening of existing concrete structures, either reinforced or prestressed,are important activities of civil engineers. Nowadays different techniques are available for the strengthening. Various techniques were adopted for strengthening RC structures, namely, steel plates, external post tensioning, externally bonded Fibre-Reinforced Polymer (FRP), and near- surface-mounted FRP systems to increase shear and flexural capacity. During the last few decades, strengthening of concrete structural elements by fibre-reinforced polymer has become a widely used technique. But it has several disadvantages due to the epoxy resin like debonding of FRP from the concrete structure, unstable nature of the epoxy at higher temperatures etc. To overcome this, an upgraded system was introduced as an alternative for FRP known as Fibre Reinforced Cementitious Matrices (FRCM). The objective of this paper is to investigate the feasibility of Fibre-Reinforced Cementitious-Matrix materials as an alternative external strengthening technique for RC members. Columns with circular geometry were wrapped with different fibre materials using cementitious matrix. The analysis was done using ANSYS software. Keywords: RC columns, FRCM, Strengthening, fibre, ANSYS

scholarly journals Flexural strengthening of RC beams by using a near surface mounted T-section profiles

2014 ◽  
Vol 13 (3) ◽  
pp. 071-078
Author(s):  
Szymon Chołostiakow ◽  
Renata Kotynia
Keyword(s):  
Reference Beam ◽  
Concrete Surface ◽  
Experimental Program ◽  
Rc Beams ◽  
Test Results ◽  
Near Surface ◽  
Flexural Strengthening ◽  
Existing Structures ◽  
Near Surface Mounted ◽  
Strengthening Technique

The paper presents test results of an experimental program of four full-scale RC beams, strengthened in flexure with T-section carbon fiber reinforced polymer (CFRP) profiles and two reference beams subjected to a six point bending. The novel shape of CFRP profile combines both the near surface mounted (NSM) and externally bonded (EB) strengthening systems. The application of the CFRP profiles consisted of gluing both the web and the flange of the profile to the concrete surface. RC beams made of the same concrete class were differed by the internal steel reinforcement ratio and in a number of applied profiles. Efficiency of this new strengthening product was determined by comparison of the strengthened and non-strengthened RC beams. An increase of the CFRP-concrete bond area and high stiffness of the T-section profiles significantly improved the strengthening ratio (up to 130% of the reference beam) and reduced the maximum mid-span deflection (ranged of 70-80%) of the non–strengthened beams. The CFRP strain utilisation equal to 67% of the tensile strain corresponded to the maximum CFRP strains equal to 0,73%. The promising test results exhibit this system as a very attractive proposal of new strengthening technique used for field applications of the  existing structures.

Flexural Behavior of NSM CFRP - Stone Composite Beams: Experimental Investigation

2012 ◽  
Vol 517 ◽  
pp. 881-886 ◽  
Author(s):  
Zi Xiong Guo ◽  
Yong Ye ◽  
Bao Cheng Liu ◽  
Yang Liu
Keyword(s):  
Failure Modes ◽  
Shear Failure ◽  
Reinforcement Ratio ◽  
Flexural Behavior ◽  
Test Results ◽  
Near Surface ◽  
Reinforced Polymer ◽  
Reinforced Beams ◽  
Test Parameters ◽  
Near Surface Mounted

A technique for increasing the flexural behavior of stone beams using near-surface mounted (NSM) carbon fiber reinforced polymer (CFRP) rods is proposed. Four granite beams were tested under monotonic loading to investigate the effectiveness of this technique. One conventional stone beam was kept unreinforced as the control specimen and three beams were reinforced with NSM CFRP rods. The main test parameters included rod diameters and reinforcement ratios. Three types of failure modes were observed during testing, namely, abrupt fracture for conventional stone beams, flexure failure for moderately-reinforced beams and flexure-shear failure for over-reinforced beams, respectively. Test results showed that reinforcing with NSM CFRP could significantly enhance the flexural behavior of stone beams. For specimens with a reinforcement ratio of 0.14%, an average increase up to 91.0% in the ultimate load with respect to that of the control beam was obtained and the deformation capacity was dramatically increased. For specimens with a reinforcement ratio of 0.28%, though flexural behavior was greatly enhanced, an unfavorable shear failure was observed.

Experimental Study of RC Beams Strengthened with Prestressed near Surface Mounted Helical Rib Steel Wire

2012 ◽  
Vol 204-208 ◽  
pp. 1189-1193
Author(s):  
Chun Sheng Zhang ◽  
Hui Min Hao ◽  
Mei Xiang Zhang ◽  
Ya Hong Ding
Keyword(s):  
High Performance ◽  
Ultimate Load ◽  
Concrete Beams ◽  
Steel Wire ◽  
Reinforced Concrete Beams ◽  
Test Results ◽  
Near Surface ◽  
Steel Wires ◽  
Near Surface Mounted ◽  
Strengthening Technique

A new reinforcement technique with prestressed helical rib steel wires is presented, and one control beam, three strengthened beams under monotonous loads are tested. The flexural capacity, load-deflection relation, cracks and deformation of reinforced concrete beams are systematically studied under the same initial prestress level and amount of reinforcement, different groove size. The test results indicate that the strengthening technique could significantly improve the first-crack load, steel-yielding load, ultimate load of the beams, and improves the service performance of the strengthened beams. The high performance of the helical rib steel wires is allowed for a better utilization. The results provide a reference for engineering applications.

scholarly journals Strengthening Effect of Prestressed Near-Surface-Mounted CFRP Tendon on Reinforced Concrete Beam

2018 ◽  
Vol 2018 ◽  
pp. 1-18 ◽  
Author(s):  
Woo-Tai Jung ◽  
Jong-Sup Park ◽  
Jae-Yoon Kang ◽  
Hee Beom Park
Keyword(s):  
Construction Materials ◽  
Reinforced Concrete Beam ◽  
Fiber Reinforced Polymer ◽  
Strengthening Effect ◽  
Test Results ◽  
Near Surface ◽  
Bond Performance ◽  
Reinforced Polymer ◽  
Near Surface Mounted ◽  
Traditional Construction

Efforts are being made to use FRP (fiber-reinforced polymer) for reinforcements instead of traditional construction materials like steel owing to its remarkable mechanical properties. Among them, this study developed a CFRP tendon to be used as near-surface-mounted reinforcement together with a dedicated prestressing system and investigates experimentally the strengthening effect considering various variables including the amount of reinforcement, the bond performance, and the strength and damage ratio of the concrete. The test results reveal that one line of reinforcement improved the strengthening performance by about 55% and two lines by 96% and that the bonding of the CFRP tendon enhanced the strengthening performance by 15%. Higher strength and damage of the concrete seem to have a poor effect on the overall strengthening performance. However, the use of CFRP tendon with bond performance higher than 11 MPa, filler, and anchorage system appears to promote stable strengthening behavior.

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