scholarly journals Sustained Loading Bond Response and Post-Sustained Loading Behaviour of NSM CFRP-Concrete Elements under Different Service Temperatures

2021 ◽  
Vol 11 (18) ◽  
pp. 8542
Author(s):  
Javier Gómez ◽  
Cristina Barris ◽  
Marta Baena ◽  
Ricardo Perera ◽  
Lluís Torres
Keyword(s):  
Ultimate Load ◽  
Load Level ◽  
Sustained Load ◽  
Load Testing ◽  
Near Surface ◽  
Sustained Loading ◽  
Carbon Fibre Reinforced Polymer ◽  
In Series ◽  
Fibre Reinforced Polymer ◽  
Cyclic Service

Nowadays, one of the foremost procedures for strengthening concrete structures is the Near-Surface Mounted (NSM) technique. This paper presents an experimental study on the effect sustained loading and different service temperatures (steady and cyclic) have on NSM Carbon Fibre-Reinforced Polymer (CFRP)-concrete bonded joints and their post-sustained loading load-slip behaviour. Four experimental campaigns using eight NSM CFRP-concrete specimens were performed by employing two different service load levels (15% and 30% of the ultimate load) and combining two groove thicknesses (7.5 and 10 mm) and two bonded lengths (150 and 225 mm). Two steady state temperatures (20 and 40 °C) and two cyclic service temperatures (ranging between 20 and 40 °C) were programmed. The slip obtained was proportional to the sustained load level. Furthermore, higher slips were registered for specimens under higher mean temperatures in the cycle. After 1000 h of sustained load testing, the specimens were tested under monotonic loading until failure (post-sustained loading tests). In general, the ratio between the post-sustained loading ultimate load and the instantaneous ultimate load was close to the unity, although some differences were perceived in series S2 (steady 37.7 °C) with a mean increase of 6.3%, and series S3-B (cyclic temperature ranging between 24.6 and 39.2 °C) with a mean reduction of 9%.

scholarly journals Strengthening of self-compacting reinforced concrete deep beams containing circular openings with CFRP

2018 ◽  
Vol 162 ◽  
pp. 04015
Author(s):  
Nabeel Al-Bayati ◽  
Bassman Muhammad ◽  
Murooj Faek
Keyword(s):  
Ultimate Load ◽  
Test Results ◽  
Load Path ◽  
Deep Beams ◽  
Self Compacting Concrete ◽  
Reinforced Polymer ◽  
Web Reinforcement ◽  
Externally Bonded ◽  
Carbon Fibre Reinforced Polymer ◽  
Fibre Reinforced Polymer

This paper shows the behavior of reinforced self-compacting concrete deep beams with circular openings strengthened in shear with various arrangements of externally bonded Carbon Fibre Reinforced Polymer (CFRP). Six simply supported deep beams were constructed and tested under two points load up to the failure for this purpose. All tested beams had same geometry, compressive strength, shear span to depth ratio, main flexural and web reinforcement. The variables considered in this study include the influence of fiber orientation, utilizing longitudinal CFRP strips with vertical strips and area of CFRP. The test results indicated that the presence of the circular openings in center of load path reduce stiffness and ultimate strength by about 50% when compared with solid one, also it was found that the externally bonded CFRP can significantly increase the ultimate load and enhance the stiffness of deep beam with openings.

scholarly journals COMPARATIVE ANALYSIS OF FLEXURAL STIFFNESS OF CONCRETE ELEMENTS WITH DIFFERENT TYPES OF COMPOSITE REINFORCEMENT SYSTEMS

2021 ◽  
Vol 13 (0) ◽  
pp. 1-5
Author(s):  
Haji Akbar Sulatani ◽  
Viktor Gribniak ◽  
Arvydas Rimkus ◽  
Aleksandr Sokolov ◽  
Lluis Torres
Keyword(s):  
Multiple Cracks ◽  
Flexural Stiffness ◽  
Near Surface ◽  
Stiffness Analysis ◽  
Simplified Approach ◽  
Reinforced Polymer ◽  
Glass Fibre Reinforced Polymer ◽  
Carbon Fibre Reinforced Polymer ◽  
Fibre Reinforced Polymer ◽  
Composite Reinforcement

Various materials and reinforcement technologies have been created for concrete structures. However, there is no uniform methodology to compare the mechanical characteristics of different reinforcement systems. In structural systems, residual stiffness can estimate the efficiency of the reinforcement. This study introduces a simplified approach for the flexural stiffness analysis. It employs a new testing layout designed with the purpose to form multiple cracks in a small laboratory specimen. The achieved solution requires neither iterative calculations nor a description of the loading history. Several composite reinforcement schemes, including internal glass fibre reinforced polymer (GFRP) bars, carbon fibre reinforced polymer (CFRP) sheets and near-surface mounted (NSM) strips are considered. The analysis of the test results reveals a substantial efficiency of the external CFRP reinforcement systems.

Blast Testing of RC Slabs Retrofitted with NSM CFRP Plates

2007 ◽  
Vol 10 (4) ◽  
pp. 397-414 ◽  
Author(s):  
Chengqing Wu ◽  
Deric John Oehlers ◽  
John Wachl ◽  
Craig Glynn ◽  
Adrian Spencer ◽  
...  
Keyword(s):  
Reinforced Concrete ◽  
Charge Weight ◽  
Future Research ◽  
Near Surface ◽  
Reinforced Polymer ◽  
Blast Testing ◽  
Carbon Fibre Reinforced Polymer ◽  
Fibre Reinforced Polymer ◽  
Near Surface Mounted ◽  
Rc Slabs

In this paper, blast testing was performed on two reinforced concrete specimens: a plain reinforced concrete (RC) specimen; and an identical RC specimen retrofitted with near surface mounted (NSM) carbon fibre reinforced polymer (CFRP) plates. Each specimen was subjected to two separate explosive loads at a standoff distance of 0.6m, with the aim of investigating the performances of both specimens within both their elastic and plastic response ranges. The first blast (Blast 1) and second blast (Blast 2) consisted of an equivalent TNT charge weight of 0.079kg and 2.09kg respectively. The elastic-range responses of both specimens after the small shot (Blast 1), such as acceleration and deflection were obtained and comparisons were made between the specimens. The plastic performances of both specimens, such as tension face scabbing, crack patterns, plastic hinges and permanent deflection, after the large shot (Blast 2) were also analysed and compared. A number of unique failures and behaviours of both specimens were observed, investigated and analyzed. The test results provide a vital direction in the development of an optimal retrofit in future research.

Concrete cover separation of reinforced concrete beams strengthened with near-surface mounted method: Mechanics based design approach

2019 ◽  
Vol 22 (7) ◽  
pp. 1739-1754
Author(s):  
Ahmad Azim Shukri ◽  
Zainah Ibrahim ◽  
Huzaifa Hashim
Keyword(s):  
Reinforced Concrete ◽  
Carbon Fibre ◽  
Concrete Cover ◽  
Reinforced Concrete Beams ◽  
Near Surface ◽  
Reinforced Polymer ◽  
Carbon Fibre Reinforced Polymer ◽  
Fibre Reinforced Polymer ◽  
Near Surface Mounted ◽  
Concrete Cover Separation

The primary mode of premature failure for near-surface mounted strengthened beams is the concrete cover separation. Due to its complexity, most of the prediction methods for concrete cover separation tend to be empirical based, which can limit their usage to specific near-surface mounted strengthening configurations. In response to that, this article presents a mechanics-based design which uses the moment-rotation approach and the global energy balance approach which is less reliant on empirical formulations, as the mechanics of reinforced concrete beam such as tension stiffening and propagation of concrete cover separation debonding crack are directly simulated rather than empirically derived. The proposed design procedure was validated against published experimental results of reinforced concrete beams strengthened with near-surface mounted carbon fibre–reinforced polymer bars, near-surface mounted carbon fibre–reinforced polymer strips or side-near-surface mounted carbon fibre–reinforced polymer bars and show good accuracy. As it is less reliant on empirical formulations, the proposed design procedure should be applicable to various near-surface mounted reinforcement configurations and materials.

scholarly journals Experimental Work to Study the Strengthening Effect of SFR and CFRP on a Part or Whole of the Length of Slender RC Columns

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Mohammed Al-Helfi ◽  
Ali Allami
Keyword(s):  
Cross Sections ◽  
Ultimate Load ◽  
Steel Fibre ◽  
Concrete Columns ◽  
Effective Length ◽  
Strengthening Effect ◽  
Interaction Diagram ◽  
Reinforced Polymer ◽  
Carbon Fibre Reinforced Polymer ◽  
Fibre Reinforced Polymer

Abstract The This paper is focusses on the investigation of the strengthened column by steel-fibre-reinforced (SFR) and carbon fibre-reinforced polymer (CFRP) on a part or a whole of the length of the column under axial force, and to obtain the effective length, which is responsible for the increasing of the ability of the column to resist buckling. Seven samples were designed as slender reinforced columns with dimensions of 2000 mm length and cross-sections of 120 mm x 60 mm. It was shown that the strengthening of the middle half of the column length by SFR gave an ultimate load similar to the strengthening of the whole column with same material. Also, it was found that the column strengthened by SFR increased its ultimate load by 42.6 %, 42.1 % and 33.3 % for strengthened lengths of dimensions L, L/2 and L/3, respectively, compared to the non-strengthened column. The increase in ultimate load that could be borne by the column strengthened by CFRP were 53.0 % and 33.8 % for strengthened lengths of L and L/2, respectively, only. Interaction diagram had been depended as a theoretical analysis for slender concrete columns. The interaction diagram for the column strengthened by CFRP is greater than for the column strengthened by SFR, which in turn is greater than the non-strengthened column.

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