scholarly journals Development of Bonded/Riveted Steel Anchorages of Prestressed CFRP Strips for Concrete Strengthening

Materials ◽  
2020 ◽  
Vol 13 (10) ◽  
pp. 2217
Author(s):  
Bartosz Piątek ◽  
Tomasz Siwowski ◽  
Jerzy Michałowski ◽  
Stanisław Błażewicz
Keyword(s):  
Reinforced Concrete ◽  
Concrete Structures ◽  
Concrete Surface ◽  
Epoxy Adhesive ◽  
Full Scale ◽  
Steel Plates ◽  
Tensile Failure ◽  
Small Scale ◽  
Reinforced Concrete Structures ◽  
Flexural Strengthening

CFRP (carbon fiber reinforced polymer) strips are currently often used to strengthen reinforced concrete structures in flexure. In order to ensure effective strengthening, proper connection between FRP material and concrete structure is needed. CFRP strips can be applied passively (only by bonding to the concrete surface) or actively (by prestressing before bonding). In the case of passive strengthening, CFRP strips connecting by bonding to the surface along the strengthened element are usually sufficient. However, active (prestressing) CFRP strips should be additionally anchored at their ends. Anchoring of unidirectional CFRP strips to the reinforced concrete is difficult because of their weak properties in transverse directions. The paper presents a development of mechanical steel anchorages used in an active CFRP flexural strengthening system for reinforced concrete structures. The anchorages were made of steel plates connected to CFRP strips with steel rivets and epoxy adhesive. They were developed within series of tests on specimens from small-scale to full-scale tested in an axial tensile scheme. The paper describes successive modifications of the anchorages as well as the results of full-scale tests. The final version of the anchorage developed during the research had a tensile failure force of 185 kN, which is sufficient value for CFRP strengthening purposes.

scholarly journals Adhesion characteristics of geopolymer mortar to concrete and rebars

2019 ◽  
Vol 258 ◽  
pp. 01012 ◽  
Author(s):  
Sanjay Pareek ◽  
Hiroo Kashima ◽  
Ippei Maruyama ◽  
Yoshikazu Araki
Keyword(s):  
Reinforced Concrete ◽  
Building Materials ◽  
Concrete Structures ◽  
Acid Resistance ◽  
Steel Plates ◽  
Alkali Concentration ◽  
Reinforced Concrete Structures ◽  
Interfacial Zone ◽  
Adhesion Properties ◽  
Repair Materials

In recent years, geopolymers have gained a wide attention as highly ecological-friendly building materials, having a capability to cut down 70% of CO2 emissions in comparison to the ordinary cement concrete. In this study, geopolymer mortars are proposed as repair materials for reinforced concrete structures, due to their superior acid resistance, heat resistance and high strength in comparison to the existing repair materials. The objective of this study is to investigate the adhesion properties of geopolymer mortars to concrete substrates with different surface treatments, steel plates and rebars. As a result, the geopolymer mortars are found to have excellent adhesion properties to dry concrete substrates, steel plates and rebars. Concrete substrates treated with grinder, further enhanced the adhesion properties of geopolymer mortars. On the other hand, poor adhesion of geopolymer mortars to wet concrete substrates was observed due to the presence of water on the interfacial zone, which decreased the alkali concentration of the geopolymer, resulting in lower adhesion strength. In general, geopolymer mortars are found to have suitable adhesion properties to the concrete substrates, steel plates and rebars and can be applied as repair materials for reinforced concrete structures.

A solution to the thermal problem of fire resistance of spun reinforced concrete columns

2021 ◽  
Vol 30 (2) ◽  
pp. 49-70
Author(s):  
I. I. Palevoda ◽  
D. S. Nekhan
Keyword(s):  
Reinforced Concrete ◽  
Cross Section ◽  
Cross Sections ◽  
Fire Resistance ◽  
Concrete Structures ◽  
Concrete Columns ◽  
Full Scale ◽  
Reinforced Concrete Structures ◽  
Thermal Problem ◽  
Reinforced Concrete Columns

Introduction. Spun reinforced concrete columns are widely used in the present-day international construction practice. Known formulas, used to calculate temperatures of cross sections of reinforced concrete structures, needed to assess their fire resistance limit, are successfully applied to homogeneous structures that have solid sections. However, they are inapplicable to spun reinforced concrete columns due to their structural features. The purpose of this work is to develop a method for solving a thermal problem of spun reinforced concrete columns and adapt existing calculation formulas.Materials and methods. This work addresses the heating of spun reinforced concrete structures in case of fire. Ansys Workbench was employed to perform the computer simulation needed to study the influence of the characteristics of spun reinforced concrete columns on their heating. Results and discussion. In the course of the theoretical studies, the effect, produced by column cavities, the heterogeneity of spun concrete and thin walls of these structures on the heating of their cross sections was assessed with regard for the results of full-scale fire tests of spun reinforced concrete columns. Correction coefficients were obtained in order to take account of these factors. A regression equation was derived as a result of the simulation performed in the context of a full-scale factorial experiment involving coefficient khol, which takes into account the rising temperature of hollow reinforced concrete structures in comparison with solid ones. Khet heating acceleration coefficient is applicable to spun reinforced concrete structures due to the heterogeneity of concrete in the cross section. This coefficient represents a function of the wall thickness. Coefficient kth, which allows for the heating acceleration in the course of crack opening in thin-walled structures, varies in the range of 1.00…1.40. The concrete cracking temperature is 550 °C.Conclusion. A new method allows to solve the thermal problem of fire resistance of spun reinforced concrete columns. The engineering formula used to calculate the temperature in a cross-section was adapted. The results of computer-aided simulation and calculation of temperature values, performed using the adapted formula, show acceptable convergence with the experimental data.

Small Scale Models for Reinforced Concrete Structures

1977 ◽  
Vol 20 (1) ◽  
pp. 0132-0137
Author(s):  
A. H. Chowdhury ◽  
R. N. White ◽  
N. R. Scott
Keyword(s):  
Reinforced Concrete ◽  
Concrete Structures ◽  
Small Scale ◽  
Reinforced Concrete Structures ◽  
Scale Models

Effects of Aggregate Size on Concrete Shear Strength

2014 ◽  
Vol 970 ◽  
pp. 143-146
Author(s):  
Lau Teck Leong ◽  
Chen Zhe ◽  
Abdullahi Ali Mohamed ◽  
Wee Kang Choong
Keyword(s):  
Shear Strength ◽  
Reinforced Concrete ◽  
Concrete Beam ◽  
Concrete Structures ◽  
Aggregate Size ◽  
Shear Behaviour ◽  
Maximum Aggregate Size ◽  
Small Scale ◽  
Reinforced Concrete Structures ◽  
Normal Concrete

In view of the importance of the applicability of small-scale beam specimens in replicating the shear behaviour of prototype reinforced concrete structures, this study was conducted on beam specimens cast with micro-concrete having scaled aggregates (maximum sizes: 10mm, 5mm, and 2mm) to investigate whether the use of micro-concrete impose any reduction in their shear strength. The results indicate the maximum aggregate size (s) has negligible effects on concrete shear strength, and the micro-concrete beam specimens replicate the shear behaviour of normal concrete.

scholarly journals STRUCTURAL DESIGN OF POLYMER PROTECTIVE COATINGS FOR REINFORCED CONCRETE STRUCTURES. PART I: THEORETICAL CONSIDERATIONS

2007 ◽  
Vol 13 (1) ◽  
pp. 11-17 ◽  
Author(s):  
Zenonas Kamaitis
Keyword(s):  
Reinforced Concrete ◽  
Protective Coatings ◽  
Concrete Structures ◽  
Concrete Surface ◽  
Polymer Coatings ◽  
Concrete Cover ◽  
Reinforced Concrete Structures ◽  
Coating Materials ◽  
Barrier Materials ◽  
Mechanism Of Degradation

In a number of situations reinforced concrete structures must be protected by barrier materials to prevent contact with aggressive agents. One of the ways to protect concrete structures from corrosion is to use protective polymer coatings. Polymers as coating materials are not totally resistant and impermeable to all aggressive agents. Gases, vapors and liquids penetrate into a polymer so that the polymer mass swells and eventually disintegrates. However, the penetration/disintegration progresses at a much lower rate than that in the concrete. Surface coatings are able to reduce considerably the penetration, to slow down the rate of deterioration of concrete cover and to overcome most durability problems associated with external attack. In this article the mechanism of degradation of polymer coatings are analyzed. Methodology and predictive models for the degradation over time caused by aggressive actions of polymer coatings are presented. Proposed models can be applied to design of polymer coatings. Such a design of coatings is presented in a simple form for engineering design purposes.

Elimination of Debonging of FRP Strips in Shear Strengthened Beams Using Grooving Method

2011 ◽  
Vol 250-253 ◽  
pp. 1077-1081 ◽  
Author(s):  
Davood Mostofinejad ◽  
Amirhomayoon Tabatabaei Kashani
Keyword(s):  
Reinforced Concrete ◽  
Experimental Studies ◽  
High Strength ◽  
Concrete Surface ◽  
Reinforced Concrete Beams ◽  
Small Scale ◽  
Shear Strengthening ◽  
Flexural Strengthening ◽  
Frp Composites ◽  
Frp Strips

One of the methods of retrofitting reinforced concrete structures is use of FRP sheets to increase the flexural and shear strength of concrete elements. Use of FRP materials is in rapid progress because of their high strength, light weight and easy installation of FRP composites. Poisson’s ratio mismatch between FRP sheets and concrete is resulted premature debonding of FRP strips. Hence, the use of ultimate strength of FRP sheets is difficult if EB (External bonded) is applied in installation of FRP. Therefore, debonding has been repeatedly reported in most experimental studies. Recent studies in Isfahan University of Technology (IUT) show that use of grooving method (GM) to attach the FRP sheet to concrete surface for flexural strengthening is much more effective compared to conventional methods. In present experimental study, small scale reinforced concrete beams were strengthened with FRP strips for shear. Comparison between the ultimate load and deflection of the test beams demonstrates that grooving method was effective and led to elimination of debonding of FRP strips used for shear strengthening.

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