Thickness of Concrete Cover for Corrosion Protection of Steel Reinforcement and Crack Control

2010 ◽  
Vol 95 ◽  
pp. 61-68 ◽  
Author(s):  
Rina Farhat
Keyword(s):  
Corrosion Protection ◽  
Crack Width ◽  
Limit State ◽  
Concrete Cover ◽  
Steel Reinforcement ◽  
Strain Diagram ◽  
Stress Strain ◽  
Crack Control ◽  
Strain Relationship ◽  
Cover Thickness

Thickness of concrete cover positively affects both the protection of the steel against corrosion and the safe transmission of bond forces. On the other hand it affects Crack control inversely, larger concrete cover causes larger crack width, and as a result it yields reduction in the protection of the steel against corrosion. The influence of the distance between the centroid of the longitudinal reinforcement to the neutral axis, and the stress in the tension steel, on the crack width and Crack control, will be examined. Computations will be done using personal computer program developed for nonlinear analysis of rectangular reinforced concrete sections in flexure. The analysis is performed using Stress-strain relationship for confined concrete: parabola – rectangle with decending branch to 0.3 fc at Ecu, followed by horizontal branch. Stress-strain diagram for reinforcing steel, with an inclined top branch with a strain limit of E su . Beams and slabs elements sections will be examined for the flexural moments from the external loads acting at serviceability limit state. This paper will introduce by computing the concrete fibers stresses and strains over the height of the section, for different element thickness, the influence of tension steel stresses and concrete cover thickness on crack control and corrosion protection of steel reinforcement.

Analysis of Crack Patterns of 500MPa Reinforced Concrete Beams

2013 ◽  
Vol 790 ◽  
pp. 120-124
Author(s):  
Zhi Hua Li ◽  
Xiao Zu Su
Keyword(s):  
Static Loading ◽  
Crack Width ◽  
Concrete Beams ◽  
Concrete Cover ◽  
Reinforced Concrete Beams ◽  
Crack Control ◽  
Crack Patterns ◽  
Beam Depth ◽  
Steel Bars ◽  
Constant Moment

Fourting concrete beams reinforced with 500MPa longitudinal steel bars, of which 6 with skin reinforcement and 8 without skin reinforcement, were tested under two-point symmetrical concentrated static loading to investigate their crack patterns. Crack distributions in constant moment region of beams are compared. The propagation of side cracks along the beam depth is obtained. The results of this study indicate that the concrete cover of longitudinal tensile steel bars and the spacing of skin reinforcement has significant effect on crack distributions; substantial crack control in beams can be achieved if the spacing of skin reinforcement is limited to certain critical values. The curve of d-w(d is the distance between observation points of side cracks and tension face of beams, w refers to crack width at observation points) is approximately characterized by a zig-zag shape and concave-left near longitudinal tensile steel bars.

scholarly journals Applicability of Existing Crack Controlling Criteria for Structures with Large Concrete Cover Thickness

2021 ◽  
Vol 64 (1) ◽  
pp. 69-91
Author(s):  
Chavin Nilanga Naotunna ◽  
S.M Samindi M.K Samarakoon ◽  
Kjell Tore Fosså
Keyword(s):  
Crack Width ◽  
Concrete Cover ◽  
Future Research ◽  
Model Code ◽  
Long Term Study ◽  
Model Code 2010 ◽  
The Aesthetic ◽  
Cover Thickness ◽  
Crack Widths ◽  
Calculation Models

Abstract Widely used crack width calculation models and allowable crack width limits have changed from time to time and differ from region to region. It can be identified that some crack width calculation models consist with limitations for parameters like cover thickness. The current Norwegian requirement for cover thickness is larger than these limitations. The applicability of existing crack width calculation models and the allowable crack width limits must be verified for structures with large cover thickness. The background of crack width calculation models in Eurocode, Model Code 2010, Japanese code, American code and British code have been examined. By comparing the experimental crack widths with the predictions of the aforementioned models, the existing codes can be identified as requiring modification. Considering the durability aspect, it can be identified a long-term study proving that the allowable crack width can be increased with the increase in cover thickness. When considering the aesthetic aspect, the authors suggest categorizing the structures based on their prestige level and deciding the allowable crack widths accordingly. The paper proposes potential solutions for future research on how to improve both crack width calculation methods and allowable crack width limits to be used effectively in structures with large cover thickness.

scholarly journals Comparison of Ultimate Capacities of RC Chimney Sections under Wind Loading

2022 ◽  
Vol 19 (1) ◽  
pp. 1722
Author(s):  
Megha Bhatt ◽  
Sandip Vasanwala
Keyword(s):  
Reinforced Concrete ◽  
Comparative Study ◽  
Ultimate Strength ◽  
Limit State ◽  
Design Concept ◽  
Wind Loading ◽  
Stress Strain ◽  
Limit State Design ◽  
Strain Relationship ◽  
Thin Walled

Diffusion of gaseous and particulate pollutants from tall stacks has formed an important element in the control of air pollution since the industrial revolution began. These tall reinforced concrete chimneys are considered to be cantilever columns subjected to axial load resulted from the self-weight of the shell, linings and other accessories and bending moments which are resulted from the lateral loads like wind forces and earthquake forces. The recently published IS: 4998 – 2015 adopted a limit state design concept which requires well defined stress-strain relationship for concrete and steel. It has been seen that there are many disparities lies between the stress-strain relationships of constituent materials adopted by IS: 4998 – 2015 and other design standards. This paper discusses various methods pertaining to the estimation of the ultimate strength of thin-walled hollow circular sections of reinforced concrete chimneys, subjected to wind loading. A comparative study of various methods based on the prevalent codes reveals considerable disparity in the predicted ultimate strength values. These differences have been critically analyzed and results are discussed in this paper in terms of ultimate strength along with the contribution of concrete and steel, ultimate curvature and depth of neutral axis. For the comparison of above-mentioned parameters, design recommendations of IS 4998 – 2015, CICIND 2011, ACI 307 – 08 are used. HIGHLIGHTS The recently published IS: 4998 – 2015 adopted a limit state design concept which requires well defined stress-strain relationship for concrete and steel which differs in terms of strain and stress limits when compared with other well established RC chimney design codes Various methods pertaining to the estimation of the ultimate strength of thin-walled hollow circular sections of reinforced concrete chimneys, subjected to wind loading are discussed using a comparative study with different parameters of RC chimney For the comparison of above-mentioned parameters, design recommendations of IS 4998 – 2015, CICIND 2011, ACI 307 – 08 are used Stress-strain relationship of concrete and steel also discussed with the bases of the same is also discussed in detail for each of the above codes GRAPHICAL ABSTRACT

scholarly journals Applicability of existing crack controlling criteria for structures with large concrete cover thickness: Review.

2020 ◽  
Author(s):  
Chavin Naotunna ◽  
S.M Samindi M.K Samarakoon ◽  
Kjell Fosså
Keyword(s):  
Crack Width ◽  
Concrete Cover ◽  
Design Stage ◽  
Rc Structures ◽  
Model Code ◽  
Design Life ◽  
Service Load ◽  
Model Code 2010 ◽  
Cover Thickness ◽  
Calculation Models

Adverse effects from the cracks in Reinforced Concrete (RC) structures are controlled at the structural design stage. Cracks due to service load are controlled by limiting the ‘calculated crack width’ to a ‘maximum allowable crack width’. With the understanding of social and economic advantages of long design life structures, there is a trend of constructing structures up to 300 years of design life. To enhance durability, such structures require relatively large concrete cover thickness. The existing ‘crack width calculation models’, have to be validated before using on such large cover structures. The predictions of crack width calculation models in Eurocode 2, Model Code 2010, Japanese Code, American Code and British code were compared with the results of recent experiments with large cover specimens. It could identify that the aforementioned models have to be improved to predict the crack widths of large cover structures. The necessary improvements of each model have been identified. Next, a literature survey was conducted to check the applicability of the existing ‘allowable crack width limits’, for the structures with large concrete covers. To effectively use the existing allowable limits on such structures, the necessary improvements and future works have been identified considering the durability, aesthetic and tightness criteria.

scholarly journals Performance of Tension Lap-Splice in Lightweight Concrete

2020 ◽  
Vol 9 (3) ◽  
pp. 181-186
Keyword(s):  
Failure Modes ◽  
Lightweight Concrete ◽  
Cost Savings ◽  
Concrete Cover ◽  
Steel Reinforcement ◽  
Moment Capacity ◽  
Bond Behavior ◽  
Lap Splice ◽  
Cover Thickness ◽  
Bar Diameter

The use of Light-Weight Concrete (LWC) in modern construction has resulted in efficient designs and considerable cost savings by reducing structural own weight and supporting footings sections. The purpose of this paper is to investigate the Lap-Splice behavior between LWC and steel reinforcement (RFT). The tested specimens were divided into four groups to study the effect of main variables: steel reinforcement bar size, internal confinement (stirrups), splice length and concrete cover thickness. Four-point bending tests were carried out on test specimens to evaluate the performance of lap splices under pure bending. Bond behavior and failure modes were noted to be similar in the normal concrete and in the LWC. In tested beams, it was observed that the bar size has a significant influence on the mean bond stress in the splice. Improving radial tensile strength by using increasing stirrups number improves the bond behavior. The splice length up to 35 times bar diameter decreased the moment capacity of beam. The splice length of 55 times bar diameter results in the same capacity of the beam without any splice.

scholarly journals Comparative Analytical Study on Crack Width of Reinforced Concrete Structures

2021 ◽  
Vol 7 (7) ◽  
pp. 1203-1221
Author(s):  
Ahmed A. Abu El Naas ◽  
Hany M. El Hashimy ◽  
Khaled F. El Kashif
Keyword(s):  
Crack Width ◽  
Analytical Study ◽  
Limit State ◽  
Concrete Cover ◽  
Design Code ◽  
Element Analysis ◽  
Research Findings ◽  
Flexural Reinforcement ◽  
The Impact ◽  
Numerical Program

This paper presents a comparative study for the cracking limit state according to design codes. It aims mainly to connect research findings with design code equations. Appropriate recommendations are reached and the various factors and parameters influencing crack width investigated. The most appropriate equation for crack width calculation can be found. This is done by creating an analytical and numerical program studied various factors and parameters affecting on the crack width. The Analytical study includes some variables affecting the crack width such as steel stress, concrete cover, flexural reinforcement ratio and rebar arrangement. A 3-D finite element analysis by ABAQUS were used to model and idealize the problem. The numerical results were compared with the analytical results. It was concluded that some codes did not take into account the impact of some major variables and cases on the crack width. Also, it was found that some codes are not clear in the region concerning the position of the crack width calculation and the values obtained for the crack width. For calculating crack width values, JSCE (2007) equation is the most appropriate equation as it takes into account the main parameters that affect crack width. Doi: 10.28991/cej-2021-03091720 Full Text: PDF

scholarly journals Corrosion protection of embedded steel bars in concrete

2018 ◽  
Vol 199 ◽  
pp. 05007
Author(s):  
L., Pistolesi ◽  
C., Zaffaroni
Keyword(s):  
Corrosion Protection ◽  
Cathodic Protection ◽  
Field Tests ◽  
Field Studies ◽  
Concrete Cover ◽  
Reinforcement Steel ◽  
Protection Systems ◽  
Chloride Attack ◽  
Reinforced Steel ◽  
Cover Thickness

The design and construction of structures is a responsible decision, based on sound engineering principles, and virtuous and cautious consideration should be paramount. This presentation is based on the results of two different field studies to protect and ensure longevity of structural reinforced steel in structural concrete.1) Application of sacrificial anodes for the galvanic cathodic protection of reinforced steel.2) Application of a cementitious polymer based elastic coating as a viable corrosion protection system against aggressive elements. The use of these materials allows the protection and increases durability of reinforcement steel in concrete, from premature degradation caused by carbonation and chloride attack, ensuring an extended life span.Sacrificial anodes for galvanic cathodic protection are composed of zinc in conjunction with electrolytic gels that, thanks to electrochemical processes, once connected with the reinforcement steel, lower the potential of corrosion to the reinforcement steel themselves. Thus, allowing the prolongation of corrosive events in structures which need to be repaired whilst preventing degradation, if correctly applied, in new structures.Furthermore, in such protection systems, a polymer-modified cementitious membrane is used, with superior elastic and crack bridge properties in environmental exposure temperatures of up to -20°C, thus protecting the concrete from penetration of carbon dioxide and chloride attack.Due to an in-depth laboratory study in combination with live field tests, this paper will highlight that a 2-mm thick protection layer can effectively counteract the penetration of CO2 for over 50 years, and is comparable to a concrete cover thickness of 54 mm of concrete, at a w/c ratio of 0,5. With regards to chloride attack, studies confirm that 2,5 mm of coating equals 30 mm of concrete cover at a w/c ratio of 0,452.

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