A new method to determine locations of rebars and estimate cover thickness of RC structures using GPR data

Cracking of cover concrete due to the corrosion of reinforcing steel is one of the main causes of deterioration in Reinforced Concrete (RC) structures. An outbound stress is developed in concrete surrounding the reinforcing steels due to the expansive corrosion products of reinforcement leading to cracking of the concrete cover. In this paper, the cracking pressure was simulated through a finite element modeling. The effect of geometrical and material parameters, i.e. concrete cover thickness, bar diameter, and concrete tensile strength, on the cracking pressure was also investigated. Abaqus 6.14 was used as modeling platform. The cracking pressure was found to dependent on the cover thickness and tensile strength of concrete. A higher pressure was required to initiate crack for a higher cover thicknesses and tensile strength. The cracking pressure was decreased with the increase in bar diameter. Finally the crack initiation and propagation has been simulated successfully for different arrangements of reinforcements. Journal of Engineering Science 12(1), 2021, 43-49

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

10.22541/au.160632197.72845179/v1 ◽

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.

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INFLUENCE OF THE INFILL TYPOLOGY IN THE EVALUATION OF THE ANNUAL LOSSES OF RC STRUCTURES THROUGH THE APPLICATION OF A NEW METHOD

10.7712/120121.8532.19369 ◽

2021 ◽

Author(s):

Andrea Rossi ◽

Paolo Morandi ◽

Riccardo R Milanesi ◽

Guido Magenes

Keyword(s):

New Method ◽

Rc Structures

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Anchorage/lap strength of bars in RC structures in case of low concrete cover thickness

10.2749/ghent.2021.1057 ◽

2021 ◽

Author(s):

Fabrizio Palmisano ◽

John Cairns ◽

Antonia Menga

Keyword(s):

Environmental Economic ◽

Concrete Cover ◽

Rc Structures ◽

Existing Structures ◽

Codes Of Practice ◽

The World ◽

Cover Thickness

<p>In recent years the assessment of existing structures has become a topic of huge interest all over the world due to environmental, economic and socio-political assets. However, the approach to the assessment of existing structures is in many aspects different from that used for the design of a new structure. This is why there is a necessity to develop new formulations for old materials and products that are consistent with the requirements and the reliability-based approach of current codes of practice. In this scenario, this article analyses a topic very common in existing RC structures, namely the effect of low concrete cover thickness on the anchorage/lap strength of bars. The main aim of the article is to give practical formulations that can be included in future codes of practice. To this aim a novel formulation recently proposed is firstly analysed and then validated against a database of tests taken from the literature.</p>

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Design Service Life of RC Structures with Self-Healing Behaviour to Increase Infrastructure Carbon Savings

Materials ◽

10.3390/ma14123154 ◽

2021 ◽

Vol 14 (12) ◽

pp. 3154

Author(s):

Ana Bras ◽

John Milan van der Bergh ◽

Hazha Mohammed ◽

Ismini Nakouti

Keyword(s):

Service Life ◽

Method Comparison ◽

Self Healing ◽

Rc Structures ◽

Carbon Reduction ◽

Structural Deterioration ◽

Embodied Carbon ◽

Chloride Environment ◽

The Uk ◽

Cover Thickness

Corrosion of reinforced concrete (RC) structures costs the UK GBP 23b annually and is one of the main durability problems contributing to the development of rust, spalling, cracking, delamination, and structural deterioration. This paper intends to demonstrate the benefit of using tailored self-healing bacteria-based concrete for RC corrosion minimisation and service life increase. The purpose was to evaluate the enhancement in the lifespan of the structure exposed to a harsh marine microenvironment by utilising a probabilistic performance-based method. Comparison is made with the performance of a commercially available solution and in terms of embodied carbon impact. Three different concretes, using CEM I 52.5N, CEM II/A-D, and CEM III/A, were tested with and without an iron-respiring bioproduct (BIO) and an added admixture corrosion inhibitor (AACI). Results show that bioproduct significantly contributes to service life increase of RC structures with CEMIII/A. The repair solution with self-healing behaviour not only increases RC service life, but also enables us to decrease the required cover thickness from 60 mm to 50 mm in an XS2 chloride environment. In both XS2 and XS3 environments, a comparison of CEMIII/A+BIO and CEMII/A-D+AACI concrete shows the benefit of using bioproduct in corrosion inhibition context, besides contributing to an embodied carbon reduction of more than 20%.

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A Practice-Oriented Procedure for Seismic Reliability Assessment of RC Structures Affected by Carbonation-Induced Degradation

Applied Mechanics ◽

10.3390/applmech2040047 ◽

2021 ◽

Vol 2 (4) ◽

pp. 820-840

Author(s):

Francesco Nigro ◽

Adamo Zinco ◽

Enzo Martinelli

Keyword(s):

Structural Engineering ◽

Linear Time ◽

Significant Proportion ◽

Time History ◽

Rc Buildings ◽

Rc Structures ◽

Seismic Reliability ◽

Seismic Engineering ◽

Rc Building ◽

Cover Thickness

Existing reinforced concrete (RC) buildings in Europe have generally been designed without proper consideration of seismic actions and capacity design principles, and thus they tend to be vulnerable to earthquakes. Moreover, since a significant proportion of the aforementioned buildings were developed during the 1950s and 1960s, they are currently close to the end of their service life. Therefore, seismic assessment of existing RC building is a major issue in structural engineering and construction management, and the related seismic analyses should take into account the effect of material ageing and degradation. This paper proposes a practice-oriented procedure for quantifying seismic reliability, taking into account the main effects of carbonation-induced degradation phenomena. It summarizes the main aspects of the most up-to-date models for the seismic degradation of concrete and RC members and shows how nonlinear static (pushover) analyses can be utilized (in lieu of the most time-consuming non-linear time history analyses) in quantifying seismic reliability with respect to the performance levels of relevance in seismic engineering. A relevant case study is finally considered with the aim to showing how some parameters, such as exposure class and cover thickness, affect the resulting seismic reliability of existing RC buildings.

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Selective Sampling and Orientation of Non-Homogeneous Tissues

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100100238 ◽

1968 ◽

Vol 26 ◽

pp. 98-99

Author(s):

C. C. Clawson ◽

L. W. Anderson ◽

R. A. Good

Keyword(s):

Electron Microscopy ◽

Electron Microscope ◽

Light Microscopy ◽

Random Sampling ◽

New Method ◽

Microscope Examination ◽

Small Areas ◽

Selective Sampling ◽

Large Numbers ◽

Specific Orientation

Investigations which require electron microscope examination of a few specific areas of non-homogeneous tissues make random sampling of small blocks an inefficient and unrewarding procedure. Therefore, several investigators have devised methods which allow obtaining sample blocks for electron microscopy from region of tissue previously identified by light microscopy of present here techniques which make possible: 1) sampling tissue for electron microscopy from selected areas previously identified by light microscopy of relatively large pieces of tissue; 2) dehydration and embedding large numbers of individually identified blocks while keeping each one separate; 3) a new method of maintaining specific orientation of blocks during embedding; 4) special light microscopic staining or fluorescent procedures and electron microscopy on immediately adjacent small areas of tissue.

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