Reinforced Cement Concrete Structures Research Articles

Repair, Retrofitting and Rehabilitation Techniques for Strengthening of Reinforced Cement Concrete Structures Along with Experimental Work

Abstract: Structural strengthening of reinforced cement concrete (RCC) is very important because a large number of infrastructural assets in terms of buildings, bridges, sports stadium etc., which are lifeline for the civilized society. The repair, rehabilitation and retrofitting of concrete structures is really a challenging task, when structure has already undergone major structural damages or deterioration. The primary objective of this paper is to implement appropriate strengthening technique based on the observed damage and analysis results. This article also focuses on the effectiveness of the fibre reinforced polymer (FRP) material for repairs, strengthening, and retrofitting of the distressed RCC members. This has been brought in details in this paper along with experimental work which was successfully executed on the Project Construction Site, New Delhi, where the author of this paper was directly involved in planning and execution of job.

A State-of-the-Art Review on Structural Strengthening Techniques with FRPs: Effectiveness, Shortcomings, and Future Research Directions.

In the pursuit of creating more sustainable and resilient structures, the exploration of construction materials and strengthening methodologies is imperative. Traditional methods of relying on steel for strengthening proved to be uneconomical and unsustainable, prompting the investigation of innovative composites. Fiber-reinforced polymers (FRPs), known for their lightweight and high-strength properties, gained prominence among structural engineers in the 1980s. This period saw the development of novel approaches, such as near-surface mounted and externally bonded reinforcement, for strengthening of concrete structures using FRPs. In recent decades, additional methods, including surface curvilinearization and external prestressing, have been discovered, demonstrating significant additional benefits. While these techniques have shown the enhanced performance, their full potential remains untapped. This article presents a comprehensive review of current approaches employed in the fortification of reinforced cement concrete structures using FRPs. It concludes by identifying key areas that warrant in-depth research to establish a sustainable methodology for structural strengthening, positioning FRPs as an effective replacement for conventional retrofitting materials. This review aims to contribute to the ongoing discourse on modern structural strengthening strategies, highlight the properties of FRPs, and propose avenues for future research in this dynamic field.

Comparative study of buckling restrained braces and fluid viscous damper applied in an RCC structure following pushover analysis

Energy dissipators are widely used to enhance structural performance against wind and seismic activities. Since India is an earthquake-prone country, displacement-dependent (an example: buckling restrained bracing), and velocity-dependent (an example: fluid viscous damper) both types of energy dissipators are becoming more well-known and widely used to lessen the effects of seismic occurrences. Although most of the study about the application and performance evaluation of energy dissipators like buckling restrained braces (BRB) and fluid viscous damper (FVD) were based on steel and composite structure, reinforced cement concrete (RCC) building makes up the majority of structures in India, and a large number of RCC building structure are not capable to resist damage due to seismic activity. Additionally, nonlinear static analysis-based comparative information concerning BRB and FVD is very few. This study focused on a comparison of two energy dissipators- a) buckling restrained bracing (BRB) and b) fluid viscous damper (FVD) used in an RCC structure following pushover analysis to produce a pushover curve and evaluate structural performance. Four Ground floor + 14 (G + 14) storey RCC structures were created according to Indian Standard (IS) provisions in Extended Three-Dimensional Analysis of Building System (ETABS) software and applied BRB and FVD separately in diagonal and inverted V shapes. To compare structural responses with BRB and FVD independently, the results of the diagonal and inverted V systems have been explored. All the data were acquired by utilizing response spectrum sources developed under IS 1893:2016 following ASCE 41–13 NSP graphical display for static pushover curve in ETABS. It has been determined that the sample BRB has performed more admirably than FVD in both circumstances while using a diagonal and inverted V bracing system. But in large displacement FVD tends to increase performance. BRB is stiffer than FVD, allowing it to be used to raise the structure's stiffness as needed. It is essential to consider the seismic weight of BRB and FVD while designing a new building or retrofitting and restoring a structure.

Corrosion Assessment Methods in Reinforced Cement Concrete

Worldwide huge amount was spent on infrastructure development projects, in which a major part is spent on demolishing deteriorated structures due to their reduction in serviceability due to various external factors. This may be attained by preventing reinforced cement concrete (RC) structures from factors that affect serviceability such as corrosion. The research community is developing various techniques to predict corrosion in RC structures to prevent the structure in the initial stages by carrying out maintenance work instead of going for the reconstruction of deteriorated structures. The corrosion of RC structures was mainly caused by chloride ions penetrating the structure or by carbonation. This coefficient can be used to predict the rate of corrosion in concrete. Electrochemical measurement, Eddy current, Half-cell potential measurement, etc., are the experimental techniques to forecast the corrosion rate in concrete reviewed. Recently various software’s like Life 365, Thermos calc, Concrete Compass, etc., were developed to predict the corrosion rate in RC structures. This research paper reviews the effectiveness of the application of software to predict corrosion rate in RC structures by reviewing previous research works to identify an accurate method to be followed.

A comparative assessment of steel-concrete composite and RCC structures towards seismic resilience

Seismic resilience is of paramount importance for the design and construction of structures in earthquake-prone regions. This study aims to provide a comprehensive analysis of the seismic performance of steel-concrete composite and Reinforced Cement Concrete (RCC) structures under dynamic loading, facilitating a comparative assessment of their respective behaviors. The behavior of cement-concrete composite structures, emphasizing the interactions between steel and concrete components, their energy dissipation mechanisms, and their contributions to seismic resistance are explored. This review contributes to the advancement of seismic design guidelines, aiding architects, engineers, and policymakers in making informed decisions regarding safer and more resilient structures.

Comparison of Seismic Analysis of Multi storey Buildings with RCC columns and CFST columns by Varying Heights

As there is an increase in population day by day, there is more requirement for land. But the availability of land on Earth’s surface is 29 % which should be used for various purposes and hence, there would be difficulty in providing accommodation to all the citizens. There comes the idea of vertical development of the structures i.e., multi-story structures. Usage of Reinforced Cement Concrete (RCC) for high rise structures with large spans would be very complex as it requires high grade concrete and steel and hence becomes risky. In that case, the composite structures give effective results due to the co-action of materials. Providing Concrete Filled Steel Tube (CFST) columns will reduce the requirement of formwork and will increase the functional area as the steel tube acts both as longitudinal as well as transverse reinforcement which gives mere resistance to tensile stresses. In this thesis, Multi Storied Structures of G+10, G + 20 and G + 30 were taken and variation was considered in the columns, the rest of the structural elements have been taken of RCC only. The seismic analysis of the structures has been carried out for both the type of structures for each height by using Response Spectrum analysis in Zone II following the guidelines of IS 1893:2016 code using ETABS software. The comparison of the structures has been shown in terms of earthquake response parameters such as story drift, story displacement, story shear etc. It has been concluded that structures with CFST columns have shown better seismic performance with increasing height compared to RCC structures.

Provisions of Sustainability in Structural Design Approaches in Different Codes

Concrete has changed the norms in the Construction industry, it has modified the thinking and possibilities of the general public. Particularly, Reinforced Cement Concrete (RCC) is being used throughout the world; whether it be tall sky scrapers in the Middle East, or the vast buildings in Central Europe, RCC has altered the construction Industry. But then again, RCC has its fair share of shortcomings, in recent times it has been recorded that RCC structures collapse due to brittle failure. Seismic loading, mainly from earthquakes are mostly responsible for structure failure as seismic waves generally lead towards overloading and ultimately the structure fails. Cement is generally an energy releasing material and it releases immense amount of CO2 emissions into the earth’s atmosphere, causing the ozone layer to deplete. Hence to minimize this impact and to provide a sustainable solution and to minimize the accidents different sustainable houses are being provided to the people. By doing this, we can reuse existing building assets to minimize the waste and to reduce the pollution. In 2011, International Organization launched the Life cycle Sustainability assessment to have a more sustainable approach towards construction by using different techniques. Life cycle sustainability assessment is a suitable too used for environmental performance of buildings. In this paper we will look to observe different provisions of sustainability in different structural designs taking different codes as a reference.

Embedded system for ultrasonic imaging of under-water concrete structures

Many of the modern concrete structures such as sea-links and bridges are built in water. They require structural health monitoring (SHM) and audit to ascertain the quality and estimation of remaining useful life. To meet these requirements, a single-channel ultrasonic imaging system has been designed and developed to detect defects, porosities and rebar locations inside the Concrete/ Reinforced Cement Concrete (RCC) structures. This real-time and reconfigurable embedded system whas evaluated by carrying out under-water imaging of Concrete and RCC test blocks. Conventionally, Ultrasonic Pulse Velocity (UPV) method is being utilized over three decades in Transmit-Receive (T-R) mode to estimate the density and strength of the concrete structure under test. UPV method requires a skill to interpret the data provided by the UPV instrument. The novelty of the single-channel system discussed in this paper is that it is capable of inspecting Concrete/ RCC structures both in Pulse Echo (PE) as well as in T-R mode. An application software has been developed using C# in a visual environment for image acquisition and the control of Data Acquisition (DAQ) hardware has been interfaced to the computer via USB. The imaging system performs data acquisition and coherent averaging of the RF bipolar data to achieve Signal-to-Noise Ratio (SNR) higher than 20 dB. The performance of the system was evaluated by acquiring B-Scan images of the water submerged concrete test blocks having Side Drilled Hole (SDH) and RCC blocks with one as well as two steel rebars, using 54 kHz water immersion transducer in PE mode. The acquired B-Scan images have revealed the internal details of the sample test blocks, resembling the defects generated in the test blocks. High voltage tone burst bipolar pulser with maximum output of (± 350 V) has been specifically designed for this system to inspect highly attenuative porous and non-homogeneous Concrete/ RCC materials for the detection of SDH and reinforced steel bars in the concrete test blocks, using B-Scan imaging technique.

Case Studies on Condition Assessment and Repairs for Fire Damaged Reinforced Cement Concrete Structures

In India, the shift in the mode of construction of structures from load bearing walled to framed, started in the early eighties. Concrete is highly durable and has very good compressive strength, but is expensive compared to the materials used for load bearing walled structures. Inspite of the cost, since the durability is more, most of the structures being constructed are RCC structures. However, concrete structures are damaged due to the action of fire. Though concrete has good resistance to fire, it is not completely fireproof. This study presents two case studies on structures damaged by fire. The condition assessment, Non Destructive Testing for quality evaluation of the concrete and the suggested repair techniques are discussed.

Strength Comparison of Bamboo and Steel Reinforcement in Mud Concrete

The authors have designed mud concrete, by replacing cement with Over the past decade the price of construction materials like cement, aggregates, steel etc. have increased many folds, making it difficult for rural people to afford the cost of construction. The biggest problem of reinforced cement concrete (RCC) structures is corrosion of steel, as well as carbon footprint. Locally available Red soil, Fly Ash and achieved an approximate strength 20 MPa meeting the requirements of IS 456:2000 as the minimum grade suggested for RCC structures. This research paper discusses the viability of using bamboo bars as an alternative to steel reinforcement bars in mud concrete. In this research five mix design variations are designed as per IS 10262-2009, control mix (M20), 20%, 30%, 40% and 50% of partially replaced cement. Each variation comprised of locally available Red Soil (mud), and Fly ash in 2:1 ratio and lime as fixed 5%. Bamboo and steel bars of diameter 12 mm are used. Beam (Prism) of size 500 mm x 100 mm x 100 mm were casted with bamboo and steel reinforcement bars in single and double layers. These were cured and tested in flexure at 7 and 28 days as per IS 516-2002.The results between the beams of all variations are compared. It is found that the beam with doubly reinforced bamboo bars of 50% cement replacement gave similar results to M20 doubly reinforced steel bars with the added advantage of elimination of corrosion, decrease in self weight and non brittle breakage.

Deep learning based thermal crack detection on structural concrete exposed to elevated temperature

Health monitoring of concrete including, detecting defects such as cracking, spalling on fire affected concrete structures plays a vital role in the maintenance of reinforced cement concrete structures. However, this process mostly uses human inspection and relies on subjective knowledge of the inspectors. To overcome this limitation, a deep learning based automatic crack detection method is proposed. Deep learning is a vibrant strategy under computer vision field. The proposed method consists of U-Net architecture with an encoder and decoder framework. It performs pixel wise classification to detect the thermal cracks accurately. Binary Cross Entropy (BCA) based loss function is selected as the evaluation function. Trained U-Net is capable of detecting major thermal cracks and minor thermal cracks under various heating durations. The proposed, U-Net crack detection is a novel method which can be used to detect the thermal cracks developed on fire exposed concrete structures. The proposed method is compared with the other state-of-the-art methods and found to be accurate with 78.12% Intersection over Union (IoU).

Time and cost comparison of reinforced cement concrete and steel structure

In South Asian countries concrete is mostly used as construction material, especially for low rise structures. Still steel is not predominantly used in high rise structures. Besides, Reinforced Cement Concrete (RCC) and steel structures; composite structures can be built to get maximum benefit of the steel and concrete, as well to produce reliable and economic structures. In this paper comparative study of nine storey hospital RCC and steel building is carried out. For the modelling and analysis of RCC and steel structure ETABs software is used. Comparative study of different parameters like base shear, load carrying capacity, displacement, time period, axial force, and cost is carried out with RCC and steel structures. Final results illustrates that steel structures are more suitable for high rise structures, less time consuming and they are cost effective too.

Analytical and experimental study on shear performance of RCC beam elements reinforced with PSWC rebars: a comparative study

Early distress in RCC (Reinforced Cement Concrete) structures in the recent times poses a major problem for the construction industry. It is found that in most of cases, distresses in reinforced concrete structures are caused by corrosion of rebar embedded in the concrete. The HYSD (High Yield Strength Deformed) rebars which are used to offer excellent strength properties is detrimental to durability due to action of ribs as stress concentrators. Nowadays, concept of PSWC rebars (plain surface with wave type configuration rebars, formerly known as C-bars/mild steel rebar with curvy profile) is emerging to have a compromise between strength and durability. This investigation assesses the flexural behaviour of RCC elements reinforced with PSWC rebars. The flexural performance of RC beams of size 1000mm x 150mm x 150mm reinforced with PSWC rebars at 4mm and 6mm deformation level was studied by conducting test as per IS 516-1959 under four point loading. The performance of PSWC bar reinforced elements are compared with beams reinforced with mild steel rebars, HYSD rebars with spiral and diamond rib configuration to assess the viability of PSWC rebars to replace conventional reinforcement. The test results are validated by numerical analysis with the help of ANSYS software. Totally 15 beams are subjected to flexure test and the performance evaluators are first crack load, deflection at first crack load, ultimate load carrying capacity, deflection at ultimate load, load-deflection behaviour, load-strain behaviour and failure pattern. It is found that PSWC rebars as reinforcement in concrete beams enhanced the ductile behaviour of beams as compared to conventional HYSD and mild steel rebar beams. The energy absorbing capacity has increased significantly for beams reinforced with PSWC rebars when compared with conventional HYSD and mild steel rebar beams. The load-deflection behaviour and failure mode of PSWC rebars reinforced concrete beams were found to be similar to that of high yield strength rebars irrespective of deformation level. The analytical investigation from ANSYS software gave good agreement with the experimental results. It is concluded that PSWC bar has the potential to replace conventional HYSD rebar. Further study needs to be done to optimize the profile level and stirrup locations; and usage with high concrete grade for effective exploitation.

Case Studies of Rehabilitation / Repair of Reinforced Cement Concrete Structures

Case Studies of Rehabilitation / Repair of Reinforced Cement Concrete Structures

Comparative Study of Pure Mg and AZ91D as Sacrificial Anodes for Reinforced Cement Concrete Structures in a Chloride Atmosphere

Comparative Study of Pure Mg and AZ91D as Sacrificial Anodes for Reinforced Cement Concrete Structures in a Chloride Atmosphere

Comparative Study of Pure Mg and AZ91D as Sacrificial Anodes for Reinforced Cement Concrete Structures in Chloride Atmosphere

Comparative study of the corrosion behavior of pure Magnesium and AZ91D anodes in reinforced cement concrete was undertaken in the present work. The steel reinforcements were kept in contact with these anodes electrochemically in chloride atmosphere and the half-cell potential drop was observed. Bare steel reinforcements were tied to the anodes and were also kept in high chloride atmosphere to test the mechanical properties. The yield stress and ultimate tensile stress were found to decrease by approximately 50MPa while the reduction in percentage elongation is approximately 25% for reinforcements tied to AZ91D and pure Mg at the end of 80 days compared to fresh steel reinforcement. The rate of corrosion of pure Mg was reportedly slightly higher compared to AZ91D due to the presence of inter-metallics as inferred through micro-graphs.

Study on GFRP Reinforced Beams under Flexure

Acute shortage of raw materials and deterioration of reinforced concrete structural elements lead to implementation of new substitute materials and innovative technologies. Reinforced Cement Concrete structures are usually reinforced with steel bars which are subjected to corrosion at critical temperature and atmospheric conditions. The structures can also be reinforced with other materials like Fibre Reinforced Polymers (FRP). In this line Fibre Reinforced Polymer based reinforcement replacing conventional steel rod for a precast element of a prefabricated structure is considered. The precast member cast out of M25 grade concrete reinforced exclusively with locally produced Glass Fibre Reinforced Polymer (GFRP) bars including GFRP stirrups is designed, cast. Flexural behaviour of rectangular concrete beams reinforced with FRP bars and stirrups is examined with two specimens one with conventional sand as fine aggregate and another with quarry dust as fine aggregate. The load at cracking and ultimate, type of failure and crack patterns are observed and compared with those of conventional cement concrete.

Study on performance of waterborne anticorrosive coatings on steel rebars

Durability of reinforced cement concrete structures is mainly affected by corrosion of steel reinforcements. In order to protect the reinforcing bars from corrosion and to enhance the lifetime of reinforced cement concrete structural members, anticorrosive treatment to steel is of prime importance. Conventional coatings are solvent based. In this study, water based Latex was used to formulate anticorrosive coating. Latex is applied to steel specimen substrates such as plates and rods and their mechanical properties such as flexibility, abrasion, bendability, adhesive strength, impact resistance, etc. were studied. It was inferred that coating containing latex, micro silica, zinc phosphate, ferric oxide, aluminum oxide, titanium oxide and silica fume was found to possess more corrosion resistance under marine exposure conditions.

In-structure response spectra considering nonlinearity of RCC structures: Experiments and analysis

Many devastating earthquakes exceeding the design basis levels have occurred in the past. Safety assessment of equipments and piping systems of industrial/nuclear safety related structures subjected to earthquakes beyond design basis levels necessitates consideration of the structural nonlinearity. The In-structure or floor response spectra (FRS) are the input required for qualification of these systems and hence it is essential to generate this input considering structural nonlinearity. This paper addresses the experimental and analytical work on generation of FRS for nonlinear Reinforced Cement Concrete (RCC) structure. Push over and shake table experiments are performed on three storeyed RCC framed structure. A simplified analytical approach is proposed to derive earthquake-induced In-structure response spectra for the structure deforming beyond elastic limits. In this approach, initially, the performance of the structure is evaluated using pushover analysis. Floor spectra of the structure are then obtained considering the degraded stiffness and increased damping evaluated at each performance level iteratively from pushover curve. The floor spectra of the structure generated by the proposed method are validated using experimentally simulated results from shake table tests.

Identification of Zero Effect State in Corroded RCC Structures Using Guided Waves and Embedded Piezoelectric Wafer Transducers (PWT)

Reinforced cement concrete (RCC) structures are prone to damages such as corrosion of reinforcement, surface cracking, debonding and the like. The corrosion process results in two effects, namely, reduction in the diameter of rebar and debonding at the steel/concrete interface. Several researchers have worked to establish a correlation between intrinsic damage features and guide wave signal characteristics. However, the work till date is focused mainly on identifying the individual damage phenomenon, and few researchers have attempted to correlate the combined effect of these damage parameters. Therefore, it is an impending task to study the combined influence of corrosion and debonding on wave characteristics and to establish methods to distinguish and correctly quantify the damage level. A three-dimensional finite element model of a RCC beam is developed in the Abaqus software by using an explicit method in order to study wave propagation in an RCC beam after including the two effects of corrosion. The implicit and explicit models are co-executed using standard-explicit co-simulation. It is observed that the reduction in diameter would result in the diminishing of the guided wave amplitude, whereas debonding results in an increase in the guided wave amplitude. It is found that these two complimentary effects on wave features result in a signal that has the same wave features as undamaged rebar that is surrounded by concrete, which could be termed as the zero effect state.