FE modelling of bond interaction of FRP bars to concrete

In this paper a computational modelling approach is used to investigate the bond behaviour of fibre-reinforced plastic (FRP) bars in concrete. Two finite element packages (ANSYS and ABAQUS) are used to model the bond interaction of FRP reinforcing bars in cubes and beams. The main purpose of this work is to develop additional understanding of how FRP bars ‘cooperate’ with concrete to sustain the pullout load. Two modelling approaches are presented. In the first approach, a spring describing the behaviour of short embedment lengths in pullout tests was used for predicting the behaviour of longer embedment lengths. In the second approach, spring characteristics obtained from an experimentally determined bond stress against anchorage length envelope are used in FE modelling of beams. Both approaches showed good agreement between analytical and experimental results. However, further development on the analytical modelling of the bond interaction is required, in order to consider the effect of all parameters that influence bond

Bond behavior of fiber reinforced polymer bars under direct pullout conditions

This paper examines the behavior of Eurocrete fiber-reinforced polymer (FRP) bars (glass, carbon, aramid, and hybrid) in concrete under direct pullout conditions. More than 130 cube specimens were tested in direct pullout where no splitting was allowed to develop. In normal concrete, the mode of bond failure of FRP bars was found to differ substantially from that of deformed steel bars because of damage to the resin rich surface of the bar when pullout takes place. Bond strengths developed by carbon fiber-reinforced polymer and glass fiber-reinforced polymer bars appear to be very similar and just below what is expected from deformed steel bars under similar experimental conditions. The load slip curves highlight some of the fundamental differences between steel and FRP materials. This paper reports in detail on the influence of various parameters that affect bond strength and development such as the embedment length, type, shape, surface characteristics, and diameter of the bar as well as concrete strength. The testing arrangement is also shown to influence bond strength because of the “wedging effect” of the bars

Bond behaviour of FRP bars in concrete.

This thesis investigates the bond behaviour of Fibre Reinforced Polymer (FRP) reinforcing bars in concrete elements both analytically and experimentally. Two series of experiments were conducted. In the first series, more than 100 cube specimens were tested in direct pullout. The mode of bond failure of FRP bars in the pullout tests was found in most cases to differ substantially from that of deformed steel bars. Within this series the parameters that influence bond development were examined. The bond strengths developed by CFRP and GFRP bars appear to be very similar, and just below what is expected from deformed steel bars. In the second series of experiments, nine beams were tested in four-point bending to examine the bond splitting behaviour of FRP single anchorages and splices. CFRP bars develop higher bond splitting strength than respective GFRP bars, which contradicts the findings of pullout tests. The lower elastic modulus of GFRP bars is thought to play an important role to their lower bond splitting strength. For this reason, the suitability of the cube tests for measuring the bond strength ofFRP bars for practical purposes is questioned. Spliced bars appear to develop similar bond splitting strength to single bar anchorages. The distribution of bond stresses along the anchorage length and the effect of flexural cracks on the bond development were also examined. The thesis also discuss other parameters that influence bond splitting such as transverse reinforcement, concrete cover, and support action. An analytical study was conducted to enhance further the understanding of the bond behaviour of FRP bars. Both the pullout and beam tests were modelled by using FE packages. Non-linear springs describing the bond behaviour of short embedment lengths were chosen and used for predicting the behaviour of longer embedments. The influence of flexural cracking was also considered in the case of beams. The analytical results showed a good correlation with the respective experimental. Finally, some important issues regarding the design of anchorage lengths for FRP reinforcing bars were addressed and a method of working towards the formulation of design recommendations is suggested

Bond between glass fibre reinforced polymer bars and high - strength concrete

YesIn this study, bond properties of glass fibre reinforced polymer (GFRP) bars embedded in high-strength concrete (HSC) were experimentally investigated using a pull-out test. The experimental program consisted of testing 84 pull-out specimens prepared according to ACI 440.3R-12 standard. The testing of the specimens was carried out considering bar diameter (9.5, 12.7 and 15.9 mm), embedment length (2.5, 5, 7.5 and 10 times bar diameter) and surface configuration (helical wrapping with slight sand coating (HW-SC) and sand coating (SC)) as the main parameters. Twelve pull-out specimens reinforced with 16 mm steel bar were also tested for comparison purposes. Most of the specimens failed by a pull-out mode. Visual inspection of the tested specimens reinforced with GFRP (HW-SC) bars showed that the pull-out failure was due to the damage of outer bar surface, whilst the detachment of the sand coating was responsible for the bond failure of GFRP (SC) reinforced specimens. The bond stress – slip behaviour of GFRP (HW-SC) bars is different from that of GFRP (SC) bars and it was also found that GFRP (SC) bars gave a better bond performance than GFRP (HW-SC) bars. It was observed that the reduction rate of bond strength of both GFRP types with increasing the bar diameter and the embedment length was reduced in the case of high-strength concrete. Bond strength predictions obtained from ACI-440.1R, CSAeS806, CSA-S6 and JSCE design codes were compared with the experimental results. Overall, all design guidelines were conservative in predicting bond strength of both GFRP bars in HSC and ACI predictions were closer to the tested results than other codes

Assessment of GFRP bond behaviour for the design of sustainable reinforced seawater concrete structures

Freshwater is an increasingly scarce resource. Its use in the production of concrete is one important contributor to its fast depletion. Alternatively, the use of seawater for reinforced concrete production, combined with the use of glass fibre reinforced polymers (GFRP) as reinforcement, may represent an interesting solution to increase concrete sustainability. The objective of this paper is to explore this promising solution through the development of concrete compositions with seawater. Additionally, it is also an objective to assess the bond behaviour between GFRP rods and concrete, in a design perspective. The influence of concrete age, rod diameter and anchorage length were also investigated. An analytical model capable of determining the local bond stress-slip laws was used. Results demonstrated that the use of seawater had no relevant effects on neither concrete mechanical properties nor bond behaviour.The study presented in this paper is a part of the research project “NEXT-SEA: Next Generation Monitoring of Coastal Systems in a Scenario of Global Change”, financed by CCDRN and FEDER funds in the scope of the Next-sea project (NORTE-01-0145-FEDER-000032). The authors acknowledge all the companies that have been involved supporting and contributing for the development of this study, mainly: S&P Clever Reinforcement Ibérica Lda., Burgoparaíso – Unipessoal Lda., Secil, Sika Portugal – Produtos Construção e Indústria S.A. The first and the last authors wishes also to acknowledge the grants SFRH/BD/131913/2017 and SFRH/BSAB/150266/2019, respectively, provided by FCT, financed by European Social Fund and by national funds through the FCT/MCTES

Performance Metrics for Freeway Sensors

Performance measures play a critical role in the operation of Intelligent Transportation Systems (ITS), because they provide feedback to the operators regarding system operations and efficiency. Traffic management systems use archived data, provided by various sensors, as a basis for describing normal conditions and predicting traffic conditions that may be expected at a particular time and place in the highway system. However, data quality is one of the principal concerns of archived ITS data users for the following reasons: 1) Manual inspection techniques are unable to detect significant errors because of the large volume of ITS data; 2) Only minimal error detection can be performed as the data is being collected; 3) Sensors may only fail intermittently and not affect long-term averages; 4) Sensor failures may be masked by congestion or incidents. This project examined several quality control issues on one of the nation’s busiest sections of Interstate, the Borman expressway (I-80/94). Various tests such as speed and volume comparisons, data availability and average effective vehicle length test were developed and applied, revealing significant inconsistency in data quality provided by different detection technologies. Results that document these problems are presented in this study and causes of non-random changes are identified. Finally, several recommendations for improving construction and configuration procedures are proposed. Several simple performance metrics are also documented that transportation agencies can use to assess the quality of traffic data and sustain that quality over time

Adding value using sustainable building construction in Cyprus: the case study of the Cyprus University of Technology in Limassol

The building industry in Cyprus is in the midst of rapid change toward more sustainable design and construction. Sustainable or green building design is still an evolving field with rapid advances in knowledge, technology, and methods of measuring outcomes. The purpose of this study is to apply life cycle costing and assessment for buildings that make use of ‘new sustainable designs and technologies’ and compare directly the results obtained using the ‘existing traditional design’. This work will be supported by the case study of the Cyprus University of Technology performed in the framework of the ValPro European Project (Eracobuild VDP call). The case study of the Cyprus University of Technology provides a different perspective and highlights the potential increase of added value in real estate when involving extensive renovation and rehabilitation of older buildings to serve new functions within an existing city infrastructure

Development of a geographical information system for risk mapping of reinforced concrete buildings subjected to atmospheric corrosion in Cyprus using optical remote sensing data

Concrete reinforced with steel rebars remains one of the most widely used construction materials. Despite its excellent mechanical performance and expected service life of at least 50 years, reinforced concrete is subjected to corrosion of the steel rebars which normally leads to concrete spalling, deterioration of the reinforced concrete’s (RC) mechanical properties and eventual reduction of the structural load capacity. In Cyprus, especially in coastal regions where almost 60% of the population resides, many structural problems have been identified in RC structures, which are mainly caused by the severe corrosion of steel rebars. Most RC buildings, located in coastal areas, show signs of corrosion within the first 15-20 years of their service life and this affects their structural integrity and reliability, especially against seismic loading. This paper presents the research undertaken as part of the STEELCOR project which aims to extensively evaluate the steel corrosion of RC buildings in coastal areas of Cyprus and conduct a risk assessment relating to steel corrosion. Non-destructive testing of corroded RC structures measurements were used to estimate the simplified index of structural damage. These indices were imported into a Geographical Information System to develop a digital structural integrity map of Cyprus which would show the areas with high risk of steel corrosion of RC buildings. In addition, archive optical remote sensing dataset was used to map the urban expansion footprint during the last 30 years in Cyprus with the aim of undertaking corrosion risk scenarios by utilizing the estimated indices. © (2014) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only