Behaviour of FRP-to-concrete bonded joints

The bond behaviour between FRP (fibre-reinforced polymer) and concrete is a consideration in the design of FRP strengthening mechanisms for structurally deficient or functionally obsolete concrete structures. In the past, a number of empirical models and fracture mechanics based theoretical models have been proposed for determining the effective bond length and bond strength of FRP sheets/plates bonded to concrete. However, these methods have yielded large discrepancies in the predictions of effective bond length and bond strength. In this paper, the results of an experimental investigation into effective bond length and bond strength are presented. Comparison of experiments results with predictions from three empirical and three fracture mechanics based theoretical models shows that a recently proposed fracture mechanics based local-bond slip model provides a conservative prediction of the effective bond length and an accurate prediction of bond strengt

Investigation of the effect of using fly ash in the grout mixture on performing the fully grouted rock bolt systems

This paper attempts to reveal the influence of using fly ash in the grout on the axial bearing capacity of fully grouted rock bolts. For this purpose, different fly ash contents, including 1% and 2%, have been applied with Stratabinder HS with a water-to-grout ratio of 30%. Also, after preparing and curing the required samples, the UCS tests were conducted to determine the influence of fly ash on the grout strength. Along with the UCS tests, several pull-out tests were examined by preparing and curing rock bolt samples with steel reinforcement rebars of 16 mm and steel pipes with a 50 mm length and 23 mm diameter. The results revealed that replacing a small amount of grout with fly ash could increase the strength of the grout. Also, the axial bearing capacity has risen by using fly ash in the grout mixture

The effect of changing confinement diameter on axial load transfer mechanisms of fully grouted rock bolts

This paper aims to study the effect of changing the confinement diameter on the axial load-bearing capacity of rock bolt systems. The diameter of the confinement is monitored in a fully encapsulated rock bolt at day 7 and 28 of grout curing. These particular times were considered critical to demonstrate grout strength when conducting pull-out tests on rock bolt samples. Following this, the samples were cast with a water-grout ratio of 36%, the internal diameters of encapsulation being 23 mm and 50 mm, and the encapsulation length at 50 mm. The results indicated that by increasing the confinement diameter, the rock bolt\u27s load-bearing capacity increased approximately 32% and 45% for days 7 and 28, respectively

Use of CFRP for rehabilitation of steel structures: a review

One of the main problems facing steel structures is corrosion which effectively reduces total section area of steel members thus leading to elevated stresses in the corroded area. Moreover, increase in the service load of metallic structures, such as bridges, as a result of civil development can aggravate the problem. The need for economical and fast rehabilitation solutions reflects the importance of using carbon fibre reinforced polymers (CFRP) as a repair material. This paper reviews the previous work in this area and shows the structural advantages that can be obtained, along with reducing the cost, through application of CFRP on construction steelworks. A brief conclusion summarizes the benefits and drawbacks of this technique and the paper will serve as a good guide for many engineers who are interested in this topic

Reinforcement of corroded steel structures with CFRP panels

Carbon Fibre Reinforced Polymer composites are a proven method of providing structural strengthening that is lighter, non-corrosive, and less labour intensive than the application of steel plate or exterior post-tensioning. Corrosion of steel structures in bridges and other civil engineering applications induces a serious structural damage that could lead to the failure during operating conditions. Instead of replacing the damaged structures there is the current approach of repairing the corroded steel structures by strengthening the damaged steel beams or gridges using Carbon Fibre Reinforced Polymer (CFRP). The focus in this work is on tension angle members in truss type of steel structures. The loss of sectional area due to corrosion effect was represented by creating notches of different sizes (3 mm – 12 mm) in the angles. The results revealed that CFRP reinforcement is able to rehabilitate the corroded steel to the point that the tensile strength reached a value within 20% of the original value of the undamaged steel truss for artificial notch length lower than 9 mm. The effect of moisture on the corroded and rehabilitated steel structures was also investigated and the results revealed a decrease of 7% in the ultimate tensile strength of the steel truss after 2000 hours of continue immersion in water

The effect of debonding on the flexural behaviour of reinforced concrete beams strengthened with fibre reinforced polymer

In recent years, the use of fibre reinforced polymer (FRP) as a means of rehabilitating or strengthening reinforced concrete (RC) beams has generated much interest in the construction industry. The most popular means of utilising FRP for this purpose involves externally bonding the FRP strip to the extreme tensile fibres of the beam. In previous work, predictions on the behaviour of a beam undergoing debonding have been made utilising experimental FRP strain data to account for the strain incompatibility at the debonded zone. In this paper, previous work has been extended such that strain incompatibility is taken into account through a simple theoretical development to the simple beam theory rather than using experimental measurements of FRP strain data. The model has been verified and used to study the effect of debond length on the flexural behaviour of the beam

Three dimensional finite element analysis of concrete filled FRP tubular model piles under lateral loads

An investigation of the lateral load capacity of model concrete filled FRP tubular composite piles was carried out. Model composite piles which formed a basis for the development of a three dimensional finite element model (FEM) using the ABAQUS analysis package were tested in a sand filled chamber at James Cook University. The results from the laboratory model piles and the FEM analysis provide a clear indication of the superiority of the FRP composite pile over its traditional counterpart under lateral load conditions

Load-deformation behaviour prediction of timber beams externally reinforced with composite materials

Old timber beams have a tendency to weaken with age. In order to repair old timber structures, a rehabilitation technique is required. A rehabilitation method that is getting attention in civil engineering applications recently involves bonding sheets (or bars) of fibre reinforced polymer (FRP) to the tensile face of the affected beam member to improve its strength and deflection characteristics. This paper presents a prediction model based on the virtual work method and Bazan- Buchanan non-linear constitutive law for timber. The model allows the moment-curvature and load deflection relations of FRP reinforced timber beams to be predicted. The model was verified using experimental results from the literature. A parametric analysis was conducted to show the influence of key parameters such as FRP area and FRP type on the load-deflection characteristics of beams loaded in four point bending. From the model presented here, It IS possible to obtain the ultimate load and deflection that each beam can sustain before failure. As expected, the results show that application of an FRP composite to timber beams improves the strength and deflection characteristics of the beam. This indicates that this method may be a quite viable option for the rehabilitation of old timber beam structure

Clogging mechanism of permeable concrete: A review

Urbanization results in the conversion of pervious spaces to areas of impervious (paved) surface which creates numerous problems such as erosion, flash floods, pollution of rivers and hot island in city. A sustainable solution to this problem is to use permeable pavements which only began to find application in Australia recently. Permeable pavements can facilitate biodegradation of oils from cars and trucks, help rainwater infiltrate into soil, replenish groundwater, allow tree roots to breathe, and reduce flash flooding, but they have not been widely adopted in Australia due to concerns mainly over reduced structural capabilities and clogging. A research project is being carried out at USQ aiming at understanding the influence of pore structures features and particle deposition on clogging resistance and permeability reduction. Clogging is perceived as a major problem for any type of permeable pavement. Even with vigorous maintenance clogging is common. In the paper, some common types of clogging are discussed first, followed by the clogging effect on the performance of porous concrete mainly related to the change of the porosity and the pore structure properties. Testing methods for measuring porosity and hydraulic conductivity which include both physical testing and image analysis are reviewed in detail