Epoxy Bonded Steel Plates Research Articles

Failure of urban subway segments in coastal area and reinforcement effect of bonded steel plate: a case study in China

The construction of metro in coastal areas is prone to safety accidents when it encounters unfavourable geology. Serious water inrush and sand gushing occurred during the construction of the shield tunnel connection channel of Shenzhen Metro Line 20, resulting in extensive deformation and even cracking of the shield segment. With the event as the background, it is conducted in this article with a further analysis of the causes of sand gushing in the connecting channel. Using convergence displacement and crack width as indicators, the shield segments are classified as strong influence zone, moderate influence zone, weak influence zone and no influence zone. Furthermore, by combining numerical simulation and field investigation, the innovative method of epoxy bonded steel plate reinforcement is proposed. In particular, it should be noted that the steel plate needs to be opened at the connection channel, so four small right-angle steel plates are designed to reduce the concentrated stress of the split ring. According to finite element analysis and on-site measurement, it can be known that after the steel plate is reinforced, the internal force of the segment is greatly reduced, and the deformation is stable, which can ensure the safe service of the tunnel. This research provides a new idea for the damaged reinforcement of urban subway segments in coastal areas in the future.

Experimental investigation of the bearing capacity of deformed segmental tunnel linings strengthened by a special composite structure

Steel plate – concrete composite structure (SPCCS) was recently proposed to strengthen shield tunnels. The steel plate serves as the strengthening material. A combination of connectors and steel-fiber reinforced concrete is employed to establish the bond between the strengthening material and the tunnel lining. A full-scale test was conducted to investigate the mechanical behavior and the bearing capacity of the structure. A comparison of the SPCCS strengthening technique with the epoxy-bonded steel plate (EBSP) strengthening technique was conducted, concerning the distribution of the strain of the steel plate, the joint opening, the bolt strain, slippage, the stripping value, the failure mechanism, and the overall strengthening benefits. The results are shown as follows: for the shield lining, strengthened by the SPCCS technique, the effectiveness of the bond increases, which renders acting of the individual structural components in combination with the tunnel lining more efficient, resulting in the full use of the components of the strengthening device. The failure mode of the strengthened structure is characterized by a high degree of ductility. Compared with EBSP strengthening, the SPCCS strengthening technique results in a reduction of the amount of steel, but in an increase of the bearing capacity and the ductility.

EBR Strengthening Technique for Concrete, Long-Term Behaviour and Historical Survey.

Epoxy bonded steel plates (externally bonded reinforcemen: EBR) for the strengthening of concrete structures were introduced to the construction industry in the late 1960s, and the use of fibre reinforced polymers (FRPs) was introduced in the 1990s, which means that these techniques have already been used in construction for 50 and 25 years, respectively. In the first part of the paper, a historical survey of the development and introduction of these strengthening techniques into the construction industry are presented. The monitoring of such applications in construction is very important and gives more confidence to this strengthening technique. Therefore, in the second part of the paper, two long-term monitoring campaigns over an extraordinarily long duration will be presented. Firstly, a 47-year monitoring campaign on a concrete beam with an epoxy bonded steel plate and, secondly, a 20-year monitoring campaign on a road bridge with epoxy bonded CFRP (carbon fibre reinforced polymers) strips are described. The paper is an expanded version of the paper presented at the SMAR2017 Conference.

Strength and ductility of simple supported R/C beams retrofitted with steel plates of different width-to-thickness ratios

The concept of strengthening reinforced concrete beams using epoxy-bonded steel plates (EBSP) is a well-known solution in structural engineering, however, there is little information about the effect of the width-to-thickness ratio of steel plates on the behaviour of steel–concrete composite beams. This paper presents an experimental study of the flexural behaviour of under-reinforced concrete beams, strengthened in flexure by externally-bonded steel plates (EBSP) of varying width-to-thickness ratios. A total of 23 reinforced concrete beams were tested; 6 beams in Series 1 tests and 17 beams in Series 2 tests. One beam in Series 1 tests and two beams in Series 2 tests were regarded as control specimens, whilst the remaining beams were strengthened with steel plates of different width-to-thickness ratios. In each group, the width of the bonded steel plate varied from 75 mm to 175 mm, in increments of 25 mm. The beams were tested as simply supported, under two-point static loadings until failure. From the experimental results, it was observed that the externally bonded steel plates led to substantial increase in flexural stiffness, which resulted in an increase in the capacity and cracking load of the strengthened beams and a decrease in vertical deflections and crack-widths, compared to the control beams. It was also found that the width-to-thickness ratio of steel plates as low as 12.5 can promote flexural yielding and extensive ductility in strengthened beams.

Experimental investigation of the ultimate bearing capacity of deformed segmental tunnel linings strengthened by epoxy-bonded steel plates

In order to develop an effective method to increase the load-bearing capacity of deformed segmental tunnel linings, full-scale tests concerning the ultimate bearing capacity of the linings, strengthened by steel plates, were conducted. The design of the tested linings and the loading scheme are described in this paper. In addition to the bearing capacity, the failure mechanisms of the tested linings were investigated. It was found that bonding of steel plates to the deformed segmental tunnel linings is an effective and practical method for strengthening segmental tunnel linings, thereby enhancing both their ultimate bearing capacity and their overall stiffness. The behaviour of these structures under loading is similar, no matter whether they are strengthened by full-ring or so-called semi-ring steel plates. The failure of the strengthened linings is the consequence of local failure of the bond between the steel plates and the tunnel segment. Therefore, the success of the proposed strengthening method strongly depends on the bonding capacity.

Experimental investigation of the ultimate bearing capacity of deformed segmental tunnel linings strengthened by epoxy-bonded filament wound profiles

A new strengthening method employing epoxy-bonded filament wound profiles (FWPs) has been applied to shield tunnels subject to large deformation. Full-scale tests were conducted on the ultimate bearing capacity of linings strengthened by the new method. With consideration for secondary loading, the strengthening measures were applied when the lining deformation reached 120 mm (0.02D). The failure phenomena are described, and the main loading process results were obtained, including load-displacement curves, cracking, and joint openings. The failure mechanisms, the key performance points, and bearing capacities of the tested strengthened linings are discussed and analysed. In addition, a comparison was made between two FWP strengthening methods as well as with epoxy-bonded steel plate strengthening methods. The results show that the epoxy-bonded FWP method is effective and practical for strengthening segmental tunnel linings, which can improve both the ultimate bearing capacity and overall stiffness of the structures. The failure of the strengthened linings is primarily caused by bond failure between the FWPs and the concrete lining segments, indicating that the bonding capacity of the adhesive is of great importance when utilising the proposed strengthening method.

Simplified nonlinear simulation of shield tunnel lining reinforced by epoxy bonded steel plates

A high-efficiency simplified modeling approach based on fiber-beam elements and discrete elements is proposed for investigating the nonlinear response of shield tunnel reinforced concrete linings. The proposed approach focus on following main features: modeling simplicity and computational efficiency, the considerations of critical material and geometric nonlinearity associated with the entire loading process, including the stage of reinforcing the deformed concrete lining by steel plates. Comparison between the analysis results of the proposed numerical model and the experimental results from the full-scale structural test are presented to validate the developed model. The results show that the proposed model can capture the essential characteristics of the nonlinear load–deformation response of segmental tunnel lining. The modeling approach presents a balance between simplicity and accuracy, and serves as a viable alternative to detailed finite elements analysis.

Dispersion of ultrasonic surface waves in a steel–epoxy–concrete bonding layered medium based on analytical, experimental, and numerical study

The epoxy-bonded steel plate strengthening method has been widely applied in retrofitting reinforced concrete structures. However, using epoxy as the adhesive will bring deterioration due to its aging and delamination. Ultrasonic Nondestructive Evaluation (NDE) is an advantaged approach to detect the delamination or the bonding quality of the layered medium. The elastic property of the adhesive material can also be estimated properly by obtaining the phase velocity of surface wave through NDE test. This research proposes an approach to estimate the elastic property of epoxy layer in a steel–epoxy–concrete bonding layered medium. By solving dispersion equations, the analytical dispersion curves are plotted. Then the influence factors to the modes and shapes of those dispersion curves are discussed. An ultrasonic NDE test on a specimen is conducted, by which the relation between phase velocity and frequency is obtained. Through inversion process, the elastic property of epoxy layer is estimated. Based on the estimated elastic constants, a numerical study of steel–epoxy–concrete layered medium is also conducted using Explicit Finite Element Method, from which the numerical dispersion curves are obtained. Through analytical, experimental, and numerical studies, the dispersion property of surface waves in the layered medium is well understood.

Three-dimensional finite element analysis of reinforced concrete slabs strengthened with epoxy-bonded steel plates

This paper presents a nonlinear finite element analysis(FEA) in order to investigate the flexural performance of one-way slabs strengthened by epoxy-bonded steel plates. Four point loading scheme is selectively chosen. A model is developed to implement the material constitutive relationships and non-linearity. Five Slabs were modeled in FEM software using ABAQUS. One slab was un-strengthened control slab and the others were strengthened with steel plates with varying the plate thickness and configuration. In order to verify the accuracy of the numerical model, a comparison was done between the experimental results available in the literature and the proposed equations by ACI 318-11 for the calculation of ultimate load capacities of strengthened slabs, the agreement has proven to be good and FEA attained accurate results compared with ACI code. A parametric study was also carried out to investigate the influence of thickness of steel plate, strength of epoxy layer and type of strengthening plate on the performance of plated slabs. Also, the practical and technical feasibility of splitting the steel plate in strengthening process has been taken into account. For practical use, the author recommended to use bonded steel plate as one unit rather than splitting it to parts, because this saves more effort and reduces the risk of execution errors as in the case of multiple bonded parts. Both techniques have nearly the same effect upon the performance of strengthened slabs.

Compactness Inspection Methods for Epoxy-Bonded Steel Plates of Bridge Strengthening

Construction quality of epoxy-bonded steel plates is not easy to check for absence of inspection standard in situ. In this paper inspection methods of the critical evaluation factor-bond compactness of epoxy- bonded steel plates, hammer test based multi-level grids and infrared holography, are proposed by theory analysis ,specimen experiments and practical validation in engineering. In final he suggestion on the practical usage of these two methods are also presented.

Shear strengthening of reinforced concrete beams using epoxy bonded steel plates, CFRP sheets and externally anchored stirrups

This research presents the effectiveness of different shear strengthening methods using epoxy bonded steel plates, steel strips, carbon fiber reinforced plastics (CFRP) sheets and externally anchored stirrups for enhancing the shear strength of RC beams. In this study, an experimental program including two series of twelve specimens was carried out to investigate the behavior of RC beams strengthened with the above methods. Further, a numerical analysis using finite element method (FEM) was performed to simulate the behavior of strengthened beams. The effectiveness of using epoxy bonded steel plates, CFRP sheets and externally anchored stirrups for shear strengthening of RC beams is confirmed through both numerical and experimental results.

Shear strengthening of reinforced concrete beams using various techniques

This paper presents the results of an experimental investigation for enhancing the shear capacity of reinforced concrete beams using different techniques. A total of eleven beams were tested in this program. Two series of beams were designed; in the first series, beams were designed in such a way that the strengthened beams fail in ductile flexural mode thereby avoiding the brittle shear failure. The second series of beams were designed to fail in shear mode; to assess the actual increase in shear strength by devised strengthening techniques. Two beams were kept as control beams; whereas other beams were strengthened with steel brackets, steel plates, vertical strips and externally anchored stirrups. All techniques were found effective in enhancing the shear strength of beams. However, the externally anchored stirrups were found to be the most effective. Beam strengthened using this technique failed at a load almost 117% higher than the control beam. The epoxy bonded steel plates provided an average of 72% increase in shear capacity as compared to the control beams.

Shear strengthening of RC beams with web-bonded continuous steel plates

This paper presents the results of an experimental program and a parametric study conducted on RC beams strengthened in shear with web-bonded continuous steel plates. An experimental investigation was conducted to assess the effectiveness of web-bonded continuous steel plates for shear strengthening of RC beams having internal stirrups. A two-dimensional nonlinear finite element model was developed to simulate the overall behavior of beams with epoxy bonded steel plates. In order to develop a design methodology for beams with web-bonded steel plates, a parametric study was conducted. Main parameters considered were concrete strength, plate thickness, plate depth-to-beam depth ratio, yield strength of steel plates, beam size and the internal shear reinforcement ratio. A formula to compute the shear strength of such beams was proposed by adding up the concrete contribution, shear reinforcement contribution and the contribution of steel plates. The validity of proposed formula was checked against the results from parametric study and the experiments. It was found that the proposed formula predicts the ultimate shear strength of RC beams with web-bonded continuous steel plates very well.

Nonlinear Finite Element 2D Analysis for RC Beams Strengthened by Epoxy Bonded Steel Plates

ABSTRACTThis paper presents the nonlinear finite element modeling of the global behavior for RC beam strengthened by externally epoxy bonded steel plates up to failure. In addition to the consideration of nonlinear behavior and cracking of concrete, the model involves interface element to capture not only the shear and normal stress concentration at the plate curtailment, but also the separation due to the exceeded peak shear and normal stress. The internal steel bar using truss element and the external steel plate using deformation theory of plastic have been confirmed by compare finite element solution with plastic theory. The proposed finite element solutions result in close correlation with experimental data available for RC beams strengthened by epoxy bonded steel plates with different thickness.

Numerical simulation of steel-plate strengthened concrete beam by a non-linear finite element method model

Strengthening with epoxy bonded steel plate is one of the most widely used techniques for flexural upgrading of reinforced concrete (RC) beams. However, debonding failure at the plate cut-off zone and or in the vicinity of flexure and shear cracks leads to catastrophic failure of the upgraded beams. This particular failure depends on several factors such as the distance of plate curtailment from the support, plate thickness and the provision of end anchors. Since the conventional beam theory cannot predict the debonding failure of such beams, a finite element model capable of predicting the overall behavior of strengthened beams including different failure modes accurately is developed. This paper presents the formulation of finite elements and material models and simulation results of some RC beams tested for flexural strengthening with epoxy bonded steel plates.

Effect of Environmental Exposure on the External Strengthening of Concrete with Composites-Short Term Bond Durability

The pressing need for rehabilitation and retrofit strategies that encompasses new and emerging materials and technologies, results from the need to simultaneously repair existing structures while attempting to increase both their performance levels and life spans. A large number of techniques currently exist for strengthening highway bridges ranging from the use of external post-tensioning to the addition of epoxy bonded steel plates to the tension surface. The use of composite plates for the purpose of external reinforcement has considerable potential. However, there is a critical need to investigate the degradation of the composite-concrete interface after exposure to environmental conditions that include moisture, sea water, freezing and freeze-thaw. In this investigation, the effect of five different environmental conditions on the performance of plated beams is considered from aspects related to materials and durability. It is shown that the selection of the appropriate resin system is critical to success, and the dangers of selecting systems with low glass transition temperatures and drastic drops in instantaneous modulus as a function of temperature are discussed. Two different resin systems are compared using the same fibrous reinforcement and an overall view of durability at the concrete-composite interface is elucidated.

Computational model for reinforced concrete beams strengthened by epoxy bonded steel plates

This paper presents a nonlinear finite element model for the flexure-shear response of reinforced concrete (RC) beams strengthened externally by epoxy bonded steel plates. The model includes a special interface element to simulate the thin epoxy adhesive layer and which allows for the metamorphosis of failure mode from plate yielding to separation as the plate thickness t p is increased. The numerical results show close correlation to experimental data available for an RC beam strengthened by plates of various thickness.

RELIABILITY OF EPOXY BONDED STEEL PLATE METHOD FOR REPAIRING DAMAGED RC SLABS OF BRIDGE

Epoxy bonded Steel Plate Method is a reinforcement method for repairing cracked and damaged RC slabs of bridge. In the method, a steel skin plate is adhered to the bottom surface of damaged concrete slab with epoxy resin.The aim of this paper is to examine the reliability of this method. Model slabs were tested under the repetition of truck wheel loading in both the states before and after repairs. From various observations on deflection-growth, cracking in concrete, and strain-increase in steel bar and skin plate, it is concluded that the method is fairly reliable even if the repair is done at the stage of so severe damage as to cause diagonal tension (shear) cracks in the concrete section of slab.

The analysis of reinforced concrete beams strengthened by epoxy bonded steel plates

An analytical method for the elastic analysis of the interaction between a concrete beam and a steel plate bonded to it by epoxy adhesive is presented. The shear and the peeling distributed forces induced into the epoxy are formulated. It is observed that large shear and peeling distributed forces are induced into the epoxy at a samll region at the edges of the steel plate. The cases where large tensile distributed peeling force is induced, are discussed.

Strengthening of concrete bridge decks with epoxy-bonded steel plates

An example of the use of bonded steel plates to strengthen a motorway bridge complex is described. Full-scale loading tests demonstrated that the required structural improvements had been achieved, and associated laboratory tests confirmed short-term strengthening effects. Uncertainties about long-term durability have led to an extensive programme of weathering tests. Early results from small-scale tests indicate the possibility of slightly reduced bond efficiency due to internal corrosion and indicate the need for improved anti-corrosion treatment to ensure a long trouble-free life.