External Steel Plates Research Articles

콘크리트 교량의 보강을 위한 온도 프리스트레싱 공법의 실험적 연구

Traditional external post-tensioning method using either steel bars or tendons is commonly used as a retrofitting method for concrete bridges. However, the external post-tensioning method has some disadvantages such as stress concentration at anchorages and inefficient load carrying capability regarding live loads. Thermal prestressing method is a newly proposed method for strengthening and rehabilitation of concrete girder bridges. Founded on a simple concept of thermal expansion and contraction of steel, the method is a hybrid method of external post-tensioning and steel plate bonding, combining the merits of two methods. In this paper, basic concepts of the method are presented and an illustrative experiment is introduced. From actual experimental data, the thermal prestressing effect is substantiated and the FEM approach for its analysis is verified.

Effect of variations in the plate modulus of elasticity on the failure modes of FRP plated R.C. beams

In the absence of FRP plate/glue/concrete interface bond failure (i.e. interfacial debonding), eight possible flexural modes of failure are identified for reinforced concrete beams experiencing lateral loading, and strengthened in flexure with external FRP or steel plates glued to their soffits. All possible changes in such modes of failure, as a result of variations in the modulus of elasticity of the FRP material (assuming an associated constant value of ultimate tensile strength for the FRP plate in a given beam design), have been addressed in some detail, with a quantitative treatment of the critical values of the FRP modulus of elasticity associated with various failure mode transitions (i.e. changes).

Structural assessment of externally flexural strengthened reinforced concrete beam after repaired with polymer mixture

This study investigated the effectiveness of external strengthening technique. The experimental variables were the strengthening material and overlay materials using polymer mixtures. Beams considered in this study are the ones strengthened either with external steel plate or carbon fiber sheet (CFS) bonded to the overlay soffit or with reinforcing rebars in the overlay. An analytical method based on the nonlinear layered finite element method is used to simulate the load–deflection behavior of strengthened beam. The theoretically obtained load–deflection relationships and strains of the strengthened beams are compared to the corresponding experimental values. Efficiencies of the repairing techniques are evaluated by comparing the approximate measures on the cumulative slips. Parametric studies are then obtained using the developed model to investigate the effects of design variables on the overall flexural behavior of the strengthened beam. Simply supported beams under monotonically increasing symmetrical loads are considered exclusively.

Experimental and numerical studies of external steel plate strengthened reinforced concrete coupling beams

This paper aims to develop a new method for strengthening reinforced concrete (RC) coupling beams. Experiments were conducted to test three full-scale RC coupling beams, of which two were strengthened by bolted external steel plates on the side faces of the beams and the other one acted as a control specimen without strengthening. The improvements to strength, deformation and energy dissipation of the external plate strengthened RC coupling beams were observed from the experimental results. Nonlinear finite element analysis was carried out to model the strengthened and non-strengthened coupling beams. The material properties used for concrete and reinforcement in the numerical analysis were validated by the laboratory tests. As the experimental study showed that there was a small slip between the bolted connection and the concrete wall pier, a bilinear model was used to simulate the load–slip behaviour of the bolt connections. The model was calibrated by the experimental results from the plate strengthened coupling beams. A numerical parametric study found that the small slip (>3 mm) between the bolt connection and the concrete wall could significantly affect the load-carrying capacity of the bolt connections as well as the structural performance of the strengthened coupling beams. The numerical model developed is very useful for investigating strengthened beams with other configurations and other reinforcement details.

Strengthening of critically designed girders with dapped ends

Reinforced concrete (RC) beams with dapped ends are frequently found in bridge girders and precast concrete construction. A reduction in depth near the supports tends to produce a stress concentration and hence requires special analysis and detailing of any reinforcement used. Improper dimensioning and distribution of reinforcing steel can lead to undesirable cracking and failure mechanisms that need to be predicted in order that a proper strengthening system be applied. The experimental programme described in this paper incorporated 52 specimens with dapped ends; three main defects were intentionally introduced at the recess zone and 12 different strengthening techniques were applied. The defects included an inadequate development length of bottom longitudinal reinforcement at the dapped ends, and elimination of either horizontal or vertical shear reinforcement at the ends. External bonding of the steel angle at the reentrant corner, unbonded bolt anchoring, external steel plate jacketing, exterior carbon fibre wrapping and/or stripping were applied in order to determine the best strengthening technique. A strut-and-tie model was used in the analysis of such discontinuity regions and a strength enhancement index procedure was introduced. A comparative study was undertaken in order to evaluate the various strengthening techniques applied.

Strengthening of critically designed girders with dapped ends

Reinforced concrete (RC) beams with dapped ends are frequently found in bridge girders and precast concrete construction. A reduction in depth near the supports tends to produce a stress concentration and hence requires special analysis and detailing of any reinforcement used. Improper dimensioning and distribution of reinforcing steel can lead to undesirable cracking and failure mechanisms that need to be predicted in order that a proper strengthening system be applied. The experimental programme described in this paper incorporated 52 specimens with dapped ends; three main defects were intentionally introduced at the recess zone and 12 different strengthening techniques were applied. The defects included an inadequate development length of bottom longitudinal reinforcement at the dapped ends, and elimination of either horizontal or vertical shear reinforcement at the ends. External bonding of the steel angle at the reentrant corner, unbonded bolt anchoring, external steel plate jacketing, exterior carbon fibre wrapping and/or stripping were applied in order to determine the best strengthening technique. A strut-and-tie model was used in the analysis of such discontinuity regions and a strength enhancement index procedure was introduced. A comparative study was undertaken in order to evaluate the various strengthening techniques applied.

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.

A Semi-active Oleodynamic Damper for Earthquake Control. Part 1: Design, Manufacturing and Experimental Analysis of the Device

Within an experimental research project financed by the European Union, a prototype semi-active oleodynamic damper has been conceived and manufactured in Italy starting from technology today currently adopted for passive energy dissipation devices. The new device was obtained by just adding two identical electrovalves and an external oleodynamic circuit to a commercially available silicon oil damper. Static and dynamic tests performed on the damper allowed to determine its stiffness and energy dissipation characteristics when passively operating (both electrovalves are always closed or open) as well as to measure the release and insertion times of the electrovalves during opening and closing tests. The experiments indicated a non-linear quadratic viscous constitutive law for the damper as well as operating times of electrovalves in good agreement with specifications given by the manufacturer. A semi-active assembly composed by the prototype damper and external flexible steel plates was then mounted and subjected to further tests in order to definitively characterize through a simple mathematical model the entire system and to completely identify its operating delays and their physical sources.

Strength of reinforced concrete columns bonded with external steel plates

Rehabilitating reinforced concrete elements using external steel plates has been applied to both beams and slabs in bridge and building construction over the last two decades. The effect of applying external steel plates increases the strength of beams and slabs. This technique can also be applied to reinforced concrete columns to increase their strength with a minimal increase in the cross-sectional dimensions of the member. This article presents an experimental programme used to ascertain the behaviour of both short and slender columns. These columns had steel plates bonded to them by the use of both bolting or gluing and bolting. A simplified theoretical model based on composite construction techniques is then presented and calibrated with the experiments to determine the strength increase and recommendations for further research are then made.

Strength of reinforced concrete columns bonded with external steel plates

Strength of reinforced concrete columns bonded with external steel plates

External steel plate systems for the shear strengthening of reinforced concrete beams

Attaching steel plates to the external surfaces of concrete beams can provide a practical solution to the upgrading of existing structures. When plates are fixed to the sides (web) of a beam a large increase in the shear capacity can be realised. The experimental results from two methods of plate attachment, namely adhesive bonding and bolting, are examined and compared. A method of analysis, based on the equilibrium of forces along the critical section, is proposed.

Fatigue Performance of Concrete Beams Strengthened with CFRP Plates

Recent increases in bridge design loading requirements have highlighted the need for fast, efficient, and durable strengthening methods. External steel plate bonding provides a satisfactory solution, but carbon fiber reinforced plastic (CFRP) offers the added advantages of resistance to corrosion, low weight, and high mechanical strength. This paper examines the fatigue performance of CFRP-strengthened concrete beams as part of a project investigating the use of CFRP as an alternative to steel. Five reinforced concrete beams were tested in fatigue; two control beams and three strengthened with externally bonded CFRP plates. Three loading options were used: (1) apply the same loads to both plated and unplated beams, (2) apply loads to give the same stress range in the rebar in both beams, and (3) apply the same percentage of the ultimate load capacity to each beam. Fatigue fracture of the internal reinforcement steel would appear to be the dominant factor governing failure, and it would appear reasonable to expect the same fatigue life for plated and unplated beams with comparable values of stress range in the steel bar.

Fatigue Performance of Concrete Beams Strengthened with CFRP Plates

Recent increases in bridge design loading requirements have highlighted the need for fast, efficient, and durable strengthening methods. External steel plate bonding provides a satisfactory solution, but carbon fiber reinforced plastic (CFRP) offers the added advantages of resistance to corrosion, low weight, and high mechanical strength. This paper examines the fatigue performance of CFRP-strengthened concrete beams as part of a project investigating the use of CFRP as an alternative to steel. Five reinforced concrete beams were tested in fatigue: two control beams and three strengthened with externally bonded CFRP plates. Three loading options were used: (1) apply the same loads to both plated and unplated beams, (2) apply loads to give the same stress range in the rebar in both beams, and (3) apply the same percentage of the ultimate load capacity to each beam. Fatigue fracture of the internal reinforcement steel would appear to be the dominant factor governing failure, and it would appear reasonable to expect the same fatigue life for plated and unplated beams with comparable values of stress range in the steel bar.

A comparison of two methods for resistivity measurements on repair mortar for cathodic protection systems

This Note presents the theory and application of two methods for measuring the electrical resistivity of repair mortar for use in cathodic protection systems. One method employs the use of steel pins embedded within the sample and the other uses external steel plates placed on the sides of the sample. It is shown that, if the correct geometry of pin arrangement is chosen, the results obtained using both methods compare favourably.