Application Of FRP Research Articles

Seismic Response of URM Walls Strengthened with FRP Reinforced Coating

A set of individual URM walls as well as an assemblage of a three-storey URM hollow clay block masonry structure composed of two shear- and two cross-walls have been tested in original and strengthened state. As a method of strengthening, the coating of the walls, consisting of glass fiber reinforced polymer (GFRP) grid laid in fiber reinforced cementitious mortar matrix (sometimes called textile reinforced mortar), anchored to the walls with glass fiber anchors, has been used. All specimens were subjected to constant vertical load simulating the effect of gravity loads and cyclic horizontal displacements with step-wise increased amplitudes, induced either at the top of the walls or at the floor levels of the assemblage, simulating the effect of seismic loads.The observed behaviour and failure mechanisms were of the shear type. The results show that by the application of FRP reinforced coatings, the seismic performance of URM structures can be significantly improved. As the results of experiments indicate, the energy dissipation, displacement capacity and shear resistance of URM increase substantially. In this regard, adequate anchoring of coating to the masonry and into the r.c. floor structures is essential.

Application of carbon FRP for fatigue strengthening of old steel structures

The traffic requirements on the existing infrastructure are rising still. This coupled with its age puts a strain on it. This is especially problematic for old steel bridges. Higher and more frequent loads will lead to development of fatigue damage to those structures. This causes an issue for the infrastructure owners as the existing methods of repair are difficult, time consuming and expensive. So there is a need to find some easier alternatives. One of such can be the use of carbon fibre reinforced polymers (CFRP). They are being successfully used for repairs and strengthening of concrete structures however their use with steel is still relatively new.The purpose of this work is to establish how does a deteriorated steel reinforced with CFRP behave under fatigue loading. To test this a series of experiments was designed. With the help of a preliminary numerical study the dimensions of the specimens and the applied loading was established. There are two sets of specimens. With both we are using mild steel and each set has different level of surface deterioration (corrosion pits or corrosion holes). The specimens are reinforced using hand laid wet layup composites. They are subjected to fatigue loading and the difference between the fatigue life reinforced and unreinforced specimens is observed. Based on the preliminary study, it is expected, that the reinforcement will prolong the life expectancy by half.

Wood as a Technical Material for Structural Vehicle Components

The application of molded wood parts as an alternative, innovative and sustainable multi-material system (MMS) for structural, resource-efficient and sustainable components within the body shell is a new approach in light-weight constructions. In many of the cases where a structural application of FRP is being considered, they can principally be substituted by wood-based MMS. Although there are great challenges; wood has the potential to fulfill the demands of the present technical appliances and social requirements. Actual results offers the first systematic approach to use wood in structural applications. The main properties and demands, which correspond with those of the specific original structural components, could be met. So, as regarding performance and reproducibility, it is possible to apply a wood-based material in technical appliances. Furthermore, material models have been designed and concepts for the repair and recycling of the wood-based MMS were developed.

Some Aspects of CFRP Steel Structures Reinforcement in Civil Engineering

The FRP materials application in various branches of technology is under examination for at least for about half a century. In civil engineering the most attention was given to practical aspects of FRP application for RC (reinforced concrete) elements strengthening. As for steel structures there is much less done in this field, high elastic modulus of steel being one of the critical points for this delay. Bonding between the adherents represents another problem point when dealing with the FRP reinforcement of steel structures. In RF there are few works concerning this problem.In this paper the case of axial tension is considered and formulae for the ultimate bonding layer length and other parameters are given with worked numerical examples. Also some prospects of application of CFRP in building are discussed.

Mechanical behavior of concrete–resin/adhesive–FRP structural assemblies under low and high temperatures

The application of FRP to the strengthening of existing reinforced concrete structures entails the inevitable exposure of the layered structure to temperature changes. This paper takes another step in investigating the behavior of the structural assembly under the combined effect of temperature change and load. The investigation tests double lap shear joints a temperature-controlled chamber under temperatures in the range of −40–120°C. Two FRP systems are examined. The first combines unidirectional carbon fiber sheets and epoxy resin applied in a wet lay-up technique, and the second uses pre-fabricated FRP strips or laminates applied by an adhesive bonding technique. The emphasis in this paper is on the response of the layered structure to the combined mechanical and environmental loading. The experimental sections of the paper characterize the mechanical properties of the resin used in the wet lay-up system and the adhesive used in the bonded system under the examined range of temperatures. Next, the paper explores the response of the two assembled FRP–adhesive/resin–concrete systems under the thermo-mechanical load. The analytical section of the investigation also includes two phases. First, the paper examines three empirical formulae for the assessment of the failure load. Then, the paper investigates the results of an analytical approach that uses a high-order fracture mechanics model. The experimental and analytical results reveal a gradual degradation under both low and high temperatures and a behavior that is different from the glass transition effect, which characterizes certain components of the layered system.

An experimental study on reinforced concrete beams strengthened with prestressed near surface mounted CFRP strips

Externally-bonded prestressed FRP plates and near surface mounted (NSM) FRP strips are two important techniques of strengthening concrete structures with FRP materials. However, there are considerable limitations for these two techniques. Using prestressed NSM FRP strips can combine the advantages of these two strengthening methods and it thus becomes very attractive to further promote FRP applications in retrofitting concrete structures. In this paper, a total of 7 rectangular reinforced concrete beams were constructed for static load tests, of which 1 specimen was the reference beam and the other 6 beams were strengthened with FRP strips. The behavior and failure modes of these specimens were investigated, the difference of the mechanical performance due to various strengthening techniques was compared, and the effect of parameters, such as the bond length, prestressing force, and the anchorage, on the behavior and failure modes of specimens was analyzed. The testing results showed that the load-carrying behavior of flexural members could be improved significantly by strengthening with prestressed NSM FRP strips, since the highest load-carrying capacity of the beam with prestressed NSM strips is increased by 122% and 44.2% when compared to the beam without strengthening and with non-prestressed FRP strips, respectively. While the prestressed FRP strips could be anchored by epoxy through the near surface mounting, the failure modes of beams strengthened with this technique might be the debonding of epoxy- concrete interface and delamination of the concrete cover. It was proven that these failure modes can be avoided by extending the bond length of FRP strips or using U-wraps of CFRP sheets. The stress transfer length of the prestressed-FRP strengthened beam with U-wrap anchorage is approximately 100mm.

Investigation of Material and Manufacturing Process to Develop High Pedestrian Safety Composite Bonnet

Cost reduction, light weighting, quality and safety are the basis for all design and development of automobile component manufacturing. Low cost with high quality components can be produced by proper material selection, material cost, production volume, manufacturing process. This paper investigates the existing metallic bonnet with a new low cost and light weight composite bonnet. Fibers such as glass and jute along with matrixes of polyester and epoxy resin are selected for part fabrication. Using reverse engineering process design is extracted from original metallic bonnet and is redesigned for FRP application. Hand lay-up and VARTM manufacturing process are compared to fabricate FRP bonnet. Important factors that involve in bonnet under real time damages are impact of child head-form during accident is analyzed as per Euro-NCAP standard. From the result VARTM based glass/ polyester composite is found to be a better candidate for fabrication. Keywords: Predestrain safety, Reverse enginneering, hand layup, VARTM, Analysis.

Research on the FRP bridge girder under static load

The CFRP composite materials due to their excellent mechanical properties are more and more often used in civil engineering. In recent more than ten years one could have observed f.e. much more wider application of FRP in bridge construction. The main goal of the ongoing research project was to develop and demonstrate FRP composite bridge girder, including their technical design, material research, manufacturing technique selection and structural testing on full scale model. The objective of the paper is the development and research on a new FRP bridge girder fabricated by VARTM manufacturing technique. The reduced scale prototype girder with the total length of 13,5 m was tested to evaluate its carrying capacity, overall behavior under ultimate static load, as well as modes of failure. The girder met the prescribed serviceability and safety criteria and is likely to be implemented on-site soon for bridge construction. The output of the research project gives a very promising future for the FRP application in bridge engineering.

Research of Seismic Design Method of RC Frame Structure Retrofitted by FRP

According to the research data and achievements home and abroad, this paper puts forward the practical seismic design process and method of RC frame structure retrofitted by FRP, to promote the application of FRP in the field of RC frame retrofitting. And the ductility design of the column, the reinforcement design of the node area and the structures integral seismic action are discussed, providing a reference for future research and engineering application.

Current Situation and Prospect of the Application of FRP in Material Engineering

The FRP composite material can replace the traditional under certain conditions, the wood structure of steel and reinforced materials, with high strength, light weight, resistance to corrosion and fatigue resistance, temperature stability and good special, because by civil engineeringcircles. This paper introduces the characteristics of FRP composites, the application of FRP composites in civil engineering are discussed, finally, the prospect of FRP materials are introduced.

SOME PARAMETERS AFFECTING THE STATIC BEHAVIOR OF NORMAL AND HIGH STRENGTH CIRCULAR R.C. SHORT COLUMNS CONFINED BY CFRP

Concrete columns have an important function in the structural concept of many structures. Often, these columns are vulnerable to exceptional loads (such as impact, explosion or seismic loads) , load increase ( increasing use or change of function of structures, etc.) and degradation ( corrosion of steel reinforcement, alkali silica reaction , etc.). On the other hand, confinement of concrete is an efficient technique to enhance the structural behavior of concrete members primarily subjected to compression .Structural repair and rehabilitation of reinforced concrete structures is becoming an increasing important option for all deteriorated / damaged structures to restore, enhance the load bearing capacity and increase the life span of the structure. The strengthening of concrete structures with externally bonded reinforcement is generally done using either steel plates or FRP laminates. The main disadvantages of using steel plates are steel corrosion in the adhesion zone, heavy weight and excessive size of single plates. With the development of technology , the use of high- strength concrete members has proved most popular in terms of economy, superior strength , stiffness, and durability. With the increase of concrete strength, the ultimate strength of the columns increases, but a relatively more brittle failure occurs. The lack of ductility of high strength concrete results in sudden failure without warning, which is a serious drawback. [1] .The application of FRP in the construction industry can eliminate some unwanted properties of high strength concrete , such as its brittle behavior [2,3]. To study the behavior of normal and high strength circular R.C.columns confined with CFRP under statically load, tests on columns wrapped with FRP have been executed. The efficiency of externally bonded CFRP of circular R.C.columnsis declared and evaluated.

Use of FRP in Egypt, Research Overview and Applications

Advanced Composite Materials, (ACM), have been used in civil engineering applications in Egypt over the last two decades. Significant progress has been made in the use of ACM in the form of fibre reinforced polymers, (FRP), to repair, rehabilitate and upgrade aging or damaged structures. Egypt has released its national code for design and application of FRP in construction fields addressing both externally bonded and internal FRP reinforcement in concrete elements. As a result, the use of FRP for repair, strengthening and retrofitting of structures have become a very well accepted practice in Egypt. The code has been issued after a series of successful rehabilitation projects and extensive studies at different research institutions in Egypt. This paper presents a general overview on samples of the research activities in Egypt for using FRP in strengthening concrete structures. FRP laminates are applied for strengthening slabs or beams in flexure and shear as well as for confinement of reinforced concrete, (RC), columns. Different research programs carried out in Egypt in the field of FRP are presented. This research is an outcome of collaboration between different universities and research institutes in Egypt. The paper also presents field applications of FRP strengthening of special structures in Egypt. Selected projects utilizing ACM in the form of externally bonded FRP laminates to strengthen existing reinforced concrete structures are presented. Historical buildings such as the Egyptian Museum and Kaitbay Fence were rehabilitated after distress/deterioration caused by corrosion of steel reinforcement and lack of maintenance. Design concepts and constructional details are presented for each project.

FRP Truss Bridge Construction Technology Research and Application

For the rapid erection of FRP truss bridge, based on the FRP material characteristics, it was put forward to a suitable FRP truss bridge construction hoisting technology. Hoisting technology was divided into two types: integral hoisting and segment hoisting. This article mainly researched and analyzed the aspect of the selection of hoisting scheme, the selection of hoisting equipment and hoisting point, expounded emphatically the selection principle and method of hanging point when hoisting, and checked hoisting point in different cases. Certain references were provided for the subsequent FRP truss bridge hoisting erection.

Influence of surface roughness on the bond of FRP laminates to concrete

The potential of Fiber Reinforced Polymer FRP in the reinforcement of concrete structures has been shown in many studies and practical applications. However, few works have been focused systematically on the development of quantitative criteria to measure surface roughness and relate this parameter to the debonding stress. Roughness has a direct influence on the FRP performance in terms of bond to concrete, which is important to ensure the effectiveness of the external FRP reinforcement. Currently, there is not much evidence about the parameters related to surface state of concrete structures nor many guidelines about assessing the optimal conditions of concrete surface for the application of the FRP. To respond to these needs, the presented study deals with the effects of the surface characteristics of concrete on debonding strength of the FRP; this objective has been pursued by means of experimental tests on concrete specimens characterized by different levels of roughness of the concrete surface. The paper describes the experimental campaign outlining the analyzed surface preparation procedures (i.e., sandblast, bush-ammering, grinding, brushing) and the subsequent tests performed on the installed FRP by means of two different test methods. The former is a laboratory method which performs shear tests to evaluate the debonding shear strength of the FRP reinforcement; the latter is pull-out test which is a typical method used for in situ check of quality of the FRP application. The results of these experimental tests are discussed in the paper with emphasis on the correlation between the roughness of the surface and the outcomes of both shear and pull-out tests; this information can be used in design in order to prescribe the minimum roughness level necessary to attain the expected debonding strength of the reinforcement.

Application of FRP in Geotechnical Engineering

As FRP composite has a series of advantages such as higher strength weight ratio , higher rigidity weight ratio ,erosion resistance , no magnetism and high durability , it has being widely used in civil engineering ,its main characters and applications in geotechnical engineering are introduced in this article.

Research on Factors Affecting Durability and Improvements for FRP Reinforced Concrete Structures

With wide applications of FRP in civil engineering, it is necessary to study the durability of FRP reinforced concrete structure. Based on the related research both at home and abroad, the factors affecting durability of FRP reinforced concrete structures and the corresponding improvements have been put forward by analyzing the durability of concrete, FRP materials and reinforced structures, respectively.

전단 보강이 없는 FRP RC보의 전단강도 예측

There are many problems in application of FRP reinforcing bars as shear reinforcement, since bending of FRP bars is not a feasible process on construction site. Even though FRP bars can be manufactured in bent shape, they have lower strength at bent location. However, there are no serious problems to use FRP bars as flexural reinforcement. Plates or slabs like bridge decks, in general, do not need shear reinforcements. These types of members with FRP flexural reinforcement have lower shear strength than those with conventional steel flexural reinforcement. However, reliable process or equation for shear strength estimation of FRP reinforced concrete without shear reinforcement are not established, yet. In this study, predicted shear strength obtained from available design equations and assessment equations are compared with 211 experimental results. The results showed that among the current design codes, the Architectural Institute of Japan (AIJ) and the Institution of Structural Engineers (ISE) provided the best estimation. ACI 440.1R-06 provided conservative results with degree of dispersion similar to that of ISE. In addition, regression analysis on the collected experimental results was conducted to develop regression models. As a result, a new reliable shear strength equation was proposed.

Relaxation Behavior of Clamping Force in Bolted Joints of Pultruded GFRP Laminates

The relaxation behavior of clamping force in friction-type FRP bolted joints is one of the significant subjects in application of FRP to structures. The aim of this paper is to obtain the factors of relaxation behaviors in the GFRP bolted joints based on the experimental results. The relaxation behaviors are due to both steel bolt and GFRP laminate. Steel bolt dominates the relaxed force immediately after initial loading but not reloading. The relaxation factors of GFRP laminate except matrix polymer could be both laminate surface geometry and laminate bond, considering the variance of relaxed force and more relaxed force for bonded laminate than single laminate observed in the experimental results. Boltzmann superposition principle can be hardly applicable to the relaxed forces for initial loading and reloading, suggesting that less relaxed force for reloading could be obtained by the strain hardening of bolt threads through the decrease of cross section area due to shear plastic deformation and that surface geometry could be modified by plastic and irreversible viscous deformation considering the viscoplastic property of matrix polymer. More relaxed force could be obtained for the surface geometry farther from the flat surface and the surface geometries could be categorized into the surface with either equal height protuberances or random height ones. Laminate bond dominates the relaxed force and its lower viscosity could give relaxed force more. The viscosity of laminate bond could be more variable than matrix polymer and increase through the modification of structure by plastic and irreversible viscous deformation. The minimum elapsed time could be required to complete the relaxation behavior for the flat surface and the bond viscosity as high as matrix polymer.

FRP-Concrete Bond Behaviour under Cyclic Debonding Force

The strengthening of concrete structures against earthquake actions is one of the most important application of FRP; nevertheless, the effect of cyclic forces on FRP – concrete bonding has been scarcely experimentally investigated. This paper presents the results of an experimental campaign on FRP-concrete specimens subject to shear cycles at very high force levels, typical of earthquake excitation. Both CFRP plate and CFRP sheet have been tested. An experimental set-up (single shear test) allowing for stable debonding process has been adopted and both strain gauges along the FRP plate and LVDT transducers have been used. The sequences of the cyclic loadings under traction have been prescribed by controlling the progression of the debonding. It is shown that the debonding force is not affected by cyclic loadings; a small degradation of the interface behaviour, with the reduction of the maximum shear stress, has been detected only after the onset of debonding. Nevertheless, this reduction, analogous to that showed by monotonic loading tests, remains constant during the development of the debonding and is not modified by further application of cyclic loads at very high force level.

Quality Control and Monitoring of FRP Applications to Masonry Structures

Abstract: The use of composite materials in strengthening and restoring interventions on existing structures is continuously increasing. During the last decades, many researchers have developed new strategies, technical solutions and analyses. In particular, the Italian CNR DT 200/2004 technical recommendations for the design and construction of strengthening techniques with fibre‐reinforced composite material (FRP) systems have been published to provide an aid to designers interested in the field of composite materials and to avoid their incorrect application. The Guidelines deal with different types of FRP applications both to masonry and reinforced concrete structures and take into account several tests for the quality control and monitoring of FRP installation. In the present study, the results of semi‐destructive and non‐destructive techniques conducted for the quality control and monitoring of FRP applications to masonry, according to CNR DT 200/2004 Guidelines, are reported. Pull‐off tests and shear‐tearing tests were performed on real brick and natural stone masonry buildings for the assessment of the quality of FRP application. Finally, non‐destructive tests were carried out to characterise the uniformity of FRP installation by means of thermographic tests. Different types of FRP fabrics have been adopted. The tests allowed the validation and assessment of procedures, methods and theoretical relationships suggested in the Guidelines.