Strengthening Of Slabs Research Articles

Evaluation of CFRP, GFRP and BFRP Material Systems for the Strengthening of RC Slabs

An experiment was carried out to investigate the effect of CFRP, GFRP and BFRP materials on the strengthening of reinforced concrete slabs. RC slab specimens were tested on a steel frame with four supporting edges. They were centrally loaded with the actuator of an MTS through a steel plate. The strengthening capacity and the failure mode of slabs strengthened with different material systems were determined and compared. A finite element model (using ANSYS program) was used for predicting the failure process of slabs strengthened with different material systems. The predicted and experimental results are in good agreement.

Strengthening of Interior Slab–Column Connections Using a Combination of FRP Sheets and Steel Bolts

The results of an experimental investigation undertaken to evaluate a new technique for strengthening interior slab–column connection in combined flexural and shear modes are presented. The technique consists of using a combination of shear bolts inserted into holes and prestressed against the concrete surface for improving the punching shear capacity, and external [fiber-reinforced polymer (FRP)] reinforcement bonded to the tension face of the slabs in two perpendicular directions for increasing the flexural strength of the slabs. Square slab specimens of 670×670 mm dimensions were tested and the main test variables included the ratio of steel reinforcement (1.0 and 1.5%), span–depth ratio or thickness (55 and 75 mm ) of the slabs, area, and configuration of steel bolts, and area of FRP reinforcement. It was found that the use of shear bolts alone improves the punching shear strength and increases the ductility of failure by changing the failure mode from punching to flexural. However, the use of a combi...

CFRP strengthened openings in two-way concrete slabs – An experimental and numerical study

Rehabilitation and strengthening of concrete structures with externally bonded fibre reinforced polymers (FRPs) has been a viable technique for at least a decade. An interesting and useful application is strengthening of slabs or walls where openings are introduced. In these situations, FRP sheets are very suitable; not only because of their strength, but also due to that they are easy to apply in comparison to traditional steel girders or other lintel systems. Even though many benefits have been shown by strengthening openings with FRPs not much research have been presented in the literature. In this paper, laboratory tests on 11 slabs with openings, loaded with a distributed load are presented together with analytical and numerical evaluations. Six slabs with openings have been strengthened with carbon fibre reinforced polymers (CFRPs) sheets. These slabs are compared with traditionally steel reinforced slabs, both with (four slabs) and without openings (one slab). The slabs are quadratic with a side length of 2.6 m and a thickness of 100 mm. Two different sizes of openings are used, 0.85 × 0.85 m and 1.2 × 1.2 m. The results from the tests show that slabs with openings can be strengthened with externally bonded CFRP sheets. The performance is even better than for traditionally steel reinforced slabs. The numerical and analytical evaluations show good agreement with the experimental results.

Effect of material configuration on strengthening of concrete slabs by CFRP composites

While there have been a large number of studies related to strengthening of concrete beams, girders and slabs through the use of externally bonded fiber reinforced polymer (FRP) composites, there has been very little emphasis on investigating the effect of material configuration (primarily related to the process used to fabricate the strips). This paper reports on the strength, failure mechanisms and ductility achieved through the use of pultrusion and wet layup fabricated strips, both adhesively bonded to the concrete substrate. Fourteen different tests are conducted on concrete slabs using a variety of configurations. Differences in mechanisms of failure are identified and comparisons are made of overall response. Initial results of materials efficiency are noted and results are compared to an analytical model with criteria based on fracture based criteria.

Carbon FRP Grid로 휨 보강한 철근콘크리트 슬래브의 파괴형태와 설계기준

This paper presents the failure mode and strengthening design of reinforced concrete slab strengthened with Carbon Fiber Reinforced Polymer(CFRP) grid. Parameters involved in this experimental study are FRP grid reinforcement quantity, repair mortar thickness, the presence of anchor, and strengthening in compression. In this study, there are different failure types with increasing the CFRP grid strengthening reinforcement. On the low strengthening level, CFRP grid in repair mortar cover ruptures. On the moderate strengthening level, there is a debonding shear failure in the interface of carbon FRP grid because of the excessive shear deformation. On the high strengthening level, diagonal shear failure occurs. With the increasing of FRP grid reinforcement, the strengthening effect increased, but the ductility decreased. By limiting the strengthening level, it can be achieved to prevent shear failure which result in sudden loss in the resisting load capacity. CFRP rupture failure is desirable, because CFRP ruptured concrete slab keeps the same load capacity and ductility haying before strengthening even after failure. Finally, design guideline and procedure are given for strengthening of concrete slab with CFRP grid.

The refurbishment of Heyeswood Railway Bridge

Heyeswood Railway Bridge was constructed in 1958 and carries the A556 dual carriageway over an over-head electrified spur of the West Coast Mainline railway. The 45° skew deck comprises fabricated steel girders with reinforced concrete slabs at the top and bottom of the deck, forming a complete enclosure. The bridge had suffered deterioration as a result of a variety of factors resulting in significant spalling to both slabs. Interim strengthening was carried out in 1991. Major utilities were very restrictive. The most cost-effective long-term solution was to over slab the top slab, nominally repair the bottom slab and provide a unique load-carrying, glass-reinforced plastic enclosure to the soffit. This aspect of the design is emphasised. The top slab strengthening was carried out in two phases, enabling a contra-flow traffic system to be in place throughout. Work to the soffit had to be carried out under a series of Saturday night railway possessions. The project was carried out as part of the Highways Agency's innovative Construction Management Pilot. It is unlikely that this project could have been successfully concluded under a traditional, more adversarial contract.

The refurbishment of Heyeswood Railway Bridge

Heyeswood Railway Bridge was constructed in 1958 and carries the A556 dual carriageway over an over-head electrified spur of the West Coast Mainline railway. The 45° skew deck comprises fabricated steel girders with reinforced concrete slabs at the top and bottom of the deck, forming a complete enclosure. The bridge had suffered deterioration as a result of a variety of factors resulting in significant spalling to both slabs. Interim strengthening was carried out in 1991. Major utilities were very restrictive. The most cost-effective long-term solution was to over slab the top slab, nominally repair the bottom slab and provide a unique load-carrying, glass-reinforced plastic enclosure to the soffit. This aspect of the design is emphasised. The top slab strengthening was carried out in two phases, enabling a contra-flow traffic system to be in place throughout. Work to the soffit had to be carried out under a series of Saturday night railway possessions. The project was carried out as part of the Highways Agency's innovative Construction Management Pilot. It is unlikely that this project could have been successfully concluded under a traditional, more adversarial contract.

Assessment of Dielectrometry for Characterization of Processing and Moisture Absorption in FRP Composites

The increasing use of ambient cured resin systems for the fabrication of composites used in structural components such as in civil infrastructure creates a need for monitoring cure progression over time as well as for tracking changes due to environmental exposure during the extended period of time needed to attain full cure. Further, there is a need for the development of methods to monitor the health of structures in the field for applications such as column retrofit, external strengthening of girders and slabs, and even bridge decks. This paper investigates the application of dielectrometry to the characterization of E-glass epoxy composites exposed to deionized water. Results are correlated with DSC and moisture absorption. It is shown that a direct correlation between moisture absorption and permittivity can be obtained.

Fiber-Reinforced Polymer Strengthening of Two-Way Slabs

First Name is required invalid characters Last Name is required invalid characters Email Address is required Invalid Email Address Invalid Email Address

Behaviour and strength of FRP-strengthened RC structures: a state-of-the-art review

Extensive research has been carried out in recent years on the use of fibre-reinforced polymer (FRP) composites in the strengthening of reinforced concrete (RC) structures. This paper provides a concise review of existing research on the behaviour and strength of FRP-strengthened RC structures, with a strong focus on those studies which contribute directly to the development of strength models. Topics covered include flexural and shear strengthening of beams, flexural strengthening of slabs, and strengthening of columns subject to both static and seismic loads. For each of the topics covered, the methods of strengthening are first explained, followed by a description of the common failure modes. Available strength models are then summarised and discussed.

Fiber-Reinforced Polymer Composite Strengthening of Concrete Slabs with Cutouts

Fiber-Reinforced Polymer Composite Strengthening of Concrete Slabs with Cutouts

Strengthening of two-way concrete slabs with FRP composite laminates

This paper presents an experimental and analytical investigation for evaluating the ultimate response of unreinforced and reinforced concrete slabs repaired and retrofitted with fiber reinforced polymer (FRP) composite strips. A uniformly distributed pressure was applied to several two-way large-scale slab specimens using a high-pressure water bag. Both carbon/epoxy and E-glass/epoxy composite systems were used in this study. In predicting the behavior of the repaired slabs, the finite element method was used. Comparison between the experimental and the analytical results indicated the validity of the computational models in capturing the experimentally determined results for both the control and the rehabilitated slabs. For repair applications, test results indicated that both FRP systems were effective in appreciably increasing the strength of the repaired slabs to approximately five times that of the as-built slabs. For retrofitting applications, use of FRP systems resulted in appreciable upgrade of the structural capacity of the as-built slabs up to 500% for unreinforced specimens and 200% for steel reinforced specimens.

TR 55: Design guidance for stengthening concrete structures using fibre composite materials: a review

This paper reviews the contents of Concrete Society Technical Report 55 on strengthening concrete structures using externally bonded fibre composite materials. The paper describes the background, nature and mechanics of producing the Report. Set in the context of limit state philosophy, the Report provides design guidance on flexural strengthening of beams and slabs, shear strengthening of beams and columns, and flexural and compressive strengthening of columns. These procedures are briefly explained. Other aspects of the Report, which deal with material types and properties, field applications, workmanship and installation, and long-term monitoring, are summarised. Finally, a worked example of a beam strengthened with bonded FRP reinforcement is presented in order to illustrate the design procedure for flexural strengthening, this representing the majority of applications.

Strengthening of Two-Way Slabs Using Steel Plates

First Name is required invalid characters Last Name is required invalid characters Email Address is required Invalid Email Address Invalid Email Address

Strengthening of Two-Way Slabs Subjected to Moment and Cyclic Loading

Strengthening of Two-Way Slabs Subjected to Moment and Cyclic Loading

Strengthening of RC slabs with circular composite patches – a high-order approach

A new approach for the strengthening of existing reinforced concrete slabs using circular patches made of composite materials, and a mathematical model for the analysis of such strengthened slabs are presented. The model follows the concepts of the High-Order theory and fulfills all equilibrium and compatibility requirements as well as boundary and continuity conditions. The field equations and the boundary and continuity conditions are derived via the variational principle of virtual work assuming axisymmetric behavior. The constitutive relations of laminated materials are used for the composite patch and unique constitutive relations are derived for the RC member. The proposed model is used for the investigation of a square slab strengthened with circular patches of various materials and sizes through a sub-structuring approach. The results include the overall behavior of the strengthened slab and the localized shear and vertical normal stresses near the edges of the bonded patch throughout the entire loading process. The effects involved with pretensioning of the circular patch are also examined. The study reveals that the proposed strengthening approach improves both the serviceability and the load resistance of the slab, however it is associated with severe stress concentrations near the edge of the bonded patch.

Strength of RC Cantilever Slabs Bonded with GFRP Strips

Strengthening of RC cantilever slabs using bonded glass-fiber–reinforced plastic (GFRP) strips has recently been explored. That work led to the proposal that the GFRP strips should be anchored to the supporting wall using epoxy-mortar–filled horizontal slots and to the slab using fiber anchors, to prevent or limit debonding. This paper focuses on the strength of RC cantilever slabs strengthened using this method. Experimental work on model cantilever slabs with steel reinforcement of different amounts and different positions is presented. Because of the presence of fiber anchors, all strengthened slabs failed by tensile rupture of the fiber-reinforced plastic (FRP), although in some of the slabs partial debonding had appeared before the FRP rupture took place. Flexural strength equations based on the conventional plane section assumption are next described and shown to predict the test results well, even for slabs with partially debonded FRP strips. Finally, the effect of preloading on the strength of strengthened slabs is discussed.

Materials Considerations in FRP Rehabilitation of Concrete Structures

The use of fiber reinforced polymer (FRP) composites for the seismic retrofit of columns and piers, flexural strengthening of beams and girders, and strengthening of slabs has been fairly well established on a structural basis. However, aspects related to materials selection and use, design detailing, fracture and failure mechanisms, and durability are still not well understood. The functional efficiency of the rehabilitated structure is largely dependent on materials-related issues, which are highlighted in this paper, emphasizing effects pertaining to constituent materials, interfaces, and overall systems response. Major implications of processing and fabrication schemes are highlighted focusing on materials use efficiency, potential of defect formation, and effects on durability. Examples of the importance of detailing are shown, and design guidelines pertaining to materials are discussed.

Retrofitting of Deficient RC Cantilever Slabs Using GFRP Strips

Despite many studies on beams and slabs strengthened using fiber-reinforced plastic (FRP) plates, no study has been reported on the strengthening of RC cantilever slabs (e.g., canopies and balconies) using FRP materials. This paper presents the results of an experimental study of the feasibility of strengthening deficient RC cantilever slabs by bonding glass FRP (GFRP) strips/sheets on the top surface (the tension side). As the key to the success of this strengthening method is a proper way of anchoring the GFRP strips into the supporting wall and the slab, the effectiveness of different anchorage systems was the focus of the experiments. Based on the test results, a simple and effective method is identified in which the GFRP strips are anchored into the walls through horizontal slots and onto the slab using fiber anchors.

Fiber Reinforced Composites – Advanced Materials for the Renewal of Civil Infrastructure

Fiber reinforced polymer matrix composite materials hitherto used predominantly in aerospace and marine applications are increasingly being considered for use in the renewal of civil infrastructure ranging from the seismic retrofit of bridge columns and the strengthening of parking garage floor slabs to their use in replacement bridge decks and in new bridge structures. Their corrosion resistance, potentially high overall durability, light weight, tailorability and high specific performance attributes enable their use in areas in which the use of conventional materials might be constrained due to durability, weight or lack of design flexibility. This paper provides an overview of the use of composites in the renewal of civil structures with particular emphasis on bridges and pipelines. Examples of large scale testing for the validation of structural effectiveness are given and future design and research advances are presented.