Use Of Composite Systems Research Articles

Influence of spike anchors in the bond behaviour of FRCM systems applied on concave masonry substrates

One of the methods that can be used for strengthening masonry arch structures is through the use of composite systems bonded to the external surfaces, preferably to the intrados, such as textile reinforced mortar systems (FRCM, TRM, SRG etc). The application of such systems to the intrados allows the ultimate load to be increased while keeping the structure in service. The load increment depends on the performance of the bond between the matrix and the masonry substrate and between the matrix and the fabric, and also the radial detachment stresses (normal for the strengthening system) that are generated when applying this technology to concave surfaces must also be taken into account, as they have a negative effect on the load transfer mechanism. Spike anchors are generally used to reduce the negative effect of curvature in order to postpone the debonding process of the strengthening system. This paper presents the results obtained from a direct shear test campaign on curved masonry specimens strengthened with a fiber-reinforced cement-based matrix (FRCM) with pozzolanic reaction and a carbon fiber fabric. In particular, the effects of spike anchors on the load transfer mechanism between FRCM and the masonry substrate are shown. The use of such spike anchors produced, on average, a higher maximum ultimate force than specimens without spike anchors.

The Specifics of Use of Composite Materials in Consolidation of Historical Monuments

Abstract The use of composite systems in protecting, preserving and maintaining historical monuments has become more and more used. There are several consolidation procedures with fiber-reinforced polymeric polymers that can be applied as required or on the basis of the basic material (concrete, masonry, wood, etc.). Besides the many advantages it provides, the application of composite systems in the rehabilitation of heritage buildings and historical monuments requires minimal workmanship. More and more cities are actively involved in the rehabilitation and preservation of heritage buildings and historical monuments by launching good practice guides to preserve local cultural heritage by applying composite elements as robust as possible without the need to modify the overall dimensions of the buildings through a classic covering.

12.06: Numerical analysis of stainless steel, concrete encased and carbon steel double skin tubular stub columns

ABSTRACTThe use of stainless steel as formwork for concrete columns provides several benefits for the structure, including the high corrosion resistance, durability, fire resistance, ease of maintenance and high aesthetic value. The use of composite systems in columns has been a major breakthrough in bridges and viaducts. A particular advantage of the composite columns is the reduction of cross sectional area, speed of construction, easy maintenance and material saving when compared to conventional reinforced concrete structures. These advantages are related to the idea that the columns are concrete filled eliminating the use of forms and the need for extra steel reinforcing bars. The investigated system adopts a second carbon steel tube inside the primary stainless steel tube composing the structural system made of concrete‐filled double skin composite tube columns (CFDSCT). This study aims to develop numerical models, using the finite element method and considering geometric imperfections. The structural behaviour was assessed through a nonlinear analysis and was later compared to compressive tests performed in the laboratory. After the completion of the numerical models calibration, a parametric analysis was performed to investigate the influence of parameters like the diameter, thickness and height of the stainless steel tube (outer) while its results were also compared to predictions made by traditional design equations.

Out-of-plane experimental behaviour of T-shaped full scale masonry wall strengthened with composite connections

Abstract The seismic behaviour of existing masonry buildings strongly depends on the type of connections between orthogonal walls and between walls and floors. Recent earthquakes have clearly shown that the most common failure modes of existing masonry buildings involve out-of-plane mechanisms. In these structures, the structural connections are crucial to achieve a favourable distribution of horizontal loads and to avoid out-of-plane mechanisms. In order to investigate on the effectiveness of typical existing structural connections between bearing walls in masonry buildings, an experimental program has been carried out on a full scale T-shape tuff masonry specimen. A weak connection has been designed between the two orthogonal walls of the specimen in order to reproduce common execution practices. Three tests have been performed under the simultaneous application of axial load and monotonic or cyclic horizontal displacements on the specimen in three different configurations: as-built, repaired, and repaired and strengthened with an innovative solution based on the use of composite systems. The strengthening solution consisted of grouted anchors made by hollow CFRP pultruded carbon tubes wrapped with longitudinal and spiral stainless steel fabrics to increase the bond between mortar and tubes. The paper reports the main aspects related to the experimental test setup, the theoretical predictions in terms of strength capacity, the main experimental results at global and local level, and the crack patterns and failure mechanisms of the as-built and strengthened specimen.

Impact of Shear Connector Spacing in Composite Construction Incorporating Cold-Formed Steel Channel Lipped Section

Composite construction with traditional Hot Rolled Steel (HRS) sections has been known to perform much better than with Cold-Formed Steel (CFS) sections for decades; as observed by extensive rules and requirements for their design as prescribed in current design codes. There is, however, limited technical information available about the use of composite systems that incorporates the use of light gauge steel sections, despite the potentials of the system in residential and light industrial constructions. However, the composite action of CFS with an in-situ concrete, especially Self-Compacting Concrete (SCC) using bolted shear connector has not yet established. Therefore, this study attempted to investigate the behaviour of bolted shear connector used with SCC and CFS to form a composite beam system at designated longitudinal spacing. Push-out and full-scale test specimens of longitudinal spacing of 250 mm and 300 mm with bolted shear connector of grade 8.8 installed with single nut and washer on the CFS flange and beneath it were fabricated, cast and tested till failure occurred. The experimental test results shows that the bolted shear connector possessed good ultimate strength and ultimate moment capacities with an increase in the longitudinal spacing of the bolted shear connector from 250 mm and to 300 mm respectively. It was therefore concluded that, longitudinal spacing between bolted shear connectors had significantly influenced the shear connector strength capacities.

STRENGTH CAPACITY OF BOLTED SHEAR CONNECTORS WITH COLD-FORMED STEEL SECTION INTEGRATED AS COMPOSITE BEAM IN SELF-COMPACTING CONCRETE

The use of composite systems comprising of concrete and hot-rolled steel (HRS) sections is well established as observed by extensive rules and requirements for their design as prescribed in current design codes. There is, however, few technical information available about the use of composite systems that incorporates the use of light gauge steel sections, despite the potentials of the system in residential and light industrial constructions. Therefore, this study investigates the strength capacity of bolted shear connectors with cold-formed steel (CFS) section integrated as composite beam in self-compacting concrete. In this paper, four composite beam specimens of dimensions (4500 mm x 1500 mm x 75 mm) with bolted shear connectors of M12 and M14 of grade 8.8 installed on the upper flanges of the coupled back-to-back CFS I-section with longitudinal spacing’s of 250 mm and 300 mm centers and spaced 75 mm laterally were fabricated, cast and tested to failure using four-point bending test. Shear connector size and the longitudinal spacing were the varied parameters, and their influence was investigated on the ultimate load and ultimate moment capacities. The results showed that, the ultimate load and ultimate moment capacities were both influenced remarkably by the studied parameters. However, results of theoretical analysis, revealed good agreement between the experimental and the theoretical results. This shows that, the plastic analysis results for the ultimate moment capacity of the composite beams can be estimated efficiently by using the constitutive laws as prescribed by Eurocodes.

Stress Intensity Factor for Repaired Circumferential Cracks in Pipe With Bonded Composite Wrap

The use of composite systems as a repair methodology in the pipeline industry has grown in recent years. In this study, the analysis of the behavior of circumferential through cracks in repaired pipe with bonded composite wrap subjected to internal pressure is performed using three-dimensional finite element analysis. The fracture criterion used in the analysis is the stress intensity factor (SIF). The obtained results show that the bonded composite repair reduces significantly the stress intensity factor at the tip of repaired cracks in the steel pipe, which can improve the residual lifespan of the pipe.

State-of-the-art techniques in operative dentistry: contemporary teaching of posterior composites in UK and Irish dental schools

Advances of composite systems and their application have revolutionised the management of posterior teeth affected by caries, facilitating a minimally invasive approach. Previous surveys have indicated that the teaching of posterior composites within dental schools was developing, albeit not keeping pace with clinical evidence and the development of increasingly predictable techniques and materials. Concurrently, surveys of dental practice indicate that dental amalgam still predominates as the 'material of choice' for the restoration of posterior teeth within UK general dental practice. In light of such considerations, the aim of this study was to investigate current teaching of posterior composites in Irish and UK dental schools. An online questionnaire which sought information in relation to the current teaching of posterior composites was developed and distributed to the 17 established Irish and UK dental schools with undergraduate teaching programmes in late 2009. Completed responses were received from all 17 schools (response rate = 100%). All 17 schools taught the placement of occlusal and two-surface occlusoproximal composites in premolar and permanent molar teeth. Two schools did not teach placement of three-surface occlusoproximal composites in either premolars or molars. In their preclinical courses, ten schools taught posterior composites before teaching dental amalgams. Fifty-five percent of posterior restorations placed by dental students were of composite (range = 10-90%) and 44% amalgam (range = 10-90%), indicating an increase of 180% in the numbers of posterior composites placed over the past five years. Diversity was noted in the teaching of clinical techniques and students at different schools are trained with different composites and bonding systems. Some cause for concern was noted in the teaching of certain techniques that were not in keeping with existing best evidence, such as the teaching of transparent matrix bands and light-transmitting wedges for occluso-proximal composites (eight schools) and the teaching of bevels on the cavosurface enamel margins of both the occlusal and proximal box margins (three schools). The teaching of posterior composites in the Irish and UK dental schools has substantially increased over the last five years. Dental students in these schools often gain more experience in the placement of posterior composites than amalgam. However, practice trends indicate that a majority of GDPs continue to place amalgam in preference to composite, thereby suggesting a source of tension as current dental students emerge into the dental workforce over the coming years. There is, as a consequence, a challenge to the dental profession and its funding agencies in the UK to encourage more of a shift towards the minimally interventive use of composite systems in the restoration of posterior teeth, in particular among established practitioners.

Viscose materials with soil-repellent properties

The possibility of fabricating viscose fibres with soil-repellent properties by modifying them with composites based on fluorine-containing copolymer latexes produced by domestic industry was investigated. It was shown that the use of composite systems based on fluorine-containing copolymers will allow obtaining viscose materials with a high level of soil-repellent properties, especially with respect to organic contaminants and water systems.

Observations on a composite resin for Class II restorations: Two-year report

A clinical study was conducted to compare the performance of a commercial composite direct-filling resin with that of amalgam in Class II cavities. Of 124 paired restorations placed in 73 patients, 92 pairs were available at the two-year period. The restorations were subsequently evaluated at one and two years by a team of examiners from the Materials and Technology Branch of the Division of Dental Health, United States Public Health Service, San Francisco. Caries was not detected with either material during the two year period. No gross fractures occurred in the composite resin restorations. Three amalgam restorations fractured during the first year, and one amalgam restoration was replaced at the time of the second examination because of suspected, although not confirmed, fracture. At the end of two years, a number of restorations of each material exhibited some degree of marginal breakdown. Amalgam restorations had little or no change in anatomic form, while a moderate change was observed in approximately one half of the composite resin restorations. The change in anatomic form appeared to be the result of occlusal wear. Until formulations are improved in this respect, the use of composite systems in Class II restorations should probably be limited to those situations where esthetics is the major consideration and the cavity preparations are conservative. Composite restorations were also evaluated with respect to color match and cavosurface marginal discoloration. A change in color match was observed in approximately 60 per cent of the composite resin restorations with time. However, the change appeared to be due to surface stain rather than color shift of the material. Slight marginal discoloration was detected in approximately 70 per cent of the composite restorations.