Flexural behaviour of structural fibre composite sandwich beams in flatwise and edgewise positions

The flexural behaviour of a new generation composite sandwich beams made up of glass fibre-reinforced polymer skins and modified phenolic core material was investigated. The composite sandwich beams were subjected to 4-point static bending test to determine their strength and failure mechanisms in the flatwise and the edgewise positions. The results of the experimental investigation showed that the composite sandwich beams tested in the edgewise position failed at a higher load with less deflection compared to specimens tested in the flatwise position. Under flexural loading, the composite sandwich beams in the edgewise position failed due to progressive failure of the skin while failure in the flatwise position is in a brittle manner due to either shear failure of the core or compressive failure of the skin followed by debonding between the skin and the core. The results of the analytical predictions and numerical simulations are in good agreement with the experimental results

Experimental investigation on the flexural behaviour of pultruded GFRP beams filled with different concrete strengths

Glass fibre reinforced polymer (GFRP) pultruded profiles are being increasingly used in the construction industry due to their numerous advantageous over the conventional materials. However, most pultruded GFRP sections fail prematurely without utilising their high tensile strength due to their thin-walled sections. As a result, several hybrid systems made out of GFRP profiles and concrete as a filler material have been proposed in order to enhance their structural performance. Most of these studies utilised high strength concrete wherein the additional cost does not justify the enhancement in the stiffness and strength of the infilled GFRP profiles. This paper presents an experimental investigation on the effect of the compressive strength of concrete infill on the flexural behaviour of beams with a view to determine a lower cost infill for GFRP profiles. Pultruded GFRP square beams (125 mm x125 mm x 6.5mm) were filled with concrete having 10, 37 and 43.5 MPa compressive strength and tested under static four-point bending. The results showed that the capacity of the filled beam sections increased by 100 to 141% than the hollow sections. However, the compressive strength of the concrete infill has no significant effect on the flexural behaviour of the beams. The increase in concrete compressive strength from 10 to 43.5 MPa increased the ultimate moment by only 19% but exhibited an almost same flexural stiffness indicating that a low strength concrete is a practical solution to fill the GFRP profile

POLARIS

The project explores the relationship between the architecture and the engineering behind thin-shelled concrete structures. Initially, hanging chain models were used to observe pure compression; then, this model was improved upon using software like Rhinocerus, AutoCAD. From AutoCAD, the model was imported into SAP2000 for analysis

Evaluation of physical and durability characteristics of new headed glass fiber–reinforced polymer bars for concrete structures

This paper presents the results of a collaborative research project with Quebec’s Ministry of Transportation and the Ontario’s Ministry of Transportation, which aimed at characterizing a new type of headed glass-fiber-reinforced-polymer (GFRP) reinforcing bar and evaluating its suitability as internal reinforcement for concrete structures. To achieve these objectives, the project was implemented in three stages: (1) evaluation of the physical and mechanical properties; (2) determination of the pullout behavior in concrete; and (3) characterization of the long-term durability of the headed GFRP bars. A total of 57 specimens embedded in a 200 mm concrete cube were tested with the direct pullout test to investigate the effect of confinement, bar size, concrete compressive strength, and exposure conditions on the pullout behavior of the headed GFRP bars. Simultaneously, microstructural analyses and measurements of the physicochemical and mechanical properties were carried out on conditioned and unconditioned headed GFRP bars. The results show that the materials, geometry, and interface configuration of the head provided very good mechanical interlocking to the GFRP bars. Up to 63% and 53% of the guaranteed tensile strength of the straight GFRP bars were achieved for 15.9 mm and 19 mm diameter bars with headed ends, respectively. Scanning electron microscopy and differential scanning calorimetry showed no material changes in the head and bars after exposure to alkaline solution and freeze–thaw cycling. Exposure to the alkaline solution under sustained loading had the most detrimental effect, with the bar retaining 79.4% of its pullout strength. The results indicate that the tested headed GFRP bar has suitable mechanical and durability properties for use as reinforcement in concrete bridge components

Compressive, tensile and thermal properties of epoxy grouts subjected to underwater conditioning at elevated temperature

Oil and gas pipes are susceptible to failure initiated by corrosion due to their operating pressure under adverse atmospheric conditions. Repairs, comprising a composite shell assembled around the pipe with a small gap, which is then infilled with grout, are considered a suitable option for corroded pipelines. This paper presents the investigation on the mechanical (compression, tension) properties and glass transition temperatures of two infill grouts, after 1000 hour of hot/wet conditioning. An extended investigation on the moisture absorption behaviour was also carried out, revealing the highest absorption to be about 6% after 2520 hours of immersion. The glass transition temperatures of the grouts are reduced by approximately 20ºC. The results suggest that the grouts underwent significant reduction of strength and stiffness due to hot/wet conditioning when tested at an elevated temperature, compared to room temperature. This reduced strength and stiffness is the result of the grouts being tested in close proximity to their glass transition temperatures

Oil contaminated sand: an emerging and sustainable construction material

Crude oil spillage severely impacts the environment and affects the physical and chemical properties of the surrounding soil. Due to prohibitive cost of cleaning and disposing oil contaminated sand, mixing and stabilizing them with cement and using them in construction is now considered as an alternative and cheap remediation method. In this paper, the effect of o il contamination on the mechanical properties of sand and its concrete were reviewed . In addition, the results of the on-going research and development on the effects of light crude oil contamination on the properties of fine sand and the produced mortar are presented. For fine sand contaminated with light crude oil, it was found that the cohesion increased significantly up to 1% of oil contamination and then decreased with increasing percentage of crude oil while a slight reduction in frictional angle was observed with oil contamination. The highest compressive strength was obtained for mortar with 1% oil contamination and with only a 18% decrease in strength of mortar with 10% oil contamination compared to the uncontaminated samples. More importantly, the compressive strength of mortar with oil contaminated sand was found suitable for some engineering applications indicating their high potential and beneficial use as an emerging and sustainable material in building and construction

Glass fibre and recycled mixed plastic wastes: recent developments and applications

In recent years, there has been an increasing interest in seeking for potential civil engineering applications of recycled mixed plastic wastes to relieve the pressure on landfills. This paper presents the recent developments on new generation of composites made from mixed recycled plastics and glass fibre. Glass fibres are one of the most cost-effective reinforcements which can be compounded with recycled thermoplastics to obtain products with improved mechanical property. Some of the first uses for such composites are for the replacement for traditional wooden items like park benches and picnic tables. While these composites are appropriate for such small-scale products, using them in structural applications would consume much greater volume of waste plastics. With its inherent resistance to rot and insect attack, these composites can in fact be used as a replacement for chemically treated timber in various large scale outdoor applications such as railroad crossties and bridges. However, the behaviour of such composites under different environmental conditions such as elevated temperature and ultraviolet rays are crucial. This paper provides an overview of the on-going efforts to address the critical issues for the effective usage of recycled mixed plastics composites in civil engineering and construction