Evaluation of grooving method to postpone debonding of FRP laminates in WPC-FRP beams

The use of lightweight construction material with high corrosion resistance and low cost plays an important role in the design and construction of marine structures such as waterfronts. One of the most common methods for strengthening the structures is composite fibre reinforced plastic (FRP) sheet that is used for member retrofitting including wood plastic composite (WPC). The WPC material is produced from wood and compressed resin, which has good mechanical properties as well as economic benefits. The main problem of WPC reinforced with FRP sheets is the debonding of the sheet from WPC surface, which leads to premature and non-economic failure in members. One of the existing methods to solve this problem is surface preparation. However, surface preparation of wood plastic composite has some additional problems, such as operational cost, environmental pollution, etc. Therefore, to avoid debonding, another method has been used, known as the grooving method at the lower parts of beams. The laboratory used 50 I-shaped specimens with the same geometrical and mechanical properties. Initially, some slots such as longitudinal, transverse and diagonal grooves were created on the surface of specimens and filled by an epoxy. All beams were armed using one or two layers of GFRP sheets embedded at the lower part and were tested under four-point flexural loading. Grooves of different shapes, various widths and depths as well as the number of reinforcement layers were determined for considering their effect on the beam's behaviour. The results expressed that the debonding of FRP sheets can be delayed by selecting the longitudinal grooves with certain width and depth, which also leads to resistance improvement

Investigating laboratory parameters of the resistance of different mixtures of soil – lime – fume using the curing and administrative method

Soils treatment is affected by various factors such as density, moisture content and mineral composition of soil and different percentages of materials in soil. Lime soil as a suitable and inexpensive material has been used for decades to stabilize in civil engineering projects; however, the effect of adding fume and curing temperature on strength and stability parameters of the mixture seldom been studied. In this study, soil and water has been studied from Dokhtar Borji in Hosseinieh city in Iran. Based on a laboratory study, we dealt with evaluating the physical and mechanical properties of soils and chemical properties of soil and water. The cylindrical samples of different mixtures of soil- lime- fume were modified using the AASHTO method and compressive strength testing of 7-, 14- and 28-day samples were conducted according to ASTM standards at 27 °C. Analysis was conducted in SAS (Statistical Analysis System) software. Results indicated that the increase in average compressive strength from 7 to 14 and from 14 to 28 days were 62 and 53.57%, respectively. Therefore, by increasing the number of curing days from 7 to 14, the percentage of the compressive strength is at its highest. The study also provided a linear regression equation that determines compressive strength with an accuracy of 95.1%