Cytotoxic activity of the Red Sea anemone entacmaea quadricolor on liver cancer cells

Entacmaea quadricolor (Phylum Cnidaria, class Anthozoa) is a marine anemone found in Coral Reefs in the Red Sea. Its venom is reported to be a potential anticancer agent when tested on several cancer cell lines; such as skin cancer, and lung cancer cell lines. Yet, none of the earlier studies have characterized the extracted venom, nor tested its activity on hepatocellular carcinoma (HCC). The purpose of this study was to determine for the first time the potential cytotoxic activity of the Red Sea anemone E. quadricolor on HCC cell line. In addition to the effects of bleaching, seasonality and light exposure during storage on the venom were studied. Moreover, it was aimed to determine whether the cytotoxic activity was apoptotic or necrotic. In this study, the venom of the anemone E. quadricolor was extracted and stored under three different conditions; winter vs. summer, light vs. dark and bleached vs. unbleached. The cytotoxic activity of each venom was tested on SNU-449 HCC cells using the MTT assay. SDS-PAGE was used to differentiate between venoms based on protein composition. Moreover, Annexin-V/PI assay was used to determine the type of cytotoxic activity. The results revealed that E. quadricolor had potent cytotoxic activity against SNU-449 cells that was mediated by a necrotic pathway. The maximum activity was found during summer at the half-inhibitory concentration (IC50) of 20 µg/ ml. However, this cytotoxic activity was neutralized when the venom had been exposed to light when stored. Furthermore, cytotoxic activity was significantly decreased upon Bleaching of the anemone. A protein of 28 kDa was found in the composition of the venoms of bleached and unbleached organisms possibly identifying the cytotoxic active protein. The present results underline the findings of previous studies showing the cytotoxic activity of the sea anemone venom on cancer cell lines extending this to HCC. Furthermore, the findings are unique in showing that a bleached organism still produces toxic proteins and the venom loses its toxicity when exposed to light

STR-837: PUNCHING SHEAR BEHAVIOUR OF HIGH STRENGTH CONCRETE SLAB-COLUMN CONNECTIONS REINFORCED WITH GFRP BARS

The catastrophic nature of punching shear failure exhibited by flat plate system requires a great attention and robust predictions of the behaviour of slab-column connections. This paper presents an experimental study carried out to investigate the punching shear behaviour of fibre-reinforced polymer (FRP) reinforced concrete (RC) interior slab-column connections made of high strength concrete (HSC). Three full-scale HSC specimens were constructed and tested up to failure. The three connections were reinforced with GFRP sand-coated bars with reinforcement ratios of 1.0, 1.5 and 2.0% without any shear reinforcement. The typical dimensions of the test specimens were 2800 × 2800 × 200 mm with a 300 mm square column extending 1000 mm above and below the slab, representing the region of negative bending moment around an interior supporting column of a parking structure. All specimens were simply-supported along all four edges with the corners free to lift. The connections were subjected to vertical load and unbalanced moment that were monotonically applied through the column tips. The behaviour of the specimens in terms of the deformation and strength characteristics is discussed. Increasing the reinforcement ratio increased the punching shear capacity and decreased the reinforcement strains and deflections at the same load level. The test results were also compared to the predictions of the relevant North American codes where applicable

STR-886: EFFECT OF CONCRETE STRENGTH ON THE PUNCHING SHEAR BEHAVIOUR OF GFRP-RC SLAB-COLUMN EDGE CONNECTIONS

This paper presents the results of an experimental program carried out to investigate the effect of concrete strength on the punching shear behaviour of concrete slab-column edge connections reinforced with glass fibre-reinforced polymer (GFRP) bars. Six full-scale connections were constructed and tested to failure under gravity loads. Three connections were made of normal strength concrete (NSC), while the other three were made of high strength concrete (HSC). The dimensions of the slabs were 2,800×1,550×200 mm with a 300-mm square column extending 1,000 mm above and below the slab. All connections were reinforced with GFRP sand-coated bars without shear reinforcement. Three flexural reinforcement ratios were employed for each concrete strength; 0.90, 1.35 and 1.80% in the direction perpendicular to the free edge. All connections failed in a brittle punching mode. The HSC connections showed less deflections and strains in both reinforcement and concrete at the same load level than their NSC counterparts. Also, doubling the concrete strength (from 40 to 80 MPa) slightly increased the capacity by 10, 3 and 5% for connections with reinforcement ratios of 0.90, 1.35 and 1.80%, respectively. Moreover, the Canadian standard for FRP-reinforced concrete buildings provided reasonable predictions with an average experimental-to-predicted ratio of 1.29±0.05 and 1.22±0.05 for the NSC and HSC connections, respectively

STR-884: EFFECT OF SPACING OF TRANSVERSE REINFORCEMENT ON THE LAPPED SPLICED GFRP‐RC COLUMNS SUBJECTED TO CYCLIC‐REVERSED LOADS

Recently, the non-corrodible fibre-reinforced polymer (FRP) materials have been used successfully as reinforcement for concrete structures. However, the behaviour of glass (G) FRP-reinforced concrete (RC) columns under seismic loading has not been explored yet. This paper presents the results of an experimental program that investigates the contribution of GFRP transverse reinforcement to the confinement of concrete core in lap-spliced GFRP-RC columns. Three full-scale column specimens were constructed and tested to failure under quasi-static cyclic‐reversed loads. All specimens were reinforced with GFRP longitudinal bars and transverse stirrups. The columns had 350-mm square cross section and 1850-mm cantilever length. Each column was cast on heavily steel-RC footing measuring 1400×1400× 600 mm3, which was constructed to simulate rotational fixity of the column and to force the failure to occur in the column. The splice length for each column was equal to sixty times the diameter of the longitudinal column reinforcement. The test variable was the spacing between the transverse GFRP reinforcement (75, 100 and 150 mm). Test results are presented in terms of mode of failure, load-drift diagrams, energy dissipation, ultimate capacity and code comparison, if applicable. The results showed that, decreasing the spacing of spiral reinforcement improved both the strength and the deformability of the columns. Moreover, the requirement of the Canadian standard for FRP-RC buildings related to the amount of confinement provided by GFRP transverse reinforcement is adequate to ensure stability of the longitudinal bars

STR-895: MOMENT REDISTRIBUTION OF GFRP-RC CONTINUOUS T-BEAMS

Fiber-reinforced polymer (FRP) bars have proven to be an excellent alternative to steel bars in many concrete structures such as parking garages and overpasses that are susceptible to harsh environments and consequently corrosion of steel reinforcement. In these structures, FRP reinforced concrete (FRP-RC) continuous beams are common members. Moment redistribution in FRP-RC continuous beams has not been well established yet because of the different characteristics of FRP bars such as linear-elastic stress-strain relationship and lower modulus of elasticity compared to conventional steel. Recent studies showed that redistribution of internal forces in Glass (G) FRP-RC continuous beams with a rectangular section is possible. However, no attention was given to continuous beams with a T-section. Therefore, this study aims at investigating the ability of GFRP-RC continuous beams with a T-section to redistribute the moment between the critical sections. In this paper, test results of three large-scale GFRP-RC T-beams are presented. The beams were 6,000-mm long and continuous over two equal spans of 2,800 mm each. The sections had an overall depth of 300 mm, an effective flange width of 600 mm, a flange thickness of 100 mm, and a web width of 200 mm. The test variables included the assumed moment redistribution percentage and the arrangement of shear reinforcement. It was observed that the beam with less stirrup spacing showed better performance in achieving the assumed percentage of moment redistribution and in carrying higher ultimate load compared to its counterparts with larger stirrup spacing

Post-Cracking Behavior of Cementitious Composite Incorporating Nano-Silica and Basalt Fiber Pellets

Recently, fiber reinforced polymers (FRPs) have been increasingly used to reinforce concrete structures in harsh environments, due to their non-corrodible nature. Developing a nonferrous reinforcement system (corrosion-free system) for concrete using FRP bars along with discrete fibers is a promising option for exposed concrete structures in cold regions or marine environments. Incorporating highly efficient non-metallic fibers into any cementitious composite is capable of reducing bleeding, controlling shrinkage cracking, and improving toughness and impact resistance. Therefore, in this study, a new type of basalt fiber pellets with high tensile strength was investigated. This paper reports on the flexural performance of the basalt fiber-reinforced cementitious composite (BFRCC) compared to steel fiber-reinforced cementitious composite (SFRCC). The cementitious composite incorporated general use cement, slag and nano-silica. The key mechanical property determined was the post-cracking behavior in terms of residual strength, and toughness. Standard prisms (100 × 100 × 350 mm) were cast using basalt fiber pellets and steel fibers with three different dosages and tested after 28 days following the general guidelines of ASTM C1609 (Standard Test Method for Flexural Performance of Fiber-Reinforced Concrete). Analysis of results showed a high level of effectiveness of the basalt fibers to enhance the post-cracking behavior of specimens, as they behaved comparably or superiorly (first cracking, load-deflection relationship, and toughness) to counterpart specimens comprising steel fibers

Finite Element Modeling of GFRP-Reinforced Concrete Interior Slab-Column Connections Subjected to Moment Transfer

A finite element model (FEM) was constructed using specialized three-dimensional (3D) software to investigate the punching shear behavior of interior slab-column connections subjected to a moment-to-shear ratio of 0.15 m. The FEM was then verified against the experimental results of full-scale interior slab-column connections reinforced with glass fiber reinforcement polymer (GFRP) bars previously tested by the authors. The FEM results showed that the constructed model was able to predict the behavior of the slabs with reasonable accuracy. Afterward, the verified model was used to conduct a parametric study to investigate the effects of reinforcement ratio, perimeter-to-depth ratio, and column aspect ratio on the punching shear behavior of such connections. The test results showed that increasing the tested parameters enhanced the overall behavior of the connections in terms of decreasing deflections and reinforcement strain and increasing the ultimate capacity. In addition, the obtained punching shear stresses of the connections were compared to the predictions of the Canadian standard and the American guideline for FRP-reinforced concrete structures

Seismic performance improvement of GFRP-RC moment frames

Although concrete structures reinforced with Fiber Reinforced Polymers (FRPs) have shown promising performance under gravity loads, their performance under cyclic loading is still a concern. Although the linear nature of FRP reinforcement could be advantageous in terms of limiting the residual damage after an earthquake event, it lowers the energy dissipation of the structure which can compromise its seismic performance. In this research, adding steel plates at selected locations in moment-resisting frames is proposed as a solution to improve seismic performance of FRP-RC structures. Three full-scale cantilever beams, one steel-RC, one FRP-RC and one FRP-RC with proposed steel plates were constructed and tested under reversal-cyclic loading. The results indicated that the proposed mechanism effectively improves the seismic performance of FRP-RC beams through increasing their initial stiffness and energy dissipation. Moreover, a computer simulation, using moment-curvature determination process, was conducted to calculate bending moment capacity of FRP-RC beams with steel plates.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Finite-Element Analysis of Adjacent Concrete Box Girders Transversely Post-Tensioned at the Top Flanges Only

A three-dimensional non-linear finite-element model (FEM) was constructed using a commercial software (ATENA-Studio) to investigate the transverse load distribution behavior of adjacent precast prestressed concrete box-girder bridges. An innovative connection between box girders was used, where transverse post-tensioning was applied at the top flanges only eliminating the need for intermediate transverse diaphragms. The FEM was validated in terms of deflections, strains, cracking and ultimate loads against experimental results previously reported by the authors. The validated FEM was then used to perform a parametric study investigating the influence of adding concrete topping, load location, and bridge width on the transverse load distribution behavior of the newly developed connection. The results of the FEM demonstrated the efficiency of concrete topping in limiting mid-span deflections up to 25%. Additionally, the maximum live load moment distribution factors (LLMDFs) for different load locations and bridge widths were evaluated