Flexural Behaviour of Composite High Strength Concrete – Fibre Reinforced Polymer Beams
This paper presents the results of an experimental study conducted to examine the effectiveness of Glass Fibre Reinforced Polymer (GFRP) laminates in enhancing the flexural capacity of high strength concrete beams. In this study, a total of ten beams of size 150 mm x 250 mm in crosssection with a total length of 3000 mm were cast and tested. Eight beams were strengthened with chopped strand mat glass fibre reinforced polymer and uni-directional cloth glass fibre reinforced polymer of 3mm and 5mm thickness. The study parameters included the reinforcement ratio, GFRP laminate material and their thickness. All the beam specimens were subjected to four-point bending test in a loading frame. Deflection and strain measurements have been made through appropriate instrumentation. The results show that the GFRP strengthened beams exhibit increased strength, flexural stiffness and composite action until failure. Keywords— GFRP, HSC beams, laminates, strengthened
Design Guidelines for Flexural Strengthening of RC Beams with FRP Plates
Bonding composite plates to reinforced concrete beams is an effective technique of repair and retrofit. The ultimate capacity of the strengthened beam is controlled by either compression crushing of concrete, rupture of the plate, local failure of concrete at the plate end due to stress concentration, or debonding of the plate. These failure modes have been considered for developing design guidelines for strengthening reinforced concrete beams using fiber composite plates. The effect of multistep loading of the beam, before and after upgrading, has been included in these guidelines. Limit state design concept has been followed in this paper. Terms, definitions, and notations compatible to design guidelines for ordinary reinforced concrete beams have been used.
Mitochondrial aquaporin-8-mediated hydrogen peroxide transport is essential for teleost spermatozoon motility
Reactive oxygen species (ROS), particularly hydrogen peroxide (H2O2), cause oxidative cell damage and inhibit sperm function. In most oviparous fishes that spawn in seawater (SW), spermatozoa may be exposed to harmful ROS loads associated with the hyperosmotic stress of axonemal activation and ATP synthesis from mitochondrial oxidative phosphorylation. However, it is not known how marine spermatozoa can cope with the increased ROS levels to maintain flagellar motility. Here, we show that a marine teleost orthologue of human aquaporin-8, termed Aqp8b, is rapidly phosphorylated and inserted into the inner mitochondrial membrane of SW-activated spermatozoa, where it facilitates H2O2 efflux from this compartment. When Aqp8b intracellular trafficking and mitochondrial channel activity are immunologically blocked in activated spermatozoa, ROS levels accumulate in the mitochondria leading to mitochondrial membrane depolarisation, the reduction of ATP production, and the progressive arrest of sperm motility. However, the decreased sperm vitality underlying Aqp8b loss of function is fully reversed in the presence of a mitochondria-targeted antioxidant. These findings reveal a previously unknown detoxification mechanism in spermatozoa under hypertonic conditions, whereby mitochondrial Aqp8b-mediated H2O2 efflux permits fuel production and the maintenance of flagellar motility.