The potential of membrane distillation (MD) in seawater desalination and high-salt wastewater treatment makes it a highly promising application in alleviating the global water crisis. However, membrane fouling and wetting are the main obstacles to the large-scale application of MD. Bio-inspired super liquid-repellent membranes offer a viable resolution to these challenges. The rapid advancement of nanotechnology has stimulated the growing attention toward electrospun nanofiber membranes (ENMs). Electrospun fibers demonstrate excellent functionalization, controllability, and hydrophobicity. Their low energy consumption and ease of preparation promote their application prospects in the construction of super liquid-repellent membranes. This article provides a comprehensive summary of electrospinning principles and influencing factors, coupled with a detailed account of the theory and preparation of super-liquid-repellent membranes via electrospinning, thus explicating the application and challenges of these membranes in MD, facilitating a deeper understanding of the ENMs application in MD for readers.
Four large scale concrete beams of 4.2 m length and 200 x 500 mm cross-section were built and tested under four-point bending. Two beams were used as control beams and were reinforced with mild steel for both shear and flexure. The flexural and shear reinforcement for the remaining two beams were provided by externally bonded carbon fibre (CFRP) sheet. In addition, to achieve ductility in the CFRP reinforced beams, a low modulus high strain high density polypropylene grid (HDPP) was placed within them. The primary focus of this study was to achieve ductility via the provision of HDPP but it was also intended to prevent delamination of bonded CFRP sheets by attaching some of the laminae to the sides of the beam rather than attaching them all to the beam soffit. Finally, the magnitude of shear that could be resisted by externally bonded CFRP U stirrups was investigated. The hybrid reinforced beams achieved their design capacity and initial failure occurred due to rupture of CFRP sheet in the maximum moment region, followed by some delamination. The CFRP stirrups reached 70% of their ultimate strain capacity. After the rupture of CFRP, the HDPP provided the beams with residual strength, but due to the low modulus of HDPP, the deformations of the beams increased substantially. (A) For the covering abstract see ITRD E104933.
Premature deterioration of concrete structures has created awareness and concern about the durability of concrete. Concrete mixtures used in the construction of residential basement walls and foundations have a high water to cement (w/c) ratio (w/c>0.6) and low cement content (<280kg/m3). The result is friable concrete with a highly porous surface layer and high potential for cracking. The defects have a direct impact on the durability of concrete. This experimental study examines the effects of three parameters—mix design, formwork, and consolidation—on the quality of the surface of high w/c concrete. The fresh concrete is characterized using its rheological properties—in particular, its yield stress and plastic viscosity. Pulse velocity, pull-off strength, and compressive strength were measured to evaluate the quality and the mechanical properties of the hardened concrete. The durability of the hardened concrete was evaluated by measuring its surface transport properties—namely, its air permeability and sorptivity. The results show that it is possible to correlate the rheological properties of fresh concrete to the mechanical and permeation properties of the hardened concrete.
An experimental investigation was carried out to evaluate the seismic behaviour of 200 × 200 mm2 reinforced-concrete columns with an embedded drain pipe subjected to monotonic and reversed cyclic loading. Nine full-scale specimens were prepared, including two control specimens without an embedded pipe and seven specimens with a pipe embedded in the column core. Among the latter seven columns, two were highly confined using 8 mm dia. ties with 80 mm spacing, while a 200 mm spacing was used in the other columns. The test results indicated that the pipe adversely affected the column's load-carrying capacity, load–displacement response and ductility. The extent of the adverse effect was found to depend on the level of axial load, the degree of confinement and the distance of the pipe exit from the column base. Due to local stress concentration, some local damage was observed in the vicinity of the pipe exit, but the provision of high confinement in the pipe exit region significantly improved the overall behaviour of the column under reversed cyclic loading.
Vlasov's thin walled box beam theory, which accounts for the distortion of the cross section, is combined with special shear lag warping functions to derive a box girder finite elenent model with exact shape functions. The governing differential equations are used to derive the exact shape functions and the stiffness matrix and nodal load vector are developed based on these. The paper describes the computer program in which the proposed procedures are implemented, and two numerical examples are presented which compare the proposed method with facet shell finite element analyses.
