Design and multi-physical properties of a new hybrid hemp-flax composite material

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Influence of the type of viscosity-modifying admixtures and metakaolin on the rheology of grouts

The Viscosity-modifying admixtures (VMAs) contribute to the control of the rheology of grouts and are used to enhance plastic viscosity, cohesion, stability, and resistance to bleeding of cement-based systems.  This paper reports the results of an investigation on the effect of type of VMAs, namely two types of diutan gums and a welan gum and metakaolin (MTK), plus a superplasticiser, on the rheology behaviour of cement grouts.  All mixes were made with polycarboxylic superplasticiser at 0.6% and 0.9%.  The dosages of VMAs were 0.05%, and 0.10%, with a fixed water-to-binder ratio of 0.40.  The investigated fresh properties of the grouts included the mini-slump flow, plate cohesion, and rheology parameters: namely yield value and plastic viscosity.  The rheological parameters were obtained using a vane viscometer.  Control grouts (with and without superplasticiser and VMA) were also tested and compared to mixes containing VMAs.  The results indicated that the incorporation of MTK reduced the fluidity and increased the plate cohesion and yield stress, and plastic viscosity due to the higher surface area of MTK.  The diutan gum grouts improved the grout fresh properties and rheology compared to the welan gum grouts

The effect of semi-rigid joints on the design of cold-formed steel portal frame structures

This paper investigates the effect of semi-rigid joints and finite connection length on the design of cold-formed steel portal frames. The performance of frames sized using a rigid joint and full joint strength assumption is compared with frames having semi-rigid joints and partial strength. It goes on to describe whether it can offset the fact that the joints cannot sustain the full moment capacity of the sections. Experimental, analytical and finite element modelling techniques have been used. They demonstrate that frames of modest span sized using a rigid joint and full joint strength assumption, are unsafe under gravity load and do not satisfy the ultimate limit state. Designers should therefore take the semi-rigidity and partial strength of the joints into consideration when analysing cold-formed steel portal frames

The structural behaviour in fire of a cold-formed steel portal frame having semi-rigid joints

This paper describes a non-linear finite element study into the effects of elevated temperature on a cold-formed steel portal frame having semi-rigid joints. Numerical modelling was carried out using ABAQUS finite element analysis software with shell elements used to capture localised buckling effects. Results for the ambient shell models are compared against previous full-scale tests. Material properties are taken from the literature, in order to predict the behaviour of the frame at elevated temperature. The results of finite element beam models are compared against those of shell models to enable comparison. At elevated temperature, shell models are shown to detect failure much earlier within the fire. Therefore shell models are recommended for such studies, for a conservative approach

Effect of nanosilica addition on the fresh properties and shrinkage of mortars with fly ash and superplasticizer

The ongoing use of various mineral additions along with chemical admixtures such as superplasticizers justifies the need for further research. Understanding and quantifying their effects and possible synergies on the fresh and hardened properties of cement-based materials is necessary, especially if some of these components are known to have a pozzolanic effect. This paper describes and models the fresh and hardened properties of cement mortars including nanosilica and fly ash, and relates their properties to the proportioning of these materials and the superplasticizer dosage. Mini-slump, Marsh cone and Lombardi cone tests were used to examine the properties of the fresh mortars, and to assess density, plastic shrinkage, and drying shrinkage up to 20 days. The equations presented in this paper make it possible to optimize mortar proportionings to the required levels of performance in both fresh and hardened states

Numerical Derivation of Iso-Damaged Curve for a Reinforced Concrete Beam Subjected to Blast Loading

Many engineering facilities are severely damaged by blast loading. Therefore, many manufacturers of sensitive, breakable, and deformed structures (such as facades of glass buildings) carry out studies and set standards for these installations to withstand shock waves caused by explosions. Structural engineers also use these standards in their designs for various structural elements by following the ISO Damage Carve, which links pressure and Impulse. As all the points below this curve means that the structure is safe and will not exceed the degree of damage based on the various assumptions made. This research aims to derive the Iso-Damage curve of a reinforced concrete beam exposed to blast wave. An advanced volumetric finite element program (ABAQUS) will be used to perform the derivation