Flexural rigidity

About: Flexural rigidity is a research topic. Over the lifetime, 3829 publications have been published within this topic receiving 56780 citations.

Increased bending rigidity of wool fabric imparted by hybrid organic-inorganic sol–gel coatings

Abstract: Hybrid organic–inorganic coatings prepared by the sol–gel method can impart desirable properties to textiles, but may adversely affect properties such as bending rigidity. This study investigated the causes of increased bending rigidity. Woven wool fabric was pad coated with formulations of methyltriethoxysilane (MTES) and Hercosett polyamide resin, examined by scanning electron microscopy, and the bending rigidities were determined. MTES coatings of up to 3.0% solids on mass of wool did not impart unacceptable bending rigidity. The coatings were not uniform on the fiber surfaces, and the increases in fabric bending rigidity could be partially attributed to inter-fiber bonding. In addition, the coatings “pinned” the edges of the cuticle scales, making individual fibers harder to bend. These effects are only weakly dependent on the Young's moduli of the coating materials.

An Experimental Study on Flexural Behavior of Steel Fiber Reinforced Ultra High Performance Concrete

Abstract: Dept. of Structures & Bridges, Korea Institute of Construction Technology, Goyang 411-712, KoreaABSTRACT In this study, the flexural behavior of steel fiber reinforced ultra high performance concrete (UHPC) was inves-tigated. It presents experimental results of steel fiber reinforced UHPC with steel fiber content of 2% by volume and steel rein-forcement ratio of less than 0.02. This study aims at providing more information about UHPC beams in bending in order toestablish a reasonable prediction model for flexural resistance and deflection in structural code in the future. The experimentalresults show that UHPC is in favor of cracking behavior and ductility of beams, and that the ductility indices range from 6.29 to10.44, which means high ductility of UHPC. Also, the flexural rigidity of beam whose cast is begun from end of beam is largerthan that of beam whose cast is begun from midspan of beam. This result represents that the flexural rigidity is affected by theplacing method of UHPC. Keywords : ultra high performance concrete, flexural rigidity, ductility, crack, deflection

Semi-rigid behaviour of connections in precast concrete structures

Abstract: Multi-storey precast concrete skeletal structures are assembled from individual prefabricated components which are erected on-site using various types of connections. In the current design of these structures, beam-to-column connections are assumed to be pin jointed. This current research work focuses on the flexural behaviour of the beam-to-column connections and their effect on the behaviour of the global precast concrete frame. The experimental work has involved the determination of moment-rotation relationships for semi-rigid precast concrete connections both in full scale connection tests and smaller isolated joint tests. This has been done using the so called "component method" in which the deformation of various parts of the connection and their interfaces are summated, and compared with results from full scale sub-frame connection tests. The effects of stress redistribution, shear interaction etc. are taken of by linear transformation in the results from the full scale tests, enabling parametric equations to be formulated empirically in order to describe the semi-rigid behaviour. Eight full scale column-beam-slab assemblages were tested to determine the (hogging) moment-rotation behaviour of double (balanced loading) and single sided in-plane connections. Two of the most common types of connection were used, the welded plate and the billet type. Proprietary hollow core slabs were tied to the beams by tensile reinforcing bars, which also provide the in-plane continuity across the joint. The strength of the connections in the double sided tests was at least 0.84 times the predicted moment of resistance of the composite beam and slab. The strength of the single sided connections was limited by the strength of the connection itself, and was approximately half of that for the double sided connection, even though the connection was identical. The secant stiffness of the connections ranged from 0.7 to 3.9 times the flexural stiffness of the attached beam. When the connections were tested without the floor slabs and tie steel, the reduced strength and stiffness were approximately a third and half respectively. This remarkable contribution of the floor strength and stiffness to the flexural capacity of the joint is currently neglected in the design process for precast concrete frames. Measurements of the extent of damaged zones near to the connection in full scale tests showed that, unlike steel connections, semi-rigid behaviour in precast concrete does not occur at a single nodal position. In general the double sided connections were found to be more suited to a semi-rigid design approach than the single sided ones. Analytical studies were carried out to determine empirical design equations for column effective length factors β in unbraced and partially braced precast concrete frames. The main variables were the relative flexural stiffness α of the frame members, and the relative linear rotational stiffness Ks of the connection to that of an encastre beam. The variation of β factors with Ks and α are presented graphically and in the form of design equations similar to those currently used in BS 8 110. The change in the response of a structure is greatest when 0 2 the changes in the behaviour are so small that they may be ignored within the usual levels of accuracy associated with stability analysis. This is an important finding because the experiments have found Ks to be generally less than 2 for typical sizes of beam. The results enable designers to determine β factors for situations currently not catered for in design codes of practice, in particular the upper storey of a partially braced frame. A design method is proposed to extend the concrete column design approach in BS 8110 and EC2, whereby the strength and semi-rigid stiffness of the connection enables column bending moments to be distributed to the connected beams. However, the suitability of each type of connection towards a semi-rigid design approach must be related to the stiffness and strength of the frame for which it is a part.

Flexural rigidity of thin auxetic plates

Abstract: The influence of auxeticity on the mechanical behavior of isotropic plates is considered herein by evaluating the plate flexural rigidity as the Poisson's ratio changes from 0.5 to -1. Since the change in plate's Poisson's ratio is followed by a change in at least one of the three moduli, any resulting change to the plate flexural rigidity is only meaningful when at least one of the moduli is held constant. This was performed by normalizing the plate flexural rigidity by a single modulus, a square root of two moduli product, or a cube root of three moduli product to give a dimensionless plate flexural rigidity. It was found that the plate flexural rigidity decreases to a minimum as the plate Poisson's ratio decreases from 0.5 to 0 when only the Young's modulus is held constant. Thereafter the plate flexural rigidity increases with the plate auxeticity. Results also reveal that when only the shear modulus or when the bulk modulus is held constant, the plate flexural rigidity decreases or increases, respectively, with the plate auxeticity. Intermediate trend in the plate flexural rigidity is observed when the product of two moduli is held constant. When the product of all three moduli is held constant, the plate flexural rigidity increases with the plate auxeticity, and the change is especially drastic when the plate Poisson's ratio is near to the upper and lower limits of Poisson's ratio for isotropic solids. Results from this work are useful for structural designers to control the flexural rigidity of plate made from auxetic materials.