A Comparative Investigation on Normal and High Strength Concrete Beams under Torsion

In this study, an experimental investigation was done to study the behaviour of Normal Strength Concrete (NSC) and High Strength Concrete (HSC) Plain beams under torsion with the concrete mix of M40 and M100. No mineral admixtures are used to obtain the required strength of concrete. Eight NSC beams and eight HSC beams whose width was varying with 75 mm, 100 mm, and 150 mm; depth varying as 75 mm, 100 mm, 150 mm and 200 mm; and span of the beams varying 600 mm, 800 mm and 1200 mm were casted and cured to stud the effect of torsion. The principle aim of this study was to understand the torsional behaviour of the NSC and HSC beams for rotation, cracking, size effect and torsional strength. A standard torsional loading method was used for conducting the testing of beams. The results obtained were compared with different theories and code equations. It was observed that the torsional strength of the beam increases with the increase in strength of concrete. HSC beams have higher torsional strength than the NSC beams which has the same amount of reinforcement.

INVESTIGATION OF HULL STRENGTH OF RIVER SEA CONTAINER VESSEL

River sea vessels are ships for inland navigation and suitable for restricted navigation at sea in regions where, - significant wave height does not exceed 2m, according to Bureau Veritas Rules for the classification of inland vessels. In a container vessel structure, almost the entire deck space is occupied by hatches, leaving a narrow strip of deck plating outboard. This calls for a topside structure of heavy plating or a double hull to provide material in tension, stiffness against lateral and torsional loads, and resistance to buckling in compression when the vessel is in sagging condition. For sea going open deck vessels, torsional loading plays a predominant part to the hull girder strength and for inland navigation open deck vessels; the effect of torsion is rather negligible. Keeping this scenario in mind, the aim of this project is to investigate the hull strength of a river sea container vessel under combined bending and torsional loading to study the effect of torsion on river sea open deck vessel. To perform the strength analysis, firstly, a finite element model is created using Femap with NX Nastran software for the investigated vessel. Therefore, still water and wave loads are calculated using direct calculation. To find out the still water loads Argos software is used and for the wave induced loads potential flow software Hydrostar is used. Next, Finite element model is verified with classical beam theory and thin wall girder theory. Then the effect of various loading conditions on structural response is investigated. After, structural response of different hull configurations are scrutinized under combined bending and torsional loading. Finally, some recommendations are proposed for structural response of river sea container vessel subjected to combined bending and torsional loading.

Yield and fracture loci for a ductile cast iron EN-GJS-600-3 under biaxial stresses

Biaxial (axial and torsional loading) static tests were performed for the first time on EN-GJS-600–3 ductile cast iron tubular specimens obtained reproducing the solidification conditions typical of thick-walled castings. The experimental results were elaborated to determine the yield and fracture loci of the material, which exhibited significant deviations from those predicted by the Von Mises and Mohr-Coulomb criteria usually adopted for steels and grey cast iron, respectively. For this purpose, several alternative criteria proposed in the technical literature, some of them specifically devised for composite materials, have been calibrated and compared to account for the peculiar mechanical properties of this natural composite material.

Behavior of Reinforced Concrete Plates under Pure Torsion

The behavior of reinforced concrete members under torsional loading has interested many researchers during the last decades. These researches focused mainly on the response of reinforced concrete beams at different reinforcement conditions and the size effects. On the other hand, the behavior of concrete plates or slabs has not been investigated clearly under pure and/or combined torsional loading. In the present study, nine reinforced concrete plates were prepared and tested under pure torsion. Effect of steel reinforcement ratio and size change was studied and they have a great effect on the plated strength, capacity, stiffness and ductility. As stated by torsion theories of reinforced concrete beams, the torsional strength of slabs was upgraded also with increasing in cross section and transverse reinforcement ratio.

Lateral migration resistance of screw is essential in evaluating bone screw stability of plate fixation

Conventional evaluation of the stability of bone screws focuses on pullout strength, while neglecting lateral migration resistance. We measured pullout strength and lateral migration resistance of bone screws and determined how these characteristics relate to screw stability of locking plate (LP) and dynamic compression plate (DCP) fixation. Pullout strength and lateral migration resistance of individual bone screws with buttress, square, and triangular thread designs were evaluated in polyurethane foam blocks. The screw types with superior performance in each of these characteristics were selected. LP and DCP fixations were constructed using the selected screws and tested under cyclic craniocaudal and torsional loadings. Subsequently, the association between individual screws’ biomechanical characteristics and fixation stability when applied to plates was established. Screws with triangular threads had superior pullout strength, while screws with square threads demonstrated the highest lateral migration resistance; they were selected for LP and DCP fixations. LPs with square-threaded screws required a larger force and more cycles to trigger the same amount of displacement under both craniocaudal and torsional loadings. Screws with triangular and square threads showed no difference in DCP fixation stability under craniocaudal loading. However, under torsional loading, DCP fixation with triangular-threaded screws demonstrated superior fixation stability. Lateral migration resistance is the primary contributor to locking screw fixation stability when applied to an LP in resisting both craniocaudal and torsional loading. For compression screws applied to a DCP, lateral migration resistance and pullout strength work together to resist craniocaudal loading, while pullout strength is the primary contributor to the ability to resist torsional loading.

Effect of Axial Deformation Caused by Torsion on a Solid Steel Cylinder

Equations describing the classical theory of applied torsion and axial rotation on a solid cylindrical shaft have been modified by Shirali and Hossain (2019) to derive new theorems, which can take into consideration axial deformation of members. The modified theorems use various empirical parameters to introduce the combined effect of axial force, axial displacement and axial rotation, which is neglected in classical theorems of torsion. Multiple finite element analysis models for solid steel cylindrical members, fixed at one end and subjected to torsion at its free end, were developed to study the effects of torsional loading. The effect of axial deformation/stress developed in the cylinder is analyzed and compared with values predicted by classical and proposed modified theorems (equations). It is shown that the cylinder can shorten or elongate when subjected to torsion. The proposed theorems/equations, based on axial deformation subjected to torsion, provide more accurate predictions of shear stress and axial rotation (angle of twist).

Effect of Axial Deformation Caused by Torsion on a Solid Steel Cylinder

Equations describing the classical theory of applied torsion and axial rotation on a solid cylindrical shaft have been modified by Shirali and Hossain (2019) to derive new theorems, which can take into consideration axial deformation of members. The modified theorems use various empirical parameters to introduce the combined effect of axial force, axial displacement and axial rotation, which is neglected in classical theorems of torsion. Multiple finite element analysis models for solid steel cylindrical members, fixed at one end and subjected to torsion at its free end, were developed to study the effects of torsional loading. The effect of axial deformation/stress developed in the cylinder is analyzed and compared with values predicted by classical and proposed modified theorems (equations). It is shown that the cylinder can shorten or elongate when subjected to torsion. The proposed theorems/equations, based on axial deformation subjected to torsion, provide more accurate predictions of shear stress and axial rotation (angle of twist).