Rigidity EI Research Articles

Improved ‘EI’ estimation for reinforced concrete circular columns

An exact analysis is carried out utilizing the stress-strain curve for concrete confined by circular hoops and a typical idealized stress-strain curve for steel to develop the moment-curvature relationship for reinforced concrete (RC) circular column sections. Based on that, the flexural rigidity EI of the section is determined at the yield curvature. A computer program is written in Fortran 77 to handle the required computations. The influence of material properties, the effect of steel ratios and the impact of axial loads on the EI estimation were investigated. This study leads to the development of a new equation to estimate the flexural rigidity EI of RC circular columns in which these factors were considered. It is shown that the new equation stems from the actual behaviour of the column. Therefore, it is recommended for general use in the design of slender columns.

BIOMECHANICS OF PSILOTUM NUDUM AND SOME EARLY PALEOZOIC VASCULAR SPOROPHYTES

The elastic modulus E, flexural rigidity EI, static loading P, and volume fractions V of tissues of the aerial portions of Psilotum nudum are examined in terms of two Voigt models: 1) total elastic modulus ET of a branch element is considered the additive property of the elastic modulus of tissues times their respective volume fraction, i.e., ET = (EV), + (EV)2 + … (EV)n, and 2) ET is considered the product of the elastic modulus of cell walls and the apoplastic volume fraction, i.e., ET = EcwVa. The parameters EI and P, together with the length (l) of each branch element are combined into a dimensionless ratio, Pl2/EI (the load parameter L), to describe the relationship between static loading (Pl2) and the ability to sustain loading (EI). The load parameter of branch elements was found to decrease as the level of branching within aerial portions of this race of Psilotum was ascended. The magnitude of P also decreased acropetally. However, the decrease in L is primarily due to a disproportionate decrease in EI. The load parameter of the basalmost branch of aerial portions is smaller for larger aerial portions of this race of P. nudum. Thus, larger specimens are subtended by more rigid branch elements than smaller aerial portions. The Voigt models provide satisfactory approximations of the data from this race Psilotum and indicate that the principal load supporting tissues are the cortical sclerenchyma and other lignified tissues in older (lower branch elements). The mechanics of the three dimensional branching of P. nudum is extended to consider the aerial portions of some early Paleozoic vascular sporophytes (Algaophyton, Rhynia). Analyses indicate that biomechanical speculation about these fossils is potentially flawed by the ambiguity of anatomical data.

ON THE SOFTNESS AND SHEARING PROPERTIES OF SILK FABRICS

The pliable handle of textile fabrics different from paper and plastic film may be due to the large deformation in shear.In this paper, firstly the typical load-deformation curves in shear of silk fabrics such as Habutae, crepe and taffeta, and more nonwoven fabric, paper and glass cloth are discussed generally, secondly the softness of silk fabrics are examined by the relation between bending stiffness EI and shear angle _??_, and finally the relationships between air quantity ratio and shear properties, and also the relations between sensory scale values of softness and flexural rigidities and shear angles for Habutae cloths were investigated. The results obtained were as follows:1. The shapes of shearing load-deformation curves are different by the kinds of fabrics. They may be explained by the effects of frictional and elastic forces, on the other hand the character of fabric can be assumed by the shape of load-deformation curve in shear.2. The relation between the bending stiffness EI and shear angle _??_ of silk fabrics shows an inverse correlation. Assuming that softness is dependent on shear angle _??_ and liveliness depends upon bending stiffness EI for silk fabrics, it is considered that when both EI and _??_ of fabrics are large its fabric will show soft and lively handle.3. Shear angle for Habutae cloths increase as the air quantity ratio increase. The air quantity ratio on Habutae cloths is related to shear angle _??_ and apparent specific gravity and percentage of air quantity in the fabric. The sensory values of softness on Habutae cloths are largely connected with shear angle _??_ rather than in flexural rigidity EI. From the above fact it is considered that Habutae cloths become soft in proportion to the air quantity ratio increase and also the deformation in shear increase.

VISCOELASTIC STUDIES OF TEXTILE FABRICS

The flexible rigidities (EI) of the many kinds of fabrics (Table 1) are measured by heart loop method.(1) EI of fabric depends upon the bending mode of test piece. An EI of fabric having the long floats on its surface is smaller in face-to-face bending than back-to-back. (Fig. 1 & 2)(2) An EI of low freeness fabric is generally small, but there are many deviations from this tendency, e. g. in basket weaves.(3) An effect of crimp of component yarn of fabric to the EI of fabrics is generally small. When the crimp is of sine wave, apparent rigidity Da is: Where σ: a/b π, a: amplitude, b: the length of period. So, in the case of σ_??_1 a crimp efiect is very small and neglegible, ordinary fabrics are in this category.(4) The flexible rigidity of yarn calculated by means of dividing the fabric rigidity with yarn density EI (F) are generally larger than the true rigidity EI (T) of compornent yarn measured by the experiment.The rigidity factor S may can be descriced in general as;where l is true length contributing to yarn bending. In the ordinary fabrics, warp and weft yarns come in contract each other not at geometrical contact point but in contact length. So, true length l is shorter than in the case of ideal geometrical fabric model, i. e. l0=nl.i.e. S is proportional to n, n3 EI(T)=EI(F).In the ordinal clothing fabrics, n=1_??_1.16 (Table 3 & 4)We find that the bending mechanism of fabrics could be explained as the function of the rigidity of compornent yarn and fabric structure.

On the Function and One Method of Stress Analysis of the Structures of Passenger Cars

The strength of the side structures of railway passenger cars has usually been analyzed as a "composit beam", namely, by assuming that the side structures are made of two beams pin-jointed with struts between them. But the side structures are recently designed as rigidly jointed structures, i.e. rahmen structures. The method of slope-deflection analysis can be rationally applied to such structures. Assuming that the external normal load can be taken only by the side stuuctures, the theory of analysis was studied for the structures as shown in Fig. 1. The structural function of upper and lower beams and struts and their mutual action of cooperation were made clear. It was also found that the rigidity EI'/l' and the shear rigidity of struts have an important role for increasing the beam action of side structures so as to be a beam as a whole, and the larger their values are, the greater the effectiveness of struts becomes.