Percentage Of Tension Research Articles

Effect of compression reinforcement on modulus of elasticity of RC beams under flexure

In structural analysis, precise estimation of modulus of elasticity, cross-sectional area and moment of interia of the section play an important role. It is a key factor while carrying out structural analysis for indeterminate structures. Most of the international codes quantify material behaviour for concrete as well as steel in elastic zone and is equally correct. Indian codal provisions express modulus of elasticity of concrete in terms of characteristic strength of concrete only similar to all other international codes. Structural analysis of a high rise building demands cross-sectional area of unreinforced concrete. However, area of reinforcement and stirrups provided are overlooked in the analysis. Contemporary design practice necessitates additional cycle of analysis along with design. First cycle of analysis shall yield the conventional design of sections and are of reinforcement. Based on calculated area of steel in first cycle, it is possible to arrive at effective area of concrete and respective moment of inertia by considering reinforcement in tension and compression zone. The analysis of sections can further be carried out in pre and post cracking conditions. At this stage, material as well geometrical properties play an important role. Present aim of study is to determine modulus of elasticity of reinforced concrete beams with percentage of compression reinforcement ranging from 0.29 to 0.43%. The outcomes are used to propose an empirical equation for evaluation of modified modulus of elasticity of reinforced concrete material which is a dependent on concrete grade along with percentage of tension and compression reinforcement.

Axial Force-Bending Moment Limit Domain and Flow Rule for Reinforced Concrete Elements Using Euro Code

Performance-based design approach of special moment-resistant reinforced concrete (RC) framed structures demands a thorough understanding of axial force—bending moment (P—M) yield interaction of RC elements, particularly when the structure is subjected to seismic loads. Latest design approach includes desirable features of both ultimate strength and working stress to ensure a suitable ductile deformation response. This demands a detailed understanding of nonlinear response of P—M interaction. A complete set of analytical expressions for P—M yield interaction are proposed in a closed form by defining the limit boundary with ten sub-domains based on Euro Code currently in prevalence. P—M interaction relationships are also verified for plastic flow-rule in two main sections namely: (i) tension failure resulting in yielding of steel; and (ii) compression failure resulting in crushing of concrete. The conventional limit P—M domain is described based on Euro Code as long as the plastic strain increment becomes nearly normal to the yield domain over the part of bending response in the presence of axial force. The verified flow rule shows a close agreement in all sub-domains of tension failure, while does not qualify in few of the sub-domains of crushing failure. Practical examples of RC sections are chosen to illustrate the influence of different parameters namely: (i) cross-section dimension; (ii) percentage of tension and compression reinforcements; and (iii) properties of constitutive materials on the P—M boundary. Mathematically developed P—M interaction model is capable of identifying the damage mechanism of different sub-domains in RC sections; damage identification is made on the basis of strain profile of concrete and reinforcing steel.

Isotonic and isometric responses of different tonic muscles to agonists and antagonists.

1 With isotonic recording the percentage of muscle shortening as compared with the maximal possible shortening, and with isometric recording the percentage of developed tension were determined. In relatively 'thick' muscles, such as dorsal leech muscle, frog rectus abdominis or protractor pharynx of holothuria (0.3-0.8 mm thick), the concentrations of a full agonist (carbachol) producing a given percentage of tension, (e.g. 50%) are about 5 times greater than the concentrations, producing the same percentage of shortening. In 'thin' muscles the difference between the percentage of shortening and tension is either small (retractor dentis of the sea urchin, 0.1 mm thick, response to carbachol) or absent (guinea-pig ileum, 0.06 mm thick, responses to methylfurmethide). The possible mechanism underlying this difference is discussed. 2 With partial agonists (dodecamethonium and heptamethonium) the fractional tension of the frog rectus abdominis is always less than the fractional shortening and the correlation between shortening and tension is the same as in the case of full agonists. 3 The blocking activity of (+)-tubocurarine on the frog rectus abdominis is the same in isotonic and in isometric conditions. 4 On the frog rectus abdominis the alkylating agent, decamethonium mustard, does not produce any 'parallel shift' of the dose-response curve for carbachol, the only result of alkylation being a decrease in maximal response, which is more pronounced in isometric than in isotonic conditions. The degree of decrease is in accordance with the correlation between percentage of shortening and percentage of tension in the absence of alkylating agent. Probably this muscle does not possess any 'spare receptors'. 5 On the frog muscle the dose-isometric response curve for acetylcholine (ACh) is shifted toward greater concentration about 33-fold as compared with the dose-isotonic response curve but after the inhibition of cholinesterases the shift is only about 6-fold. The same shift (5-fold) is observed for carbachol, which is not hydrolysed by cholinesterases. The results with ACh are due to the fact, that after cholinesterase inhibition the sensitivity to ACh increases in isotonic conditions only 13-fold, but in isometric conditions it increases 71-fold. Probably under isometric conditions, when the muscle remains in the extended state, the rate of hydrolysis of ACh is much greater than under isotonic conditions when the muscle is shortened during contraction.