A treatise on concrete, plain and reinforced : materials, construction, and design of concrete and reinforced concrete; 2nd ed. . /^ +4- 6 J f-^^ equation (57) M= CJ,bh^ (58) Hence in investigating a given section of an arch,if M, b, h, C^ are known,the unit compression in the concrete is M^^=CJhr^ (59) To solve this equation easily, values of C„ should be taken from 180, page 573, gives values of C„ for n = 15, 2a = |/i and variousvalues of k. Evidently before using equations (57) or (59) to find the unit compres-sion in the concrete, the position of the neutral axis must first be
A treatise on concrete, plain and reinforced : materials, construction, and design of concrete and reinforced concrete; 2nd ed. . /^ +4- 6 J f-^^ equation (57) M= CJ,bh^ (58) Hence in investigating a given section of an arch,if M, b, h, C^ are known,the unit compression in the concrete is M^^=CJhr^ (59) To solve this equation easily, values of C„ should be taken from 180, page 573, gives values of C„ for n = 15, 2a = |/i and variousvalues of k. Evidently before using equations (57) or (59) to find the unit compres-sion in the concrete, the position of the neutral axis must first be do this we must find the value of k. Since the moment M = Ne, that is,the thrust multiplied by the eccentricity, equation (56) may be multipliedby e and equated to (57). From this process, the following equation con-taining k is obtained Jl/= moment, n = ratio elasticity. A= thrust. /c=compression in concrete. /8 = tens!onin steel, /s = compression in steel, b = breadth. h = height, e = eccentricity, p = ratioof steel. k = ratio depth neutral axis. Ca = constant. 572 lO VALUES OF ECCENTRICITY CO (N S d do. VALUES OF ECCENTRICITY Fig. 179.—Diagram for Determining Depths of Neutral Axis for Different Eccen- 4tricities. Based on « = 15 and 2a = — h. {See p. 574.) 573
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