. The theory of the flexure and strength of rectangular flat plates applied to reinforced concrete floor slabs . f the slab over the column head, while the rest of them are carriedthru under the head at the bottom of the slab. This modificationof design, when a sufficient number of rods go over the head toresist the negative bending moments there, is very uneconomicalof steel, because in the case where they all go over the head, it isthe fact that altho the mean tension of the steel is not so great asat mid span, nevertlu^less, by reason of the overla])ping of the beltsin crossing, the stresse
. The theory of the flexure and strength of rectangular flat plates applied to reinforced concrete floor slabs . f the slab over the column head, while the rest of them are carriedthru under the head at the bottom of the slab. This modificationof design, when a sufficient number of rods go over the head toresist the negative bending moments there, is very uneconomicalof steel, because in the case where they all go over the head, it isthe fact that altho the mean tension of the steel is not so great asat mid span, nevertlu^less, by reason of the overla])ping of the beltsin crossing, the stresses in the* rods at the to]) reach a value notmuch less than at mid si)an, and cannot be saft^ly diminishtHl innumber. It thus appears that the rods carried thru on tht^ bottomare largely sujx^rfluous. Of these two mats of rods at top andbottom, on(; of them is necessarily in tension and tlu^ other in com-prefjsion. But it is a mistake to us(^ Mvc\ to n^sist conipn^ssionwhen concrete can ])e l)etter used for tliis |)iirpos(\ The lo\vi>r matis superfhious for this reason. 58 SMALL HEAD. TOP AND BOTTOM BELTS. — Theoretical line \ Column tread A^ of inflection ^/ ^Assumed line of inflection I 1 1 M I W in pounds per square foot I I I ^,58^* • - • uji/ago/ia/ steel in tuo layers ^^^ \ 1 y^rectangular sttel In^^ o H y^ two layers ^^ / 5 In pounds per linear ^< L_, Fig. 5 There is still another and, if possible, more serious objectionto this arrangement of rods to form a mat or double laj^er of rodsat the top and at the bottom of the slab near the columns. Thisis because they are too far removed from each other in the slabfor the elongations of the steel in one mat to be resisted hj lateralcontractions in the other. The reinforcement does^not thereforeconspire to produce the slab action expressed by Poissons ratio,which requires that the interacting steel concerned should lie approxi-matel}^ in the same zone or level. This arrangement is illustrated in Fig. 5, copied from T
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Keywords: ., bookcentury1900, bookdecade1910, bookidtheoryofflex, bookyear1913
