Zveza društev gradbenih inženirjev in tehnikov slovenije
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Objavljeno v: Gradbeni vestnik - 6, 7 - 1965

Avtorji

prof. Svetko Lapajne, inž.

Nekaj prijemov iz prakse statika-konstruktorja

UDK: 69.00:624,04:624.9

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Some features from practice of an engineer-designer

The author presents solutions for th ree little p ro blem
s :
The first problem relates th e calculus of the top
and bottom stiffnesses of an elem ent w ith irreg u lar
m om ent of inertia. The basis is the m ethod of the
elastical center. Com puting th e Csonka’s stiffness —V
d s/j
an d th e sidesw ay-stiffness ~ i r 7 ~ r all z2 ds/j the other stiffnesses
and the carryoverfactor coefficients are easily obtainable.
The second problem deals w ith th e size of the
su p p o rt m om ents of a sq u are tw o-w ay slab, fully
re stra in t and uniform ely loaded, so th a t the Poisson’s
ratio is taken into acount. T he bending m om ents of
the other orthogonal direction cause a reduction of
yielding on the observed direction. The deduction yields
for the fixed-end m om ent the expression q L2 . 0,0323
and for the positive field m om ent q L2 . 0,0215.
The th ird problem is th e control designing of compressed
construction elem ents, loaded w ith an exceptionally
strong w ind blow (150% of th e usual). For
this case our code allow s 150 °/o higher stresses. It is
proved, th a t th ere is n ’t question for all p u rely bended
sections, nor fo r concrete tresses in columns. M eanw
hile in stanchions th e am ount of steel reinforcem ent
increases. F or th is case a form ula is given, using the
norm al allow able stresses and the norm al w indm om ents
in com bination w ith only 2/3 am ount of th e norm al
axial com pression and only 2/3 of the bending m om ent
acused by the v ertical loading.

Synopsis

The author presents solutions for three little problems :The first problem relates th e calculus of the top and bottom stiffnesses of an elem ent with irregular moment of inertia. The basis is the m ethod of the elastical center. Com puting th e Csonka’s stiffness —V d s/j an d th e sidesw ay-stiffness ~ i r 7 ~ r all z2 ds/j the other stiffnesses and the carryoverfactor coefficients are easily obtainable. The second problem deals w ith th e size of the support moments of a square two-way slab, fully re stra in t and uniform ely loaded, so th a t the Poisson’s ratio is taken into acount. T he bending m om ents of the other orthogonal direction cause a reduction of yielding on the observed direction. The deduction yields for the fixed-end m om ent the expression q L2 . 0,0323 and for the positive field m om ent q L2 . 0,0215. The th ird problem is th e control designing of compressed construction elem ents, loaded w ith an exceptionally strong w ind blow (150% of th e usual). For this case our code allow s 150 °/o higher stresses. It is proved, th a t th ere is n ’t question for all p u rely bended sections, nor fo r concrete tresses in columns. Meanw hile in stanchions th e am ount of steel reinforcem entincreases. F or th is case a form ula is given, using the norm al allow able stresses and the norm al wind moments in com bination w ith only 2/3 am ount of the norm alaxial com pression and only 2/3 of the bending moment acused by the v ertical loading.

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