STAS 10107/0-90

- brief notes -

1. Reinforcement anchorage:

a) longitudinal

l_a l_ad ; d=diameter of rebar

It will be considered to have severe solicitation conditions:

the reinforcement of elements with antiseismic strength purpose in constructions belonging to seismic zones AF, only in the potential plastic zones

the reinforcement of elements acted upon by important concentrated forces, situated at distances smaller than 40d from the interior bound of supports

the reinforcement of elements computed for the fatigue limit state

It will be considered to have defavorable conditions of adherence:

the rebars having a horizontal position during casting (or an inclinement smaller than 45^o with respect to the horizontal), placed in elements with height h>=300mm and situated in the superior part of the element ;

horizontal rebars from the vertical elements of the structures, having great height and thickness <= 300mm (structural walls, reservoir walls and silos..) ;

when justified, in special cases, other reinforcement for which the reinforcing conditions, technological conditions of concrete casting or some other causes could unfavorably influence the adherence within the anchorage zones (ex: structures executed using sliding forms).

b) transversal

for ties and stirrups there will be hooks bent at 135^o or 180^o in case of OB stirrups and only 135^o in case of PC ;

2. Reinforcement splicing

by welding: compulsory for bars with d>=32mm and recommended for bars with d>=25 mm ; welding will not be used for bars with d<=10mm

in the potential pastic zones splicing will be avoided; if not possible, the splicing of all bars with d>=16mm will be done only by welding. In case of bearing vertical elements this provision will be applied only for the base level;

splicings will usually be placed in zones of minimum effort in rebars; for the vertical bearing elements, the splicing is admitted above the level of each floor plate;

for the rebars spliced by overlapping, situated in zones where in any loading group they remain subjected to compression, the overlapping length will be: 30 d for elements with concrete class < Bc25 and 20 d in case of elements with concrete class > Bc25

3. Supplementary provisions for columns

The present provisions are referring to columns with significant axial loads:

There will be considered the following groups of columns:

group A : columns participating to antiseismic structures with significant post-  elastic deformations and require specific ductility measures, in seismic zones AE

group B : columns participating to antiseismic structures, designed to remain in the elastic range under the seismic action, in seismic zones AE or columns in the seismic zone F

group C : columns not participating to antiseismic structures or columns with low values of loads, designed to remain in the elastic range in the sesmic zone F

The concrete section

for orthogonal sections, the minimum dimension is 250 mm and for circular  sections D250mm

the dimensions must be a multiple of 50 mm

the ratio between the sides of the section is usually established as:  h/b2.5

Longitudinal reinforcement

minimum diameters 12mm for bars PC60 and PC52, 14mm for OB37

maximum recommended diameters: 28mm for columns with usual concrete and 22mm for columns with ligth aggregate concrete

bvnm

clear minimum space between bars 50mm

maximum interaxial distance 250mm ; the reinforcing with only 4 bars in the corners of the section is addmitted only for columns having the sides of the section 350mm for columns belonging to group A and 350mm for groups B and C ; for circular columns, the minimum no. of bars is 6.

total longitudinal reinforcement percentage p:

maximum p : p_max = 2.5% (recommended)

minimum p :

minimum reinforcement percentage on each side of the section is: p_{min_side} = 0.20

the maximum slope for the deviation of the longitudinal reinforcement, through the height of the beams, in case of changing of the columns section is

Transversal reinforcement

the distance between the stirrups through the height of the column should be:

for the group A columns, there will be provided closely spaced stirrups :

in the potential plastic zones at the inferior extremity of the columns at all storeys, in all cases

in the potential plastic zones at the superior extremity of the columns at each storey, if : 

in the potential plastic zones at the superior extremity of the columns when there is the possibility of occurrence of plastic hinges, in the case of short columns or at the columns belonging to structures at which some structural walls are missing, from functional reasons

the length of the plastic zone l_p is measured from the superior, or inferior respectively, face of the beam and it is taken as :

if, at the dimensioning of the column, it is admitted that: then the length l_p increased by 25%

over the length l_p , the distance between the stirrups must follow the rules:

for the columns belonging to group A, the straight portions at the end of the hooks of stirrups, must be taken as 10 d instead of 5 d

over the length of overlappping of longitudinal reinforcement we must provide closely spaced stirrups, as for the plastic zones; at the base of the columns in groups A&B there will be provided closely spaced stirrups form the superior face of foundation until the end of the l_p portion, measured from the upper face of the flooring

for the columns belonging to group A for which (short columns), there will be provided closely spaced stirrups, as for the plastic zones, over the whole height of the respective storey

the diameter of the stirrups must follow the rules:

the need for intermediary stirrups is established considering:

for the group A columns, each longitudinal bar must be tied to a stirrup corner ; it is admitted that the longitudinal bars to be tied from 2 to 2 sirrup corners if the distance between 2 consecutive branches is less than 200 mm ;

for the columns in seismic zones F there are admitted only perimetral stirrups, outside the potential plastic zones, if : , with 3 bars on each side ;

for the columns in groups B&C there are provided intermediary stirrups in all the cases in which there are over 3 bars on each side, if and when there are over 4 bars/side, if ;

the transversal reinforcement percentage on the direction of one side b of the columns section will be computed with the formula:

, where :

A_e the cross sectional area of one stirrup branch

n_e the number of stirrups branches intersected by a plan parallel to side b

a_e the distance between stirrups over the height of the column

- on the direction of each side, the minimum p_e should be:

- for the columns of groups B&C:

- for the columns in group A :

outside the potential plastic zones:

within the potential plastic zones:

- if :

- if :

in which :

3. Supplementary provisions for beams

The concrete section

the medium reinforcement percentage, will usually be between 0.81.8 %

for the beams subjected to bending with torsion, in the case when it is recommended that :

the dimensions of the cross section are, usually, multiple of 50 mm for and multiple of 100 mm for

The longitudinal reinforcement

the minimum diameter is 10 mm ; for light-weight concrete beams, the bars with d>12mm must be from PC

the clear distances between the bars:

the distance between the axes of the bars, in the tensioned zones, must be, usually, max. 200 mm

the minimum reinforcement percentages, in the tensioned zones, are:

in the suport sections of the beams participating to antiseismic structures, the ratio between the bottom and the upper reinforcement should be:

- in the seismic zones A,B,C

- in the seismic zones D,E

the anchorage and splicing of this type of reinforcement is performed as for bars subjected to tension ; for the anchorage in the supports of the bottom reinforcement, it is recommended the following setting:

Longitudinal constructive reinforcement

in the regions in which there is no need for structural longitudinal reinforcement in beams at the upper part, there will be provided one bar at each stirrup corner ;

for beams with , intermediary reinforcing bars will be provided on the lateral faces of the beam, at distances of at most 400 mm over the height of the section, tied up together by transversal ties

the minimum admitted diameters of longitudinal constructive reinforcement:

they will not be smaller than the diameter of the stirrup

Transversal reinforcement

the minimum diameters of the stirrups in case of tied-up cages:

, where d is the maximum diameter of longitudinal reinforcement;

6 mm for beams with

8 mm for beams with

the minimum diameters of the transversal bars in case of welded cages: F_min = 4 mm

for beams with there will be provided stirrups with minimum 4 branches

closed stirrups will be provided:

over the entire length of independent beams, without a slab at the upper flange ;

in zones where there are structural rebars at the upper face of the beam or if the beam has a slab at the upper flange

maximum distances between stirrups a_e :

in the regions where there is compressed reinforcement resulted from computation:

for the usual concrete beams ;

for the light-weight concrete beams ;  d = the minimum diameter of the longitudinal reinforcement in the compressed zone

in the potential plastic zones of the beams participating to antiseismic structures, over the length l_p : 

in all other cases :

for the beams participating to antiseismic structures, in the seismic zones AE, the minimum transversal reinforcing percentage p_e in the potential plastic zones must be:

the potential plastic zones are usually considered as the zones of extremities of all beams, developed over the length l_p usually equal to 2h ; h = the height of the beam

usually, the length l_p= 2h is measured from the column face :

in the situations when the critical section for negative moment is offset from the column face at a distance , consider the following:

3. Supplementary provisions for slabs

The thickness of the slabs

is established considering the following:

p_med will usually be below 0.8% for one-way slabs and below 0.5% for two-way slabs

the deflections to be kept under the allowable limits

accoustic insulation

the slabs with high concentrated forces and flat slabs will be checked for punching

minimum allowable thickness: - 60 mm for monolithic slabs

- 30 mm for prefab. Slabs with 10 mm concrete covering

the thickness will be, usually, a multiple of 10mm

The reinforcement

minimum diameters: - 6 mm for bottom straight bars

- 6 mm for inclined bars and top bars if theyre PC60 or PC52

- 8 mm for inclined bars and top bars if theyre made of OB37

- 5 mm for welded wire meshes

minimum no. of bars / meter

for h_p: 5 bars/m

for 300mm< h_p: 4 bars/m

for h_p: 3 bars/m

the maximum no. of bars is 12 bars/m

constructive details

for one-way slabs, there will be provided constructive reinforcement on the direction   perpendicular to the resistance reinforcement :

in the tensioned zones in field and supports, distribution reinforcement with the section /meter equal to at least 15% of the resistance diameter but not less than 4F6 /m for individual bars reinforcing and 5F5 /m for welded meshes

for the negative moments in the supports, local upper reinforcement will be provided