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A: Zone acceleration coefficient according to the seismic zone and the using group of the building (See Table 1, Fig. 1)
D: Average dynamic amplification factor, depending on the site category, the damping correction factor η and the fundamental period of the structure T (See Fig.2)
T2: Characteristic period associated to the category of the site
(See Table 2)
η: Damping correction factor given by the following formula:
ξ: Critical damping ratio (%) depending on constitutive material, structure type and importance of infill (See Table 3)
R: Global behavior coefficient of the structure according to the lateral force resisting system (See Table 4). In case of different lateral force resisting systems in two considered directions, the smallest value of R must be used.
Q: Quality factor of the structure given by the following formula:
Pq: Penalty to be applied depending on whether the criteria of quality q "is satisfied or not" (See Table 5)
W: Total weight of the structure that is equal to the sum of the weights Wi calculated at every floor I
WGi: Weight of dead loads and eventual fixed equipment
WQi: Live loads
β: Weighting coefficient depending on the nature and the duration of the live load (See Table 6)
Category S1 (rocky site): Rock or other geological formation characterized by an average shear wave velocity Vs ≥ 800 m/s
Category S2 (firm site): Very dense gravel or sand and/or over consolidated clay deposits with a thickness of 10 to 20 meters and
Vs ≥ 400 m/s from a depth of 10 meters
Category S3 (soft site): Thick deposits of moderately dense gravel andsand or moderately stiff clay with Vs ≥ 200 m/s from a depth of
10 meters.
Category S4 (very soft site): Loose sands deposits with or without
soft clay with Vs < 200 m/s within the 20 first meters
Any building treated by the present rules should be classified in one of the four groups provided
the lateral load
resisting structural systems
A) Reinforced concrete structure
1.a : Moment resisting space frames without rigid masonry infill walls
The building must not exceed five (05) stories or 17m height in Zone I, four (04) stories or 14m height in Zone IIa, and three (03) stories or 11m in height Zone IIb and III.
1.b : Moment resisting space frames with rigid masonry infill walls
The building must not exceed five (05) stories or 17m height in Zone I, four (04) stories or 14m height in Zone IIa, three (03) stories or 11m height in Zone IIb and two (02) stories or 8m height in Zone III.
Nota:
In the case of the first story is used for
commercial where a density of dividing walls is less relatively the upper
stories and make soft story, to ask for bracing the building assured by a system
with shear walls in two directions (mixed system, moment resisting frames-shear
walls, or reinforced concrete central core).
To remember that the soft story have the lateral stiffness less than 70% of the stories neighbouring or less than 80% of the average lateral stiffness of three stories upper.
12. Tied (confined) bearing masonry structures
Those kind of buildings are limited for five (05) stories or 17m height in Zone I, four (04) stories or 14m height in Zone IIa and three (03) stories or 11m height in Zone IIb and III.
17. System including transparencies (soft stories)
To ovoid this system, otherwise we take a measurement to rigidify in order to attenuate this phenomena.
concrete structures
For the main elements, the concrete must have the strength fc28 not less than 20 Mpa and less than 45 Mpa.
The value of Elasticity modulus must be according the rule C.B.A.
Formwork
The columns must doing in all the height in one time, the heel-piece is forbidden.
Min(b1,h1) ≥ 25 cm in Zone I an IIa
Min(b1,h1) ≥ 30 cm in Zone IIb an III
Min(b1,h1) ≥ he/20
1/4 < b1/h1 < 4
For the cylindrical column, the diameter D must satisfy those conditions:
D ≥ 25 cm en Zone I
D ≥ 30 cm en Zone IIa
D ≥ 35 cm en Zone IIb and III
D ≥ he/15.
The section of the columns in the side or the corner must be comparable than the central column.
Rebar of reinforcement
Longitudinal rebar
Minimum ratio
0.8% in Zone IIa
0.9% in Zone IIb and III
Maximum ratio
3% in current zone
6% in recovery zone