Macau Wind Code 2008

CIVL 426 Reinforced Concrete II

CIVL426 by W.M.Quach, 2008

Wind Action – Articles

Wind ( Characterization ) Article 17°

Topography (Topographic effect ) Article 18°

(Shape Configuration,
Structures Wind permeability ) Article 19°

(Dynamic sensibility,
Dynamic effect Applicability condition ) Article 20°

CIVL426 by W.M.Quach, 2008

Wind Flows on Buildings

Shielding Effect
(www.iitg.ernet.in/iccms06/cd/pdf/b024)
Streamlines of wind flows
(http://www.arigreenenergy.com/ )
CIVL426 by W.M.Quach, 2008
Shielding Effect and Interfacial Layer for
Low-rise Building Groups (height < 10m)

(from NAHB Research Center, Inc., USA. 1998)

CIVL426 by W.M.Quach, 2008

Shielding Effect for High-rise Building
Groups

Building
considered

(Van
CIVL426 by W.M.Quach, Uffelen 2009)
2008
 Shielding Effect for High-rise Building
Groups

Mean forces

IF =
Fluctuating
Wind load (buildings in
forces
Group) / Wind load
(Solitary building)
(Van Uffelen 2009)
CIVL426 by W.M.Quach, 2008
 Article 17° – Wind Action & its effect on
Structures
The scope of the code specifications includes the
following types of ordinary structures:
1. Regular buildings with height up to 200m;
2. Bridge structures (excluding cable-supported
bridges) having span up to 200m.
3. Dynamic Non-sensitive Building Structures
with na > 1 Hz.
4. Dynamic Sensitive Building Structures with
0.2 Hz < na < 1 Hz.
Note: na = the first mode fundamental frequency of
the structure
CIVL426 by W.M.Quach, 2008
 Article 17° – Wind Action & its effect on
Structures
Out of the scope of this code:
1. Flexible structures with na < 0.2 Hz;
2. Special flexible structures (e.g., cable structures,
chimneys, lattice towers);
3. Irregular building structures (Significant eccentricities
and torsional vibration effects);
4. Structures with “shielding effects”;
5. Structures with significant “crosswind response”, in
addition to alongwind response;
6. Structures where vibration modes other than the
fundamental mode need to be considered.
Note: na = the first mode fundamental frequency of the
structure
CIVL426 by W.M.Quach, 2008
 Article 17° – Wind Action & its effect on
Structures
The Basis of the Statistical analysis:
1. Wind data base of Macau (the year 1952 ~ 2005);
2. Wind blowing over the sea surface at a height of
250m;
3. All directions were considered in the statistical
analysis;
4. Confidence level of 99.5%;
5. Terrain roughness (only one type of roughness –
wind blowing over the sea surface);
6. Return period of 50 years (equivalent to an annual
probability of exceedance of 2%);

CIVL426 by W.M.Quach, 2008

 Article 17° – Wind Action & its effect on
Structures
The Basis of the Statistical analysis:

Currently Considered

CIVL426 by W.M.Quach, 2008

 Article 17° – Wind Action & its effect on
Structures
Characteristic Gust Wind Pressure Profile:

Mean Wind
Pressure

Gust Wind
Pressure

CIVL426 by W.M.Quach, 2008

 Article 17° – Wind Action & its effect on
Structures
The Safe Verification on Structures exposed to
Wind action:
1. Serviceability Limit State – corresponds to a return
period of 50 years for a partial safety factor of γq = 1.0.

2. Ultimate Limit State – corresponds to a return period of

1000 years, if a partial safety factor of γq = 1.5 .

3. Reduced wind action – apply the combination

cofficients ( ψ0 =0.4, ψ1 = 0.2, ψ2 =0), when the wind
action is not the basic variable.

CIVL426 by W.M.Quach, 2008

 Article 17° – Wind Action & its effect on
Structures
Characteristic
wind pressure

Characteristic
wind force
Wind Structures
Topography Dynamic

CIVL426 by W.M.Quach, 2008

 Article 17° – Wind Action & its effect on
Structures

Characteristic
wind-induced
Friction force
Wind Structures
Topography Dynamic

CIVL426 by W.M.Quach, 2008

 Article 18° and Appendix A of Annex 3 –
Topographic effect (Speed-up effect)

• Local abrupt topography affects wind profiles near ground

(speed-up effect);
• Wind speed up depends on (1) shape of hill, (2) location of
building, and (3) height above ground.

Quantified by the topographic coefficient Ct :

1. Significant, Æ take Ct > 1.0 (Appendix A of Annex 3)
2. Not significant, Æ take Ct =1.0.
CIVL426 by W.M.Quach, 2008
Appendix A of Annex 3 – Topographic
Coefficient

CIVL426 by W.M.Quach, 2008

Appendix A of Annex 3 – Figure IIIA.2
(The value of S)

CIVL426 by W.M.Quach, 2008

Appendix A of Annex 3 – Figure IIIA.2
(The value of S)

CIVL426 by W.M.Quach, 2008

Appendix A of Annex 3 – Figure IIIA.3
(The value of S)

CIVL426 by W.M.Quach, 2008

Appendix A of Annex 3 – Figure III.A.3
(The value of S)

CIVL426 by W.M.Quach, 2008

External and Internal Wind Pressures

External wind pressures (http://www.arigreenenergy.com/ )

Internal wind
pressures CIVL426 by W.M.Quach, 2008
 Article 19° and Appendix B of Annex 3 –
Shape Configuration

1. Pressure coefficient δp ( = δpe – δpi ,

where δpe = external coeff., and δpi =
internal coeff.): +ve = pressure effect,
–ve = suction effect.
2. Force coefficient δf (to define resultant
wind force to structures)
3. Friction coefficient δfr

CIVL426 by W.M.Quach, 2008

 Article 19° and Appendix B of Annex 3 –
Pressure coefficient δp
Pressure coefficient δp = δpe – δpi :
+ve = pressure effect (Inward for δpe ,
Outward for δpi ),
–ve = suction effect (Outward for δpe ,
Inward for δpi ).
1. External pressure coefficient δpe
(depends on shape configuration &
wind direction)
2. Internal pressure coefficient δpi
(depends on air permeability of
building facades)
CIVL426 by W.M.Quach, 2008
Figure III.B.1 – External pressure for
Rectangular Plan Buildings

Wind profiles for

Windward walls
CIVL426 by W.M.Quach, 2008
 Article 17° – Wind Action & its effect on
Structures
Characteristic Gust Wind Pressure Profile:

Mean Wind
Pressure

Gust Wind
Pressure

CIVL426 by W.M.Quach, 2008

Figure III.B.1 – External pressure for
Rectangular Plan Buildings

Wind profiles for

Leeward walls & side walls

For Leeward walls & side walls , the reference height he is

taken as the building height h .

CIVL426 by W.M.Quach, 2008

Figure III.B.2 – External pressure coefficient
δpe for Rectangular Plan Buildings

CIVL426 by W.M.Quach, 2008

Figure III.B.2 – External pressure coefficient
δpe for Rectangular Plan Buildings

CIVL426 by W.M.Quach, 2008

 Tables III.B.1 & III.B.2 – External pressure
coefficient δpe

The case of
h/d > 5 (highly For a loaded
dynamic) is area of 10 m2
out of the
scope, but can
be referred to
EN1991-1-
4:2005.

Applied to
Local action loaded
only used for
areas other
the design of
small elements
than 10 m2
(i.e., purlins,
roof plate
connection ) CIVL426 by W.M.Quach, 2008
Table III.B.3 – External pressure
coefficient δpe for Duopitch roofs

CIVL426 by W.M.Quach, 2008

Table III.B.3 – External pressure
coefficient δpe for Duopitch roofs

CIVL426 by W.M.Quach, 2008

Table III.B.4 – External pressure
coefficient δpe for monopitch roofs

CIVL426 by W.M.Quach, 2008

Table III.B.5 – External pressure
coefficient δpe for cylindrical roofs

CIVL426 by W.M.Quach, 2008

Table III.B.5 – External pressure
coefficient δpe for cylindrical roofs

CIVL426 by W.M.Quach, 2008

Table III.B.6 – External pressure coefficient
δpe for multi-span duopitch roofs

CIVL426 by W.M.Quach, 2008

Table III.B.6 – External pressure coefficient
δpe for multi-span duopitch roofs

CIVL426 by W.M.Quach, 2008

Table III.B.7 – External pressure coefficient
δpe for multi-span monopitch roofs

CIVL426 by W.M.Quach, 2008

Table III.B.7 – External pressure coefficient
δpe for multi-span monopitch roofs

CIVL426 by W.M.Quach, 2008

Article 19° and Appendix B of Annex 3 –
Internal pressure coefficient δpi

CIVL426 by W.M.Quach, 2008

Article 19° and Appendix B of Annex 3 –
Internal pressure coefficient δpi

CIVL426 by W.M.Quach, 2008

 Article 19° and Appendix B of Annex 3 –
Equivalent Overall Pressure (Wind Direct)

Windward Leeward
pressure pressure

Equivalent Overall Pressure in the Wind Direction =

Reduction Factor × Vector Sum of (Windward pressure, Leeward pressure )

Reduction Factor = 1.0, for h/d ≥ 5

Reduction Factor = 0.85, for h/d ≤ 1
Interpolation of Reduction Factor, for 1 ≤ h/d ≤ 5

CIVL426 by W.M.Quach, 2008

Table III.B.8 – Net pressure coefficient δp
for canopy roofs

CIVL426 by W.M.Quach, 2008

Table III.B.8:
Net pressure
coefficient
δp for
canopy
roofs

CIVL426 by W.M.Quach, 2008

Table III.B.9 – Friction coefficient δfr

CIVL426 by W.M.Quach, 2008

Figure III.B.3 – Reference Area ( Afr) for
Friction

CIVL426 by W.M.Quach, 2008

 Article 20° and Appendix C of Annex 3 –
Dynamic response due to wind action

1. Dynamic Non-sensitive Building Structures

with na > 1 Hz : Æ Cdyn = 1.0 ;
2. Dynamic Sensitive Building Structures with
0.2 Hz < na < 1 Hz.: Æ Cdyn > 1.0 (see
Appendix C of Annex 3).
3. Dynamic Sensitive Building Structures with
na < 0.2 Hz.: Æ (The structure is out of the
scope of this code. Use relevant
investigation or wind tunnel tesing).
Note: na = the first mode fundamental frequency of
the structure
CIVL426 by W.M.Quach, 2008
Dynamic Sensibility – An Alterative
simplified method

CIVL426 by W.M.Quach, 2008

 Appendix C of Annex 3 – Dynamic
response coefficient Cdyn
According to AS/NZS 1170.2.2002.
For Dynamic Sensitive Building Structures with
0.2 Hz < na < 1 Hz ,

Reserving more
Only for alongwind elaborated analytical
components methodologies for
the other cases

CIVL426 by W.M.Quach, 2008

Appendix C of Annex 3 – Dynamic
response coefficient Cdyn

CIVL426 by W.M.Quach, 2008

Appendix C of Annex 3 – Dynamic
response coefficient Cdyn

CIVL426 by W.M.Quach, 2008

Appendix C of Annex 3 – Dynamic
response coefficient Cdyn

CIVL426 by W.M.Quach, 2008

Appendix C of Annex 3 – Dynamic
response coefficient Cdyn

CIVL426 by W.M.Quach, 2008

Appendix C of Annex 3 – Dynamic
response coefficient Cdyn

CIVL426 by W.M.Quach, 2008