Tutorial work - tutorial problems, handouts PDF

Preview

Summary

tutorial problems, handouts...

Description

EXAMPLE QUESTION: DETERMINE WIND ACTIONS FOR A MULTI-STOREY SCHOOL BUILDING

Location: Wollongong Terrain: Distance of terrain category 4= 500 m; afterward terrain category 3 for 500 m and then terrain category 2. Topography: The building is located on a 20m high hill; horizontal distance upwind to the half hill is 100 m; upwind distance of the building from the crest is 5m. Shielding: Number of shielding building within 450 radius is 20 with average height= 50 m and average breadth= 30 m Dimension: Height of the building = 24 m; Plan dimension= 30 m x 22 m Building orientation: Major axis East-West Building construction: Reinforced concrete Calculate the wind forces on windward and leeward walls for the wind from West

Solution: 4 steps of calculation of wind speed (I) Determine site wind speed (II) Determine design wind speed (III) Determine design wind pressure (IV) Calculate wind action

(I) DETERMINE SITE WIND SPEED Vsit,β=VRMd(Mzcat, Ms, Mt)

[Equation 2.2]

Determine VR Consider the building is of Importance category 3 Average recurrence interval for serviceability limit state= Table 3.1 and 3.3] Average recurrence interval for ultimate limit state= 3.1 and 3.3]

years [AS1170.0- 2002

years [AS1170.0- 2002 Table

Wind Region=A2 [Figure 3.1 AS/NZS 1170.2-2002] for Wollongong VR= V25=______________ m/s (Serviceability Limit State) [Table 3.1] VR=V1000=______________ m/s (Ultimate Limit State) [Table 3.1]

Determine Md Wind direction Multiplier Md= __________[Table 3.2] [Region A2 for wind from West] Determine Terrain/Height Multiplier (Mz,cat) (Building height is less than 25m; hence, a single value of design wind pressure would be conservative. So, Mz,cat needs to be determined for the total height of the building) Height of the building= 24 m Mzcat for terrain categories: (Table 4.1 (A)] Mz,4= ______ Mz,3= ______ Mz,2= ______ Averaging distance= 1000 m [Table 4.2(A)] Roughness length for the terrain categories [Table 4.2(B)] For terrain category 2= For terrain category 3= For terrain category 4= Lag distance 1 (TC4 to TC3) 1.25

⎡ z ⎤ xi = z 0,r ⎢ ⎥ ⎢⎣0.3z 0,r ⎥⎦ x1=_________________ Lag distance 2 (TC3 to TC2) x2=_________________ Hence, xt4= ______________ xt3=_______________ xt2= _______________ Mz,cat= (Mz4*xt4+Mz3*xt3+Mz2*xt2)/Averaging distance =_______ =________ Determine Shielding Multiplier (Ms) Average upwind gradient Mlee [Section 4.4] Height of the hill H= 20 m Horizontal distance upwind to half height below the crest Lu= 100 m Distance of the building from the crest x= 5m Reference height z= 24 m (wind action is calculated at the roof height)

H/(2Lu)= 20/ (20*100)=0.1> 0.05

[Section 4.4.2]

x⎤ ⎡ ⎤⎡ H M h = 1+ ⎢ ⎢1 − ⎥ ⎥ ⎣ 3.5( z + L1 ) ⎦ ⎣ L2 ⎦ L1=0.36Lu>0.4H =__________ L2=4L1 =__________ Mh=___________ Mlee= 1.0 Hence, Mt=__________ Calculation of site wind speed Vsit,β= Vsit,β=

[Serviceability Limit Sate] [Ultimate Limit State]

(II) DETERMINE DESIGN WIND SPEED (Vdesθ) Vdesθ= ________ [Serviceability Limit State]

[Section 2.3]

Vdesθ= _________ [Ultimate Limit State]

[Section 2.3]

(III) DETERMINE DESIGN WIND PRESSURE p = 0.5 ρair [Vdes , θ ]2 C fig C dyn

[Equation 2.4(2)]

ρair= 1.2 kg/m3 Cfig=? Cdyn=? Determine aerodynamic shape factor Cfig Cfig=Cp,e Ka Kc Kl Kp (for external pressure) [Equation 5.2(1)] Cfig= Cp,i Kc (for internal pressure) [Equation 5.2(2)] Determine Internal Pressure Coefficient (Cp,i) The building is effectively sealed and having non-opening windows Cp,i= - 0.2 or 0 (whichever is more severe for combined forces) [Table 5.1(A)] Determine External Pressure Coefficient (Cp,e) Windward wall: Wind speed is taken at roof height (z=h) and h...