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The Usage of Malaysian Standard of
MS1553:2002 Code of Practice on Wind Loading for Building Structure
PAT409 HIGHRISE BUILDING
Contents
Part 1 : Introduction - Wind Loads
Part 2 : MS1553; 2002, Code of
Practice on Wind Loading for
Building Structures + worked eg.
Part 3 : Examples
PART : 1
Introduction
Failure because of wind loading : Ferrybridge Cooling Tower, UK (1965)
• Design wind pressures at
the top of the tower were
19% lower than they should
have been.
Natural Disaster due to Wind Storm
• According to International Disaster Database(2004), wind storm are listed top 10 naturaldisaster affected Malaysia.
• 26 December 1996, Sabah - killed 270 people in.• 12 February 1999, Kuala Lumpur- Several houses
and buildings structures has damaged and destroyed by wind. Loses are estimated morethan RM 250,000.
• 16 August 2004, Bukit Mertajam, Seberang Perai-Twenty vehicles damage because roof apartmentfalling down
• 28 August, Penang- Windstorm caused serious damaged to 25 houses but also injured people.
• 6 November 2004, wind storm has induced 40000 people affected in east cost of PeninsularMalaysia
• 19 February 2005, Sungai Siput. Perak -38numbers of house damaged due to windstorm
WIND DAMAGES IN MALAYSIA
Jumaat8 Disember 2006BERITA HARIAN - 08 DIS. 2006
BH PILIH 87 A 8 (em1
180 rumahrosakdipukul ributOleh Rosdalilah Zahari
I bat ribut yang melanda selama
POH: Sebanyak 180buah rumahmengalami kerosakan teruk aki
kira-kira sejam di sekitar Jelapang disini, petang kelmarin.
Ahli Dewan Undangan Negeri(Adun) Manjoi, Datuk Nadzri Ismail,berkata pihaknya akan memberi bantuan kepada kira-kira BOOpenghunirumah terbabit yang akan ditempatkan di Dewan Orang Ramai TamanMeru2B.
Pada masa sama, kerajaan negerimemberikan bantuan makanan danminuman selama tiga hari selain menyediakan peruntukan menggantikan atap rumah.
"Bagaimanapun, mangsa lebih cenderung tinggal di rumah saudara mara atau terus tinggal di rumah sendiri iaitu di bahagian rumah yangtidak rosak. Ini untuk mengelakkankecurian berlaku di rumah mereka,"katanya pada sidang media di sini,semalam.
Beliau berkata, selain bumbungyang diterbangkan angin, beberaparumah turut mengalami kerosakanperalatan elektrik akibat terkena hujan dan runluhan pokok besar dikawasan itu.
Katanya , tiada penduduk cederadalam kejadian yang melanda beberapa taman perumahan di sekitarTaman Meru , Bandar Meru Raya danJelapang itu manakala nilai kerugian belum ditaksir.
Kawasan berkenaan sebelum inisering diland!i angin kencang danribut kerana terletak di laluan anginlintang.
Beliau berharap mangsa ribut bersabar kerana kerajaan sedang memantau keadaan untuk membantumereka .
Katanya, kerajaan sedang meneliti
ANGKARA TAUFAN: Penduduk membaiki sebahagian darlpada 180 rumah yang rosak di Jelapang, semalam.
kesan bencana itu untuk tindakan lipina minggu lalu dilaporkan sedang Jabatan berkenaan meramalkalanjut. · menghala ke Malaysia dengan Ja angin kencang itu berdasarkan ke:
Ribut yang berlaku kelmarin dan batan Meteorologi meramalkan hu daan laluan Taufan Durian yang bedikatakan ' tempias' daripada Tau jan lebat dan angin kencang dijangka gerak dari tenggara Vietnam ke arafan Durian dianggap terburuk da berlaku di kebanyakan tempat di Ke barat daya dengan kelajuan 24 km,lam tempoh lebih 10tahun.
Taufan Durian yang melanda Fi- lis mulai semalam dan hari ini.lantan , Terengganu, Kedah dan Per merentasi Teluk Thailand seteru
nya menghala ke Malaysia.
2 J lsnln, 16 Jul i 2007 SetempatIM PIUH2N 16 (1-11111)
»Oleh Rladz [email protected]:n.my
SUNGA! PETANI: "Saya
hanya menyedari kejadian itu apabila dia menangis akibat terkejut
selepas beberapa zink jatuhhampir tempat tidurnya.
"Saya bersyukur kerana diatidak cedera," kata ZaitonAbd Manaf, ibu kepada NorAlia Natasha Ismail, 5, antaramangsa kejadian ribut diKampung Sungai Deraka,Kota Kuala Muda, dekat sini,awal pagi semalam .
Dalam kejadian ribut sertahujan lebat jam 7.30 pagi itu,sekurang-kurangnya tujuh rumah rosak termasuk empat darinya rosak teruk. Zaiton, 50, berkata , ketikakejadian anaknya itu masih tidur dalam kelambu di bahagian depan rumahnya . "Saya tidak mampu berbuatapa apa selain mencapai Aliayang menangis akibat terkejut dengan kejadian itu,"katanya ketika ditemui di rumahnya semalam.
Bagaimanapun, semua 11penghuni rumah itu terselamat.
Seorang mangsa ribut, Fariza Ahmad, 43, berkata kejadian ribut yang berlakubegitu pantas kira-kira 10minit itu menerbangkanbumbung rumah ketika diabersama anaknya, HazariMohd Khalid, 19, sedangbersarapan.
"Say rdengar bunyi meletup(li bumbung dan dalam sekelip mata bumbungrumah kami diterbangkanribut dan jatuh hampir 100meter dari rumah," katanya .
Dia bersyukur kerana ke-
Nyaris ced·eraditimpa zinkTujuh rumah rosakteruk dipukul ribut, 10bumbungsekolah tercabut
jadian, dua inaknya tiada dirumah kerana ke sekolah.Sementara itu, dalam kejadian sama, 10 keping bumbung bangunan Sekolah Kebangsaan (SK) Haji Sulaimanturut diterbangkan ribut.
Bagaimanapun, tiada yangtercedera kerana ketika ke-
jadian semua pelajar sedangberada di kantin sekolah.
Sementara itu, Ahli DewanUndangan Negeri (Adun)kawasan Pantai Merdeka,Datuk Dr Shuaib Saiden ketika ditemui berkata, mangsaribut akan diberi bantuan .
Dia menasihatkan mangsa
terbabit supaya membuat I:poran polis bagi memudalkan pihak Jabatan KebajikaMasyarakat (JKM) membebantuan.
"Bantuan memperbaiki korosakan bumbung akan dusahakan segera bagi memidahkan mangsa," katanya.
10 keping bumbungbangunan Sekolah
Kebang&aan (SK) Hajl·Sulalman turut
dlterbangkan ribut.
Metro Setempat
Bumbung diterbang ributBeberapa rumah, pusatbeli-belah di Putrajaya rosakdilanda ribut, hujan lebatsebabkan banjir kilat»Oleh Hayati [email protected]
PUTRAJAYA: Hujan le
bat disertai ribut petirlebih satu jam, petangsemalam menyebabkan
beberapa rumah kediamandan pusat beli-belah terkemuka di sini, digenangi airakibat bumbung yang diterbangkan angin.
Kejadian yang bermula kira-kira jam 3.30 petang ituturut menyebabkan banjirkilat di sekitar Putrajaya, selain beberapa batang pokoktumbang serta dua kenderaan termasuk sebuah motosikal dan kereta rosak akibat ditimpa atap gentingyang jatuh dari pangsapuri.
Bagaimanapun, tiada kecederaan dilaporkan.
Antara rumah yang mengalami kerosakan teruk ialah kediaman di tingkat paling atasBlok B, Pangsapuri Putra Damai, di Presint 11 dan Pangsapuri Fasa 4A, Presint 8.
Pembantu am di Kementerian Kemajuan Luar Bandar dan Wtlayah, NorainArshad, 22, yang tinggal ditingkat 16, Blok B, Pangsapuri Putra Damai berkata,kejadian itu disedari sebaikpulang ke rumah kira-kirajam 5.30 petang.
"Ketika tiba di rumah, sayamelihat rakan sedang mengeringkan air yang bertakung di ruang tamu rurnah.Apabila memasuki bilik sayadapati siling sudah berlubangmanakala seluruh ruang biliktermasuk tilam dan pakaianbasah.
"Malah, kepingan atap genting bertaburan dalam bilik. Ini kali keenam kejadian seumpama ini berlaku sejakkami tinggal di sini, tetapi kali ini lebih teruk sehingga menyebabkan selurµh rumah basah," katanya ketikaditemui di sini, semalam. Norain yang menyewa rumah itu sejak setahun lalubersama enam lagi rakan, su-
SITI RAHAYU...agak cemas
dah memaklumkan mengenai kebocoran siling itu kepada tuan rumah, namun pemilik rumah itu memaklumkan dia sudah memberitahupihak penyelenggaraan. "Tetapi sehingga kini, tiadatindakan segera diambil untukmengatasi masalah itu menyebabkan kami risau setiapkali hujan lebat," katanya.
Sementara itu, Siti RahayuAbu Bakar, 38, yang tinggaldi tingkat enam, Blok B,
TERCABUT...sebahaglan atap Pangsapuri Blok B Preslnt 8 diterbangkan rlbut,
semalam.
Pangsapuri Presint 8, berkataketika mendapati hujan lebatberserta angin kencang, diaterus menghubungi anaknyayang tinggal di rumah supaya
menutup semua tingkap danpintu.
"Panggilan pertama saya dijawab, tetapi selepas seketika saya menghubungi semula
bagi memastikan keselamatannya, namun panggilan telefon saya tidak terjawab menyebabkan saya agak cemaseketika," katanya.
Setempat 20 April 2008 7 IIM PIUH 7A20 (e-!ftlll
BumbungtercabutEnam rumahrosakdipukul ributkuat
»Laporan dan foto [email protected]
BALING: "Saya terns
melaungkan azan kerana tidak tahu apa lagipatut saya buat selepas
seluruh rumah bergegar danbumbung tercabut diterbangkan angin disebabkanribut terlalu kuat," kata RosliDin.
Rosli, 45, antara pemilikenam rum ah yang rosak akibat kejadian ribu t di Kampung Padan g Cik Mas, Mukim Pulai, dekat sini, kira-kira jam 7 malam kelmarin.
Menurutnya, ketika keja-
dian dia menikmati minumpetang bersama anaknya didapur dan mereka merancang hendak ke masjid bagimenunaikan solat Maghrib.
"Tiba-tiba saya nampakangin putih berpusing-pusing masuk ke ruang tamurumah dan dalam sekelipmata atap rumah diterbangkan. Saya sempat memelukanak saya selepas bumbungditerbangkan angin sejauh 20meter.
"Kami kemudian berlindung di ruang dapur keranabimb ang rumah runtuh danketika itu saya melaungkanazan ," katanya sembil memberitah.u , hujan lebat berterusan kira-kira kira-kira
30 min it.Rosli berkata , akibat ribut
itu pihaknya mengalami kerugian kira-ki ra RMS,000berikutan banyak peralatanrumahnya rosak.
Seorang lagi penduduk,Mohd Nazir Samah, 41, berkata ketika kejadian itu diapergi menziarahi isterinya dirumah mentuanya di Sik, Kedah.
"Ketika kejadian , hanyadua anak saya di rumah iaituMohd Hafiz, 14, dan Mohamad, 7.
"Mujur anak saya selamatwalaupun sebahagian rumahsaya rosak teruk akibat dihempap pokok macang. Semua barang dalam rumah
rosak kerana dibasahi air,"katanya.
Kejadian ribut itu juga menyebabkan beberapa pokoktumbang dan menghalang jalan utama untuk ke kampungberkenaan.
Bagaimanapun , denganbantuan Tenaga NasionalBerhad (TNB) Baling, usahamemotong pendawaian elektrik serta membersihkan pokok yang tumbang merintangi jalan dijalankan.
Sementara itu, AnggotaDewan Undangan Negeri(Adun) Bayu, Azme Che
Hussain, yang melawatmangsa meminta kerajaanneger i menyalurkan bantuandengan segera. BAIKI... mangsa menunjukkan rumah yang rosak.
Taman Murni 10 Ogos 2009
Strong Wind Events in Malaysia
Name
Matric
no. Site, State Date Time Wind Speed Station
Peninsular Malaysia
1 Alvin Leong Chee Wei 91846
2 Ang Jin Leong 91847
3 Teh Boon Koon 91944
4 Ng Woei Seng 91914
5 Bong Sell Feng 91851
6 Chan Wei Chuang 91852
7 Tou Yok San 91948
Kuala Perlis , Perlis 8-Oct-08 8.00 pm. Chuping
Sik, Kedah 28-Mar-09 Evening Alor Setar Station
Alor Setar, Kedah 25-Mar-09 - 79.92km/hr Alor Setar Station
Batu Lanchang, Penang 4-Apr-05 4.30 pm Bayan Lepas
Sungai Dua, Penang 20-Jun-07 1.44 pm 79.636 km/hr Bayan Lepas
Taiping, Perak 14-Aug-09 5.00 pm. Hospital Taiping
Putra Jaya , Selangor 4-Apr-08 3.30 pm. Subang
8 Chen Siew Siew 91855
Kampung Malaysia Raya, Kuala
Lumpur 28-Nov-09 4.15pm. 15.9 m/s Subang
9 Eugene Lim
10 Gan Khai Sian
91866 Seremban, Negeri Sembilan 1-Jan-10 5.30 am. Hospital Seremban
91870 Kota Melaka, Melaka 1-May-07 - Melaka
11 Saw Hooi Yee 91930 Parit Jawa, Muar , Johor 21-Oct-09 1.45 am 48.6km/hr Senai
12 Hew Ting Hui 91874 Johor Bahru, Johor 19-Jul-07 11.15 am. Mersing
13 Khor Wei Huat 91879 Rompin, Pahang 28-Sep-09 4.00pm. Muadzam shah
14 Ng Lye Khong 91912 Kota Bharu, Kelantan 2-Oct-09 - Kota Bharu
15 Yeong Ngai Hung 91951 Kota Bharu, Kelantan 22-Nov-09 - Kota Bharu
16 Leong Chung Sum 91885 Kota Bharu, Kelantan 30-Sep-09 3.30 pm. Kota Bharu
Kuala Terengganu Airport
Station17 Seet Khing Liong 91931 Besut, Terengganu 24-Apr-09 5.00pm. 52.56km/hr
18 Kuan Kae Liang 91882 Kuala Terengganu , Terengganu 21-Nov-09 Noon Kuala Terengganu
East Malaysia
19 Tan Yik Ping 91942 Tawau, Sabah 24-Nov-07 - 50km/hr Tawau
20 Lee Jun Yuan 91883 Lahad Datu, Sabah 19-May-09 Night Tawau
21 Ong Yee Chien 91926 Papar, Labuan 28-Sep - 60km/hr Labuan
22 Teh Koon Teik 91945 Kapit, Sarawak 21-Jun-09 7.30 pm. Kuching
23 Lee Khoon Jeng 91884 Kuching, Sarawak 15-Aug-09 - 40.7km/hr Kuching
CHARACTERISTICS OF THUNDERSTORMTS Event at 17.30 on 11th April 2003
25 Var iab le
W IND A
Wind Spe e d (m/s ) ve rs u s Time
Win
dS
peed
(m/s
)
W IND B
20
15
10
5
0Minute
Hour
Da y
Loads
• Two main types
dead loads - self-weight, fixed elements
live loads - occupancy, wind
Loads (cont.)
• The building materials impose deadloads (fixed, vertical)
• The occupants and contentsimpose live loads (variable, mostlyvertical)
• Wind and earthquake impose liveloads (variable, mostly horizontal)
Wind loads
• Both Pressure and Suction
• Always important for tallbuildings
• But also important for lowbuildings - bracing
Wind loads on Buildings• Pressure on the windward face
• Suction on other faces
• Suction on lowpitched roofs - <300
• Buildings need bracing and tying-down
• Wind can come from any direction
wind
Wind Loads on Buildings(cont1.)
may need to
weigh down roof
Factors in Wind Speeds
• General wind speed in the region ( 8 – 20 m/s)
– (pressure varies with square of the speed)
• Local topography affects wind patterns
• Wind speed increases with altitude
• Wind speed decreases with terrain roughness
Very exposed
More sheltered
Wind
Factors in Wind Loads(cont.)
• Shelter from anything permanent will reduceloads
• Shape of building affects loads
– Boxy vs streamlined
Curved
shapes
would need
special
analysis
Sheltered
by buildings
Menara KOMTAR, Penang
Wind Loads on Elements
• Min wind pressure in MS1553 =0.65kPa
• Wind Force = Multiply by the areaexposed to wind
Structural Response
Deflection
All structures experience stress and undergo a limited amount of deflection when subjected toloading. A structure’s deflection under the dead load is only in the vertical direction withno lateral deflection at all. vertical deflection can be in the form of bending in thehorizontal spanning members such as beams and slabs and shortening of vertical loadbearing members such as columns and walls.
When the live load is added to the structure, the produced stresses and the resulted deflections
become much higher. The horizontal loads such as wind load and earthquake loads canproduce large lateral displacement of the overall structure, which in turn will result indeformation of structural members locally.
Excessive deflections are undesirable in a building because they can result in damage of thebuilding components and create structural problems. Deflection limits imposed by variousbuilding codes. These limits are based on the load types and the structural member.
Overall Structural Stability
If the structure or its foundation is not properly designed or constructed the overall structuralsystem can lose balance and fail. This failure can result in sliding, overturning or torsion.
1. Sliding
2. Overturning
3. Torsion or Twisting
6
LIMITATIONS OF CODES
•Not consider tornadoes and typhoons
•Covers only building +- 200m high
•Structures with roof spans less than
100m
•Not off-shore structures, bridges and
transmission towers
3
Wind tunneltesting
Current technology is based on simulating
boundary-layer (synoptic) wind profiles
Modelled building + surrounding structures +
topography are geometrically similar to full
scale
Instrumentations are consistent with the
required measurement
Less effect of terrain and topography
Wind tunnel testing - Monash 450kW wind tunnel
UBN Complex
Kuala Lumpur 1982
aeroelastic test
Wind tunnel testing - Monash 450kW wind tunnel
Menara MPPJ
Petaling Jaya 1983
aeroelastic test,
cladding pressure
Menara MPPJ
Wind tunnel testing - Monash 450kW wind tunnel
Menara Safuan
Kuala Lumpur 1984
aeroelastic test,
cladding pressure,
environmental wind study
Wind tunnel testing - Monash 1MW wind tunnel
Penang Stadium
1997-98
aeroelastic,
pressure study with
correlations (effective static
wind loads)
Wind tunnel testing - Monash 450kW wind tunnel
Batang Baram Bridge
Sarawak
1997
section model test
Wind tunnel testing - Monash 1MW wind tunnel
Batang Baram Bridge
Sarawak
1997
aeroelastic model of full
bridge and erection stages
Wind tunnel testing - Monash 450kW wind tunnel
Universiti Teknologi
Petronas
Tronoh 1999
cladding pressure,
area-averaged pressures
Wind Tunnel testing at NUS
Menara Taming Sari
Melaka, 2003
cladding pressure,
aeroelastic
• Not all extreme winds are boundary-layer winds
• Thunderstorm downburst winds are dominant contributor to extreme winds in equatorial climates near ground level
• Synoptic winds may be dominant at greater heights - tall buildings
• Storm types must be separated in extreme value analysis
• Full-scale measurements of vertical and horizontal profiles in downbursts are required
• Potential for laboratory and numerical simulation of flow over buildings, topography
Summary
Introduction
MS 1553:2002
•Malaysia has developed their code of practice MS
1553:2002 on wind loading for building structure .
•MS: 1553:2002 has been base from Australia Standard
AS 1170.2 based on similarity of wind climate (Sundaraj,
2002).
•The code was developed using 23 meteorological all over
Malaysia and the basic wind speed for Malaysia was
established.
•In year 2002 under research grant of wind profile study,
three ultrasonic wind sensors were installed in Seberang
Jaya Telecommunication Tower
Ultrasonic Wind Sensor
C
B
UWS Position at Seberang Jaya
TelecommunicationTower
A
level A B C
Height (m) 45.72 75.28 97.23
Telecom Tower
Seberang Jaya
Telecom Tower -Seberang Jaya
Wind Loads
• The most common lateral load consideredin building design is wind load.
• Wind load vary in intensity depending onthe building's geographic location, elevation, degree of exposure, relationship to nearby structures, building height, sizeand shape.
• The dynamic effect of wind load is usuallyanalyzed as an equivalent static load inmost small and moderate-sized buildings
Wind Loads
• Wind against a building may buildsup positive and negative pressures on the windward and leeward sidesof the structure. Winds can applyloads to structures from unexpecteddirections.
• Wind loads have become particularlysignificant because of the increasingnumber of high-rise buildings.
PART : 2
Design Wind Load
Factors influenced Wind Load
• Basically all codes and standards included factor to calculate the wind pressure on building.
• The basic factor to calculate wind pressure to building are depending on the building s geographic location, elevation, degree of exposure, relationship to nearby structures, building height, size and shape.
• There are well known as:
'
1. Type of terrain ground,
2. Wind direction factor3. Shielding factor
5. Height above
6. Hill shape factor7. Aerodynamic factor
4. Dynamic Response Factor
An Overview of Design Codes
CodeDesign Wind Dynamic
Building Pressure/forceSpeed Pressure
ISO 4354 V q ref = 0.5 ρV2w =
(q )(C )(C )(C )ref exp fig dyn
ENV 1991-
2-4Vref = CdirCtemCALTCref,o q ref = 0.5 ρv2
ref w = (q ref)(ce)(z)(cpe)
ASCE 7-2002 Vq z =
0.5 ρKzKztKdV2I
p = q (GC )p
AIJ 1996 UH =UOETEER qH = 0.5ρU2H
wf = qHCfGfA
PE = CpeKeKlKpqzAS 1170.2-1989 Vz = VMd(Mz.cat)MsMtMi qz = 0.5 ρV2 z
BS 6399:
Part 2Ve = VbSaSdSsSpSb qs = 0.5ρVe
2 Ps = qs CpeCa
MS 1553:2002Vdes=
Vs Md(Mz.cat)MsMhIq 0.5ρV 2 P = q C C
s = des s s fig dyn
REFERENCES
1. Architectural Institute of Japan (1996) ‘’Recommendation for Loads on
Buildings’’, AIJ.
2. American Society of Civil Engineers (1998), ‘’Minimum Design Loads for
building and others structures’’. ASCE 7-98.
3. British Standard Institution. Loadings for building (1995) ‘’Code of practice for
wind loads’’, BS 6399 Part 2.
4. C.E.N (European Committee for Standardization) Eurocode 1 (1994) ‘’Basis of
Design and Actions on Structures – Part 2-4: Actions on Structures - Wind
Action’’ ENV 1991-2-4.
5. International Standards Organization (1997) ‘’ Wind Action on Structures’’, ISO
4354.
6. Malaysia Standard (2002) ‘’Code of Practice On Wind Loading For Building
Structure’’, MS 1553:2002 Department of Standards Malaysia.
7. National Research Council of Canada (NRCC) (1996). ‘’ User’s Guide - Structural
Commentaries’’ NBCC 1995 Part 4.
8. Standard Australia (1989) ‘’ Minimum Design Load on Structure Part 2: Wind
Load’’AS 1170.2-98.
Modification on Factor
• From modification factors that have been highlighted before, there arethree major concern why the factor areincluded
1. Wind climate2. Topography Condition (e.g. Hill Slope)3. Geometry/Shape of Building
• Only factor deal with climate differentfrom one country to another country.Other factor are almost same
Terrain height multiplier
• From the various codes of practice, the modification factor that deal with climate is terrain height multiplier.
• It is known and symbol as shown as below:SYMBOL FACTORCODE
ISO 4354 Cexp Exposure coefficient
ENV 1991-2-4 CALT **
ASCE 7-2002 KzExposure terrain
coefficient
AIJ 1996 ET **
AS 1170.2-1989 Mz.catTerrain Height
Multiplier
BS 6399: Part 2 Sb Terrain Building Factor
MS 1553:2002 Mz.cat
Terrain Height Multiplier
Basic Wind Speed (Vs)
• Definition: Maximum wind speed will occur one in a recurrent interval year (XT)
• X = wind speed , T =Year
• Always T is taken as 50 year and 100 year
• Vs is measured at 10 m height from ground level
• Vs is use as a reference wind that will be consider in design load to structure
Design Wind Pressure
• According to MS 1553:2002
p = (0.5ρair) Vdes 2(Cfig)(Cdyn) in Pa …(2)
where Vdes=Vsite x I
and Vsit = Vs(Md)(Mz,cat)(Ms)(Mh)
I = important factor (Table 3.2 pg 21)
Vs = Basic Wind Speed ( Table 3.1 pg 19 or map Fig 3.1 pg 20)
Md = Direction Multiplier (Md = 1)
Mz,cat = Terrain Height Multiplier ( Table 4.1 pg 23)
Ms = Shielding Multiplier (Table 4.3 pg 25)
Mh = Hill shape Multiplier ( Equations either a), b) or c) )
Mz,cat = Terrain Height Multiplier
• Definition = multiplier than giving wind speed at variation of height base on wind speed at reference (Vs,10 m) for different terrain category
• Table 4.4, pg 23 MS1553
Category Description
1 Exposed open terrain with few or no obstruction
including water surface and sea surface
2 Open terrain, with few well scattered obstruction
having height from 1.5m – 10 m
3 Terrain with numerous closely spaced obstruction
3.0m- 5.0m such as suburban areas
4 Terrain with numerous large, high (10m to 30m high)
and closely spaced obstruction such as large city
centre and well developed industrial complexes
1(a)
Ope.n country·
soo.
400
300
200
0I .
I
Woadland orSub,urban
City centre
z,
Minimum
Design Wind Pressure 0.65 kPa
(Cl 2.4.2 pg 15)
PART : 3
Examples