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 Radziriadz@hmetro.coi: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 Ibrahimya_t@hmetro.com.my

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 SAFURIKAMARUDINam@hmetro.com.rny

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