PSZ 19:16 (Pind. 1/07)

DECLARATION OF THESIS / UNDERGRADUATE PROJECT PAPER AND COPYRIGHT

LEE SID HWAAuthor’s full name :

Date of birth : 26 / 10 / 1983

Title : FAILURE OF ROOF STRUCTUREDUE TO WIND LOAD

2007/2008Academic Session:

I declare that this thesis is classified as :

I acknowledged that Universiti Teknologi Malaysia reserves the right as follows:

1. The thesis is the property of Universiti Teknologi Malaysia.

2. The Library of Universiti Teknologi Malaysia has the right to make copies for the purposeof research only.

3. The Library has the right to make copies of the thesis for academic exchange.

Certified by :

SIGNATURE SIGNATURE OF SUPERVISOR

(NEW IC NO. /PASSPORT NO.) NAME OF SUPERVISOR

Date : Date :

NOTES : * If the thesis is CONFIDENTAL or RESTRICTED, please attach with the letter fromthe organization with period and reasons for confidentiality or restriction.

UNIVERSITI TEKNOLOGI MALAYSIA

√

CONFIDENTIAL (Contains confidential information under the Official Secret

Act 1972)*

RESTRICTED (Contains restricted information as specified by the

organization where research was done)*

OPEN ACCESS I agree that my thesis to be published as online open access

(full text)

831026-05-5155

9 APRIL 2008

P.M. DR. RAMLI ABDULLAH

“I hereby declare that I have read this thesis and in my

opinion this thesis is sufficient in terms of scope and quality for the

award of the Master of Civil Engineering (Civil – Structure)”

Signature : …………………………………...

Name of Supervisor : PM. DR. RAMLI ABDULLAH

Date : …………………………………….

FAILURE OF ROOF STRUCTURE DUE TO WIND LOAD

LEE SID HWA

A project report submitted in partial fulfilment of the

requirements for the award of the degree of

Master of Civil engineering (Civil – Structure)

Faculty of Civil Engineering

Universiti Teknologi Malaysia

APRIL 2008

ii

I declare that this project report entitled “Failure of Roof Structure Due to Wind Load”

is the result of my own research except as citied in the references. The project report has

not been accepted for any degree and is not concurrently submitted in candidature of

any other degree.

Signature : …………………………………...

Name : LEE SID HWA

Date : ……………………………………

iv

ACKNOWLEDGMENT

First of all, I would like to thank my supervisor, Prof. Madya. Dr. Ramli

Abdullah, who had given guidance for my work and came up with some inspiring

suggestion, in the mean time, his patience and immeasurable contribution is the key to

generate this project. If Dr. Ramli didn’t spent his own valuable time to listen to my

problem and give advices, I would have not completing my project thesis.

Next, I would like to acknowledgement my thanks to the laboratory staff

especially Encik Zailani for his cooperation, hardwork and endless patience in my

laboratory testing. Their aid reduced my work load and also speed up the progress.

Last but not the least, I would like to express my deep appreciation to my family,

and people that I don’t mentioned their name for their support, suggestion and also

opinion.

v

ABSTRACT

There are reported roof failure due to uplifting of the roof structures or roof

sheeting during rainstorm has been causing damages to the buildings. Generally, failure

occurred at the two points, either at the roof truss’s sheeting or at the truss to roof beam

connections. There are 2 types of structure are to be analyzed; the different of these two

building will be the buildings dimension, meaning that one is a single storey houses and

other is a 20 storey apartment. The roof structure’s data is extracted from the reported

cases for simulation purposes. For a more conservative result, the wind speed is taken as

40 m/s. Due to different aspect for this 2 type of structure, the wind-uplifting force will

be determined. The calculated resulting forces transferred at different connection points

were compared with the experimental result obtained from laboratory testing. The result

of this, is that the connection of both houses and apartment is safe under the wind speed

of 40m/s. However, this happen when the proper used of selected material plus all the

material is in well condition. To improve the study of this project, the larger scale

testing like wind tunnel can provide the more accurate result due to the integrity of the

roof structure.

vi

ABSTRAK

Seperti yang dicatat dalam bahan bacaan seperti suratkhabar, kes-kes kepingan

atap yang dicabut oleh angin kuat dalam hujan lebat menyababkan kegagalan struktur

bumbung. Sebenarnya menurut kajian yang telah dilakukan, biasanya kegagalan

struktur bumbung berlaku di 2 tempat, iaitu di tempat sambungan pada komponen-

komponen kayu dan paku atau kepingan zink yang dipaku pada gulung gulung. Oleh itu,

2 jenis struktur akan dikaji untuk menyelidik bahawa faktor-faktor ketinggian, saiz, dan

lokasi akan menjadi sebab kegagalan struktur bumbung. Perhubungan antara bangunan

apartment yang setinggi 20 tingkat dan rumah biasa setinggi satu tingkat. Untuk

mendapatkan bacaan yang lebih selamat, halaju angin adalah 40 m/s. Selepas pengiraan

untuk kapasiti pada setiap sambungan, kapasiti yand dikaji akan selamat dalam halaju

angin 40 m/s. Tetapi keputusan ini adalah benar jikalau semua komponen dalam

struktur adalah baik. Pada akhirnya, kajian ini mencadangkan penggunaan Wind Tunnel

untuk mendapatkan keputusan yang lebih memuaskan.

vii

TABLE OF CONTENTS

CHAPTER TITLE PAGE

DECLARATION ii

DEDICATION iii

ACKNOWLEDGMENT iv

ABSTRACT v

ABSTRAK vi

TABLE OF CONTENTS vii

LIST OF TABLES x

LIST OF FIGURES xi

1 INTRODUCTION 1

1.1 Introduction 1

1.2 Problem Statement 3

1.3 Objective of Research 4

1.4 Scope of Research 5

1.5 The Contribution of the Research 5

2 LITERATURE REVIEW 6

2.1 Metal Roof Sheeting 6

2.2 Timber Roof Structure 10

2.3 Wind Action 12

2.4 Wind Tunnel Experimental done 15

2.4.1 Global roof failure testing 16

viii

2.4.2 Sheathing panels 16

2.4.3 Effects of dominant openings 17

2.4.4 Roof venting 17

2.5 Roof Structure Element 18

2.6 Supporting Structures 20

3 METHODOLOGY 22

3.1 Research Programme 22

3.2 Weather data 23

3.3 Materials 25

3.3.1 Zinc Roof Sheeting 25

3.3.2 Timber (Wood) 26

3.3.3 Caped Nail and Washer 26

3.3.4 Suitable Nails Used 27

3.4 Pre-assumption Involved in Calculation 27

3.4.1 Low Rise Ordinary Houses ( 1- storey high ) 28

3.4.2 High Rise Apartment ( 20-storey high ) 31

3.5 Laboratory Testing Process 34

3.5.1 Connection between Zinc Roof Sheeting and Purlin 34

3.5.2 Connection between Purlin and Rafter 36

3.5.3 Connection between Rafter and Beam 41

4 TEST RESULTS 42

4.1 Introduction 42

4.2 Experimental Result 42

4.2.1 Experimental Result – Zinc Sheeting and Purlin 43

4.2.2 Experimental Result – Purlin and Rafter 45

4.2.3 Experimental Result – Rafter and Beam 46

ix

5 ANALYSIS AND DISCUSSION 50

5.1 Analysis 50

5.1.1 Required Nail Pulling Resisting Force 50

5.1.2 Comparing Experimental Result 51

5.2 Reverse Calculation 52

5.2.1 Single Storey House 52

5.2.2 20 Storey Apartment 53

5.2.3 Total Roof Structure Failure 54

5.3 Discussion 55

6 CONCLUSION AND RECOMMENDATION 57

6.1 Conclusion 57

6.2 Recommendation 58

REFERENCES & BIBLIOGRAPHY 59

APPENDICES 60

x

LIST OF TABLES

TABLE NO. TITLE PAGE

2.1: Types of metal roof sheeting and their properties 11

2.2: Roof systems materials consumed in homes 12

2.3: Maximum Bay Lengths of Rafters and Ceiling Ties(BS 5268 Table 3) 21

3.1: Weather data of Senai, Johor Bahru at January 2007 25

3.1(a): Legend of Table 3.1 26

3.2: Classification of timber due to strength 27

4.1: Failure load on the experimental testing – Zinc Sheeting and Purlin 44

4.2: Failure load on the experimental testing – Purlin and Rafter 46

4.3: Failure load on the experimental testing – Rafter and Beam 47

xi

LIST OF FIGURES

FIGURE NO. TITLE PAGE

1.1: Some of the common example roof failure 3

2.1: An example of outstation homestead of using zinc roof sheeting 8

2.2: Spandek Roof Sheeting 10

2.3: Custom Orb Roof Sheeting 10

2.4: Trimdek Roof Sheeting 10

2.5: Klip-Lok Roof Sheeting 10

2.6: Some of the common example truss shapes 12

2.7: Wind effect on a structure 13

2.8: Wind effect on a structure (2) 14

2.9: Wind action on corner of the roof structure 15

2.10: Winds create forces that attack the integrity of a structure inmultiple ways 16

2.11: Roof Structure parts and label 20

2.12: Battens (or Purlins) arrangement to avoid buckling 20

2.13: Truss and purlin spacing arrangement 20

2.14: Compression and Tension force along a normal truss 21

3.1: Flow chart of research planning 24

xii

LIST OF FIGURES (CON’T)

FIGURE NO. TITLE PAGE

3.2: Different condition of zinc roof sheeting 26

3.3: Caped nail and washer 27

3.4: Correct Nails Used (Simpson Ties Company) 28

3.5: Low Rise Structure Modeling Dimension 29

3.6: Wind Uplifting force for Pitched Roof (Low Rise) 31

3.7: High Rise Structure Modeling Dimension 32

3.8: Wind Uplifting force for Pitched Roof (High Rise) 34

3.9: Overall View of Roof Structure 35

3.10: Specimen Formed 36

3.11: Connection for the specimen 36

3.12: Testing Procedure using Rig Test 37

3.13: Testing specimens for connection between rafter and purlin 38

3.14: Setting of specimen 39

3.15: Specimen SP1 39

3.16: Specimen SP2 40

3.17: Isometric View and Side View of Connection between

Rafter and Beam 40

xiii

LIST OF FIGURES (CON’T)

FIGURE NO. TITLE PAGE

3.18: Specimen SP1 41

3.19: Specimen SP2 41

3.20: Connection between Rafter and Beam (Specimen SP1) 42

3.21: Connection between Rafter and Beam (Specimen SP2) 42

4.1: Testing result – Minor Rusted zinc sheeting teared off whilenail remains connected with the purlin 44

4.2: Testing result – Normal zinc sheeting tear off in the testing 45

4.3: Testing result – Rusted zinc sheeting tear off in the testing 45

4.4: Testing result for SP1– Purlin been pulling off 46

4.5: Testing result for SP2– Nail remain in rafter while the purlindetach from the connection 46

4.6: Testing result– Rafter is pulling up by testing machine 48

4.7: Testing result– The resistance of the nails has reached its limit 48

4.8: Testing result for SP1– Rafter detached from its position 49

4.9: Testing result for SP2– Nail being pulled out 49

4.10: Testing result for SP3– Nail being pulled out 50

CHAPTER 1

INTRODUCTION

1.1 Introduction

The roof is often the most expressive part of a house, symbolic of shelter and

functionally important for its capacity to protect the house from the element. However,

sometimes we tend to ignore the roof structure and put the concentration on the

structural member like beam and column. However, there is some real life report, wind

has cause of damage to buildings.

As printed on the newspaper or magazine, there is some cases that related to the

failure of roof structure due to the wind blow especially at rainstorm. Due to this

tragedy, there is something that can do to reduced or minimize through some study or

research to the wind load effect on the roof structure.

Wind damage in rainwater tends to occur progressively, usually starting with

damage to one of the components forming the building envelope (typically the roof,

cladding or unprotected windows), and which, if it progresses far enough, can lead to

failure of the complete structure. Even in cases where complete structural failure does

not occur failure of the building envelope often allows wind-driven rain to penetrate the

building leading to damage to the contents as well as loss of function. The loss of roof

sheeting is often attributed to the loss of roof sheeting is often attributed to either

inadequate nailing.

For roof pitches in the range commonly used for residential structures, wind

forces oriented normal to the ridge of the roof will cause wind uplifting forces.

Sometimes, there are weakness could extend the damage from wind; these weaknesses

involve the attachment of roofing to the roof sheathing. The sheathing attachment to the

roof framing, rake overhang details, and attachment of internal partitions to the external

walls contributes significantly to the extensive damage and to system failures.

For country that located at near the equator like Malaysia, the temperature is

high all year round (except at altitude). In many tropical regions people identify two

seasons: wet and dry. Unlike the foreign country, phenomenon like hurricane, snow fall

doesn’t happen on this area, but when the raining monsoon occurs: a large amount of

rainwater will fall, makes the withdrawal of water is crucial to avoid leaking or water

spill out. This is why pitched roof is so common compared to flat roof throughout the

country. Timber made roof truss has such advantages:

Lowest overall cost.

Fast to install.

Requires ordinary tools and

Doesn’t require skilled labour to install.

Virtually any roof and ceiling is possible.

Engineered product.

No job site waste.

1.2 Problem Statement

Throughout these years, there are some cases that related to the failure of roof

structure due to the wind blow especially at rainstorm. Due to this tragedy, there is

considered vital if there is a way that can do to reduced or minimize through some study

or research to the wind load effect on the roof structure.

For example, there are some real life cases like in the US, wind is the most

common, and the most costly cause of damage to buildings. Over a 7 year period from

1986 to 1993 extreme wind damage cost $41 billion in insured catastrophe losses as

compared to $6.8 billion for all other natural hazards combined. Reasons given for these

losses include: increased development in high risk areas, a lack of awareness of or

failure to follow recommended construction practices and the introduction of new and

unproven materials. Economic losses include repairing or replacing damaged homes

and their contents, while the loss of personal possessions and relocation during

reconstruction are common outcomes of residential damage.

Figure 1.1: Some of the common example of roof failure

Uplifting of the roof structures or roof sheeting during rainstorm has been

causing damages to the buildings. Generally, failure occurred at the two points, either at

the roof frame’s sheeting or at the frame to roof beam connections. There are 2 types of

structure are to be analyzed; the different of these two building will be the buildings

dimension and geographical locations.

Wind damage in rainwater tends to occur progressively, usually starting with

damage to one of the components forming the building envelope (typically the roof,

cladding or unprotected windows), and which, if it progresses far enough, can lead to

failure of the complete structure. Even in cases where complete structural failure does

not occur failure of the building envelope often allows wind-driven rain to penetrate the

building leading to damage to the contents as well as loss of function.

1.3 Objective of Research

Residential houses located in the countryside region (kampung houses) that were

relatively unsheltered from the full force of the storm incurred the decent damage. The

damage to these houses presented a unique opportunity to investigate the type and

extent of damage to this type of structure.

The objectives of this study are:

a) To investigate the roof structure elements and their tying down system

that frequently failed due to wind forces.

b) To determine the minimum wind speed required which causes the

uplifting of the roof of various construction and age.

c) To review the safety of the presently practiced construction of roof

structure.

1.4 Scope of Research

The scope of this research is to determine the ways to succeed the objectives.

One of these was the calculation of connection capacity. For those countryside housing

estates, it had presumed that all connection using nails rather than the metal connection

plate that used recently due to the age of the existing houses. And so, the weakness in

strength is the main focus of the research.

For the worst case environment performance, the experimental circumstances

practiced for extreme possibility, means the testing data based on the highest wind

speed that occurred before.

Moreover, this research will also determine the effect of the failure pattern of the

roof connection that due to strong wind blow condition. The connection part that

involved was connection between zinc roof sheeting and purlin; purlin and rafter; and

also the rafter and beam.

The result decided through the testing by laboratory equipment or through

certain calculation. And through that, the roof structures ultimate storm resistance can

be calculated. Data obtained through experiments will be analyzed and suggestions will

be given as necessary.

1.5 Significance of the Research

At the end of the research, the wind speed limit, ultimate resistance and effect

under severe weather will be provided, as an understanding and awareness to the

involved parties. With this, whenever the resident know about the current wind speed,

they will know the consequence of roof structure failure. To avoid the tragedy again,

repairing and strengthening of roof structure maybe needed.

CHAPTER 2

LITERATURE REVIEW

2.1 Metal Roof Sheeting

Metal roof sheeting is an old material, it has been made for about a century and

although it has had it's pro and cons in terms of popularity it has always been the best

roofing material for many people. A metal roof is a roofing system made from metal

pieces or tiles. They are components of the building envelope. Corrugated roof sheeting

or roofing iron has been around since the 1830's in England. It was and still is a

significant invention. The simple process or forming corrugations into a flat floppy

sheet of thin iron changed roofing for ever. Because of it's lightness and strength, easy

transportability, tons of it was shipped all over the world. Corrugated galvanised iron

describes the original product that was wrought iron plate coated with zinc and then roll

formed into corrugated sheets. However, the corrugated zinc roof sheeting now rare and

no longer manufactured in large amount. It has been replaced by some other else

material.

Figure 2.1: An example of outstation homestead of using zinc roof sheeting.

The main product that has replaced the old galvanised iron (zinc sheeting) is

called "Zincalume". This name being derived from the two main components of the

actual coating system, which consists of Zinc 55% / aluminium 43% / silicon 1.6% that

coat the steel base. The material is sent from the steel mill in large rolls of flat

sheet. The main difference in the coil products are:-

Zincalume - This is the natural colour of the sheet that looks similar to the

old galvanised iron. It weathers with times and loses it's bright shiny look.

Colorbond – Basically it is Zincalume with a paint surface added. It comes

in about 20 various colours. It has a plain painted finish to the underside.

Colorbond Metallic - A metallic sheen that changes under different light

conditions.

Colorbond Ultra - For severe coastal and industrial environments.

Stainless - For severe coastal and industrial environments.

Thickness - For the most part I think that for private house work the 0.42mm

thick is the most common. As you can see it is pretty thin stuff, less than

half a millimeter most of it.

Galvanised - Steel sheeting is still made, but in the thicknesses for roof

sheeting it most probably only done as special orders for heritage restoration

work. Where I do see it quite a lot is in the form of valley gutters, in thicker

gauges, say 2.0mm.

Various companies doing the different type of roll forming. They turn the coils

of flat into various standard profiles for which the engineering properties are

documented. The types of metal roofing will be as following:

Stainless steel. - Available for harsh conditions, rollformed and fixed similar to

corrugated steel profiles.

Aluminum - One of the longest lasting metals, but somewhat expensive.

Copper - Usually used for flashing or very small sections like covered

entryways. Expensive. If the building were ever to be dismantled the copper

would be reused because of its high value and variety of possible uses.

Stone Coated Steel - Stone Coated Steel shingle panels are made from pressure

formed, zinc/aluminum alloy coated steel with an acrylic, bonded, stone chip

finish, which resists fading and UV (Ultra-Violet) penetration. The panels are

lightweight (1.5 pounds per square foot) and walkable, and come in a variety of

earth-toned colors. They are fireproof and come with a 120-mile (190 km)-per-

hour wind rating and have a 50 yr to lifetime warranty against fading, cracking,

rusting, curling and de-granulation. Stone Coated Steel panels come in a wide

range of solid and Mediterranean blends and are vailable in both tile, shake,

slate and shingle style They withstand all extreme environmental elements

including Hail, Fire and Wind. Stone Coated Steel is ideal for flat to pitch

conversions and can even be installed over existing roofs without the need for

tear-off. Structural support is generally not required and can be walked on after

installation, too. Nails are installed horizontally to provide greater resistance

against vertical pullout due to high wind conditions.

Inverted Box Rib is a low-cost corrugated square-fluted iron roofing used

mainly in the South African market. It can be commonly seen all the way from

industrial sites to low-income shacks.

From the table shown below, that the shallower the roof sheeting pitch, the

deeper the ribs have to be, and also the thicker the material in most cases. There are a

handful of other profiles available but those are less common on typical house

construction. There are quite a few roof sheeting profiles available, but the main ones

for housing are as follows:-

Figure 2.2: Spandek Roof Sheeting.

Figure 2.3: Custom Orb Roof Sheeting.

Figure 2.4: Trimdek Roof Sheeting.

Figure 2.5: Klip-Lok Roof Sheeting.