NEPAL NATIONAL BUILDING CODE
NBC 113 : 1994

ALUMINIUM

Government of Nepal

Ministry of Physical Planning and Works
Department of Urban Development and Building Construction
Babar Mahal, Kathmandu, NEPAL

Reprinted : 2064

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12 December 1993

NEPAL NATIONAL BUILDING CODE
NBC 113 : 1994

ALUMINIUM
This publication represents a standard of good practice and therefore
takes the form of recommendations. Compliance with it does not confer
immunity from relevant legal requirements, including bylaws
tTsflng >L % sf] ;/sf/ -dlGqkl/ifb\_ sf] ldlt @)^).$.!@ sf] lg0f{ofg';f/ :jLs[tGovernment of Nepal

Ministry of Physical Planning and Works
Department of Urban Development and Building Construction
Babar Mahal, Kathmandu, NEPAL

Reprinted : 2064

NBC113V0.RV1

12 December 1993

iPrefaceThis Nepal Standard was prepared during 1993 as part of a project to prepare a National Building
Code for Nepal.
In 1988 the Ministry of Housing and Physical Planning (MHPP), conscious of the growing needs ofNepal's urban and shelter sectors, requested technical assistance from the United Nations Development
Programme and their executing agency, United Nations Centre for Human Settlements (UNCHS).
A programme of Policy and Technical Support was set up within the Ministry (UNDP Project
NEP/88/054) and a number of activities have been undertaken within this framework.
The 1988 earthquake in Nepal, and the resulting deaths and damage to both housing and schools, again
drew attention to the need for changes and improvement in current building construction and design
methods.
Until now, Nepal has not had any regulations or documents of its own setting out either requirements
or good practice for achieving satisfactory strength in buildings.
In late 1991 the MHPP and UNCHS requested proposals for the development of such regulations anddocuments from international organisations in response to terms of reference prepared by a panel ofexperts.
This document has been prepared by the subcontractor's team working within the Department ofBuilding, the team including members of the Department and the MHPP. As part of the proposedmanagement and implementation strategy, it has been prepared so as to conform with the general
presentation requirements of the Nepal Bureau of Standards and Metrology.
The subproject has been undertaken under the aegis of an Advisory Panel to the MHPP.

The Advisory Panel consisted of :Mr. UB Malla, Joint Secretary, MHPP
Director General, Department of Building(Mr. LR Upadhyay)
Mr. AR Pant, Under Secretary, MHPP
Director General, Department of Mines & Geology(Mr. PL Shrestha)
Director General, Nepal Bureau of Standards & Metrology(Mr. PB Manandhar)
Dean, Institute of Engineering, Tribhuvan University(Dr. SB Mathe)
Project Chief, Earthquake Areas Rehabilitation &Reconstruction Project
President, Nepal Engineers Association
Law Officer, MHPP (Mr. RB Dange)
Representative, Society of Consulting Architectural &Engineering Firms (SCAEF)
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ChairmanMemberMemberMemberMemberMemberMemberMemberMemberMember
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ii

Representative, Society of Nepalese Architects (SONA)
Deputy Director General, Department of Building,(Mr. JP Pradhan)

MemberMember-Secretary

The Subcontractor was BECA WORLEY INTERNATIONAL CONSULTANTS LTD. of New
Zealand in conjunction with subconsultants who included :Golder Associates Ltd., Canada
SILT Consultants P. Ltd., Nepal
TAEC Consult (P.) Ltd., Nepal
Urban Regional Research, USA
Principal inputs to this standard came from :Mr. RD Jury, BECA
Revisions and Updated to this code came from :Mr. Purna P. Kadariya, DG, DUDBC
Mr. Kishore Thapa, DDG, DUDBC
Mr. Mani Ratna Tuladhar, Sr. DIV. Engineer, DUDBC
Mr. Jyoti Prasad Pradhan, Ex.DG, DOB
Mr. Bhubaneswor Lal Shrestha, Ex. DDG, DOB
Mr. Uttam Shrestha, Architect, Architects' Module Pvt. Ltd.
Mr. Manohar Lal Rajbhandhari, Sr. Structural Engineer, Mr Associates
Mr. Amrit Man Tuladhar, Civil Engineer, DUDBC

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iii

TABLE OF CONTENTS

Preface ......................................................................................................................................................... i0Foreword ...................................................................................................................................... iv

1Guidelines for the Design of Aluminium Structures............................................................... 1
1.1
1.2
1.3
1.4
1.5
1.6

2Strength ............................................................................................................................ 1
Modulus of Elasticity ...................................................................................................... 1
Creep ......................................................................................................... ......................... 1
Thermal Expansion and Contraction........................................................................... 2
Fatigue .............................................................................................................................. 2
Corrosion Protection ...................................................................................................... 2

Guidelines for the Fabrication of Aluminium Structures...................................................... 2
2.1
2.2
2.3
2.4

Laying Out ....................................................................................................................... 2
Welding............................................................................................................................. 3
Mechanical Jointing........................................................................................................ 3
Heating.............................................................................................................................. 3

ADDITIONAL REFERENCES………………………………………………………………….... ..4

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iv0.

Foreword
This document is not intended to be a definitive design standard. Rather it is a series ofguidelines intended only for the designer of simple aluminium structures. Although the use ofaluminium as a structural material in Nepal is likely to grow in the future, the current usage
does not yet justify the preparation of a detailed Nepal Standard covering construction inaluminium.
Designers wishing to use aluminium as a structural material are referred to the relevant codesof other countries.

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11

Guidelines for the Design of Aluminium Structures
1.1Strength
Aluminium is always alloyed with minor quantities of other metals for structural use. Awide variety of yield and ultimate strengths are available, depending on the alloy. It is
important that designers ensure that the particular alloy they have assumed during theirdesign is that used for construction.
The stress-strain curves for aluminium alloys do not have a clearly defined yield point
and therefore the yield strength is defined as the 0.2 % proof stress.
Most aluminium alloys will retain their mechanical properties at temperatures up to 100°C. However, extended exposure to higher temperatures will lead to a loss in strength.
Limited, short-term exposure to high temperatures can be used to assist in bending, etc,
without significant loss in mechanical properties.
Under earthquake and wind loading, permissible stress increases similar to those definedfor steel structures may be used.
Many welding alloys have much lower mechanical properties than the parent material
and are often the limiting factor in determining the permissible stresses in a structure.

1.2

Modulus of Elasticity
The modulus of elasticity of aluminium can be as low as 35 percent of that of steel.
Thus, deflections will be larger than for similar sections in steel.
The lower modulus of elasticity also means that aluminium sections are likely to be more
prone to buckling problems than are steel sections. Twisting of columns, which is not
usually a problem with steel sections, needs to be considered for aluminium sections.
Generally, the distance between lateral restraining members will need to be less foraluminium beams.

1.3

Creep
When designing in aluminium, as for other materials, designers should bear in mind theeffects of long-term creep. Generally, design to established codes such as the SAA
Aluminium Structures Code will prevent problems with long-term creep.

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21.4

Thermal Expansion and Contraction
Aluminium alloys have a relatively high coefficient of thermal expansion and therefore
aluminium tends to move to a greater extent than other materials. In structures
incorporating other materials in conjunction with aluminium, designers must makeallowance for the different expansions and contractions in the jointing systems, etc, toavoid additional stresses.

1.5

Fatigue
Members which are subjected to fluctuations in stress (which need only be a small
percentage of the mean stress) may suffer from fatigue failure. The initiation of fatigue
cracks is due primarily to stress concentrations introduced by detailing. In the absence ofspecific requirements for aluminium, it is suggested that the general rules for steel
structures subjected to stress fluctuations are followed.

1.6

Corrosion Protection
Although most aluminium alloys have a high resistance to corrosion due to theformation of a thin transparent oxide outer layer, care must be taken to avoid contact
with dissimilar materials. Separation can be achieved by painting, but reference should
be made to appropriate sources for suitable paint types. The correct paint will dependon the type of metal to be separated and the exposure environment, i.e. marine, soil,concrete-encasement, etc.
Precautions must be taken to avoid water collection/pounding. Where practical,
structural members should be shaped or orientated to provide adequate drainage.
Aluminium, like other materials, can suffer premature corrosion if cracks, crevices orunsealed lips which entrap moisture are created.
Generally, stainless steel, galvanised and electro-galvanised fastenings can besatisfactorily used with aluminium. However, in severe conditions, e.g. marine
environment, de-passivation of the stainless steel can occur - leading to rapid corrosion.

2Guidelines for the Fabrication of Aluminium Structures
2.1

Laying Out
The scribing of set-out marks into the metal surface should be avoided as such marks
can lead to stress raisers in highly-stressed members.
In high temperature conditions, such as outside in hot weather, allowances should bemade for the different rates of thermal expansion of the aluminium and measuring
devices, particularly where high accuracy is required.

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32.2

Welding
Surfaces to be joined should be well prepared to minimise weld contamination byretained oxide. Adequate and correctly proportioned gas flow and proper shielding of
the work area should be achieved to prevent disturbance due to wind. Care should betaken to select the correct wire or rod size and type to match the design requirements.

2.3

Mechanical Jointing
When bolting, riveting or screwing aluminium, care must be taken to ensure adequate
bearing is provided and the fastener head dimensions are adequate.

2.4

Heating
Structural aluminium sections should not be heated, except that in order to easebending, heating to a temperature not exceeding 200 °C for a period not exceeding 30
minutes may be carried out. Such heating should only be allowed where sufficient
controls and supervision are in place to ensure that the above temperature and time
limits are adhered to.

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4
ADDITIONAL REFERENCES :Other useful references are:NBC113V0.RV1

Engineers Handbook - Aluminium - Design Data, The Aluminium Development
Council of Australia (Limited)Arya, A.S. and Ajmami, J.L., Design of Steel Structures, Fourth Edition, 1989 (Chapter
12 covering Aluminium Structures).

12 December 1993