SOUTH AFRICAN STANDARD
Code of practice for
The general procedures and loadings
to be adopted in the design of buildings
Reprint 1994
First Revision Published by
Amdt No. Date Text affected
I
I
SOUTH AFRICAN BUREAU OF STANDARDS
CODE OF PRACTICE
for
THE GENERAL PROCEDURES AND LOADINGS TO BE ADOPTED
IN THE DESIGN OF BUILDINGS
Obtainable from the
South African Bureau of Standards Private Bag X191
Pretoria
Republic of South Africa 0001 Telephone : (012) 428-791 1 Fax (012) 344-1568 E-mail : [email protected] Website : http:llwww.sabs.co.za COPYRIGHT RESERVED
Printed in the Republic of South Africa by the South African Bureau of Standards
(As amended 1991 and 1993)
NOTICE
This code of practice was approved by the Council of the South African Bureau of Standards on
7 November 1989.
In terms of the regulations promulgated under the Standards Act, 1982 (Act 30 of 1982), it is a punishable offence for any person to falsely claim compliance with the provisions of a code of practice published by the South African Bureau of Standards.
Authorities who wish to incorporate any part of this code of practice into any legislation in the manner intended by section 33 of the Act should consult the South African Bureau of Standards regarding the implications.
This code will be revised when necessary in order to keep abreast of progress. Comment will be welcomed and will be considered when the code is revised.
First Revision November 1989
Incorporating Amendment No. 1: 15 May 1990
Reprint incorporating Amendment No. 2: 15 November 1991
No. 3: 18 October 1993 This code of practice supersedes SABS 0160-1980
CONTENTS COMMITTEE SECTION 1 . SECTION 2
.
SECTION 3 3.1 3.1.
1 3.1.2 3.1.3 3.1.4 3.1.5 3.1.6 SECTION 4 . 4.1 4.2 4.3 4.4 4.4.1 4.4.2 4.5 4.5.1 4.5.2 SECTION 5 . 5.1 5.2 5.2.1 5.2.2 5.3 5.4 5.4.1 5.4.2 5.4.3 5.4.4 5.4.5 5.5 5.5.1 5.5.2 5.5.3. . .
6 SCOPE . . . 7 DEFINITIONS . . . 7GENERAL DESIGN CONSIDERATIONS
. . .
10Design Requirements
. . .
10 General. . .
10 Design procedure . . . 10 Vibration . . . 14 Stability . . . 15 Integrity. . .
15GENERAL GUIDANCE ON LIMIT-STATES DESIGN LOADS
. . .
17Deformations under service loads . . . 11
General
. . .
17Limit-states Criterion of Failure . . . 17
Limit-states Approach
. . .
18Uniform Load Factors and Load Combinations
. . .
18General . . . 18
Limit-states design loads . . . 19
Design Codes for Individual Materials
. . .
23General . . . 23
Assessment of partial material factors for material codes . . . 23
LOADS . . . 24
General . . . 24
Load Factors and Load Combinations . . . 24
Limit-states design methods . . . 24
Working stress design methods . . . 25
Amdt 3. . . . NominalPermanentLoadsG, 25 Oct . 1993 NominallmposedLoadsQ, . . . 25
Nominal imposed floor loads in buildings containing occupancies Nominal imposed floor loads in buildings containing storage and Nominal imposed roof loads
. . .
31Wind Loads W,
. . .
34Determination of nominal wind loads
. . .
34Nominalwindspeed V, . . . 36
Nominal wind pressures and forces . . . 41
other than industrial and storage occupancies . . . 25
. . .
industrialoccupancies 29 Amdt 3. Load reduction. . .
30 993 Forces on walls, balustrades and glazing. . .
32Blank
CONTENTS (continued)
5.5.4 Pressure and force coefficients
. . .
455.5.6 Simplified wind load design . . . 66
5.6.1 Seismic hazard zones
. . .
675.6.3 Planning considerations for low-rise housing in Zone II
. . .
715.6.4 Design load effect and load combinations
. . .
725.6.5 Seismic base shear
. . .
725.6.6 Distribution of seismic forces
. . .
765.6.7 Structural component load effects
. . .
775.7 Loads due to Overhead Travelling Cranes
. . .
785.5.5 Dynamiceffects
. . .
645.6 EarthquakeLoads
. . .
675.6.2 Design considerations for multistorey buildings in Zone I and Zone II
. . . .
705.7.1 5.7.2 5.7.3 5.7.4 5.7.5 5.7.6 5.7.7 5.7.8 5.7.9 General
. . .
Classification of travelling cranes. . .
Vertical wheel loads. . .
Horizontal transverse forces. . . . Horizontal longitudinal force . . . Forcesonendstops . . . Position of crane and crab More than one crane in a building Combination of crane lateral forces and wind load. . .
. . .
. . .
78 78 79 80 82 82 82 82 82 5.8 Otherloads . . . 825.8.1 Provision for impact and vibration
. . .
825.8.2 Lifting and handling equipment
. . .
835.8.3 Lateral and uplift forces . . . 83
5.8.4 Inertia sway forces . . . 83
5.8.5 Ceilings, skylights and similar structures . . . 83
SECTION 6
.
IN-SITU LOAD TESTING OF BUILDINGS AND BUILDING ELEMENTS . . . 836.1 General
. . .
836.1
.
1 Types of full scale load tests . . . 836.1.2 Planning . . . 84
6.2 Testing Authority . . . 84
6.3.1 Planning . . . 84
6.3.2 Conducting of tests . . . 85
6.3.3 Test precautions . . . 85
APPENDIX A . APPLICABLE PUBLICATIONS . . . 88
APPENDIX B . NOMINAL UNIT MASSES CIF MATERIALS . . . 90
APPENDIX C
.
NOMINAL IMPOSED LOADS. . .
95APPENDIX D
.
WIND FORCES . . . 97APPENDIX E . DEFORMATION OF BUILDINGS . . . 105
APPENDIX F . RAINFALL INTENSITY . . . 119
6
COMMITTEE
South African Bureau of Standards . . . RH Watkins (Chairman) I Jablonski (Standards Writer) A van Wyk
(Committee Clerk) Bruinette, Kruger, Stoffberg Incorporated . . . HJ Maoc
Concrete Masonry Association . . . JW Lane CSlR
Division of Building Technology . . . JAP Laurie RV Milford Division of Processing and Chemical Manufacturing Technology
. . .
MR NewhamSouth African Transport Services . . . J Geldenhuys Steel and Engineering Industries' Federation of South Africa . . . FH Pienaar The South African Association of Consulting Engineers . . . DJW Wium
University of Pretoria . . . BWJ van Rensburg University of the Witwatersrand . . . AR Kemp
SOUTH AFRICAN BUREAU OF STANDARDS CODE OF PRACTICE for 1. 1 .I 1.2 1.3 2. 2.1
THE GENERAL PROCEDURES AND LOADINGS TO BE ADOPTED IN THE DESIGN OF BUILDINGS SCOPE
This code of practice details the general structural design procedures and the minimum design loads to be adopted in the design of buildings or their structural members. This code of practice does not cover the following:
a) Detailed design appropriate to particular construction materials or methods; b) loads on bridges;
c) loads on earth-retaining structures and on structures subject to internal pressure from the contents (e.g. bunkers, silos, water tanks, etc.); and
d) dynamic loadings due to plant and machinery (other than loadings covered in
5.4.2.3,
5.7, 5.8.1 and 5.8.2).Loads incidental to construction c:annot, because of the wide variety and nature of the combinations, be specified. It is necessary, however, that the designer give conside- ration to the effects of such loads on a partly completed structure. (See also 5.1.2(b).) NOTE
a) The standards referred to in the code are listed in Appendix A-1 , and references that may be consulted for additional information are listed in Appendix A-2.
b) Nominal unit masses of materials that may be used in the calculation of loadings are given in Appendix B.
c) The assessment of floor loads in factories and warehouses is covered in Appendix C . d) Further information on wind forces is given in Appendix D.
e) Guidance on acceptable limits for deformations of various types of buildings is given in Appendix E. f) Guidance on the design of rainwater disposal from roofs is given in Appendix F.
DEFINITIONS
NOTE: Where it is desired to use t e r m in addition to the terms listed below, these terms should be selected from IS0 8930.
For the purposes of this code of practice the following definitions shall apply:
-
Act. The National Building Regulations and Building Standards Act, 1977 (Act 103 of Action. Any cause (load or imposed deformation) leading to internal forces in, or deformation of, the members of a structure, or the structure as a whole. It may be a) a set of concentrated or distrihuted forces acting on the structure (direct action), or b) imposed or constrained deforrnations within the structure (indirect action). Symbols such as a, a, E, etc., must be chosen to designate each particular indirect action.NOTE: The term
"load"
may be used with essentially the same meaning as "action".Combination of actions. A set of values for the actions occurring in a structure, that is used for the verification of the structural reliability of a structure for a limit state under the simultaneous influence of differerit actions.
Free action. Action which may have any distribution in space over the structure, within certain limits, e.g. action of vehicles on a bridge.
Permanent action. Action which is likely to act throughout a given design situation and for which the variation in magnitude with time is negligible in relation to the mean value, or for which the variation is always in the same direction until the action attains a certain limit value, e.g. self-weight, prestressing force.
Sustained action/Transient action. Terms used for a qualitative classification of actions, e.g. in a floor loading, the weight of the furniture represents the "sustained" action, and the weight of persons represents the "transient" action.
Building. As defined in the Act.
Code of practice. As defined in the Act.
Deflection. Movement of a defined point in a defined direction.
Medial deflection (Fig. 1). Deflection of the middle of a member relative and normal to
the line joining its ends.
Terminal deflection (Fig. 2). Deflection of the end of a member relative and normal to
the line through the opposite end parallel to its undeflected position.
Desiqner. In relation to the erection of a building or of part of a building, a competent person appointed by the owner to be responsible for the design of such building or part. Deviation. The distance of a defined point from a defined datum.
Medial deviation (Fig. 1). Deviation of the middle of a member from the straight line or plane joining its ends.
Terminal deviation (Fig. 2). Deviation of the end of a member from the straight line or
plane, horizontal or vertical (as relevant) through the opposite end.
Durabilitv. Ability of the structure and its members to maintain adequate performance in
time.
Dwellincl house. A building, together with any outbuildings appurtenant thereto, situated upon its own site and designed for occupation as a separate dwelling for one or more persons forming a household.
Dwellins unit. A dwelling other than a dwelling house comprising one or more rooms which have living, sleeping, eating, cooking and sanitary facilities for one or more persons forming a household.
Ground movement. Disturbance of foundations by influences not dependent on the loads applied by the building.
Limit states. States beyond which the structure no longer satisfies the design (performance) requirements.
Serviceabilitv limit states. Limit states related to normal use (often related to function). Ultimate limit state. Limit state corresponding to the maximum load-carrying capacity of a structure or of a part of the structure.
Load (see also Action)
Desian load. Design value of load.
Imposed load (The term Preferred to "live load"). Load due to intended occupancy (includes loads due to movable partitions and loads due to cranes), snow, ice and rain, earth and hydrostatic pressures, and horizontal components of static and inertia forces.
Nominal load. Nominal value of load.
Point-in-time load. The most-likely load which is on the structure at any instant in time (not the lifetime maximum value).
Self-weiqht (The term preferred to "dead load"). Load consists of the weight of all the members of the structure itself, plus the weight of all finishes, including permanent partitions, which are to be supported permanently by any member of the structure. Load arranqement. Arrangement of loads introduced into a calculation to allow for the variation in space of a free action, e.g. arrangement of traffic loads on a bridge.
Load case. A load case is determined by fixing the arrangement of each of the free
actions.
Local authoritv. As defined in the Act.
National Buildinq Reaulations. As defined in the Act.
OccuDancv. The use or purpose to which a building or site is normally put or intended to be put. (See the National Building Regulations for clarification of the various types of occupancies.)
Owner. As defined in the Act.
Partition. An internal vertical structure that is employed solely for the purpose of subdividing any storey of a building into sections, and that supports no load other than its own weight.
Undef lected
A
Deflected
SABS 0160
i
Org.11902-EC/00-07 a and b a r e medial deviations b e f o r e and a f t e r deflection a + b is m e d i a l d e f l e c t i o nFig. 1
-
Medial Deflection and DeviationV e r t i c a l l i n e r e p r e s e n t i n g t h e i n t e n d e d p o s i t i o n o f t h e member (column) a = T e r m i n a l d e v i a t i o n in n o - l o a d b = T e r m i n a l d e v i a t i o n in l o a d e d c = Terminal d e f l e c t i o n o r
\
condition condition movement o f t h e member, c a u s e d b y the l o a di
F r e e - s t a n d i n g (no l o a d ) p o s i t i o n'/
o f the member1
New p o s i t i o n o f the member under l o a d
I
3. 3.1 3.1.1
3.1.2
Serviceability. Ability of the structure and structural elements to perform adequately in normal use (serviceability limit-states related).
Settlement
Differential settlement. Relative displacement of different parts of foundations under the action of loads applied by the building.
m.
The effective span of horizontal or inclined members, assuming conditions ofsimple support. (For cantilevers
-
the overhang. For two-way spanning slabs-
the shorter span.)Standard specification. As defined in the Act.
Storev heiaht. The vertical distance between the points of support of horizontal supporting members at successive floor levels.
Structural safety. The capacity of a structure to resist all the actions, and also certain specified accidental phenomena, which it will have to withstand during construction and anticipated use (ultimate limit-state related).
Value (of a Darameter)
Characteristic value. Value fixed on statistical bases to correspond to a prescribed probability of not being exceeded on the unfavourable side during the lifetime of the structure. (See also Nominal value.)
Combination values. Values associated with the use of combinations of actions to take
account of a reduced probability of simultaneous occurrence of the most unfavourable
values of several independent actions. They may be expressed as a certain part of the nominal value by using a factor y,, I 1.
Desian values. Values obtained by application of partial safety factors to the relevant nominal values.
Partial safetv factor. This term describes all the y factors, which are principally
a) ?,factors (applicable to actions), the value of which reflects the uncertainties of
the actions;
b)
the
ym
factors (applicable to materials), the value of which reflects the uncertaintiesof the material properties.
Nominal value. The principal representative value of a parameter (either an action, or a property of a member or of a material), fixed on non-statistical bases, for example on experience acquired or on physical constraints.
G EN ERAL DES I G N CONS I DERATIO N S
DESIGN REQUIREMENTS
General. Ensure that any building or any part of a building is designed to possess sufficient structural capacity to resist safely and effectively all loads and influences that may reasonably be expected to act upon it, having regard to the expected service life of such building.
Desian Procedure. In order that the design of a building or of part of a building may
comply with the provisions of the National Building Regulations’), ensure that
a) the procedures adopted in such design are in conformity with this code and with any other code of the South African Bureau of Standards that is relevant to the materials used in such building or in part of such building; or
b) the design is in accordance with the empirical rules contained in SABS 0400, relevant to specific elements of a building; or
c) the design is in accordance with one of the following alternative methods:
1) A code of practice other than prescribed above;
2) an analysis based on generally established theory;
3) an evaluation of a full-scale building or a prototype by test loading;
1) Published by Government Notices 1211 of 6 July 1977, R441 of 1 March 1985, 729 of 18 April 1986 and
3.1.3
4) studies of model analogues; or
5) an authoritative document covering in detail the design of a building or a structural member for a specific purpose or a specific material or both, provided that where a material is used for which there is no SABS specification, the design is in accordance with a safe method applicable to such material.
In terms of the National Building Regulations, alternatives (a) and (b) above are deemed to satisfy the regulations and therefore must in all cases be accepted by the local authority. A design based on one of the methods given in (c) above may have to be justified by the designer to prove that it will ensure the level of safety and performance implicit in the regulations. The deemed-to-satisfy requirements for the use of specific materials employed in the construction of a building or of part of a building are given in SABS 01 00 for structural concrete
SABS 01 37 for glazing SABS 0161 for foundations SABS 0162 for structural steel SABS 0163 for structural timber SABS 0164 for structural masonry
The empirical rules contained in SABS 0400 relate to Foundations (see Part H)
Floors (see Part J) Walls (see Part K) Roofs (see Part L)
Glazing (see Part N)
Deformations under Service Loads. So design structural members that their deforma- tions under expected service loads will be acceptable with regard to
a) the intended use of the building or member;
b) possible damage to non-struct.ural members and materials; and
c) possible damage to the building itself, taking account, where significant, of the additional effects of loads acting on the deformed building or member; and
d) possible damage to the adjacent buildings.
NOTE: Table 1 is a summary of suggested deformation limits and should be read in conjunction with Appendix E.
(To be read in conjunction with Appendix E) 1 ~~ Type of deformation Deflection
Particular deformation Critical elements and criteri:
I
Medial deflection of floors
Medial deflection of roofs or roof members
Terminal deflection of cantilever floors Terminal deflection of
cantilever roofs Terminal deflection of non-
cantilevered horizontal members Terminal deflection of vertical members Stability Damage at supports Ceiling damage Partition damage Stability Damage at supports Ceiling damage Partition damage Roof covering damage Ceiling damage Partition damage Ceiling damage Partition damage Damage at supports Damage at supports 4
Suggested limiting value
Span1300 Span1300
Varies with construction (usually less critical than partitions)
Span1500 to span1300 (floor beneath partition) 10 mm if Clh < 3,5 (floor below partition)§ 10-15 mm if Qlh < 3.5 (floor above partition)§ Span1300
Span1300
Varies with construction 10-15 mm if Qlh < 3,5511 Span1250 to span1125 Varies with construction
Span1500 to span1300 (floor beneath partition) Varies with construction
10-1 5 mm§// Span1250 to span1125 Span1100 Span1500 Storey height1100 Storey height1500 5 6 7 a 9 10 Construc- tion devia- tion* Actions Diff. settle- ments+
-
-
-
EC EC EC-
-
KEY:Q = length or span of member. h = height of element. C = creep deflection. E = elastic deflection.
Thermal and moisture movements may also be involved according to the construction arrangement and the environment. 'Taking account of any camber provided.
+Under all appropriate actions.
$Includes the self-weight load of the structure, cladding, finishes, partitions and also pre-stress where this contributes to the deformation under consideration §In this case the floor or roof is considered to be isolated from the partition in question.
/I Deflection at the nodes in the case of a roof truss.
**The creep component need only be included if the imposed loads are long-term actions. Hail and snow are not normally long-term actions in South Africa. ++If acting eccentrically.
I displacements involvc load$ C
I
E
C I **EC C *'EC1
-
iail or snow load-
** E **E "E **E **E-
Nind load-
EMedial deviation of floors Medial deviation of roofs
and roof members Terminal deviation of
cantilever floors
Terminal deviation of cantilever roofs Terminal deviation of non-
cantilevered horizontal members
Terminal deviation of vertical members Oscillations of members Oscillations of the building
as a whole Appearance Use (curvature) Appearance Appearance Use (curvature) Use (rotation) Appearance Use (slope) Stability Appearance Resonance Use Use Type of deformation Deviation Oscillations KEY:
I
Particular deformation Critical elements and criteria Suggested limiting value Construc- tion devia-tion" Visible length1250, or 30 mm
Span1300 Yes
Visible length/250, or 30 mm Yes Visible length1250, or 15 mm
Span1125
Yes
I
Yes Span11 00 Yes Visible length1250, or 15 mm Yes SDan1lOOI
yes++EC **++EC "++E ++EC **++EC **++E
P = length or span of member. h = height of element. C = creep deflection. E = elastic deflection.
Thermal and moisture movements may also be involved according to the construction arrangement and the environment. 'Taking account of any camber provided.
+Under all appropriate actions.
$Includes the self-weight load of the structure, cladding, finishes, partitions and also pre-stress where this contributes to the deformation under consideration. §In this case the floor or roof is considered to be isolated from the partition in question.
I / Deflection at the nodes in the case of a roof truss.
**The creep component need only be included if the imposed loads are long-term actions. Hail and snow are not normally long-term actions in South Africa. ++If acting eccentrically.
3.1.4
Commentary:
The deformation of a building or of any part of a building should not adversely affect the appearance or proper functioning of the building. The designer must satisfy himself that the deformations under service conditions will not be excessive, having regard to the particular characteristics of the building, including its size, type of cladding, partition construction, finishes and occupancy, as well as the foundation conditions and environmental conditions to which it is subject.
This consideration should cover the possible effects of differential axial deformations of members as a result of temperature, moisture and short- term or long-term loading effects, as well as effects due to deflection of members.
Where experience or analysis shows that movement or stress relief joints are necessary to avoid damage, overstressing or instability of elements of the building, such joints must be designed and suitably described in the de- sign documents.
Note that the deformation in question in a particular case is that due to the relevant portion of the loading or environmental effect, e.g. for control of cracking in partitions, it would be that portion of the elastic and creep de- flection of the supporting floor that occurs after construction of the partition (this will also depend on when the floor props are removed). Note also that a distinction is made in Table 1 between deflection, which is the movement of a defined point in a defined direction, and deviation, which is the distance of a defined point from a defined datum (e.g. out of straightness or out of plumbness, whether due to deflection or to initial distortion). Deviation limits are generally related to appearance factors but may in some cases involve use and stability.
Whilst it is undesirable that the deformations of a building damage adjacent buildings, or inconvenience their occupants or other members of the public, such matters are normally the subject of legislation and are not appropriate to this code. Nevertheless, attention may be drawn to the fact that the pro-
vision of movement joints between adjacent buildings and the avoidance of
interference with neighbouring foundations are normal good building prac- tice.
Vibration
a) Give special consideration to floor systems susceptible to vibration, to ensure that such vibration is acceptable for the intended occupancy of the building.
b) Investigate unusually flexible buildings and, where necessary, check lateral accelerations of the building to ensure that such accelerations are acceptable for the intended occupancy of the building.
commentary:
a) In the majority of buildings, the stiffness provided to conform to the deformation limit state will be such that no further consideration of vibration is necessary. Where specific consideration of vibration is required by virtue of known repeated loading, the following should be taken into account (See also Table 1 .):
1) The damping characteristics of the material;
2) the dynamic magnification effects on the structural members; and
3.1.5
3.1.6
b) Two types of vibration problems require attention in building construc- tion, i.e. continuous vibration and transient vibration. Continuous vibration results from the periodic forces of machinery or of certain human activities such as dancing. These vibrations can be considerably amplified by resonance when the periodic forces are synchronized with a natural frequency of vibration of a building. Transient vibrations are caused by footsteps or other impiacts followed by decay at a rate which depends on the available damping.
The undesirable effects of continuous vibrations caused by machines can be minimized by special design provision, such as location of machinery away from sensitive occupancies, vibration isolation, or alteration of the natural frequency of the structure. Human beings can create periodic forces in the frequency rartge of approximately 1-4 Hz, and floor resonant frequencies of less than about 5 Hz should be avoided for light residential floors, schools, auditoria, gymnasia and similar occupancies. For very repetitive activities such as dancing, some resonance is possible when the beat is on every second cycle of floor vibration, and it is therefore recommended that the resonant frequency of such floors be 10 Hz or more, unless there is a largo amount of damping.
Stability. Ensure that adequate provision is made for the stability of a building as a whole and for that of its elements against overturning, uplift, sliding, foundation failure and stress reversal.
This requirement may be deemed to have been met if
a) in analysis according to the (ultimate) lirnit-state method: The sum of the effects of the destabilizing nominal loads multiplied by the appropriate partial load factors that exceed unity as specified in 4.4.2, combined with the effects of the stabilizing component of self-weight load multiplied by the load factor less than or equal to unity as specified in 4.4.2, does not exceed the ultimate resistance of the relevant parts of the structure and its foundations; or
b) in analysis according to the permissible working stress method: The sum of the effects of the destabilizing design loads combined with 0,7 times the effects of the stabilizing component of the self-weight load does not exceed the design resistance of the relevant parts of the building and its foundations.
Commentary:
The adoption of the passive resistance of the soil as part of the resistance to sliding should be carefully considered, as full passive resistance general- ly comes into play only after movement has taken place.
lntearity (See also 4.3)
a) The degree of safety of a structure depends not only on the strength of the load-bearing members and of the structure as a whole but also on the integrity of the structure, i.e. its ability to withstand local damage without it causing or initiating widespread collapse. Adequate structural integrity may be achieved by
1) designing the structure in such a way that, if any single load-bearing member becomes incapable of carrying load, this will not cause collapse of the whole structure or any significant part of it within a period of time sufficient to make the necessary repairs (method of alternative paths of support); or
2) minimizing by design or by protective measures the probability of failure of a load-bearing member whose failure is likely to result in widespread collapse (method of local resistance).
b) Design every building to withstand, at any level, a horizontal force acting on the portion of the building above that level and acting in any plan direction, the magnitude of the force being at least equal to the greater of
1) the wind load acting above that level; or
2) 1 '/o of the total nominal self-weight load above that level, including that due to
unlocated partitions exerting a force exceeding 3 kN/m of length.
This force may be shared between the elements of the structure, depending on their stiffness and strength.
c) Traditional structures, particularly building structures, often possess an adequate degree of structural integrity. When a review of a structure's integrity indicates that the consequences of failure could be widespread or otherwise very serious or when the structural integrity of a new or unusual form of construction is being evaluated, specific provisions for structural integrity as indicated above should be incorporated in the design. Commentary:
The following is intended to give guidance when progressive collapse is
considered:
a)
It
is clearly not feasible to design all buildings for absolute safety nor is it economical to design for abnormal events unless there is a reasonable chance that they will occur. However, when there is a reasonable chance ofabnormal occurrences, the designer must, in terms of 3.1.6, consider
rational means of limiting the spread of local failure to an extent disproportionate to the initial cause of local damage.
Some abnormal events that can occur are explosions due to gas, boiler failures or ignition of industrial liquids, vehicle impact, falling or swinging
objects, adjacent excavation or flooding causing severe local foundation
failure, or very high winds such as cyclones or tornadoes.
Most of the foregoing events would not in general be considered in design, but events such as fires, earthquakes (in certain areas of South Africa), and corrosion, which are taken into account in the normal course of design, should also not cause progressive collapse.
Although a building should have resistance to progressive collapse caused by "accidental" abnormal events, it is accepted that well-placed explosives could bring down any such building.
In some traditional construction systems there is inherent structural integrity,
a tying together of elements and an ability to redistribute overloads. This
inherent integrity is frequently overlooked in new systems and, as a consequence, prefabricated systems in particular are often designed to resist the primary gravity and lateral forces only. The resistance to progressive collapse should be fully evaluated for any new system and if such resistance is not inherent in the system, it should be provided by other means.
b) There are four general considerations that can be used in designing to prevent progressive collapse:
1) Reduction of the probability of the occurrence of an abnormal event;
2) design using ductile connection;
3) design to resist abnormal loads;
4.
4.1
4.2
c) It is difficult to apply limits to collapse resulting from an abnormal event; however, it is suggested that collapse be limited,
1) where progression is vertical, to the storey where the event occurred and to the storeys immediately above and below;
2) where the progression is horizontal,
i) to the truss, beam, precast strip floor, or roof panel damaged, and to the one on either side;
ii) to a single bay of a full bay-sized floor or roof slab except that where the
principal support at one end of a slab is removed, two bay-sized panels may act together as a catenary.
d) Severe deformation is temporarily acceptable in the vicinity of the local failure at the ultimate conditions. A load combination of self-weight load plus one-third of the total of the specified imposed load plus wind load should be used in evaluating the ultimate stability and ultimate strength of the damaged building after the event.
GENERAL GUIDANCE ON LIMIT-STATES DESIGN LOADS
NOTE
a) This section is not to be used unless there is a reference to it in the material code. b) See NOTE (b) to Section 5.
GENERAL. This section describes a standardized formulation for preparing limit-states codes for different structural materials. This is achieved through a two-phase process: a) Acceptance of a set of partial load factors and a uniform system for defining load combinations which would be applicable to all structural materials, as described in 4.4.2. b) Subsequent evaluation of partial material factors, and resistance (or performance) factors appropriate to each limit state in each material code in order to achieve a consistent level of reliability, as described in 4.5.
LIMIT-STATES CRITERION OF FAILURE. The criterion of fitness for purpose is: Amdt Oct. 1993 3,
where Rd = design resistance
Qd = design load or action effect and Rd and Qd are given by
where R( ) = a function defining the resistance of the structure for a particular limit state
fk
= the characteristic: material strengthym = the partial material factor which allows for uncertainty in the material strength
Amdt 3,
Oct. 1993
@Q = the resistance (or performance) factor which allows for all other
uncertainties in modelling the as-built structure by equation 4(a) for the limit state under [consideration, and for brittle modes of failure
QnI =
YI
= 4.3 4.4 4.4.1 v / I =the effect of the nominal action or load defined in the loading code; the summation reflects the combination of self-weight, imposed, wind or other types of load effect appropriate to that limit state
the partial load factor defined for the type of action or load i which allows for variability in the action and an average uncertainty over all materials and limit states in the process of modelling the effect of the action
the load combination factor applicable to action or load i which allows
for the probability of simultaneous occurrence of different load types in a particular load Combination.
LIMIT-STATES APPROACH. Astructure, or part of a structure, is considered unfit for use or to have failed when it exceeds a particular state, called a limit state, beyond which its performance or use is impaired. The limit states are classified into the following two categories:
a) Ultimate limit states are those concerning safety, and correspond to the maximum load-carrying capacity. They include:
1) Loss of equilibrium of the whole or of a part of the structure considered as a rigid body (e.g. overturning, uplift);
2) loss of load-bearing capacity of members, due to exceeding material strength,
buckling, fracture, fatigue, fire or deformation; 3) overall instability of the structure;
4) very large deformation, e.g. transformation into a mechanism.
b) Serviceability limit states are those which restrict the normal use and occupancy or affect durability. They include:
1) Excessive deflection or rotation that affects the use of the structure, the appearance
of structural or non-structural elements or the operation of equipment;
2) excessive local damage (cracking or splitting, spalling, local yielding, slip of connections) that affects the use, durability or appearance of the structure;
3) excessive vibration that affects the comfort of the occupants or the operation of equipment.
All relevant limit states should be considered in the design; the usual approach, however, will be to design on the basis of the expected critical limit state and then to check that the remaining limit states will not be reached.
UNIFORM LOAD FACTORS AND LOAD COMBINATIONS
General. It is intended that future issues and revisions of design codes for structural
materials in South Africa will, whereverfeasible, be expressed in a limit-states format and will conform to a single set of partial load factors and a uniform system for defining load com binations.
Cornrnen tary:
The uniform set of partial load factors and load combination factors defined in 4.4.2 is based on the assumption that the following two-stage procedure is a legitimate approach:
a) Identification of partial load factors and load combination factors from available statistical data on common types of loading that give consistent combinations of design load effects possessing a maximum probability of occurrence comparable with existing practice. (The results of this analysis are defined below.)
4.4.2
b) Identification of partial material factors for each structural material and partial resistance factors for each limit state that, from available statistical data on resistance of different limit states, give consistent probabilities of failure, using the loading information obtained from (a) above. (This assessment will be undertaken by the individual code committees for the different structural codes.)
This is different from the approach adopted in North America and Australia, where the assessment of each limit state and load combination is under- taken ab initio, allowing for variability in both load effect and resistance. A practical problem associated with a full reliability analysis of this type is that the statistics of both the load effect and the resistance of the member are required. In South Africa, statistics for member resistance, related to the relevant materials codes, are largely unavailable at present and it would be a lengthy process to collect the necessary information. A further problem is that several of the materials codes are still in the process of preparation and it is also anticipated that some of the existing codes may undergo major revisions in the future.
In terms of the above, the partial load factors and load combination factors defined subsequently were therefore selected in order to achieve a consistent value of a load index a, calculated as follows:
where
Qd = the design load effect = Z(wiyiQni)
PQ = the curnulative probability of the load exceeding the design value
The target value of the load index a used in this assessment is 2,O at the ultimate limit state (equivalent to a 1 % probability of exceeding the design value in the 50-year life of the structure) and 1
,O
at the serviceability limit state (equivalent to a 10 % probability of exceeding the design value). The actual minimum values of a at the ultimate limit state over a practical range of load combinations range from 1,6 to 2,0, owing to a desire to deviate from existing practice as little as possible.Limit-states Desian Loads
NOTE: The partial load factors and load combination factors described in this section are to be used only in cases where the relevant material design code has been drafted or modified to be compatible with these provisions.
The design load effect Q pertaining to the ultimate and serviceability limit states is obtained from equation 4(e) or 4(f), as the case may be, by multiplying the effects of the nominal loads by the partial load factors given in Column 2 or 3 of Table 2, as applicable, and by the relevant load combination factors given in Column 4 of Table 2 or derived from the recommendations given in Table 3 (depending on the time-dependent nature of the additional load and its correlation to the dominant load).
(As amended 1991 and 1993)
20
where Amdt 3, Oct. 1993 Amdt 3, Oct. 1993 Amdt 3. Oct. 1993yi = the partial load factors given in Table 2
D, = the nominal permanent load effect
Q, = the dominant imposed load effect for the load combinations and limit state
under consideration
Qni = additional imposed load effects relevant and significant to the load combination and limit state under consideration
t,ui = the load combination factors given in Tables 2 and 3
The design point-in-time value of the load effect Qdpis obtained from equation 4(f) as follows:
Qdp = YD Dn + 2 (ViYiQnJ 4(9)
The design point-in-time value obtained from equation 4(g) may be required in the following design situations:
- determination of the sustained load contribution for analysis of time-dependent
behaviour of materials at the serviceability limit state
-
analysis of stability of structures with localized accidental damage at the limit stateof accidental damage
analysis of residual strength of structures at the limit state of progressive collapse. -
For self-weight D,, imposed floor loads Q, and wind loads W , , the following combina- tions can be used at the ultimate limit state:
with the exception that the load factor 0,5 for imposed loads must be replaced by 1
,O
forgarages, filing areas and storage areas and by 0,O for roof loads, and the load factor 1,3
for wind loads must be replaced by 1,5 for chimneys and free-standing towers. The following combinations can be used at the serviceability limit state:
171Dn + 1,OQn
l,lD,
+
0,3Q,+
0,6W,with the exception that the load factor 0,3 must be replaced by 0,6 for garages, filing
areas and storage areas and by 0,O for roof loads.
NOTE: The 0,6 serviceability wind load factor should be used in conjunction with the 50-year mean return period of wind speed only.
Amdt 2, Nov. 1991
The sustained portion of the loads at the serviceability limit state is obtained from 1,lQ + 0,3Qn
with the same proviso on the factor 0,3 as above.
The design load effect may be adjusted at the discretion of the designer by multiplying the design load effect in equation 4(e) and 4(f) by an importance factor yc to allow for the consequences of failure. In the case of critical structural members of structures in which large numbers of the public gather and where there would be "very serious" con- sequences of a failure, a value of yc in the range 1,1-1,2 should be used. For structures with a very low degree of hazard to life and "not serious" consequences of failure, a value of yc of 0,9 would be appropriate.
TABLE 2
-
PARTIAL LOAD FACTORS AND LOAD COMBINATION FACTORS1 Type of load Permanent loadinq
a) Maximum self-weight load acting in isolation (eqn 4(e))
b) Maximum self-weight load acting in combination with other loads (eqn 4(9)
c)Minimum self-weight load Imposed loading
d) Wind load
e) Loads on floor (other than garages, filing or storage areas)
f) Loads on floor for garages, filing or storage areas
g) Loads on roof (other than those in (d) and (h)-(l))
1) Inaccessible roof
2) Accessible roof h) Earthquakes i) Loads from fluids j) Imposed deformations
1) Temperature, settlement, etc.
2) Prestressing k) Accidental loads
I) Other types of imposed loads not considered above (e.g. material loads, cranes) in the absence of more detailed information
I
Partial load factor Y;
Ultimate limit state Serviceability limit state 1 ,o 1
.o
1.o
4 Load combination factor i,ui 1,o
1,o
0 0.3 0,6 See Table 3 1,o
0 See Table 3 Amdt 3, Oct. 19931 3 for slender non-redundant structures such as chimneys and free-standing towers that exhibit significant cross-wind response.
SABS
(As amended 1991 and 1993)
22
It is necessary for the designer to assess the degree of dependence or correlation between the dominant load and the additional load, and the variation of the additional load with time. For example, for a single crane where horizontal crane load is the
dominant load and vertical crane load an additional load, a value of cy = 0,75 would
frequently be appropriate. For two cranes working in tandem, cy = 1 would apply. For
cranes in adjacent bays that operate completely independently, cy = 0,5 may be applied
to the additional load from the second crane. Examples of the influence of the time
variation of loads are implied by the values of cy = 1 in Table 2, for imposed loads of a
semi-permanent nature such as storage loads or loads from fluids, where the additional load is assumed to be uncorrelated to the dominant load. In addition, it is expected that the designer would not include as additional loads those types of load that, when factored, contribute in an insignificant manner to the total load.
Amdt 3, TABLE 3
-
RECOMMENDED LOAD COMBINATION FACTORS FOR Oct. 1993 TYPES OF IMPOSED LOADINGS NOT COVERED BY TABLE 2I I
Correlation between dominant imposed load and additional
imposed load None
Partial
Variation of additional load with time, i.e. the ratio: Arbitrarv point-in-time value
Lifetime maximum value
0,s
1
,o
0 3
3
Load combination factor
'+"i
Examples of common applications of Tables 2 and 3 are: Amdt 3, 1 3 (PERMANENT)
Oct. 1993
1,2 (PERMANENT) + 1,6 (FLOOR)
0,9 (PERMANENT) + 1,3 (WIND) + 0,8 (CRANE HORIZONTAL) + 0,8 (CRANE
VERTICAL)
1,2 (PERMANENT) + 1,6 (CRANE VERTICAL) + 0,5 (FLOOR) + 1,2 (CRANE
HORIZONTAL) Commentary:
No provision has been made for pattern loading of permanent loads. North American practice is adopted in which this effect is apparently absorbed in the portion of the partial load factors that allows for modelling uncertainties and in terms of the definition of permanent loading.
Considering Tables 2 and 3, at the ultimate limit state, the factored values of the self-weight and dominant load effects reflect the lifetime maximum load effects, and the factored value of the additional load effect reflects the instantaneous or arbitrary point-in-time value which is likely to occur simultaneously with the lifetime maximum of the dominant load.
At the serviceability limit state, the factored value of the self-weight and dominant load effects and the factored value of the additional load effect may be compared to the mean point-in-time value of the sustained portion of the load effect.
4.5 4.5.1
4.5.2
It should be emphasized that appropriate statistical information is not available for types of loading other than self-weight, wind and office floor loading. Load factors for other types of loading (vehicles, material storage, retail and residential, crane and temperature) should therefore be based either on the partial load factors and load combination factors given in Tables 2 and 3 or, where it is apparent that these are inappropriate, on the judgement of the designer.
The load factor of 1,3 for wind loads is increased to 1 3 for chimneys and free-standing towers that exhibit significant cross-wind response, owing to the greater uncertainty in the structural response. The wind load factor is also increased to take into account the likelihood that the maximum cross-wind response due to vortex shedding occurs at a relatively low wind speed, and not at an extreme wind speed, and therefore has a greater probability of occurrence.
A specified magnitude of importance factory, has a greater influence on the probability of failure for a limit state with a small coefficient of variation and is therefore material dependent.
DESIGN CODES FOR INDIVIDUAL MATERIALS
General. It is intended that codes for each structural material will include appropriate values for the partial material factors, and resistance (or performance) factors applicable
to the limit states in such codes, in accordance with equation 4(b). Partial factors will be
established on a consistent basis, using a procedure that involves identifying values for these partial factors that achieve probabilities of failure for different limit states over the practical range of properties, dimensions and loads which are consistent with existing practice.
Partial material factors of 1,50 for concrete, 1 ,I 5 for reinforcement and 1,075 for struc- tural steel are likely to be adopted in codes applicable to those materials. In the assessment of individual limit states, an appropriate resistance or performance factor (@@ in equation 4(b)) will be determined allowing for these partial material factors so that at least the following target values of safety index@ are achieved:
Ductile, gradual modes of failure :
J'=
3,O Brittle, sudden modes of failure : @ = 4 , 0 Connection details between components : @ = 4 3The safety index@ is the inverse of the cumulative normal distribution function @-' of the probability of failure pf which is defined as the probability of the effect of the actions or loads exceeding the resistance of a particular limit state (equation 4(a)), i.e.
Assessment of Partial Material Factors for Material Codes. It is clearly desirable that consistent partial material factors be adopted in different structural codes to allow for uncertainties in material strengths (for example, the factors for composite beams should correspond to those in the concrete and steel codes). These partial material factors should correspond to existing practice in SABS codes.
It has been shown that for material strengths and resistances with a coefficient of
variation in the range 0,lO-0,30 (which covers most materials used in construction), a safety index of@ = 3,O (required for ductile failure modes) will be achieved if the partial material factors and partial resistance factors are selected on the basis of achieving a 1 % resistance fractile (i.e. the resistance of not more than 1 % of members will be less than the design resistance). This is therefore a suitable definition of a design strength for ductile members. For members with a coefficient of variation in the range
(As amended 1991 and 1993) 5. 5.1 5.1 .I 5.1.2 5.2 5.2.1
0,lO-0,15 (which is typical of structural steel and reinforced concrete), a safety index
ofJ =
4,O
(required for brittle failure modes) will be achieved if the partial resistancefactor forJ = 3,O is reduced by a factor of about 0,7-0,8, whereasp = 4,5 (required
for steel connections) will be achieved if the partial resistance factor forJ = 3,O is
reduced by a factor of about 0,6-0,7. LOADS
NOTE
a) Since in general practice nominal values of loads are used more often than characteristic values of loads, the term "nominal" will be used in relation to load values. (See definition of in 2.1 .) b) Take the nominal values of loads given in this section for use with limit state design methods to be synonymous with the design or service loads for use with the permissible working stress methods of design .
GENERAL
Ensure that, except as provided for in 5.1.2, the following loads, forces and other effects are, where relevant, considered in the design of a building and its structural members and connections:
a) Self-weiuht loads G, as provided for in 5.3.
b) ImDosed loads Q, due to intended occupancy (includes loads due to movable partitions and loads due to cranes), snow, ice and rain, earth and hydrostatic pressures, and the horizontal component of static or inertia forces, as provided for in 5.4.
c) Wind loads W, or earthuuake loads E,, whichever produces the more unfavourable
effect, as provided for in 5.5 and 5.6.
d) Loads due to overhead cranes and other loads applicable to special conditions, as provided for in 5.7 and 5.8.
e l Deformations due to one or more of the following: 1) Temperature changes, shrinkage, moisture changes; 2) creep in component materials;
3) movement due to differential settlement or heave.
a) Where a building or structural member can be expected to be subjected to loads,
forces or other effects not listed in 5.1 . I , or where the loads or forces listed in 5.1 . I differ significantlyfrom those given in the relevant tables, ensure that these are taken into account in the design, using the most appropriate information available. b) Precautions must be taken in the design to ensure that, during all stages of construction, the building or any part of the building is not damaged, distorted or
made unserviceable owing to the application of excess loads in the construction
process.
c) If it can be shown by the application of engineering principles, or if it is known from experience, that disregard of some or all of the effects resulting in deformations (as listed in 5.1 . I (e)) will not affect the safety and serviceability of the building or of any part of the building, calculation for these specific effects may be omitted.
LOAD FACTORS AND LOAD COMBINATIONS
Limit-states Desian Methods. In limit-states design procedures, use the most adverse combinations of the various types of loads as specified in the appropriate limit-states material design codes of practice, and factored according to the partial load factors specified in such codes of practice for each load combination and limit state under consideration.
5.2.2
5.3 5.3.1
5.3.2
Workina Stress Desian Methods.
a) Where the design is to be executed by the permissible working stress method, use the following loads and load combinations:
1) Self-weight load G,;
2) self-weight load plus imposed load (G,
+
Q,J;3) self-weight load plus wind load or earthquake load (G,
+
W,) or (G,+ En);
4) self-weight load plus imposed load plus wind load or earthquake load 5) any one of (1)-(4) above, together with those dimensional change effects not exempted in terms of 5.1.2(c).(Gn
+ Qn + W,J or(Gn
+ Qn + E,);b) Where the effects of self-weight loads counteract those of other loads or load combinations in any of (a) above, the value of the self-weight load to be used in this case is the nominal self-weight load multiplied by a reduction factor of 0,7 (see 3.1.5(b)).
NOMINAL PERMANENT LOADS G,
The nominal permanent load for a building or for a structural member of the building consists of
Arndt 3,
Oct. 1993
a) the weight of the building or rnember itself, plus
b) the weight of all finishes and materials of construction which are incorporated into the building or member and which are to be supported permanently by the building or member, including permanent partitions, but excluding movable or unlocated partitions (see 5.4.1.3), domestic appliances and sanitary appliances, which are treated as imposed loads.
Commentary:
Designers and owners are advised to give special thought to the likely types and positions of partitions, since insufficient provision for partitioning may reduce the future utility of the building.
Calculate nominal permanent loads from the actual known masses of the materials to be used. Where there is a reasonable possibility of a significant change in mass owing to the absorption of moisture by porous materials, make due allowance for such increase when calculating permanent loads.
Com men tary :
Where the unit masses of materials are not known or where approximations are sufficient for a preliminarydesign, use may be made of the data given in Appendix B.
5.4 NOMINAL IMPOSED LOADS Q,,
5.4.1 Nominal Imposed Floor Loads in Buildinas Containinq Occupancies other than Industrial and Storaae Occupancies
5.4.1.1 Occupancies included in Table 4. Where a building or part of a building contains a class of usage listed in Column 2 of Table 4, for the design of its floors use nominal imposed loads of at least
a) the appropriate uniformly distributed floor load given in Column 3, such load being applied over either the entire floor area or such part of the floor area as will produce the most severe effects on the element under consideration;
(As amended 1993)
26
b) the appropriate concentrated load given in Column 4, applied over the plan area given in Column 5 and placed in the position that produces the most severe effects on the element under consideration.
NOTE
1) The loads in Columns 3 and 4 should not be considered as acting simultaneously; 2) the loads in Column 3 may be reduced in accordance with 5.4.3.
OccuDancv classes not included in Table 4. Where the category of usage of a floor
area is not provided for in Table 4 or where it is desired to determine the intensity of
a nominal imposed floor load (or floor loads) because of special circumstances, such load(s) may be determined from an analysis of the likely loads and their effects for the particular occupancy. Generally, the imposed floor loads should be applied as in
5.4.1 .I. The values so obtained should be in appropriate relationship to those in the
most relevant categories of usage in Table 4. 5.4.1.2
2 3 A €3 4 5 Load
I
categoryAccess catwalks in buildings 0 , l x 0,l 2,o 5,O
2,o 10,o Classrooms, lecture theatres
X-ray rooms, operating theatres
Garages and parking areas for vehicles of gross weight less than 25 kN excluding garages where mechanical parking or stacking devices are employed
Offices for general use* 2 3 0,75 x 0,75
offices with data-processing and similar equipment* Cafes, restaurants
Dining rooms, dining halls, lounges, kitchens, communal bathrooms and toilets in educational buildings, hotels and offices
Entertainment, light industrial and institutional occupancies
9,o
3,O
3,O 5,O 0,l x 0,l Occupancy class of building or floor zone
(description of room or floor use')
Minimum uniformly distributed imposed floor load, kN/m2
I
All rooms in a dwelling unit and a dwelling house including corridors, stairs and lobbies to a dwelling house
I
1
I
Bedrooms. wards, dormitories, private bathrooms and toilets in educational buildings, hospitals, hotels and other institutional occupancies
I
1.5 15ro
-4
'For uses not listed in Column 2, refer to 5.4.1.2.
+Offices where small printing presses, collating machines, etc., are installed. In the case of assembly areas with fixed individual seating, it is implied that a) the number of occupants is controlled, and
b) the removal of the seating and the use of the space for other purposes is improbable.
$Attention is drawn to the possible need to increase floor ioadings where compacted filing systems are used.
NOTE: Attention is drawn to the fact that it is possible for loading intensities to reach as much as 7 kNlm2 when large numbers of people are forced by panic or other urgencies to crowd together to the point where free movement is impossible and acute discomfort is experienced.
These extreme loadings would tend to be confined to limited areas in the vicinity of points of congestion such as exit gates, stair landings, subways or foot-bridges at railway stations. The highest prescribed crowd loading of 5,O kN/mz in the table is based on a more probable level of loading consistent with the philosophy that the code of practice loadings are not the maximum attainable values. It alSO takes
,cn
2 g
load of 7 kN/m2.
:a
$ 6
account of the history of satisfactory performance of public assembly buildings that have been designed for this level of loading in many countries. Where public assembly type structures are PartiCUlarlY sensitive to overloads (such as might be the case with light foot-bridges or temporary grandstands), the designer should consider designing or checking the relevant portions of the structure for an imposed
Load category
Area over which Minimum uniformly Minimum concentrated load concentrated load in distributed imposed (applied over the area
given in Column 5), kN Co'umn is to be floor load, kN/m2
Occupancy class of building or floor zone (description of room or floor use*)
applied, m 6 7 0 9
I
10
I
Corridors, stairs and lobbies to all buildings other than dwelling houses (where Category 1 applies)I
The same as the zone that they serve but not less than:Assembly halls, theatres, cinemas, sports complexes, grandstands, all with fixed individual seating Light laboratories
Sales and display areas in retail shops and departmental stores
Banking halls 4,O 5.0
Assembly halls, sports complexes, grandstands, all without fixed individual seating Stairs, corridors, landings and individual components of grandstands
Public and assembly areas of airports, railway stations, and terminals Stages to assembly halls, theatres and cinemas
Cantilever balconies accessible to the public
Filing and storage areas to offices, institutional occupancies, and hotels*
Shelved areas to libraries 5 0 Exhibition halls
4.0 3,O
5.0 3,O
5,O
0,l x 0 , l
11 Cantilever balconies, loggias and canopies irrespective of whether they are normally accessible to
the public or not than:
The same as the zone that they serve but not less
5.4.1.3 Partitions. Where provision is to be made for unlocated or movable partitions, allow for the following nominal imposed floor loads for such partitions, in addition to the loadings in Table 4:
a) Where the partitions have a weiaht Der unit lenqth not exceedina 3 kN/m and are SUDDOrted on a floor svstem with adeauate load-distributina DroDerties: An equivalent uniformly distributed floor load (in kilonewtons per square metre) of 0,5 times the weight per unit length of the partition (in kilonewtons per metre), but with a minimum of 1 kN/m2.
b) Where the Dartitions have a weiqht Der unit lenqth exceedina 3 kN/m: A series of line loads, spaced at a maximum of 2,5 m centres, placed in any position and direction and having a weight per unit length equal to that of the partitions.
Commentary:
For serviceability limit-states analysis, it is often only the permanent or long duration or regularly acting component of the imposed floor load that is of consequence, e.g. where creep deflection is a factor. The proportion of the nominal imposed load which may be considered as being of long duration varies with the type of usage. As a guide, the following proportions of the specified nominal distributed imposed loads may be taken as being of long duration:
Floors in the following:
Residential buildings; )
offices ; )
wards, corridors ancl theatres in hospitals;
schools; )
assembly buildings. )
) 0,3
Floors used for storage and floors in ) laboratories and in storage and ) 0,6
industrial buildings. )
Owners and designers are advised to give special thought to the possibility of later changes of occupancy involving loading heavier than was originally contemplated. They should not necessarily in every case select the lower loading appropriate to the first occupancy. In doing this, they may considerably restrict the use of the building at a later date, and thereby reduce its utility. Attention is drawn also to the possibility of temporary changes in the use of a building, as in the case of a dormitory being cleared for a dance or other recreational purpose and in the case of an institutional dining hall being used also as an assembly area.
5.4.2 Nominal Imposed Floor Loads in Buildinas Containina Storage and Industrial
OccuDancies
5.4.2.1 Storaae OccuDancv. Determine the nominal imposed floor loads in a building or in
part of a building, of storage occupancy, taking into consideration the type of stacked materials and methods of storage. Take into account the greatest volume of materials (or the greatest number of stacked articles) which can be located on the area of the floor under normal operational conditions of the warehouse, allowing for the densest stacking of materials and articles and the possible effect of the increase in density of some materials when stored for a long time. Allow for the weight of handling equipment, including the maximum load capable of being lifted. Ensure that the nominal imposed floor load adopted is at least 5 kN/m2.
(As amended 1993)
5.4.2.2 Industrial OccuDancv. Determine the nominal imposed floor load in a building, or in
part of a building, of industrial occupancy, such as a workshop, taking into consideration the weight of manufacturing plant, including
a) the weight of the plant,
b) the weight of the heaviest pieces under treatment or the weight of the maximum volume of the product being processed,
c) the weight of gangways and working platforms, d) the weight of handling equipment, and
e) loads resulting from necessary maintenance or replacement of stationary plant. Ensure that the nominal floor load adopted is at least
1) 3 kN/m2 for production rooms such as workshops with lightweight equipment
(benches, machine tools weighing not more than 5 kN each), and
2) 5 kN/m2 for production rooms such as workshops in works and factories.
See 5.4.3 for load reduction.
5.4.2.3 Dynamic forces. Make provision, where necessary, for the influence of dynamic
forces arising from operations with dynamically imbalanced equipment, from the shifting of heavy loads over the floor, or from falling or suddenly displaced goods in storage.
5.4.3 Load Reduction. The minimum uniformly distributed imposed floor load shown in
Column 3 of Table 4 or derived from 5.4.1.2 may be reduced as follows:
a) Where the tributary area of a floor, used for an assembly of persons or for storage, manufacturing or garaging, that is supported by a column or bearing wall (the cumulative area of all floors so supported being taken), or bya single span of a beam or girder, or by a single panel of a slab (solid or ribbed), or flat-plate, exceeds 80 m2, the distributed loading may, for the design of the building or of part of the building, be multiplied by a factor equal to:
0,5 +
-
4’5, but with a minimum value of 0,7where A = the tributary floor area that complies with the requirements of (c) below, m2
@
b) Where the tributary area of a floor, used for any purpose other than those in (a) above, that is supported by a column or bearing wall (the cumulative area of all floors so supported being taken) or a single span of a beam or girder, or a single panel of
a slab (solid or ribbed) or flat-plate, exceeds 20 m2, the distributed loading may, for
the design of the building or of part of the building, be multiplied by a factor equal to
0,3 +
g ,
but with a minimum value of 0,5@
where A = the tributary floor area that complies with the requirements of (c) below, m2
c) Provided that (in (a) or (b) above)
1) for one-way spanning slabs, the width of the tributary area does not exceed one-half of the span of such slab; and
2) for rectangular two-way spanning slabs, the tributary area does not exceed that of a square of sides equal to the smaller dimension of the rectangle.
