Design Load

Note: The source of the technical material in this volume is the ProfessionalEngineering Development Program (PEDP) of Engineering Services.

Warning: The material contained in this document was developed for SaudiAramco and is intended for the exclusive use of Saudi Aramcosemployees. Any material contained in this document which is not alreadyin the public domain may not be copied, reproduced, sold, given, ordisclosed to third parties, or otherwise used in whole, or in part, withoutthe written permission of the Vice President, Engineering Services, SaudiAramco.

Chapter : Onshore Structural For additional information on this subject, contactFile Reference: CSE10702 C.C. Baldwin on 873-2654

Engineering EncyclopediaSaudi Aramco DeskTop Standards

Design LoadsSaudi Aramco Building Code

Engineering Encyclopedia Onshore Structural

Design Loads Saudi Aramco Building Code

Saudi Aramco DeskTop Standards

CONTENTS PAGE

DESIGN LOADS 1

Design Loads in the Uniform Building Code 1

Basis of the Loads 1

Locating the Loads 1

When to Apply Structural Loads Data 1

Referring to the Base Document (UBC) 2

Saudi Aramco Modification to the UBC Design Loads 2

Basis of Aramco Modification to the UBC 2

Combined Loads 3

The Individual Loads Combined 3

Basis of UBC Wind Loads 8

EARTHQUAKE LOADS IN SAUDI ARAMCO 11

What They Are 11

How Earthquake Loads are Used 11

Seismic Load Factors Used by Saudi Aramco 11

Where to Get Additional Information 11

GLOSSARY 18



Saudi Aramco DeskTop Standards 1

DESIGN LOADS

The purpose of this module is to familiarize you with design loads found in the Saudi AramcoBuilding Code. This will include individual loads on structures, such as dead and live loads,wind and seismic loads, and combinations of these loads. The solution of specific designproblems does not apply to this module. For purposes of this module it is sufficient to knowthe various structural design factors that apply to your work and where you can locate thecurrent references so that you will be able to check existing designs for accuracy or calculatedata for new designs.

Design Loads in the Uniform Building Code

Basis of the Loads

Chapter 23, Part V (UBC) addresses and sets forth rules and formulas to deal with allprobable loads and combination of loads that may be encountered in the design of structuresthroughout the USA and its possessions.

Locating the Loads

Tables A through Q and Figures 1-2-3, pages 160-179 of the UBC represent all UBC loadswith numerical values and are presented so as to account for all individual structural loads forcombinations of structural loads. The different structural loads represented in these tables are:

Table Page Type of Load

23 A & B 160-163 Floor Loads, Dead and Live, Uniform and Concentrated23 C 164 Minimum Roof Live Loads23 D & E 165 Structural Members/Deflection23 F thru H 165 thru 167 Wind Loads23 I thru Q 168 thru 176 Seismic LoadsFigure 1 177 Basic Wind SpeedsFigure 2 178 Seismic Zone Map of USAFigure 3 179 Seismic Spectral Acceleration Graph

When to Apply Structural Loads Data

Structural loads data must be used whenever specified in the Saudi Aramco Building Code(SABC).

NOTE: Remember, the SABC is actually the UBC with modifications, as appear in SAES-M-100. To completely understand this relationship, read carefully SAES-M-100, p. 5,paragraph A.1. Take special note of lines 1-5.




Referring to the Base Document (UBC)

The procedure for researching the code is to:

(1) Enter the base document (UBC).

(2) Locate the desired data.

(3) Now enter SAES-M-100 (SABC) to see if there are modifications to base documentdata.

(4) Apply any modifications to base document data.

(5) Now use the modified base document data to satisfy your requirement.

Saudi Aramco Modification to the UBC Design Loads

Design loads are covered in the UBC, Chapter 23, Section 2301-2312. A review, however, ofSAES-M-100 (SABC) will show that a number of modifications have been created which takeprecedence over the related material in the UBC.

This means that if you are using loads data in the UBC you will actually follow the designrequirements which appear in SAES-M-100, pages 16, 17, 18, Part V, Chapter 23, Sections2303 through 2312(d)4, and Table 23A. (See SAES-M-100).

Basis of Aramco Modification to the UBC

If geographic and environmental conditions and operational factors in Saudi Arabia were thesame as in the USA, there would not have to be any modifications to the UBC. This is not thecase, however. Unique environmental conditions in Saudi Arabia and, in some cases,operational differences (in facilities, etc.), are two main factors which make it necessary tomodify the code so as to compensate for these unique conditions.

Some examples of this include Section 2311(b), Basic Wind Speed; Section 2311(c),Exposure; Section 2311(d), Design Wind Pressure; and, Table 23-A, Uniform andConcentrated Loads. (See SAES-M-100, pages 16 and 17.)




Combined Loads

The Individual Loads Combined

Every structural design will be subject to one or more conditions of loading. A combinationof loads will be factored into the design calculations and it must be determined that theapplicable loads to any design have been accounted for and that the loads have been selectedfrom the correct reference in the Saudi Aramco Building Code. The structural loads anengineer must be concerned with are: dead load , live load, wind load and seismic load .(See Figures 1, 2 and 3.) Knowledge and use of combined load factors is important so thatthe engineer may achieve the best combination of safety vs. efficiency and cost, in his design.

Dead Load Factor is determined by the vertical load due to the weight of all permanentstructural and nonstructural components of a building, such as walls, floors, roofs and fixedservice equipment. An example of additional dead load items contributing to the total deadload factor of a structure:

Roof mounted air conditioning unit(s)

Attic mounted air handling unit(s)

Upper floor mounted electrical or mechanical equipment

Live Load Factor is the load superimposed by the use and occupancy of the structure notincluding the wind load, earthquake load or dead load. Examples of live load factors on astructure:

Concentrations of people moving about on a structural surface i.e. floors,walkways, mezzanines, balconies

Movable industrial equipment on floors

Standing (ponding) water on roof




FIGURE 2




Wind Load Factor is calculated to compensate structural design for the effect of wind blowingagainst the structure. Every building or structure and every portion thereof must be designedand constructed to resist wind effects. Wind must be assumed to come from any horizontaldirection. Design stress values vary with:

Different structural shapes

Maximum wind speed values

Exposure factors

Seismic Load Factor is determined to ensure that as a minimum, structures and parts ofstructures shall be designed and constructed to resist the effects of seismic ground motions.This may involve horizontal and vertical motion. The importance of seismic effects uponstructural design cannot be overstated. The design considerations, criteria, and mathematicalformulas dealing with this phenomenon are found on UBC pages 140 through 159, andTables 23-I through 23 Q.

Major components of the wind that affect structures are:

1. Gusting

2. Vortex shedding

3. Sustained and transient, high and low pressure field

Combined loads that apply to structural design in Saudi Arabia are:

1. Yanbu area (dead, live, wind and seismic)

2. Eastern Province (dead, live and wind

See Figure 2, SAES-M-100, Sec. 2312(a).

Wind Load in Aramco. Wind loads for Saudi Aramco design purposes are unique to the SaudiArabian land lass. Saudi Aramco environmental services located in E-2000 providesofficial wind data for structural design purposes. This data is compiled from Saudi Arabianhistorical meteorology records.




Origin of Wind Data. Wind speeds appearing in the UBC for continental United States, Alaska,Hawaii and Puerto Rico are obtained from meteorology records of the past 50 years, whereavailable. Values listed are the fastest mile-per-hour speeds at 33 feet above ground level,maximum exposure category, and annual occurrence probability of 0.02%.

Since these wind factors are not relevant to the Kingdom of Saudi Arabia, a wind andexposure factor has been calculated for the entire Saudi Arabian land mass, based onhistorical observations during the last 50 years. (See SAES-M-100, p. 17.)

Basis of UBC Wind Loads

UBC wind loads are based on structural design vs. geographic location. If a geographic areahas a history of very light winds and there is less than 0.02% probability of stronger windsever occurring, it is clear that structures can be designed lighter and cheaper than in ageographic area where there is a 0.02% or better chance stronger winds will occur. (NOTE:SABC minimum 78 mph wind factor affects all Saudi Aramco structural design.)

The higher the probable wind load that must be factored into a design, the more costly thestructure will be.

You must confirm that a design meets the actual wind load risk, by locating and checking allavailable references which apply. (See 2311a-i, UBC, and ANSI A58.1.)

When to Use ANSI A58.1. ANSI A58.1 shall be the reference used when designing, or reviewingthe design of structures sensitive to dynamic effects, such as buildings with a height-widthratio greater than five, structures sensitive to wind excited oscillations such as vortexshedding, and buildings over 400 feet in height. At the engineer's discretion, any structuremay be designed by reference to ANSI A58.1. (See ANSI A58.1.)

NOTE: ANSI A58.1 deals with all structural load factors. However, Saudi AramcoBuilding Code (SAES-M-100), Sec. 2311(a), directs the engineer to referenceANSI A58.1 only with respect to wind loads.




Importance Factor. For the purpose of protecting essential facilities which must be safe andusable for emergency purposes after a windstorm, an additional stress allowance is specifiedfor structural design.

Structures specified in the UBC to receive an importance factor of 1.15 are:

1. Hospitals and other medical facilities providing surgical or emergency treatment areas.

2. Fire and police stations.

3. Municipal government disaster operation and communication centers deemed to bevital in emergencies.

4. Buildings where primary occupancy is for assembly use for more than 300 people.(See UBC P.13a, Sec. 23 11 (i).

In addition to the above four items, SABC modification calls for item 5 to deal specificallywith Saudi Aramco concerns, as follows:

5. All plant area buildings and all high rise buildings. (See SAES, page 17,Sec. 2311(i).)

Application of the 1.15 Importance Factor - It is now clear that we want to design strongerfacilities in the case of items 1-5 above; but the question is, how much stronger? A look atour importance factor of 1.15 tells us we must design fifteen percent (15%) stronger; but,where shall the extra 15% be applied?

Turn to page 138, UBC, and look at the design wind pressure formula (Section2311(d)).

In the formula P = Ce Cq qs I , the letter "I" designates importance factor.

This would show as P = Ce Cq qs 1.15 for any structures listed in 1-5 above.

For all other buildings the formula is P = Ce Cq qs 1.0 . (See page 139, UBC, Section2311(i), last line.)

Since wind speed and wind pressure values in the UBC have no validity for SaudiArabia, the values to be used in structural wind pressure computation will be as shownin SAES-M-100 modification (p. 17), of

UBC Section 2311 (b) 78 mph All of Saudi Arabia

UBC Section 2311 (d) 16 PSF All of Saudi Arabia




A definition of location/exposures factors is found in the UBC, p. 2311(c).

An exposure shall be assigned at each site for which a building or structure is to bedesigned. Exposure C represents the most severe exposures and has terrain which isflat and generally open, extending one-half mile or more from the site in any fullquadrant. Exposure B has terrain which has buildings, forest or surfaceirregularities 20 feet or more in height covering at least 20 percent of the areaextending one mile or more from the site.

Since the location/exposure factor for all of Saudi Arabia has been established as aconstant, the value to be used in all structural design considerations is as shown inSAES-M-100 modification (p. 17) of the UBC Sec. 2311(c), "Exposure C shall beused."




EARTHQUAKE LOADS IN SAUDI ARAMCO

What They Are

Earthquake loads in Saudi Aramco are load factors specified in the SABC to protect structuresin earthquake zones. If a location does not merit a seismic zone factor with a numericalvalue, it is permissible to design without consideration of seismic loads.

How Earthquake Loads are Used

Earthquake loads are calculated, when applicable, to determine design technique, materialsand strength so that structures will resist the effects of seismic ground motion.

Seismic Load Factors Used by Saudi Aramco

SAES-M-100 addition to UBC Sec. 2312(a) states that "Seismic loads are not applicable toAramco Eastern Province operating areas. Seismic loads, Zone 1, are applicable to the YanbuNGL plant installation and to the Royal Commission tract at Yanbu."

Where to Get Additional Information

SAES-M-100, addition to UBC 2312(a) states, "For areas other than the above-mentioned, theManager, Consulting Services Department, shall be contacted for a definition of the seismiczone prior to start of design. (See SAES-M-100, p. 17.)




FIGURE 4




MICROFICHE READER/PRINTER OPERATION

STEP 1. TURN ON THE POWER SWITCH.

STEP 2. RAISE FICHE CARRIER UNTIL THE GLASS PLATES SEPARATE.

STEP 3. PLACE MICROFICHE IN, RIGHT SIDE UP, AND BACKWARDS.

STEP 4. LOWER GLASS DOWN ONTO FICHE.

STEP 5. FOCUS IF NECESSARY.




FIGURE 6




FIGURE 7

STEP 1. TURN ON THE POWER SWITCH.

STEP 2. INSTALL CARTRIDGE IN RECEPTACLE.

STEP 3. ALLOW MACHINE TO AUTOMATICALLY FEED FILM INTODRIVE MECHANISM.

STEP 4. FOCUS IF NECESSARY.

NOTE: Ask Librarian for detailed instructions as needed.




FIGURE 8




FIGURE 9




GLOSSARY

dead load The vertical load due to the weight of all permanent structuraland non-structural components of a building, such as walls,floor, roofs and fixed service equipment.

gusting Sudden, brief burst of wind, blowing with strong force at randomintervals.

importance factor An additional strength factor applied to buildings which arecritical to community health, safety and security.

live load The load superimposed by the use and occupancy of thebuilding, not including the wind load, earthquake (seismic) loador dead load.

microfiche A folder in the TIC that resembles a ring binder. It is fitted

pocket file with interior pockets which contain the microfiche transparenciesfor all existing Saudi Arabian Standards (SSA).

ponding Rainwater which collects in low spots on flat roofs, formingsmall lakes or "ponds" which impose considerable additionalload on the roof areas where the water collects.

seismic Motions, movements, and vibrations of the surface layers of theearth.

seismic load The forces acting upon a building or other structure due toeffects of seismic (earthquake) ground motions.

vertical carousel track A special rack in the TIC for the storage of microfilm cartridges.It is approximately five feet high, rotates on a vertical axle andcontains a large number of cartridges.

vortex shedding Wind created vortices (eddies) on alternate sides of a structure(tall chimney, suspension bridge, very tall building, etc.) If thefrequency of vortex shedding approaches the natural frequency(oscillation period) of the structure, the alternating buffeting willcause it to suffer dangerously large vibrations.

wind load The forces acting against a building or other structure from windcoming from any horizontal direction.

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Design Load