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400 Small Buildings

AbstractSection 400 gives civil engineers, and other engineers working outside their displine, design and construction guidelines for typical, pre-engineered, steel, masonry, and blast-resistant buildings. It includes both Company-designed builings and contractor-designed structures. The primary emphasis is on the civil astructural aspects of buildings. Building material (other than structural), architectural treatments, and electrical, lighting, and mechanical systems are not coverApplicable codes and industry standards are referenced, as well as standard drings of blast-resistant building details.

Contents Page

410 Background and Basic Data 400-2

411 Industry Codes, Practices, and Guidelines

412 Design Considerations

413 Layout and Design Considerations

420 Building Shells 400-12

421 Metal Building Systems

422 Bearing Wall Construction Systems

423 Curtain Wall Construction Systems

424 Concrete Block Construction

425 Roof Designs

430 Blast-Resistant Design 400-21

440 Safety Storage Buildings 400-28

450 Model Specifications and Standard Drawings 400-29

451 Model Specification

452 Standard Drawing

460 References 400-29

Chevron Corporation 400-1 June 1997

400 Small Buildings Civil and Structural Manual

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410 Background and Basic Data

Industrial BuildingsFor purposes of this section, industrial buildings include, but are not limited to, tfollowing:

• Locker Rooms• Shops• Storehouses• Guard Houses• Equipment Shelters• Electrical/Electronic Equipment Enclosures• Small Operations Offices

Administration, control houses, and laboratory buildings are normally architectually designed and are not addressed in detail in this section. Blast-resistant dessuch as that used for control houses, is discussed in Section 430.

411 Industry Codes, Practices, and GuidelinesListed below are the primary codes and industry standards that govern the desand construction of small industrial buildings. Most communities have minimumbuilding requirements, usually adapted from codes established by regional orgations. It is important to review local code requirements to ensure that designs aconformance.

The latest edition of the applicable codes should generally be followed. Howevedesigners should be aware that local communities commonly adopt regional coby dated edition. Changes that appear in subsequent code editions may or maybe recognized.

Industry Codes

Other Codes and StandardsUniform Plumbing Code (UPC)

National Electric Code (ANSI/NFPA 70)

Minimum Design Loads for Buildings and Other Structures (ASCE 7-93)

Uniform Mechanical Code (UMC)

Building Codes Primary Areas

UBC Uniform Building Code Midwest, West, West Coast

BBC Basic Building Code North, Northeast, Midwest

SBC Southern Building Code South, Southeast

National Building Code of Canada Canada

June 1997 400-2 Chevron Corporation

Civil and Structural Manual 400 Small Buildings

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National Fire Code (NFPA)

American Institute of Steel Construction Specification for the Design, Fabricatioand Erection of Structural Steel for Buildings (AISC)

American Concrete Institute Building Code, Requirements for Reinforced Conc(ACI 318)

American Society of Heating, Refrigerating and Air-Conditioning Engineers Habook Series (ASHRAE)

Metal Building Manufacturers Association (MBMA)

Building PermitsIt is common practice for city or other local governmental units to require a building permit prior to start of construction. It is good practice to determine earin a building project the following information:

• Building permits required

• Documentation required with a request for permit

• Applicable code requirements and special local requirements, if any

• Applicable code classification for building by use or occupancy. Request comation by local jurisdiction

• Timing considerations

– When submitted– How long for review and approval process

• Local inspection required and at what construction hold points

412 Design Considerations

Design MethodsThere are two basic methods by which the Company proceeds with building designs:

• Company completes in-house design

• Company prepares preliminary design with final designs completed by an outside consultant or with design/construct contract

The size and complexity of the building usually determines which method is chosen. Company designs are generally limited to structures that are constructbasic building materials and usually do not require mechanical systems such asHVAC or special interior or exterior architectural treatment. Examples of possibCompany-designed buildings include:



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• Pre-engineered building structures used for storage, small shops, small labequipment shelters, or temporary construction offices or facilities

• Small masonry structures with limited functions, such as remote area oper-ator’s office, toilet facilities, or equipment shelters

Most other building designs would generally be contracted for design outside thCompany. To increase the designer’s efficiency, it is recommended that in-houspreliminary layouts be developed first. This is not intended to restrict the architeto a particular arrangement, since creative thinking by the architect should be encouraged to achieve a design that is functional, visually pleasing, and econoical. The purpose of the preliminary layout is to:

• Define the scope for the job and required facilities• Give the architect an understanding of how the building is to function• Show how the occupants of the building need to interact

Site ConsiderationsRegardless of the method chosen to execute the building design, the following information on the proposed site must be developed in the preliminary planningphase:

• Size and configuration of site• Site topography• Access by vehicles and pedestrians• Proximity to other buildings/facilities• Building orientation considerations• Special site restrictions, minimum clearances• Access to utility services• Soils, groundwater, drainage, possible subsurface contamination informatio• Other space requirements (parking, outside storage)• Requirements for matching architectural style and treatment of existing nea

buildings.

413 Layout and Design ConsiderationsFigure 400-1 provides guidelines for the layout and design of some typical indutrial buildings. Facilities listed include:

• Small offices• Lockers/toilets• Storehouses• Shops• Electrical equipment• Control houses



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Sometimes these structures are designed as separate buildings; frequently, howthey are combined with other facilities within a single building. The following sizlayout, and design considerations will be applicable for both cases.

Fig. 400-1 Building Function, Size and Design Considerations (1 of 6)

Building Function: Small Offices

Size Considerations Design Considerations

Possible facilities: • Combine various functions where possible. For example, training/conference room. Or, by using accordion-type wall divider, a training room and lunchroom could be combined.

• Fully understand the intended building functions.

– Importance of building appearance

– Advantages/disadvantages of multi-storied construction

– Importance for occupants being able to observe specific areas or activities

– Consider difficulty of maintaining building condi-tion because of heavy traffic or work-related environment

• Provide adequate HVAC and insulation.

• Select building structural framing system and dimensions to suit proposed layout.

• Interior partitions can usually be arranged to accommodate columns without obstructing access.

• Building evacuation requirements.

• Office(s)

• Training/conference room

• Toilets/locker room

• Safety locker

• Kitchen/lunchroom

• Switchgear room

• Mechanical room (HVAC)

• Handicap access and facilities

• Medical treatment

• Waiting area for visitors

• Building support services

– Janitor

– Copy

– Storage

– Computer room

– File room



Building Function: Change Houses (Lockers, Showers, Etc.)


• Size determined by number of employees using the facilities:

• Dual facilities for men and women employees.

• Size of lockers based on type of clothing stored.

– Overalls and special clothing requires full length locker.

– For other clothing half-size lockers may be appropriate to reduce space requirements.

• Provide means for positive ventilation through the individual lockers.

– Provide adequate water heating capacity with quick recovery.

• Access for personnel in and out and security considerations will influence layout.

• Employee parking facilities will influence building location.

• Consolidate arrangement of toilet/shower facilities to reduce cost of water supply and waste water plumbing systems.

• Pay careful attention to the materials specified for ceilings, walls, and floor. They should be selected for ease of cleanup, maintenance, and durability.

• Provide adequate HVAC for environmental condi-tions.

– Locker number based on total employee requirements

– Toilets, showers, etc., based on maximum at shift changes

– Number of facilities provided generally based on code requirements (Reference 1) specifies minimum fixture requirements

– May require substantial mechanical room for housing air handling and water heating equip-ment

– Allow for future growth.

• Extra space

• Provision for building expansion

• Special change rooms sometimes required to separate work clothes from street clothes.




Building Function: Storehouse


Possible facilities: • Location considerations:

– Convenient for outside truck deliveries without entering plant areas.

– Convenient for in-plant material pickup.

– Rail siding and unloading if service is available.

• Material receiving and distribution:

– Truck/rail loading docks

• Building security

• Floor slab designed for heavy industrial loading.

– Fork lift truck use

– High unit loading from material storage

• Adequate outside space available for outside storage and reclamation.

• Heating, ventilation, and A/C as required for offices and special materials storage.

• Doors with adequate width and height for material handling.

• If exterior walls are metal, consider ways to protect from physical damage. For example use masonry or concrete for lower 5 feet to 6 feet.

• Select building structural framing system and dimensions consistent with proposed layout. For example, match column layout with forklift traffic patterns.

• Fire protection requirements for chemical and other combustible material storage areas.

• Toilet/locker room(s)

• Offices

• Conference room

• Space for files

• Kitchen/lunchroom

• Special Storage

• Waiting area for outside visitors

• Truck unloading/receiving area. Issue area for storehouse materials

• Special storage areas with controlled environment




Building Function: Shops


Possible facilities included: • Material/equipment handling.

– Overhead bridge crane(s)

– Jib cranes

• Understand progression of equipment through shops to minimize handling time.

• Floor slab designed for heavy industrial loadings.

• Adequate ventilation.

• Heat and A/C as required for offices.

• Environmental control for electronic/instrument shops.

• Doors adequate in width and height for material and equipment handling.

• Provision for protection of building exterior wall panels from physical damage.

• Adequate outside space for work areas or equip-ment/materials storage.

• Location of building columns must suit proposed layout of facilities.

– Provide adequate lighting. Note fluorescent lighting can be a problem around rotating equip-ment.

• Specific shop facilities required

• Lockers/showers/toilets

• Offices

• Tool room(s)

• Shops storehouse

• Lunchroom/kitchen




Building Function: Electrical or Electronic Equipment Enclosures


• Equipment sizes • Located as required for area served.

• Buildings are normally unoccupied.

• Ventilation and humidity control may be critical considerations.

• May require pressurization to meet desired elec-trical area classification.

• Air intakes must be located to provide clean air source.

• Careful planning is required for conduit entries.

• Provision for moving equipment in and out.

• Provide ample allowance to meet code safety clearances and working clearances in preliminary layouts. Actual size of equipment furnished may be larger than planned.

• Consider having MCC supplier furnish the building; for example, a complete prefabricated unit including installed MCC units.

• Code clearances

• Allowances for future equipment

• Allowances for maintenance work on equipment.




Building Function: Control House


• Possible facilities: • Underfloor space (basement) often serves as air return and passage for routing of electrical/instru-mentation cables. Use vapor barriers, seals, and allow absolute minimum openings to assure dryness. Conduit bank entrance is major source of water entry. A block and bleed double entrance may be required.

• Underfloor drain lines must be adequately supported. Welded steel pipe rather than cast iron may be best material.

• Laboratory facilities, a common internal fire hazard, should be isolated from the rest of the building with a floor to ceiling solid wall and sepa-rate exterior entrance.

• Construction materials should be reviewed with Health, Environment & Loss Prevention.

• Non-essential personnel should not be located in the control house.

• Electrical/instrumentation racks and panels should be securely anchored to prevent overturning during an earthquake or blast.

• If structure is designed for blast resistance, consider independent blast-resistant walls outside exterior doors to attenuate blast pressures acting on doors.

• Positive internal pressure maintained to keep hazardous vapors out.

• For computers (see also ICM-MS-3651, Control House Environment for Digital Instrumentation and Process Computers):

– Adequate HVAC

– Air filter system

– Humidity control

– Uninterruptible power system

– Raised (“access”) floor or trenches

– Fire extinguishing method

– Control room

– Computer room

– Kitchen area/lunch room

– Toilets

– Lockers

– Offices

– Access area to instruments

• Provide adequate allowances for structural member sizes, and for number (spacing) of columns. Changes after other designs have started become difficult to make.

• Air handling ducts tend to become very large. Consider these early as they may influence building dimensions.

• Get a clear agreement about provision for future expansion of the building. Can influence structural framing and components.




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Preliminary Building Layout StudiesThe following guidelines are suggested for proceeding with preliminary buildinglayouts.

• Define offices and facilities to be provided. This requires input from the useorganization.

• Define preliminary space requirements for the proposed facilities. Review osimilar building facilities provides helpful guidelines.

• Include in the space studies adequate area for building support services:

– Entrances– Mechanical equipment– Stairs (if required)– Toilet (locker) facilities– Copy room– Storage– Janitorial facilities

• Determine user preferences for interrelationship between various offices anfacilities, i.e., offices that should be grouped together or facilities that may (should) be segregated.

• Study the advantages/disadvantages and acceptability of the following basbuilding concepts:

– Single level– Two level– For structures with high vertical clearances (shops or storehouse), the

of partial mezzanine area

• If offices are required for the building, be aware there are Corporate guidelifor space allocation based on job placement:

Information on current office space standards may be obtained from either the Company’s manual, entitled Office Standards, or from Chevron Real Estate Management Company (CREMCO) in San Francisco.

• In starting preliminary building layouts, it is important to have a general concept in mind for possible framing systems. This is particularly true if interior columns may be required.

Approximate Range (in usable square feet)

Private Office 115-150

2-Person 180-225

Clerical Offices 90

(includes space for aisles, normal files, and equipment)



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• For preliminary layout, studies begin with single line arrangement sketchesConsider a number of alternative arrangements, for this will help in the layoreview process.

Review of Preliminary LayoutsThere are two fundamentals to be kept in mind when planning building layouts:

1. It is human nature for every individual reviewing building layouts to offer suggestions. Relative to other Company endeavors, there is more input conuted from all levels to the planning of building layouts. Sorting through this information is important, as excellent suggestions and ideas come out of threview process. The level of user acceptance and satisfaction relates direcconsideration of their input.

2. Individuals reviewing preliminary layouts frequently are unable to articulatewhat they really want or like. They are, however, able to recognize, even invery rough preliminary layouts, the things they don’t like or arrangements thdon’t appear to work. It is sometimes helpful, therefore, to have a number oalternatives prepared when starting the review process.

420 Building ShellsBuilding shells by definition include framing systems, exterior walls, and roof systems for buildings. All interior work, room dividers, and mechanical and electrical systems are not included. In this section the following examples of buildinshells are discussed:

• Metal building systems• Bearing wall construction• Curtain wall construction with independent framing system• Concrete block construction

421 Metal Building SystemsMetal building systems, also called “pre-engineered” or “prefabricated,” have wapplication for use as industrial buildings. They are available as a complete encsure with a structural steel frame, with prefinished metal roof and wall panels, aare generally site-assembled. See Specification CIV-MS-4796, Pre-EngineeredMetal Buildings, included in the specification section of this manual.

Building FramingManufacturers of the pre-engineered building systems generally offer four basictypes of framing systems or some combination of these types.

See Figure 400-2 through 400-5 for illustration of these framing systems:

• Rigid frame—for column-free interior space• Single slope for economic designs



• Beam and column—for wider span structures• Truss—for heavy suspended loads and high building heights

Fig. 400-2 Rigid Frame Metal Building

Fig. 400-3 Single Slope Metal Building



Fig. 400-4 Beam and Column Metal Building

Fig. 400-5 Truss Metal Building



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Pre-engineered metal building systems generally use the manufacturer’s standwall and roofing system to achieve cost-effectiveness and the best performanceThe walls and roofs are generally assembled with large prefinished panels withwithout insulation. The panels are usually ribbed or corrugated for strength andprovide interlocking of panel sections.

For advantages/disadvantages and typical applications for metal building systerefer to Figure 400-6, Building Construction Comparison.

Division of ResponsibilityIn addition to furnishing the building components, the manufacturers of pre-engneered building systems normally furnish the following as part of the purchase order:

• Building drawings (building shell only)• Anchor bolt pattern and schedule• Foundation loadings• Required special foundation details to suit building• Erection drawings, details, and specifications

The purchaser of pre-engineered building systems normally provides:

• Detailed foundation and floor slab design drawings• All interior design and construction (walls, partitions, ceilings, etc.)• All mechanical, electrical, and lighting systems• Special architectural treatment materials, such as masonry exterior walls• All field installation labor and equipment

To take advantage of prefabricated building construction, the purchaser shouldallow flexibility in building dimensions of plus or minus several feet so that the manufacturers can use their standard designs.


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Fig. 400-6 Building Construction Comparison

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Storehouse facilitiesShop facilitiesTemporary construction facilitiesUnoccupied equipment sheltersChange houses

Occupied buildings:

OfficesControl houses LaboratoriesFire protection buildingsSecurity buildingsChange houses

Building Construction Advantages Disadvantages

Metal Building Systems(pre-engineered/prefabricated)

Design costs can be reduced because the structure is made up of pre-engineered standard building components, frames, purlins, wall girts, bracing, siding, and roofing.

Time to complete an installation is reduced because of short design period, fast material delivery to the site, and quick erection time using all prefabricated components.

Available In many structural frame configurations and a large range of dimensions, and available for different design loadings.

Buildings come complete with gutters, exterior trim, standard doors and windows, wall and roof ventila-tion, and insulation as specified by purchaser.

The appearance is generally not as attractive as architect-designed buildings where a wide choice of materials is available and a more pleasing architectural rendering canbe developed. this disadvantage canbe partially offset by supplementaryuse of other more decorative mate-rials to provide some architectural rendering.

Pre-engineered wall panels used in shops or storehouse activities are subject to damage from equipment omaterial movement. this kind of damage can be difficult to repair or replace. the use of masonry for wallsections subject to damage will reduce this problem.

Building layouts and configuration are limited to the standard sizes avaable from manufacturers.

Bearing Wall And Curtain Wall Construction

Provides a more permanent and attractive appearance than metal building structures.

Provides greater flexibility In layout options.

Curtain wall construction can be used for multi-storystructures.

Bearing wall construction generally limited to single story buildings with smaller dimensions

Requires more design time to selectand detail all structural componentsand other architectural detail.

Cost is higher than prefabricated metal building systems.


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422 Bearing Wall Construction SystemsIn bearing wall construction systems, the roof assembly acts as a unit to transfegravity and lateral loads to the bearing walls.

Walls transfer all vertical and lateral loads to the foundation with primary stressbeing compression and shear.

Basic Types

Framed. Usually site assembled. Wood or metal studs with structural sheathingdiagonal bracing. Interior and exterior finishing compatible with stud constructio

Masonry. Site assembled with stacked masonry units (concrete block or brick); vertical and horizontal reinforcing as required. See Section 424.

Cast-Concrete. Includes cast-in-place, tilt-up, and precast construction

Refer to Reference 3 for the following information on bearing walls:

• Distribution of loads• Types and properties• Compatible floor and roof framing systems• Load-bearing capacity• Exterior and interior facings• Selection considerations• Wall insulation• Wall details

Roof deck systems for buildings with bearing wall construction are commonly constructed with bar joists, precast tees, hollow core planks, or metal deck panwith lightweight concrete, gypsum, or rigid insulation. Hot-applied built-up roofinis commonly used to provide a watertight barrier.

Refer to References 3 and 9 for information on alternative systems and materiainsulation, membranes, and construction details.

423 Curtain Wall Construction SystemsCurtain walls are perimeter wall panels which carry their own weight and transflateral loads to a structural frame. Gravity and live loads on the structure are cato the foundation by an independent structural framing system of steel or concrExamples of curtain wall systems include:

• Sandwich-type insulated panels of steel or aluminum• Precast concrete• Single thickness panel (formed metal panels with corrugations or ribs)

Roof decks for curtain wall construction use systems similar to those describedbearing wall construction.



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For additional information on curtain wall construction refer to References 3 and

424 Concrete Block ConstructionThis section discusses the design and recommended details for reinforced andinforced hollow unit masonry bearing walls. Model Specification No. CIV-MS-94covers concrete block construction.

DesignDesigns are usually made in conformance with:

• ACI 531—Building Code Requirements for Concrete Masonry Structures• UBC—Chapter 24• Other jurisdictional codes

Design Strength of MasonryThe compressive strength for concrete masonry includes both the mortar and thmasonry unit itself. If a significant amount of block masonry construction is involved, it might be desirable to establish allowable stresses based on standarcompression tests using the same masonry and mortar materials to be used in structure. For most work, however, designs are based on assumed ultimate comsive strength given by code. This results in allowable stresses that are intentionconservative.

The codes recognize that the quality of workmanship is critical to the integrity othe masonry structure. For example, ACI 531 states that without engineering orarchitectural inspection to ensure quality control of materials, construction, andworkmanship, allowable compressive stresses are reduced by one-third and shand tension by one-half.

For loadings due to wind or earthquake, a one-third increase in allowable stresspermitted.

Hollow Block MasonryMasonry units are usually furnished to ASTM C90. There are two grade designtions used by C90 (and also in UBC Standards).

For general use on Company construction, load bearing hollow block concrete are specified as Grade N-I (general-use blocks with moisture control) with a spefied minimum compressive strength on the average net area of 2100 psi.

Moisture control of the masonry unit is important for attaining the desired strengof masonry construction.

• Grade N For general use in exterior walls above and below grade

• Grade S Limited to use for interior walls or above grade in exterior walls with weather-protective coating



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• If the masonry unit is too moist, it will not draw out sufficient moisture from the mortar to achieve a good bond between mortar and unit

• If the masonry unit is too dry, it will draw out moisture too rapidly from the mortar which will reduce the strength and bond of the mortar

ASTM C90 establishes moisture-content requirements for masonry units. Maximum moisture-content is specified for three different job site humidity condtions: humid, intermediate, or arid. Masonry with or without moisture control is designated as Type I or II respectively.

ReinforcementFigure 400-7 illustrates typical wall reinforcement for load bearing reinforced concrete masonry.

In Seismic Zones, all walls shall be reinforced with both vertical and horizontal reinforcement. The sum of the areas of horizontal and vertical reinforcement shbe at least 0.002 times the gross cross-sectional area of the wall, and the minimarea of reinforcement in either direction shall not be less than 0.0007 times the gross cross-sectional area of the wall. The spacing of reinforcement shall not exceed 4 feet.

Horizontal wall reinforcement must be provided at top of foundations, top and bottom of wall openings, and at roof levels.

Vertical reinforcement should be provided on each side of openings, at intersections, ends, and corners.

Example for Determining Reinforcement Spacing8 in. thick wall

8 ft high

(8 in.) (8 ft) (12 in.) = 768 in2

AT = 0.002 (768) = 1.536 in2

0.0007 (768) = 0.538 in2

Use three No. 4 bars horizontally

AH = 0.60 in2 > 0.538 in2 OK

AT - AH = 1.536 - 0.6 = 0.936 in2

AV ≥ 0.936 in2. Use five No. 4 bars.

AV = 1.00 in2 >0.936 in2 OK

Spacing (8 ft.) (12 in.) ÷ 5 = 19.2 in.

Say 16 in. to match cells.

See References 1, 8 and 9 for more information in the design of reinforced mas



Fig. 400-7 Masonry Wall Construction



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Control JointsControl joints are continuous vertical joints built into masonry walls to aid in controlling wall movements. Control joints in walls should be located over any control joints in the foundation. The maximum spacing for control joints is discussed in ACI 531.

425 Roof DesignsThe advantages for flat roof systems and sloped (pitched) roof systems are:

430 Blast-Resistant DesignControl houses or other buildings housing personnel and control equipment neaprocessing plants are sometimes designed with a level of blast resistance. Theis to protect personnel and critical control systems for facilities to permit an ordeshutdown and prompt recovery after an accident.

The decision to design for blast resistance is made by the project design team consultation with the CRTC Process Risk Team. Generally, blast-resistant desigshould be considered when the building or control house:

1. serves two or more refinery process plants

2. serves one major plant that processes large volumes of volatile and flammliquids and gasses

3. must be located closer to the plant than the recommended minimum spacin

4. is adjacent to LPG or Pentane above flash temperature and greater than 2psig

Blast-resistant design may not be necessary if the building is far enough from thpotential source of a blast, even if it meets conditions 1 or 2 above. Consult theFire Prevention Manual or the Process Risk Team for guidelines on control house loctions.

Design Blast LoadsIn the rare event of a Vapor Cloud Explosion, (VCE), and fire in a process plantcontrol house can be damaged, not only by fire itself, but by:

Flat Sloped

Is not subject to wind forces (or in the case of blast-resistant design, to reflected overpressure forces).

Roof drainage is better and more easily directed. Can be used for longer spans without interior columns.

Is architecturally more pleasing than a highly pitched sloping roof.

Snow and ice may be less of a problem. Generally can be a more economical structural design.



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• overpressure resulting from the ignition and explosion of flammable materiathat has escaped into the atmosphere, or

• overpressure or missiles from runaway reactions.

When a VCE occurs, there is a violent release of energy that causes a sudden sure increase in the surrounding atmosphere. This pressure disturbance, terme“blast” or shock wave is characterized by an almost instantaneous rise from norpressure to an overpressure condition. This high pressure shock front, with a veshort duration (expressed in milliseconds), expands outward from the center ofblast. The shock wave intensity decays with distance and as a function of time.measured pressure at a given point exhibits an instantaneous increase in overpsure from atmospheric to a peak overpressure value as the shock wave reachepoint. The overpressure then decays rapidly, followed by a period of negative psure.

If the shock wave impinges on a rigid surface, such as wall, the propagation of wave is obstructed. This results in a rapid increase in pressure against the walan amount far greater than the overpressure, this is termed Reflected Overpresure. There are several ways to estimate the peak reflected overpressure. Forrange of peak overpressure used for blast resistant building design, reflected psure will be higher by factor of from 2 to 2.5.

The shock wave will also generate drag pressure onto the building. Drag pressis due to air movement associated with the shock front moves at high velocity. convenience, and without much risk of error, this velocity is generally assumed be the same as the shock-front velocity. This “wind” produces drag forces on aobstacle in its path which are combined algebraically with peak overpressure fo

Figure 400-8 illustrates the sequence of events as the shock wave passes overangular enclosed structure.

The magnitude of the blast overpressure at a building is a function of the follow

• Size of the flammable vapor cloud.

• Material of the cloud. Higher reactive materials include: hydrogen, acetylenethylene oxide and propylene oxide. Lower reactive materials include: methane and carbon monoxide.

• Level of equipment and piping congestion in the vapor cloud.

• Area of confinement for the vapor cloud.

• Distance of the building from the Vapor Cloud Explosion.

Use Figure 400-9 as a guideline to determine the design overpressure load if yoare considering a blast-resistant building. Figure 400-9 shows the effects of ovepressure and duration on a building as a function of distance from source unit size of the unit. The analysis assumes a typical facility and the blast may be covative in many cases. However, a site specific hazard assessment can be donethe CRTC Process Risk Team to provide a more accurate determination of the loading.


Civil and Structural Manual

400 Small Buildings

Chevron Corporation400-23

June 1997

F
ig. 400-8 Reaction of Rectangular Structure to Explosion Shockwave

400 Small Buildings

Civil and Structural Manual

June 1997400-24

Chevron Corporation

Fig. 400-9 Design Blast Loads for a Building (Side-On Overpressure)


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Structural SystemsBlast-resistant buildings should normally be clad with reinforced concrete or othductile material. Roofs should be of reinforced or prestressed concrete or of composite construction utilizing steel decking and concrete. Framing systems which may be required to support walls or roofs may be of reinforced concrete structural steel. Where reinforced masonry or prestressed concrete is used, theenergy absorption capacity of each structural element up to the point of collapsshould exceed twice that required to resist the design blast loading.

In view of the very large design loads for blast conditions, interior columns are normally provided when roof spans exceed 30 feet. Equipment and interior parttions can usually be arranged to accommodate these columns without obstructaccess within the building.

Structural DesignThe intent of the structural design is to accept moderate structural damage to thbuilding while still maintaining protection for personnel and control equipment. Some distortion of the building structural elements and external doors may occblast loadings even less than the specified design load. No special provisions nbe made to protect items such as exterior lights, gutters and roof drains, antennand landscaping. The number of these items should be minimized as they maybecome dangerous projectiles in the event of a blast.

For design purposes, it is assumed the explosion occurs as a surface burst andreflected loads are imposed on the roof.

It is assumed the explosion can be omnidirectional with respect to building orietion. This means that all faces of the structure should be designed for the full reflected overpressure. The assumed explosion locations are taken perpendicuthe center of the building walls.

In addition to being subjected to an overpressure condition from a blast, there mbe impacts against the building from high velocity debris. The subject of missileimpact is not addressed here because typical control house building materials (as reinforced concrete) offer excellent properties for resisting missile penetratio

Static Load Equivalent of Blast PressuresRequired dynamic resistance in the direction of blast loads shall be calculated iaccordance with the procedure outlined in ASCE Manual 42 [11], which takes iaccount dynamic response of the various structure elements.

The equation for this calculation relates the peak blast load (either incident or reflected) to the actual required dynamic resistance, which is actually an equivastatic load. The equation takes into account each element’s ductility and funda-mental period of vibration in the direction of load. The ratio of blast load duratioto period of vibration is also used in the relationship.

The required resistance may be as much as twice the peak blast force for a palarly brittle structure subjected to a long duration loading, or just a fraction of thpeak force for a ductile structure subjected to a short duration loading.



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This pseudo-dynamic procedure provides a uniform margin of reserve strengththroughout the structure and therefore gives a more uniform factor of safety agacollapse for all elements in the structure, a provision not satisfied by using a uniform static load over all the structural elements.

The intent is to design a ductile building, with each element capable of carryingdesign loading in relation to that element’s stiffness. The dynamic material strencapacity of any structural element should be determined according to the plastidesign method for structural steel and the ultimate strength method for reinforcconcrete as provided by AISC Specification and ACI Standard, respectively.

Alternately, a dynamic analysis procedures for the petrochemical facilities is described in ASCE Task Committee Report, “Design of Blast Resistant Buildingin Petrochemical Facilities”. The overall objective of a dynamic blast analysis to assess the capability of a structure to resist a specified blast load. A resistanfunction, or applied force versus displacement relationship, is developed basedassumed failure mechanisms, the member configuration and estimated sectioncapacities. The analysis will provide maximum relative deflections of each strutural elements, and relative rotation angles at plastic hinge locations. The desigcan proceed to determine the adequacy of the member through the applicationthe acceptance criteria.

Consult references [11], [13], and [14] for the detailed design procedure. The CRTC Civil and Structural Team can provide guidance on blast resistance desigand analysis of the structural system.

Load CombinationsThe required dynamic resistance to blast loads should be combined with other as follows:

U = D + L + R

where:U = total required structural resistance

D = dead loads, or their related internal moments and forces

L = applicable live loads, or their related internal moments and forc

R = required dynamic resistance to blast loads (or rebound)

Required rebound resistance, such as for roofs, should normally be consideredcombination with dead loads only.

Resistance to blast loads should not be considered in combination with wind orearthquake.



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Rectangular box-shaped buildings should be designed for blast pressures giventhe guidelines below.

FoundationsIt is generally not necessary to increase the size of the foundation in order to limthe soil bearing pressure in the vertical or lateral direction for blast loading. Thevery high bearing pressures which may be generated can be accepted becausehigh strength of soils under rapid loading and the high inertial effects when soilsare accelerated. In general, dynamic soil bearing pressures are between 1.5 antimes greater than the allowable soil bearing pressure for operating loads.

Pile-supported buildings should be designed structurally to transmit the verticalloads to the underlying soils using the ultimate strength of the pile. For timber pthe ultimate strength may be computed by multiplying the cross section area ofpile at the butt by the dynamic compressive strength, which is taken as twice thnormal static ultimate compressive strength. It is not necessary to increase the penetration into the supporting soils in order to provide the required frictional retance or end bearing pressure for blast loading.

Blast-Resistant DoorsAt least two independent means of exit should be provided. The exterior doors should be located remote from each other and at opposite walls of the building.

Doors should open outward and should be supported on all edges by the door frames. Doors should preferably be flush with the outside of the building, or notrecessed more than 18 inches into the building.

Doors, latches, and hinge mechanisms should be designed to be tight and remoperable after being subjected to the blast design loads.

Doors should be constructed of steel plates on both faces, internally reinforcedgenerally having the appearance of conventional flush metal doors.

Glass viewing ports, provided for routine entrance/exit doors, should not be largthan 1 square foot. Glazing should be, as a minimum, double laminated clear sglass with energy absorption capacity, prior to collapse, of more than twice thatrequired to resist the design blast loading. See Standard Drawing GF-R 1077, Details of Blast-Resistant Doors, included in the Standard Drawings section of manual.

• Vertical Exterior Walls Each wall should be designed for the peak reflectpressure

• Roofs Flat roof slabs and beams should be designed forthe incident overpressure

• Structural Framing The main structural framing should be designed the blast pressure on any one wall in accordance with the loading criteria for vertical exterior walls, together with roof loading



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Windows and Other OpeningsBlast-resistant buildings should be constructed without windows.

Openings such as vent intakes and fume hoods should be designed for blast efSuch openings should by location, by use of blast attenuators or by other meanprevent entry of shock waves and debris into personnel and critical equipment areas. Such openings should be kept to a minimum.

Equipment, such as air conditioners, cooling towers, etc., should not be placedthe roof of control houses.

Internal fixtures, such as lights, ceilings, ventilating ducts, and interior walls, should be designed and installed so that they will not fall if the building is subjeto the design blast loading specified.

440 Safety Storage BuildingsThere may be requirements for temporary storage of chemical and hazardous mrials on a Company site. This raises concern about:

• Spill containment• Fire protection• Security• Safeguards for personnel• Meeting regulatory standards

Such storage facilities are usually not very large in size and can be built on-sitewith concrete or masonry construction.

An alternative is to purchase special prefabricated units for chemical and hazarmaterial storage. These units are available with the following features:

• Spill containment sub-floor

• Forced air ventilation system

• Controlled environment (heating/cooling)

• Electrical system to meet specified classification

• Single unit capacity up to 10 tons of material (drums, boxes and cans); unitare available in sizes up to 9 feet by 22 feet

• Integral dry chemical or water fire protection system.

Information on these prefabricated units may be obtained from:

Safety Storage, Inc.2301 Bert DriveHollister, CA 95023(408) 252-2750



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450 Model Specifications and Standard Drawings

451 Model SpecificationCIV-MS-4796, Pre-Engineered Metal Buildings, with Data Guide CIV-DG-4796 and Data Sheet CIV-DS-4796 are included in the specification section of this manual. This model specification gives the requirements for the purchase of prericated, pre-engineered metal buildings, and includes structural design, vendor’responsibilities, structural steel fabrication, and such items as roof and wall panfasteners, flashing and trim, accessories, and drawings and data requirements.

CIV-MS-943, Concrete Block Construction (Hollow Unit Masonry), is included inthe specification section of this manual. It covers the materials to be used and tprocedures followed in building concrete block masonry walls.

452 Standard DrawingStandard Drawing GF-R 1077, Details of Blast-Resistant Doors, is included in tStandard Drawings and Forms Section of this manual.

460 References

General1. Uniform Building Code, International Conference of Building Officials.

The purpose of this code is to provide minimum standards controlling the design, construction, materials, use, and occupancy of buildings.

2. Recommended Design Practices Manual, Metal Building Manufacturers Asso-ciation (MBMA).

The purpose of this manual is to establish standard practices among the mfacturers of pre-engineered buildings to achieve maximum economy of deswithin the limits of good engineering practice.

3. Sweet’s Catalog File, McGraw-Hill.

Lists manufacturers’ data on products for general building construction. Includes a separate volume on “Selection Data” which provides general tecnical information and checklists that relate to all building systems and compnents.

4. Manual of Steel Construction. American Institute of Steel Construction, Inc.

Manual includes the dimensions and properties of standard structural memfor design and detailing. Includes sections on beam, column, and connectiodesigns. Includes AISC Specification for the Design, Fabrication and Erectiof Structural Steel for Buildings.

5. ACI Manual of Concrete Practice. American Concrete Institute Publication.



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Building Code Requirements for Reinforced Concrete (ACI Standard 318) provides the minimum requirements for reinforced concrete design or constion that is regulated by a general building code; includes analysis and desidevelopment of reinforcement, and reinforcement details.

Building Code Requirements for Concrete Masonry Structures (ACI 531) provides minimum requirements for materials, analysis, and design of structures which are built using concrete masonry units. Specification for ConcreMasonry Construction (ACI 531.1) provides a reference standard specificatwhich may be cited in specific project specifications.

6. American Society of Civil Engineers 7-93, Minimum Design Loads for Build-ings and Other Structures, 1994.

Provides requirements to govern assumptions for dead, live, and other loadthe design of structures.

7. ASTM Standards in Building Codes. American Society for Testing Materials.

Provides standard specifications, test methods, and definitions for structurasteel shapes and plates, cement, concrete, reinforcement, and other materused for buildings and structures.

8. Structural Engineering Handbook. Gaylord, Edwin H., Jr. and Charles N. Gaylord (Editors).

An all-inclusive handbook that includes information on structural analysis, steel, and reinforced concrete design.

9. Architectural Graphic Standards. The American Institute of Architects.

From general planning to detailed design. This is a valuable source of infortion on building construction and details.

Blast-Resistant Design10. Introduction to Structural Dynamics, John M. Biggs.

Includes a chapter devoted to blast-resistant design. Includes design tablescurves and examples for calculating the approximate effective fundamentalperiod for structural elements.

11. Design of Structures to Resist Nuclear Weapons Effects, American Society of Civil Engineers, Manual No. 42, 1961.

Includes chapters on choice of structural system, dynamic strength of materials, dynamic analysis, and design procedures all relating to blast-resistandesign.

12. Design of Blast Resistant Buildings in Petrochemical Facilities, ASCE Task Committee on Blast Resistant Design, American Society of Civil Engineers(1997).



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Includes general guidelines in the structural design of blast resistant petrocical facilities, types of construction, dynamic material strengths, allowable response criteria, analysis methods, and design procedures. Three exampcalculations are included.

13. An Engineering Approach to Blast-Resistant Design, Nathan M. Newmark, Transactions of American Society of Civil Engineers, Vol. 121, 1956.

Includes the fundamental work to develop the empirical equation used to dmine the equivalent static load for blast pressure.

14. Nuclear Safety Structures Code, ACI 349, Appendix C, Special Provisions for Impulsive and Impactive Effects.

Includes recommendations to assure ductility in the design of concrete strutural elements under impulsive loads. Also recommends allowable dynamicstrength increases and permissible ductility ratios.


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