Who What Where
Who, What & Where Who are the users? Church School Manufacturers Researchers
Who, What & Where What is the purpose? Fellowship Teaching Manufacturing Production
Who, What & Where Location, Location, Location
Who, What & Where Where is the project located? Building Code Environmental Forces Construction Practices
Limitation of Discussion Use Educational, Administrative and Assembly space Structure Structural Steel with typical and long span components up to approximately 3 floors
Building Loads Forces experienced by structures
Building Loads STRUCTURE LIVE LOADS ENVIRONMENTAL LOADS SELF-WEIGHT OCCUPANCY AND USE ROOF LOADS WIND LOADS EARTHQUAKE LOADS FLOOD LOADS STRUCTURAL FRAMING MEP EQUIPMENT SNOW LOADS THERMAL LOADS EARTH PRESSURES ARCHITECTURAL FINISHES & CLADDING UNIFORM LOADS CONCENTRATED LOADS SPECIAL EQUIPMENT
Live Loads.. loads produced by the use and occupancy of the building
Live Loads Occupancy or Use Live Load Occupancy or Use Live Load Assembly & Theaters (fixed seats) 60 Assembly (movable seats) 100 Stages and Platforms 125 Projection & Control Rooms 50 Catwalks 40 Corridors & Lobbies 100 Dinning Rooms & Restaurants 100 Parking Decks 40 Libraries (reading rooms) 60 Libraries (stack rooms) 150 Administrative 50 Classrooms 40 Stairs & Exits 100 Retail 75
Live Loads are Reducible Reduction reflects the statistical probability that a floor will be fully loaded at any one time. Reduction based on occupancy, structural component and floor area being supported by component. Most floor joist or floor beams do not see a reduction. Girders and beams maximum reduction is 40% Columns maximum reduction is 60%
Live Loads Consider designing with Unreduced live loads or More than code required live loads
Building Loads Environmental Loads Snow Wind Flooding Seismic
Snow Loads Impact Snow drifts and sliding snow Structural considerations Local near parapets Mechanical Equipment Multi-tiered roofs Cost implications Some increased member sizes Low Impact
Snow Loads Impact Snow weight over entire structure Structural considerations Entire roof Cost implications Most Structural members will require increased sizes Moderate Impact
Snow Loads Severe Impact Impact Snow weight over entire structure Structural considerations Entire roof Cost implications Increased decking gauge Reduction of member spacing Significant increase in member sizes
Wind Loads Design Peak Gust Hurricane Wind Speeds (mph) in Open Terrain 90-100 100-110 110-120 120-130 130-140 140-150 150-160
Wind Loads Impact Typically limited to buildings lateral system Structural considerations Slight increase in bracing and foundations Cost implications Some increased member sizes Low Impact
Wind Loads Impact Entire building including exterior cladding Structural considerations Roof decking and attachments Drag struts Increased foundation sizes Cost implications Significant over entire building including cladding Stringent component attachment requirements Moderate Impact Severe Impact
Flood Loads Low Areas Rivers Coastal Regions Break-away away walls Crawl space flow-through Limitation of inhabitable space Foundation scour
Seismic Loads Impact Wide building expansion joints Loads on building increase exponentially Attachments of all building components Anchorage of MEP equipment and building fixtures Low Impact Moderate Impact Severe Impact
Seismic Loads Cost Implications Moderate and severe regions often see significant cost increases Low Moderate Severe
BEST PLACE TO BUILD A BUILDING
Building Loads Dead Loads Weight of structure Mechanical equipment Finishes
Dead Load Engineers Design must hold it up
Dead Load Special finishes and features Baptisteries
Dead Load Special finishes and features Baptisteries Catwalks
Dead Load Special finishes and features Baptisteries Catwalks Platforms
Dead Load Special finishes and features Baptisteries Catwalks Platforms Drywall soffits and special glazing
Deflections and Drift Framing Deflection Serviceability, not a strength issue
Deflections and Drift Structural systems and members thereof shall be designed to have adequate stiffness to limit deflections and lateral drift.
Deflection Limits Floor Members Construction Roof Members: Supporting plaster ceiling Supporting non-plaster ceiling Not supporting ceiling IBC TABLE 1604.3 DEFLECTION LIMITS L I/360 I/240 I/180 I/360 S or W I/360 I/240 I/180 D + L I/240 I/180 I/120 I/240 Exterior walls and interior partitions: With brittle finishes With flexible finishes Farm buildings Greenhouses I/240 I/120 I/180 I/120
Deflections and Drift What to look for Long spans adjacent to walls Detail for movement between structure, cladding and finishes Long spans adjacent to windows and brittle finishes Walls with masonry veneer Tall walls Flat roofs Ponding the retention of water due to the deflection of the roof framing Roofs with no free edge to drain
Building Drift The movement of the top of the building relative to the base of the building.
Building Expansion Joints
Building Expansion Joints Expansion Joint Configuration Overall length of building Shape of building
Building Expansion Joints Once it is determined an expansion joint is required Factors of Joint Width Temperature change Generally very small, especially if the structure is continuously heated or cooled
Building Expansion Joints Once it is determined an expansion joint is required Factors of Joint Width Temperature change Generally very small Wind forces Less than one inch depending on lateral system
Building Expansion Joints Once it is determined an expansion joint is required Factors of Joint Width Temperature change Generally very small Wind forces Less than one inch depending on lateral system Seismic forces Can require large structural joints
Building Expansion Joints Additional Location of lateral bracing Stiffness of columns
Building Expansion Joints Avoid them if possible Expensive Special cladding and finish required MEP system can incur special detailing
Vibration
Vibration When do structural engineers worry about vibration? Large open spaces with few users Malls Large classrooms Fellowship halls
Vibration When do structural engineers worry about vibration? Theatrical and exercise space Rhythm of dancers, athletes and music can create unacceptable levels of vibration.
Vibration When do structural engineers worry about vibration? Laboratory, healthcare imaging and research space Specialized equipment may not work if vibration limits are exceeded.
Vibration What can minimize vibration worries? Stiffening the structure Increase mass of structure
Vibration What can minimize vibration worries? Stiffening the structure Increase mass of structure Will add cost to minimize
Acoustics Structures do move... Movement of steel results in creaking and popping Most noticeable in large, quiet places
The Grid Optimization of grid = Savings to the Owner
The Grid Avoid grids that do not stack Avoid transfer girders Avoid irregular grids Lose advantage of repetitive fabrication More beams required to support offset conditions
The Optimal Grid Optimal Bay Size: Length to width ratio of approximately 1.25 to 1.50
Preliminary Structural Components Beams Optimal Depth = Cost Effective Depth (in) = Span (ft) / 2 Consult with structural engineer if bay size is flexible
Preliminary Structural Components Joist (typical for basic wind, snow and seismic regions) Roof : 6 6 0 Floor: 2 2 0 to 3 3 0 Depth (in) = Span (ft) *3/4
Structural Steel Depths Available Joist Profiles
Structural Steel Depths Truss Depths Great for large loads Great for long spans Can be designed and detailed to match architectural preferences Avoid arches if possible Very expensive
Columns Types Pipes Tubes Hollow Structural Shapes Wide Flanges
Columns Cost Varies based on market
Columns Wide flanges may be preferable in multi-story construction
Preliminary Column Sizes Number of Stories Bay Spacing 1 2 3 20 X 20 5 X 5 6 X 6 10 X 10 20 X 30 5 X 5 6 X 6 10 X 10 20 X 40 6 X 6 8 X 8 10 1/4 X 10 1/4 30 X 30 6 X 6 8 X 8 10 1/4 X 10 1/4 30 X 40 6 X 6 10 1/4 X 10 12 1/2 X 12 1/4 40 X 40 8 X 8 10 1/2 X 10 1/4 13 X 12 1/4 Maximum 15 0 Floor Height Table is approximate and provides for allowance for selection of optimal shape and size of column
Lateral Bracing Placement and Locations Preferred locations varies between structural engineers Options Include Core of building Perimeter of building
Lateral Bracing Types of Braces
Lateral Bracing Materials Masonry Concrete Shafts Tilt-up Panels Steel X-type X Bracing Steel Frames
Lateral Bracing Most Economical: Typically steel X-type X Bracing (Exception: load bearing walls are present)
Lateral Bracing Avoidance of openings Environmental Loadings
Foundations Coastal Regions Anticipate Piling Near coastline For heavily loaded foundations Soils with anticipated settlements
Foundations Lowland Areas Improved swampland or filled valleys Significant soil remediation Deep foundations
Foundations Northern Climates Bottoms: below the frost elevation Sidewalks: stabilized to avoid frost heave Perimeter insulation
Foundations Mississippi Gumbo Expansive clays shrink and swell Combination of remedial solutions:
Foundations Mississippi Gumbo Expansive clays shrink and swell Combination of remedial solutions: Soil remediation Deep foundations Framed slabs over carton forms Post-tensioned tensioned slabs
Foundations Birmingham Limestone geology presents unique challenges Pinnacled limestone Sinkhole activity Soft clay layer directly above rock
Exterior Cladding Exterior Cladding Brick Other cladding types Moderate and severe wind regions and seismic regions Store fronts and curtain walls Force protection systems
Exterior Cladding Brick BIA provides recommendations for backup deflection Usually L / 600 May require use of masonry or deeper studs to meet deflection requirements.
Exterior Cladding Other Cladding Types Allowable deflection assumed to be per IBC Usually L / 240 Consider limitation carefully 15 wall would deflect ¾
Exterior Cladding Wind & Seismic Regions Anticipate stringent cladding attachments Deeper backup systems
Exterior Cladding Curtain Walls Multi-story walls require either internal or external support Cost and coordination often not recognized until late in the project!