1. Structural Loads

2. Structural Design
Strength: structural system can support loads without failure
Serviceability: deformations are within allowable limits

3. Design Manuals
Technical standards which establish requirements for the actual structural design.
(a) Type of Structure
(b) Type of Material
Standard Specifications for Highway Bridges,
American Association of State Highway and Transportation Officials (AASHTO)
Manual of Steel Construction,
American Institute of Steel Construction (AISC)
Building Code Requirements for Reinforced Concrete (ACI 318),
American Concrete Institute (ACI)

4. Building Codes
Account for influence of local conditions on building construction (e.g., building codes specify minimum design loads for structures)
International Building Code, International Code Council (ICC)
Minimum Design Loads for Buildings and Other Structures, ASCE/SEI 7-05

5. What kinds of loads must a structure support?
People
Material itself
Snow
Wind
Seismic
Flood
Vehicles
Furniture
Contents allowed on floor maximum
Dirt

6. Classification of Structural Loads
Dead loads (DL):
Dead loads have constant magnitude and fixed location
Live loads (LL):
Live loads can have varying magnitude and location can change
Loads due to environmental factors
Weight of
structure
Weight of objects
permanently attached
to structure
DL =
Loads that can be moved during the life of a structure
LL =

7. Environmental Loads Wind Snow Earthquake Hydrostatic/soil pressure
Blast
Fire
Design loads given in building codes based on probability of occurrence for given location
Dams, retaining walls, storage tanks `
When treated as structural loads, require complex analyses

8. Sample Contour Map
Contour map for seismic design

9. Computing Loads

10. Floor Plan Diagram
In structural engineering, it is useful to look at floor systems from a plan view.
Plan view means to look at the structural system from directly above (“bird’s eye view”).
From a floor plan, you can:
determine the location of the columns,
determine the arrangement and spacing of the floor beams, and
identify which members are joists, girders, and spandrels.
What is a Structure? A structure consists of a series of connected parts used to support loads.

11. Floor Plan Diagram
What is a Structure? A structure consists of a series of connected parts used to support loads.

12. Gravity Loads vs. Lateral Loads

13. Tributary Area Distribution of loads to structural members
Ex.- Floor system of a building consisting of a 5-in. thick reinforced concrete slab resting on four steel floor beams, which are supported by two steel girders.

14. Tributary Area Tributary Width for Beam CG = (5 ft + 5 ft) = 10 ft A B

15. Computing Dead Loads
Weights for common building materials and building components are given in tables
(refer to Table 1-2, p.10 in Hibbeler text)

16. Example: Dead Load/Tributary Area
Given:
Floor plan and member areas shown in figure below.
Unit weight for reinforced concrete = 150 lb/ft3
Unit weight for steel = 492 lb/ ft3
Compute the dead load acting on beams CG and DH, and girder AD.

17. RC= 150 lb/ft3 and S= 492 lb/ ft3
RC= 150 lb/ft3 and S= 492 lb/ ft3. DBEAM-CG , DBEAM-DH , and DGIRDER-AD ?

18. RC= 150 lb/ft3 and S= 492 lb/ ft3.E F G H

19. Alternatively: use tributary area to find force on column D.G H

20. Live Loads in Buildings
Design live loads for buildings provided in ASCE/SEI-7 (refer to Table 1-4, p.13 in Hibbeler text)

21. Live Loads on Bridges Highway Bridges (AASHTO specification):
Design Truck Load:
Live loads applied rapidly cause greater stresses in members  Impact Factors

22. Computing Wind Loads
Static wind pressure computed from kinetic energy by
qs = 0.5mV2
m = mass density of air
V = velocity of wind (ASCE/SEI-7)
qs is then modified to account for
Importance of building (hospital vs. warehouse)
Exposure conditions (city vs. open plains)
Topography (level ground vs. on a hill)
Gustiness
How wind is distributed on sides of building.