ECIV 320 Structural Analysis I

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ECIV 320 Structural Analysis I
Structure
A system of connected parts used to support load
connected parts STRUCTURAL ELEMENTS
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Structural Elements

• Tie Rods
• (bracing struts)
• Tensile Forces
• Usually Slender

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Structural Elements

• Beams
• Characteristics
• Straight horizontal members
• Carry Primarily vertical loads
• Resist mainly bending
• Material
• Steel
• Reinforced Concrete
• Wood

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Structural Elements

• Columns
• Characteristics
• Vertical members
• Carry primarily vertical loads
• Resist mainly compressive forces
• Beam-Columns (Resist flexure)

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Types of Structures

• Trusses
• Planar
• Bridge, Roof support
• Space
• Towers, Derricks

Structure in Bending Members in Axial
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Types of Structures

• Cables
• Carry Loads in Tension
• Building Roofs, Bridges

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Types of Structures

• Arches
• Carry Loads in Compression
• Bridges
• Dome Roofs
• Openings in Masonry walls

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Types of Structures

• Frames
• Composed of Beams Columns
• Pin or Fixed Connections
• 2-D or 3-D
• Bending

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Types of Structures

• Surface Structures
• Made of materialhaving very smallthickness

• Very flexible membrane action
• Rigid plates and shells

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Design Loads
Most important and difficult task is the accurate
estimation of loads applied to a structure over
its life
Second most difficult is to determine load
combinations
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Design Loads - Types
Types of Loads
Dead Loads
Live Loads

• Weight of structural members
• Objects permanently attached to structure

• Vary in magnitude and location
• Objects temporarily attached to structure

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Design Loads - References
References General Building Codes
ASCE Minimum design loads for buildings and other
structures ASCE 7-02, ASCE 7-05
International Building Code Whittier CA,
International Conference of Building Officials
References Bridge Design Codes
Standard Specifications for Highway Bridges
(AASHTO)
Specifications for Steel Railway Bridges (AREA)
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Design Loads - References
References Design Codes
Building Code Requirements for Reinforced
Concrete (ACI) Manual of Steel Construction
(AISC) National design Specification for Wood
Construction (American Forest and Paper
Association)
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Design Loads Densities of Materials
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Design Loads densities of Materials
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Design Loads Minimum Dead
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Design Loads - Minimum Dead
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Dead Loads - Example
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Dead Loads - Example
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Live Loads

• Building Loads
• Bridge Loads
• Wind Loads
• Snow Loads
• Earthquakes
• Hydrostatic and Load Pressure
• Other Natural Loads

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Live Loads - Buildings
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Live Loads Bridges

• AASHTO
• Wheel loading and spacing
• Series of loadings at critical locations
• Dynamic Effects - Impact

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Wind Loads
Wind velocity depends on Height Terrain
Winds kinetic energy is converted to potential
energy
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Wind Loads
http//www.camerashoptacoma.com/mpegs/TacomaNarrow
sBridge.mpg
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Wind Loads
Dynamic or Static Approach
Static Approach (not suitable for high-rise
buildings)

• Static Approach 2-Step Process
• Step 1 Compute Kinetic Energy
• Step 2 Compute Wind Pressure on Surfaces

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Wind Loads Step 1
Wind Kinetic Energy q0.5rV2
ASCE 7-02 modifies q to account for importance of
structure, height and terrain
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Wind Loads Step 1
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Wind Loads Step 1
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Wind Loads Step 1
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Wind Loads Step 1
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Wind Loads Step 2
External Pressure
Internal Pressure
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Wind Loads Step 2
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Wind Loads Step 2
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Wind Loads Step 2
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Wind Loads Step 2
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Wind Loads Step 2
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Wind Loads Step 2
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Snow Loads
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Load Combinations

• Structural Design is not an action movie!
• Loads could act simultaneously
• Uncertainty Probability Theory LRFD
• 1.4 (DL)
• 1.2(DL) 1.6(LL) 0.5(SL)
• 1.2(DL) 1.5(E) 0.5(LL)
• etc

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Homework

• Reading Assignment
• Section 1.1 1.4
• Examples 1.1 1.4
• Live Load Reduction, Design Wind Pressure for
  Signs
• Homework Problems 1-3, 1-6, 1-9, 1-16, 1-17