Post on 31-Dec-2015
Introduction to Structural Design
© 2010 Project Lead The Way, Inc.Civil Engineering and Architecture
Architecture has recorded the great ideas of the human race. Not only every religious symbol, but every human thought has its page in that vast book.
- Victor Hugo
Structure of a Building
The primary function of a building structure is to support and transmit the building loads and forces to the ground.
Photos courtesy Tilt-up Concrete Association
Characteristics of a Structure
• Strength
• Stability
• Economic Value
Structural System
• Made up of many smaller structural sub-systems that work together to provide a strong, stable, and cost-effective structure.
• Examples of these smaller structural sub-systems include:
Structural engineers design these structural systems.
Structural Sub-System
• Made up of many structural elements that work together to provide a strong, stable, and cost-effective system.
• Basic structural elements include:
Structural engineers design these structural systems.
Forces and Loads
• A force is any action that causes a change in the shape or motion of an object.
• A load is a force that is supported by a structural element.
• The terms force and load are often used interchangeably.
SNOWWIND
Structural Member Forces
Tension – A force that stretches or pulls apart a member, resulting in the member elongating.
Compression – A force that squeezes or presses a member together, resulting in the member shortening.
Shear – A force that acts perpendicular to the axis of the member, causing the internal particles of the member to slide against each other.
Beam
• A structural element that carries a load that is applied transverse (perpendicular) to its length.
• Usually a horizontal member that carries a vertical applied load.
• The top fibers of a beam are in compression; the bottom fibers are in tension.
Cantilever Beam
• A special type of beam that is supported only at one end
• The top fibers of the cantilever are in tension; the bottom fibers are in compression
Column
A vertical structural element that carries an axial force in compression
COLUMN
Truss• A structural element that is composed of
smaller structural members typically configured in triangular arrangements
• Some truss members carry a tension force; others carry a compression force
Arch
• A curved structural element that spans over an open space
• In stone arches, the last stone to be placed at the top is called the keystone
KEYSTONE
Vault
A continuous arch that forms a ceiling or roof
Dome
A structural element that is made up of arches that radiate around a center point to create a half sphere
Hybrid Forms
• An infinite number of combinations of these forms exist
Design Process
The same design process used by engineers and designers in other disciplines can be used to design structural systems.
This design process was developed based on the University of Maryland - College Park - IRB Research Project
Architectural Program
• Defines the Problem
• Establishes overall concept and design philosophy
• Includes– Location of building on site– Architectural style– Interior space planning– Design elements– Construction materials– Building systems
Architectural Program• An architectural program establishes preliminary
structural systems.
• The structural engineer must analyze the structural systems and provide a strong, stable, and cost-effective design.
• Additional criteria needed:– Types and magnitudes of applied loads– Load path that each load will follow to the ground
Structural Design Process
Generate Concepts– Consider alternate
structural configurations, materials, and spacing to improve the design or reduce costs
Structural Design Process
Generate Concepts– Select an Approach
• Based on structural performance, compatibility with the architectural program, and cost
• Based on the possibilities explored, select the optimal design
Structural Design Process
Develop a Solution– Create a preliminary
structural design incorporating the selections for all structural elements
– Create technical drawings to represent your solution
Structural Design Process
Construct and Test Prototype– Create a model to
represent your structural design
• Structural analysis software
• 3D architectural software
• Physical model
– Test model
Structural Design Process
Evaluate the Solution– Assess the
effectiveness of the design
– Revise the design as necessary to correct problems with strength, stability, and compatibility with other systems
Structural Design Process
Present the SolutionIf the proposed design
solves the problem• Document the project
– Create working drawings and specifications for the structural design
• Communicate the project
Image Sources
• Tilt-up Concrete Association
(www.tilt-up.org)