Building Construction/Collapse Flashcards
Why study building construction?
- Understanding of fire spread
- Understanding of collapse potential
- Understanding of hidden dangers
- Understanding of how to apply strategy and tactics to fight fire safety based on building construction specifics.
- Because building on fire are our work place and it is in our best interest to understand the hazards and characteristics of our workplace.
Who said “A building does not drop from the sky as does a disabled aircraft. Neither is it a transient, much as a ship, a truck, or a train. Very often it has been in existence since long before any of the firefighters at the scene where born. Yet sad to say, in many cases the building might as well be a spaceship from Mars for all the Fire Department knows about it.” ?
Francis Brannigan
Average lifespan of a building is ____
75-100 years.
24hr/day gravity is trying to pull it down.
Again, why do we study building construction?
- On average, 110 firefighters still lose their lives each year!
- Since 1900’s, the frequency of fires has dropped considerably.
- Since 1900’s, the frequency of firefighter deaths has stayed the same.
Building construction language
a. It is important for us to be able to speak the right language in regard to building construction
b. Enables us to communicate with other agencies
c. Enable s us to be more specific when speaking to each other
d. Helps our professional image
e. Clear, precise communication is essential on the fireground!
Forces placed upon structural components are known as ____
loads.
All firefighters should know what about loads?
i. Have a basic understanding of loads within a building.
ii. Be able to understand how the building loads will change when the building is compromised.
What is a GRS and what does it do?
Gravity Resistance System
i. All structural elements and connections that support a transfer loads placed on a structure are part of GRS
ii. Designed to transfer all loads placed on the structure down to the ground.
iii. Compromise of GRS interrupts load transfer to ground. Thus loads are placed on adjoining structural members that were not meant to handle them.
What are the two types of loads caused by gravity?
Dead loads
Live loads
Whats a dead load?
weight of the building and everything permanently attached to it
a. We care about dead loads because added dead loads such as AC units may not have been planned for structurally.
b. Materials are expensive.
i. Reduction in dead weight at the top of a building allows reductions in the overall weight of GRS.
ii. Less mass in structural members = less fire resistance, as fire resistance is a function of its surface to mass ratio
What are orthostatic vital signs?
Orthostatic vital signs are a series of vital signs of a patient taken while the patient is supine, then repeated sitting up, then again while standing. A variation is to check blood pressure and heart rate in supine and then standing positions only. The results are only meaningful if performed in the correct order (starting with supine position)[1][2][3] Used to identify orthostatic hypotension,[4] orthostatic vital signs are commonly taken in triage medicine when a patient presents with vomiting, diarrhea or abdominal pain; with fever; with bleeding; or with syncope, dizziness or weakness.
What is a live load?
the weight of all movable things in and on the building, such as people, furniture, and supplies.
a. We care about live loads because they cannot be specifically calculated ( must be estimated based on building use)
b. Building codes specify minimum designs for specific uses.
i. Uniform Live load for distributed loads
ii. Concentrated load for specific large objects.
c. If the building changes, the actual live loads may change, but unless it’s renovated, the structure was designed for a different live load.
d. Firefighting can add live load to the structure that it is not designed for. For example, a 1000GPM master stream will at over 8000lbs a minute…
What are some other things about loads that would be handy to know?
i. Loads placed on a building create stress within the materials bearing the load.
ii. How and where the force or load is applied to the materials determines what internal stresses the material experience.
3 types of stress in a material
- Compression: squeezing things together
- Tension: pulling things apart
- Shearing: sliding or bending type stress in the member.
Define Axial load
- Loads applied parallel to the axis of the member and pass through the centroid of the cross section of the member
- Compressive
- Tensile
Define Tension (Flexural or Bending stress)
- Force applied perpendicular to the axis of the member
2. Compressions on the top by the applied load and tension on the bottom.
Define Eccentric Loads
- Loads that are applied parallel to the axis of the member but that do not pass through the center of the cross section of the member.
- Causes compression on parts underneath the load and tension elsewhere.
Define Deformation
- Different materials react differently to different forces. Duh.
a. Concrete is good under compressive loads but not tension
b. Steel is good in both tension and compression depending on its makeup
c. Wood is decent in compression as well as tension. - Deformation is the change in size and shape of member under a load.
Define Elasticity
a. The ability of a material to return to size and shape after deformation under load
b. A ductile material can be subject to a large amount of stress without breaking
c. A brittle material will break early when subject to a large amount of stress.
What’s an environmental load?
i. Based on where a building is built, it must be able to withstand different types of environmental loads
1. Snow, wind, earthquakes, hurricanes, tornadoes, etc.
ii. Calculating snow/rain loads
1. Can be distributed or concentrated
2. Calculated based on average snowfall levels for the area (using a worst case scenario)
3. Normal live load calculation is 20psf for roofs (FF ~225psf-275psf)
4. Rain load obviously depends on if the water is able to run off or not and how quickly.
What do we know about structural stability?
a. Depends on the loads placed on the building
i. Designed vs undersigned
ii. Dead/live loads
b. Also important is the method of load transfer
c. Buildings are meant to transfer all loads through the structure to the ground.
d. Methods of connection of its members are an important component.
e. Consider the connection of the floors to the building…
f. A building can be built with super strong materials, but if they are not connected in a way that is as strong as the materials themselves, it will fail when subjected to extraordinary loads.
g. A building is only as strong as its connections!!!
