Quiz Flashcards
What are the two types of methods ASCE uses to calculate pressures on buildings ?
Normal force method - which must be used for gables rigid frames and may be used for any structures
Projected area method - assumes that horizontal pressures act on the full vertical projected area of the structure and that vertical pressures act simultaneously on the full horizontal projected area.
What is a girt
It is a structural wind member similar to a purloin on the roof
Buildings suffer the greatest damage at what frequency ?
Ground motion at a frequency close to or equal to their natural frequency
What is the difference between ASD and LRFD?
ASD uses service loads or loads given from the book
LRFD uses factored loads or loads that have been increased from the service load
It includes an ultimate load:
U: 1.2(dead load) +1.6 (live load)
How is does a two way flat slab work ?
It does not have a grid or beams under the slap and does not need temperature reinforcing. It accommodates large loads such as 30’x30’ and reduces punching shear by incorporating drop panel or a capital at the columns
What are the two irregularities outright banned by code ?
Extreme soft stories and extreme torsion in essential buildings in high seismic zones
Buildings must be designed to resist
wind or earthquake forces but not at the same time
A thin shell structure is able to resist what forces?
Shear, tension and compression but not bending
Where is wind pressure the highest on a building ?
Corners , overhangs, parapets
How does the dead load effect lateral forces ?
The dead load directly is proportional to seismic forces
The dead load does not effect wind forces
Charpy V-notch Test
A ductility test where a piece of material has a v-notch cut into the top. Tests how much energy it takes to make the not good go through the whole piece.
When bending is low shear is?
High
How much more load does a column half the length take then a full size column ?
8 times stiffer ( the stiffness of a column varies by the inverse of the cube of the length
How is a two-way beam slab used ?
A two way reinforced slab between four beans and that spans a square. Usually 40x40 span.
What org gives the allowable unit stresses for wood ?
National design specification for wood construction
What is the maximum drift allowed for a building ?
1/500
What is considered a Risk Catergory IV
These are buildings that are considered essential in that their continuous use is needed. They are usually needed in instances or medical, seismic, or fire emergencies
How is a two way flat plate used ?
Typically found in high rise, residential and light loads. Usually 20x20 and up to 30x30. No need for temperature reinforcing
How do you increase the section modulus of a member?
Increasing the amount of material away from the neutral axis of the member …i.e. make it deeper
What does the IBC require that drift be limited in typical buildings
0.02 and 0.01
What are theee solutions to the soft story?
Add columns,
Add bracing,
Add external buttresses
What are one-way structural systems?
Beam-and-girder system
Concrete joist system
Axial loads are more efficient in use of material in what direction to the load
Perpendicular
What is the minimum concrete coverage for a footing?
3”
The earthquake regulations of the IBC are intended to provided resistance to?
ground shaking
Frequency is the inverse of period
A 20 story building
Period = 2.0
Frequency = 1/2
.5 hertz
What are the benefits of using space frame over one-way parallel trusses?
the space frame tends to deflect less,
the space frame can be shallower
the loads are resisted by all members if the space frame
the space frame spans in two directions
What does the IBC in regards to handrails?
Handrails and guard rails shall be designed to resist a linear load of 50 pounds per linear foot.
What is the duration of the allowable design loads based on normal duration of loads
10 years
What is the natural period of most low-rise buildings ?
The natural period will be relatively short
What is considered a Risk Category II ?
Buildings and other structures except those in I, III, and IV
The wind pressures used in the design of buildings depend on?
wind speed
terrain
occupancy category
the part of the building under consideration
What is the maximum height for buildings in SDC D
no limit
What does the IBC say in terms of landscaped roofs ?
The uniform design live load in unoccupied landscaped areas on roofs shall be 20 psf
space frames are
highly undetermited
What are the effects on a building closer to the fault line ?
It will experience higher frequency and shorter period ground motion
What type of load is post and beam unable to support?
Lateral load
What does the IBC say about partition loads?
The partition load shall not be less than a uniformly distributed live load of 15psf if the uniform live load is 80psf or less
In regards to wind loads when must a building be approved by wind tunnel testing procedures ?
Buildings over 400ft in height
When can you reduce the live load?
The tributary area is greater than 150 sqft
The live load is less than or equal to 100psf ( not an assembly ) or the building does not support one floor of parking garage
The reduced live load must be greater than 50% of the original live load
Can a moment connection be made with wood ?
No
What is sin, cos, tan?
Rise, run, slope
The allowable shear in plywood is based on what?
The plywood grade
Nail size and spacing
Width of framing members
What concepts have been developed for strengthening existing construction ?
Add strength , alter stiffness , add continuity, add containment, rationalize the existing capacity and isolate the building from the ground
The shape that s cable assumes when the only load acting on it is its own weight ?
Catenary
Abrupt changes in topo can cause wind speeds to increase
Don’t locate building on upper half of a hill
What three properties help reduce seismic induced forces?
Damping , ductility , strength and stiffness
What does the IBC say in terms of wood ?
Bottom wood joist at least 18 in above ground
Ends of wood girders provide .5 in air gap
Crawl spaces provide 1ft bet area for ventilation
When can the repetitive use factor (Cr) or 1.15 be used ?
When the members are not over 4 in thick, not spaces more than 24 in oc And must be joined by bridging or decking ( three members in a group)
What are the requirements for columns in Type IV ?
Columns must be at least 8 in in any direction, brand and girders must be at least 6 in wide and 10 in deep and floor decking must be at least 3 in thick.
What is the difference between a connection on the web vs a bolt connection on the flange of steel?
Web = pin connection /shear
Flange = pin connection / moment
What does the IBC say in regards to decks?
Where supported by attachment to an exterior wall, decks shall be positively anchored to the primary structure and designed for north vertical and lateral loads as applicable. There should be no use of toenails or nails subject to withdrawal.
Earthquake damage tends to be more severe in areas of ?
Soft ground
How many reactions in each support ?
Roller = 1 vertical reaction Pin = 2 vertical and horizontal Fixed = 3 vertical, horizontal, and moment/rotation
what type of diagram is the same as a stress diagram?
Maxwell
How does the fundamental period of vibration of a building affect its seismic load?
the longer the period the smaller the seismic load. A longer period means a more flexible building.
What is considered a Risk Category III?
Buildings that represent a substantial hazard to human life in the event of failure. Like schools, colleges, public assemblies
What does the IBC say in terms of interior walls and partitions ?
Interior walls and partitions that exceed 6 ft in height including their finish materials shall have adequate strength to resist the loads to which they are subjected but not less than a horizontal load of 5psf
What is a another name for shear studs ?
Nelson studs
What is considered a Risk Category I?
Low hazard buildings
Is a lamella structure one way or two way ?
One way
An arch supports load by ?
A combination of compression and bending
Where are stirrups in relation to the suppers ?
More stirrups at the support
What is the reference height of the basic wind speed?
33 ft
What does the IBC in terms of dynamic and static lateral forces ?
The dynamic method is always permitted while the static method is only allowed under certain conditions
What does the IBC say in terms of the reduction of live loads?
Live loads that exceeds 100psf shall not be reduced. The live loads for members supporting two or more floors are permitted to be reduced by a max of 20%
What makes a Vierendeel truss different from a regular truss?
It has rigid joints not pinned.
It resists bending movements not axial loads
It resists shear forces.
What does the IBC say about dead loads?
First floors in office buildings where partition locations are subject to change must be designed to support a uniformly distributed load of 20psf. Access floor systems may be designed to support an additional 10psf of uniformly distributed dead load over all other loads