Term
| What are the 2 categories of dead load in AASHTO? |
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Definition
DC = Dead Load of Strl. Components & Non-Structural Attachments
DW = Dead Load of Wearing Surfaces and Utilities |
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Term
| What is AASHTO load type DD? |
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Definition
DD = downdrag
Downdrag is a downward force applied to a deep foundation, caused by settlement. |
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Term
| What are the 4 types of "E" loads in AASHTO? |
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Definition
EH = Horizontal Earth Pressure Load
EV = Vertical Earth Pressure Load
ES = Earth Surcharge Load
EL = Accumulated Locked-In Force Effects Resulting from the Construction Process, Including Secondary Forces from Post-Tensioning. |
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Term
| What are the 7 types of Permanent Loads in AASHTO? |
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Definition
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Term
| Name the 2 AASHTO Live Loads: |
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Definition
LL = Vehicular Live Load
PL = Pedestrian Live Load |
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Term
| Describe the AASHTO Design Truck (loads, axle dimensions) |
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Definition
Three axles. 1st axle: 8 kips, 2nd and 3rd axles: 32 kips.
distance between 1st and 2nd axles: 14 feet. distance between 2nd and 3rd axles: between 14' to 30'.
width between wheels = 6'. |
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Term
| What is the "Design Tandem" in AASHTO? |
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Definition
Two axles, 4 feet apart.
each axle is 25 kips.
transverse wheel spacing is 6 feet.
Dynamic Load Allowance per 3.6.2.
(page 3-21) |
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Term
| How do you determine the number of design lanes for a bridge? |
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Definition
Divide w (w = clear, drivable, interior width of bridge) by 12 feet min. width, and round down.
However - if the traffic lanes are less than 12 feet, use the width of the traffic lane for the width of the design lane. |
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Term
| What is the "multiple presence of live load"? |
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Definition
| Section 3.6.1.1.2 gives you "m" multiple presence factors to use for loading one design lane or multiple design lanes. Need to look at this section in more depth. Also, this section relates to sect. 4.6.2.2 and .3. |
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Term
| what is the technical name for the design vehicular loading? |
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Definition
| HL-93 (consisting of a design truck/tandem AND design lane load) |
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Term
| What is the AASHTO contact area of a tire? |
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Definition
10 in x 20 in
(Sect. 3.6.1.2.5) |
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Term
| AASHTO Pedestrian Live Load is ___ ksf? |
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Definition
0.075 ksf for all sidewalks wider than 2 ft and considered simultaneously with the vehicular design load.
Pedestrian-only bridges (including bikes) are designed for 0.085 ksf live load. |
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Term
| What is the "IM" Load Type? |
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Definition
IM = Vehicular Dynamic Load Allowance
Per 3.6.2.1, applied to all design trucks or tandems (except centrifugal forces, braking forces, culverts/buried structures, and wood components) per Tbl. 3.6.2.1-1.
Deck Joints: 75% add'l
All other components:
- fatigue / fracture: 15% add'l
- all other limit states: 33% add'l |
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Term
| What is the standard "IM" Dynamic Load Allowance, and when is it not appropriate (name 4 exclusions)? |
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Definition
Typically 33% add'l of the static effects of the design truck or tandem.
Exclusions:
- deck joints
- fatigue/fracture
- culverts/buried structures
- wood |
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Term
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Definition
| Erosion of sediment at bridge piers due to moving water; loss of support. |
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Term
| What are the 2 kinds of Wind Loads? |
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Definition
WS = Wind on Structure
WL = Wind on Live Load |
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Term
In AASHTO, the Seismic [Performance] Zone is a factor of ______? |
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Definition
| Acceleration Coefficient "A" |
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Term
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Definition
| Mechanically Stabilized Earth |
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Term
| In AASHTO, to analyze a slab, how do you determine the effective width to analyze? |
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Definition
| Use the Table on pg. 4-18. The effective width depends on material, orientation relative to traffic, spacing of supports, span length, etc. |
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Term
| In AASHTO, when you are considering 1-way vs. 2-way action of strips of deck, what is the determining aspect ratio? |
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Definition
If greater than 1.5 -> one-way
If less than 1.5 -> two-way
(sect. 4.6.2.1.5) |
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Term
| What is the design span length for strips of slab in AASHTO? |
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Definition
Center-to-center of supports.
Can be considered continuous or simply supported.
Sect. 4.6.2.1.6. |
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Term
| In AASHTO, what is the design section for negative moments and shear in an equivalent slab strip? |
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Definition
It depends.
Use 4.6.2.1.6 to get type of construction. It can vary from the face of the support to 1/3 flange width from CL of support. |
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Term
| In AASHTO, what are the 2 major types of bridges and which is most common? |
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Definition
Most common: BEAM-SLAB BRIDGES. These have a slab spanning between girders.
Less common: SLAB-TYPE BRIDGES. These are monolithic structures, either concrete or wood, that do not have girders. |
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Term
| In AASHTO, how do you determine the span length, L, for girders/beams? |
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Definition
Depends on what you're calculating.
Use Table on page 4.26. For example,for negative moment, use average of two adjacent spans. |
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