# Shared Flashcard Set

## Details

PE - Strl I - AASHTO
AASHTO
25
Engineering
Professional
05/17/2009

Term
Definition
Term
 What is AASHTO load type DD?
Definition
 DD = downdrag   Downdrag is a downward force applied to a deep foundation, caused by settlement.
Term
 What are the 4 types of "E" loads in AASHTO?
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.
Term
 What are the 7 types of Permanent Loads in AASHTO?
Definition
 DC DD DW EH EV ES EL
Term
 Name the 2 AASHTO Live Loads:
Definition
Term
 Describe the AASHTO Design Truck (loads, axle dimensions)
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'.
Term
 What is the "Design Tandem" in AASHTO?
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)
Term
 How do you determine the number of design lanes for a bridge?
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.
Term
 What is the "multiple presence of live load"?
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.
Term
Definition
 HL-93 (consisting of a design truck/tandem AND design lane load)
Term
 What is the AASHTO contact area of a tire?
Definition
 10 in x 20 in   (Sect. 3.6.1.2.5)
Term
 AASHTO Pedestrian Live Load is ___ ksf?
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.
Term
 What is the "IM" Load Type?
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
Term
 What is the standard "IM" Dynamic Load Allowance, and when is it not appropriate (name 4 exclusions)?
Definition
 Typically 33% add'l of the static effects of the design truck or tandem.   Exclusions: - deck joints - fatigue/fracture - culverts/buried structures - wood
Term
 What is scour?
Definition
 Erosion of sediment at bridge piers due to moving water; loss of support.
Term
 What are the 2 kinds of Wind Loads?
Definition
 WS = Wind on Structure   WL = Wind on Live Load
Term
 In AASHTO, the Seismic [Performance] Zone is a factor of ______?
Definition
 Acceleration Coefficient "A"
Term
 What is MSE?
Definition
 Mechanically Stabilized Earth
Term
 In AASHTO, to analyze a slab, how do you determine the effective width to analyze?
Definition
 Use the Table on pg. 4-18.  The effective width depends on material, orientation relative to traffic, spacing of supports, span length, etc.
Term
 In AASHTO, when you are considering 1-way vs. 2-way action of strips of deck, what is the determining aspect ratio?
Definition
 If greater than 1.5 -> one-way If less than 1.5 -> two-way   (sect. 4.6.2.1.5)
Term
 What is the design span length for strips of slab in AASHTO?
Definition
 Center-to-center of supports. Can be considered continuous or simply supported.   Sect. 4.6.2.1.6.
Term
 In AASHTO, what is the design section for negative moments and shear in an equivalent slab strip?
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.
Term
 In AASHTO, what are the 2 major types of bridges and which is most common?
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.
Term
 In AASHTO, how do you determine the span length, L, for girders/beams?
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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