PART 2 PRELIM Flashcards
(59 cards)
GENERAL REQUIREMENTS
The American Association of State
Highway and Transportation Officials
(AASHTO) specifications require highway
bridges be designed for:
_____, ______, and
______, with due regard to issues
of _____,______, and _____
constructability, safety, and
serviceability
inspectability, economy, and
aesthetics.
primary approach
recommended by AASHTO for both
bridge design and evaluation.
Load and Resistance Factor Design
(LRFD) method
a reliability-based design
approach
LRFD
account for
uncertainties in applied loads.
Load Factors
reflect material
variability and construction tolerances.
Resistance Factors
a condition beyond which
a structure or its components cease to
perform their intended function safely
and efficiently.
Limit states
defines the boundary between
acceptable and unacceptable
performance in terms of strength,
serviceability, and other criteria.
Limit state
used to ensure that bridges remain safe
and functional under various loads and
conditions throughout their service life.
Limit states
The limit states specified in the AASHTO
codes are intended to provide a
buildable and serviceable bridge
capable of safely carrying the design
loads for the specified life span of _____
years.
75
A bridge design must satisfy all relevant
limit states to be considered safe and
effective.
Strength Limit State
Serviceability Limit State
Fatigue and Fracture Limit State
Extreme Event State
ensures that the
bridge has sufficient capacity to resist
the maximum expected loads without
experiencing structural failure, such as
collapse or excessive yielding of
materials.
Strength limit state
Prevents catastrophic failure.
Ensures public safety under worst-case
loading conditions.
Strength limit state
Guarantees the bridge’s ability to
support expected traffic and
environmental loads.
Strength limit state
The strength limit state accounts for:
Dead Loads
Live Loads
Environmental Loads
Impact Loads
Stability
ensures
that the bridge remains functional,
comfortable, and durable under normal
operating conditions, without excessive
deflections, vibrations, or cracking.
serviceability limit state
Maintains user comfort and operational
efficiency.
Prevents service interruptions due to
excessive deformations.
Enhances long-term durability by
minimizing material damage.
serviceability limit state
The serviceability limit state accounts for:
Deflections
Vibrations
Crack Control
Creep and Shrinkage
Thermal Expansion
evaluates the bridge’s ability to
withstand repeated cyclic loading over
its lifetime without experiencing
progressive material damage, such as
cracking in steel or concrete.
fatigue and fracture limit state
Prevents failure due to cumulative
damage over time.
Ensures long-term structural integrity
under repeated loading.
Addresses concerns in high-traffic or
heavily loaded bridges.
fatigue and fracture limit state
Fatigue and fracture evaluation takes into
account:
Repeated Traffic Loads
Material Stress Cycles
Crack Propagation
Detailing and Connections
ensures
that the bridge can withstand rare but
severe events such as earthquakes,
floods, hurricanes, or vehicle collisions
without collapsing.
extreme event limit state
Protects human life and critical
infrastructure during emergencies.
Ensures resilience and functionality
after extreme events
Helps in planning emergency response
and recovery
extreme event limit state
Extreme Event limit state takes into account
for:
Seismic Forces
Floods and Scour
Fire Hazards
Accidental Loads
Extreme Weather
refers to the ability to
successfully complete the construction
of the bridge being designed.
Constructability
