Accounts for rare but high-impact events like earthquakes or ship collisions. Summary of Contents and Sections
Covers concrete, steel, aluminum, and timber structures, including superstructures and substructures. 2. Key Changes and Revisions in the 5th Edition (2010)
Predicting traffic patterns, environmental factors, and extreme events.
Updated empirical design methods for concrete decks, reducing the required internal reinforcement by recognizing the internal arching action of concrete slabs. Legacy Value and Current Status
η∑γiQi≤ϕRneta sum of gamma sub i cap Q sub i is less than or equal to phi cap R sub n Accounts for rare but high-impact events like earthquakes
Bridges must survive high-magnitude, low-probability events without suffering catastrophic collapse, ensuring that vital transport corridors remain open for emergency services. This section addresses:
(Load Factor): A statistically determined multiplier applied to specific loads (higher for highly variable live loads like traffic; lower for predictable dead loads like structural steel weight). Qicap Q sub i
Focuses on concrete slabs, metal grids, and orthotropic steel decks. 3. Substructure, Foundations, and Retaining Walls
The AASHTO LRFD Bridge Design Specifications, 5th Edition (2010), provides comprehensive, reliability-based standards for designing, evaluating, and rehabilitating highway bridges. Organized into 14 sections, this edition focuses on load and resistance factor design (LRFD) methodology, incorporating specific limit states for strength, service, and extreme events. You can review the specifications at Accuris . AASHTO LRFD Bridge Design Specifications - AISC Key Changes and Revisions in the 5th Edition
= Resistance factor (statistically determined multiplier based on material reliability) Rncap R sub n = Nominal resistance of the structural element
Restrictions on stress ranges caused by a single, idealized design fatigue truck.
∑ηiγiQi≤ϕRnsum of eta sub i gamma sub i cap Q sub i is less than or equal to phi cap R sub n ηieta sub i
Detailed criteria for live loads, including the HL-93 design truck. It focuses on maintaining vehicular comfort
This limit state restricts structural behavior under normal operational conditions. It focuses on maintaining vehicular comfort, managing aesthetic cracking in concrete, and preventing long-term structural degradation. Key provisions include:
Approximate elastic methods, finite element analysis (FEA), and yield line methods
– Geometric requirements and loads.