Overview of seismic codes for structural engineering

Compliance with seismic standards is crucial to ensure the safety and resilience of concrete buildings and steel structures during earthquakes. Seismic standards establish minimum requirements for the design, construction and testing of these structures to withstand seismic forces. Failure to comply with these standards can have catastrophic consequences, including loss of life, property damage and economic disruption.

Seismic Design and Earthquake Engineering

Seismic design and earthquake engineering are related to structures’ behavior during seismic events, such as earthquakes. Buildings are subjected to seismic loading, which can cause them to shake, vibrate, and even collapse if they are not designed to withstand these forces. Seismic design is the process of enforcing structures to resist earthquake ground motions, while earthquake engineering is the study of the behavior of structures during seismic events. Earthquake engineering studies the behavior of structures under seismic loading conditions, involving the physics of earthquakes, the mechanical properties of materials and structures, the ground motion, and its effects on structures. This includes developing models to predict structures’ behavior under different seismic loading conditions.

Seismic design and earthquake engineering are critical to ensure structures’ safety and resilience in earthquake-prone regions. Also, they help to solve such important problems as risk reduction, performance evaluation, regulatory compliance, infrastructure development. Proper design and construction of buildings and infrastructure can help to mitigate the effects of seismic loading and reduce the risk of damage and loss of life during earthquakes.

As can be seen in the map above, the most dangerous zones of seismic activity around the world, include:

• Pacific Ring of Fire, stretching from the west coast of North America, down the coast of South America, across the Aleutian Islands, and along the eastern and southern coasts of Asia and Oceania.
• Mediterranean and Middle East: This region is known for its frequent earthquakes due to the collision of the African and Eurasian plates. The area extends from Turkey and Greece in the west, to Iran and Pakistan in the east.
• Himalayas: The Himalayas are a seismically active region due to the collision of the Indian and Eurasian plates. The region is prone to major earthquakes, such as the 2015 earthquake in Nepal.
• Alaska: Alaska is one of the most seismically active regions in the United States due to the subduction of the Pacific Plate beneath the North American Plate.
• Western United States: The western United States is also a seismically active region due to the presence of the San Andreas Fault, which is a transform fault that marks the boundary between the Pacific and North American Plates.
• South America: The western coast of South America is another seismically active region due to the subduction of the Nazca Plate beneath the South American Plate.

Earthquake Codes for Concrete (for Buildings)

For the past 100 years, seismic-resistant codes have been implemented in over 160 countries and nations. However, their quality, extent of application, and methodologies vary. Though, these are seismic code quality and building typology, how a building is made or building practice, and the quality of the materials used that play a significant role in the final structure vulnerability. There are some general principles commonly included in earthquake-resistant design codes for concrete structures. Concrete is one of the most widely used building materials in the world – cheap and bearing structural weight. Building codes typically require that concrete structures be designed to resist lateral forces, typically measured using a parameter called the seismic coefficient, which is based on the expected ground acceleration at the building site. It’s important to consult local building codes and standards to ensure that any specific earthquake-resistant design requirements are being met in the region.

There are several international codes and standards related to earthquake-resistant design of concrete buildings. Here are some of the commonly used codes and standards:

• ACI 318: This is the Building Code Requirements for Structural Concrete and Commentary published by the American Concrete Institute (ACI). The code covers the minimum requirements for design and construction of reinforced concrete buildings to resist earthquake forces.
• ASCE 7: The American Society of Civil Engineers (ASCE) publishes the standard Minimum Design Loads and Associated Criteria for Buildings and Other Structures, which includes provisions for seismic design.
• Eurocode 8: The European standard EN 1998-1, also known as Eurocode 8, provides guidelines for the seismic design of buildings. It covers the design of new buildings as well as the seismic assessment and strengthening of existing buildings.
• NZS 1170: This is the New Zealand standard for structural design actions, which includes provisions for seismic design of buildings.
• IS 1893: The Bureau of Indian Standards (BIS) publishes the code IS 1893, which provides guidelines for seismic design of structures, including buildings.
• GB 50011: This is the Chinese standard for seismic design of buildings, which provides design principles and requirements for seismic resistance of reinforced concrete structures.
• AIJ Standard for Structural Design of Reinforced Concrete Boxed-Shaped Wall Structures.

These codes and standards provide guidelines for seismic design of buildings, including provisions for strength, stiffness, ductility, detailing, and other aspects related to the seismic resistance of concrete structures.

Seismic Standards for Steel Structures

Let us pay more attention to the seismic standards for steel structures. They refer to the guidelines and requirements in place to ensure that steel buildings can withstand the forces of earthquakes, stay safe and resilient during an earthquake.

There are several seismic standards that are used for steel structures, including:

• ASCE 7: Minimum Design Loads for Buildings and Other Structures – This standard provides guidelines for the design and construction of buildings and other structures to withstand the effects of earthquakes, including guidelines for the design of steel structures.
• AISC 341: Seismic Provisions for Structural Steel Buildings – This standard provides guidelines for the design, fabrication, and erection of steel structures to resist the effects of earthquakes, including specific detailing requirements for seismic resistance.
• AISC 358: Prequalified Connections for Special and Intermediate Steel Moment Frames for Seismic Applications – This standard provides prequalified connections for steel moment frames used in seismic applications, which are designed to withstand the effects of strong earthquakes.
• ACI 318: Building Code Requirements for Structural Concrete – Although this standard is primarily focused on concrete structures, it also includes provisions for steel structures in seismic zones.
• Eurocode 8 or EN 1998-1. In the Section 6, the specific rules for steel buildings are explained.
• ISO 3010:2017: Bases for design of structures — Seismic actions on structures. This standard covers specific rules for steel structural elements.

The rules and regulations are continually updated and revised to ensure that they reflect the latest research and understanding of seismic design principles. It is important for engineers, architects, and builders to stay up-to-date on them to ensure that the designs meet current safety and performance requirements.

Earthquake Design for Bridges

Earthquake design for bridges involves creating structures that can withstand the ground shaking and other seismic forces that occur during an earthquake. This is critical for ensuring the safety of drivers and passengers who use these bridges.

There are several key design considerations that engineers consider when designing earthquake-resistant bridges. These include:

• Site selection: Bridges should be located in areas where the risk of earthquakes is relatively low, and where the ground conditions are stable.
• Foundation design: The foundation of the bridge must be designed to withstand the seismic forces that will be exerted on it during an earthquake.
• Structural materials: Bridges must be constructed using materials that are strong, durable, and able to resist the forces of an earthquake. Common materials used for earthquake-resistant bridges include steel, concrete, and composites.
• Damping systems: Damping systems, such as tuned mass dampers or viscoelastic materials, can be used to absorb some of the energy from an earthquake and reduce the amount of movement in the bridge.
• Seismic isolation: Seismic isolation involves placing the bridge on flexible bearings or isolators that can move independently of the ground during an earthquake, reducing the amount of seismic energy transmitted to the bridge.
• Redundancy: Bridges are designed with redundant structural elements to ensure that the failure of one part of the bridge does not cause a catastrophic failure of the entire structure.
• Regular maintenance: Bridges must be regularly inspected and maintained to ensure that they remain safe and functional, particularly after an earthquake.

Overall, earthquake-resistant bridge design involves a combination of careful site selection, thoughtful engineering, and ongoing maintenance and inspection to ensure the safety of the traveling public.

Structural Calculations in SDC Verifier

SDC Verifier offers engineering consultancy services helping to solve the most complex calculation tasks with an automatic tool for code-checking according to global and local standards, including seismic rules and regulations. Any global or local standards can be used for verification and checks of a structure for strength (including complex non-linear problems solving), remaining lifetime / fatigue, weld strength, bolt / rivet and member checks, stability, plate buckling, beam buckling, and other specific checks.