2 - Eurocode limit state design Flashcards
(35 cards)
What is the main difference between geotechnical materials and structural materials like steel in design?
Geotechnical materials like soil are heterogeneous and variable, while structural materials like steel are homogeneous and have consistent properties.
Why is it difficult to predict the behavior of soils in geotechnical design?
Soils are heterogeneous, meaning their properties can vary significantly over short distances, making them unpredictable.
What is a crucial challenge when collecting soil samples for geotechnical analysis?
It is difficult to ensure that a sample accurately represents the soil conditions at the entire site, as soil properties can change even over small distances.
What does Eurocode 7 provide for geotechnical engineers?
Eurocode 7 provides guidelines for accounting for the uncertainties in soil behavior and design, ensuring safe and economical geotechnical structures.
Why is it important for geotechnical designs to account for both safety and economy?
Over-design can be costly both economically and environmentally, while under-design could lead to catastrophic failure.
In an ideal world, how would a geotechnical structure be designed?
The applied loads would be less than the ground’s resistance, with no uncertainty in the measurements or calculations.
What happens if uncertainty is not considered in geotechnical design?
Uncertainty could result in a dangerous overlap between the applied load and resistance, creating a failure zone where the structure may collapse.
What is the significance of the friction angle (φ′) in geotechnical design?
The friction angle is a key soil property that influences the resistance of foundations, and errors in its testing can introduce uncertainty in design.
What is the “failure zone” in the context of geotechnical design?
The failure zone is the area where the applied load exceeds the resistance of the soil, leading to potential failure of the structure.
How does Eurocode 7 help minimize the risk of failure in geotechnical designs?
Eurocode 7 applies partial factors to account for uncertainties in loads, material properties, and resistance, ensuring that the design remains safe and reliable.
What is the goal of the Eurocode 7 design process?
To ensure that the probability of failure is acceptably low by minimizing overlap between applied load and resistance distributions.
How does Eurocode 7 account for uncertainty in design?
By applying partial factors to loads, material properties, and resistances based on the level of uncertainty.
What are partial factors in Eurocode 7?
Multipliers applied to characteristic values to account for uncertainties and reduce the probability of failure.
What is inherent variability in geotechnical design?
The natural randomness in soil properties or environmental conditions, which can vary spatially or temporally.
What causes measurement error in geotechnical engineering?
Imperfect measurement tools, sample disturbance, or inaccuracies in lab testing.
What is model uncertainty?
Uncertainty from simplifications in the models used to predict soil behavior, such as using the Mohr-Coulomb model.
What is statistical uncertainty in geotechnical design?
Uncertainty from limited data, such as too few site investigation samples or insufficient testing.
How can statistical and measurement uncertainty be reduced?
By collecting more high-quality data and conducting more site investigations or lab tests.
What is the role of engineering judgement in Eurocode 7?
It allows engineers to interpret uncertain data and apply experience to make informed design decisions.
Why might national annexes influence Eurocode 7 design choices?
They account for local practices, historical performance, and regional experience, tailoring the Eurocode to specific conditions.
What is the main purpose of Ultimate Limit State (ULS) Design?
To ensure structures resist failure or collapse under applied loads.
What is the difference between ULS and SLS?
ULS is about preventing collapse; SLS is about controlling deformation/movement.
What is the basic ULS inequality?
ΣQ ≤ R(X), where Q = actions and R(X) = resistance as a function of material properties.
How is uncertainty accounted for in ULS design?
By applying partial factors to actions (γA), material properties (γX), and resistances (γR).
