Week 9: Risk And Failure Flashcards
Define a limit state in structural engineering.
A limit state is the point at which a structure no longer fulfills its design criteria.
Describe the purpose of limit state design.
Limit state design ensures that a structure is fit for purpose, at an appropriate degree of reliability.
How can structures fail according to limit state design principles?
Structures can fail when the applied actions exceed the resistance capacity, violating the limit state conditions.
Explain the significance of the characteristic value in limit state design.
The characteristic value represents a specific level of action or resistance, typically the 95% value, used to assess safety and reliability.
What role do safety factors play in limit state design?
Safety factors are used to account for uncertainties in actions and resistances, ensuring that structures remain safe under various conditions.
Describe the two categories of limit state in structural design.
The two categories of limit state are Ultimate Limit States (ULS) and Serviceability Limit States (SLS). ULS concerns the strength and stability of the structure to prevent catastrophic failure, while SLS addresses design criteria that are not safety critical, focusing on comfort and usability.
How do Ultimate Limit States (ULS) ensure safety in structures?
Ultimate Limit States (ULS) ensure safety by preventing catastrophic collapse through considerations such as loss of static equilibrium, local failure due to excessive forces, fatigue failure, and ground failure.
Define Serviceability Limit States (SLS) in structural design.
Serviceability Limit States (SLS) refer to design criteria that focus on the usability and comfort of a structure, addressing issues like large deflections, uncomfortable vibrations, and excessive cracking.
What types of failures are considered under Ultimate Limit States (ULS)?
Under Ultimate Limit States (ULS), failures considered include loss of static equilibrium (toppling or buckling), local failure due to forces exceeding strength (crushing or rupture), fatigue failure (long-term cracking and splitting), and failure of the ground (soil liquefaction or excessive settlement).
How can excessive cracking affect the serviceability of a structure?
Excessive cracking can affect the serviceability of a structure by compromising its usability and comfort, leading to potential discomfort for occupants and possibly indicating underlying structural issues.
Describe the main issue that led to the closure of the Millennium Bridge in London shortly after its opening.
The Millennium Bridge was closed after two days due to lateral resonance caused by lateral synchronization among pedestrians.
How was the issue of lateral resonance on the Millennium Bridge resolved?
The issue was resolved by the addition of viscous dampers to the bridge.
Define the consequences of the Mecca crane collapse in Saudi Arabia in 2015.
The Mecca crane collapse resulted in 111 deaths and 394 injuries, highlighting the dangers of construction during adverse weather conditions.
What factors contributed to the Mecca crane collapse during the Hajj in 2015?
The collapse was caused by a combination of high winds, human error, and poor planning.
Explain the significance of the events surrounding the Millennium Bridge for understanding pedestrian dynamics.
The events led to a greater understanding of pedestrian dynamics and resonance, influencing future bridge designs and safety measures.
Describe the Grenfell Tower incident that occurred in London in 2017.
The Grenfell Tower incident was a catastrophic fire in a tower block in London that resulted in the deaths of 72 people. It was exacerbated by factors such as combustible cladding, poor window detailing, and a ‘stay put’ evacuation policy.
Identify the main factors that contributed to the severity of the Grenfell Tower fire.
The main factors that contributed to the severity of the Grenfell Tower fire included combustible cladding, poor window detailing, and the ‘stay put’ evacuation policy.
How many people lost their lives in the Grenfell Tower fire?
A total of 72 people lost their lives in the Grenfell Tower fire.
Define the ‘stay put’ evacuation policy in the context of high-rise buildings.
The ‘stay put’ evacuation policy is a fire safety strategy that advises residents to remain in their apartments during a fire, assuming that the building’s design will contain the fire and smoke.
What were the consequences of the Grenfell Tower fire for fire safety regulations?
The Grenfell Tower fire led to increased scrutiny and changes in fire safety regulations, particularly regarding the use of combustible materials in building cladding and the effectiveness of evacuation policies.
Describe the Grenfell Tower fire and its impact on building regulations.
The Grenfell Tower fire in London in 2017 was a catastrophic incident that resulted in the deaths of 72 people. It highlighted significant issues such as combustible cladding, poor window detailing, and an ineffective ‘stay put’ evacuation policy. This tragedy led to the introduction of new building regulations, a change in safety culture, and adaptations to thousands of existing buildings.
How did the Grenfell Tower fire reveal shortcomings in building design and regulation?
The Grenfell Tower fire exposed critical flaws in design knowledge, regulatory frameworks, and enforcement practices. Factors like the use of combustible materials and inadequate evacuation strategies underscored the need for improved safety standards.
Define the term ‘stay put’ evacuation policy in the context of high-rise buildings.
The ‘stay put’ evacuation policy is a fire safety strategy used in high-rise buildings where residents are advised to remain in their apartments during a fire, assuming the building’s design will contain the fire. This policy was criticized after the Grenfell Tower fire for its failure to protect residents.
What factors contributed to the severity of the Grenfell Tower fire?
The severity of the Grenfell Tower fire was exacerbated by several factors, including the use of combustible cladding, poor window detailing, and the implementation of a ‘stay put’ evacuation policy, which ultimately failed to ensure the safety of residents.
Do you know the number of casualties from the Grenfell Tower fire?
The Grenfell Tower fire resulted in the tragic loss of 72 lives.
Describe the Grenfell Tower fire incident.
The Grenfell Tower fire occurred in London in 2017, resulting in the deaths of 72 people due to a catastrophic fire exacerbated by factors such as combustible cladding, poor window detailing, and a ‘stay put’ evacuation policy.
How did the Grenfell Tower fire impact building regulations?
The Grenfell Tower fire revealed significant shortcomings in design knowledge, regulation, and enforcement, leading to the introduction of many new building regulations and a change in culture regarding fire safety.
Define the main factors that contributed to the Grenfell Tower fire.
The main factors contributing to the Grenfell Tower fire included the use of combustible cladding, inadequate window detailing, and the implementation of a ‘stay put’ evacuation policy.
What was the outcome of the Grenfell Tower fire in terms of building safety culture?
The outcome of the Grenfell Tower fire included a shift in building safety culture, prompting adaptations in thousands of existing buildings to enhance fire safety measures.
Do you know the number of casualties in the Grenfell Tower fire?
The Grenfell Tower fire resulted in 72 fatalities.
