Lecture 4

Question 1

11. Why do you think we desire a precise, mathematically-acceptable definition to safety, and why is this goal far from straightforward when all factors are taken into consideration

Answer 1

• Want a precise definition for safety for clarity and consistency for communication between different sectors. Also allows for objective evaluation. The use of the Eurocodes eliminate technical obstacles to trade and harmonisation of technical specifications.
• However, it is not straightforward due to the balance between safety and economics. Eurocodes can be viewed as a balanced economy against safety and quality, while accounting for legal and moral duty.

Question 2

12. What are five sources of uncertainty that are at the core of all design activity when striking the right balance between quality, safety and economy

Answer 2

• About loading
• Material strengths
• Structural dimensions
• Accuracy of calculations
• Effect of time (durability )

Question 3

13. What is the basic requirement of Robustness

Answer 3

• The structure will not be damaged by events such as explosions, impacts, or the consequences of human error to an extent disproportionate to the original cause. – no failure caused by human error.
• It gives way of avoiding potential damage: eliminating hazards to which structures can be subjected, selecting a structural form that has a low sensitivity to hazards, a design that can survive adequately the accidental removal of an induvial member, a structural systems that will collapse without warning.

Question 4

14. What should the fire engineering of a multi-storey structure for office workers enable to happen in the event of major fire incident

Answer 4

• Structural members have adequate fire resistance, for a period of time. Demand by the EN 1990
• There will be an increased load-bearing capacity, large movements and constraint force structural integrity needs to withstand.
• The structural integrity remains adequate in order for: evacuation of occupants, protection to fire-fighters, protect the buildings and adjoining property form fire spread.

Question 5

15. Which basic requirement is a reason to specify, for every structure, an indicative design working life, and why do you think the longest design working life of 120 years is for monumental buildings, highway and railway bridges and other civil engineering structures? Why will the cost of these structures be increased by these long design lives

Answer 5

• The requirement to list its designed working life for different structures is to allow for appropriate maintenance. Understanding the structures durability will be economical.
• 120 years for … is due to their high expenses to design and re-construct. Having a longer working life will be more economical as less maintenance and money will be spent on repairing and replacing sections. These structures themselves are expensive to build.
• The cost of these structures increases due to better design and materials used.

Question 6

16. Listed in Slide 4-14 are the nine interrelated factors that shall be considered to ensure an adequately durable structure. In a numerical order they are

Answer 6

1. Intended and future use of the structure
2. Required performance criteria
3. Expected environmental influences
4. Composition, properties and performance of materials
5. Choice of structural system
6. Shape of members and structural detailing, and buildability
7. Quality of workmanship and level of control
8. Particular protective measures
9. Maintenance during the intended live.

Question 7

17. In the Limit State Design Approach the Eurocode expression, applicable to a supported steel beam with several actions applied, failing ultimately with a ductile plastic hinge forming a mid-span, is Ed = E(F1Fk1, F2Fk2,…)  Rd = R(Xk/M). Define the terms in this expression, and state which side of ‘’ usually gives the designer the greatest management of uncertainty and, therefore, risk

Answer 7

• Rd is the calculated design resistance (design strength) of the whole structure or its components.
• Ed is the effect of the design actions (design loads) on the whole structure or its components
• 1F1K1= Fd1 is the design load for the first action where F1 is the partical factor to the characteristic load
• Xk is Fck is the charactistc strength of the steel and m is the partical factor for steel for resistance of cross section
• R > E as R is the calculated resistance and E is the effect of the actions. This will be when no uncertancies.