The process of good design provides a structure that serves a purpose whilst protecting those associated with it throughout its lifecycle. Optimum design is more than structural adequacy.
Introduction – What is good design?
All structural engineers aspire to be good designers. Good design is much more than preparing calculations to size members strong enough to carry their assumed loading. Good design is not something achieved by repetition or routine but is something that creates a structure that:
- Is robust against a range of hazards that might be applicable
- Is functional
- Is safe and practicable to build
- Minimises in service degradations
- Permits degradation to be observed, safely assessed and managed
All designs involve a choice of solutions and some solutions are better than others. There are competing aspects in designs, so the optimal solution may be different depending on the values and criteria of clients and users.
Designer – A good designer has to be more than just competent
Competence can be described as the combination of training, skills, experience and knowledge that a person has and their ability to apply them to perform a task safely (HSE). Other factors, such as attitude and physical ability, can also affect someone’s competence.
Good designers must continually develop:
- Be specific about their training: plan and execute
- Necessary technical and practical
- Planning and organisational
- Appreciating the importance of site visits. For a design to be practical for construction and maintenance the designer must understand site issues
- Good theoretical technical knowledge applicable to their discipline
- An understanding and appreciation of the impact of costs and programme upon a project, eg Structural engineer technical articles on the Institution of Structural Engineers’ website
- Lessons learned – more is learned from failures than successes, much can be learned from the experience of others, eg Collaborative Reporting for Safer Structures (CROSS)
- Positive, can-do attitude
- Service provider
- An attention to detail in applying technical competence
- Recognise limitations
A good design process has more to it than purely numerical literacy and coming up with a single solution. There are numerous factors that have to be taken into account to ensure that a design is both appropriate and proportionate to the requirements, demands and controls that are and will be placed upon it.
No construction project is risk free. Risk can be managed, minimised, shared, transferred or accepted. It cannot be ignored
(Sir Michael Latham noted in Latham Report, 1994)
Risk is best managed in design in a proactive manner by those who have the direct ability to manage the risk. This is much better than being reactive, waiting until the hazards present themselves, as by then it can often be too late to address these effectively and efficiently. Even when it is not too late, the likelihood is that the impact upon programme, specification and cost will be significantly increased, as will be the pressure upon the design team.
There are three risk management components to be considered:
- Principles of prevention
- Risk identification and mitigation
- Communication of hazards and risk
1 What are the principles of prevention?
These provide a system to identify and implement measures to control risks. It is worth considering what this is and how it will work.
HSE Principles of Prevention guidance
These principles are a requirement of the Management of Health and Safety at Work Regulations and apply to all industries, including construction. They are repeated in the HSE Guidance on CDM, L153. They provide a hierarchical framework to identify and implement measures to control risks on a construction project and can be used by designers to identify better design choices from a health and safety perspective.
The general principles of prevention are to:
- Avoid risks
- Evaluate the risks which cannot be avoided
- Combat the risks at source
- Adapt the work to the individual, especially regarding the design of workplaces, the choice of work equipment and the choice of working and production methods, with a view, in particular, to alleviating monotonous work, work at a predetermined work rate and to reducing their effect on health
- Adapt to technical progress
- Replace the dangerous with the non-dangerous or the less dangerous
- Develop a coherent overall prevention policy which covers technology, organisation of work, working conditions, social relationships and the influence of factors relating to the working environment
- Give collective protective measures priority over individual protective measures and
- Give appropriate instructions to employees
(L153 - Appendix 1 The general principles of prevention)
Why? – It’s only by having an understanding of potential hazards before they present themselves and put someone in harm’s way, that something can be done to protect those who build, use and maintain structures.
What is a hazard? - A hazard is defined as something with the potential to cause harm, such as construction dusts, repeatedly handling heavy items, chemicals eg cement, some paints, working from a ladder, plant and tools etc.
What is a risk? - A risk is the likelihood of potential hazards leading to harm. This tends to be based on a judgement rather than a numerical value. The extent of any risk depends upon the likelihood of the hazard occurring, the potential severity of the resulting harm and the number of people who may be affected by the hazard.
An action or omission can protect from or allow hazards to manifest as risks. Risk management is about achieving the correct balance. See Figure 1.