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An introduction to prevention through design

By establishing systems to identify and implement measures to control risks, the engineer can ensure that a design is both appropriate and proportionate to the requirements, demands and controls that are and will be placed upon it.

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:

Training

  • Be specific about their training: plan and execute

Skills

  • Necessary technical and practical
  • Planning and organisational
  • Communication
  • Negotiation

Experience

  • Appreciating the importance of site visits. For a design to be practical for construction and maintenance the designer must understand site issues

Knowledge

  • 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)

Attitude

  • 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:

  1. Principles of prevention
  2. Risk identification and mitigation
  3. 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:

  1. Avoid risks
  2. Evaluate the risks which cannot be avoided
  3. Combat the risks at source
  4. 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
  5. Adapt to technical progress
  6. Replace the dangerous with the non-dangerous or the less dangerous
  7. 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
  8. Give collective protective measures priority over individual protective measures and
  9. 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.
 


Figure 1: Balancing Risk

What to do


Figure 2: Five steps to managing risk

An iterative process: all design follows the loop shown in Figure 2.

Identify hazards - these might not be obvious or immediate as belonging to the task or work activity. It is really important to think about the project in the broader context, particularly consider the project in its geographical location and the wider site. Risks associated with an activity eg falls into excavation, may be identified, however quite often those associated with the wider context of a site, eg near a major roadway, main distribution energy routes etc, that cross the site may be missed. Consider the surroundings and physical environment, eg utilities, overhead lines, gas pipelines, drainage, or infrastructure such as railways or highways. Consider also the hazards associated with the detail of the execution of the design, temporary instability, work at height, use of chemicals like cement/grout, welding, material weights.

Assess the risks - prioritise the risk management effort that has to be applied to the risks that have been identified and the stage in the design process that these are going to be addressed. Decide which risks are best left to the detailed designers to manage eg rebar cage instability can be addressed by the rebar detailer but do not leave them guessing, identify the risk in the information provided.

Control the risks - identify sensible and reasonably practicable design choices to reduce risks associated with building the design

  • Not expected to anticipate unforeseeable risk
  • Determine whether a risk can be designed out?
  • Does that bring other risks?
  • Is the revised proposal now considered to be the safest reasonably practicable design ie is the risk ALARP - as low as reasonably practicable?
  • Provide practical information that protects people from harm or injury

Record findings - provide a record of what has been considered and the outcome, the steps taken and what is left to be taken care of, ie the residual risk. Make sure that the people who need this information receive it (in the UK provide information about significant residual risks to the Principal Designer).

Review controls - carry out reviews periodically and as conditions and circumstances change through the project or asset life.

Whilst looking at specific hazards there are also those that have a wider impact, these may relate to utilities, infrastructure and contamination whether these are on the site or in the vicinity of the site.  Consider also asset degradation and ensure that there is a record of reviews required captured in the project information (in the UK, the Health and Safety File).

How to go about it
 


Figure 3: Hierachy of hazard control measures

E – Eliminate  
Design out hazards or incorporate risk control measures
R – Reduce     If not reasonably practical to eliminate the hazard, look to minimise the risk
I – Inform         If significant risks remain, provide information on these risks
C – Control      Either through engineering or administration introduce physical or procedural controls

Generally, best addressed at source and with early intervention. Some may require to be addressed only the once whilst others require revisiting throughout the life of the project or structure.

Design risk management – implements the process and procedures to eliminate, reduce the hazards and pass on the information of residual risks. This provides a record of these, the steps taken, and finally what’s left to be taken care of. The Institution of Structural Engineers is planning to publish a guidance document which will provide information pertinent to this process.

2   Risk identification and mitigation

What is the risk?

Hazards can occur in all phases throughout the life of the project and structure. These hazards create risks that have to be identified and managed by implementing measures to avoid or control them.


Figure 4: Asset life cycle phases

Designers are in a position to significantly reduce the risks and lifetime costs during the design and construction phases and the subsequent phases of operation and end of life. The duration and costs of the design and construction phases are considerably less than those of the operation phase, early decisions can influence the whole life costs and ease of operation.

All through the different phases of a project or asset life cycle the risks will require further reviews to re-evaluate and reassess. Some existing risks may have been addressed and closed, others may require a change in controls and measures, new risks may arise as conditions and circumstances change.

Figure 5: Project risk management phases

Project workshop

To ensure that the risks are fully identified, shared, and understood, the best approach is to carry out a project workshop following a thorough schedule. The intention is to ensure that nothing is over-looked, and all hazards are identified, and the risks recognised. All hazards can be recorded, those that are within the remit of the design team or those that may belong to others. Some may be so remote that they do not have any perceptible impact upon design, activities or operation, however if these are recorded it assists in ensuring a thorough review.

A record of risks, detailing control measures implemented assists in any future reviews, whether considering existing or new risks. This record ensures a consistent and transparent approach is adopted to the management of the risks.

Design risk management – hazard elimination and management record

The design risk record or hazard elimination and management record provide details of all the possible design hazards that could impact upon the project and those associated with it throughout the life of the project or the structure. Risks are identified, potential impact determined, mitigation and control measures are applied, further information provided where appropriate, to provide an adjusted potential impact. Details of these and any significant residual risk are recorded for further review and use. This record could look like Figure 6.

Figure 6:  Hazard elimination and management record

As well as considering the execution and maintenance risk as design choices are being made, regular design reviews are undertaken in collaboration with other designers throughout the preconstruction (design) phase. Clear notes of significant risks are included on drawings/CAD designs/BIM. General or generic statements must be avoided.

Significant risks

Not necessarily those that involve the greatest risks, but those (including health risks) that are not likely to be obvious, are unusual, or likely to be difficult to manage effectively.

These reviews continue throughout the construction phase and into the operation and use phase as design is being carried out, including trade contractor design.

The Structural Engineer provides Technical Guidance Notes and other series (inlcuidng Managing Health & Safety Risks) which relate to specific hazards..

All the relevant information has to be shared and a record maintained. The record provides details of what has been considered, the outcome and what information has been shared and with whom.

3   Communication of hazards and risks


What to communicate
  • Location and nature of hazards, who is at risk
  • Risk
  • Design choices adopted to reduce the risk


For each of the above it is important that the risks are prioritised. The specifics must be clear, including ownership, as well as details of any underlying conditions and assumptions that are being relied upon.
 

How
  • Periodic review and update of hazard elimination and management record
  • Improving health and safety outcomes in construction making the case for Building Information Modelling (BIM)

Whom

  • Client
  • Principal Designer
  • Design team, including contractor appointed designers and temporary works designers
  • Contractors (main contractor, contractors/subcontractors and workers)
  • End user

 

Figure 7: Information flow

In summary

A good design may be seen as a linear process if viewed simplistically. It is however a more complex and iterative process. This means going through the processes more than once to arrive at the optimal design solution to manage the risks and to satisfy the particular requirements that circumstances or conditions demand.  The more experienced the designer, and the earlier and the better input from the Principal Designer, the fewer iterations will be required.

Hazards are best addressed at source and with early intervention. An understanding of the potential hazards and risks that can present themselves during a project will assist in arriving at a safe and healthy design, for all those associated with the project or asset life cycle.

Clear lines of communication with the information being relevant, current, readily available and accessible through all phases of the project will keep all parties well informed.    

The CDM objective of “right information, right people, right time” cannot be overstated.


References/ further reading
Constructing the Team, Latham Report, Sir Michael Latham, published in July 1994

Managing health and safety in construction, Construction (Design and Management) Regulations 2015. Guidance on Regulations, L153, HSE

Risk assessment: A brief guide to controlling risks in the workplace, INDG 163(Rev4),    HSE

Improving Health and Safety Outcomes in Construction: Making the Case for Building Information Modelling (BIM) HSE

Managing risk and risk assessment at work: Steps needed to manage risk, HSE

The Structural Engineer, Technical Guidance Notes and other series

Collaborative Reporting for Safer Structures (CROSS)

Chris Farrell and Julia Allison
Safety, Health and Wellbeing Panel
 

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