Technical

Understanding Temporary Works

Author

John Fitzgerald

Director - Operations

Appreciation of the risks temporary works pose has increased across our industry. More and more clients are including provisions in contracts, mandating external reviews and approvals of temporary works. And it’s for good reason. Failures of temporary structures due to inadequate appreciation of the risks and critical design considerations have resulted in injuries, death and significant fines.

Decades ago, infrastructure failure or collapse could occur because of a number of factors, including:

Poor design and construction processes
Inferior or wrong material selection
Lack of maintenance and inspection; or
The unaccounted effects of natural disasters (i.e. strong wind, earthquakes, flooding etc)

Of course, with the rapid acceleration of technology and infrastructure design processes, this now occurs very rarely. However, if infrastructure is to fail (i.e. collapse) it is most likely to occur during construction.

As projects become more complex and their size and scope increase, effective and efficient temporary works design and implementation are critical to reducing worksite accidents, injuries and ensuring projects can be delivered on time and budget.

What are temporary works?

Temporary works is used to describe many things on a project, ranging from access roads, temporary site buildings, right up to formwork, falsework and complex lifting arrangements.

At FSC, we define temporary works as an engineered solution used to:

Support or protect an existing structure or the permanent works during construction; or
Support an item of plant or equipment; or
Support an excavation; or
Other systems that require an engineered approach to carry or transfer loads as determined through risk assessment.

Everyone has a role to play in ensuring temporary works are fit for purpose, including permanent works designers, temporary works designers, project engineers, senior engineers and supervisors, project managers and dedicated on-site temporary works teams.

Temporary works vs lifting

Temporary works and lifting operations are both high-risk elements of construction, and there is a degree of cross-over between them. Generally, lifting covers crane selection, lift studies, rigging and use of proprietary lifting equipment. Temporary works, however, covers ground support, custom lifting equipment and design of lifting points. See more in the graphic below.

Why is temporary works so important?

At FSC, we design and construct complex infrastructure projects, so we have a deep understanding of the intricacies of projects both great and small. From a design perspective, the risks of temporary works vs permanent works is assessed as follows.

Permanent Works Design:

Design Load Case: Ultimate Load Case (e.g. Extreme Wind, Earthquake, etc.)

Likelihood = Rare

Factor of Safety >2.0

Temporary Works Design:

Design Load Case: Serviceability Load Case (e.g. construction equipment, crane loads, piling rigs, etc.)

Likelihood = Certain

Factor of Safety can be ≤1.5

Put simply; temporary works is implemented in a controlled environment for a much shorter period of time than permanent works, and therefore is designed closer to the limit. Likewise, the construction of complex infrastructure involves the staged assembly that, unless done carefully, can result in loading elements in a manner not contemplated by the original designer.

Temporary works at FSC

Temporary works need to be considered upfront and fed into the design of permanent works. Early design engagement between the temporary works team and permanent works designers is crucial to the development of the design and understanding each parties roles and responsibilities. In doing so, we ensure a project’s safety and constructability resulting in a project that is delivered on time and budget.

Temporary Works design briefs are fundamental inputs – a poor design brief will result in redesigns and oversights that could potentially lead to injuries, budget blowouts and in some cases, lawsuits. A properly detailed design brief has to be produced by a competent engineer and reviewed thoroughly by the temporary works team to ensure all necessary assumptions are validated. A ‘back briefing’ is usually the best way to ensure that all parties’ expectations are aligned. Once constructed, a thorough inspection and sign off prior to the loading and unloading of temporary works are important steps that need qualified and competent people involved.

Having experienced engineers involved is critical as while every project is unique, most of the process, design and actual works aren’t. Engaging FSC can result in big time and cost savings through efficient design, design management and either re-use or adoption of methodologies from previous projects.

Approval for temporary works can potentially be a lengthy process, so plan early to avoid delays on your project and ensure your client’s requirements are well understood. Importantly, don’t forget to review the design assumptions and establish quality assurance (QA) of temporary works. QA documentations, routine inspections and maintenance are critically important to avoid oversights and worksite incidents.