Barnabas Ilko

The official link for the call can be found here Temporary works (icevirtuallibrary.com)

Dear TWf CoP members, We received the following message from the TWf UK recently: Civil Engineering is planning a special issue in 2023 on the latest developments in temporary works, one of the most challenging yet least recognised fields of engineering. In addition to providing short-term support and protection for built assets throughout their lifecycle, often on a vast scale, temporary works include non-permanent structures for all kinds of human activity. From field hospitals and demountable stadia to emergency bridges and flood barriers, society has come to depend on the ingenuity of temporary works engineers. Common to most temporary works design is a detailed understanding of often fast-changing load conditions and a need for safe, rapid and sustainable assembly and disassembly. There is also a significant overlap with permanent works design, as structures that are more resilient to temporary loading conditions need less in the way of temporary works. The journal is calling for papers on the latest thinking and practice in temporary works, ranging from innovations in planning, design and monitoring to novel methods, materials and applications. They can be in any relevant engineering field, including structures, marine, geotechnical, transport and process, and for any application, from falsework and formwork to ground support, cofferdams, gantries, jacking systems, conveyers and access platforms. I have attached the slides that were provided with the message. If you are interested in putting forward a paper, please get in touch with me or with the individuals noted on the slides. Once I receive the official call via the ICE webpage, I will post it here. 21 12 10 _ICE TW Special Edition_ TWf_ ASt_Initial notification v 1.pptx

@Anthony McLellan, thank you for the suggestion. We are in the process of gathering information on various types of TW and requirements relating to these structures/equipment by various codes. We have a working document and awaiting the issue of the new wind code as well as the new formwork standard. This event will likely be held in Q4 of 2021.

@Shane Groom, thank you very much for taking the time to review the document. We will incorporate your comments to the document.

We tend to refer to the HSE (BS 5975:2019 Code of practice for temporary works procedures and the permissible stress design of falsework (bsigroup.com), CDM (Construction - Construction Design and Management Regulations 2015 (hse.gov.uk) and BS5975 (BS 5975:2019 Code of practice for temporary works procedures and the permissible stress design of falsework (bsigroup.com) that provide guideline on good practice in the UK. We do not have the equivalent of CDM and BS5975. The procedural control document is usually established by contractors and is driven by previous experience of individuals and organisations. Some clients might require certain TW requirements in the contract and contract documents.

Unfortunately, there is currently no such standard or general guideline (at least none that I know of) that would outline the delineation between temporary and permanent works. Usually it is set by the clients on projects and is passed down to contractors via contracts and contract documentation. This means it can vary from project to project and industry to industry. The best course of action is to negotiate the scope with the client at the beginning of the project. If you would like to gather more information on procedural control, have a look at the free guideline published by TWf NZ (https://secure.chasnz.org/downloads/resources/TemporaryWorksProceduralControl_GPG_.pdf) You can also find more reading on this topic on the TWf UK's webpage. I would highly recommend reading documents in the resources folder (Library - Temporary Works Forum (twforum.org.uk) Lastly, a good Australian based document is the Safe design of structures (Model Code of Practice: Safe design of structures | Safe Work Australia) that outlines the roles and responsibilities of designers. Equally applicable for PW and TW engineers.

@Steve Douce, Shane's response is spot on. You have a few options to choose from and I would recommend looking up the research paper by C H Wang and L Pham as that is the basis of the tables in the ABCB Standard. That particular standard does not cater for all temporary works and you might want to take a different approach, or as suggested, a performance based approach. I have no experience with mobile structures, but I would think the same rules apply as for static structures. If you are using an equipment by a supplier, they should have specification for certain use. If it is custom built, I would use the above advice. I would note one item though. You should assess the risk of the equipment toppling over if the wind picks up before you can fix it down. You should assess what is in the surrounding and if failure of the equipment can lead to other H&S hazards, I would recommend using a higher FoS for overturing.

@Tony Geldart, just a few other items you might want to consider: You will need to consider time and how long the shoring box is going to be used in a particular location You will need to allow for potential water pressure or saturated material you will also need to consider nominal surcharge loads around the trench (this might be stockpiled material, vehicular loading or other) The best would probably be to use a K0 value for the calculation of the pressure (this might lead to higher than 40kPa pressure though) All in all the best option might be to have a table of certain load cases for various depths and have 2, 3 or 4 types of shoring boxes. This might be more economical, easier and compacter to transport and easier to handle on site.

First of all, consider it. I usually revert back to WHS (and OHS) acts that explain designers' primary duty of care. PW designers should have one way of building their design safely. Maybe the builders have better, faster or safer ways, but there should be at least one solution for the build. I am not aware of any legislation that would specifically mandate considerations for TW or constructability/construction staging.

I am not familiar with the geotechnical strength reduction factors in this code. Will leave it up to someone more knowledgeable in this field to respond to this query.

Via good contractual terms and conditions as well as collaborative clients. There is no magic solution here.

Under all circumstances, design work needs to be checked internally. At least this is what I am used to. The level and type of check might vary dependent on the complexity of the task. It does not necessarily have to be a Chartered Engineer. Unfortunately, there is no Chartered Temporary Works Engineer in Australia. I am not saying that the engineer should not be chartered, but their and the company's competency should be queried. To provide greater assurance of the competence of those carrying out temporary works design activities, an internal or industry guideline could be developed to help contractors and subcontractors to choose the right companies and individuals. It should be a competency-based matrix that focuses on temporary works design. The designer and checker should sign off on the design in my opinion. BS5975 has a relatively straightforward approach to this and outlines who needs to be the checker for various design tasks. You can find it in Table 2. See snip below.

A very good first step would be to educate the clients about the potential risks and how it would impact their revenue. That might be a great first step.

I am a little bit confused by the unexpected loads such as temporary storage comment. I assume the question might be related to impact loading on structures from vehicular traffic, load being dropped from floors above if no protection fans are installed below, loads dislodging while lifting with tower crane. Or a usual item we debate which is loading on overhead protections from vertical and lateral loads. In case you are after loads falling on a temporary structure, AS1170.1 should be used as a first step. The commentary will explain how to calculate these forces, simple physics. In case you are after storage and impact loads on falsework, please refer to the Concrete Institute of Australia's practice note Z36 which has a very good explanation of how these loads should be calculated.

As mentioned, in the table time is represented by the design life of both, time allowed for planning, legacy and warranty liabilities and when they lapse. In very short, there is usually more time allowed for the design and planning of PW versus TW.

I am pleased to hear you enjoyed the presentation. This is a very broad question. Depends on the form of temporary works and their intended use. For example hoarding for overturning at least a factor of 1.2, for tower crane overturning a factor of 1.5, for a temporary retention system's overturning can be 2.0 and temporary lifting elements that are moved on rough terrain by tracking vehicle can be 4.0 or more. So there is a wide range of factors from low to relatively high dependent on the application.

This is a very broad question and really depends on what temporary works I design and what loadings I will have on the particular element. It can be overturning, friction, sliding, lateral stability and many others.

The British Standard I referred to is BS5975 Code of practice for temporary works procedures and the permissible stress design of falsework. It has three parts: General Procedural of Temporary Works Falsework This code provides guidance for falsework design in the last part. Some of the Australian design standards relating to temporary works are the following: AS 1418.4-2004 Cranes, hoists and winches Tower cranes AS/NZS 1576 Scaffolding (multiple volumes) AS 1657:2013 Fixed platforms, walkways, stairways and ladders – Design, construction and installation AS 3610:1995 Formwork for concrete AS 3850:2003 Tilt-up concrete construction AS 2601-2001 The demolition of structures AS 4991-2004 Lifting devices - SAI Global It really depends on what you are after though. There are a lot of practice notes and guidelines nationally and internationally to research. Feel free to click through the following links where you might find interesting further reading International TWF's - Temporary Works Forum (engineersaustralia.org.au)

I start with some of the items that can be improved in my view. I think there are too many simple structures and very low-risk structures being independently reviewed by another organisation. At the same time, a lot of organisations have robust internal Q&A procedures. This means that the ‘independent review’ could be carried out in house by another team member. A competency-based matrix could be developed for this to work where competent engineers and consultants can review design work in-house for those low-risk simple design works. This would mean that for low-risk simple and repetitive design elements the design and certification process could be fast-tracked which reduces delays on site. On a flip side, when things get medium to high-risk it is important to have a fresh set of eyes going over the design. This is especially important when the design codes are not well defined and engineering judgement plays a key part during the design process.

This is a very interesting question. Under the WHS (or OHS in some states) act, designers should design structures in a manner that ‘ensures, so far as is reasonably practicable, that workers and other persons are not exposed to health and safety risks arising from the business or undertaking’. Furthermore, the designer must ensure that structures are designed to be safe when used as a workplace during its lifecycle. The designer has to provide information to anyone issued with the design. It has to clearly state the purpose of the design, such as load constraints. It has to highlight the results of any calculation, testing or analysis and all conditions necessary for the safe use. In other words, all this means that they are liable for ensuring what they design is not going to cause harm to people. The other part of your question relates to execution on site I assume. When the design is certified and handed over to the contractor or subcontractor, they are also obliged by the WHS (or OHS) act not to create an unsafe work environment. For example, suppose they alter a temporary works element or do not get them designed (unless it is not proprietary product with specified installation for the intended use). The TW element fails and causes harm to people on site or the wider public. In that case, they might be in breach of their primary duty of care if something goes wrong, especially if they do not ask the designer whether the proposed changes are acceptable and explain the proposed changes.

There are a number of risks involved such as wear and tear (corrosion, damage, perforation etc.), reduction of load limit over time or losing components and replacing them with different components that might not be meeting the manufacturer's specification or requirements. The designers of proprietary elements usually overdesign TW elements and allow for some of the above mentioned items. Some elements need to be periodically retested, such as lifting beams and equipment to ensure they still meet the SWL or WLL that is specified for the element. Different TW components pose different risks. Non-proprietary, non certified design elements should be tested before reuse in my opinion, but it really depends on the circumstances. History can show us a few failures where reused temporary works elements were part of the problem. I would recommend you have a look at the causes of the Barton Bridge scaffold collapse (Manchester, UK, 1959).

I would also note that it is usually soil and project specific. The bentonite slurry used for driving the pipes into the ground could vary through a single drive. It is important to talk to a 'mud doctor' or specialist that can give advice on the composition of the slurry mix.

I agree with Martin's comment and would add that the basement structures should be designed as 'stand alone' structures without reliance on neighboring properties and structures. Those structures could be subsequently modified, demolished or new building/s built in its place and it should not have an impact on the structure you design. In any instance involvement of legal and commercial experts is a reasonable step to take.

It depends on how we approach it. In general I would say the tower crane itself is a machine that sits in its own category. When we talk about the base and ties, I would consider them as temporary works elements. The crane can be in temporary states as well during erection and dismantling.

This is a very complex question and topic. There is no simple answer for it. In Australia there is no code or procedure that would outline the exact roles and responsibilities. Usually they are set by clients and are outlined in the contract documents via management plans, procedures, references to international codes/practice guidelines etc. Based on the WHS legislation the designer needs to ensure so far is reasonably practicable to minimise the health and safety risks of the workers, stakeholders and the wider public. When taking a more practical approach, for example temporary stability of structures would be usually up to the temporary works engineer to identify and resolve. In better situations the permanent works engineer might indicate that some critical elements need to be checked or discussed during the temporary state. On some occasions with the modification of permanent works or integration of temporary works into permanent works could be a solution, but it usually requires close collaboration and time spent together between the head contractors and PW, TW engineers. It is very rare when this happens. When looking at the UK, HSE outlines the legal obligations, CDM the responsibilities and BS5975 provides guidance on the management of temporary works. The combination of these provides a relatively clear indication for each parties what they need to do when, but also involves clients and other stakeholders in the process.