Engineering Archives - Hawkins Forensic Investigation

A Structure is Only as Strong as its Weakest Link

Matthew Carrington — Mon, 09 Mar 2026 15:41:10 +0000

Construction projects of all kinds, over a wide range of scale, require structural engineering design input to direct the way they are built. The structural engineering design is almost always implemented in conjunction with architectural design, other specialisms, and the knowledge and skills of the contractor and specialist sub-contractors.

Civil and structural engineering design is a complex field where many engineers are highly qualified, with professional accreditations from engineering institutions after several years of industry experience, following a university degree. However, there is no safeguard against less qualified or less experienced people also trading as civil or structural engineers.

This article discusses the typical aspects of structural engineering design that are required in most construction projects. It includes case studies investigated by Hawkins, where the action of the structural engineering designer could be at fault.

“The strength of a structure depends on the strength of its elements and the way they are joined together.” – Gustave Eiffel

Weak Links

Some building faults might be related to issues with the structural engineering design, or omissions in it. Others may be due to the actions of other parties in the design or construction team, or faulty materials. The design process for each project must consider all the potential modes of failure of the structure. Any one thing could be missed in the design process and cause an issue with the performance of a building. Sometimes, a combination of circumstances needs to coincide to cause a failure. Almost every construction project is a prototype due to the varying combinations of building shape, location and formation of the team performing the work. The following sections describe five links in the structural engineering design chain.

1. Design Issues

It is possible for a structural engineer to completely design the strength and stiffness of the individual elements for the structure but miss a wider issue that can lead to damage or failure.

For example:

The lateral sway stability of part of a building can be reduced by replacing the vertical support from a solid masonry wall with a steel beam;
Loads on a gravity retaining wall at a change of level of external ground that were not allowed for in the design can occur if drainage is not detailed (Figure 2);
Overall structural capacity can be exceeded if a whole category of loading is omitted, such as wind or snow load.

2. Site Issues

There are cases where the design might have considered the typical scenario for the type of structure they designed, but there was something different on site that they did not allow for.

For instance:

If a designer assumed that a wall was a cavity brick/block wall, when it was in fact a solid stone wall, then the wall would be heavier than assumed. A beam installed to create an opening and support the wall could then be overloaded;
A wall that was retaining higher ground could collapse if the rest of the building that was providing lateral support to the wall was removed without considering the interaction (Figure 3);
The effect of a row of small trees on building foundations movement can be greater than the individual trees;
Different ground conditions can have more or less aggressive reactions to the concrete they are in contact with. The wrong mix of concrete might look suitable initially, but in aggressive ground conditions, it can degrade over time.

3. Calculations

Sometimes, the structural designer can miscalculate their designs.

Examples might include:

An assumed length of a beam was not updated in the design calculation when the length of the opening was longer than first planned;
In a structural assessment, the engineer might have used the material properties for normal density concrete when the element was lightweight or aerated concrete, which can only provide lower strengths;
In computer aided design, using finite-element modelling or calculation sheets prepared by a software company, the wrong input for the situation being built can lead to an understrength member. This might arise from one wrong tick in a box within the software options.

4. Stages of Design

There have been cases where the structural engineer provided sufficient design information for a preliminary stage of the design, such as submission to building control, to gain approval for the project to proceed. Then, the client or contractor did not go back to the engineer to ask for detailed design and construction details, or did not correctly apply the submitted preliminary design.

These cases have included:

Where relative positioning between structural members and their supports was critical to the building performance, but the individual member capacity design was sufficient to pass the building control plans check;
Where the order of construction would be critical to the capacity of the structural members. During construction, an unrestrained steel beam would have considerably less capacity to carry vertical loads until it was restrained by the floors to both sides (Figure 4);
Often, changes that appear to make the building simpler to construct can introduce complications to the way they would perform. The changes would need further structural design and could cause a problem if the designer had not been notified.

5. Missing Design

We have investigated cases where an item was overlooked as needing civil or structural engineering design. This can occur at interfaces between specialist contractors’ responsibilities:

i. Roof vents (Figure 5);
ii. Cladding boards (Figure 6).

These will likely perform satisfactorily in normal conditions but might not be sufficient for high winds or rain. This would likely present in the failure of several of the same items. Identifying the fault early might allow the rest of the items to be remediated.

Failures can exhibit a range of states of distress and at different times in the life cycle of a building.

The questions which must be considered when investigating the root cause of the failure will vary with the scenario, including:

Was the designer provided all the necessary and correct information?
Should the designer have found out the correct information by looking into the situation more than relying on drawing or reports they were provided?
Was there information that the designer needed to show in more detail to a competent contractor?
Was there a coordination responsibility to make sure the correct information was provided?
Should a competent contractor have given feedback to the designer that the situation was not as allowed for in the design?
Did the client appointment limit how much the designer could do in any of these aspects?

In some cases, we have been able to advise that urgent action needed to be taken to avoid further damage occurring. This can save people spending time in a position of danger looking for material damage or conducting intrusive investigations that might tip the situation further towards collapse.

“The best design is the simplest one that works”. – Albert Einstein

Conclusions

Sufficient structural engineering design relies on considering all the relevant design issues and all the particular conditions on the site. The structural engineer must complete the design calculations correctly and present the construction information clearly to the contractor. Greater levels of detail are required for the construction issue of the structural drawings than for the building control submission. That is a situation where misunderstandings can arise. Also, there are proprietary and peripheral items related to construction that might not be part of the scope of a structural engineering appointment but would have benefitted from a review by a structural engineer.

How can Hawkins Help?

Hawkins’ Built Environment team can review when something has gone wrong and assess the relevant specialism or party that might have contributed to the issue. Professional experience is important in engineering, including experience of investigation.

About the Author

Jolyon Antill is a Chartered Civil Engineer based in our Reigate office. Graduating with a first-class Master’s Degree in Civil and Structural Engineering, Jolyon has 27 years of design consultancy experience.

His range of industrial and commercial project design work includes new builds, renovations, and structural surveys, both in the UK and overseas. Jolyon also has extensive experience in regional civil and structural engineering consultancies working on educational, residential, leisure and commercial projects. If you have a civil or structural issue and need Jolyon or one of the team to investigate, please contact us.

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Bye Bye Bamboo: Why Hong Kong is Phasing Out Traditional Scaffolding

Matthew Carrington — Mon, 24 Nov 2025 10:56:48 +0000

Bamboo scaffolding, alongside neon signs and red taxis, has long been a defining feature of Hong Kong’s urban landscape. But like many cultural icons, it is now facing a quiet retreat. In a move driven by safety concerns, The Government of Hong Kong is beginning to phase out bamboo scaffolding in public construction projects, marking a significant shift in the city’s construction practices.

A Policy Pivot Toward Metal

On the 17 March 2025, the Development Bureau of Hong Kong issued a circular memo titled “Adopting of Metal Scaffolds in Public Works”. This document outlines a new requirement that from 21 March 2025, all public works tenders must specify the use of metal scaffolding. Bamboo may only be used in exceptional cases, and only with detailed justification.

The Bureau cited bamboo’s “intrinsic weaknesses,” including inconsistent mechanical properties, susceptibility to deterioration, and high combustibility, as key reasons for the change. Additionally, the Bureau is cognisant of the wide adoption of metal scaffolding in Mainland China and other advanced economies.

The Case for Bamboo

Despite its drawbacks, Hong Kong has historically favoured bamboo scaffolding for several compelling reasons. It is:

These advantages have contributed to bamboo scaffolding becoming a staple of the city’s construction industry for decades. However, safety concerns have persisted.

Putlogs: A Common Source of Failure

A 2004 study by Tsinghua University titled “Comparative Study of Safety and Application of Bamboo and Metal Scaffolding in Hong Kong”^[1]found that the most significant hazard in both systems was the failure or absence of putlogs – horizontal members that tie scaffolding to the building structure. An excerpt from the paper showing the hazards associated with both types of scaffolding can be seen below.

Interestingly, Hong Kong’s safety codes impose stricter requirements on bamboo scaffolding putlogs than on metal ones. Bamboo scaffolds (under 100m in height from ground) must have putlog ties spaced no more than 3 meters horizontally and 6.3 meters vertically (equivalent to one per 18.9m²), with each tie capable of withstanding 7kN^[2]. In contrast, metal scaffolds require only one tie per 25m², with a lower strength threshold of 6.25kN^[3].

This raises a critical question: if bamboo scaffolding is held to higher standards with regards to putlogs, why is it perceived as less safe?

The Real Risk: Lack of Oversight

A recent scaffolding collapse involving 20 workers revealed the true issue: inadequate professional oversight. Investigators found that the metal ties used for the bamboo putlogs were as thin as 1.06mm – far below the required 6.00mm^[4]. The collapse was not due to the use of bamboo itself, but to unauthorised modifications and a lack of professional design and supervision. A government safety officer emphasised the need for scaffolding to be professionally designed and approved. The Chairman of the Construction Industry Council echoed this, calling for better coordination among engineers, supervisors, and qualified personnel to prevent such failures^[4].

Looking Ahead: A Role for Expertise

While the shift to metal scaffolding may reduce some material-related risks, it does not reduce the need for professional oversight. Whether bamboo or metal, scaffolding systems must be properly designed, installed, and maintained.

The phasing out of bamboo scaffolding in public works marks the end of an era in Hong Kong’s construction history. Although the decision is rooted in legitimate material safety concerns, it also reflects a broader shift toward modernisation and regulatory rigour. As this transition unfolds, it is essential to recognise that safety is not solely a matter of materials and regulations – it is also a matter of professional expertise.

How can Hawkins Help?

At Hawkins, our chartered civil and structural engineers bring deep industry experience in design consultancy, site supervision, and forensic investigation. We offer guidance to the construction industry, helping define and develop working procedures and practices that reduce the risk of incidents and lead to safer outcomes. Our Hong Kong team has investigated a wide range of incidents, including, crane and material hoist collapses, concrete spalling, slope failures, and structural damage from vehicle collisions. Our goal is to provide clarity, accountability, and actionable insights that help prevent future incidences.

About the Author

Patrick is a Chartered Structural Engineer based in our Hong Kong office. He has many years of experience in the construction industry and has worked for both contractors and consultants on temporary and permanent structural works. He has designed temporary supporting structures for both metal and bamboo scaffolds. As a resident site engineer, he has also monitored scaffold construction safety and ensured that temporary working platforms are adequate to support all intended loads.

Patrick joined Hawkins as an associate in 2024 to expand the forensic structural engineering capabilities of Hawkins in the Greater China and Asia region.

If you would like to discuss any incident—whether related to the built environment or any of the many other scientific and engineering disciplines Hawkins supports its clients with worldwide, please get in touch.

References:

[1] Fang, DP, Wu, SH, Wong, KW & Shen, Q 2004, A comparative study on safety use of bamboo and metal scaffolding in Hong Kong. in Construction safety management systems. Spon Press, pp. 373-386.

[2] Hong Kong Labour Department 2024, Code of Practice for Bamboo Scaffolding Safety, Fifth Edition.

[3] Hong Kong Labour Department 2013, Code of Practice for Metal Scaffolding Safety, Second Edition.

[4] Hong Kong Construction Industry Council 13 February 2025, Life First Walk the Talk Webinar – Bamboo Scaffolding Safety and Code of Practice.

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Decorative Laminates

Chloe Duggan — Thu, 15 Aug 2024 10:46:36 +0000

Composites^[1], attractive because of their low weight and high strength, are common throughout the construction industry and are used for both structural and aesthetic purposes. Laminates are a type of composite, manufactured from multiple layers of materials that are stacked on top of each other and joined together using a combination of pressure, heat and adhesives. Laminates are commonly used for decorative purposes, such as floors, as well as door and furniture surfaces.

This article discusses some of the common problems that cause laminates and their underlying substrates to become ‘unbalanced’. This can not only be unsightly but can also cause the product to no longer fulfil its expected safety requirements.

Laminate Manufacture

Typical composites are made up of fibres, which provide mechanical strength, and a matrix, which transfers the load between the fibres. The resulting material has features of both the fibre and the matrix. Laminates are classified as a type of composite comprising sheets or panels (lamina) that have a preferred high-strength direction. These layers are stacked and glued together such that the orientation of the high-strength direction varies with each layer; these stacks are then adhered to a substrate, typically wood.

A schematic drawing of how these layers can be stacked. ^[2]

Decorative laminates are typically constructed from kraft papers impregnated with resin that adhere to the back of decorative paper. The fibres in the paper give the mechanical strength in tension and the material used to impregnate the paper is the matrix, providing the compressive strength when bent. It is important to note that the kraft papers used have a fibre orientation and can be laid to maximise the mechanical strength in a particular direction.

Each laminate has multiple layers of this paper which are then compressed and adhered to each other using either a high-pressure system or a continuous high-pressure system.

High-pressure laminates (HPL) consist of multiple layers of kraft paper which have been saturated in a phenolic resin. A decorative layer of paper saturated with a melamine resin is then applied on top. These are then compressed in a static press at pressures ≥ 50 bar and temperatures ≥ 120˚C to form the finished laminate. Laminates manufactured in this way are typically used for panels that are likely to be subjected to a high wear, such as work tops. BS EN 438, the standard for high-pressure decorative laminates, states that the minimum permitted thickness of the laminate is 0.8 mm ± 0.1 mm.

The process for manufacturing continuous high-pressure laminates (C-HPL) differs in that, whilst the pressures and temperatures used to make these laminates are similar to those used in HPL, the laminates are passed through a continuous roller, allowing for faster and more efficient manufacturing.

Unbalanced Laminates

As described above, the kraft paper used to manufacture laminates has a fibre orientation that will affect the mechanical properties of the laminate, as will the thickness of the laminate and how the laminates have been manufactured. One of the most common problems encountered when using laminates^[3]is warping, caused by unbalanced panel construction.

There are several factors that can cause a panel to become unbalanced. These include (but are not limited to):

The specification of the laminates used on each face – laminate manufacturers allow the customer to choose what laminates they want installed on their product. For example, a customer might want a door with one type of laminate installed on the inside face, and a different laminate on the outside. When materials with different properties are rigidly glued together, changes in moisture content across the panel can occur, which causes the materials to try and change shape (expand or contract). When this happens, stresses can accumulate. The panel will warp if the stresses on one side of the panel are significantly larger or smaller than on the other side of the panel i.e., the panel is unbalanced.
The orientation of the laminates used – where different fibre orientations are used.
Pre-conditioning of the laminate – this is carried out before bonding of the lamina and substrate and involves storing all materials used at a controlled temperature and humidity. This minimises the differential movement caused by changes in temperature and humidity.
Conditioning of the laminate – the fully constructed laminates are typically stored in the environment in which they are to be installed in for several days to allow them to acclimatise to the environment.

Another key factor to consider is the end environment in which the laminates are to be installed; large variations in temperature or relative humidity can cause the product to warp or distort after it has been installed.

Warping, whether caused by unbalanced construction, inadequately conditioned materials or the end environment is of particular importance when the product is required to conform to a specific standard or is safety critical, for example, the use of laminates in the manufacturing of fire doors, which are required to have maximum gaps between the door and the frame to allow for the proper operation of the smoke seals.

About the Author

Christabel is a Materials Engineer with extensive experience in the failures of polymers, metals, glass, composites, escapes of water and oil, mechanical system failures and personal injury claims.

She has written several CPR-compliant court reports and regularly presents at industry awareness days. She is well-versed in the testing and characterisation of conceptual and current materials and has experience in failure analysis of electrical components.

Hawkins has the technical knowledge and experience to tell you why a materials failure occurred, not just what caused it. Our services range from a free consultation through to a full investigation including a court-compliant report for the support of legal action. If you would like to discuss how we can assist you, please fill out our enquiry form or call us for a free consultation.

References

[1] Comprising of two or more materials with different physical and/or chemical properties.

[2] Source: https://www.researchgate.net/figure/A-laminate-made-up-of-lamina-with-different-fiber-orientations_fig2_308721666.

[3] Bent or twisted out of shape.

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Investigating Railway Collisions

Chloe Duggan — Wed, 31 Jul 2024 12:14:13 +0000

Collisions and incidents involving trains, including rolling stock, light rail, and mass transit systems such as trams, result in damage to vehicles and personal injuries, with consequential effects on service delivery and lost revenue. Rail vehicles are also used in many industrial settings and amusement parks, and incidents can result in personal injuries, damage to property, and business interruption.

Rail vehicles by their very nature operate on tracks, and therefore the options for avoiding a collision are limited to braking to either slow down or come to a stop. For the most part, rail vehicles such as trains, operate in an environment where they are segregated from hazards such as vehicular traffic and pedestrians by design. Issues can however arise where different forms of traffic meet.

Pedestrians and Passengers

One of the main areas of risk for the passengers of trains and trams is at the platform to train interface. Hazards for passengers include falling from the platform onto the track (and then potentially being struck by an approaching train), falling between the platform and the train, and being trapped in the train doors. In the investigation of an incident at the platform to train interface, an assessment of the adequacy of measures to reduce the prevalence of such incidents is often undertaken.

That assessment can include measurement of the friction levels provided by the platform surface, and a review of the platform markings and tactile surfaces to denote edges. The quality of any lighting (both above and below the platform) should be considered and followed-up by a review of the relevant safety requirements and standards. Physical measures, such as barriers or additional platform doors to prevent passenger access trackside can also be assessed. In some instances, motion detection or CCTV algorithms can be used to detect objects or people on the track. However, many rail systems are legacy systems and do not utilise the latest technology; therefore, additional platform doors and motion detection systems are not universally adopted. Systems which could result in false detection events (for instance being accidentally triggered by debris or animals) could also result in service disruption, and therefore their adoption can be impractical. Consequently, many systems rely on observation by the driver or other rail staff via CCTV systems or mirrors to ensure that the train is safe to depart. The condition and coverage of those systems can also be reviewed as part of an investigation.

Trespassers, whether intentional or accidental, can also pose a direct risk to themselves and trains, and cause damage to infrastructure. Infrastructure elements, such as gates, barriers and fences, along with appropriate signage, can help to deter trespassers, and can be considered as part of an investigation.

Pedestrian and Vehicle Crossings

Incidents can also occur at railway crossings (for pedestrians or vehicles), and in mixed traffic areas in the case of trams. Many warning elements (signage, lights, barriers etc.) along with warning procedures and sight lines for all parties need to be considered. The requirements for crossings should be reviewed in the context of the design of the crossing facilities and guidance such as Principles for managing level crossing safety published by the Office of Rail and Road (ORR). Trams have additional physical safety features fitted to them which enable their use in mixed traffic areas.

At the time of an incident, all efforts must be made to secure the evidence that could be considered relevant as part of an investigation. Such information is often captured as part of a Police or Rail Accident Investigation Branch investigation. The Rail Accident Investigation Branch (RAIB) is a Government agency with a statutory role to investigate many railway incidents to find cause, but not apportion blame or establish liability. The RAIB investigate all incidents on the national rail network and metro systems (including the Underground), but its remit does not include those on private land (e.g. industrial rail systems, museums, and amusement parks). Information is often gathered as part of an internal investigation for public railway operators and is critical in incidents in the private domain where there is no RAIB involvement. This information includes, but is not limited to, witness statements, operational data, CCTV recordings from both station and trackside locations, and other premises that could overlook the incident. CCTV is often critical, as it shows the movements of individuals and rolling stock, along with providing a timeline of events. If sufficient details are provided, train speed, vehicles and pedestrians can be calculated depending upon the quality of the recordings available. On-vehicle CCTV systems can provide further information showing the relative location of people and their actions, and if sufficient coverage is provided, potentially a driver’s responses. Datalogging systems related to the rail vehicle can provide speed, deceleration and positioning of a train (or trains) prior to, during and after an incident.

Derailments

Derailments can also result from material failures to both the vehicle and the track through fatigue, damage, overloading, and inappropriate maintenance. Hawkins have metallurgists and material scientists who can investigate failures to determine the root cause and the sequence of events for such incidents.

Collisions

When reconstructing a collision involving a train or tram, avoidance aspects (by the drivers involved) must be considered, although as highlighted above, the avoidance measures for rail vehicles are limited to braking, in contrast to a car where steering could also be used to avoid a collision. The driver’s view from the cab, which is often limited by the geometry of the windows, can be assessed along with any exterior lighting. Such an examination will usually require access to the train in a suitable area, where measurements of the field of view from the driver’s position and exterior lighting of the vehicle can be obtained. Where possible, an assessment of the scene is helpful, although it is often not practical to assess the scene ‘on foot’, depending on the management of access trackside and the incident location. Under such circumstances, a ‘drive through’ of the scene on an exemplar train fitted with video recording equipment can be used to obtain an appreciation of the scene. Other measurements can often be obtained by personnel working during engineering hours. The driver’s likely Perception Response Time (PRT) range can be determined according to published research, similarly to studies on car drivers, although there are some specific nuances regarding a rail environment. Such aspects can include levels of automation to the vehicle in question, which based on published research, can alter the likely PRT range. The field of view and lighting conditions, as well as the nature of the environment (i.e. if the incident occurred in an area where such a hazard might be expected) can also have a bearing on the likelihood of a driver detecting a hazard, and their associated PRT.

The braking response of the train can also be calculated when determining the overall braking distance. That can include the ‘rise time’ of the braking system, and the likely deceleration achieved by the train (often a minimum level specified in the train design). Such information can often be obtained from the equipment manufacturer, although information from testing during routine maintenance, can also be useful. It should be noted that the deceleration levels achieved by rolling stock is seldom as high as those achieved by cars and lorries. That is in part due the levels of friction available at the wheel to rail interface, and therefore ambient conditions (weather, leaves etc.) can have a significant effect on the deceleration levels that can be generated. Guidance, such as Network Rail standard NR/L2/OPS/045-4.07 National Operating Procedure, Section 07 Railhead contamination levels, exists for locations at a high-risk of rail head contamination and low adhesion conditions (such as areas prone to heavy leaf-fall or ice). The Network Rail operations standard NR/L3/OPS/021/01 Autumn Management also outlines how Network Rail and train operators prepare, manage and respond to the risks arising from autumn weather. However, each route will be subject to a specific process depending upon the risks that are present locally; that process, and conformity to it, can also be reviewed as part of an investigation. However, it must also be considered that high levels of deceleration could also lead to injuries to unrestrained and standing passengers.

Many trains include a data logging system, which can provide an insight into an incident including the speed of the train on the approach to and during a collision. Deceleration rates and the response of the driver can often be calculated from any data recorded on the train. The operation of automation systems for control and signalling could be reviewed and, where available, compared against any recorded data to determine if it has operated as designed.

Damage to a train and another vehicle (for instance a car) can also be assessed to confirm if the damage to the vehicles is consistent with the reported circumstances of the incident. If sufficient information is available, the scope of any likely repairs can also be determined when considering quantum in such cases.

About the Author

James is a Chartered Mechanical Engineer and has led a wide range of investigations relating to collisions and personal injuries involving vehicles and machinery. James specialises in incidents involving large goods vehicles, agricultural equipment and rail vehicles. Many of these investigations have required a review of appropriate health and safety procedures and guidance. James has also produced reconstruction reports for vehicle collisions. He is experienced in analysing CCTV footage and has conducted numerous scene surveys and vehicle examinations. He has also given evidence as an expert witness in Court proceedings.

Hawkins has investigated a number of rail incidents, including notable incidents such as the Potters Bar derailment in 2002, as well as incidents where the RAIB has not been involved (such as amusement park incidents and other related industrial failures). If you have a rail related incident and would like to speak to James or another member of our team, contact us for a free initial consultation.

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Leveraging Artificial Intelligence and Machine Learning in Digital Forensic Investigations

Chloe Duggan — Mon, 29 Apr 2024 12:02:35 +0000

In the ever-evolving landscape of digital forensics, the integration of artificial intelligence (AI) and machine learning (ML) stands out as a game-changer. These advanced technologies are transforming the way digital forensic investigators analyse and extract insights from vast amounts of digital data, making the investigative process more efficient, accurate, and proactive.

Improved Investigation Efficiency

Automation of Routine Tasks

One of the primary advantages of AI and ML in Digital forensics lies in automating routine tasks. Investigators often face the daunting challenge of sifting through vast datasets to identify relevant information. AI algorithms can be trained to recognise patterns, anomalies, and correlations within these datasets, significantly reducing the time and effort required for initial data analysis. Routine tasks such as data categorisation, keyword identification, and timeline reconstruction can be streamlined, allowing investigators to focus on the more complex aspects of a case.

Advanced Data Analysis

AI and ML algorithms excel at processing and analysing diverse forms of data, including text, images, and multimedia. This capability proves invaluable in cases where a multitude of digital artefacts must be examined. From emails and chat logs to image and video files, AI-driven tools can identify connections and uncover hidden patterns that can assist human investigators to efficiently analyse and interpret the evidence. This advanced data analysis contributes to a more comprehensive understanding of the digital landscape under investigation.

Enhanced Digital Evidence Recognition

Pattern Recognition

AI and ML excel in pattern recognition, a critical component of digital forensics. These technologies can be trained to identify specific patterns associated with malicious activities, such as cyberattacks or data breaches. By recognising patterns in network traffic, system logs, or file structures, investigators can swiftly detect and respond to potential threats. This proactive approach enhances the overall cybersecurity posture and reduces the risk of digital crimes being successful.

Behavioural Analysis

ML algorithms can analyse user behaviour and identify deviations from normal patterns. This is particularly relevant in cases involving insider threats or unauthorised access. By establishing baselines for user behaviour, AI-driven tools can flag suspicious activities, enabling investigators to intervene before a situation escalates. Behavioural analysis adds a layer of preventative measures to the digital forensic toolkit.

Overcoming Encryption Challenges

Decryption Assistance

As encryption becomes more prevalent in digital communications, investigators face challenges in accessing the encrypted data that is crucial to their cases. AI and ML can aid in developing advanced decryption techniques, assisting investigators in overcoming encryption barriers. By analysing patterns in encrypted data and leveraging ML to predict potential decryption keys, these technologies offer a valuable resource in accessing crucial information lawfully.

Encrypted Communications Analysis

AI-driven linguistic analysis can be employed to scrutinise encrypted communications for suspicious content. Even when the content itself remains hidden, patterns in language, syntax, or metadata can provide valuable insights. This level of analysis enhances the ability to uncover illicit activities while respecting privacy concerns and legal boundaries.

Conclusion

As AI and ML continue to evolve, so does their impact on digital forensics, both from a perpetrator and investigator stance. The future promises even more sophisticated tools that adapt to the dynamic nature of cyber threats. Increased collaboration between cybersecurity experts, data scientists, and digital forensic investigators will be crucial in harnessing the full potential of these technologies.

In conclusion, the integration of AI and ML into Digital forensics represents a paradigm shift in investigative methodologies. From automating routine tasks to enhancing data analysis and overcoming encryption challenges, these technologies empower investigators to navigate the complexities of the digital landscape with unprecedented efficiency and accuracy. As we venture into the future, the alliance between human expertise and AI will undoubtedly redefine the boundaries of what is achievable in the realm of digital forensics.

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Leaking Pipes & Cylinders: Common Themes Between Industry & Airing Cupboard

Chloe Duggan — Mon, 29 Apr 2024 09:14:17 +0000

We rely on our infrastructure to provide us with hot water, gas, and oil. Often, we are only aware of how important these services are to us when we notice a problem such as a leak. This can be just as difficult for a homeowner dealing with water streaming through their kitchen ceiling, or a refinery finding steam piping leaks. When the leak involves flammable hydrocarbons, gas or oil the risk of fire and explosion makes the potential for damage and casualties much worse.

At both ends of the spectrum of leaking pipes and cylinders, it is often the joints where the investigator will seek and find the leak location. This does not always mean that the joints themselves are faulty (although this may be the case). In this article, I will reflect on some of the common themes that can lead to leaks and failures; from high integrity industrial sites to the pipework in your home airing cupboard. These fall into three categories: materials and methods, installation skill, and service conditions.

Materials and Methods

The materials that can be welded for high integrity pressure and piping applications range widely across low alloy steels, stainless steels, aluminium alloys, nickel-based alloys, and more. Pipes and fittings used for the UK domestic water supply must comply with the Water Regulations. Either copper or plastic pipe (polybutylene (PB) or polyethylene (PE-X)) are the main options for domestic water pipework, with fittings made from copper, brass, or plastic. However, common to both sectors is that the materials and fittings should conform to British, or equivalent, standards.

The materials properties and composition range for engineering materials are specified to a standard, for instance, British Standard BS EN 10025[1] for structural steel, or American Petroleum Institute specification 5L[2] for pipeline steel. Products are supplied with mill certificates, giving chemical analysis and tensile properties for the batch of material. In welded fabrications, the weld consumables (wire, rods, flux, and gases) also have their own certificates and standards. Copper pipe for plumbing is specified to BS EN 1057[3], while plastic pipes are given in BS 7291[4] part 1 for PE-X or part 2 for PB. Plumbing fittings are included in the relevant parts of BS EN 1254[5], which deal separately for fittings for soldered joints, threaded fittings, compression, push-fit, or press-fit fittings.

With materials specifications generally having a robust quality system, this leaves the method for making the pipe joints, open to the greatest scope for error.

In industrial welding, the weld procedure specification, or WPS, is the ‘recipe’ to produce the weld. This lists the type of joint and alloy to be welded, the arc welding process including its current and voltage, and the welding filler metal that will make the joint. The method is qualified by making a test weld using the procedure, which is then subjected to a full program of destructive and non-destructive testing (NDT) to show that a satisfactory quality weld can be made.

All the welding records, material certificates, and test results certificates form the bundle of paperwork known as the weld procedure qualification record, or WPQR. This approach for ensuring weld quality is common across industries, whether it is a nuclear pressure vessel or a bridge that is being made. Any combination of material to be welded and the welding procedure can be qualified using this approach, following the methods provided in standards such as ISO 15614[6] or ASME BPV Part IX[7]. When performing an investigation into a failure involving any welded structure, a review of the WPS and WPQRs, as well as the welding and inspection records, will often be an important part of the work.

There is no equivalent approach in domestic plumbing installation, where methods have been developed for improving the speed of installation, or to reduce the amount of ‘hot work’ for fire safety. As an alternative to soldering, pressed joints made using a hydraulic tool can provide mechanical joint strength and leak tightness in copper pipes. Manual methods using compression joints and push-fit joints are also widely used and are considered relatively easy to fit. The method used in plumbing therefore is driven by the fitting type and the particular installation instructions for that fitting.

When materials and methods contribute to the cause of a failure, it is often due to a damaged or faulty component or fitting. Sometimes, a fabrication method has been used that is incompatible with the pipe material or fitting, or the fitting was damaged during installation. Less common, but not unheard of, is when rogue materials (with fraudulent paperwork or documentation) have been used in good faith, but are not fit for service. Sometimes the selection of material is inappropriate for the given service, causing corrosion issues later in service (for example), while the material used is the major contributing factor.

Installation Skill

The method for installing pipework is only as good as the skill of the person who does it. In both welding and plumbing, there are established ways that a technician can learn their skill and demonstrate their competency., such as on-the-job training and certification.

Welders are qualified on specific weld procedures and codes based on the quality of a test weld they have made, and they are usually qualified to ASME BPV Part IX or ISO 9606[8]. The qualification is based on the skill of the welder, rather than the mechanical properties of the weld (which are determined by the weld procedure parameters). The welder qualification usually also allows them to weld joints that are considered ‘easier’ than the one used for the test weld. This allows for a wider range of welds to be made from each welder qualification. An example would be a welder qualified on a single-sided joint could also weld double-sided, or a pipe welder could also weld plate.

Alternatively, using mechanised or automated welding processes can reduce the number of parameters under the welder’s control and can ensure more consistent quality welds. A welder’s skill is continually assessed since their welds are subject to NDT so that defects can be cut out and repaired. Welders with high repair rates can be identified and given further training.

A plumber who consistently makes poor joints would not necessarily be identified so directly. Teams of plumbers in industrial fit-out or new-build sites can work in a similar manner to welders. However, in domestic settings, plumbing is perhaps more susceptible to installer error, since the plumber could be working on their own, without an independent pair of eyes to pick up on accidental oversights or check the finished work . Plumbing fittings and methods are developed to be ‘easy to install’, but this means that push-fit joints and compression joints that appear to be well-fitted, might not be, if the push-fitting is missing an O-ring, or the pipe is not pushed into the fitting far enough. Compression joints need to be tightened enough to deform the olive on the pipe to make the seal mechanically strong and watertight, but this cannot be determined just by looking at the joint.

The main way to confirm the effectiveness of the plumber’s joint is by pressure testing it (although ultrasonic test methods exist that can be used on press-fit joints).

Once a plumber learns the basic skills from qualifications and on-the-job training, certification schemes are available to support professional development and competence, such as the Construction Skills Certification Scheme (CSCS), the Association of Plumbing and Heating Contractors (APHC), or the Water Regulations Approval Scheme (WRAS). When investigating a failure that might be due to an installation error, it is prudent to ask for evidence of the installer’s qualification(s) and certification. Although mistakes can happen, installers should have the appropriate skills and knowledge to understand how best to avoid them.

Service Conditions

Even the best materials and installation are at the mercy of the conditions the pipework and equipment will experience in service, in terms of temperature, stresses, and chemical environment.

For welded steel structures, the main concerns are avoiding brittle fracture at low temperatures, preventing fatigue cracking when in service under variable or cyclic loads, and preventing atmospheric corrosion (rust). Welds can also be susceptible to stress-driven environmental cracking such as stress corrosion cracking (SCC) because the intrinsic residual stresses at the weld joint can be sufficient to drive cracks in susceptible combinations of materials and chemical environments. There are many potential in-service damage mechanisms for industrial piping. However, both industry and domestic plumbing can suffer SCC of austenitic stainless steel when exposed to chloride (i.e. salt). In your home, this is more likely to be found in the bathroom as it affects the woven metal in flexible hose connectors. The outer layer is made from woven stainless-steel wire and provides the mechanical strength to support the rubber inner tube containing the water. But exposure to certain cleaning products or bathroom chemicals, or where the metal does not have enough alloying in the steel to be sufficiently resistance, the wires can corrode and the fibres crack. This will be seen as rusting and fraying of the weave, allowing a hole to open for the inner tube to burst.

Fatigue is a major issue for welded structures in service, particularly under vibrations, or rotating equipment, as cyclic loads incrementally propagate cracks from stress concentration locations – often weld toes. The magnitude of stress cycles can be low, but can still grow a crack over time, causing the structure to ultimately fail from a secondary failure mode. This is often a ductile overload of the remaining thinned ligament. Fatigue in plumbing fittings is rarer, as they do not usually experience thousands of loading cycles, but can occur in installations where pipework is under high constraint or bending loads. Fatigue cracks in plumbing will initiate from stress concentrations intrinsic to the fitting, such as the threads in compression fittings.

Low temperature in service is a concern for both industrial components and in plumbing, but for different reasons. Ferritic steels undergo a transition from ductile to brittle behaviour as the temperature drops, increasing the risk that they could fail in a catastrophic brittle manner. In domestic settings, low temperatures are more likely to cause pipes to freeze if they are not well insulated. When the water inside a pipe freezes, it causes localised blockages in the pipe, and the water trapped in between these ice plugs experiences an increase in pressure due to the expansion in volume of the freezing ice. The resultant pressure increase can cause copper pipe to burst, or pipe fittings to separate. Upon thawing, the subsequent escape of water can cause significant property damage.

Summary

For cases involving leaking pipework or fluid-containing cylinders, the common themes in the ways they fail can help steer the forensic investigation and ensure all appropriate evidence is gathered. Examination and analysis of the broken component will provide a materials engineer with plenty of information. Their hypothesis must consider whether the damage relates to the materials that have been used, the fabrication methods and the skill of the fabricator, or the conditions experienced in service. The forensic investigator will then be able to seek specifications, documents, records, certificates, or request testing, that can help determine the ultimate cause of leaking pipes and cylinders.

About the Author

Materials expert Dr Philippa Moore joined Hawkins in 2022 and is based in our Cambridge office, where she specialises in materials failures, escape of water and oil, and mechanical and engineering failures. Philippa graduated from the University of Cambridge with MA and MSci degrees in materials science and metallurgy. She then spent 18 years working at TWI Ltd, and developed an international reputation in fracture toughness testing, and engineering failure investigation, often of welded steel structures, through her project work and consultancy. With extensive experience in forensic investigations, Philippa has published over 45 conference and journal papers on her academic research, and on topics supporting her involvement on British and International standards committees for fracture testing.

References

[1] BS EN 10025-2:2019 “Hot rolled products of structural steels – Technical delivery conditions for non-alloy structural steels”, 2019.

[2] API Specification 5L, 46th Edition, “Line Pipe”, American Petroleum Institute, 2018.

[3] BS EN 1057:2006+A1:2010, “Copper and copper alloys. Seamless, round copper tubes for water and gas in sanitary and heating applications”, 2010.

[4] BS 7291-1, 2010 Edition, November 10, 2020 – Thermoplastics pipe and fitting systems for hot and cold water for domestic purposes and heating installations in buildings Part 1: General requirements.

[5] BS EN 1254, “Copper and copper alloys. Plumbing fittings” twenty part standard, 2021.

[6] ISO 15614-1:2017 “Specification and qualification of welding procedures for metallic materials — Welding procedure test — Part 1: Arc and gas welding of steels and arc welding of nickel and nickel alloys”.

[7] ASME BPVC-IX 2023 American Society of Mechanical Engineers, Boiler and Pressure Vessel Code, Section IX: Welding, Brazing, and Fusing Qualifications.

[8] ISO 9606-1:2012, “Qualification testing of welders — Fusion welding — Part 1: Steels”.

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Concrete – Hard Lessons

Chloe Duggan — Fri, 22 Mar 2024 17:34:01 +0000

Reinforced concrete is one of the world’s most widely used building materials. It is a composite material of concrete, which works well in compression, with metal bars, fibres or mesh embedded to provide tensile strength. Recent failures of structures containing Reinforced Autoclaved Aerated Concrete (RAAC) in the UK have garnered widespread attention. However, RAAC is just one form of concrete, and there are several other historical issues affecting existing concrete buildings. In this article, Jamie Paterson discusses how these issues affect the durability and life-expectancy of reinforced concrete buildings.

Reinforced concrete has many unique characteristics compared to other common structural materials. Most notably, the ability to readily alter its composition and form during design and construction.

Compositional changes can improve:

Strength
Curing time
Water resistance
Durability
Shrinkage
Buildability
Embodied carbon content

Additionally, concrete has no fixed form allowing it to take-on virtually any shape. While this adaptability is advantageous, it also generates complexities that do not exist in other building materials.

Designing for Durability

Despite its robust appearance, reinforced concrete is vulnerable to deterioration caused by external factors such as moisture, chemicals, and extreme temperatures. The primary defence against these elements involves encasing the steel reinforcement behind a surface layer of concrete, known as “cover”. This protective layer must have sufficient thickness and be composed of a suitable concrete mixture. In the absence of suitable cover, harmful chemicals and moisture can infiltrate leading to corrosion. Furthermore, a lack of cover during a fire, results in the heating of the steel reinforcement and rapid strength loss.

Cover requirement for fire (‘a’) and durability (‘c_nom’) based on BS EN 1992

Identifying the minimum cover and mix design is typically a simple prescriptive process. However, it is critically important to understand the specific environmental and functional conditions that the concrete will be exposed to. The designer needs to be diligent in understanding all conditions that could affect the concrete, not simply the moisture levels.

In the presence of moisture, steel reinforcement will begin to corrode. The formation of rust on the surface of the steel exerts pressure on the surrounding concrete causing cracking and eventually spalling of the surface concrete. This, in turn, exposes the steel reinforcement to further deterioration. The process of corrosion is accelerated by the presence of certain harmful chemicals. These can enter the concrete during construction, via contamination of its constituent materials, or while in service. Improved industry knowledge and modern quality control measures have reduced the prospect of harmful chemicals entering concrete during manufacture and construction. However, many buildings that exist in the UK were constructed several decades ago and already contain contaminants.

Historical Issues Affecting Concrete Durability

Cured concrete typically has an alkalinity of pH9 or greater, which provides passive protection to the embedded steel reinforcement. Over time, the alkalinity of cured concrete reduces, particularly at the surface, due to carbonation. The rate at which carbonation progresses through the depth of the concrete depends on several factors, but notably, a humid environment causes an increased rate of carbonation. In the event that carbonation depth exceeds the concrete cover, the reinforcement loses passive protection. Carbonation is likely to be more advanced in older structures simply due to age. Excessive carbonation is not an issue in dry conditions, but once moisture is present, corrosion can progress at an accelerated rate.

The carbonation depth is typically measured by spraying a phenolphthalein solution onto a freshly cut concrete surface. The solution turns pink in the presence of alkaline conditions (i.e. uncarbonated concrete). For certain concretes, phenolphthalein is ineffective and alternative pH indicators should be used.

The likelihood and rate of corrosion occurring, is also increased by the presence of chlorides. These can have a major influence on the long-term durability and integrity of concrete structures. Concrete can be exposed to chlorides via several pathways, primarily from external sources like deicing salts, salt water, and marine environments. Corrosion in the presence of chloride can be incredibly destructive and the primary means of mitigation is through design. When specifying the concrete composition, it is normally necessary to adopt concrete with a compressive strength of greater than 40N/mm². The maximum water content, cement ratio and suitability of additives should also be considered. In existing buildings, it is critically important that concrete containing or exposed to elevated levels of chlorides is kept dry. This is particularly important in historic buildings, where many traditional building materials contain salt from their original manufacture and transportation.

In the late 1940s, following the Second World War, it became increasingly common for the ground floors of buildings to be constructed using ground-bearing concrete slabs, as opposed to imported timber. Due to shortages of construction materials, the government encouraged the use of ‘hardcore’ below-ground-bearing slabs. At the time, hardcore consisted of crushed waste, which included contaminants and deleterious material. These materials often contained sulphate, which attacks chemical compounds that are abundant in the most common type of cement.

It was not until 1965 that the building regulations were updated to prohibit the use of hardcore containing water-soluble sulphates. This reduced the issue but failed to eliminate it completely. The ground on many brownfield sites is contaminated by material containing water-soluble sulphate. These materials can leach sulphate into the ground, creating higher risk conditions for below-ground concrete, such as foundations. Nowadays, sulphate-resistant cements can be specified in place of the more common Ordinary Portland Cement (OPC).

OPC is the most common cement type used in the production of concrete. Other types of cement, or cement substitutes, can be specified to achieve the required concrete characteristics. In the 1950s, High Alumina Cement (HAC) was used in the manufacture of precast concrete elements. It was then banned from use in the 1970s, following several high-profile collapses. Despite this, concrete containing HAC remains in thousands of buildings across the UK. The primary issues affecting HAC concrete are lack of cover, carbonation depth and a chemical process called conversion. Conversion occurs over time and is commonly accompanied by a significant reduction in strength. Investigations have found that the compressive strength of HAC concrete following conversion can be less than 50% of the initial strength.

HAC was typically used to manufacture precast I-beams or X-beams, but it has also been identified in some insitu concrete between 1950-1970. Reinforced Autoclaved Aerated Concrete (RAAC) is composed of two elements: Steel reinforcement (R) and Autoclaved Aerated Concrete (AAC). AAC has existed since the early 1920s and is commonly found in unreinforced blocks for constructing masonry walls. AAC is a precast form of concrete and has several positive characteristics for use in buildings. However, these characteristics are accompanied by low compressive strength and high permeability compared to other forms of concrete. Around 1950, reinforcement was combined with AAC to create precast elements with improved spanning capabilities for use in floors and walls.

There are several issues that affect RAAC including low stiffness and poor detailing of reinforcement, as well as the low strength and high permeability that comes with AAC The durability of RAAC is negatively impacted by the porosity of AAC, which facilitates the penetration of moisture and transportation of harmful chemicals to the embedded reinforcement, increasing the risk of corrosion occurring.

Prevention and Life-Extension

There is little that can be done to rectify reinforced concrete that has been constructed to unsuitable specifications or with poor detailing of reinforcement. However, by identifying potential defects it is possible to avoid conditions that might adversely affect the structure. The issues discussed above are inactive in dry conditions. It is critically important that concrete buildings, new and old, are regularly inspected to identify sources of moisture and changes to the prevailing conditions. Maintenance of the building envelope, supply water, drainage and ventilation systems can help reduce moisture levels and extend the life of concrete buildings. Examples of issues that may adversely affect concrete buildings include:

Leaking services
Damaged below-ground drainage
Water ingress
Storage of water or chemicals
Faulty rainwater goods
Increases in humidity
Change of use
Defective waterproofing

Since the characteristics of concrete, and the associated defects, are dependent on several factors, investigations of concrete structures should be undertaken by a competent structural engineer with suitable knowledge and experience of the type of building being inspected.

It is possible to protect concrete structures from deterioration via the introduction of surface coatings and renders or via cathodic protection. These methods are most suitable in scenarios where a concrete structure cannot be isolated from moisture or harmful chemicals. Typical examples include multi-storey car parks, where surface water and de-icing salts are present, or industrial buildings, where processes generate unfavourable conditions. It is fundamentally important that adequate preparatory work is completed to ensure that the remedial measures perform as intended. In the case of cathodic protection, the initial costs can be high, and the system is likely to require ongoing maintenance and inspection.

Summary

The construction industry, like many industries, has often progressed through trial and error. The recent collapses linked to RAAC are one such error that will still be fresh in everyone’s mind, but similar historical issues still affect thousands of buildings. The simplest way to mitigate these issues is through regular inspection and maintenance. Pre-emptive investigations can be conducted to pinpoint potential risk factors, aiding the development of suitable inspection procedures that are tailored to the risks present.

Hawkins’ Built Environment team can assist in the investigation of defects in building structures, whether in a pre or post loss scenario. Our structural and civil engineers can identify factors affecting life expectancy or investigate the cause of failures that have already occurred.

About the Author

Jamie Paterson is a chartered structural engineer (CEng) with the Institution of Structural Engineers (MIStructE) and has a broad range of skills covering onshore and offshore structures. He has undertaken detailed structural investigations of existing buildings, including listed buildings and monuments and has extensive experience of investigating and remediating existing buildings via destructive and non-destructive methods.

Jamie also has experience with modern design methods and low-energy buildings in the context of net zero. In 2022, Jamie became one of the first Passivhaus certified structural engineers in the UK.

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Beware the Repair

Chloe Duggan — Tue, 12 Mar 2024 11:26:09 +0000

Second-hand domestic appliances can appeal to the budget-conscious, environmentally-minded, or bargain lovers alike. Facebook Marketplace, Gumtree and eBay, all offer inexpensive used appliances; however, these appliances come with no guarantees and no certainty over the provenance of the appliance.

Having investigated numerous domestic appliance fires and examined countless tumble dryers, I was interested in what £10 would buy you in a second-hand domestic appliance. I decided upon the following appliance:

First and foremost, being aware of the 2015 Hotpoint/Indesit tumble dryer recall, I checked the appliance on their website and found it to be covered by the recall; this appliance was at an increased risk of fire. The guidance from Hotpoint is to unplug the dryer and not use it.

I did not know the history of the appliance, as the seller was the owner of a house clearance company and sold items of value from the clearances. I undertook an inspection and testing of the appliance in the Hawkins’ laboratory facilities. When I plugged it in and switched it on, the LCD screen flashed but did not remain illuminated. When I pressed ‘start,’ the drum rotated for a couple of seconds before ‘tripping’ the Residual Current Breaker with Over-Current (RCBO). An RCBO is a combined residual-current device (RCD) and circuit breaker for the sockets. I reset the RCBO and tested the appliance again, with the same result.

Taking the side panel off, it was apparent that some of the parts were not original, and that the tumble dryer had undergone a repair. It appeared that the heater element and associated supply cables had been replaced, but whoever did this had not replaced the cable ties securing the cables. The main power supply cables to the heater elements were not routed through the casing mounted cable tie but, were instead attached to this cable tie with a green twist tie. As a result, the cables were not routed correctly and were left resting against the rotating drum.

Due to the incorrect routing of the main power supply cable to the heater elements, the cable insulation had worn against the drum when the dryer was in use. Over time, this abrading of the cable insulation had exposed the live conductors, allowing them to arc against the drum. Several markings on the drum show that the cable had been arcing for some time before I purchased it, as each mark was evidence of a separate arcing event.

Whilst the fault has not manifested itself in a fire, the number of markings on the drum suggested that the circuit protection of the building where the appliance had been located was much less sensitive than an RCBO or RCD and was not sensitive enough to isolate the tumble dryer when the arcing occurred. This means that this wear could have, continued to a point at which an incendive failure occurred.

About the Author

Since joining Hawkins in 2016, Jon has investigated over 400 fire and explosion incidents. He has led investigations of a domestic, industrial and commercial nature, which have ranged in size from small losses to multi-million-pound complex claims.

Jon is experienced in the legal process in both Scotland and England & Wales, and the preparation of CPR Part 35 compliant reports. He has experience advising solicitors and Counsel and has given expert evidence in the All-Scotland Sheriff Personal Injury Court, a Fatal Accident Inquiry, and in the County Court of Northern Ireland.

Jon is also an A2 Certificate of Competence (A2CofC) certified drone pilot and can assist clients with aerial surveys on cases relating to fires, structural failures, and personal injuries. The use of drones in an investigation can be particularly beneficial to inspect dangerous or hard to reach areas. He is Regional Manager of our Glasgow and Belfast offices.

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Open Plan Office Acoustics (BS ISO 22955)

Chloe Duggan — Thu, 15 Feb 2024 17:12:17 +0000

Since before the start of the COVID-19 pandemic, the way typical offices are used has been changing. A move toward more collaborative and flexible working spaces has been growing, with private office space reducing. The pandemic accelerated this growth, as the increase in home working makes flexible office space more feasible and increases the likelihood that, when an office is in use, it is specifically for collaborative work. To keep up with this trend, an update in the standards relevant to the control of the acoustics of office spaces was also necessary. To that effect, BS ISO 22955:2021 “Acoustics – Acoustic quality of open office spaces” aims to give guidance in the design and construction of open office space for acoustics and its cognitive effects.

The standard categorises the open office spaces into different room-activity ‘types’:

Undecided (vacant floor plate);
Outside of the room communication;
Inter-workstation collaboration;
Small amounts of wider range collaboration;
Public reception;
Combinations of activities;

For each of these room activity types, the standard then details criteria based on the interactions and resulting acoustic challenges that occur. Criteria include maximum workstation noise levels, minimum special decay rates, maximum reverberation times, and maxima for the sound pressure level of speech at 4 metres from the source. It assumes that the typical open-plan office space is to be used as a flexible workspace, and therefore has requirements for both collaborative communication and ‘concentration’ options.

In addition to these quantitative measures for the recommended performance of the open office space, the standard also provides more qualitative guidance, such as how to arrange the space to optimise acoustic conditions. This includes details of where to locate coffee machines and breakout areas, private offices and meeting rooms, and circulation routes, with respect to the open plan space. In the case of private offices and small meeting rooms, the standard also provides a recommendation for the sound insulation between the spaces. An open-plan spaces ‘etiquette’ annex is included, that provides guidance on working practices that can improve acoustic working conditions, including avoiding talking while walking, not using telephone loudspeakers, and encouraging the use of instant messaging and private meetings for collaboration.

A description of how to treat spaces in order to meet these recommendations is included, briefly covering ceiling, wall, and floor treatment, in addition to the contribution from the furniture used in the spaces and considerations for accessibility and special needs.

Finally, an annex discussing sound masking systems, which are a widespread treatment solution for open plan offices, but are scarcely mentioned elsewhere in the standard, is provided. The annex discusses the argument around the use of such systems, their intended function, and concludes that “The use of masking sound should be considered in the context of the overall design, the occupants, and the activities undertaken”.

The standard is likely to prove a useful tool in the design and construction of open plan offices, with specific guidance based on recent research as to how to optimise such spaces for work. Considered design of open plan offices ensures that productivity is maximised and disturbance minimised. Without these design considerations, spaces can become excessively noisy and distracting, or in more extreme cases, be deemed unfit for purpose.

Works to alleviate issues can delay when spaces can be used, and incur costs. Whilst some concerns can be rectified fairly easily, in acoustically critical spaces, the solution may require complete demolition and reconstruction.

Further work is still required to fully understand the relationship between sound masking systems and open office spaces, and perhaps to better define the type of activities that can occur in an open office space and their relationship with each other.

About the Author

Jonathan is a Senior Acoustic Consultant based in our Cambridge Office following graduation from The University of Exeter with a Masters in Physics. He is part of the acoustics team at Hawkins, working with architects, manufacturers, facilities managers, and end-users to supply noise impact assessments, room acoustics assessments, noise at work assessments, design consultation, vibration measurement, and consultation for product development.

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Defining Spaces in Public Address and Voice Alarm System Design

Chloe Duggan — Tue, 06 Feb 2024 17:20:13 +0000

Public Address and Voice Alarm systems can be found in public buildings such as train stations, airport terminals, bus terminals, museums, and places of worship, to name but a few. They are also becoming more common in office buildings and other non-public buildings with high numbers of staff. While a Public Address System is used to convey general information or paging, they often double-up as a Voice Alarm System, used to convey emergency or safety information, such as “beware of unattended packages” or evacuation guidance in emergencies. Voice Alarm Systems must be designed and perform to the minimum requirements set out in British Standards. The most important of those requirements is the speech intelligibility; that is, how easily a message can be understood. After all, if you cannot understand what is being said, there is little benefit in having a Voice Alarm System.

Acoustically Distinguishable Space

Most buildings are divided into different areas or spaces, and the speech intelligibility is usually assessed for each space separately. ADS is the abbreviation for ‘Acoustically Distinguishable Space.’ Formerly ‘Acoustically Distinguishable Area’ (ADA), the name was changed in British Standard 5839-8:2023 to better distinguish it from the ‘area of coverage’. The difference being that the ‘area of coverage’ is a 2-dimensional audience area to be ‘covered’ by the Voice Alarm System (this may be a small area or a whole building), whereas an ADS is a 3-dimensional room or area covered by the Voice Alarm System.

The ADS is a space, inside or outside a building, characterised by its specific acoustic performance or physical characteristics. For example, a waiting area leading to a large atrium would likely be a separate ADS to the atrium, despite the absence of a wall separating the two spaces.

So, why is it important to properly separate areas into their ADSs? Let us consider a small train station with two platforms and a ticket hall. It is normal practice for each of these areas to be given a different ‘zone’, where a ‘zone’ is part of the area of coverage to which information can be given separately. If the platforms are at the surface (for example, not underground) then, in all likelihood, there will be both canopied and uncanopied areas on those platforms. A canopied area will typically be characterised by a greater number of acoustic reflections from the canopy and platform buildings. That is, it might sound ‘echoey’. However, an uncanopied area may be characterised by a higher ambient noise level as it is more exposed to environmental noise. They should, therefore, be treated as two separated ADSs even though they may be within one zone – the platform.

Why Does This Matter?

If, in our predictions or measurements, we take the canopied and uncanopied areas to be a single ADS (i.e., a single audience plane in our modelling software with the same noise for both areas), we will find that we have a large deviation in measured speech intelligibility in the two areas, and it will be dominated by the worse of the two areas. By taking the platform to be a single ADS, we might fail the entire zone (using our previous example, the entire platform), when, in fact, it may only be a specific ADS (the canopied or the uncanopied area) that needs our attention.

What about spaces of different physical characteristics? To highlight the importance of considering those physical differences, we will consider a double-height ticket hall with a high ceiling adjacent to an area of much lower ceiling height. It might be the case that the ambient noise level is the same throughout the entire zone. It also might be the case that, due to the application of acoustic absorption, the acoustic performance of both spaces is similar. We might predict the speech intelligibility for the zone and find we get much lower values in the area with the lower ceiling compared with those in the area with the higher ceiling. What is going on here? The difference lies in the proportion of sound reaching the listener that comes from the loudspeakers and that which comes from reflections.

The matter of correctly identifying ADSs might seem trivial, however, incorrectly defining them could mean that an area that should pass the intelligibility requirements might appear to fail, resulting in the installation of unnecessary acoustic treatment or other costly remedial action to be taken. In the worst case, an area might pass when it should fail, resulting in an unsafe life safety system.

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