11
Mon, Nov
0 New Articles

Top Articles

A University of Manchester academic has become a leading expert of rap music in UK criminal cases.

Dr Eithne Quinn (above) a University of Manchester academic is a leading expert of rap lyrics in UK murder cases.

Practical Considerations by Michael Berrigan, Associate Director, Dubai, HKA INTRODUCTION Most standard form construction contracts contain provisions under which the employer can terminate the contractor’s employment for default. Default of the contractor can arise for several reasons. The events that entitle the employer to terminate should be clearly set out within the contract. Notwithstanding the reasons for termination, quantifying the financial effects and the monies due to, or from, a party can be problematic, which may lead to disputes and the expenditure of additional monies to expedite recovery.1 The purpose of this article is to identify some of the basic principles to consider when quantifying the effects of termination, either as the engineer, the parties to a contract or as a third party (collectively hereinafter referred to as the “Assessor”). Reference is made to the termination provisions of the FIDIC Red Book 2017 (“Red Book”),2 however this article intends to identify principles that can be adopted generally. TERMINATION FOR CONTRACTOR DEFAULT (Sub Clause 15.2) Following termination of the contractor’s employ- ment for default, the employer has a contractual remedy to complete the works and/ or arrange oth- ers to do so. The employer may use any goods (which may include the contractor’s equipment, materials, plant and temporary works) and the contractor’s documents to complete the works. The contractor is required to comply with any reasonable instruction from the employer, for the assignment of any sub- contract; and for the protection of life or property, for the safety of the works. Any employer supplied materials and/or equipment should be made avail- able to the employer, if provided to the contractor. The employer may suspend payment until any ad- ditional costs, losses or damages that flow from the termination, are ascertained. VALUATION AFTER TERMINATION (Sub Clause 15.3) It is of upmost importance that a valuation of the works is carried out at the date of termination (“DOT”). The valuation shall form the basis of calculating any monies owed to, or from, the contractor and will inevitably form the basis of determining the balance scope of works to be completed. Sub-Clause 15.3 prima facie appears to be self- explanatory in this respect, however in practical terms it raises a few commercial considerations for the Assessor: ”the Engineer under Sub-Clause 3.7…shall proceed to agree or determine the value of the Permanent Works, Goods and Contractor’s Documents and other sums due to the Contractor for work executed in accordance with the Contract…”. Sub-Clause 3.7 encourages the parties to consult in order to agree the valuation. As part of the consultation process, the parties may jointly or independently employ the expertise of quantity surveyors3 to undertake or assist in preparing the valuation. If the parties are unable to agree the valuation, the engineer must issue a determination within the prescribed time limits. Undertaking the valuation It is important to recognise that the valuation is to be a gross valuation in accordance with the terms of the contract. The valuation may be calculated as the ag-gregate of items ‘a)’ to ‘c)’ below, less the actual monies paid to the contractor, including a provision for any outstanding monies to be recovered for advance payments as follows: a) Permanent Works and Variations; b) plus, Materials/Plant on site or delivered to the engineer; c) plus, Claims; and d) less, monies paid to the contractor and any balance of advance payment(s) owing to the employer. The process of preparing a valuation of the Permanent Works and Variations, should be one based on factual evidence, as far as reasonably possible. It is essential that the Assessor and/or the parties visit the site as soon as the termination becomes effective, in order to sufficiently record the as-built status of the works4. Valuation can be more difficult under lump sum contracts, typically when elements of the works are partially complete and the contract does not include a mechanism for valuation, for example, the absence of a schedule of rates or a bill of quantities.5 Some standard form contracts contain provisions which allow for a valuation to be based on a reasonable amount. Consideration may need to be given to the valuation of Permanent Works that are considered defective. The Red Book states that the valuation “shall not include the value of any Permanent Works to the extent that they do not comply with the Contract.”6 In practice however, if it is the employer’s intention to suspend payment to the contractor until any additional costs are ascertained, it may be practical to include the full value of the Permanent Works and set-off any costs for remedying defects once established.7 The valuation of Preliminaries may be more subjective. Consideration should be given to the valuation of fixed lump sum items.8 For example, it may be that the contract price includes a lump sum for design. The Assessor may need to review the scope of the contractor’s design and make a valuation, taking into consideration the progress of the design and the production of deliverables at the DOT. A simple pro- rata of the allowance(s) contained within the contract price may not generate an accurate valuation. Further consideration may also need to be given in in- stances where the contractor has caused critical delay to the project. It may be necessary to abate the valuation of preliminaries to reflect the same period of delay caused by the contractor. The valuation should also recognise the value of any Materials and/or Plant intended to form part of the works, either on or off site. There are several legal issues to consider in this context such as ownership, possession and retention of title. The first step is always to check the terms of the contract. Most con- tracts provide that title passes when (i) they are delivered to site; or (ii) when the value of goods have been included within an interim payment. Under the provisions of the Red Book, the contractor must de- liver to the engineer, any materials and/or plant required by the employer at the DOT. These may be goods ordered, but not yet delivered to the site. It may require a reasonable period to pass to allow for such items to be delivered to the engineer. Nevertheless, the valuation should include all the items in the possession of the engineer and on site. The con- tract may identify the value for each item, in the absence of this, it is unclear how the Assessor is to value the goods. One approach may be to value the goods on a cost-plus basis, inclusive of all reasonably incurred costs such as mobilisation. The contractor should present satisfactory records for such goods, including purchase orders, receipts, proof of ship- ping costs etc.9 The value of all Claims determined by the engineer up to the DOT, should also be included within the gross valuation. Deducted from the gross valuation should be the monies already paid to the contractor and the amount, if any, not yet recovered from any advance payment made by the employer to the contractor. The calculation will determine the amount owed to or from the contractor under Sub-Clause 15.3. PAYMENT AFTER TERMINATION (Sub Clause 15.4) The employer may withhold the payment of any monies owed to the contractor as agreed or deter- mined under Sub-Clause 15.3, until all the costs,losses or damages, associated with the completion of the works have been established. The employer may be entitled to set-off the following from the monies owed to the contractor: 1) Additional costs of executing the works; 2) Other costs reasonably incurred including the employer’s losses and/or damages; and 3) Delay damages. Additional costs of executing the works After termination of the contractor (“Contractor A”), the employer may choose to appoint a replacement contractor (“Contractor B”), to complete the works. Ideally, the tender for the completion works should be competitive, inclusive of free issue material and/or plant left on site or in the possession of the engineer at the DOT. Provisions may also be made for the use of Contractor A’s equipment and/or temporary works if retained by the employer. It is important to remember that the employer is only entitled to recover the extra over costs of completing the works. When re-tendering the completion works, it is highly unlikely that the final scope of the works can be determined, and inevitably there may be further variations to be issued up to completion. To calculate the extra over costs, it is important that the Assessor recognises that the final account for Contractor A is still ongoing and should be com- pared to the final account of Contractor B for the same works at completion. For example, under the terms of the Red Book, the contract price may be subject to adjustments, including changes to items and/or quantities.10 The Assessor should prepare a final account for both contractor’s up to the completion of the works, referred to by the RICS as a notional final account.11 Any additional costs incurred as a result of completing the works with Contractor B can be set-off from any monies due to Contractor A under Sub-Clause 15.3. Difficulties may arise when valuing variations for works that are dissimilar to the works contained within Contractor A’s contract. In such instances, it may be reasonable to value the varied works taking into account all of the information contained within Contractor A’s contract, as far as reasonably possible, for example, labour constants, labour rates, rates for overheads and profit etc. and apply that information to current market rates and prices for the varied works. All other costs reasonably incurred and the employer’s losses & damages Most certainly the employer will incur further costs, losses and damages in connection with the completion of the works. A general list of items that the employer may be entitled to set-off from Contractor A are set out below: 1) The cost of making good defects to Contractor A’s works – The completion contract should distinguish between the completion works and making good of defects. If the full value of the defects is to be claimed in the employer’s set-off, then the valuation for Contractor A at termination must include the full value of the same items of work, as if they were in accordance with the contract. 2) Interim costs such as making the site safe, additional insurances, the employment of security and the removal of redundant items. 3) Costs of procuring the completion works, quantity surveyor’s fees, additional in-house resource, surveys and the employment of other third parties. 4) Any legal fees incurred as a result of termination, for example the drawing up of new contracts for the completion works and the assignment and novation of materials suppliers and sub-contractors etc. This list is not exhaustive and depends on the rele- vant contract in use and the applicable law. Items available in one jurisdiction may be considered too remote in other jurisdictions. There are also items which may be caught by the term consequential losses, and a contract may exclude recovery of such items,12 these may include loss of profit, loss of rent, interest/financial charges etc. Delay damages The employer may be entitled to set-off delay damages related to the late completion of the works. The basis on which the damages are calculated will depend upon the wording of the contract. 13 One issue to be considered is whether a delay dam- ages clause can be applied up to and beyond the DOT. The issue was recently considered by the Court of Appeal in Triple Point Technology Inc (“TPT”) v PTT Public Company Ltd (“PTT”) [2019] EWCA civ 230. In this case, TPT was liable to pay delay damages ‘up to the date PTT accepts such work’. The project had 3 mile- stones; stages 1 and 2 were successfully handed over by TPT, however PTT terminated the contract prior to the completion of stage 3. At this point in time the project was in delay. One of the issues raised in court was whether PTT was entitled to rely upon the delay damages clause, and, if so, whether the delay damages accrued up to the DOT, or beyond. It was found that PTT was en- titled to rely upon the clause, calculated up to the date of completion for stages 1 and 2. However, for stage 3 the clause was found to be inapplicable. The contract stated that delay damages were to be applied ‘up to the date PTT accepts such work’, and therefore the clause could only apply to complete stages of work at the DOT. For incomplete works, PTT was entitled to recover damages at large, up to the date that the works were complete, subject to the necessary burden of proof. Although the Courts stressed that the outcome in each case would depend on the exact wording used, it also doubted recent cases which have held that pre- determined delay damages continue post-termina- tion, until the works are completed by the employer or the replacement contractor. 14 Reasonableness of additional costs, losses and damages The employer may only set-off additional costs, losses or damages, reasonably incurred as a result of the termination. Whether costs incurred are reasonable involves detailed enquiries such as whether the procurement process was appropriate for the works procured, or whether the contract terms were rea- sonable. Disputes can arise in relation to the reasonableness of the rates and prices procured for Contractor B, which are often more than Contractor A’s. It is important to consider a few issues in this respect. It’s not necessarily correct to compare the tender for the original works with the tender for the completion works because, for example, Contractor A may have underestimated the project. Further, a reasonable price at any point in time will, to a large extent, be dictated by market forces, and, given that the ten- der for the completion works will inevitably be carried out later than the original works, varied market conditions may prevail. Issues may also arise if the employer procures Contractor B and its tender is not the most competitive. Whether a price is reasonable is a different consideration from whether a price is the lowest price possible. It is important to keep in mind that a reasonable price requires to be appropriate and fair in the circumstances. A price that is so low, that it is insufficient to carry out the works to the required quality and within the required timescales, may not be a reasonable price. Other factors such as the inefficient nature of the works, or the complexities which arise in completing works commenced by another party, should also be considered. SUMMARY This article sets out a small sample of the issues which may need to be considered when quantifying the financial effects of termination. Parties are encouraged to be mindful of the termination provisions contained within their contracts. Quite often, parties fail to recognise the termination provisions, and therefore, incorrectly value any further payment in accordance with the terms of the contractual payment mechanism. These terms tend to differ somewhat to the party’s entitlements under the termination provisions. References 1, Through a formal dispute resolution process. 2, FIDIC Red Book 2017, assuming that termination is lawful and the Contract survives termination. 3, Or any other type of surveyor / consultant that may assist in agreeing the as-built status of the works. 4, Records may include; photographic / video evidence, witness statements, marked up drawings, surveys and the like. 5, The parties are encouraged to give due consideration to similar matters at contract formation. 6, FIDIC Red Book, Clause 15.3, Valuation after Termi- nation for Contractor’s Default. 7, Set-off made in accordance with Sub-Clause 15.4 8, Fixed priced preliminaries are items which are independent of duration. 9, Sub-Clause 14.5, Plant and Materials intended for the Works. 10, FIDIC Red Book 2017, Sub-Clause 14.1, Contract Price. 11, For further guidance, refer to the RICS Professional Guidance, UK ‘Termination of Contract, Corporate Recovery and Insolvency’. 12, FIDIC Red Book 2017 addresses consequential losses at Sub-Clause 1.15, Limitation of Liability. Such clauses are also commonly referred to as ‘Consequential loss exclusion clauses.’ 13, Triple Point Technology, Inc v PTT Public Company Ltd [2019] EWCA Civ 230. 14, Hogan Lovells, Talking Point: Construction and Engineering, May 2019, ‘Where work is never completed, delay liquidated damages may not accrue up to termination.’ HKA is one of the world’s leading providers of consulting, expert and advisory services for the construction and engineering industry. For over four decades we’ve stood alongside our clients as trusted independent advisers, finding solutions amid uncertainty, dispute and overrun. www.hka.com About the Author Michael Berrigan is an Associate Director working in HKA’s Expert Services team in Dubai, UAE. He is a Quantity Surveyor with 17 years’ experience work- ing initially for main contractors in the UK and for the past 6 years working in the dispute resolution sector in the Middle East, Africa and Asia. Michael has been involved in the preparation of claims and has assisted quantum experts in the preparation of expert reports for matters in dispute adjudication boards and arbitration. Michael has worked on a wide range of international projects in- cluding high-rise buildings, infrastructure works, air- ports, power stations and oil and gas facilities. Michael holds a BSc in Quantity Surveying and Commercial Management from Bolton University, UK and an LLM in Construction Law and Dispute Resolution from Salford University, UK. Michael is a Fellow of the Chartered Institute of Arbitrators (FCIArb), a member of the Chartered Institute of Building (MCIOB), an Associate Member of the Academy of Experts (AMAE) and an Associate Member of the Royal Institution of Chartered Surveyors (ARICS).

by Larry Canary

A little background is needed to place this important topic in proper context. Prior to 1992, Fire & Explosion investigations were more closely aligned with the art of Investigations, rather than actual sci- ence. Investigators relied on what they were taught by those revered in the fire investigation profession or through trial and error. Since 1992, the National Fire Protection Association (NFPA) published a document called NFPA 921 Guide for Fire & Explo- sion Investigations. A complimentary document to NFPA 921 was NFPA 1033, Standard for Professional Qualifications for Fire Investigator. Although both the afore mentioned documents are orchestrated by the United States, they are internationally accepted in many locations and seen as a Best Practice docu- ment. To place a finer point on these documents being internationally accepted, The Institute of Fire Engineering in the UK and the Fire Service College, referenced as recommended reading NFPA 921 and 1033 as part of their Level 5 Award in Fire Investi- gation, dated 10 August 2017. Level 5 Award in Fire Investigations, a more advanced version from Level 2, was designed for fire officers, scenes of crimes officers and others involved in investigating and reporting on incidents involving fires.

Hot-tubbing’, or concurrent expert evidence, has been used for the first time in a Scottish civil court case. Is the experience likely to be repeated? Katherine Doran reports At the end of 2016, Lord Woolman issued his decision in SSE Generation Ltd v Hochtief Solutions AG (2016) CSOH 177. The case concerned liability for the collapse of part of a water-bearing tunnel at Glendoe hydroelectric station in Fort Augustus. This was one of the longest and most technically complex cases to come before the Scottish courts in recent years. The court sat for 91 days; 73,000 documents were lodged, including 37 expert reports and 91 witness statements. Of those, 19 experts gave evidence at proof, and 46 witnesses of fact. The court was faced with the challenge of hearing and comprehending technically difficult expert evidence on matters such as structural geology, rock mechanics and tunnel engineering. The case was the first in the Court of Session to use “hot-tubbing” to hear expert evidence. Hot-tubbing, or concurrent evidence, is a process whereby expert witnesses of the same or similar disciplines give their evidence at the same time in a structural discussion, with the judge acting as chairperson. Concurrent expert evidence is already a feature of civil litigation in England, with a suggested procedure set out in Practice Direction 35, supplementing the Civil Procedure Rules, Part 35. It is also commonly used in arbitration and other forms of ADR. So what does it entail? Views from experience The procedure adopted by Lord Woolman mirrored that set down in Practice Direction 35. His Lordship was also guided by video demonstrations from the Judicial Committee of the New South Wales Commission. It was essentially this: • Counsel for the parties agreed in advance a list of suggested topics to be discussed during the concurrent evidence session. • Lord Woolman initiated the discussion between the expert witnesses by asking one of them to set out his position on a particular issue, then inviting the others to participate in the discussion, questioning one another as appropriate. • Counsel were invited to ask follow-up questions. A 2016 report by the Civil Justice Council on hot-tub- bing (online at bit.ly/2oQRGGC), found the procedure is well liked by judges and practitioners alike. This view was echoed by Lord Woolman in his judgment at para 258: “I found it an extremely valuable exercise and one which I would repeat in suitable future cases. Instead of hearing complex testimony weeks apart, I was able to hear the different opinions at one and the same time. They were also able to challenge one another’s position. This brought the topics into sharp focus. Each expert had to crystallise his position.” When considering the CJC’s report, the English Civil Procedure Rule Committee expressed some caution over the use of hot-tubbing. It noted that hot-tubbing required significant work and time, and early buy-in of all concerned. It was also felt that if hot-tubbing is used, there must be adequate safeguards in place to ensure fairness of the proceedings. This was achieved in SSE v Hochtief by using hot- tubbing in addition to, and not instead of cross- examination, so both parties had sufficient opportunity to test the experts’ evidence. By hearing evidence concurrently, it was possible to focus the key issues and garner the respective positions of the experts on those issues. Conditions for success There are two major factors that will determine the success of hot-tubbing: • Is the case suitable? Lord Woolman commented that the process was most useful where there was anarrow technical dispute – less so where there was little common ground between the parties or the level of detail was too great. • Does the process have the support of all involved? Litigants will need to be comfortable with novel approaches to taking evidence. Expert witnesses need to understand the process and be confident asking and answering questions of one another. Solicitors and advocates will have to agree a procedure up front, and possibly an agenda of topics to be dis- cussed. And finally, judges need to be fully engaged with the case in order to formulate suitable questions and chair a productive discussion. Provided these criteria are met, there is no reason why hot-tubbing should not be used more widely. The opportunity for experts to discuss and question one another is a useful addition to the examination process. This interactive process is likely to crystallise positions, and highlight areas of agreement or divergence of expert opinion. Ideally, this will lead to more measured and reasonable positions being advanced, and ease the decision-making process. Katherine Doran is a senior associate with Holman Fenwick Willan LLP, London, who acted for Hochtief in this litigation Reproduced by kind permission of The Law Society of Scotland www.lawscot.org.uk/members/expert-witness-directory/

by Martin Burns In August 2019, 46 nations, including China and the USA, gathered in Singapore to sign the United Na- tions Convention on International Settlement Agreements Resulting from Mediation. Known more simply as the “Singapore Mediation Convention, it represents an international dispute resolution frame- work, which improves cross-border enforceability of settlement agreements. It provides businesses with certainty and guarantees that have previously been absent in relation to mediated outcomes of disputes. Enforcement of mediated agreements of cross- border disputes is often complicated. The parties may agree to court proceedings in one jurisdiction, but the court's judgment may then need to be enforced in another jurisdiction where the other party’s assets are located. This can involve significant time and costs and prevent a party from receiving monies, or other remedies, that were agreed at the mediation. These potential enforcement issues can easily dampen any enthusiasm the parties had to engage in mediation in the first place. Another thing that can discourage mediation is when parties approach mediation as if it were a “one size fits all” process, and not something that can be easily engineered and deployed to meet the needs and priorities of different sizes and types of businesses. The Singapore Mediation Convention represents a hugely positive step forward for the promotion of mediation of cross-border commercial disputes. And while many commentators have naturally focussed on the fact that the Convention permits quicker and simpler enforcement of settlement agreements, it is the description of what mediation is in Article 2 of the Convention that may do most to encourage parties to use it to resolve their disputes. For many lawyers and other professionals, who regularly use litigation, arbitration and other dispute resolution procedures, the temptation is find a reliable methodology that they understand and stick with it. Some arbitrators and adjudicators will follow the same path, regardless of whether a dispute before them is about a few thousand dollars or many mil- lions, or whether the issues at the heart of a dispute are enormously complex or straightforward I know of a few timeworn arbitrators and adjudicators who have used the same letter templates and directions in every case they have dealt with for decades. It seems they must follow a familiar and well-worn path regardless of the relative complexity and/or value of the dispute they are dealing with. The path they fol- low can often be painstaking and detailed. This may be fine when a dispute is multi-faceted and involves enormous sums of money, but the problem is that these arbitrators and adjudicators can give no consideration to adapting their approach where disputes are about simple clear-cut matters. They will apply the same procedure and take just as long to resolve a simple dispute as they would a complex multi-issue dispute. And it is the parties who generally have to pay for it in time, money and resources. Article 2(3) of the Singapore Mediation Convention defines mediation as a method for resolving disputes whereby they endeavour "to reach amicable settle- ment of their dispute with the assistance of a third person or persons ('the mediator'). The difference be- tween a mediator and a judge, arbitrator or adjudicator is that a mediator lacks “the authority to impose a solution upon the parties". As long as any settlement that a party wishes to en- force falls within this definition, the Singapore Convention applies, even if the process is not actually called a "mediation". Furthermore, there is no need for a mediation be formally supervised by a media- tion institution or conducted by a government and/or institutionally approved mediator. The Convention thus provides a deliberately non-prescriptive definition of mediation. It is this in-built flexibility that makes the Convention meaningful and will thus make mediation an attractive proposition for businesses. For some years, UK commercial operations have been adapting mediation techniques to accommodate their, and their clients’, business priorities and idiosyncrasies. Transport for London (TfL), which is responsible for, amongst other things, running the London Under- ground system, engages many 100s of suppliers on contracts ranging from simple maintenance works to full scale refurbishment of lines and stations. Given the vast array of works and numbers of contracts involved, the potential for disputes between TfL and suppliers has, historically, been enormous. In recent years, however, TfL and contractors have embraced a dispute resolution procedure, known as CAP, which applies mediation techniques, though no one concerned with it actually refers to it as mediation. The procedure involves parties endeavouring to reach amicable settlement of disputes with the assistance of independent third-parties, who are subject matter experts appointed through the Royal Institution of Chartered Surveyors (RICS), who cannot impose settlement. Over the past 3 years, the CAP procedure has greatly reduced the numbers of disputes and associated costs on TfL contracts. CAP is an innovative form of dispute resolution that particularly lends itself to major infrastructure projects where there are lots of suppliers, and potentially lots of money at stake if they get into disputes It is clear that the Singapore Mediation Convention can, and will, offer considerable support to organisations and businesses based in countries that have signed up to it. It will enable parties to develop and implement cross-border dispute resolution procedures that address their special needs and priorities, rather than having to follow someone else’s procedure. Parties can adapt procedures, like CAP, that are designed to help parties achieve agreed settlements and provide certainty that settlements can be simply and effectively enforced. They can even design their own bespoke mediation process in the confidence that it can achieve, not only agreed outcomes but, final and binding results too. Martin Burns RICS, Head of ADR Research and Development 09 September 2019

by Keith McMillan, Chartered Construction Manager. Reflecting on a life in construction, it becomes apparent that many of the changes in legislation which now govern how we approach our expert work actually stems from the construction site. It is the changes in society’s approach to health and safety, the result of mechanisation and the essential adoption of new skill sets brought about by ground breaking inventions. A process which, whether we like it or not, will continue to grow.

Timber fire doors have passed official government testing to confirm that they can withstand the 30-minute standard on both sides of the door.

by Larry Canary

A little background is needed to place this important topic in proper context. Prior to 1992, Fire & Explosion investigations were more closely aligned with the art of Investigations, rather than actual science. Investigators relied on what they were taught by those revered in the fire investigation profession or through trial and error. Since 1992, the National Fire Protection Association (NFPA) published a document called NFPA 921 Guide for Fire & Explosion Investigations. A complimentary document to NFPA 921 was NFPA 1033, Standard for Professional Qualifications for Fire Investigator. Although both the afore mentioned documents are orchestrated by the United States, they are internationally accepted in many locations and seen as a Best Practice document. To place a finer point on these documents being internationally accepted, The Institute of Fire Engineering in the UK and the Fire Service College, referenced as recommended reading NFPA 921 and 1033 as part of their Level 5 Award in Fire Investigation, dated 10 August 2017. Level 5 Award in Fire Investigations, a more advanced version from Level 2, was designed for fire officers, scenes of crimes officers and others involved in investigating and reporting on incidents involving fires.

by Brian Clancy JP, BSc, CEng, FICE, FIStructE, FCIOB, FConsE, MAE, MRICS, MCIArb. Consultant, Brian Clancy Higby Partnership, Cheshire, UK

by Dr Angus Ramsay, MEng, PhD, NRA, PSE, CEng, FIMechE

Introduction

To the uninitiated, engineering might well be a black art. How on earth do people design and build such structures as bridges, and how do they know that they will stand the test of time? This opinion might be reinforced by the regular failures that sadly occur with such structures. In reality, though, the bridge will have gone through a design process which will have used analyses to size the various structural members so that they have sufficient stiffness and strength to withstand any foreseen loads that the structure might see during its life. It should then have undergone a detailed design process whereby the various details in the design, e.g., bolted and welded joints, are investigated for such matters as fatigue resistance. Even seemingly static structures as bridges do see time-varying or transient forces due, for example, to traffic and wind, that induce oscillatory stresses about the mean value which have the potential, through fatigue, to initiate and grow a crack and ultimately fail. These, too, need to be considered at the analysis stage. In a statically indeterminate structure, one that possesses redundancy through multiple load paths, failure of one member may not necessarily mean structural collapse. However, for a statically determinate structure, as considered in one of the studies presented in this paper, this could mean partial or complete structural collapse.

Most people understand that stress is simply force divided by area and that for a safe design the stress needs to be limited to some value. However, unless the structural member or machine component is extremely simple, determining the stress is not a straightforward task. The engineer can begin the process of stress analysis by considering how the load applied to the member or component transfers through it to the supports. Beam theory, a staple undergraduate subject, is often useful here. However, whilst a structural member might well actually be a beam, it may well have details or features, e.g., holes, reinforcement etc., that require it to be considered as a three-dimensional continuum, at least local to the feature, in a manner similar to that required for a machine component.

Engineers like to simplify problems to those that have known theoretical solutions for the stresses. The plate with a central hole under a uniform tension field is a nice example. It shows that the stress is concentrated around the hole by a factor of about three, i.e., the peak stress is about three times the ambient tensile stress and that this figure is more or less independent of the size of the hole! There are many other structural features that can cause stress concentrations but with no known theoretical solution and so if the engineer is to avoid the possibility of early fatigue failure at one of these points, he/she must be able to predict with reasonable certainty the stress concentration factor.

Whilst there is a plethora of published data on stress concentration factors likely to occur at particular design features, they usually apply for a given, and often idealised, set of loads and supports. The true nature of the stress concentration for the actual loading/ support conditions can only be explored by detailed stress analysis using a numerical or computational technique such as the finite element (FE) method.

The FE method works by discretising the component into a mesh of (finite) elements. The elements are normally of simple shapes, e.g., triangular or quadrilateral for two-dimensional, planar problems defined by the position of the vertices or nodes. Within each element the stress is allowed to vary in a defined manner, e.g., a constant or linear variation, and usually it is the nodal values of the stress that define the, as yet undetermined, amplitude of the element stress field. The elements are then assembled using continuity conditions between adjacent elements. The complete numerical model then comprises a set of simultaneous equations which, once suitable supports and loads have been applied, can be solved for the unknown amplitudes of the element stress fields. The FE solution, whilst only an approximation, does have the property that it minimises the error between the FE solution and the unknown theoretically exact solution for the problem. Thus, in a nutshell, FE is an approximate but hopefully convergent method in that with mesh refinement the FE solution should get closer and closer to the theoretically exact solution even if this is unknown.

Whilst the above description of FE seems simple enough and although, nowadays, FE software is extremely easy to use, the whole subject is fraught with pitfalls for the unwary or uneducated user. I discussed in an earlier article for The Expert Witness Journal, [1], some of the issues faced by engineers when using numerical simulation techniques such as FE and outlined approaches for good practice. The engineer must always remember that Computer- Aided Catastrophes (CAC) can and do occur. The Sleipner incident is probably the most notorious example of CAC. This case is discussed further in [2] but, in essence, poor (unconverged) FE results were used to design the submerged concrete base of an oil platform resulting in an underprediction of the true stresses (by some 45%) such that the structure failed as it was being submerged into position on the sea bed. Whilst no injuries occurred, the cost of the incident was in the order of $700M. The only safe approach when using FE results is to adopt the Napoleonic Code of jurisprudence, i.e., Guilty until proven Innocent!

In this article I am going to present two short case studies of recent projects with which I have been involved. Both required FE analysis although for different reasons. Each project underwent significant verification procedures but these will not be presented here. What I would like to show with these case studies is, however, the logical processes which an engineer goes through in order to get to the essence of the problem at hand. In the first study I look at a seemingly straightforward problem of a plate supported around its perimeter and under a uniform load. My client’s structural engineer analysed the plate using a traditional hand calculation and, finding the stresses to be too high, rejected the design and recommended that the plate thickness be doubled. Further consideration of the problem, and use of FE, however revealed additional reserves of stiffness and strength in the plate not considered by the structural engineer which meant that the client’s original design could be shown to be perfectly adequate. This study comes from my core engineering consultancy business. The second study, which comes from a recent project where I acted as a Technical Expert, involves the collapse of a scissor lift caused by the failure of one of its structural members. The lift is actually a rather simple (statically determinate) structure and the stresses in the members can be established exactly using beam theory and hand calculations. However, the failure occurred in a portion of one of the members where reinforcement had been applied. The local analysis of this portion required a three-dimensional FE analysis to pick up the stress concentration caused by the step change in section properties at the curtailment of the reinforcement. The actual study involved providing an opinion on whether the collapse was a result of poor design or operational overload. The opinion I came to is not, for obvious reasons, discussed in this study but the process of arriving at the stresses on which this opinion was based is shown.

Case Study Number 1 – Perforated Aluminium Balustrade

This example comes from a recent project undertaken at the author’s company, Ramsay Maunder Associates (RMA). The company involved in specifying, manufacturing and installing the balustrades had approached their usual structural engineer to ensure that their design met the appropriate codes of practice. The code of practice tells the engineer the loading that the balustrade should withstand and also the maximum acceptable displacement and stress. Balustrades similar to the one being considered here are shown in Figure 1(a).

The approach used by the structural engineer was to use standard tabulated data for the maximum bending moments in unperforated plates. To account for the perforations, the engineer then factored the bending moments up by the ratio of the appropriate cross-sectional area of the unperforated plate (thickness multiplied by plate width or length) divided by the cross-sectional area of the perforated plate. The factored moments were then compared with the yield moment for the 3mm thick aluminium plate to establish whether or not the plate had sufficient strength. It turned out, on this basis, that the plate was not strong enough and the engineer then calculated that the plate thickness would need to be doubled, i.e., from 3mm to 6mm, for it to have sufficient capacity

At this point in proceedings, RMA were approached to see if a more detailed analysis might be able to show sufficient strength for the 3mm plate thickness. Over the years, RMA have performed checks on tabulated engineering data and in some cases found such data to be incorrect – see, for example, reference 3. A good starting point for this project then was to check that the results used by the structural engineer were actually correct. A FE model of the unperforated plate was generated and confirmed the maximum bending moments used by the structural engineer.

In looking at the FE results, the deflection was also noted and the maximum value, which occurs at the centre of the plate, was found to be about 2.5 times the maximum value prescribed in the code of practice! So, not only was the plate failing due to excessive stresses, it was also violating the code through excessive deflections.

Now, for an initially flat plate, transverse loads are transferred through the plate to the supports by bending actions. This is much like the way a beam transmits loads but for the plate there are bending moments in two mutually orthogonal directions. This is all well and good, but as the deflections increase, and, typically, once they become of the same order of magnitude as the plate thickness, membrane action begins to stiffen up the now deflected plate or shell. Membrane action involves forces parallel to the surface of the plate and can be particularly significant if the supports are such that the plate is not allowed to ‘pull-in’. Indeed, it is the membrane action that makes an egg shell so strong – if you’ve not already done this, try squeezing an egg in your hand, you might be surprised just how much pressure it can take before it breaks. In order to account for membrane action, ‘large’, as opposed to ‘small’ displacement theory needs to be adopted. The problem becomes a non-linear one and is more or less intractable through hand calculation. The problem is however easily handled through FE analysis by simply switching on the large displacements feature in the solver.

The plots of displacement as a function of applied load for the plate are shown in Figure 1(b). With small displacement theory the deflection limit is reached at about 40% of the required load. The true behaviour of the plate, which is captured using large displacement theory, shows that the plate can take the full required load without reaching the deflection limit. Now, as the stress increases with increasing deflection, the stresses occurring in the plate are lower than predicted using small displacement theory and are such that the plate can be shown to be compliant with the code of practice for both deflections and stresses.

Case Study Number 2 – Reinforced Structural Member

This example comes from one of the author’s recent engagements as a technical expert. The case involved a scissor lift that had collapsed early in the machine’s life causing a fatality. The scissor lifts shown in Figure 2 are for illustrative purpose only and are not the same as the one considered in this case study. The author performed a structural analysis and assessment of the lift and was then able to provide an opinion whether the design was flawed or whether the operator had overloaded the lift. Whilst the failure is in the public domain, the project was executed under an NDA and so details of the lift have been changed for this article and the author’s opinion on fault left open.

The scissor lift is an interesting structure in that without the hydraulic actuator it is a mechanism rather than a structure. Addition of the actuator turns it into a mechanism which can bear load due to self-weight and applied to the platform through occupants and cargo. It is what engineers term a statically determinate structure, which makes for rather simple analysis but this also means that it possesses no redundancy in case of the failure of a single member, i.e., the failure of any member will, depending on which member fails, lead to partial or complete collapse of the structure.

The basic structure can be analysed by hand calculations. The process proceeds by setting up the equations of equilibrium for each member, assembling these for the structure and is completed by solving these equations to obtain the forces applied to each member. It is a simple matter then to draw stress resultant diagrams, e.g., bending moment diagrams, which define the structural demand on each member. The design engineer would then select a member with a cross section with a capacity capable of meeting this demand. As this was an assessment rather than a design project, the author compared the demand with the capacity of the section as already designed.

The initial assessment showed that the square hollow sections (SHS) of the lift members had insufficient capacity to cope with the demand for the two members attached to the hydraulic actuator. The designer of the lift was obviously aware of this and had added reinforcement to the SHS in the regions of high bending moment. The reinforcement, however, was limited in its extent both around the cross section and along the length of the member, and led to a step change in section properties together with a fillet weld to join the reinforcement to the SHS. In a similar vein to Aristotle’s view that ‘nature abhors a vacuum’, the engineer knows that ‘structural members abhor step changes’, and tend to respond by shooting the stresses up to infinity, at least theoretically!

The initial FE model used beam elements and the basic section properties of the SHS without any reinforcement. The member stresses in this model are high at the point of maximum moment and exceed the yield stress for the material at the point of interest. The point of interest is the member supporting the bottom joint of the actuator which, as a result of the offset of the actuator joint from the central axis of the adjoining member, leads to a step change in the bending moment. This can be seen in the stress contours plotted on the beam model of the relevant member in Figure 3; stresses greater than the yield stress are coloured in silver-grey.

In order to model the stresses in the region of interest when the member is reinforced, a solid continuum model was required. A local solid model was constructed and loaded with forces and moments derived from the beam model. Those keen to point out that reinforcement might lead to a different load path should remember that this structure is statically determinate, i.e., the load path is independent of the relative stiffness of the members.

The understanding of Figure 3 requires some explanation. Starting from the left we have the scissor lift modelled as using beam elements. Move to the right and we see the axial stresses in the member supporting the bottom joint of the actuator. We see a step change in the stresses corresponding to the step change in bending moment at the point where the actuator joins (with an offset) the member. The stresses in the corresponding solid model are shown offset to the right of this figure. The same contour range is adopted for both beam and solid models, and the correspondence of stress levels can be seen. In order to see the peak stresses, we must adopt a view normal to the upper surface of the member. This is shown in the figures to the right-hand side where both beam and solid model results are shown. It is seen here, in the solid model results, that the step change in section does indeed amplify the stress levels to such an extent that the region where the stress exceeds the yield stress for the material extends further than it would have done had the section not been reinforced.

The results presented above are under an overload condition for the lift and show unacceptably high stresses of the sort that might well lead to the rapid development of a fatigue crack. Reinforcement was applied to the region of high bending moment but it was not extended sufficiently beyond the region for the stresses to be brought down to a sensible level, i.e., well below yield. Under normal loading the stresses in this region were well below yield. It is common for mobile elevated working platforms such as this scissor lift to be overloaded and in speaking to a colleague who works in the auctioning of secondhand machinery, the author understands that hire companies generally sell their lifts off after only a year of operation precisely because they cannot guarantee that they have not been overloaded.

Discussion

Projects, such as the type described in this paper, provide challenges and are therefore extremely interesting and having projects coming from industry as well as through expert witness cases work well together with the two streams of business complementing each other.

The successful outcome of both projects required a developed understanding of structural mechanics together with a specialist understanding of how to model such problems using FE analysis so as to provide sound and robust results. Neither of these skill sets come as standard with a graduate engineer and, on the whole, require a mature and experienced en gineer to be able to tackle such problems reliably.

The author has developed these skills and specialisms over a thirty plus year career working both as a mechanical engineer at the sharp end of design and analysis of turbomachinery and also as a structural engineer in the nuclear industry assessing structures for structural integrity under the simulated action of earthquakes. One of the key skills required in acting as a technical expert or as an expert witness is the ability to explain clearly and concisely what your opinion is and how it was obtained. This often requires distilling rather technical matters into a pithy and well-illustrated argument that is understandable by an intelligent layperson. This may, of course, need to be done orally at a hearing, but possibly more importantly the product of a technical expert is generally a report in a written legal format. In presenting the case studies in this short article, the author has attempted to use this distillation process and it is hoped, as the reader, you will understand and find a new realisation of what an engineering technical expert actually does.

In closing this article it should be noted that structural engineering and the analysis of stresses in both structural members and mechanical components is just one field of activity that typifies engineering practice.

References

[1] Angus Ramsay, ‘Simulation Governance for the Expert Witness’, The Expert Witness Journal, Vol. 1, Issue 20, pp 86-93, Summer 2017.

[2] Angus Ramsay, ‘The Sleipner Incident; A Computer- Aided Catastrophe Revisited’ The NAFEMS Benchmark Challenge Volume 2, NAFEMS, 2015. www.ramsay-maunder.co.uk/downloads/nbr06.pdf

[3] Angus Ramsay & Edward Maunder, ‘An Error in Timoshenko’s Theory of Plates & Shells’, The Structural Engineer, June 2016. https://www.ramsay-maunder.co.uk/knowledge-base/ publications/an-error-in-timoshenkos-theory-of-plates and- shells/

Acknowledgements

The author is grateful to Dr Edward Maunder, a practising structural engineer and the Reverend Max Ramsay, an intelligent and interested amateur, f or their reading of and comments on this article.

Dr Angus Ramsay MEng, PhD, NRA, PSE, CEng, FIMechE

Angus completed a traditional engineering apprenticeship (ICI) before studying at Liverpool, Exeter and the Robinson FEM Institute with a brief intervening period in automotive research and development. He conducted research in computational structural mechanics at IST in Lisbon (equilibrium methods) and Nottingham (yield-line techniques) which was followed by ten years industrial consultancy in mechanical engineering (turbomachinery). He recently acted as an Independent Technical Editor for the NAFEMS Benchmark Challenge Initiative, is a member of their Education and Training Working Group and a Founding Member of the NAFEMS PSE Scheme. The PSE scheme replaces the older NAFEMS Registered Analyst (NRA) scheme. He is a Technical Expert for HKA Global, a company specialising in providing expert engineering and technical services to an international client base and a member of IMechE’s Structural Technology & Materials Group.

Office: +44 (0)1626 867591

Mobile: +44 (0)7917 833 234

www.ramsay-maunder.co.uk

A leading Clinical Neuropsychologist from the University of Exeter has received a prestigious award for his work. Professor Huw Williams won the British Psychological Society’s (BPS) Barbara Wilson Award – the highest UK professional award for clinical neuropsychologists.