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The Structural Engineer

When the President proposed the title of this paper to one of the authors some months ago, it raised a number of interesting points. Firstly, it was quite clear that despite the best endeavours of the Construction Industry Council (CIC) and the construction industry professional institutions and associations to eradicate the phrase ‘structural survey’ from the terminology of the industry, it seems it has clearly become a generic term that defies eradication. Secondly, it reminded the same author of a conversation some 40 years ago in the design office of a large consultancy firm. Junior engineer to senior engineer: ‘A lady’s on the phone; she’s got a house in Hendon – says it has some cracks and distortions. Huh! Can we come out and do a structural survey on it? Surely that’s not a proper thing for consulting engineers to be doing?’ ‘Not only is it proper’, replied the senior engineer, ‘but you have to be absolutely certain that you do it properly. If you don’t, you’re in trouble; if you do, you’ll learn a lot more about buildings and structural engineering from sorting out problems than you’ll ever learn in the office doing new-build design!’ In a nutshell, addressing those topics is the theme of this paper. The paper addresses mainly smaller buildings, say below five storeys and upon which rapid opinion may reasonably be expected by the client, but includes all types – commercial, domestic, industrial, whatever! So probably 95% of the UK building stock is encompassed by the comments within this paper. Brian Clancy, BSc, CEng, FIStructE, FICE, FCIOB, MRICS, MCIArb Consulting Engineer, Cheshire Bob Stagg, BSc, CEng, FIStructE, MICE Alan Conisbee & Associates, London

The Structural Engineer

Structural engineers are increasingly finding themselves assessing existing structures rather than designing new ones. These need to be checked because loads have changed or the materials have deteriorated, or simply because the owner (or an insurance company) wants reassurance that the structure is adequate. Many of these structures are failing the checks, which results in work for the engineer but expense for the client and a feeling amongst the general public that we are surrounded by bridges and buildings that are inadequate. But is this really the case? Very few structures actually collapse because a slightly increased load overcomes a slightly reduced load capacity caused by corrosion. Gross errors do happen – a 20t truck driven over a bridge with a 2t weight limit is not something the engineer can be blamed for, but corrosion of critical structural elements, such as prestressing tendons, is something for which engineers should check. The problem to which this paper is addressed is the structure which has apparently been giving good service for many years which suddenly appears to be inadequate because of a reanalysis. The relationships are considered between elastic theory and plastic theory, design methods and analysis methods, and the upper and lower bound theorems. These raise various conflicts for engineers that can have important consequences. Chris Burgoyne, MA, MSc, PhD, CEng, MIStructE, MICE Dept of Engineering, University of Cambridge

The Structural Engineer
The Structural Engineer

The first organised motorsport event was a 126km Reliability Trial that was run from Paris to Rouen in 1894. It was organised by Le Petite Journal, a French newspaper, and the winning ‘horse-less carriage’ had to be ‘safe, easily controllable and reasonably economical to run.’ Twenty-one entries left Paris on 22 July, and the first home was Count de Dion in a steam driven De Dion tractor. Unfortunately for him, the jury decided that his car was not a practical road vehicle and instead awarded the prize jointly to the next two leading cars, a Panhard-Levassor and a Peugeot. The average speed of the winning car was just 16km/h. The story of motor racing over the next 100 years is a great example of the sequential development of technology for a single purpose. From the first ever purpose built racing cars of the early 1900s, through the development of engines, chassis, tyres, aerodynamics and control systems, engineers have been at the heart of technological advancements throughout. By comparison with the Paris to Rouen race, a modern F1 racing car reaches speeds of up to 360 km/h, more than 20 times that of this first ever run. Modern aerodynamics have been tuned to provide a downforce of 2.5 times the weight of the car at full speed and provided that the car is travelling faster than 160km/h, it will theoretically carry its own weight upside-down. Engines weigh only 90kg, they can generate 900bhp at 19 000rpm and at full throttle, an F1 fuel pump delivers petrol faster than water flows out of your kitchen tap. Each car carries about 1.5km of wiring that pulls data from approximately 120 sensors that are located around the body of the car, each providing essential information about performance, orientation or load that is communicated back to the pit crew by on-board telemetry. The software that manages the on-board systems is contained in about half a million lines of code, it manages around 3000 gear changes in an average Monaco Grand Prix and if it mis-times a single gear change by only a fraction of a second then the gear box will disintegrate. There can be no doubting the speed of development that is forced upon a Formula 1 team. Fierce competition and numerous and changing regulations necessitate new design approaches in order to gain the few milliseconds that can separate winners from losers. With top teams such as McLaren-Mercedes budgeting around $500 million for a single season, the stakes are high and in this same period, a group of engineers will be expected to make significant step-changes in technology, set-up and strategy in order to find and maintain some form of ongoing competitive advantage. Ron Dennis, Chairman and CEO of TAG McLaren Group, summarises ‘F1 is all about speed,: not just speed on the track but also speed of development. That, in turn, mostly equates to speed of calculation. The faster the engineers can get their calculations done, especially with regard to the complexities involved in 3D v

The Structural Engineer