Evening Meetings

This evening meeting takes place at Imperial College London (South Kensington Campus, Skempton Building) and will begin at 6pm. Registration is not necessary and non-members are welcome to attend. This talk will unfortunately not be broadcast online. Please see the flyer for further details about the meeting.

This meeting is organised by the Wind Engineering Society and chaired by John Kilpatrick. The speaker is Andrew Allsop from Arup.

The discussion and workshop aims to explore in an accessible way the differences between time-history and the more common gust factor and frequency-domain methods for providing wind loads on complex roof structures.

The presentation is based on a number of different roof structures for which linear time-domain analysis was found to give a more realistic sense of the roof behaviour and, in some cases, indicates very different behaviour compared to some classic assumptions in common use.

In the early years of wind engineering, developing rapidly only from the latter half of the 1960s, our ability to measure and process data from large number of pressure taps was severely curtailed by the cost of computing. Time- and computing-efficient frequency domain methods were developed based on assumptions of static and dynamic behaviour which don’t always hold well for major structures we are designing today.

One example is that dynamic loads are distributed according to mass and mode-shapes, whereas direct wind loads are distributed according to area and the nature of the wind fluctuations. With the current computing power of even laptop computers, what’s preventing us working in the time domain more regularly?

Andrew Allsop is a Fellow of the UK Wind Engineering Society and a Director and Arup’s leading wind engineer based in London.

Please note there is no charge and non-members of the Society are always welcome to attend. For further information or to express an interest in attending, please contact Tim Fuller at the ICE on: Tel: 020 7665 2234, Fax: 020 7799 1325, Email: This email address is being protected from spambots. You need JavaScript enabled to view it..

Vibration is an inherent problem in rotating machinery and one of the main concerns when designing aero engine components. The effects of vibration can be an ongoing issue during aircraft service and are a common feature of failure investigations. The presentation will provide a practical guide to the tools and methods commonly adopted in the assessment of aero engine vibration.

Human-induced vibrations cause problems in a variety of civil engineering structures, including office floors, commercial buildings, hospitals, footbridges, staircases, sports stadia and others. These problems have been exacerbated in recent years by the trends towards ever more lightweight and slender structural forms and more open-plan building layouts, resulting in structures with lower mass, stiffness and damping. Traditional techniques to control vibrations include structural modifications (adding mass and stiffness) and a range of passive control technologies (TMDs, viscoelastic treatments, etc.). Unfortunately, these measures are often ineffective and/or expensive. This presentation gives an overview of more advanced technologies that have potential application to human-induced vibrations in civil structures, including active vibration control, semi-active control and hybrid control (combined active/passive). Results from recent research into their performance benefits are also presented. These advanced technologies offer more effective means of controlling vibrations in problematic structures than traditional methods and may offer a way to achieve ever more slender and efficient structures in the future.

This technical lecture from Dr Andrew Mair and Andreas Nielsen of Jacobs will provide an insight into earthquake engineering, with a focus on current practice in the UK, but also drawing from international experience. The speakers will discuss many aspects of earthquake engineering, from seismic hazard studies, through to seismic analysis and design. Examples from recent commissions will be presented.

Seismic performance objectives are continuously changing due to the devastating effects of earthquakes. This is inspiring new design and retrofit methods, which aim to reduce or isolate damage even for very large earthquakes. In this Presentation, the ability of 'rocking' to isolate the structure from the ground motion will be considered.

On the 6^th April 2009 at 3:32am local time, a 6.2 M_Wearthquake hit the Abruzzo region of Italy. The epicentre of the earthquake was located 3.4 km SW of Aquila, the administrative capital of the region of Abruzzo. Aquila had a population of more than 72,800, and was devastated by the earthquake. The earthquake intensity reached IX EMS-98 in the proximity of Aquila. In total the earthquake killed 308 people, injured over 1,500 people and approximately 67,500 people were left homeless. The close proximity of the causative fault to the town of Aquila caused near total collapse of historical masonry buildings in its town centre, including the town hall, the national museum of Abruzzo, and many major historic churches including that of San Bernardino. The earthquake also severely affected reinforced concrete structures of more modern construction. The affected buildings are representative of construction types in many European countries. This earthquake is therefore of particular interest to the UK earthquake engineering community.

The various parts of Eurocode 8 (Design of structures for earthquake resistance) were published in 2004 and 2005. In contrast with US seismic codes, Eurocode 8 presented an integrated approach to the seismic design of the most common structural materials and to many different forms of construction type, including buildings, bridges, pipelines and various types of industrial structure. Moreover, some aspects of the code represented some major innovations compared with what was previously available. Because the change from national to European codes represented such a radical change for European structural engineers, it was decided that all the standards in the Eurocode suite should be subject to a relatively long period of stability, when only corrections or minor amendments would be permitted. However, a period of review has now started which is expected to lead to more extensive revisions being published around 2019. It will be no surprise to learn that the European Commission funding for this exercise will be very limited.

Seismology, in the sense of the observation of earthquakes and speculation about their nature, has a longer history in Britain than many people might imagine. It may come as a surprise to learn that the oldest theoretical writing on earthquakes in Britain dates back to the end of the 12th century. The first attempt in Britain to make a properly scientific study of an earthquake was as early as 1666.

In the early morning on 11th December 2005 CCTV cameras in the Buncefield Oil Terminal and in the surrounding industrial estates captured remarkable images showing the spread of a low lying dense cloud of petrol vapour. After 25 minutes the cloud was 2-3 metres deep and covered an area up to 500 metres across. A devastating vapour cloud explosion then occurred which caused damage in excess of £1 billion. Buildings, storage tanks and other plant on the site itself were completely destroyed by fire and blast damage. All other buildings in the area that the cloud reached were catastrophically damaged and the remains of several large reinforced concrete office and factory buildings had to be demolished. Further away from the site there was significant damage to the cladding of scores of other commercial properties. Many were not usable and had to be completely reclad. The economy of the whole area was blighted for several years. Fortunately there were no fatalities.

Scales of seismic risk may be defined as: (i) real-time, that is during the event; (ii) near-real-time, that is in the aftershock sequence of a major earthquake; (iii) long-term life cycle of degrading structures. This evening meeting will address some research results, which may potentially enhance seismic risk management practice.

Most research on people’s earthquake preparedness activity in highly seismic areas has assumed that low levels of preparedness are attributable to insufficient awareness of seismic risk. However, empirical evidence for this assumption is weak. Furthermore, there is growing appreciation of the role played by social, cultural and emotional variables in risk perception and behaviour.

Like earthquakes, nuclear test explosions generate seismic waves which propagate through the Earth and can sometimes be detected many thousands of kilometres from the location of the explosion. Seismological methods therefore provide a powerful means of monitoring nuclear test explosions, something which is of interest to governments and for monitoring compliance with treaties such as the Comprehensive Nuclear-Test-Ban Treaty.

This talk will give an overview of the waveform technologies used to monitor nuclear test explosions and the Comprehensive Nuclear-Test-Ban Treaty.

Calibration, on the basis of data from centrifuge and shake table experiments, continues to promote the development of more accurate computational models. Capabilities such as coupled solid–fluid formulations and nonlinear incremental-plasticity approaches allow for more realistic representations of the involved static and dynamic/seismic responses. In addition, contemporary high-performance parallel computing environments are permitting new insights, gained from analyses of entire ground-foundation-structural systems. On this basis, the horizon is expanding for large-scale numerical simulations to further contribute toward the evolution of more accurate analysis and design strategies. The presentation addresses these issues through recently conducted large-scale physical and computational representative research efforts that simulate the seismic response of: (1) cohesive backfills behind retaining walls, (2) liquefaction and lateral spreading loads on piles and pile groups, (3) shallow-foundation liquefaction countermeasures, (4) pile-supported wharf systems, and (5) full bridge-ground systems. A discussion of enabling tools for routine usage of such 3D simulation environments is also presented, as an important element in support of wider adoption and practical applications. In this regard, graphical user interfaces and visualization approaches can play a critical role.

SHARE is a Collaborative Project in the Cooperation programme of the Seventh Framework Program of the European Commission. SHARE's main objective is to provide a community-based seismic hazard model for the Euro-Mediterranean region with update mechanisms.

Modern building codes in the United States do not focus on earthquake resilience, the ability of an organization or community to achieve functional recovery after an earthquake. The primary intent of the code is to protect lives by providing an acceptably low probability of collapse in the Maximum Considered Earthquake (MCE). The building code accepts that significant structural and non-structural damage may occur which may not be economically feasible to repair. Recent research shows that the consequences of this damage are significant financial losses for repairs and many months (or even years) of downtime – the time it takes to get back in the building and use it again.

Many of us have been using embedded and post-installed anchors in concrete for some time now. However, many engineers have poor understanding of the failure modes and mechanisms used to verify their adequacy. Of even more concern is that many of us just design anchors on a static basis without understanding the response under applied dynamic loading, including low cycle and high cycle fatigue and response under high strain-rate loading (e.g. blast).

So, it is with great pleasure we have the opportunity to hear from Professor Eligehausen, who is a world leader in this subject, with many excellent publications and papers all well supported by extensive testing.

Over the last two decades, researchers and practising engineers have gradually shifted towards the performance-based seismic design concept, wherein a structure is designed to meet multiple performance objectives under different levels of seismic actions, the objectives being (preferably) defined in terms of displacements (drifts) and/or deformations. This can be done with the aid of either elastic or inelastic analysis. If elastic analysis is used, the expected inelastic response of the building is accounted for by techniques like the secant stiffness approach and the use of ‘over-damped’ elastic spectra. If inelastic analysis is used (using a fully or partially inelastic model), the procedure becomes more involved but also more reliable, since the safety verification involves comparing the inelastic demands against the deformation capacities to verify the performance of the structure with respect to a given performance objective (e.g. allowable member rotation for ensuring life safety under a ground motion having an appropriately selected probability of occurrence). In many of the available design methods, regardless of whether elastic or inelastic analysis is used, the procedure involves a number of iterations.

Professor Peter Woodward will be talking about the development of critical velocity effects for high speed trains over poor soils. The talk will look at the Ledsgard site in Sweden and will show how the critical velocity effect developed with train speed and what the effect was on the track response. The site is analysed using the dynamic fully coupled 3-dimensional non-linear time domain finite element program DART3D and comparisons to the measured response made. The formation of ground Mach Cones as the train speed increases is clearly shown through displaced contour plots of the track response; this is compared to video evidence of ground wave propagation at the site. The development of lateral ground vibration is also discussed through plots of the vertical peak ground velocity. Observations about the peak strains within the soil are presented in relation to the development of non-linear effects and guidance on the analysis methodology given. The research work is put into context for the development of high-speed lines across the world and the implications for ground reinforcement to allow line speed increases discussed.

According to current seismic codes, the foundation soil is not allowed to fully mobilize its strength, and plastic deformation is restricted to above-ground structural members. Capacity design is applied to the foundation guiding failure to the superstructure, thus prohibiting mobilization of soil bearing capacity. However, a significant body of evidence suggests that allowing strongly nonlinear foundation response may be advantageous. The lecture will introduce an alternative seismic design philosophy termed rocking isolation, in which soil yielding is used as a “fuse”.