Academic lead: Dr K Goda

‌Seismic hazard assessment in regions with sparse seismicity is challenging due to large uncertainty, which results from our incomplete understanding and experience about the nature of these events. Available historical data and instrumental observations are rather limited (50-100 years in most cases), compared with major cycles of active faults (in the order of hundreds to thousands of years). Probabilistic seismic hazard analysis provides a convenient mathematical framework to incorporate various kinds of seismic hazard information (earthquake catalogue and geodetic data) into the assessment. It is concerned with the evaluation of likelihood of strong ground motion intensities in terms of peak ground acceleration and spectral acceleration, which may cause destruction of buildings and infrastructure and disruption of economic and social activities. These are essential tools for developing seismic hazard maps and modern seismic design provisions in national building codes. In the past, probabilistic seismic hazard analysis has been carried out for Canada, the UK, Malawi, and Eritrea.

Academic lead: Dr K Goda

Mega-thrust subduction earthquakes cause structural damage to buildings and infrastructure and disrupt essential lifeline services over a large geographical region, generating tremendous economic loss. During the 2011 M9.0 Tohoku Japan earthquake, intense ground shaking with multiple-shock features was observed due to a complex source rupture process involving several strong motion generation areas. Advanced stochastic finite-fault techniques for simulating strong motion time-histories can characterise such shaking. The method is relatively simple in comparison with other methods (e.g. empirical Green’s function method and hybrid broadband method), and has capability of capturing the key features of the observed ground motions. The applicability of the simulated ground motions has also been demonstrated for nonlinear dynamic analysis of structures, which is important for earthquake engineers.

Academic lead: Dr K Goda

Buildings and infrastructure are the fundamental backbone of urban cities and economic activities. Severe damage of structures due to infrequent and large earthquakes causes direct physical and financial distress to a great number of households and companies, and induces indirect ripple effects across regional and national economies. For accurate assessment of aggregate consequences of seismic risk of an urban city, simultaneous seismic effects on assets and facilities, which are correlated in space, need to be taken into account. Moreover, to evaluate seismic loss accurately and efficiently, it is of utmost importance to take account of key uncertainties in contributing factors (earthquake occurrence, ground motion intensity, and nonlinear structural behaviour). The advanced performance-based earthquake engineering methodology can be adopted to develop a rigorous seismic loss model for an urban city. 

Academic lead: Dr K Goda

Recent earthquake catastrophes have highlighted that the financial consequences to stakeholders can be significant. It is necessary to enhance the capability of dealing with such low-probability high-consequence events through integrated seismic risk management by combining hard and soft disaster risk reduction measures. Generally, hard and soft measures are complementary, and such integrated disaster risk reduction solutions are robust against unforeseen and uncertain events. An important difference between hard risk mitigation measure (e.g. seismic retrofitting) and soft risk transfer measure (e.g. insurance) is that the former physically reduces the actual extent of seismic damage, while the latter transfers the incurred loss to a third party based on a pre-agreed risk-sharing scheme. Because the recovery process is nonlinear and dependent on various post-disaster situations (e.g. prolonged business interruption may result in loss of share in a competitive market), earthquake insurance has the effects of accelerating the recovering process. For more proactive seismic risk management, financial instruments, such as earthquake catastrophe (CAT) bonds, can be utilised in addition to conventional insurance/reinsurance coverage.

Academic lead: Dr K Goda

The physical processes of tsunami generation/propagation/inundation have crucial influence on how hazard analysis is formulated and conducted, and what mitigation measures can be adopted to protect our society and assets. Different stakeholders require different tsunami hazard/risk information related to potential effects on coastal communities and infrastructure over a variety of temporal and spatial scales. Understanding the meaning of hazard estimates with regard to epistemic uncertainty of hazard modelling processes is an essential part of probabilistic hazard analysis and thus visualisation of the outcomes of an uncertainty assessment has become increasingly important. Novel stochastic source modelling combined with Monte Carlo tsunami simulation offers new ways of presenting and visualising tsunami hazard analysis results, which are relevant for risk management actions. The developed methodology can be applied to various problems including probabilistic tsunami loss estimation and robust design of coastal defence structures (breakwaters, seawalls, and evacuation buildings).

Academic lead: Dr K Goda

To mitigate ground shaking and tsunami risks for coastal communities, reliable tools for simulating strong motion and tsunami are essential. Although earthquake and tsunami research is at an advanced stage of understanding individual hazard and loss generation processes and computational methods are remarkably progressed, the state-of-the-art methodology that can be applied to multi-hazard earthquake-tsunami risks has not been fully developed, and thus one cannot evaluate the concurrent risks due to these cascading hazards. Importantly, conventional risk analyses for assessing ground shaking and tsunami risks have been undertaken on a hazard-by-hazard basis. Thus the current methodology does not reflect the fact that a building in a coastal town/city experiences a mainshock, which may severely damage the structure, and then, geo-hazard (liquefaction), tsunami, and aftershocks, which may cause additional damage. A new approach for evaluating risks due to cascading seismic hazards has been developed. The novelty of the multi-hazard methodology is that the common physical processes of the earthquake rupture are modelled and their effects are propagated through assessments of individual hazards and risks. 

Academic lead: Dr Anastasios Sextos

‌Our group is leading an H2020 EU-funded Intersectoral/International Research and Innovation transfer scheme between academia and industry in Europe and North America focusing on mitigating seismic risk of buried steel pipeline networks that are subjected to ground-imposed permanent deformations. It aims to develop a decision support system for rapid pipeline recovery to minimize the time required for inspection and rehabilitation in case of a major earthquake. EXCHANGE-Risk involves novel hybrid experimental and numerical work of the soil-pileline system at a pipe, pipeline and network level integrated with innovative technologies for rapid pipe inspection. More information can be found on the Exchange-Risk website.

Academic leads: Dr A Crewe, Prof C Taylor

Advanced Gas Cooled Reactor (AGR) cores are multi-layered arrays of graphite components whose geometry and mechanical properties change under prolonged exposure to neutron irradiation. The presence of cracked components in the arrays later in their operational life may cause disruption of core geometry with implications for fuel cooling and control rod insertion in the event of a severe, but infrequent, seismic event. These ageing issues are being addressed using physical models of an AGR core which has been built in the Faculty of Engineering to provide experimental validation for the computational tools which model high levels of core degradation. The rig has been tested on the shaking table with the purpose of exploring the mechanical interactions inside the array and to output acceleration and displacement data at selected locations. The model rig is capable of providing experimental evidence for the computational modelling methods and is making significant contributions to reducing uncertainties in these methods.

Academic lead: Dr N Alexander

The performance and safety of many civil engineering systems is governed by their response to dynamic loads such as earthquake, wind and traffic. However, there is very little work on the robustness of structures under dynamic loads. In fact, robustness is not well understood even under static loads. Concepts and methods have been developed to investigate the vulnerability and integrity of nonlinear dynamic structural systems. The method involves modelling structures at different levels of definition. Representative finite element simulations are used to generate low-dimensional models which are suited for multiple simulations to identify dependable regimes in the space of control parameters. Proper Orthogonal Decomposition forms a useful basis for the reconstruction of such models and the identification of vulnerable members. Example studies demonstrate that the output from such studies will be of practical use for the safety management of structures under dynamic loads.

Academic lead: Dr Anastasios Sextos

The 7.8 magnitude earthquake on April 25, 2015 that caused extensive damage and left 22,000 people injured, was the worst natural disaster to strike Nepal since 1934. It was followed by a 7.3 magnitude aftershock on May 12. Overall, over 600,000 homes were destroyed including 8,620 damaged schools in the 14 worst-affected districts with 19,700 collapsed classrooms, 12,000 heavily damaged, and another 17,500 with relatively minor damage. Our research efforts are focused on (a) developing a framework for the pre- and post-assessment of school buildings, (b) investigating technically feasible, economically affordable, culturally acceptable retrofit solutions that can be implemented in a rural context using locally available materials, (c) validating numerical predictions used for school design and assessment against laboratory tests, (d) forming simple rules and formulas to update design codes and guidelines and (e) developing new, low-cost/high-performance, construction techniques for school buildings, TLCs and shelters.

Academic lead: Dr A Crewe

Multiple support excitation is caused when different ground inputs occur along the length of a bridge. Much research has been carried out on modelling long span bridges with multiple support excitation both numerically and analytically, however there have been few successful experimental models investigating the effect of this type of input motion on large scale bridges.  To overcome this we designed and constructed a unique multiple support excitation experimental test bed. The bed comprises 5 single axis shaking tables which are independently controlled by 5 actuators. There are however a number of control issues associated with operating this type of experimental rig where the interaction between the test specimen and the test rig itself can have a detrimental effect on the results of the test. This collaborative work with the control group resulted in the development of new control techniques for this type of specimen testing.

Academic lead: Dr Anastasios Sextos

Our group is developing a systematic and comprehensive approach for the assessment and management of seismic risk to urban and interurban roadway networks (inclusive of roads, motorways, bridges, overpasses, embankments and abutments, tunnels, retaining walls, slopes) in earthquake prone areas. The outcome of our approach is a set of earthquake scenarios and maps illustrating the spatial distribution of seismic demand, vulnerability assessment of all structural and geotechnical components within the network and a reliable evaluation of the expected urban and inter-urban direct and indirect losses of the entire network.

Academic lead: Dr Anastasios Sextos

Our research focuses on the development of a holistic methodology to account for the effect of spatially variable earthquake ground motion on the response of long bridges considering ground motion incoherency and wave passage effects, soil-structure interaction and local soil and site response. Based on laboratory experiments, free field and on-structure measurements, the influence of higher mode excitation is investigated while design codes and guidelines are critically assessed.

Academic lead: Dr Anastasios Sextos

Field mission of the University of Bristol in collaboration with the Geotechnical Extreme Events Reconnaissance (GEER) Association and the University of Sannio to central Italy after the multiple devastating earthquake events of October and November 2016. Disproportional cumulative damage was evident, particularly for unreinforced masonry structures.

Academic leads: Dr A Crewe, Dr K Goda

Earthquake field observations provide raw damage data of existing built environments and are useful for developing empirical correlation between ground motion intensity and damage severity for earthquake impact assessment of future events. Valuable lessons and insights into new research topics can be gained from the significant earthquakes. Bristol academics have been active in contributing to the UK Earthquake Engineering Field Investigation Team (EEFIT) missions to the 2008 Maule Chile, 2011 Tohoku Japan, 2015 Gorkha Nepal, and 2016 Kumamoto Japan earthquakes.

Academic lead: Dr A Crewe

The earthquake that hit Kobe in 1995 caused severe damage to the city and the surrounding areas. Hundreds of buildings collapsed, roads cracked, bridges were destroyed, there were several landslips, and water, power and telephone lines were severed. As part of an EEFIT team Dr Crewe visited the city a few days after the earthquake.

The structures designed to modern Japanese codes all performed very well with minimal damage, but this only seemed to highlight the deficiencies in the older buildings. Much of the research in the group is aimed at improving current design practices and it was gratifying to see that research is slowly improving our ability to design for earthquakes. However, this earthquake still caused many dramatic failures that show we have a long way to go before we can be really confident in our ability to overcome nature. A full report can be found on the EEFIT website.

Academic lead: Dr J Macdonald

In 1999 a devastating earthquake hit the heart of the coffee growing region of Colombia. Earthquakes are common in this area, the last damaging one occurring just 4 years ago, but this one was different. Whereas most earthquakes so far from the Pacific coast occur at depths in excess of 150km in the subduction zone of the Nazca Tectonic Plate beneath the South American Plate, this one was due to movements of a network of faults relatively near the surface.

Dr Macdonald visited the area as part of an EEFIT team to assess the damage caused by the earthquake. The focus of the visit was to learn from the engineering failures, and successes, to improve future design and construction practice and to inform earthquake engineering research. Overall the trip showed that although the consequences of this earthquake were very severe, progress has been made in earthquake-resistant design. Modern techniques are successful if carried out with care, but there is still a long way to go in ensuring good practice at a practical level, particularly in developing countries.

A full report can be found on the EEFIT website.

Academic lead: Dr A Crewe

The IDEERS (Introducing and Demonstrating Earthquake Engineering Research in Schools) activities started in 2000 with a local schools competition.  The competition was developed to increase general awareness of the importance of good design and help reduce the likelihood that inappropriate structures are built where earthquakes are a hazard. Since then the scope of the competition has expanded and the concept of a seismic design competition for schools been adopted internationally by NCREE in Taiwan as a way to increase public awareness of earthquake engineering research across the world.  The local activity is supported by a website which is available for schools and the research group is happy to test models for schools between our other ongoing testing on the shaking table.