Imperial College London

DrPeterStafford

Faculty of EngineeringDepartment of Civil and Environmental Engineering

Reader in Engineering Seismology & Earthquake Engineering
 
 
 
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Contact

 

+44 (0)20 7594 7916p.stafford

 
 
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Assistant

 

Ms Ruth Bello +44 (0)20 7594 6040

 
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Location

 

321Skempton BuildingSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

93 results found

Xu B, Bompa DV, Elghazouli AY, Ruiz-Teran AM, Stafford PJet al., 2018, Behaviour of rubberised concrete members in asymmetric shear tests, Construction and Building Materials, Vol: 159, Pages: 361-375, ISSN: 0950-0618

© 2017 Elsevier Ltd This paper deals with the experimental behaviour of rubberised concrete members subjected to asymmetric four-point shear loading. A detailed account of tests on 15 prismatic members using conventional concrete as well as rubberised concrete, with relatively high replacement ratios of both fine and coarse mineral aggregates with rubber particles, is given. The results enable direct assessment of strength and complete deformation characteristics including the post-peak response for ultimate behaviour governed both by shear and mixed-mode tensile-shear. After describing the material properties, mix designs and member details, the main observations from detailed measurements of the crack kinematics through a digital image correlation monitoring system, with focus on members developing shear-governed response, are reported. Complementary numerical studies are undertaken using nonlinear finite element procedures which are validated against tests developing shear-governed failures. In order to provide further insight into the key response characteristics, particularly those related to ultimate strength, a number of numerical sensitivity studies employing various constitutive parameters are also carried out. Moreover, comparative assessments in terms of shear resistance, toughness and force transfer across the cracked interfaces are performed and discussed. The detailed test measurements, coupled with the results obtained from the numerical simulations, permit the definition of expressions for representing the shear resistance as a function of the rubber content and concrete compressive strength.

JOURNAL ARTICLE

Bommer JJ, Stafford PJ, Edwards B, Dost B, van Dedem E, Rodriguez-Marek A, Kruiver P, van Elk J, Doornhof D, Ntinalexis Met al., 2017, Framework for a Ground-Motion Model for Induced Seismic Hazard and Risk Analysis in the Groningen Gas Field, The Netherlands, EARTHQUAKE SPECTRA, Vol: 33, Pages: 481-498, ISSN: 8755-2930

JOURNAL ARTICLE

Bompa DV, Elghazouli AY, Xu B, Stafford PJ, Ruiz-Teran AMet al., 2017, Experimental assessment and constitutive modelling of rubberised concrete materials, CONSTRUCTION AND BUILDING MATERIALS, Vol: 137, Pages: 246-260, ISSN: 0950-0618

JOURNAL ARTICLE

Elghazouli AY, Bompa DV, Xu B, Stafford PJ, Ruiz-Teran AMet al., 2017, Inelastic behaviour of RC members incorporating high deformability concrete, Pages: 2399-2406

©Springer International Publishing AG 2018. This paper examines the inelastic behaviour of dissipative zones in structural members incorporating high deformability concrete materials in which mineral aggregates are partly replaced by rubber particles. An experimental study on three large-scale circular reinforced concrete column specimens, subjected to lateral cyclic displacements and co-existing axial loads, is described. The testing arrangement, specimen details, and main observations, are presented and discussed. The test results enable a direct assessment of the strength and ductility characteristics of the specimens. In particular, the study permits an evaluation of the comparative performance of structural members with and without rubber replacement, as well as the influence of external confinement. The results show that, in comparison with conventional reinforced concrete members, structural elements incorporating a significant proportion of aggregate replacement by rubber particles can offer a good balance between bending capacity and ductility, particularly for modest levels of co-existing axial loads. For column members required to sustain substantial gravity loads, favourable performance can be achieved in rubberised concrete members by means of strength enhancement through external confinement such as fibre reinforced sheets. Based on the experimental findings, the main material and response parameters are discussed and their influence on the overall structural behaviour are highlighted.

CONFERENCE PAPER

Sadowski AJ, Rotter JM, Stafford PJ, Reinke T, Ummenhofer Tet al., 2017, On the gradient of the yield plateau in structural carbon steels, JOURNAL OF CONSTRUCTIONAL STEEL RESEARCH, Vol: 130, Pages: 120-130, ISSN: 0143-974X

JOURNAL ARTICLE

Skiada E, Kontoe S, Stafford P, Potts Det al., 2017, Ground motion amplification for canyon topographies with different input motions, 3rd International Conference on Performance-based Design in Earthquake Geotechnical Engineering (PBD-III), Publisher: ISSMGE

It is widelyknown that topographic irregularities influence the surfaceground motions, typically with anenhancement of the response close to convex topographic features,such as ridges and slope crests. Several studies have investigatedthe ground motion at the surface of filled valleys and empty canyons, focusingmainly onthe geometry and the soil characteristics rather than the input excitation.Further investigation of the impact of the input excitation to the ground surface response is needed in order to modifyexisting ground motion prediction models to account for topographic effects. The response of canyons has been previously examined; but mainly focusing on simple wavelet input. This paper considers a fully weathered canyon (i.e., without any in-fill material) aiming to investigate the influence of the input excitationon the surface ground motion through a parametric time-domain finite element (FE) study. A two-dimensional plane-strain model of an idealisedcanyon is considered for vertically propagating SV waves, using both wavelets and recorded earthquakes as input excitation. The model consists of two step-like slopes with slope height (H), in a homogeneous linear elastic soil layer overlying rigid bedrock. Topographic aggravation is presented for several points along the canyon ground surface aiming to derive a pattern of its distribution considering input excitation with different characteristics.

CONFERENCE PAPER

Skiada E, Kontoe S, Stafford P, Potts Det al., 2017, Canyon topography effects on ground motion, 16th World Conference on Earthquake Engineering, Publisher: WCEE

It is broadly known that topographic irregularities effect ground motions, with a particular enhancement of the ground response close to convex topographic features such as ridges and slope crests. Although there are many studies investigatingthe ground motion in the vicinity of slope crests, the response at the toe has not been studied in great detail, as the toe ground motion is normally considered to be smaller than that of the crest. However, for canyon topographies further investigation of the ground motion at the slope toe, where a more complicated response is expected due to the interaction of the canyon sides, is needed. The response of semi-circular and semi-elliptical canyons has been previously examined; butmainly focusing on valleys filled with soft materials. This paper considers a fully weathered canyon (i.e., without any in-fill material) aiming to investigate the influence of a canyon’s width on the surface ground motion through a parametric time-domain finite element (FE) study. A two-dimensional plane-strain model of an idealised canyon is considered for vertically propagating SV waves, using wavelets as input excitation. The model consists of two step-like slopes with slope height (H), in a homogeneous linear elastic soil layer overlying rigid bedrock. The analyses focus first on the canyon slope areas, where the ground motion is altered depending upon the proximity to the topographic irregularity, identifying the main parameters that effect the response. Results are also presented for several points along the canyon ground surface showing that the distribution of topographic aggravation varies significantly with canyon width.

CONFERENCE PAPER

Stafford PJ, 2017, Interfrequency Correlations among Fourier Spectral Ordinates and Implications for Stochastic Ground‐Motion Simulation, Bulletin of the Seismological Society of America, ISSN: 0037-1106

Models for the interfrequency correlations among Fourier spectral ordinates and variances of these ordinates are presented. These covariances among Fourier spectral ordinates can be used to generate accelerograms within a stochastic simulation framework that offer improvements over traditional approaches that make use of deterministic Fourier amplitude spectra combined with a random phase spectrum. The article demonstrates that the accelerograms generated in this new way result in response spectral ordinates that have variances that are very consistent with those predicted by empirical ground‐motion models. In addition, the interperiod correlations among response spectral ordinates obtained from the simulated motions are also consistent with empirically derived response spectral correlations. The study partitions the variance among Fourier spectral ordinates into between‐event, between‐site and within‐event components, and interfrequency correlation models, and variance models are derived for each component. The between‐event correlations are found to exhibit a mild degree of magnitude dependence. An important feature of the new correlation and variance models is that they can be used to generate accelerograms that are broadly consistent with conditional response spectra. This new approach has significant implications for response‐history analyses within earthquake engineering that make use of conditional spectra as a target.

JOURNAL ARTICLE

Bommer JJ, Dost B, Edwards B, Stafford PJ, van Elk J, Doornhof D, Ntinalexis Met al., 2016, Developing an Application-Specific Ground-Motion Model for Induced Seismicity, BULLETIN OF THE SEISMOLOGICAL SOCIETY OF AMERICA, Vol: 106, Pages: 158-173, ISSN: 0037-1106

JOURNAL ARTICLE

Bora SS, Scherbaum F, Kuehn N, Stafford Pet al., 2016, On the Relationship between Fourier and Response Spectra: Implications for the Adjustment of Empirical Ground-Motion Prediction Equations (GMPEs), BULLETIN OF THE SEISMOLOGICAL SOCIETY OF AMERICA, Vol: 106, Pages: 1235-1253, ISSN: 0037-1106

JOURNAL ARTICLE

Fox MJ, Stafford PJ, Sullivan TJ, 2016, Seismic hazard disaggregation in performance-based earthquake engineering: occurrence or exceedance?, EARTHQUAKE ENGINEERING & STRUCTURAL DYNAMICS, Vol: 45, Pages: 835-842, ISSN: 0098-8847

JOURNAL ARTICLE

Skiada E, Kontoe S, Stafford P, Potts DMet al., 2016, Canyon Depth Effect on Surface Ground Motion, 1st International Conference on Natural Hazards & Infrastructure

Topographic effects are rarely accounted for in seismic design codes, despite their potential to significantly modify surfaceground motions. This paper investigates the influence of a canyon’s slope height on the surface ground motion through aparametric time-domain Finite Element (FE) study. A two-dimensional plane-strain model of an idealised canyon isconsidered for vertically propagating SV waves, using wavelets as input excitation. The model consists of two step-likeslopes with slope height (H), in a homogeneous linear elastic soil layer overlying rigid bedrock. The analysis results showthat the distribution of topographic aggravation at the ground surface varies significantly with normalized canyon depthover the input wavelength (H/λ) and it does not necessarily reach a maximum at a specific H/λ ratio, as has been suggestedin previous studies. The validity of this conclusion is investigated for different depths to bedrock and soil layer properties.

CONFERENCE PAPER

Stafford PJ, Sullivan TJ, Pennucci D, 2016, Empirical Correlation between. Inelastic and Elastic Spectral Displacement Demands, EARTHQUAKE SPECTRA, Vol: 32, Pages: 1419-1448, ISSN: 8755-2930

JOURNAL ARTICLE

Bommer JJ, Coppersmith KJ, Coppersmith RT, Hanson KL, Mangongolo A, Neveling J, Rathje EM, Rodriguez-Marek A, Scherbaum F, Shelembe R, Stafford PJ, Strasser FOet al., 2015, A SSHAC Level 3 Probabilistic Seismic Hazard Analysis for a New-Build Nuclear Site in South Africa, EARTHQUAKE SPECTRA, Vol: 31, Pages: 661-698, ISSN: 8755-2930

JOURNAL ARTICLE

Bora SS, Scherbaum F, Kuehn N, Stafford P, Edwards Bet al., 2015, Development of a Response Spectral Ground-Motion Prediction Equation (GMPE) for Seismic-Hazard Analysis from Empirical Fourier Spectral and Duration Models, BULLETIN OF THE SEISMOLOGICAL SOCIETY OF AMERICA, Vol: 105, Pages: 2192-2218, ISSN: 0037-1106

JOURNAL ARTICLE

Molkenthin C, Scherbaum F, Griewank A, Kuehn N, Stafford PJ, Leovey Het al., 2015, Sensitivity of Probabilistic Seismic Hazard Obtained by Algorithmic Differentiation: A Feasibility Study, BULLETIN OF THE SEISMOLOGICAL SOCIETY OF AMERICA, Vol: 105, Pages: 1810-1822, ISSN: 0037-1106

JOURNAL ARTICLE

Stafford PJ, 2015, Variability and Uncertainty in Empirical Ground-Motion Prediction for Probabilistic Hazard and Risk Analyses, PERSPECTIVES ON EUROPEAN EARTHQUAKE ENGINEERING AND SEISMOLOGY, VOL 2, Vol: 39, Pages: 97-128

JOURNAL ARTICLE

Stafford PJ, 2015, Extension of the Random-Effects Regression Algorithm to Account for the Effects of Nonlinear Site Response, BULLETIN OF THE SEISMOLOGICAL SOCIETY OF AMERICA, Vol: 105, Pages: 3196-3202, ISSN: 0037-1106

JOURNAL ARTICLE

Stewart JP, Douglas J, Javanbarg M, Bozorgnia Y, Abrahamson NA, Boore DM, Campbell KW, Delavaud E, Erdik M, Stafford PJet al., 2015, Selection of Ground Motion Prediction Equations for the Global Earthquake Model, EARTHQUAKE SPECTRA, Vol: 31, Pages: 19-45, ISSN: 8755-2930

JOURNAL ARTICLE

Bora SS, Scherbaum F, Kuehn N, Stafford Pet al., 2014, Fourier spectral- and duration models for the generation of response spectra adjustable to different source-, propagation-, and site conditions, BULLETIN OF EARTHQUAKE ENGINEERING, Vol: 12, Pages: 467-493, ISSN: 1570-761X

JOURNAL ARTICLE

Camara A, Nguyen K, Ruiz-Teran AM, Stafford PJet al., 2014, Serviceability limit state of vibrations in under-deck cable-stayed bridges accounting for vehicle-structure interaction, ENGINEERING STRUCTURES, Vol: 61, Pages: 61-72, ISSN: 0141-0296

JOURNAL ARTICLE

Camara A, Stafford PJ, Nguyen K, Ruiz-Teran AMet al., 2014, Comfort in slender bridges subjected to traffic loading and hammering effects, Pages: 1512-1519

The verification of the Serviceability Limit State (SLS) of vibrations due to traffic live loads is typically ignored in the design of road bridges with conventional concrete decks. However, the vibrations perceived by pedestrians usually govern the design in slender and light-weight modern structures that take advantage of the improvement in the structural efficiency, material performance and constructive procedures. On the other hand, the comfort of the vehicle users is traditionally ignored in the design of the bridge because pedestrians are usually more sensitive to vibrations. However, in many highway bridges without pathways the only users of the structure are those in the vehicles (drivers and passengers). Considering all the possible bridge users and their specific sensitiveness, this paper addresses the vibration serviceability in a slender under-deck cable-stayed bridge subjected to heavy traffic loading. In this structure the prestressed concrete deck spans a distance of 80 m with a depth-to-span ratio of 1/80. The vehicle-bridge interaction accounts for aspects traditionally ignored like the wheel dimensions and the cross-slope of the bridge. A large number of time-history analyses is conducted to address the influence of road and vehicle properties on the SLS of vibrations. This work is completed with the study of the vehicle impact when it enters and leaves the bridge. The results clearly demonstrate the influence of the wheel dimensions and the road conditions, as well as the importance of high-order modes on the response.

CONFERENCE PAPER

Douglas J, Akkar S, Ameri G, Bard P-Y, Bindi D, Bommer JJ, Bora SS, Cotton F, Derras B, Hermkes M, Kuehn NM, Luzi L, Massa M, Pacor F, Riggelsen C, Sandikkaya MA, Scherbaum F, Stafford PJ, Traversa Pet al., 2014, Comparisons among the five ground-motion models developed using RESORCE for the prediction of response spectral accelerations due to earthquakes in Europe and the Middle East, BULLETIN OF EARTHQUAKE ENGINEERING, Vol: 12, Pages: 341-358, ISSN: 1570-761X

JOURNAL ARTICLE

Elghazouli AY, Kumar M, Stafford PJ, 2014, Prediction and optimisation of seismic drift demands incorporating ground motion frequency content, BULLETIN OF EARTHQUAKE ENGINEERING, Vol: 12, Pages: 255-276, ISSN: 1570-761X

JOURNAL ARTICLE

ITOI T, STAFFORD PJ, KANEKO M, SATO Iet al., 2014, 21146 Stochastic Ground Motion Simulation for Probabilistic Seismic Risk Assessment, Summaries of technical papers of annual meeting, Vol: 2014, Pages: 291-292, ISSN: 1883-9363

JOURNAL ARTICLE

Modica A, Stafford PJ, 2014, Vector fragility surfaces for reinforced concrete frames in Europe, BULLETIN OF EARTHQUAKE ENGINEERING, Vol: 12, Pages: 1725-1753, ISSN: 1570-761X

JOURNAL ARTICLE

Molkenthin C, Scherbaum F, Griewank A, Kuehn N, Stafford Pet al., 2014, A Study of the Sensitivity of Response Spectral Amplitudes on Seismological Parameters Using Algorithmic Differentiation, BULLETIN OF THE SEISMOLOGICAL SOCIETY OF AMERICA, Vol: 104, Pages: 2240-2252, ISSN: 0037-1106

JOURNAL ARTICLE

Rathje EM, Wang Y, Stafford PJ, Antonakos G, Saygili Get al., 2014, Probabilistic assessment of the seismic performance of earth slopes, BULLETIN OF EARTHQUAKE ENGINEERING, Vol: 12, Pages: 1071-1090, ISSN: 1570-761X

JOURNAL ARTICLE

Rodriguez-Marek A, Rathje EM, Bommer JJ, Scherbaum F, Stafford PJet al., 2014, Application of Single-Station Sigma and Site-Response Characterization in a Probabilistic Seismic-Hazard Analysis for a New Nuclear Site, BULLETIN OF THE SEISMOLOGICAL SOCIETY OF AMERICA, Vol: 104, Pages: 1601-1619, ISSN: 0037-1106

JOURNAL ARTICLE

Stafford PJ, 2014, Crossed and Nested Mixed-Effects Approaches for Enhanced Model Development and Removal of the Ergodic Assumption in Empirical Ground-Motion Models, BULLETIN OF THE SEISMOLOGICAL SOCIETY OF AMERICA, Vol: 104, Pages: 702-719, ISSN: 0037-1106

JOURNAL ARTICLE

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