Adam Crewe
University of Bristol, Department of Civil Engineering, Faculty Member
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A numerical model is presented that enables simulation of the nonlinear flexural response of corroded reinforced concrete (RC) components. The model employs a force-based nonlinear fibre beam-column element. A new phenomenological... more
A numerical model is presented that enables simulation of the nonlinear flexural response of corroded reinforced concrete (RC) components. The model employs a force-based nonlinear fibre beam-column element. A new phenomenological uniaxial material model for corroded reinforcing steel is used. This model accounts for the impact of corrosion on buckling strength, postbuckling behaviour, and low-cycle fatigue degradation of vertical reinforcement under cyclic loading. The basic material model is validated through comparison of simulated and observed responses for uncorroded RC columns. The model is used to explore the impact of corrosion on the inelastic response of corroded RC columns.
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This paper will consider the response of a generic four-span, five support bridge subject to real time-history accelerations taken from the SMART-1 array, Taiwan. It considers the effects of (a) support pier to deck stiffness ratio and... more
This paper will consider the response of a generic four-span, five support bridge subject to real time-history accelerations taken from the SMART-1 array, Taiwan. It considers the effects of (a) support pier to deck stiffness ratio and (b) bridge horizontal alignment to the epicentre on the bridges response. The SMART-1 accelerogram data is corrected using a wavelet de-noising algorithm, bidirectional
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1 Dipartimento di Ingegneria Geotecnica, Universita di Napoli Federico II, Napoli, Italia. E-mail: alsimone@cds.unina.it 2 Dipartimento di Ingegneria Geotecnica, Universita di Napoli Federico II, Napoli, Italia. 3 Dipartimento di... more
1 Dipartimento di Ingegneria Geotecnica, Universita di Napoli Federico II, Napoli, Italia. E-mail: alsimone@cds.unina.it 2 Dipartimento di Ingegneria Geotecnica, Universita di Napoli Federico II, Napoli, Italia. 3 Dipartimento di Ingegneria Geotecnica, Universita di Napoli Federico II, Napoli, Italia. E-mail: afeola@mail.dex-net.com 4 Department of Civil Engineering, University of Bristol, Bristol, UK. E-mail: A.J.Crewe@bristol.ac.uk 5 Department of Civil Engineering, University of Bristol, Bristol, UK. E-mail: Colin.Taylor@bristol.ac.uk RETAINING WALLS UNDER SEISMIC ACTIONS: SHAKING TABLE TESTING AND NUMERICAL APPROACHES
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We are at the maturity convergence point of a set of actuation, control, instrumentation and data analysis technologies that make it feasible to construct laboratory experimental rigs that will allow us to address key controlling... more
We are at the maturity convergence point of a set of actuation, control, instrumentation and data analysis technologies that make it feasible to construct laboratory experimental rigs that will allow us to address key controlling uncertainties in SFSI assessment and design, which can only be addressed by testing at, or near to, prototype scale. This paper will explore the process of innovation that must be established in order to integrate these enabling technologies and thereby create novel test facilities that offer new, high value, capabilities.
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This paper describes how VRML (Virtual Reality Modelling Language) techniques can be used to quickly visualise and interpret large multidimensional experimental data sets. The data sets were created by a series of experimental tests... more
This paper describes how VRML (Virtual Reality Modelling Language) techniques can be used to quickly visualise and interpret large multidimensional experimental data sets. The data sets were created by a series of experimental tests investigating the seismic response of the UK’s Advanced Gas Cooled Reactors (AGRs). At the University of Bristol a quarter scale physical model of an AGR core was developed to support, via experimental testing the existing numerical models that assess the seismic resilience of the AGRs. Outputs from the rig consist of highly detailed acceleration and displacement datasets that contain all the challenges of ‘big data’ processing. A particular challenge has been the interpretation of the response data from even a single shake, which comprises 6DOF time dependent displacement responses of many components. Traditionally this data would be viewed as a series of time histories, but the combination of hundreds of linked 6DOF motions, which all vary with time, m...
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SummaryThe advanced gas‐cooled reactors (AGRs) are the backbone of the United Kingdom's nuclear generation fleet, producing approximately 17% of the country's electricity. Their safety cases are supported by thorough inspection... more
SummaryThe advanced gas‐cooled reactors (AGRs) are the backbone of the United Kingdom's nuclear generation fleet, producing approximately 17% of the country's electricity. Their safety cases are supported by thorough inspection and monitoring of their graphite cores and extensive theoretical, analytical, and experimental studies. This paper presents a unique, highly innovative and technically challenging earthquake engineering project that has provided vital evidence to underpin the seismic safety assessments of the AGRs. Two modelling approaches, one experimental (a multilayer array physical model), and one numerical (a SOLFEC nonsmooth contact dynamics computational model) have been developed to investigate the seismic behaviour of an aged graphite core. The synergetic relationship between the two approaches is a product of insightful collaborative learning between the University of Bristol and Atkins, with the experiments providing material parameters and validation data ...
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SummaryThe complex dynamics of a quarter‐scale model of a graphite nuclear reactor core, representative of the second generation of British advanced gas‐cooled nuclear reactors, is investigated numerically and experimentally. Advanced... more
SummaryThe complex dynamics of a quarter‐scale model of a graphite nuclear reactor core, representative of the second generation of British advanced gas‐cooled nuclear reactors, is investigated numerically and experimentally. Advanced gas‐cooled nuclear reactor cores are polygonal, multilayer, arrays of graphite bricks, with each brick allowed to rock by design relative to each other in accordance with the boundary conditions. A 35 000 DOF, nonlinear finite element model of the core created by Atkins Nuclear, was analysed on a high performance computing facility at the University of Bristol, and a corresponding 8 t physical model, equipped with 3200 data acquisition channels, was built and tested on the University of Bristol 6‐DOF shaking table. In this paper, the two models are subjected to a series of (1) synthetic earthquake and (2) idealised harmonic input motions. The experimental data are used to compare and verify the two models and explore the dynamics of the core. A kinemat...
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Last year's Indian Ocean tsunami was a tragic reminder of the destructive power of earthquakes and of the continuing need for scientists, engineers and technologists to help protect society from their effects. This paper reports on... more
Last year's Indian Ocean tsunami was a tragic reminder of the destructive power of earthquakes and of the continuing need for scientists, engineers and technologists to help protect society from their effects. This paper reports on the development of a UK-designed challenge project aimed at raising awareness among young people worldwide of the global importance of earthquake engineering skills. Since the project's launch in 2000, over 1400 school and university students have taken part—including hundreds in Japan and Taiwan—and take-up continues to rise. The project is a valuable promotional tool for the engineering profession and serves as a model for any engineers planning extra-curricular projects for local schools and colleges.
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Numerous investigations to date have explored the potential use of FRP (Fibre Reinforced Polymers) on concrete and on masonry structures as a strengthening solution. The majority of these studies have focused on the in-plane or the... more
Numerous investigations to date have explored the potential use of FRP (Fibre Reinforced Polymers) on concrete and on masonry structures as a strengthening solution. The majority of these studies have focused on the in-plane or the out-of-plane monotonic loading and the general trend has been to adapt the monotonic loading assessment methods for seismic loading as well. A need to evaluate the mechanical behaviour of the FRP reinforced masonry infill panels under truly seismic conditions has emerged. Full-scale shaking table tests were carried out at the University of Bristol on both reinforced and unreinforced masonry specimens in order to fill the gap in the existing knowledge on the dynamic behaviour of these structures. This paper presents a summary of the experimental programme together with the most relevant findings from tests. The experimental observations on pre-cracking and post-cracking behaviour are meant to provide more understanding on the reinforcement requirements ass...
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In recent earthquakes, many masonry structures have been shown to have poor seismic performance. In particular, small to medium sized domestic structures, formed from masonry panels with openings such as doors and windows, have performed... more
In recent earthquakes, many masonry structures have been shown to have poor seismic performance. In particular, small to medium sized domestic structures, formed from masonry panels with openings such as doors and windows, have performed badly. Therefore, a better understanding of the impact of the openings on masonry panel performance is needed. A specific challenge is that even small windows or door openings can reduce the stiffness and strength of the masonry panels significantly, and this usually results in poor performance or collapse of the masonry structure under seismic loading. For characterizing the impact of openings in masonry panels, a series of numerical models with possible opening sizes have been studied under simulated seismic loading. This paper describes a set of parametric masonry panel models built using the code “3DEC” which is based on the Discrete Element Method (DEM). Unlike Finite Element methods, DEM allows significant displacements between the blocks to d...
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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... more
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 need addressing in both the computational and the physical models employed in the seismic resilience assessments. This paper presents a physical model with quarter-sized components of an array representative of those in AGR cores. The model was developed by the University of Bristol to provide experimental validation to computational tools which model high levels of core degradation. This paper outlines the principles of model design and the relevant aspects of rig development. The rig is tested on an earthquake simulator with the purpose to explore...
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This paper discusses the main results of a full-scale shaking table test campaign carried out under the auspices of the EU funded research project SERA, whose objective is to investigate the seismic performance of three-leaf masonry walls... more
This paper discusses the main results of a full-scale shaking table test campaign carried out under the auspices of the EU funded research project SERA, whose objective is to investigate the seismic performance of three-leaf masonry walls with weak lime-mortar joints. These masonry walls are widely found in seismic prone regions in the Mediterranean area, thus assessing their behaviour under dynamic actions is an important pre-requisite for the seismic vulnerability evaluation of a plethora of historical centres. The first part of the paper presents a preliminary study on the mechanical properties of the wall component materials that was carried out through an ad-hoc experimental campaign. The outcomes are of particular interest for the characterization of the mortar and of the infill materials, that were designed to reproduce the low strength that is typically found in old masonry buildings. The design of the masonry wall that was tested and the test set-up are presented next. The ...
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The current performance-based seismic design philosophy of reinforced concrete (RC) structures relies on the proper detailing of plastic hinge regions where most of the inelastic deformations are expected to occur. The inelastic cyclic... more
The current performance-based seismic design philosophy of reinforced concrete (RC) structures relies on the proper detailing of plastic hinge regions where most of the inelastic deformations are expected to occur. The inelastic cyclic deformation in plastic hinge regions results in a significant tension and compression strain reversals. Unlike buildings where plastic hinges are designed to occur in beams, due to the nature of the structural system of bridges the plastic hinges are forced to occur in piers. As a result, they should be able to accommodate a significant inelastic deformation due to earthquake loading. One of the most common failure modes of RC bridge piers that has been observed in real earthquakes and experimental testing is the buckling of vertical reinforcement. This is then followed by either confined concrete crushing in compression and/or fracture of reinforcement in tension due to low-cycle high amplitude fatigue degradation. Earlier research resulted in the de...
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The graphite components of an Advanced Gas Cooled Reactor (AGR) are subject to ageing processes that lead to changes of geometry and mechanical properties. Such changes need addressing in the safety case strategy of the operator, hence... more
The graphite components of an Advanced Gas Cooled Reactor (AGR) are subject to ageing processes that lead to changes of geometry and mechanical properties. Such changes need addressing in the safety case strategy of the operator, hence the necessity for both the numerical and the physical reactor models to be conservative and to represent high levels of graphite component degradation. This paper presents a quarter scale physical model of a multi-layer array representative of those in AGR cores. The rig was developed by the University of Bristol to support the seismic capabilities of the existing computer core models. The physical model can embed high percentages of doubly cracked bricks in various pattern distributions. Intact and cracked array configurations were subjected to seismic testing on an earthquake simulator. Relevant results of component displacement in the array are presented together with separation data between doubly cracked brick halves that provide evidence of key-...