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Walker C.,Flint and Neill Ltd | Stafford P.J.,Imperial College London
Proceedings of the Institution of Civil Engineers: Bridge Engineering | Year: 2010

Modal superposition techniques such as the responsespectrum method (RSM) can be used to quickly estimate the peak response of a structure to earthquake-induced vibration and, as such, are widely used in preliminary design. Modal-combination rules for use with the RSM are typically founded on assumptions of linear structural behaviour, well-separated natural modes, classical damping and stationary excitation. By contrast, the response of cable-stayed bridges is known to be nonlinear with three-dimensional orthogonal mode shapes that can be coupled and closely spaced. Furthermore, it is widely known that the use of stationary stochastic processes for modelling earthquake excitation is a firstorder approximation and there is thus sufficient reason to doubt the validity of the RSM for estimating the response of cable-stayed bridges. This paper critiques the historical development and theoretical consistency of popular modal-combination rules with a view to assessing their suitability for estimating the response of cable-stayed bridges and their relative performance is investigated using an example finite-element model. In many cases, the more sophisticated modal-combination rules can be reliably employed; however, numerous scenarios are envisaged where such rules are likely to be inaccurate and caution is advised against their use under these circumstances.

Firth I.,Flint and Neill Ltd
Structural Engineer | Year: 2010

For many engineers, the steel box girder story starts with disaster. The memories of the tragic events of 1970 and 1971 are still raw for some, and the implications have been far reaching. But the story is also one of bold innovation, lessons learnt and ultimate success. This paper explores the short history of the steel box girder and reflects on how it has shaped the evolution of the popular modern bridge structures we see today. © Ian Firth.

MacKenzie D.K.,Flint and Neill Ltd | Colford B.,Forth Estuary Transport Authority
Bridge Maintenance, Safety, Management, Resilience and Sustainability - Proceedings of the Sixth International Conference on Bridge Maintenance, Safety and Management | Year: 2012

The operation of major bridges provides a clear insight into some of the limitations within the design process, where the designers' emphasis on strength and stiffness often neglect important considerations of maintenance. Difficulties occur primarily with access and the replacement of components that do not have the same design life as the bridge, resulting in significant increases to operation costs and even the inability to carry out maintenance. Although modern design of cable supported bridges embraces planned cable replacement as a standard design case, issues still abound with items such as the replacement of bearings, joints and holding down bolts and safety fences. In the case of cable replacement, the load case is considered but not the impact on traffic, the use of temporary works and the safety of operators carrying out the works. In the design and build framework where performance specifications work well for strength and stiffness constraint, less attention is paid to the equally important maintenance design case. This paper looks at the difficulties in maintaining major bridges and the examines how designers can consider access and maintenance issues as design cases alongside conventional strength and displacement criteria, resulting in greater reliability of the structure. © 2012 Taylor & Francis Group.

Yeow H.-C.,Flint and Neill Ltd
Proceedings of the Institution of Civil Engineers: Geotechnical Engineering | Year: 2014

The increasing use of the finite-element method in geotechnical design has raised the question of the compliance of this design approach with Eurocode requirements for the ultimate limit state conditions, especially when a more complex soil constitutive model has been used. Past authors have identified several important issues relating to the application of the finite-element method in ultimate limit state design, including the effects of initial stresses, effects of stress history, choice of soil model, significance of the failure of structural member and the timing when the partial factor of safety is applied during the design assessment. In this paper, an advanced ‘Brick’ soil model has been used to demonstrate its application in the design of different geotechnical structures and the effects of the design assumptions used in the design of these structures. The paper also demonstrates the versatility of the Brick soil model in the derivation of the new set of input parameters when the necessary partial factor is applied to the strength of the soil as required in the Eurocode design approach. © 2014, Thomas Telford Services Ltd. All rights reserved.

Wood H.J.,Flint and Neill Ltd
Geotechnical Engineering for Infrastructure and Development - Proceedings of the XVI European Conference on Soil Mechanics and Geotechnical Engineering, ECSMGE 2015 | Year: 2015

The Mersey Gateway Bridge includes a 1km long three tower cable stayed bridge across the River Mersey estuary. To optimise the span arrangement for the superstructure the plan extent of the foundations needed to be minimised. This led to the selection of direct foundations on sandstone bedrock identified at 10- 15m depth below the river bed. A description of the interpretation of the ground investigation data is presented to allow the design of circular spread footings. Details of the assessment of the bearing capacity and stiffness of the foundations are described and related to the proposed construction monitoring to verify the foundation behaviour. © The authors and ICE Publishing: All rights reserved, 2015.

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