Experimental investigation into amplitude-dependent modal properties of an eleven-span motorway bridge

The authors would like to thank their supporters. New Zealand Earthquake Commission (EQC) Research Foundation provided financial support for experimental work (Grant No. UNI/578). New Zealand Transport Agency (NZTA) provided access to the bridge. Piotr Omenzetter’s work within the LRF Centre for Safety and Reliability Engineering at the University of Aberdeen is supported by Lloyd’s Register Foundation. The Foundation helps to protect life and property by supporting engineering-related education, public engagement and the application of research. Ge-Wei Chen’s doctoral study is supported by China Scholarship Council (CSC) (Grant No. 2011637065).Peer reviewe

Dynamic testing and long term monitoring of a twelve span viaduct

Peer reviewedPreprin

Calibration of the finite element model of a twelve-span prestressed concrete bridge using ambient vibration data

Peer reviewedPreprin

Ambient vibration based evaluation of a curved post-tensioned concrete box-girder bridge

Peer reviewedPreprin

Ambient vibration testing, system identification and model updating of a multiple-span elevated bridge

Peer reviewedPreprin

Dynamic properties of an eleven-span motorway bridge at different levels of excitation

Peer reviewedPreprin

Ambient and forced vibration testing of an eleven-span motorway off-ramp bridge

Peer reviewedPreprin

Dynamic behaviour of reinforced concrete bridges in freezing conditions

The strong influence of ambient temperature variation, and especially freezing of near-surface soils, on the transverse modal response of the bridges in cold earthquake-prone regions has been shown in previous research. This paper extends this work and presents an analytical investigation of the modal characteristics of the range of reinforced concrete continuous beam bridges with integral pile-column systems with various geometries over a range of temperatures. The numerical bridge models were geometric modifications of previously validated finite element models of a soil–pile-bridge system representing a prototype three-span bridge located in Anchorage, Alaska. Frozen conditions increased the fundamental modal frequencies across all the bridge schemes. The mode shapes of the short bridges with a few spans undergo significant transformation mainly due to the changes in the stiffness of the pier-foundation-soil system in winter. More flexible, high column and multi-span bridges are less susceptible to these significant mode shape variations. The findings reveal the need for further assessment of the seismic design code requirements for the bridge stock in the cold regions, given that changes in modal parameters may increase the design seismic lateral loads along with potential redistribution of the loads across the structure due to stiffening of the pile-soil system in winter

Ambient vibration tests of a cross-laminated timber building

Cross-laminated timber has, in the last 6 years, been used for the first time to form shear walls and cores in multi-storey buildings of seven storeys or more. Such buildings can have low mass in comparison to conventional structural forms. This low mass means that, as cross-laminated timber is used for taller buildings still, their dynamic movement under wind load is likely to be a key design parameter. An understanding of dynamic lateral stiffness and damping, which has so far been insufficiently researched, will be vital to the effective design for wind-induced vibration. In this study, an ambient vibration method is used to identify the dynamic properties of a seven-storey cross-laminated timber building in situ. The random decrement method is used, along with the Ibrahim time domain method, to extract the modal properties of the structure from the acceleration measured under ambient conditions. The results show that this output-only modal analysis method can be used to extract modal information from such a building, and that information is compared with a simple structural model. Measurements on two occasions during construction show the effect of non-structural elements on the modal properties of the structure

Using the vibration envelope as a damage-sensitive feature in composite beam structures

This article was published in the journal Structures [Elsevier Ltd / © The Institution of Structural Engineers] and the definitive version is available at: http://dx.doi.org/10.1016/j.istruc.2014.10.001A novel approach of damage detection in composite steel-concrete composite beams is suggested. Based on the idea of using the envelope's profile deflections and rotations induced by a moving load, this approach can lead to a practical cost-effective alternative to the traditional use of accelerometers and laser vibrometers.A parametric study has been undertaken, quantifying the sensitivity of the dynamic response of a realistic composite bridge to the presence of damage at different levels of partial steel-concrete interaction and velocity of the moving load.When compared to shifts in the natural frequencies, it has been verified that the proposed approach generally enjoys a higher sensitivity (so damage can be detected at an early stage), is more effective when closer to the ends of the bridge (where shear studs are more likely to be damaged), and displays an ordered set of results (which would reduce the possibility of a false damage).Further work is required to assess the effects of uncertainties and the adoption of more refined models for the moving load