David Lilley

Calculation of Dynamic Impact Loads for Railway Bridges Using a Direct Integration Method

Abstract This paper introduces railway bridge assessment in the UK and the concept of dynamic impact loads. The dynamic impact loads demonstrated in the codes of practice in several other countries have been reviewed and have been found to be significantly different in the different codes. A technique for calculating dynamic impact load using a direct integration method has been developed. In many cases, the mass of the train may be similar to the mass of the bridge in heavy railway bridges but the mass of the vehicle is normally neglected in an analysis due to complexities in computation. Time-varying non-linear mass models are employed to reflect the effect of moving vehicle mass. An existing prototype bridge has been selected to compare results from the codes of practice and the technique developed in this study. The correlation between vehicle speed, axle load, and dynamic impact load has been investigated.

A Structural articulation method for assessing railway bridges subject to dynamic impact loading from track irregularities

This paper discusses the importance of track irregularities in railway bridge design, and presents a new technique for calculating the dynamic impact load induced by such irregularities: the structural articulation method. The properties of the combined bridge-suspension system are coupled through global mass, stiffness, and damping matrices. Under the proposed method, the true suspension system over a particular point on the bridge girder at time t is divided into equivalent suspension systems attributed to adjacent finite-element nodes of the bridge. The time-dependent effects of a moving mass are thereby included in the equation of motion.

Design for Next… Year. The Challenge of Designing for Material Change

Abstract From the moment of purchase, pristine objects are subjected to an array of stimuli including wear, impact, heat, light, water and air which alter their tactile and aesthetic properties. Material change is often regarded as ‘damage’ or ‘degradation’, but has potential to be used as a tool to engender emotional engagement to an object. We present a framework for designers to better understand how materials change with use, and in turn how people respond to materials as they change. Key challenges are identified which must be overcome to use this framework in design practice – people’s physical interaction with objects is poorly understood, it is difficult to simulate material change, materials resources for designers do not provide information about material change, and people’s responses to aged materials depend on a complex web of interacting factors.

Train-generated sound within an underground light railway system

Abstract An empirical study has been made to identify important features of sound levels generated within an underground section of a light railway. Measurements of sound pressure level were recorded as trains passed within a few metres of computer-controlled instrumentation during normal daytime operation. Peak values of sound pressure level were identified for each passing train and a method of compensating for train speed was investigated. Further measurements were taken of sound levels as two Metro trains were repeatedly driven through the same section of underground track at different nominal speeds during a night-time possession. Characteristics of sound levels produced by approaching and departing trains have been studied to identify any salient features that may be beneficial in developing a means of monitoring the condition of passing trains. No definitive relationship was identified between train speed and peak value of sound pressure level, although results indicated that higher sound exposure levels and duration when a passing train generates sound levels above a threshold value can be linked to train condition. Further development of the work is planned to provide an automated management tool for identifying trains in need of further inspection and maintenance. The ultimate aim is to improve the efficiency of scheduling for train maintenance and to satisfy environmental needs for keeping train-generated sound to minimum levels.