The mechanism analysis is not new, but it was not of great value until Professor Heyman demonstrated its application. It has now been adopted by the Department of Transport as the primary tool for arch assessment. Unfortunately, the method as used by Heyman can lead to lower assessment loads than does the traditional MEXE method. An unrelated problem is that bridges are often messed using limited data, which leads to some lack of confidence in the results. W.J. Harvey
I have for a number of years been involved in the design of remedial and refurbishment work to existing buildings. Working in this field has made me very aware of the high costs involved in the maintenance of buildings. Often repairs have become necessary as the result of poor management and lack of maintenance, but there have been occasions where defects have been present from the time the building was constructed. It is not unusual in these circumstances for the owner of the building to try various local repairs to overcome the problems, but to find eventually that major works have to be undertaken to make the building perform satisfactorily. When this happens the costs are sometimes much greater than they need be because of such factors as difficult access and the impracticality of replacing structural and fabric components. Often, standard components are no longer available. The result is that the client seeks recompense by resorting to litigation and this, as we all know, affects the practising engineers and contractors by costly defence actions and, ultimately, through professional indemnity premiums. G. Sage
This paper deals with the problem of anchorage at the ends of steel plates glued to the tensile faces of rein forced concrete beams. A simple theoretid study of the force systems at the plate/glue and the glued concrete interfaces is presented. This suggests that high stress concentrations and peeling forces are present at the ends of the plates when the composite beam is loaded in flexure. Tests carried out to investigate the effectiveness of different anchorage arrangements are described in detail. The results from these tests confirm that, at the ends of the plates, interface stress concentrations exist, which have limiting peak values in the region of ã2 X tensile splitting strength of the concrete. Theoretical interface bond stresses, based on simple elastic behaviour, are found to have no consistent relationship to the measured peak values. However, if the maximum (unreduced) plate thickness is always used in these calculations, a simple method is proposed for obtaining a reasonable assessment of the peak stress. The efficiency of the different anchorage details is discussed, and it is shown that the use of additional glued anchor plates gives the best results. These plates overcome the problem of anchorage failure and enable the full theoretical flexural strength to be achieved, together with ductile behaviour. R. Jones, R.N. Swamy and A. Charif
Over the past few years the question of quality has been exercising the minds of many of us. Last year The Structural Engineer carried an excellent series of papersl. Since then, a small working party has been set up to consider where we should go and, more recently, a discussion evening was led by Alex Tait. This will be reported in The Structural Engineer in due course. Professor W.D. Biggs