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The Structural Engineer, Volume 77, Issue 11, 1999
Hipped roofs A number of members have contributed to this discussion. David Cuntrell writes from Norfolk: I am frequently faced with assessing the overall stability of hipped end conservatories, constructed in a variety of materials. These are often built or proposed with few or nonexistent eaves ties and bracing. This usually results in the design of rigid joints for the eaves ring-beam, to-make the structure ‘work’ (a difficult task when using small timber section sizes!).
In the UK, there is an urgent current need to assess the serviceability of many masonry arch bridges as a result of imminent increases in permitted heavy vehicle axle weights within the EU. Vibration techniques, along with some others, can be used to assess the integrity of these structures. The arch ring, as the fundamental loadbearing component of these structures, is of particular interest. Insufficient attention has been paid in the past to the measurement and categorisation of the diferent types of modes of vibration of these structures and the ordering of their successive natural frequencies. This paper investigates the vibration behaviour of segmental arch rings of a range of realistic proportions and the corresponding variations of modal shapes and frequencies. Good comparisons are obtained in some key cases between the results from the modern finite element (FE) method and older previous work. The eflect of variations in the proportions of the arch ring on the natural frequencies is shown graphically, and there is discussion about the corresponding mode shapes. A.J. Pretlove and J.C.A. Ellick
Blackpool Pleasure Beach and Alton Towers haven’t seen anything like this. The London Eye, when completed, will be the fourth highest structure in the Capital, with a wheel diameter of 135m suspended dramatically by the River Thames on a cantilevered spindle over 22m long. This spectacular structure will dominate the view from the Houses of Parliament and Big Ben on the north side of the river, and from the former County Hall building, which now houses two hotels and the London Aquarium, on the south side. John Roberts