Shallow Wedge Research Articles

THE STRENGTHENING OF HAMMERSMITH BRIDGE.

The suspension bridge over the River Thames at Hammersmoth with a main span of 422 ft, was opened in 1887. It carries a 2-lane carriageway and two footways. The chains are of mild steel, the structural towers, suspenders, cross girders and balustrading of wrought iron, and the decking of timber. When failure of some short suspenders, the inadequacy and suspected fatigue of the stiffening girders, seizure of the chain saddle rollers and rotting of the timberwork necessitated the replacement of these items, the restraints of 'listed building' control and maintenance of road and river traffic posed some interesting problems. Temporary 'splint' girders were provided to maintain longitudinal continuity while the stiffening girders were replaced in 24 ft sections, and prefabricated timber panels were used to enable 16 ft lengths of existing deck to be removed and replaced overnight. Temporary gaps in the deck were bridged during the day with portable battledeck units. The 18000 sq ft area of deck was surfaced with a patented gritted epoxy resin and has neoprene filled expansion joints. The chain saddle rollers were replaced by smaller diameter high tensile steel rollers placed between them, the load being transferred to the new rollers by the driving in of shallow wedges with hydraulic jacks. Flexible airtight covers with dessicants now protect the new rollers from dirt and corrosion. /Author/TRRL/

Fluid surface oscillations in a shallow two-dimensional basin

The two-dimensional oscillation of a free liquid surface in a shallow basin of arbitrary cross-section is considered It is assumed that the fluid motion is not influenced by the earth rotation and that the fluid is ideal, Since the linearized equations are not valid in the region of the shoreline, they are used only in the center region of the basin. In the proximity of the shoreline the method of characteristics is used as applied to the nonlinear shallow water equations. The bottom of the basin in this region is approximated by a straight line. Since it is implicitly assumed that the center region drives the shallow wedge at the shoreline, but conversely the shore region does not affect the center region, the usefulness of the solution is confined to the first few cycles only. The analytical solution was checked by applying a numerical method of solution for the entire basin. The agreement was satisfactory over the first two cycles.

The use of wedge filters in X-ray therapy

Summary To assist in obtaining uniform irradiation throughout the treated volume, techniques have been developed using wedge filters, i.e., non-uniform (metal) filters whose thickness varies in one direction across the field. Specifications are given of wedges for use with radiation of 1 mm. Cu h.v.l. and field sizes of 5 × 5 cm., 6 × 8 cm., 8 × 10 cm., and 10 × 15 cm. (the wedge directions being along the first of the two dimensions in each case) to produce isodose curves of approximately 45° slope. Measured isodose curves for these applicators are presented, together with field summations for two wedge fields at right angles, two wedge fields and a central normal field in a hemihexagonal arrangement, and two opposed wedge fields with a normal field at right angles. The use of these techniques in larynx, posterior tongue, antrum and ethmoid sinuses, nose, chest, and abdominal wall, limb, and cerebral treatments are discussed and illustrated by photographs. The use of a shallow wedge in superficial treatment of a curved surface is also briefly considered.