I propose to discuss land use under two heads: (U) the use of land within the port for the development of port installations, and (6) the availability of land for port development generally and for the location of associated industries. In the port industry we are living through a time of change which is well-nigh unprecedented in its extent and rapidity, and this places the planner in a particular difficulty as part of his job is to attempt to assess with some sense of reality the shape of things to come. When he tries to peer into the future, it may be helpful if he glances over his shoulder and looks into the past, so as to form some historical perspective and discern in the past events some trend, some developing theme, which he can extrapolate into the future.68. Fig. 5 shows four part plans of berths which were typical of the period when they were built. The first is the plan about the turn of the century. It is a very tight, congested layout which gives a berth area of about quarter of an acre to every 100 ft of quay apron. The second plan shows a finger pier of about 20 years later, with a ratio of about half an acre to 100 ft of quay length. The third layout is pretty typical of modern berths in the Port of London for the mechanized handling of break-bulk cargo and gives a ratio of 1.2 acres to 100 ft of quay length. Finally we come to the apotheosis, the container berth, with a ratio of about 2 acres to 100 ft or even 2.5 acres to 100 ft. Fig. 6 gives cross sections of the same berths.69. Looking again at Fig. 5, the site in 1900 is very narrow and the warehousing operations are carried out in the same place as the transit operations. If we look at the horse-drawn vehicle we also appreciate that this was a more leisurely era and that operations did not have to be carried out at the intensive level which we try to attain today. Moving to the 'twenties, we now have a single-storey shed, a much wider area of land and the beginning of mechanization with the quay crane which dominates the site. Then in 1955/65 we have a very much wider berth still and much more intensive mechanization, with the fork-lift truck and the mobile crane. The warehousing operations are removed from the berth. Finally, once again we have the container berth, and what is distinctive about this is that the only operations carried out on the berth are those which must be carried out there, the loading and unloading of the ship and the stacking and marshalling of the containers.70. I think this very brief historical review reveals two trends. The first is the continuous increase in the area of land made available for each berth. The second is the removal from the berth side of some of the operations which are carried out in connexion with the movement of cargo in ports.71. Layouts have responded to developments in handling techniques and machinery, and I think this is probably the most important motivating factor. But very important too is the fact that we have learned to control related operations, even though they are separated physi...
said that quantitative data on the movement of ships at berths was rarely obtained and there was none in the case of Tema, but by all accounts the berths were remarkably quiet. There had been no case of a ship having to put to sea because of ranging.208. The contribution of the Hydraulics Research Station to this happy state of affairs was rather a modest one. There were three major factors in determining the movement of moored ships at berths, only one of which had been studied at the Hydraulics Research Station:(a) the waves in the vicinity; (b) the attenuation of waves by the harbour; (c) the response of the ship and its mooring system to waves.At the time when the harbour was designed there were virtually no wave records.None of the few records that were obtained was harmonically analysed because there were no techniques for making use of such analyses. 209. Again; at the time the Hydraulics Research Station was making its investigation, in 1955, no information on the response of typically moored ships to waves was available. One had merely mariners' views that waves around 1 ft highsome said waves around 2 ft high-were just tolerable for a ship lying alongside. The only one of the three problems that was amenable to study was the attenuation of waves by the harbour, and this was examined minutely in an undistorted model built to a scale of 1 :l 20. 210. Fig. 9 showed a typical response curve, one of a large group which together revealed the performance of the harbour. The ordinate was the maximum waveheight found wherever it occurred along one berth expressed as a ratio of the steady wave-height at sea; the diagram showed how this ratio varied with the period of the waves. The abscissa covered a range of periods from 7+ to 45 seconds. The figure showed that in the 10-S period wave band responses were very satisfactory, around 1/20. At the long end of the scale, around 45 S, the response rose to one third and there was another whole set of data relating to waves with periods extending from 40 S to 5 min, which showed responses generally in excess of unity. 21 1. One wondered whether the harbour's freedom from the very long waves in the 40-S to 5-min period band was due to the absence of such waves on this particular coastline. The speaker was inclined to think that this was not the explanation. On the contrary the waves normally reaching Tema formed a regular swell from distant storms and were precisely of the type likely to set up surf-beats.212. It could be demonstrated that very long waves, or surf-beats, were not too troublesome provided they were not accompanied by shorter period swell. One found that rather stiff ropes were desirable, giving the ship a natural period shorter than that of the surf-beats. The speaker thought that the great success of the design in excluding swell had led to quiet berths in spite of the presence of surf-beats from time to time. Unfortunately this must remain a matter of conjecture because no wave records were available.
DiscussionMr Rudolph Glossop observed that the design of the transit shed a t No. 19 Berth, Eastern Dock, London Dock, was based on a three-hinged portal frame, and so far as he knew, it was the first structure of its kind to be built in Great Britain. He then displayed a series of slides illustrating some practical details of its construction.Each portal frame was composed of four comparatively simple precast units-two top booms and two vertical booms-the maximum weight of any unit being 3-1 tons, which was well within the capacity of an ordinary mobile crane. The vertical booms could be handled without prestress, but the top booms were designed to be stressed before removing from the casting bed. On the whole, those members had been found quite easy to handle on the site, although it had been necessary to be very careful to use the correct lifting points on the top boom. Those were at 2 feet from the tapered end and 9 feet from the outer end. As could be seen from the first slide, that construction gave a span of 74 feet and plenty of head-room clear of obstruction, so that it was well suited to a building in which cargo was to be moved and stacked.All the members had been cast on the site, the concrete being mixed in an ordinary 10s mixer and barrowed to the shutters. The mix had consisted of 5$ cubic feet of coarse aggregate (4 -3 inch), 4 cubic feet of moist sand, and 2 cwt of Portland cement. The water/cement ratio had been 0.3, so that about 1 gallon of water had been added for every bag of cement. It was interesting to note that the natural water-content of the aggregate was usually about 14 gallon per bag of cement, so that slight variations in the natura1 moisture-content of the aggregate had been important and careful site control had been necessary.The results obtained from that mix had been :Strength at 3 days (average value) : 4,720 lb.
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