Mill Building Research Articles

Calculation of Effective Lengths and Effective Slenderness Ratios of Stepped Columns

The analysis of stepped columns arises in the design of heavy mill buildings. Such columns are generally loaded at the top and at the section where the cross section changes. The application of the AISC Specification requires that the engineer determine the effective length of each section of the column. This is a problem in elastic stability theory, and the results are dependent not only on the end fixities, but also on the ratio of the end axial load to the intermediate axial load, the ratio of the length of the upper segment to the length of the lower segment, and the ratio of the upper moment of inertia to the lower moment of inertia. In this paper the authors have extended the analysis to three cases of practical interest, not previously considered. Consistent non-dimensional characteristic equations are given for all five cases.

Lessons from Crane Runways

Many engineers consider the design of a mill building to be 90 percent judgment and 10 percent perspiration. While the exact percentages are debatable, there is little question that judgment forms an important part of the design of such structures, particularly with regard to basic load assumptions and the evaluation of "indeterminates"—those mathematical problems with too many variables for exact solution. Some of the questions that must be resolved by the designer are: How many cranes can be expected to operate simultaneously in the general vicinity of a particular column? How often, if ever, will all cranes pick up their maximum loads with the trolleys adjacent to the column? What lateral thrusting forces can occur simultaneously? What allowance should be made for impact? Would the plant be in operation when there is maximum snow load on the roof? How stiff is the variable stiffness truss? How much resistance to rotation will the foundation afford?

The changing complexity of fire and health protection problems in vegetable‐oil processing plants

w HEN my subject was first mentioned to me, it seemed that fire and health protect ion problems had grown more complex with the years. Af te r f u r t he r thought I realized tha t this was not necessarily so. Therefore I shall discuss changes and lack of changes, ra ther than increases, in the complexity of our problems. As addit ional clarification, it should be explained that most of my experience with vegetable-oil fire and health protection problems has been in the crudeprocessing end of the business so what I say is bound to be slanted in the direction of crude milling. Many years ago, when I first had anyth ing to do with a vegetable-oil processing plant, a crude mill was a mult is toried affair, often of brick or stone with wooden floors and roof. Near ly a lways there was a basement that contained the main lineshafts, which in tu rn were driven by a steam engine located somewhere near the middle of the building. The main mill building l i terally was j ammed full of machinery driven by lineshafts and counter shafts. The work spaee between machines usual ly was dark and inadequate. Auxi l ia ry buildings, for seedand products-storage, often were of wood, and many of them were fire traps. Machinery in auxi l iary buildings f requent ly was driven f rom the main engine by means of lineshafts s tretching across the mill yard. As well as I can remember, a great m a n y of our fires were caused by hot bearings, by the rubbing of belts on wood, and by sparks produced by scrap iron passing through machinery. Processing machines, conveyors, and elevators often contained m a n y wooden par ts and l i terally added fuel to the fires. As far as injuries to personnel were concerned, men were hur t by falls, by get t ing caught on line shafts, pulleys, and belts, and by being crushed in the process of handl ing heavy objects by hand. Infections were common because m a n y things were handled by hand and because locker-room and firstaid facilities were poor. In the bull/ handl ing of slow-flowing materials like cottonseed and cottonseed hulls, men often were covered up by caving materials. Regre t tab ly this problem has not been conquered and may even be worse in these days of bulk storage tanks and houses with high side-walls. Although we often feel tha t we have not made much progress in our industry, today ' s crude mills have changed much more than one may think. Most of the older mills that still operate have been electrified and now use group and individual drives. Newer mills have been built on one level and may not have any line shaft ing or open drives at all. Also the new plants general ly are of fire-proof construction. In almost all cases the l ighting and cleanliness have great ly improved; and the men have more and better work-space, locker rooms, and first-aid facilities. The danger of fire a n d / i n j u r y f rom screw conveyors and f rom material e t e ~ t o r s has been great ly reduced by the replacement of the wooden housings with t ight and substantial steel housings. Fires

Mill Architecture in Fall River: 1865-1880

T HE story of American mill architecture in the nineteenth century follows the rise of the cotton textile industry as the intensity of activity shifted from one locality to another. Thus, the early stone mills of Rhode Island, the big brick factories of Lowell, the buildings for the new companies in southern New Hampshire and those at Lawrence represent successsive developments before 186o. During this time cotton manufacturing in Fall River progressed rather slowly, but after the Civil War the industry of the city expanded at a phenomenal rate.1 In nine years twenty-three new corporations were organized, thirty new mills were built, and at least seven full-sized additions were made to old mills, with an increase in capitalization of nearly twelve million dollars,2 a boom which was not shared in anything like equal measure by other textile cities of the northeast.3 The year of most significant activity in the growth of Fall River was 1872; moreover, the full impact of the panic of 1873 was delayed until 1878, when a strong market and new capital brought quick recovery and further progress. The frenzy of mill building at the height of the boom

The prevention of dust explosions caused by high explosive bombs in flour mills

AbstractThe heavy loss of flour mills under enemy attack from the air was shown to be largely attributable to extensive fires resulting from dust explosions initiated by high‐explosive bombs, and a scheme of protection was worked out by Professor G. I. Finch in the capacity of Scientific Adviser to the Fire Research Division of the Research and Experiments Department, Ministry of Home Security. According to this scheme, propagation of the secondary dust explosion was to be prevented by packets of incombustible dust so placed in the mill buildings as to be broken open, and their contents dispersed by the high‐explosive simultaneously with the liberation of combustible dust (flour, etc.) from damaged plant. Refinements to the original scheme were made as a result of the experimental work described.Flame propagation tests showed that a mixture of 90% powdered limestone with 10% sodium bicarbonate would be a suitable incombustible dust for the purpose; the small addition of bicarbonate greatly enhancing the 'flame‐suppressing power of the mineral dust. Investigations into the agglomerating, caking and segregating characteristics of this and related mixtures, mainly in relation to mixture composition and particle size, were carried out, and indications are given of the way in which these factors may be adjusted to give the best all‐round specification for the mixture. An experimental installation in a flour mill is described.

Damping of Textile-Mill Movement by Frahm System

Abstract One of the most prevalent vibration problems in the operation of textile mills is associated with the lay movement of looms. The lay is a relatively heavy member driven with a reciprocating motion in essentially a horizontal path. Harmonic inertia forces are set up, and with the simultaneous operation of many looms large forces are transmitted to the floor and. thence to the walls of the building. Particularly where looms are mounted on upper floors of a mill building, the consequent side-to-side swaying movement is liable to exceed proportions of safety to the structure. In some cases, looms have been moved to lower floors, and in others remedial steps have been taken. Such remedies have taken the form of external abutments to reinforce the walls; the speeds of a number of looms have been changed to reduce the duration of the in-phase periods; and looms have been reoriented to distribute the forces in several different directions. Some of these measures have been helpful but not entirely corrective. The approach described in this paper is to apply to the Frahm tuned vibration damper to the restraint of mill movement.

26) 青島に於ける北向及南向鋸屋根紡績工場の採光及室温の比較について

26) 青島に於ける北向及南向鋸屋根紡績工場の採光及室温の比較について

25) 鋸屋根工場の採光設計について

25) 鋸屋根工場の採光設計について

Wind pressure on a model of a mill building

Wind pressure on a model of a mill building

Stresses in Columns Subject to Combined Axial and Transverse Loading

The most common examples of columns of this class are those supporting elevated railroads, roofs of mill buildings, posts of portals, etc. The common method, of assuming that the lower end of such ...