|
Lorain-Carnegie bridge over Cuyahoga Valley, Cleveland. |
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
Lorain-Carnegie Bridge in Cleveland: MEMBER AMERICAN SOCIETY OF CIVIL ENGINEERS From southeast to northwest, Cleveland is traversed by the winding Cuyahoga river valley, which, while it provides the railroads with an effective entrance to the city, cuts it into two distinct districts as far as vehicular traffic is concerned. To provide crossings over the river and its wide valley, several bridges have been builds, notably the Detroit-superior Bridge near the lakefront and the central viaduct to the south. After 25 years of study on viaduct to connect Lorain avenue on the west of the river with the district to the east, in The Course of which time the project was once abounded after bonds had actually been voted for construction, the citizens of Cleveland are opening, the first week in the November, a $6500000 viaduct 5,865 ft. long, with its eastern terminus at central avenue. Dr. Watson's interest in the project has been continuos since its inception. As consulting engineering for the present structure, he can speak with authority concerning it. For many years the project of constructing a high level bridge over the Cuyahoga valley, connecting Lorain avenue on the west with the east side of the city, was discussed�almost as that for a new union station, now realized. Much of this discussion hinged about the proper location of the eastern approaches. EARLY STUDIES MADE About 25 years ago, I made some studies for a viaduct from Lorain avenue direct to the southwest corer of the public square (Fig.1) but they did not meet with approval, largely because the route went through the main building of the Cleveland telephone company, the cost of removing which at that time was thought to be prohibitive. Later studies were based on the location of the eastern terminus at Huron Road. A bond issue was actually voted to construct such a bridge in 1921, but the project abounded, largely on account of a taxpayers suits attacking the issuance of the bonds, but also partly, no doubt, because of the development of the plans for the railroad station. The wisdom of locating the eastern approach so close to the terminal is questionable. In 1925, John W. Leadley was engaged to make a reportto a special committee of the city plan commission on the proposed bridge. It was then designated the Lorain Carnegie Bridge because Carnegie Avenuehad been winded into a main thoroughfare, and it was felt that the new bridge should connect with in it in order to provide a by pass for through traffic around, and south of, the business section and so relive the congestion in that section and on the overloaded Detroit�Super Bridge. Since Carnegie Avenue extended westward only to east 22d Street, it was necessary to correlate the bridge project with its extension. To accomplish this purpose several plans were proposed. That of Mr. Leadley provided for the eastern approach at Eagle Avenue, the extension of Carnegie to run south of the old Erie Street Cemetery. To carry out this plan properly would require, it was found, a bond issue of some 15 million dollars, and it was the defeated. In order that an unprejudiced study might be made of this question of location, a Citizens fact-finding Committee was organized in 1927,at the suggestion of the Chamber of Commerce and other civic bodies.This committee made an exhaustive study of the factors involved, and finally recommended that the eastern terminus must be located at central Avenue; that a single deck to build first, and provision made for feature lower deck to carry street cars and trucks; and provision made for the separation of traffic between the proposed new bridge and the existing Central Viaduct. The recommendation of the Committee also stated that the main approach to the bridge should be at the level of Ontario Street. In order to meet these requirements, the consulting engineering and architects first proposed to carry the through traffic to and from the new bridge over Ontario and Woodland streets and Broadway,bur this did not satisfy the requirement of the committee that the main roadway should meet the grade of Ontario Street. Plans were then made to carry the traffic to the old Central Viaduct in a subway, but it developed that this arrangement would interfere seriously with probable future street railway subway construction and was not
LOCATION OF LORAIN-CARNEGIE BRIDGE, CLEVELAND Warranted by traffic conditions then existing, or to be expected for some decades. There fore it was determined to develop a first stage of the project that would fit into a future second stage. This first stage contemplates the moving of central Avenue about to 80 ft. to the north where it this intersects Ontario Street, thus providing sufficient width in Central Avenue at this point entirely separate the two streams of traffic from the new and the old bridges. The second contemplates the developments of the circle at the intersection of the Broadway and Central, Woodland, and Ontario streets, which will provide a one way gyratory movement for all traffic lines intersecting at that stage is carried out, it is expected that all street railway tracks will be under ground. Traffic studies conducted by Dr. J. Gordon McKay, Director of the Bureau of Highway Research for Cuyahoga County, indicated that the probable future maximum traffic through this circle would be north and south and not east and west; therefore an elevated roadway carrying Broadway (which runs north and south) across this circle would serve traffic batter than an elevated roadway going east and west. However, the proposed circle will serve to take care of the maximum possible traffic for a long time. Estimates of the probable traffic on the streets adjacent to the new bridge, made by Dr. McKay, and based on traffic counts secured at that time, are as follows:
It is difficult to predict with precision the probable traffic over a new artery such as this, and it is expected that within a short time the bridge traffic will exceed these estimates. The present traffic on the Detroit Superior Bridge is approximately 70,400 vehicles per day. It is estimated that the proposed main Avenue Bridge will carry about 28000 per day, many of which will be taken from the Detroit Superior Bridge. Location of the piers for the new bridge was dictated largely by consideration of property damages. Starting at the east bank of the valley, the stricture passes over the tracks of the Wheeling and lake Erie Railroad, then over Canal Road, an important street, next over the tracks of the Baltimore and Ohio Railroad, and thence over numerous yard tracks of the Big Four rail road on the river. On the West Side of the river lie the tracks of the Erie Railroad, then the main line of the Big Four, and the Erie dock tracks. The problem of so locating piers as to damage these yard facilities as little as possible, to avoid interference with city streets, and to cause minimum disturbance to industrial plants, was a complicated one. Nevertheless it became possible to establish a fairly uniform spacing of piers, gradually in span length as the river was approached. To add to the difficulties, it was required that the structure should be so designed as not to interfere with the carrying out of the river-straightening program of the city. The proposed river cut off lies west of the west pylon of the bridge, and the problem was solved by designing this part of the structure in such a manner that trusses can be inserted under the floor system of the bridge, the posts removed, and the excavation for the cut carried out without interrupting traffic over the bridge. The superstructure of all spans of this bridge between pylons is carried on steel trusses of the cantilever type, alternate spans carrying suspended trusses. The longest span is that over the river, 299 ft. long, which comprises 12 panels, of which the central six are suspended. These cantilever trusses differ from the usual design in that the lower chords are curved to give more pleasing appearance to the structure. Comparative estimates made by engineers on preliminary plans indicated that this design was but slightly more heavies than the usual type with straight chords, and designers felt that the additional weight of metal warranted. The increased weight of structural steel was about 6 percent.
LORAIN-BRIDGE DURING CONSTRUCTION Studies were also made of the comparative economy of continuous and cantilever trusses. Which indicate that there was a saving of about 4 per cent in favor of continuous trusses if no provision had to be made for differential settlement of the piers, and that this would be reduced to about 2 per cent if a differential settlement of 1 in. were assumed. Because of treacherous character of the foundation material, the designers consider it was unwise to use the continuous truss. The citizens committee was desirous that this bridge should have architectural character as well as good engineering design. The engineers have had the assistance and advise of F.R. Walker, of Walker and Weeks, Architects, in determining the general design and the details of the railings and pylons. ARCHITECHURAL FEATURES The architectural features are essentially the curved lower chords of the trusses, The concrete Fascia wall carrying the pies up to the roadway, the concrete pedestals between the trusses, the stone and aluminum railings, and the four massive stone pylons decorated with carved figures of heroic size. The extension of piers to the upper- deck level was not strictly essential to the construction, but was desirable for certain reasons apart from architectural considerations. It was necessary, on this structure, to provide unusually extensive facilities for the carrying of water and gas lines, and for electrical conduits (Fig 2). Where these utilities pass over the piers, working chambers for the bridge railing was a new departure.
TYPICAL CROSS SECTION THE BRIDGE; PROVISION MADE FUTURE RAPID TRANSIT PILE FOUNDATION Wash boring taken at each pier location showed fine sand and gravel present approximately between elevations -- -25 and �43 and then clay, generally increasing the hardness with the depth, but quite variable. Sand mixing with some clay was found at the west hill for a depth of about 40-ft. above the clay. At the East End the clay is at an elevation of about +30 at canal road, and the hard clay about +16. At the river the clay line found about �40, and the hard shale (the underlying "rock") at �164 on east side of the river and �159 on the west side. At the boring on the East Side of the river, gas was found at about elevation �100. In this connection it may be the of interest to note that the river piers of the Detroit�Superior Bridge are at elevation �48, in a stiff blue clay which settled, or rather compressed, about 1 � in. under a dead load of 5.62 tons per square root. PILES USED IN CLAY When clay uncovered at �42,in the foundation for the west river pier, it was so soft that it was found necessary to drive 440 wooden piles 35 ft. long. This was also done for the East River side. These river piers were carried to elevation �42. From previous experience as well as from the boring data, it was expected that a hard clay would be found at this depth and that the footings could be about 3.75 tons per square foot, and the combined dead and live load is about 4.30 per sq.ft.
ORNAMENTAL PYLONS Comparative studies were made of the cost of various types of foundations for these piers, and the method adopted was found to be much less expensive than cylinders or caissons carried to rock, the only practicable alternative. These piers rest on a concrete mat (Fig. 3), 33 ft. 6 in by 100 ft., and 7 ft. thick, heavily reinforced. On this mat are carried hollow shafts, 16 by 20 ft. at the base, tapering to about 8 ft. 6 in. by 17 ft. under the coping. These shafts have walls 3 ft. thick at the base and 2ft. thick at the top. They are about 114 ft. high and have a side batter of I in 50 and an end batter of from about 1 in 35 to 1 in 42 above the ground. The enclosing cofferdams were constructed of steel sheet piling about 38 by 104 ft. and about 60 ft. deep, with steel bracing, allowing all concrete to be placed out of water. DIAPHRAGMS IN PILES Two interesting details of these piers are the horizontal diaphragms, 5 in each, at various levels and the battered interior surface between low and high water to prevent internal ice pressure, which might occur from the freezing of water, held within the shafts.
SECTIONS THROUGH TYPICAL PIERS All piers expected pier 12 and the river piers were supported on concrete piles, each of which carries a dead load of not more than 30 tons per pile, and a combined dead load and live load not to exceed 35 tons per pile. Pier 12 is carried out by spread footings on stiff clay. The east and west abutments and retaining walls are founded directly on sand. PERMISSIBLE LOADS Before determining the live loads and unit stresses to be used for this project, the engineers made studies of various modern vehicles and the loads carried by them. They found that touring cars, placed as close as they can travel at a reasonable speed, produce a load of from 30 to 35 lb. per sq. ft and 20 ton trucks spaced 38 ft. on centers on a 9 ft. lane produce a load of about 117 lb. per sq. ft. This spacing would require slow speeds and consequently a low impact. The average load for congested traffic consisting of mixed trucks and passenger card may be taken at 55 lb. per sq. ft. Assuming the average span of 200ft. eight lines of vehicular traffic, two electric railway tracks, and two 5 ft. walks, the equivalent live loads given by four well-known specifications are as follows:
The live load assumed for this project were equivalent to 83.2 lb. per sq. ft. based on similar assumptions, and were as follows:
For wind loads, lateral force of 30 lb. per sq. ft. was assumed to act on � times the vertical projection of one truss, including the floor system and railing, and � the vertical projection of each truss in excess of 2. Also a wind load of 200 lb. per lin. ft. was assumed to act on the live load of the upper deck, and 300 lb. on that of the lower. A longitudinal breaking force of 1/10 th the live load was added for each deck. When the lower roadways are completed, the total dead load on the bridge superstructure will be about 34,000 lb. per lin. ft of bridge, and the total live load about 13,500 lb. per lin. ft. DESIGN OF CONCRETE WORKS: All concrete piles are of the precast type, 16 in square reinforced with four 0 7/8-in round bars. They vary in length from 30 to 45 ft., and were driven practically to refusal. Driving was done by a hammer weighing 5,000lb., with a 42-in stroke, and the penetration obtained was about 5 blows per inch for the last foot or better. In many cases it was found necessary to use the water jet in order to get these piles down, but in all cases the last 3 to 5 ft. were driven without jetting. The water jet used operated under a 200-lb pressure through a 0 5/8-in.nozzle. Concrete footings were made of 1:2:4 concrete, generally with river sand and limestone aggregate. Tests of standard cylinders of this mix gave an average strength of over 4,000 lb. Per sq. in at 28 days.Pier concrete was composed of 1:11/2:3 concrete of similar proportions. Tests of standard cylinders yielded an average strength of over 5,000 lb.per sq. in., with a slump of from 3 to 5 in. the concrete of all the piers is exposed up to the bridge deck, except that of the two pylon piers, which are faced with stone. FOUR LINES OF TRUSSES RATHER THAN THREE: As noted in the description of the general design, the entire superstructure of the bridge is structural steel, consisting of a series of cantilever spans which carry steel transverse I-beams stringers, placed 6 ft. 10 in. on centers, were spaced. >Four lines of trusses were used. Although comparative studies indicated some advantage in economy of metal by using three lines instead of four, this arrangement did not work out well for the lower deck, which required three spaces, one for street railway or subway tracks, and two for the future truck roadways, While all these facilities are not installed at the present time, full provision is made of their future installation. The main trusses have a minimum depth of 25 ft. and a maximum of about 50-ft. In general, the lower chords are composed of two 30 in plates and four angles; the upper chords of two 24-in plates and four angles; and the web members of two plates from 16 to 25in wide, and four angles, all double laced. Suspended spans are secured to the upper chords of the cantilevers, with a lower chord strut to carry the lateral loads only. STRUCTURAL STEEL CONTAINS COPPER All the material in the main members is silicon steel, and all that in the lateral and sway bracing and in other secondary members in carbon steel. The carbon and silicon steel conformed to the standard specifications of the American Society for Testing Materials, expect that 0.2 percent of copper was added to all the steel used in this bridge, to increase its resistance to corrosion. In tension the allowable working stress in the carbon steel was 18,000 lb. per sq. in. That in the silicon steel was raised to 25,000 lb. per sq. in. Workmanship requirements followed closely the standard specifications of the American Railway Engineering Association of highway bridges. Throughout, the roadway was paved with 3 in. of asphalt, carried on a concrete slab composed of lightweight concrete and reinforced with fabricated units. Sidewalks are of stone flagging 2 in. thick, laid in a bed of asphalt, mastic 0 1/2 in. thick. The curb is unusual, having a total height is 17 in. above the gutters, the face toward the roadway being offset 4 in. at a height of 10 1/2 in. about gutters, forming a 6-in.step. The purpose of this was twofold: first, to protect wheel hubs, and second, to secure sufficient depth under the sidewalks to rake care of the necessary telephone and lighting conduits. The curbs are of granite 10 in. thick by 20in.deep, with a notch 4in. wide by 6� in. deep, and are sawed in four sides to insure a uniform size and smooth surfaces for damp�proofing. DATA ON THE STRUCTURE AS A WHOLE In a project of this size it is of interest to visualize the general dimensions and costs. The length of the project, from Ontario Street in the east to West 25 Th street on the west, is 5865 ft., of which the distance between pylons at each end of the cantilever truss spans is 2886 ft. the individual spans very from 132 ft. to 299 ft. at each end, the main part of the viaduct is reached by approach fills and steel trestles. On the West End, the approach passes over the tracks of the Cleveland Union Terminal and over Columbus Avenue on two separate structures. At the Cuyahoga River the clearance is 180 ft. between fenders horizontally and 93 ft.vertically for a 120 ft. width at top. For Cuyahoga County, F.R. Williams is County Engineer, and A.M. Felgate, Bridge Engineer. I was consulting and designing engineer and F.R. Walker was the architect. The viaduct was build for Cuyahoga County by the Lowensohn Construction Company, contractor for all work expect the structural steel and the two river piers. The Mount Vernon Bridge Company fabricated the structural steel, and the river piers were builds by the Walsh Construction company. The construction cost was $4,750,000 and real estate and property damage together totaled approximately $1,750,000. There remains in the treasury $1,500,000 of the $8,000,000 bound issued voted by the people. Wilbur J. & Sara Ruth Watson Bridge Book Collection, CSU Library. Cleveland Digital Library Webmaster Last updated April 10, 2002 This electronic, World Wide Web edition of the "Lorain-Carnegie Bridge in Cleveland," by Wilbur J. Watson, contains the complete text as found in the reprint of the original Civil Engineering article from 1932. The site is hosted by the Cleveland State University Library and is presented here with the permission of Civil Engineering, which retains all intellectual property rights to the work itself. We thank them for their help and generosity. ã Website copyright 2002 by Cleveland State University. All rights reserved.
|
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
