US3425077A

US3425077A - Bridge roadway construction

Info

Publication number: US3425077A
Application number: US578228A
Authority: US
Inventors: Hans Sievers
Original assignee: Demag AG
Current assignee: Mannesmann Demag AG
Priority date: 1966-09-09
Filing date: 1966-09-09
Publication date: 1969-02-04
Anticipated expiration: 1986-02-04

Description

H. suivERs 3,425,077

BRIDGE ROADWAY CONSTRUCTION Feb. 4, 1969 Filed Sept. 9. 1966 Sheet of 2 ,4 7 TOP/V575 Feb.4, 1969 HSIEVERS 3,425,017

BRIDGE ROADWAY CONSTRUCTION filed Se t, 9. 1966 Sheet 2 of 2 mrwrok MM/s 5/5 miles aj m J TTOR IEYST United States Patent M Claims Int. Cl. E01d 19/12; E04c 2/34 ABSTRACT OF THE DISCLOSURE An orthotropic roadway construction for steel bridges includes a plurality of box-shaped longitudinal ribs which are arranged at the underside of a cover plate parallel to the main bridge girders. Transverse girders transmit the load of the roadway plate to the main girders. At the underside of the cover plate and transversely to the box-shaped longitudinal ribs there are arranged transverse bulkheads, which are located at a spaced location from the cover plate and are connected at each end to the sides of the longitudinal ribs. In addition, fiat middle ribs are arranged and welded to the upper side of the cover plate such as in the same vertical plane as the cross bulkheads arranged below the cover plate.

Summary of the invention This invention relates, in general, to roadway construction and, in particular, to a new and useful orthotropic roadway of flat sheet metal particularly for steel bridges, including longitudinal ribs arranged with intersecting or crossing cross supports below the cover sheet in lines or in assembly between the main supports.

The differential equation on which the calculation of the stresses for the orthotropic plate is based indicates that the load capacity of the plate is dependent on:

(A) The bending strength or stiffness of the longittlidinal ribs with the associated portion of the cover 5 eet;

(B) The bending strength or stiffness of the cover sheet alone in the transverse direction; and

(C) The torsional stiffness of the plate which is proportional to the twisting stiffness of the longitudinal ribs.

The bending strength or stiffness of the cover plate in transverse directions as compared to the bending stiffness of the longitudinal ribs is so small that it may be neglected in the calculation indicated above. The load capacity of the plate therefore predominantly is dependent on the bending stiffness or strength of the longitudinal ribs and of the torsional stiffness of the plate.

In bridge constructions, the roadways are subject-to strongly concentrated individual loads. The bridge stress calculation indicates that it is necessary to construct the roadway in such a manner that the ratio or proportion of the torsional stiffness of the plate to, the bending stiffness of the longitudinal ribs is maintained as high as possible. By doing this there is an advantage because the ribs which are adjacent to the longitudinal ribs, to which the load is directly applied, take a very great part in absorbing the load so that the directly loaded rib is significantly relieved of the load. In respect to the roadway plate of the Koln-Miilheirner bridge in Germany, this problem has not been encountered because in that bridge, the longitudinal ribs which are in the form of fiat beaded steel members have only a very insignificant twisting stiffness or strength.

It has been proposed to construct bridge roadways with longitudinal rib formations in the form of trough-shaped or box-shaped profiles which are opened at the top and to dimension their spacing about equal to the width of the upper profile opening. In this manner, the twisting stiffness of the adjacent ribs is more strongly utilized to 3,425,077 Patented Feb. 4, 1969 relieve the load of the longitudinal ribs which are subjected to the local load. Excellent results have been experienced with such a construction, for example, in respect to the Rhine River Bridge in Germany between Duisburg and Homberg which was opened to trafi'ic in 1954 and in which the box profile was used for the first time. The excellent experience with this bridge caused the bridge builders around the world to use such a construction of a roadway for large bridges.

In the construction of the River Rhine Bridge, between Duisburg and Homberg, it had been found-from tests and calculations that the twisting stiffness or strength of the open box-shaped profiled longitudinal ribs cannot be used along the entire height but due to the distortions and bending forces which occur in the plates of the roadway, the torsional stiffness of the plate has to be reduced. This realization resulted in the additional proposal to arrange transverse ribs or transverse bulk heads to connect the longitudinal ribs with the laterally connecting ribs for the purpose of distributing local loads as much as possible. These cross bulk heads extend parallel to the cross supports which essentially transmitted the loads on the roadway plate to the main supports. The cross bulks heads were arranged between the adjacent longitudinal ribs or a portion thereof and they always extended in one plane. Such a construction was used for the first time in the River Rhine Bridge between Ludwigshafen and Mannheim in 1958 and the construction yielded excellent results. By arranging the cross ribs which are also called cross bulk heads, in the manner mentioned above, the maximum bending of the plate and thus the bending moments which are determinative for the dimensioning of the plate was reduced from to 64%. This was confirmed by tests which were fully in agreement with theoretical calculations.

Based on the considerations of the use of the open box-shaped profile longitudinal rib construction, there always existed the problem that the cover plate or sheet at the connection of the bridge was subjected to considerable cross bending stresses or tensions of alternating sign indications or which tend to reduce the permanent stability and strength of the sheet, particularly in view of the fact that in the cover sheet there were always two axial stresses and tension conditions which prevailed. In conducting further tests, it was found that even with boxshaped longitudinal ribs, additional deformations may ocour in the cover sheet which do not reduce the torsion stiflness or strengthof the plate but which make it clear that the construction obtained in this manner is certainly subject to improvement in respect to its life, to wit, permanent stability.

The present invention is based on the realization that without decreasing the torsion stiffness of the plate the secondary or transverse stresses or tensions in the cover sheet can be reduced to a minimum. This is obtained by a construction in which the transverse bulk heads are only connected with the side walls of the longitudinal ribsand they are located at a spaced location in respect to the cover sheet. In addition, on the upper side of the cover sheet or web, flat steel ribs are arranged in the range of action of each cross buk head and they are arranged to extend substantially vertically upwardly from the surface of the cover sheet to which they are welded. It has been found with such a construction that an exceedingly high torsional strength or stiffness of the plate is rendered possible and consequently a very good cross distribution of the concentrated individual loads is obtained. In particullar the disadvantages occurring during the weldingof the transverse bulk head with the cover sheet. which caused a significant squeezing or press tensions and stresses were due to the fact that the cover sheet in the region in which it is welded with the cross bulk heads must be considered as an infinite stiff member relative to the unwelded parts of the cover sheet. However, if one, in accordance with the present invention, foregoes the welding of the cross bulk heads, at the cover sheet, then squeezing tensions are reduced to a fraction.

However, if the transverse bulk heads are not positively connected to the cover sheet, then a decrease of the torsional stiffness of the plate will take place unless flat steel members are provided on the edge of the top surface of the cover sheet. A novel aspect of the invention is the realization that the fiat steel members or cross ribs on the roadway plates may be utilized for increasing the torsional stiffness .or strength of the plate and at the same time the cross ribs provide means for insuring that there will be no displacement or movement of the asphalt coating in the longitudinal direction of the bridge. It has been usual with bridge constructions heretofore to encounter a large amount of displacement of the asphalt coating which takes place repeatedly when a fiat sheet roadway is employed. The cross ribs are usually applied over the cover sheet and are welded along their entire length, or at least to such an extent that they can take over the thrust flow which is present in the box-shaped longitudinal ribs. The number of cross ribs to be arranged will be determined by economical considerations. The ribs may be arranged to either extend in a straight line or in a slight zig-zag or undulating form.

Accordingly, it is an object of the invention to provide an improved roadway construction particularly for bridges utilizing a cover sheet with longitudinal ribs arranged below the cover sheet which are of trough-shaped con-figuration with an opened top conected to the cover sheet and with interconnecting transverse stiffening members or ribs connected between the longitudinal ribs at a spaced location from the cover sheet and with a cross rib connected to the top surface of the cover sheet which extends substantially vertically upwardly therefrom.

A further object of the invention is to provide a bridge roadway construction which is simple in design, rugged in construction and economical to manufacture, and provides for a structurally stronger roadway and one in which the covering or coating on the roadway will be maintained without displacement.

The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which there is illustrated and described a preferred embodiment of the invention.

In the drawings:

FIG. la is a partial cross sectional view of a roadway constructed in accordance with the prior art and indicating the deformation of the cover sheet of the roadway in the accompanying graph;

FIG. 1b is a view similar to FIG. In of the construction of the roadway constructed in accordance with the invention and indicating the deformation of the cover sheet of the roadway with the inventive construction in the accompanying graph;

FIG. 2 is a transverse sectional view of a bridge roadway between two cross supports constructed in accordance with the invention;

FIG. 3 is a partial bottom plan view of the bridge roadway indicated in FIG. 2, partially in section;

FIG. 4 is a partial top plan view of a roadway indicated in FIG. 2; and

FIG. 5 is a partial longitudinal sectional view taken along the lines 5-5 of FIG. 2.

Referring to the drawings, in particular, the prior art bridge roadway construction is indicated in cross section in the upper portion of FIG. 1a. By comparing this construction with the inventive construction of the roadway which is indicated in FIG. 1b, it can be seen that the cover sheet will deform with the prior art construction in the manner indicated in FIG. 1a on the graph and the cover sheet will deform inthe manner indicated on 1b with the inventive construction.

As seen in FIGS. 2 to 5, the inventive roadway construction is formed between two main

longitudinal supports

1, 1 which support a cover sheet 2 of the orthotropic plate in the form of an upper trust or girth member. In accordance with the invention, below the cover sheet are provided a plurality of longitudinally extending support members or longitudinal ribs which are made of an opened box-shaped or trough-shaped profile as indicated. The opened tops of the ribs 3 are closed by the cover sheet 2 to which they are welded. The longitudinal ribs 3, as is known, have a high twisting stiffness. Cross supports 4 are provided at larger distances or spacings to which the ribs 3 are connected so as to be rotation fast.

In accordance with a feature of the construction of the invention between any two longitudinal ribs 3 there are welded cross bulk heads 5 having upper edges which are located at a distance from the cover sheet 2. As best seen in FIG. 5, all of the cross bulk heads 5- are located in a single plane. This plane is in the same plane as cross rib members which are welded to the upper side of the cover sheet 1, as indicated in FIGS. 3 and 4. The cross ribs 6 advantageously comprise a web-like fiat steel plate which is welded directly to the top surface of the cover 2. In some instances, the cross ribs 6 may be made in a zig-zag or curved foam if desired.

While a specific embodiment of the invention has been shown and described in detail to illustrate the application of the inventive principles, it will be understood that the invention may be embodied otherwise without departing from such principles.

What is claimed is:

1. A bridge roadway construction comprising a cover plate adapted to be supported on longitudinally extending main side supports, a plurality longitudinal ribs of substantially box-shaped cross section having lateral walls and with an opened top connected to the bottom of said cover plate and with the open top closed by said cover plate, a cross bulk head connected between the lateral walls of at least some of adjacent ones of said longitudinal ribs, the top of said bulk heads being spaced from said cover sheet, and an upright cross rib connected to the top of said cover sheet in the range of said cross bulk head.

2. A bridge roadway construction, according to claim 1, wherein said longitudinal ribs are of trapezoidal cross sectional configuration with said lateral walls thereof being arranged obliquely.

3. A bridge roadway construction, according to claim 1, wherein said upright cross rib comprises a steel plate web which is welded to said cover.

4. A bridge roadway construction, according to claim 1, including a relatively large cross support arranged below said cover plate and interconnecting said longitudinal ribs at spaced locations along the length of said cover plate.

5. A bridge roadway construction, according to claim 1, wherein said bulk head comprises a flat plate member disposed in an upright position and having its ends welded to respective lateral walls of said longitudinal ribs.

References Cited UNITED STATES PATENTS 2,221,309 11/1940 Gazelle 52618 X 2,316,569 4/1943 Dornier 52-618 2,970,553 2/1961 Allen 52-618 X 3,066,771 12/ 1962 Wolchuk 14-73 X 3,302,3 61 2/ 1967 Odheusden 1473 X NILE C. BYERS, JR., Primary Examiner.

US. Cl. X.R. 526 18