JPS5883708A - Obliquely tensioned bridge - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention comprises at least one reinforced concrete tower fixed in a foundation, also made of reinforced concrete, extending from said tower on both sides and firmly connected to the tower against bending. The other part relates to a cable-stayed bridge constructed from roadway girders that are relatively flexible against crushing.

The roadway girder is supported by diagonal cables extending in several parallel vertical planes.

The essence of the basic idea behind classical cable-stayed bridges is as follows. In most cases, the roadway slab and the stiffening girder forming a single unit are suspended from the tower by means of diagonal cables. The horizontal component of the cable force is then introduced into the stiffening girder as a compressive force, while the vertical component of the cable force significantly offsets the self-weight of the stiffening girder as well as the roadway board. The cable elongation is adjusted by prestressing.

Longitudinal bending moments are experienced by the stiffening girder through one-sided traffic loads, especially when both towers are bent in the same direction by half loads in the side and center spans. To get an overview of the effects of these unilateral loads, the unilateral loads are decomposed into two load groups. In this case, it is assumed that the first load group is distributed uniformly and symmetrically over both central spans and the two side spans, and the second load group is distributed asymmetrically. The first group of loads loads the center of the tower, and the second one bends the tower to one side.

In the case of a classical cable-stayed bridge, the first load group is supported by the tower and the second load group is the stiffening girder.

The stiffening girder must be measured as the length of the side span for unloaded loading or half the length of the center span for half traffic loads. Considering the deflection limit, the height of the stiffening girder will be at least 17100 mm above the center span. The structural height is relatively high, and therefore it is very rigid and, especially when made of reinforced concrete, is extremely heavy.

Compared to cable-stayed bridges made of steel, cable-stayed bridges in which the towers and stiffening girders are made of reinforced concrete have the advantage that the compression components are of low cost despite their large weight. Costs can be particularly low if it is possible to reduce the weight of the stiffening girder.

In such a relationship, only relatively flat dense reinforced concrete should be used as the stiffening girder [1967
Volume 11, Der Baui
(pages 405-406) poorly thought out plans for cable-stayed bridges are known. In the case of cable-stayed bridges that extend over multiple spans, the tower is fixed in the foundation and must completely absorb the overturning moment due to traffic loads on one side. Only a few central spans are described for the bridge. The cable-stayed cables, which are placed on either side of the vertical bridge longitudinal center plane and at a slight distance from this plane, are constructed from steel bars placed in a single copper box. Cement mortar is poured into the inner space of the box.

It is also known that, in order to improve the fatigue strength of the anchorage of tension members in concrete structures, such as the cable-stayed cables of cable-stayed bridges, which can withstand large loads, it is also known that the tension members are commonly placed in a cladding. It is being This cladding extends into the concrete structure and is formed of a metal jacket, at least where it enters the concrete structure, which is tensioned after tensioning by injected cement mortar or the like. In addition to being connected to members, it is also connected to concrete structural parts (
Federal Republic of Germany Patent No. 2114863).

The problem underlying the invention is to create an advantageous configuration of the side spans in a statically and economically identical manner in a cable-stayed bridge of the embodiment described at the outset, in which the carriageway girders are placed on the abutments. The purpose is to prevent deformation caused by traffic loads on one side due to this placement.

This problem is solved by the present invention as follows.

That is, in a cable-stayed bridge consisting of a side diameter open area and half of the center span or another side span, in which the roadway girder is placed so as to slide horizontally on the abutment, the tower is placed on the abutment so that it can slide horizontally. The tower is formed so that the bending moment can be borne by replacing the vertical load in the cross section of the tower with the resultant force, and both ends of the roadway girder are connected through the tip of the tower. This problem is solved by constructing a cable-stayed cable with extra cable-stayed cable reinforcement to absorb the remaining part of the traffic load.

Cable-stayed cables are each constructed from a number of steel bars with a particularly moderate yield point. These steel bars are arranged in a single steel pipe and are joined to the other steel pipe by injecting a hardening material, such as cement mortar, into the spaces of the steel pipe that do not contain the steel bars.

Advantageously, the roadway girder is constructed as a multi-chamber hollow box of comparatively low height without crossbeams according to the Vielendael system, the tensile members of which are advantageously pretensioned.

The basic idea of this invention is as follows. In other words, in the structure of a reinforced concrete tower fixed in the foundation and strong against bending, most of the traffic load on one side can be supported by the cantilever overhang, and a small portion of this load is placed at the end of the roadway girder. This means that the tower must be supported by the tower foundation through the tip of the tower by cable-stayed cables. This allows the system to carry most of this cantilever moment, about %, rather than being fully or poorly supported on the stiffening girder as in the case of classical cable-stayed bridges. A small portion of the tower would extend out from the tower and be supported by a tower foundation with reinforced cables.

These cable-stayed cables are routed through the center span joint cloth through the apex of the tower.

The special construction of the steel rod cable and the attached steel tubes prevents anchorage fatigue, which is a problem with free-suspension cables due to repeated sagging under the repeated bridge loads. In addition to the advantage of improved strength, there is also the added benefit of smoothing the transfer of cantilever moments from traffic loads on one side from the roadway girder to the tower.

Roadway girders constructed according to the Vielendael system are suitable in the special aspect of smoothing out the ups and downs of the cantilever ends due to tower bending and cable stretching by means of elastic ribs. The height of this roadway girder is determined at the edges by cable anchorage. This height cannot fall below a minimum limit. The upper side is determined by the cross slope of the roadway board, and the lower side is designed particularly flat in order to obtain the highest possible resistance moment relative to the bending stiffness.

The hollow box itself is divided into many chambers, and the vertical ribs of said chambers, between the plates provided on the upper and lower sides of the hollow box, are very low. This allows the vertical members of the Vielendael system, which act as rigid frames, to be constructed as wide as is necessary to absorb the shear of the rigid frame without introducing too much weight. Pre-tensioning of the tension members in this system helps reduce avoidable secondary stresses.

The main purpose of the Vielendael system is the elimination of the crossbeams that are customary in such roadway girders. The weight of this crossbeam adds a traffic-like load to the entire structure of similar height. This allows the entire concrete of the roadway girder to be used for longitudinal force transmission, resulting in significant cost savings. Another advantage arises with the reduction in the height of the roadway girder due to the avoidance of acting wind forces and the possibility of placing the height of the roadway surface at a lower level, thereby saving costs on overland bridges. The configuration of the roadway girder according to the Vielendael system also makes it possible to simplify and accelerate the construction of bridges in block free-standing structures, which makes it possible to apply very advantageous repeating methods and saves costs. You will save even more.

The figures showing examples will be explained in more detail.

The basic structure of a cable-stayed bridge is shown in side view in Figure 1. Towers 2 and 3 protrude from the water surface 1 and are fixed in foundation bodies 4 and 5. The roadway girder 6 is suspended on diagonal cables 7,7', which are arranged on two lateral support planes 8 (FIG. 4). The diagonal cables 7,7' are fastened to the towers 2 and 3 on the one hand and to the road girder 6 on the other hand.

The cable-stayed bridge according to FIG. 1 has a large central span I and two short side spans. The carriageways 6 of these two bridge sections are connected to each other by a shear hinge in the bridge center 8 and are mounted longitudinally movably on the abutments 10 at their outer ends 9.

The cable-stayed cable 7 is made up of a number of steel bars 11, which have a particularly moderate yield point. The steel rod is arranged in one steel pipe 12. The steel bar 11 is in particular hot-rolled and provided with ribs forming a helical thread. A correspondingly formed fixing body or coupling body can be screwed onto the helical screw. The hollow space within the steel pipe 12 that is not occupied by the steel rod 11 is filled with cementum rutal 13. The end 9 of the roadway girder B is connected to the middle area 8 at the center of the bridge.
The diagonal cable 7' connected thereto is constructed with corresponding reinforcement.

The fixing portion of the diagonal cable 7 in the roadway construction 6 is shown in FIG. The roadway 6 has an enlarged portion 14 on the upper side in the region of this fixing portion, and also extends to the lower side by the length of the expansion. Its length is sufficient to transfer the traffic loads absorbed by the steel pipe to the concrete of the roadway girder B by adhesion. An anchoring portion 16 for the steel rod 11 is provided in the expanded portion 15 on the lower side of the roadway.

Figure 4 shows the cross section of the roadway girder O. The roadway is constructed as a ramen with many closed vertical members. In this rigid frame, the road board 17 forms an upper horizontal member of the rigid frame, the floor plate 1B forms a lower horizontal member of the rigid frame, and the vertical web 19 forms a vertical member of the rigid frame. This static system is also called the Vierendel girder.

The shape of the roof in cross section is due to the cross-slope of the roadway pavement to drain away surface water.

FIG. 5 shows a portion of FIG. 4 in enlarged size.

For example, the floorboard 18 of the driveway 6 is the tensile member of the Vierendel system and is prestressed by tendons 20 and 21. The tension members 20, 21 are fixed in stages depending on the magnitude of the bending moment. Therefore, the tendon wire 20 is connected to the anchoring section 20 in the outer region.
A tension wire 21 is installed near the hanging cliff plane 24.
The fixing portion 25 is provided in the area of the outer rigid frame vertical member 19'.

[Brief explanation of the drawing]

Fig. 1 is a side view of the cable-stayed bridge of the present invention, Fig. 2 is an enlarged dimensional cross-sectional view of the cable-stayed cable, Fig. 3 is a detailed view of the anchoring part of the cable-stayed cable for roadway construction, and Fig. 4 is FIG. 5 is an enlarged dimensional view of a partial cross section of the roadway. Symbols in the figure ■...Central span, ■...Side span, 3...Tower, 6...Roadway construction, 7, 7'...Cable-stayed cable, 8,
9... End of roadway, 10... Bridge abutment.

Claims (1)

[Scope of Claims] 1) At least one reinforced concrete tower fixed in the foundation; also made of reinforced concrete, extending from the tower on both sides and firmly connected to the tower against bending; In cable-stayed bridges, which are supported by cable-stayed cables extending in several parallel vertical planes, the carriageway consists of a carriageway which is relatively flexible in other parts, and which is supported by cable-stayed cables extending in several parallel vertical planes. (6) is placed so as to slide horizontally on the abutment (10).
In a cable-stayed bridge consisting of I) and half of the central span (1) or another side span ω), the tower (5) The tower is formed so that the tower can be borne by replacing the resultant force consisting of the vertical loads of , and both ends (8
, 9) with cable-stayed cables (7) connected through the tip of the tower (3), reinforced with extra cable-stayed cables (7) to absorb the remaining part of the traffic load. A cable-stayed bridge characterized in that: 2) the cable-stayed cables (7, 7') are composed of a number of steel bars (11) having a particularly medium yield point; The steel rod (11) is placed in the steel pipe (12) and placed in the space of the steel pipe (12) not occupied by the steel rod (11) by injection of a material that hardens after tensioning, for example cement mortar (13). The cable-stayed bridge according to claim 1), which is connected to this steel pipe. 3) Cable-stayed bridge according to claim 1) or 2), wherein the carriageway (6) is constructed as a multi-chamber hollow box of comparatively low height without crossbeams according to the Vierendel system. 4) The cable-stayed bridge according to claim 3), wherein the tension members of the Vielendael system are prestressed.