KR960001727B1 - Prestress combined beam for continuous bridge and its working - Google Patents

Abstract

The prestressed composite beam used for constructing a continuous beam bridge is designed to eliminate an expansion joint needed for the contentional prestressed composite beam bridge. The composite beam has the concrete portion formed under the I-beam to have a curve in the upside down shape of the deflection curve appearing at the outer beam of the continuous beam, the curve being semiparabola.

Description

Prestressed composite beam for continuous beam bridge and construction method of continuous beam bridge using same

1 is a structural system and a manufacturing process of the prestressed composite beam according to the present invention.

2 is a construction process chart of the two-span prestressed composite bridge according to the present invention.

3 is a structural system and moment diagram of a four span continuous beam.

4 is a manufacturing process diagram of the inner span beam in the three-stage prestressed continuous composite beam according to the present invention.

5 is a manufacturing process of the existing prestressed composite beam.

Prestressed composite beams, which have been widely known and constructed so far, are simple beams, and in the case of long principals, prestressed composite beams made of simple beams are continuously installed to expand the joints instead of integrating the connection between the beams and the beams. To be installed. These expansion joints are expensive, reduce driving comfort and require maintenance costs. In addition, it is the cause of the deterioration of the bridge due to the impact in the expansion joint portion and the leakage through the expansion joint portion during the passage of the vehicle. In the existing prestressed composite beam bridges, the problems of such expansion joints exist because they have not found a solution to the negative moment generated at the inner point by self weight and external force.

In simple beam bridges constructed of straight I-beams, only the tensile stress is generated in the lower flange of I-beams due to the bending moment generated when dead and live loads are applied. Conventional prestressed composite beams are fabricated with an I-beam to bend upward in the center, and then a preflexion load is applied downward within the elastic range of the material (see FIG. 5). In this state, the concrete that is advantageous for compressive stress is poured into the lower flange, and then the prestressed stress is introduced into the concrete as well as the pre-fraction load is removed. Reduction is achieved. However, in the case of the continuous beam bridge, unlike the case where the connection between the beam and the beam connection portion in the existing prestressed composite beam is treated with the expansion joint, the tensile stress is generated in the upper flange by the parent load due to the dead load and the live load. The tensile stress generated at this time cannot be reduced by the conventional manufacturing method of prestressed composite beam (see FIG. 5).

An object of the present invention is to provide a construction method that completely eliminates the problems of the expansion joint generated in the existing prestressed composite beam bridge by integrating the connection portion of the prestressed composite interpolation separated and manufactured in a short span without an expansion joint.

Another object of the present invention is to reduce the self-weight by reducing the maximum bending moment in the span by the self-weight and live load than the conventional pre-stressed composite beam by continuous processing of prestressed composite beams separated and manufactured in a short span In addition, the present invention provides a method of constructing straight and curved prestressed continuous composite bridges with longer spans and economical and safe cross sections. For example, in the case of two span continuous beams, the maximum bending moment of the sending section is reduced by 78% under uniform load and 23% under concentrated load than in the simple beam prestressed composite beam by the conventional method. In the case of continuous beams longer than 2 spans, the reduction rate is similar. In order to prove the rationality of the present invention, a virtually constructable two-span prestressed composite beam bridge was selected as a model, and a computer simulated experiment was carried out using ADINA, a general-purpose finite element software package program, according to the manufacturing method and construction procedure. Simulation). Detailed numerical data from the results of the virtual experiment are omitted in this manual, and the behavior of the deflection is shown in the accompanying drawings. Referring to the manufacturing and construction method of prestressed continuous composite beam using this drawing in detail as follows.

1 shows the structural system and fabrication process of prestressed composite beam, which is the span length (ℓ) corresponding to the first span of the bridge. (A) of FIG. 1 shows the state and point conditions of the I-shaped steel beams which are bent upward, that is, the point of movement and the fixed end.

Here, in Figure 1b of the bending curve shape, it is determined by equalizing the load size and position in the I-shaped steel beam structural system and acting the load direction in the opposite direction. In the bridge, the maximum bending moment is generated by 3/8 due to the dead weight which has more influence on the bending moment than the live load, and the two loads are each 1 / 8l at the position of 3 / 8ℓ.

The right end of the I-shaped beam has a sufficient clearance from the right end so that it can be easily leveled continuously with the second beam, and for the connection of the beam and the beam, and in some cases, the rigid reinforcement (Fig. 2 (a) The fixed end should be installed. In contrast to the conventional prestressed simple beam composite beams, the right end is treated as a nodal point. Another reason for treating the prestressed composite beams as a fixed point is that when the two prestressed composite beams are processed continuously, the part of the internal point caused by dead and live loads is This is to minimize the bending rate against the moment. That is, since the parent moment at the joint by the dead load and the live load causes the compressive stress on the lower flange of the prestressed composite beam, it is advantageous that the minimum prestress compressive force is introduced to the lower flange by the prestress at the parent moment generator. When the external force (p) for prestressing is applied, the right end of the I-beam can be fastened with the second I-beam and fastened with bolts for easy disassembly. The left end of Type 2 beams is to be extended and fixed at regular intervals as necessary.

FIG. 1b is a state in which a preflexion load (p) is applied to the curved I-beams in the elastic range, and (c) of FIG. 1 shows the prestress compressive stress on the lower flange of the I-beam under the pre-fraction load. The concrete is being poured for introduction. The loading position is such that the center of the two loads is 3/8 l from the left side of the I-shaped steel beam, in which the maximum bending moment due to dead load is applied in the continuous beam. In addition, the location of the two loads is advantageously spaced by 1/8 l from the center of the two loads, and the loading method is treated the same as the existing prestressed composite beam (see FIG. 5).

As the load p of FIG. 1d is removed, the compressive stress is introduced into the prestressed composite beam in which the concrete placed on the lower flange of the I-beam is introduced. As can be seen from FIG. 1 (d), when the two beams are integrated, the bending curvature is gentle from the right side of the beam, in which the negative moment is generated by dead weight, to 1/4 l. This means that the prestressed compressive stress of the lower flange of the prestressed composite beam is not very large in the section receiving the parent by dead and live loads.

FIG. 2 shows a procedure and a method for two-stage connection between short span prestressed composite beams manufactured according to the procedure in FIG. FIG. 2 (a) shows a state in which two composite beams in which prestress compressive stress is introduced to concrete placed on the I-shaped descent flange shown in FIG. The two beams are connected by bolting and welding, which are commonly used in steel structures. Here, the connecting portion may use a stiffner plate to secure the required rigidity.

2b is to introduce the prestressing compressive force by concrete casting and curing to the I-shaped steel upper flange of the section where two prestressed composite beams are installed and integrated on the piers, and the parent moment due to dead and live loads is generated. The center point is raised in the elastic range. (C) of FIG. 2 shows a state in which the top plate and the web concrete are placed in the section where the parent moment is generated by the dead load and the live load in the rising state of the central point.

At this time, the point rising operation can be easily performed using the hydraulic jack key. In this process, of course, concrete pouring of the diaphram must also be performed simultaneously.

FIG. 2d is a drawing in which two prestressed composite beams are returned to their original point in a state where the two prestressed composite beams are completely integrated by concrete casting and curing of the central connection (see FIG. 2 (c)). Concrete placed in the upper flange of the central part where the parent moment is generated by dead load and live load is introduced into the lower flange of the entire area by the rise of the center point at the same time as compressive stress is introduced to offset the tensile stress caused by the parent moment. Compressive stress is reduced and reduced with the original and partial recovery of the central point. In the case of partially lowering the raised center point (Fig. 2 (f), the continuous prestressed composite beam bridge may be a curved bridge having a central convex shape (Fig. 2 (g)).

Through this construction, two-span prestressed composite beams are fully integrated and prestressed stresses are introduced throughout the entire section which can greatly attenuate the stresses caused by the static and parental moments generated in continuous beams by dead and live loads. The object of the present invention is achieved.

2e shows the state where the concrete of the upper plate and the abdomen is poured in the continuous preservation section and the prestressed composite beam is almost horizontal due to its own weight. If only the partially rebounded central point is returned, the continuous prestressed composite bridge becomes a curved composite bridge that is beautiful in appearance and advantageous to bridges (see Figure 2 (g)).

3 shows the bridge structure system and bending moment between four spans. In the continuous beam structure system of more than 3 spans, the outer span is the same as the manufacturing process for introducing the prestressing of the continuous span between 2 spans (see Fig. 1). Another degree of fabrication is required.

4 shows the fabrication process of the inner beam in the prestressed continuous composite beam structure system of more than three spans. FIG. 4 (a) shows a structural system in which the beam center is bent upward and fixed at both ends so as to correspond to the positive moment generated from the inner beam by the dead load and the live load in the I-shaped continuous beam having more than three spans. The shape of the bending curve is obtained by applying the load in Fig. 4 (b) in the opposite way as in the case of the two span continuous beams. FIG. 4 (b) shows a state in which two concentrated loads are applied to the beam central part within the elastic limit, and the two loads at this time maintain the interval of 1 / 4L. The construction method for the subsequent fabrication and continuous processing is the same as in the case of two span prestressed continuous beam (see FIG. 2). The constraining force caused by shrinkage and expansion with respect to temperature, which can be generated by processing several spans in succession, is solved without difficulty by treating all points of the continuous beam as roller points except the first point.

Claims (3)

In the prestressed composite beam of continuous beam bridge in which the moment of one point A is "0" and the moment of the other point B becomes negative moment, the concrete is poured at the lower end of the I beam and the I beam Is an inverted deflection curve appearing on the outer beams under the uniform limit load of continuous beams. From 3/8 ℓ, the vertex of the upward curve is placed 3/8 ℓ from the point A along the length (L) of the I beam. Prestressed composite beam, characterized in that the up curve to point B is configured to be a parabola (see Figs. 1 (a) and 3). In the prestressed composite beam of continuous beam bridge in which the moment of one point (B) is the negative moment and the moment of the other point (B) is the negative beam, the concrete is poured at the lower end of the beam. The beam is a form in which the deflection curve appearing in the inner beam is reversed under the elastic limit load of the continuous beam. Prestressed composite beam, characterized in that the symmetry curve is configured to be a parabola (see FIGS. 3 and 4 (a)). Moment of point A of continuous beam M _A = 0, moment of point B, M _B = minor moment, point C of moment M _C parent,. … In the construction of a continuous beam bridge where the moment M _N = 0 of the final point N as a prestressed composite beam, prestressed composite beams I _AB and I _BC . (Or I _CD , I _DE ) at points B, C, D,... Integrate I _AB + I _BD (or I _BD + I _CD ,...) By integrating in position at points A, B, C,... The inner points B, C, D,... The upper flange of the I-beam is increased by the length of the parent moment caused by the uniformly distributed load on both the left and right sides of the raised point (see FIG. Pour and cure the abdominal and lateral beams of the concrete slab and the I beam (see Figure 2 (c)), and then fully or partially return the elevated points (see Figures 2 (d) and (f)). The prestressed compressive stress is introduced into the parent moment generation section, and both moment sections, in addition to the parent moment generation, are continuous beams characterized by finishing loads according to the construction order of the parent moment sections (see Figs. Construction method of continuous beam bridge using prestressed composite beam in bridge. Form of I _AB : I beam is an inverted deflection curve appearing on the outer beam under the elastic limiting load of continuous beams. With this coming up, the upward curve from 3/8 L to point B is parabolic (see Figures 1 (a) and 3). Form of I _BC : I beam is an inverted deflection curve appearing in the inner beam in the elastic limiting distribution load of continuous beams. This allows the two symmetry curves from the vertices to be parabolic (see Figures 4 (a) and 3).