KR100334635B1 - Segmental bulb girder and construction method for long span bridge - Google Patents

Abstract

The present invention relates to a segmental bulb tee girder and a construction method for long span bridges.

According to the present invention, the inclination of the haunting portion 3 'of the upper flange 3 is 1/5 (10 cm) in the long span bridge girder as shown in FIGS. 2 and 7 and the haunch portion of the lower flange 4 (4 ') The slope is 1 / 1.75 (20cm), and the girder is separated into the end segment (10) and the center segment (11) at the girder production site, and then the center and end segments are mounted at the bridge construction site and between the segments. There is epoxy bonding, and the angle is combined at the top, and the tension material is jacked after completely installing the upper part with one girder.

Description

Segmental bulb tee girder and construction method for long span bridge

The present invention relates to a segmental bulb tee girder and a construction method suitable for long span bridges.

Since the 1980s-In Korea, where the need for long-span bridges is rapidly increasing due to changes in the construction environment such as the opening of the construction market and the demands of the times, the PSC beam bridges, which are conventionally designed and constructed, are limited to 30m or less. More than that, it is being constructed as a steel bridge or PSC box bridge.

Conventionally, the construction of the P.S.I-shaped bridges in Korea is limited to a distance of 30m or less due to transportation, construction and manufacturing characteristics, and when the distance is 40 to 60m, steel plate bridge, steel box bridge and free Most of the construction is done with the Pre-Flex bridge, and if it requires more space, it is constructed with the PSC Box type bridge. However, in the case of steel bridges, the reliability of the quality can be secured at the time of construction, but the maintenance cost is high after construction, and the pre-flex bridges have a relatively small cross section and excellent aesthetics, but the construction cost is excessive. In the case of PSC box type bridges, it is difficult to design and construct a medium-span bridge below a certain distance, and its efficiency is relatively inferior in terms of workability and economy compared to steel box bridges. .

Therefore, it is required to develop a new bridge type that overcomes the disadvantages of the existing bridge types and has both constructability and economy.

The present invention changes the cross-sectional characteristics of the existing PS-eye girder and can be applied to long spans of 40m or more by dividing into segments, so that the design can be compared to steel bridges or PSC box bridges of the same area. We have developed the PSC Bulb-Tee girder, which is excellent in simplicity, constructability, and economic efficiency, to provide design and construction methods based on the development of advanced bridges, reduce construction costs, and increase the national competitiveness of the domestic construction industry. The purpose is to sleep.

The present invention for realizing the above object is to form a unique cross-sectional shape by changing only the height of the girder and the number of steel wires without changing the overall shape of the girder cross section as much as possible to provide a standard cross section suitable for the bridge. Considering construction problems, the segment method was introduced.

1 is a girder cross-sectional view of a 40m bridge according to the present invention,

2 is a standard cross-sectional view for a 40m bridge according to the present invention,

3 is a girder cross-sectional view of a bridge for 50 m according to the present invention,

Figure 4 is a standard cross-sectional view for a 50m bridge according to the present invention,

5 is a girder cross-sectional view of a 60m bridge in accordance with the present invention;

Figure 6 is a standard cross-sectional view for a 60m bridge in accordance with the present invention,

7 is a sectional view of the girder connection according to the present invention,

8 is a correlation chart of the height and the effective coefficient of the member according to the present invention;

9 is an optimum construction unit price comparison chart,

10 is a flow chart of the bending design program of the girder according to the present invention.

<Description of the code | symbol about the principal part of drawing>

1-girder 2-abdomen

3-Upper flange 3 '-Hunting section

4-Lower Flange 4 '-Hunt

10-end segment 11-center segment

12-Temporary Pier 13-Epoxy Junction

14-slab 15-angle

16-temporary tension

In the present invention, in order to provide a standard section suitable for the long span bridge, the overall shape of the girder cross section is proposed as long as the height of the girder and the number of steel wires as variables, and the standard section suitable for the target span is also proposed. In the case of the PS girder, since the weight of each girder exceeds 100 tons (ton), it is also difficult to secure and transport the production space, and as the girder length and height increase, problems may occur in the stability of the girder as it increases. Proposed a construction method using the segment method.

The present invention will be described in detail with reference to the accompanying drawings.

The cross section determination of the girder (1) has a significant influence not only on the structural efficiency on the entire cross section of the girder but also on the manufacturing cost of the girder to be used. The larger the cross section, the greater the dead weight of the member itself due to the weight of the girder, which results in more tension, which increases the range of compressive stress of the concrete. In addition, the amount of concrete per unit volume increases and the amount of rebar increases according to the determined length. As the design condition of the present invention, a bridge having a span length of 40m with a two-lane bridge width (12.145m) was used as the basic model, and the concrete strength of the girder was 550kg / cm 2, and the strength of the upper slab was 270kg / cm 2. The same applies.

In the girder 1 consisting of the upper flange 3 and the lower flange 4 around the abdomen 2, the width of the wide upper flange 3 can play a large role in reducing the construction cost of the cast-in-place slab. have. This is because the wider the upper flange, the greater the rigidity, thereby reducing the slab thickness, and the reduction of the slab area can result in additional construction cost savings such as formwork costs. The width of the upper flange (3) is suitable for 120cm and the thickness of the upper flange (3) is suitable for the transport of the girder to the construction site and to prevent damage to the girder or local buckling in the actual construction stage. . The haunting inclination of the haunting portion 3 'of the upper flange 3 also applied 1/5 (= 10 cm) to reduce the weight of the girder and resist local buckling and shear forces acting on the flange.

The lower flange 4 can increase the width of the same cross-sectional area while reducing the thickness can structurally increase the efficiency of the cross section.

However, the distance from the duct to the bottom of the girder cannot be reduced below a certain level because the duct diameter, rebar placement, and concrete cover must be taken into account. In order to resist the stress, the lower flange should be 90cm wide and 25cm thick.

The inclination of the lower flange (4) haunting portion (4 ') is inclined by considering the increase of steel wire and the duct diameter due to the increase of the span, and the compaction in the concrete casting process during the girder fabrication. 1.75 (= 20 cm) is suitable.

Considering domestic production conditions, it is difficult to produce the cross-section with curvature. Therefore, a double haunt with a width and height of 5cm is placed under the haunch of the upper flange, so as to display a soft image if possible. It was.

Determination of the height and abdominal width of the girder (1) is dominated by the overall type according to the bridge span, the strength of the concrete used to make the girder, and the required steel dose depending on the unit weight of the reinforced concrete. In post-tension type PS girder, the increase in required steel wire length and length increases the number and diameter of ducts, which increases the height of the girder and the width of the abdomen.

The width of the girder's abdominal width can be determined according to the diameter of the duct used in each section, taking into account the length of the vertical reinforcement (D19) and the reinforcement reinforcement (D16) in the abdomen and 4 cm of concrete cover. However, it is efficient in design and construction to have the same width for all sections rather than different abdominal widths depending on the section, so it is assumed that a duct with an internal diameter of 12.3 cm can be used for up to 37 steel wires in one tuck. The abdominal width of 26 cm was determined for the trunk.

The height of the girder can also be determined by considering the minimum distance from adjacent anchorages and the number of ducts used, depending on the length and type of duct used.

If the total number of ducts is equal to 4 for each section and the diameter of the ducts can accommodate up to 88, 124, and 148 total steel wires, the minimum height of the girder is 210cm, 245cm, 265cm. However, considering the reinforcement of the reinforcing bars in the anchorage, the height was determined to be 240cm for the 40m section, 260cm for the 50m section, and 280cm for the 60m section.

The design data for each section is shown in the following table.

Bulb-Tee girders with lengths of 40, 50, and 60 m, respectively, are difficult to transport from the fabrication site to the construction site, and problems may occur in the upper construction of the bridge due to the heavy girder weight even during the upper construction. . Since the bulb tee girder of the present invention uses high-strength concrete to increase the period, and is designed to be placed in a large amount of wire in the cross-section, strict quality control is essential when manufacturing the girder. Therefore, a lot of difficulties come to the bridge construction site. In addition, in the case of mountainous terrain or rivers with poor site conditions, it is almost impossible to manufacture the site casting girders in the vicinity of the construction site.

In the present invention, a method of constructing a spliced girder is used. A spliced girder is a method of joining several segments in the field and constructing them in a single section. It can be referred to as a method and the construction process will be described schematically with reference to FIG.

(1) An end segment 10 and a center segment 11 of about 15m to 20m length are produced at the girder site and transported to the construction site.

(2) We construct pier at bridge construction site and establish temporary pier 12 at the same time.

(3) It moves from the outside to the bridge center part, and installs each segment, and forms the junction part 13 by the installation of the angle 15 and epoxy bonding between segments.

(4) The temporary tensioning material (16) is jacked after one girder is completely hypothesized .

(5) The other girders are constructed in sequence in the same order as above.

(6) After finishing the construction of girders, remove the temporary piers after constructing the upper slab, asphalt pavement and attached facilities.

The angle 15 is installed by welding the upper end of the connecting segment of the end segment 10 and the center segment 11, and considering the anti-slip and transfer resistance performance between the end segment 10 and the center segment (11). As shown in the figure, a shear key of about 60 ° angle is constructed.

Temporary tensioning material 16 is applied in a conventional manner on both sides of the abdomen to secure epoxy bonding between the segments.

FIG. 10 shows a design program for designing a PS girder bridge as a priority study in order to propose a cross section of a PS girder suitable for a domestic reality, and the developed program enables a designer to perform basic design by simply inputting a variable. have.

As a next step, using the developed program, the influence of each design variable on the presented sections was analyzed, and the correlation of each variable on the bridge design was analyzed. Through these basic studies, we proposed an independent cross section that can optimize the influence of each design variable and fit the domestic reality and minimize cross sections and design changes according to the interval.

In the present invention, in order to maximize the convenience of design and construction, the target interval of the bridge is set to 40m, 50m and 60m, which is considered to be a high economic feasibility and construction possibility considering the current construction environment.

The following is a list of preconditions applied in the present invention to develop a girder section for each section.

(1) Design spaces are to be 40, 50 and 60m.

(2) The section specifications of the upper and lower flanges for each design section are to be the same as far as possible.

(3) Based on the bridge design for 12.15m width of the two-lane bridge, which is the most constructed in Korea.

(4) The construction plan suitable for long term bridge construction is suggested.

The program was developed using a Spreadsheet commercial program to determine the girder cross section that can be used for long span bridges. The input parameters of the program were the overall shape of the bridge and the materials used, such as the girder cross-sectional shape, the design span of the bridge, the number of bridges and girders, the girder spacing, the thickness of the upper slab, and the specification of the barrier wall. The arrangement of the steel wire used as tensioning material was calculated by inputting the position of tensioning material at the end of the girder and the center of the middle of the girders to be calculated as a two-dimensional parabola, and the loss of tensioning material was calculated based on the result. The design load is based on the first-class bridge, and the elastic modulus, loss loss of the tension material, and the load during the active load are based on the road bridge specifications currently in use in Korea.

Cross section efficiency

The best method for selecting the optimal section in long span PSI bridges is to reduce the bending stress that has the greatest influence on the determination of section, and the design factors affecting the bending stress are dead weight and section coefficient. These variables are largely governed by the shape of the cross-section, and even if the cross-sectional area is the same, it is possible to increase the efficiency of the member by reducing the bending stress of the member when the cross-sectional coefficient is relatively large. Therefore, the maximum goal in the design of the member cross section is to design the largest cross section coefficient in the limited cross section.

Until now, most studies have examined the efficiency of the cross section through qualitative comparison of the cross section modulus with respect to the cross-sectional area. However, the effectiveness of the cross section modulus using Guyon's effective coefficient (ρ) has been found. It was shown to be the most efficient (see Figure 8).

here = Radius of rotation of section =

y _t , y _b = distance from the city center to the top and bottom cross sections, respectively

I = cross section second moment

A = cross sectional area

The advantages of the existing PSI bridges include not only ease of construction but also relatively low construction cost and maintenance cost compared to other structural types.However, when the distance is over 40m, the construction cost of the PSI bridge is designed. It is reported that it is relatively economical and that it is relatively inferior to that of steel bridge construction.

However, the development of the bulb tea girder resulted in the construction and economic feasibility review of steel bridges and P.S. bridges, resulting in a 30% reduction in overall construction costs.

In the case of the abdomen width, when the same section is designed in comparison with AASHTO, the bulb tea girder is considered to have excellent economic efficiency and superior performance in section efficiency compared to other bridge types (Fig. 9). Reference.)

In the present invention, it is easy to manufacture and transport girders having a long span of 40 to 60m, and improve the economics and workability due to the replacement of the steel bridge by providing a long span Pulse bulge girder.

Claims (2)

In the long span bridge girder, the width of the upper flange 3 is 120 cm, the thickness is 15 cm, the inclination of the haunches 3 'is 1/5 (10 cm), and the height of the web 2 is 170 cm to 210 cm, The thickness is 26cm, the width of the lower flange 4 is 90cm, the thickness is 25cm, the inclination of the haunting portion 4 'is 1 / 1.75 (20cm), and the end segment 10 and the center segment 11 are separated. Segmental bulb tee girder for 40m to 60m bridges that can be combined and constructed. In long span bridge girder, In the girder manufacturing site, the end segment 10 and the center segment 11 are manufactured to have a length of 15 m to 30 m, and the pier and temporary pier 12 are installed at the bridge construction site, and 60 ° between the segments 10 and 11 is installed. Introduce an angled shear key, introduce a conventional temporary tensioning member 16 to secure this joint with epoxy bonding, join an angle 15 to the top, and tension the tensioner after one girder is fully laid on top. Segmental bulb tee girder construction method for the long span bridge, characterized in that for jacking.