KR20020021550A - Method for designing and constructing high strength concrete construction for PSC beam bridge - Google Patents

Abstract

PURPOSE: A designing/manufacturing method of a high strength concrete structure for a PSC beam bridge is provided to reduce the number of necessary piers and girders by enlarging the length of span or expanding the distance between girders. CONSTITUTION: For design of mix proportion to make a high strength concrete for a PSC beam have design compressive strength of 600-700 kilogram per square meter, the high strength concrete structure for a PSC beam is manufactured by mixing high-early strength portland cement of 470-550 kilogram per cubic meter, water of 169 kilogram per cubic meter, fine aggregate of 586-627 kilogram per cubic meter, coarse aggregate of 1062-1088 kilogram per cubic meter, a 0.002-percent air entraining agent of the quantity of cement, and a 1.5-percent natural assimilating agent of the quantity of cement.

Description

Structure of high strength concrete for PS beam bridge and its manufacturing method {Method for designing and constructing high strength concrete construction for PSC beam bridge}

The present invention relates to a structure of a high-strength concrete for PSC beams (PSC BEAM) bridges and a design manufacturing method thereof, and more particularly to a PSC beam to which high-strength concrete (design compressive strength 600 ~ 700kg / cm ² ) is applied The design and fabrication method of the bridge and the manufacture of high strength concrete for PSC BEAM, which ensures workability and durability, apply high strength concrete and increase the allowable tensile stress and compressive stress according to the increase of compressive strength. By developing a high strength PSC BEAM bridge with 30m and 40m span within the range that does not increase the girder height of the PSC BEAM bridge used in the By designing high-strength concrete for PSC beams used in bridges that can reduce the number of piers or reduce the number of girders required Sum to a method and the structure.

And the cross section of the standard design pieseusi beam (BEAM PSC) bridge, which is currently applied in many bridge construction method to the concrete, the girder design compressive strength applied to 400kg / cm ² of the girder spacing 2.5m or less, the span length 25m, 30m In girder cross section is presented, and in the above section, it is constructed as steel bridge, PSC box bridge or preprex bridge (FIG. 1).

However, these conventional bridges are not only costly in construction, but also in the case of steel bridges, there is a disadvantage of high maintenance costs. Since the construction is also relatively inferior, a large portion of the small and medium bridges is not provided in the absence of girder height spatial constraints. Is being constructed as a bridge in the form of a PS beam.

The research on the development of high-strength concrete materials has been steadily promoted in domestic academia and related research institutes for the past 10 years, but until now, the results of direct field construction on civil structures have been insufficient for its practical use.

Recently, due to the rapid development of admixtures, strength expression of 600 ~ 700kg / cm ² can be obtained by quality control of 400 ~ 450kg / cm ² level applied to the existing PSC box bridge. It is required to identify the composite design of high strength concrete considering its workability and to investigate its mechanical properties and properties.

Therefore, the present invention is to solve the above problems, the object of the present invention is to increase the concrete strength in the PSC beam beams (PSC BEAM) bridge is widely applied in the current range of 25m ~ 30m mainly bridge bridge construction method By using the advantages of the material, we can derive the effect of increasing the girder spacing or increasing the length of the bridge than the existing PSC BEAM bridge to provide a new bridge construction method that is economical and secured, and at the same time to apply high strength concrete. The purpose of this study is to investigate the material development and its mechanical properties and to suggest the optimal formulation design that can be applied in the field.

Another object of the present invention is a compounding method by designing high strength concrete for PSC beams (PSC BEAM) used in bridges that can reduce the number of bridges or reduce the number of required girders by deriving the effect of increasing the length and girder spacing. And to provide the structure.

In order to achieve the above object, the present invention selects three types of cement and one type of cement as a suitable material for high-strength concrete, and conducts the optimum blending design for the required target design strength. The mechanical properties and durability were verified, and the optimum amount of delayed high performance AE water reducing agent derived through indoor and field tests was applied to the field to improve the slump over time for the practical use of the field. By increasing the transportable time up to 90 minutes, the field applicability has been greatly improved, and the optimum steam suitable for high strength concrete to solve the problem of hydration heat cracking caused by the increase of the amount of unit cement, which has been pointed out as a problem in the application of high strength concrete. The curing technique is presented.

The high-strength concrete developed as described above is manufactured as an actual bridge test member, and sufficient structural stability and usability of the PSC BEAM bridge are secured through static load test, fatigue test, and long-term behavior test. It was.

1 is a cross-sectional view showing a conventional PSC beam (PSC BEAM) bridge,

FIG. 2 is a cross-sectional view of a bridge showing a structure in which the number of girders is reduced by a structure of a high-strength concrete for a PSC BEAM bridge and a design manufacturing method used in a bridge of a preferred embodiment of the present invention; FIG.

3 is a change in the design compressive strength and the interval between the girder height and the girder interval according to the present invention,

Figure 4 is a change in the girder height and pitch length and girder spacing according to the design compression strength according to the present invention,

Figure 5a, 5b is a girder cross-sectional view of the bridge length 30m and 40m in accordance with the present invention,

6 is a steam curing cycle diagram suitable for high-strength concrete according to the present invention,

7 is a design compressive strength for the age of each formulation according to the present invention,

8 is a dry shrinkage characteristic of each formulation according to the present invention,

9 is a creep characteristic of each formulation according to the present invention,

10 is a salt ion permeability characteristic of each formulation according to the present invention,

11 is a load-deflection curve comparison table of the experimental member and the computer simulation results through the large member structural experiment,

12 is a load-deflection curve diagram of a composite member having an interval length of 40 m.

Explanation of symbols on the main parts of the drawings

10: firewall 20: pavement

30: slab 40: girder

50: upper flange 60: abdomen

70: lower flange

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The mixing method according to the design of the high-strength concrete for PSC beams of the present invention is a high strength for PSS beams in which workability and durability are secured among manufacturing methods of PSC BEAM bridges corresponding to a span length of 30 m to 40 m. The design compressive strength of concrete 600 ~ 700kg / cm ^{2 In} order to make a high-strength concrete manufacturing method, there is a characteristic blended in the mixing ratio shown in Table 1.

As shown in FIG. 2, the distance between the girder is divided into a separation section and a non-separation section in the two-lane PSC beam beam. Thus, 2.1 m to 2.5 m are applied to each other. If the spacing of girders can be increased to 3.3m by applying concrete, it is possible to derive the economic advantage of reducing the number of girders by one or two by adjusting the spacing of girders equally without dividing the separated and non-separated sections. In particular, in the case of multi-span long bridges, construction cost savings are even greater.

3 and 4 show the structural analysis for each case after setting the design parameters (design compression strength, girder height, girder spacing, span length, etc.) to determine the optimum cross section of high strength PSC beam bridge. Figures show the final result.

As shown in the above figure, the rightward upward range is out of the allowable stress based on the boundary line in the diagonal direction. Therefore, in order to satisfy the design condition, all the design conditions have to be satisfied in the lower left range relative to the boundary line.

Referring to the preferred embodiment of the present invention, in order to satisfy the design conditions of the girder length 40m and girder spacing 3.3m on the graph of girder height (H) = 230cm in Figure 3, the design compression strength of the girder 600 kg / cm ² The height of the girder (H) must be greater than or equal to 185 cm in order to satisfy the design conditions of the length 40m and the girder spacing 2.5m on the graph of the design strength 600kg / cm ² of FIG. 4.

The upper flange 50 of the girder in the PSC BEAM bridge corresponding to the span length of 30m and 40m by applying the high-strength concrete (designed compressive strength 600 to 700kg / cm ² ) shown in FIGS. 5A and 5B. The width of 100cm, the thickness of 15cm, the height of the abdomen 60 was 125cm to 155cm, the thickness of 22cm, the width of the lower flange 70 was formed to have a width of 72cm, a thickness of 20cm.

Next, Table 1 below is a mixing design table of high-strength concrete that ensures workability so that the slump is 18 ± 3cm when cast in place. In order to secure sufficient workability to transport the transport time to the site within 90 minutes, an optimal amount of high performance water reducing agent was used, and in order to control the occurrence of cracks due to high hydration heat during steam curing operation, as shown in FIG. An improved steam curing technique was applied to limit the curing cycle and the maximum temperature to 45 ° C. In other words, after pretreatment is sufficient for about 2 hours to reflect the condensation characteristics of the concrete, it is necessary to adjust the rise of the temperature supplied to the concrete to 12.5 ℃ per hour to prevent the rapid hydration reaction, and at the maximum temperature of 45 ℃ A proposal was made for a duration of 12 hours.

7 is a graph showing the compressive strength by age for these formulations, the expressed values meet both the 28-day design compressive strength and the strength requirements at 14 days of prestress introduction (more than 80% of the 28-day design strength) Shows one result.

Figure 8 is a graph showing the amount of dry shrinkage for each formulation, the experimental results show that the amount of dry shrinkage decreases as the strength increases compared to the conventional 400kg / cm ² applied. This effect increases the rigidity of the member by minimizing the reduction of the amount of prestress.

Figure 9 is a graph showing the creep test results for each formulation, showing a small value compared to the creep coefficients presented in the current road bridge specification, and shows that the creep deformation due to the high strength is reduced.

10 is a graph showing the results of the salt ion penetration test that can determine the density of the concrete structure, which is a measure of the improvement of the durability of the concrete, and as the strength is increased compared to 400 kg / cm ² applied to the PSC beam (PSC BEAM). It shows a significant decrease in permeability.

11 is a comparison of the load-deflection curve of the center point obtained in the structural test and the load-deflection curve obtained in the structural analysis for the composite member produced by applying the high strength concrete according to the present invention. The results obtained from the structural test and the finite element analysis considering the nonlinearity are almost similar.

12 is a load-deflection curve through nonlinear finite element analysis for a composite member of a high strength PSC BEAM bridge having a 40m span length.

For example, while the invention has been shown and described with respect to certain preferred embodiments, the invention may be variously modified and modified without departing from the spirit or the scope of the invention as set forth in the claims below. It will be readily apparent to one of ordinary skill in the art.

As described above, by using the high-strength concrete according to the present invention by using the effect of increasing the allowable tensile stress and the compressive stress in accordance with the strength of the girder concrete to increase the length of the space than the conventional PSC beam beam (PSC BEAM) bridge or By widening the girder spacing, the reduction effect of the number of piers and the reduction of the number of girders can be derived, which can be applied as a more economic bridge construction method. In addition, the durability is improved compared to the existing PSC BEAM bridge, which increases the service life of the structure and reduces post-maintenance costs. There are various effects such as resistance to cracking, increase of water permeability, drying shrinkage, reduction of volume change such as creep, and loss of prestress due to increase of elastic modulus. In addition, to overcome the constraints of the lower space of the girders on the lower side of the girders, which have been pointed out as a disadvantage of the PSC BEAM bridge, if the girder spacing of 2.5m, which was applied to the existing bridge structure, was maintained as it is, the space length would be applied. In the case of 40m, the height of the girder can be reduced by 50cm from 2.35m to 1.85m, and the replacement effect of the preprex bridge with a relatively high construction cost becomes possible. In particular, by presenting the optimum "vapor curing temperature cycle" suitable for the design strength through a number of experiments to prevent the problem of cracking caused by the heat of hydration that can be generated during the manufacture of high-intensity PS beams, while at the same time suitable for the concrete Since it has the effect of implementing the strength expression is a very useful invention in the bridge construction industry.

Claims (4)

Design strength of high strength concrete for PS beam with secure workability and durability of PSC BEAM bridge in the range of 30m to 40m span 600 ~ 700kg / cm ² To Three kinds of cement 470~550kg / m ^3, water 169kg / m ^3, fine aggregates 586~627kg / m ^3, coarse aggregates 1062~1088kg / m ^3, the air entraining agent in the largest dimension is 20mm 0.002% of the amount of cement, superplasticizer Design and manufacturing method of the structure of high-strength concrete for PSC beams (PSC BEAM) bridge, characterized in that the mixing ratio of 1.5% of the amount of cement. Design strength of high strength concrete for PS beam with secure workability and durability of PSC BEAM bridge in the range of 30m to 40m span 600 ~ 700kg / cm ² To Class 1 ordinary cement 533-650kg / m ³ , fly ash 28-33kg / m ³ , water 157-167kg / m ³ , fine aggregate 501-552kg / m ³ , coarse aggregate 991-1049 kg / m ³ , Designing and manufacturing method of high strength concrete structure for PSC beam beams, characterized in that the air entrainer is 0.1% compared to the amount of cement, high fluidizing agent is blended at a mixing ratio of 1.7 to 2.0% relative to the amount of cement. According to claim 1 or 2, wherein the curing method of the blended high-strength concrete after the pretreatment for two hours to reflect the condensation characteristics of the concrete, by adjusting the increase in the temperature supplied to the concrete to 12.5 ℃ per hour A method of designing and manufacturing a high-strength concrete structure for a PSC beam beam, characterized by preventing rapid hydration and steam curing at a maximum temperature of 45 ° C. for 12 hours. In the PSC BEAM bridge, which covers the length range of 30m and 40m by applying high strength concrete (designed compressive strength 600 ~ 700kg / cm ² ), The width of the upper flange 50 is 100cm, the thickness is 15cm, the height of the abdomen 60 is 125cm to 155cm, the thickness is 22cm, the width of the lower flange 70 is 72cm, the thickness is 20cm High strength concrete structure for PSC BEAM bridge.