KR100274142B1 - Introducing method of partial prestress of preplex composite beem by divisional method - Google Patents

Abstract

The present invention provides partial prestress of a preflex composite beam by the splitting method that can improve workability, shorten the air, and simplify the work in introducing partial prestresses to the beam member connection portions of the preflex composite beam manufactured by the split method. In order to provide an introduction method, after the beam member split type preflex beam is assembled into a high-power bowl, the upper layer beam member split type preflex beam is installed, and an oil jack is installed on the bottom of the upper beam to apply prestress to each joint. After the force is applied, the concrete placed on the lower flange of the joint is cured and the hydraulic pressure is released to introduce partial prestress.

Description

Partial prestress introduction method of preflex composite beam by split method

The present invention is the beam member of the preflex composite beam manufactured by the split method to install and assemble the long beams in the city, such as the city area and the complex of the field complex, easy transportation and effective for shortening the air and construction cost The present invention relates to a method of introducing a partial prestress of a preflex composite beam by a splitting method which improves workability, shortens air, and simplifies work in introducing partial prestresses into the inter-connection.

Preflex composite beam is a composite beam that mixes steel beams and prestressed concrete beams by using a kind of prestressing method in which high-strength concrete is placed on the lower flange of steel beams and cured by introducing compressive prestress to concrete. .

Preflex composite beams have been widely applied to various structures requiring long spans in architectural structures, bridges, Qingdao bridges, overpasses, etc.Preflex composite beams are more economical than other beam structures and have great advantages in terms of space utilization. Preference is expected to continue in the future.

Preplex composite beams, which have been known so far, are brought into steel construction beams and used to make various types of equipment to preflection. In manufacturing and constructing such a preflex composite beam, above all, consideration should be given to securing a large working space for installing large-scale pre-fraction equipment near the construction site, as well as providing a long-span cheolgolbo and safe and convenient transportation. In consideration of this point, the preflex composite beam is manufactured by dividing the preplex composite beam into two or more pieces in a factory or a field and reassembling it during construction.

The preflex composite beam by the split method introduces partial prestress into the joint concrete that is constructed at the joint of the lower flange at the joint of each beam member during construction. As a method of introducing such partial prestress, the cable flange (in-cable method) is a method of introducing a compressive force by using a PC steel bar or steel wire to the lower flange concrete, a PC steel bar or steel wire installed on the top of the preflex composite beam block There is an out-cable method and a counter weight method that induce bending flexural force in the lower part of the joint, and then remove the tension after concrete is cast and hardened.

As the in-cable method is introduced in Japanese Patent Laid-Open No. 58-4004, a stress is introduced into the lower flange concrete except for the joint of each segment in the factory, and the portion where the concrete is poured is constrained by the lower flange tube and the lower part of the joint Flanged concrete places steel concrete beams after connecting steel beams in the field, and introduces stress into PC bars near the neutral axis of the composite section.

The out-cable method is a method in which the anchoring end is installed on the upper flange of steel cheolgolbo, and the concrete for the joint is cast and hardened while eccentric bending is applied with the PC steel wire, and then the flexural prestress is introduced into the lower flange concrete by loosening the PC steel wire. Since the prestressing operation of the silver joint is performed on the upper bottom plate, the workability is good and the type of the joint is forged and shortened in the air.

The counterweight method is a method of placing pre-stressed prestresses in the lower flange concrete by placing the joint concrete in the state where the previous load is applied and then hardening by placing the bottom concrete. It is the method that is applied. This method has the advantage of shorter air because it introduces prestress to all beams and simple structure because it does not arrange PC steel wire.

The prior art is to apply an in-cable or out-cable method to partially introduce the prestress to the joint of the preflex composite beam assembled with the beam member, and the difficulty is high because the partial prestressing of the joint is performed inside and outside the web of the beam. In addition, the structure of the joint is complicated, and it is cumbersome to load the heavy load on the joint and introduce the partial prestress, which is cumbersome, and it is slow in time and the air is long, and the cost increase and connection work due to the use of PC steel wire and the attachment of the bracket And troublesome dismantling work is a problem.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and in order to improve the workability, shorten the work, and simplify the work in introducing partial prestress to the beam member connection of the preflex composite beam manufactured by the split method. The present invention relates to a pre-stress introduction method of a preplex composite beam by a division method for providing a partial prestress introduction method of a preplex composite beam.

According to the present invention, the prestress is introduced as an oil jack when the prestress is introduced into the joint part before the concrete is cast into the lower flange after transporting, installing, and assembling by the high-force bolt. Its main features are aimed at improving the speed, simplicity and accuracy of work.

1 is an illustration of a preplex composite beam using a split method showing the position of a partial prestress inlet;

2 is a partial prestress load and a moment diagram for a preflex composite beam by a split method;

3 is an installation diagram of an oil jack for introducing partial prestress to a junction of a preflex composite beam using a split method;

<Explanation of symbols for main parts of drawing>

1: preflex composite beam 2: upper beam

3: oil jack 4: temporary weight

5: connection concrete

The partial prestress amount to be introduced at the junction of the preflex composite beam applying the split method is the stress to be introduced at the point where the junction is located when the junction is not installed.In general, the initial dry shrinkage of concrete occurs simultaneously with curing. Known. Partial prestressing occurs in the short time after the initial creep is also hardened by the concrete, so when the partial prestress is introduced after assembling the joints of the preflex composite beam using the splitting method of the beam member, the initial dry shrinkage and creep are already It should be regarded as occurring and should be regarded as the initial dry shrinkage and creep progression when the introduction of the partial mortar for the joint is complete.

When the partial prestress is introduced in the prefabricated composite beam splitting method by the oil jack, the stress introduced into the joint at the time of confirming that the compressive strength of the slab concrete is 210 kg / cm ² or more is determined at the time of preflection, release, Sum of initial dry shrinkage and creep stress. Since the self-weight of the composite beam and the self-weight of the slab are introduced equally in the part where the joint is installed or not, the stress that is not introduced because the lower flange concrete is not poured in the joint is stressed at the time of release, stress at release, lower flange It is the sum of the initial dry shrinkage and creep stress in concrete.

In order to introduce these stresses into the joints consisting of pure steel beams, the prestressing force required is calculated by the pre-fraction, release, initial dry shrinkage and creep stresses, and the pre-stressed stresses during fabrication. Is

It is as below formula (a of FIG. 2).

here,

: Sum of lower flange stresses at preflection, release, initial dry shrinkage and creep

: Sum of upper flange stress at preflection, release, initial dry shrinkage and creep

h: Cheolgolbo's Bo Dance

Yt: Distance from the lower flange end to the neutral axis in steel ball

Partial prestress load

* 3 case of fragmentation (b of FIG. 2)

* For 2 chip segments (Fig. 2c)

here,

M _ppf : Moment due to partial prestress load

P _ppf : Partial prestress load, exerted at the junction position

I _s : Second moment of cross section of cheolgolbo

a: distance from point to partial prestress force point (a〉 l / 4)

l: span of beam

Consideration of Preparative Synthesis Beam by Split Method

The introduction of partial prestress to the connection is done in the following way. The upper beam 2 is installed horizontally on the upper side of the preflex composite beam 1, which is composed of a plurality of beam members, as shown in FIG. 3, and the bottom of the beam 2 of the preflex composite beam 1 Install the oil jack (3) so that it is located at the junction (P). The load cell 6 is attached to the top of the oil jack 3, and on the bottom plate concrete on the upper flange of the preflex composite beam 1, the loading beam 7 is traversed in the cross-sectional direction of the beam, and then the load cell thereon. (6) Adjust this contact. The flexural tensile force is introduced to the lower flange of the cheolgolbo by applying necessary bending prestress to the joint of the beam for partial prestressing of the oil jack (3), and the concrete is poured into the lower flange at the joint of the preflex composite beam and cured. The hydraulic pressure introduced to the jack 3 is released to introduce partial prestress into the lower flange concrete of the joint. This is a new method that transforms the existing counter method to suit the building.

When the oil jack 3 acts as a partial prestress force, the oil jack 3 alone or the oil jack 3 and the temporary weight 4 are mixed depending on whether or not cracking occurs in the slab on the hypothesized upper flange. All fixed loads except for the lower flange connection of the steel beams, ie the steel beams required to introduce the prestress as designed to the preflex composite beam by installing an oil jack (3) on the upper beam after the web of the steel beams and the bottom concrete of the upper part are applied. After checking the tensile stress generated in the flange, the concrete concrete (5) is poured into the connection of all beam members. The force by the oil jack (3) is applied to all the loads, In other words, it is obtained by including concrete creep and drying shrinkage.

After the connection part 5 is hardened, the hydraulic jack is released from the oil jack 3 as in the case of releasing at the factory to introduce partial prestress to the connection part of each beam member and load the load.

This method of introducing partial prestress by oil jack is the same as the method of introducing prestress collectively to each connecting part of the whole steel beam like the counterweight method. Therefore, the prestress is introduced in the same principle as the pre-flection of a single steel beam at the factory. It is very advantageous in terms of construction, construction management and construction process density.

Partial prestressing is performed on the preflex composite beam by introducing partial prestressing to the junction of the preflex composite beam according to the division method of the present invention as described above by using oil jack alone or with a temporary weight. This is very easy and quick. In addition, the form of the joint is simple and simple, which shortens the air and simplifies the work by eliminating the PC steel wire.

Claims (1)

After assembling the beam member split steel beams into high-strength bolts, install the beam member split type preflex beam at the upper part, install hydraulic jacks on the bottom of the upper beams, apply hydraulic pressure and apply prestressing force to each joint. A method of introducing partial prestress of a composite beam of a preflex composite beam by the splitting method, characterized by releasing hydraulic pressure after the concrete poured on the lower flange is cured to introduce partial prestress.