KR20040027562A - Steel Box Strengthening Method of Anchorage End of PS Concrete Girder - Google Patents

Abstract

PURPOSE: A reinforcement method for a PS concrete girder anchorage end using a steel box is provided to prevent the vertical crack on an end of a PS concrete girder used for a PS concrete composite bridge. CONSTITUTION: The reinforcement method for a PS concrete girder anchorage end using a steel box comprises the steps of installing a steel box provided with a shear connector(12) for a girder and a shear connector(13) for an upper plane and a floor plate together with a reinforcing bar in a form before placing a PS concrete girder, then placing a concrete girder and placing a horizontal beam and a floor plate.

Description

Steel Box Strengthening Method of Anchorage End of PS Concrete Girder}

Split-cracking of anchorages based on the existing design, as the design method based on the strut-and-tie model of the concrete structure was introduced into the European Design Code (Eurocode 2) and the recent US Design Code (ACI319-02). In addition to splitting cracks, it is necessary to control the longitudinal cracks that may occur at some distance from the anchorage. 1 is a typical PS concrete composite bridge that PS concrete girder 21 is used. Tension force 31 introduced as a concentrated load on the fixing end portion 20 of the PS concrete girder is spread into the PS concrete girder by the compression section force 32 as shown in FIG. The inclined diffusion of the compressive section force 32 generates a tensile cross section force 33 in the height direction for equilibrium conditions, and the tensile cross section force 33 over the entire abdominal height causes a potential longitudinal crack. This phenomenon occurs as shown in FIG. 2 even when the compressive cross-sectional force of the relatively narrow abdomen is diffused in the wide flange. The design of the strut-tie model determines the required concrete cross section and reinforcement by the truss analysis, which consists of inclined compression struts and tension ties for equilibrium. The area where the normal beam theory is not applied to the change of stress in the cross section due to the inclined compressive sectional force flow is called the disturbed zone (D-zone), and the area where the constant stress distribution can be applied. Is called the B-zone. Also, according to the PCI Journal (Vol. 40, No. 3, pp. 110-123), the durability of PS concrete bridges used in the last 30 years since the 1960s is not a big problem, Some damage was reported.

This method is to surround the fixing end of the PS concrete girder in a steel box (steel box) to resist the tensile cross-sectional force 33 of Figure 2 to suppress the occurrence of cracks. In addition, when a crack is generated, it may also play a role of increasing the compressive strength of concrete, such as spiral reinforcement of a spiral reinforcement column or concrete-filled steel pipe (domestic application 10-1986-0003052). As such, this method aims to suppress the occurrence of longitudinal cracking and growth control that may occur in the vicinity of the fixing end of the PS concrete girder.

The anchoring end of the PS concrete girder acts in a region of high tension and point reaction force, and forms a disturbance zone and forms a height tensile cross-sectional force of the girder in the process of spreading the concentrated load into the interior of the PS concrete girder. It is necessary to suppress the occurrence of potential cracking and to control the cracking caused by the tensile section force. In addition, the anchorage end shall be capable of preventing damage due to erection of the girders or external collisions and point reactions during use.

In particular, additional facilities are connected to the girders in use for the repair and reinforcement of bridges, which are of recent importance. However, the connection of additional installations generally requires boring on the girders. Since drilling will damage the girders, the connection of additional installations without drilling can greatly assist in the stability of the structure.

1 is a perspective view of PS concrete composite bridge

[Figure 2] Strut-tie model of PS concrete mounting end

3 is a perspective view of a steel box for reinforcing PS concrete fixing end

4 is a perspective view of the installation process of the reinforced concrete box for PS concrete mounting end

5 is an illustration of the connection of the assembly or additional facilities

<Description of the symbols for the main parts of the drawings>

10: steel box for reinforcing ends, 11: steel sheet,

12: concrete girder shear connector (welding studs or bolting studs),

13: concrete deck shear connector (welding stud),

20: anchorage end, 21: PS concrete girder,

22: steel reinforcement, 23: PS tension anchor,

24: slab, 25: cross beam,

26: support, 27: piers or shifts,

31: tension force, 32: compressive sectional force,

33: tie of tensile section force,

41: connecting device of external liver material (domestic application 10-2001-0036723),

42: prefab crossbeam,

43: load bearing reinforcement using prefabricated brackets (domestic application 10-2001-0022460)

This method is to install the steel box of Figure 3 in the PS concrete girder fixing end to suppress and control the occurrence of potential cracking by the tensile cross-sectional force (33) of Figure 2. In the steel box of the present method, a welding head stud or bolting head stud (domestic application 10-2003-0099610) is used as the shear connector 12 to connect with the girder as shown in FIG. A welding head stud is used as the shear connector 13 for the connection.

The steel box of the present method is installed together when the reinforcing bar 22 is placed before the concrete girder 21 is poured as shown in FIG. 4, and the reinforcing bar may be welded to the steel box for fixing. After the formwork is installed, the concrete girder is poured and cured. After the PS concrete girder is installed in the piers or girders, the cross beams and the bottom plate are placed and cured.

The fixing end of PS concrete girder reinforced by steel box of this method has the following effects in the prefabricated structure as well as the suppression and control of longitudinal cracking at the fixing end required by the new design method strut-tie model. It is expected.

① The steel box is supported by the tensile section force 33 of the strut-tie model to suppress the occurrence of cracking.

② In case of cracks, crack growth can be controlled by increasing the compressive strength of concrete, such as spiral reinforcement columns or concrete-filled steel pipes, by lateral compressive stress caused by steel box.

③ If the additional facility or assembly member of Fig. 5 is connected to the PS concrete girder being used for repair or reinforcement, welding or bolting head studs and high-strength bolts can be connected without drilling.

④ The damage of girder end by external impact can be prevented when PS concrete girders are laid on piers or shifts.

⑤ PS concrete girder reinforced by steel box can be continuous by simple method using welding or high-strength bolt on the side of steel plate like steel girder at the inner point of continuous beam.

Claims (1)

This method is to reinforce the PS concrete anchoring end with steel box to control and control the occurrence of potential longitudinal cracks at the end of the PS concrete girder used in the PS concrete composite bridge. Before placing the PS concrete girder used for the PS concrete composite bridge, the steel box 10 of FIG. Installed in the formwork with reinforcing bars (22), a method for producing PS concrete girder.