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The outline of maintenance·management and repair·reinforcement work For the composition of industrial foundation and improvement of living circumstance, a number of constructions and engineering constructions have been built since 1960's. The high level of economic development and basis contribute to the promotion of public welfare, but the traces of a shoddy and fault construction that neglect the safe in process of high development pursuit have begun to be seen here and there. These shoddy and fault construction has developed into the small or large collapse of facilities such as Songsu Grand Bridge collapse in 1994, Sampoong Department store collapse in 1995 and heavy loss of prosperity and lives. After those disasters, the special laws about safe management of facilities have been enacted. Also the close safe diagnosis and safe inspection have been operated to keep from disasters, promote the effectiveness of facilities and ensure public security through the maintenance management and repair·reinforcement work.

Design diagram, specification -Maintenance, business management ledger - Structural calculation statement - etc

Investigation of the present situation : The history of structure, the blueprint, natural condition, other dates and macrograph

Detailed investigation : The non-destructive test and various laboratory tests on the building place

Inspection of structural stress : Tensile stress, shearing stress, bending stress, compressive stress, the security of other members

Inspection of functional factors : Leakage, crack, deflection, deterioration, scaling, rust-preventing, joint queer, etc.

Decide upon stress calculation, reinforcement plan, use material and construction method, and write out specification and itemized statement

In case of demanding the structural reinforcement, the section expansion, the synthetic organization (steel plate carbon fiber sheet, C/F), stress decreasing and dispersion inside·outside grouting

The independent inspection and valuation about completion situation

This is the method that is used when the section extension of structure due to the differential settlement, seismic the deficiency of reinforced bar is demanded and unify the concrete and steel plate by epoxy resin. The steel plate is attached to the existed concrete with the anchor. Below picture is the example of method attaching the steel plate to the existed concrete. (Method for attaching 1, 2)

[The feature]
- The unchangeable execution on the present structure
- The unification of steel plate and concrete structure with epoxy resin
- Poor department reinforcement of structure

2-1)
The carbon fiber sheet is usually used CFRP, the material combination with epoxy resin and so on. The construction method that the fabric material of cloth form or the carbon fiber on sheet attaches to concrete by unification of the epoxy resin has been studied and in order to maximize the intensity of carbon fiber, the same feature on the field concrete as important as the lineal composition of fiber is also demanded. Therefore the carbon fiber sheet is developed as satisfying the construction demanded the same shape as lineal composition and the member of concrete. That is to say, it is the method that the carbon fiber is arranged in one direction.

2-2) Using of carbon fiber sheet method
- Civil part -- Concrete road bridge, the repair·reinforcement of RC bed deck, tunnel, box culvert and earthquake reinforcement of railway bridge - Architectural part -- Column, beam and wall of the compression·earthquake, beam and slab of the bending protection in the concrete structural whole parts.

(3-1) The surface treatment
- We remove the deterioration stratum of execution of work section (laitance, aeration, stripping mortar, painting, cranked fish plat, pollution department, etc.) using the disk sand blasting and grind it to expose the section of high intensity in order to secure the enough adhesive strength.

- We must plane away the projecting part of surface (concrete joint, from gap) with the concrete plane, disk sand blasting, etc and make it even. Also, the surface gap must be within 1mm on execution of carbon fibrous sheet.

- We curve the edge smoothly with the disk sand blasting. The edge necessary for strength revelation of carbon fiber sheet is different depending on the type of carbon fibrous sheet, but it is desirable to largely, smoothly as possible. (In case of interference on execution, to more largely.)

- We get rid of the powdered dust created during grinding completely with the compressed air, the swab. In case of cleaning with water, the ground section must be dried enough after cleaning and the abrasive surface should be smooh as possible.

(3-2) Section restoration - When the remarkable damaged part of section and the inferior part of blow-hole is created, we must restore them with the material of section restoration that has the same or higher strength as concrete and complete smoothly. Then, the adhesive strength between the existing materials and restoration ones forming the section is as high as that between the primary material or the higher. And in case of exposing of reinforcement bar, we must unify it by restoring the section after rust-preventing and put epoxy resin in the crack to repair, then complete smoothly.

- When there is leakage in the crack, joint, the separate cut off, water conveyance handing is demanded and the error of repair must be within 1㎜.

(3-3) Primer shred
- After weighing the main agent and accelerator at the mixing ratio of 2 : 1 in the round container, to mix it on low-speed revolve until it is homogeneous (about 2 minutes). We use the low-speed rolling agitator at the agitation, especially must agitate the nearby wall of container carefully. The once mixing amount must be the one able to be completed within the syncope time and must never use the amount exceeding the syncope time. In any case, we must not use the primer diluted with solvent and dry and then use the brush or roller wet with solvent.

- Spread equally with the roller or brush. As especially, in winter season, the primer's viscosity becomes higher, note that the thickness controlling is difficult. At the part that lots of primer infiltrate, the twice spread is operated after the first spread section is dried properly. The spreading amount changes depending on the kinds of execution section (ceiling, wall) or roughness. The standard of spreading amount is 250g/m2

- In state of below 5 degrees C. , rainy weather and road frosting, we don't execute check the temperature of executed part and choose the proper primer.

- We dry the spreading section until we can't feel sticky. (According to the temperature, contact drying hour changes.)

- In case of forming a drop on the surface after primer hardening, we file away roughness by the sand paper grinding work before attaching the sheet.

- The execution field must be ventilated and using the firearms is prohibited strictly. Wear the protective device (mask, engineering glasses, rubber gloves) surely on execution.

(3-4) Unevenness revision
- As the state of unevenness revision is reflected as it is in the completion of carbon fiber sheet execution. The error of work must be within 1㎜.

a) Plug the epoxy putty in the concave part of surface

b) Take the rounding process in the corner part with the epoxy putty.

c) Fill up the honeycomb of concrete surface because it causes the air bubbles. The front putty completion is desirable if possible.

(3-5) Carbon fiber sheet gluing
- No execution in the condition of below 5 degrees Celsius, rainy weather, road frosting. Choose the proper resins checking the temperature of executed part. Spread the poor resin enough and operate the steeping air drain method . The jointing length secures the 10cm or more.

a) Cut the carbon fiber sheet into the required size with the scissors and knife etc. It is desirable to restrict the quantity to that only for the day in order to prevent the damage in the custody and the cut sheets must be handled carefully so that the arrangement of fiber wouldn't disperse. (neither roll them too small nor carry them being folded) The cutting length of carbon fiber sheet is decided on the building field according to the skill in the carbon fiber sheet method, working space etc, but in general, 2 - 3m is the proper length. In case of using too long cut sheets, we must notice that the level of execution becomes low like handling, steeping, etc.

b) Check that the primer of execution surface, unevenness revision material is dried. A week after execution of primer, unevenness the part roughly with the sandpaper and then practice the sheet attaching work. Also in case of dewy, touching rain on curing of primer, epoxy putty, the rough surface handling with sandpaper is practiced.

c) After weighing the main agent and accelerator at the mixing ratio of 2 : 1 in the round container, to mix it on low-speed revolve until it is homogeneous (about 2 minutes). We use the low-speed rolling agitator at the agitation, especially must agitate the nearby wall of container carefully. The once mixing amount must be the one able to be completed within the syncope time and must never use the amount exceeding the syncope time. In any case, we must not use the primer diluted with solvent and dry and then use the brush or roller wet with solvent.

d) The carbon fiber sheet is attached to the spread surface with stacked the two shaped paper. At this time mind that the air bubbles isn't inserted between the carbon fiber sheet and resin as possible. Then make close adhesion sheets on the two shaped paper with the rubber scoop. Check that the carbon fiber sheet adhere closely to resin spread surface and take off the two-shaped paper carefully.

e) Rub the carbon fiber sheet 4-5 times in direction of fiber length strongly with a roller. At this time, remove the air bubble checking that the resin is cut and put out between sheets. We must practice the adhesion work with great care especially in the corner edge. Practice the adhesion operation towards the corned while in direction of for from edge. The direction of common adhesion work is like below pictures.

f) The joint towards fiber length must be executed guaranteeing 10cm or more. The resin is spread enough and we fold the carbon fiber sheet on it. The joint towards fiber width isn't necessary.

g) After attaching sheets, leave the resin as it is for a half hour to two hours for natural adhesion. After the initial reaction finishing of resin, if the rising or crossing occurs at the time of rising viscosity, we must adhere it with the roller, etc.

h) After leaving as it is for 30 minutes or more, spread the resin with the roller or brush (top spread). At this time, spread resins moving the roller in direction of fiber length and give attention to that the executed carbon fiber sheet is wound on the roller. The standard spread, amount is like following

　　 - The carbon fiber sheet of unitary weight 200g/m2:200 ~ 100g/m2 in the top spread (planning resin amount 600g/m2)
　　 - The carbon fiber sheet of unitary weight 300g/m2 300 ~ 200g/m2in the top spread (planning resin amount 800g/m2)

　※ Planning resin amount = top spread + low spread

Spread the top spread resin with the roller and then practice the finishing adhesion work with the rubber scoop.

i) When we execute the carbon fiber sheet of two floors or more, we must practice the low spread work of second floor after the top spread of first floor is dried enough and the rest process is operated by the same way. At this time, we must inspect the poor-qualified part (coming off or swelling) and revise it, then execute the second floor. Method of the poor-part revision is like the following.

　　 - Small unfastening : making the sword cut in direction of fiber length and complement of resin.
　　 - Big unfastening : cutting to remove the poor part → putty filling → sheet adhesion.

j) If we execute the next floor before resin drying, the crossing may be caused and it may be stripped. Especially in winter season, as the resin hardening becomes late, we make it a rule to execute a floor a day as possible.

k) The sufficient ventilation is demanded in the executing field and prohibited any kind of work with fire, notice the inhalation. Make sure that the worker wear the protective device (mask, construction glasses, rubber gloves) on execution.

l) In ease of the outdoor execution, protect and curing with the cover so that the rain, sand, dust wouldn't attach to it. But, mind that the cover doesn't contact on the execution surface. In order to achieve the design strength the below curing period of concrete is demanded.

- The average temperature 10 degrees C. , the curing period of two weeks (resin for winter)
- The average temperature 20 degrees C. , the curing period of a week (standard resin)

m) After the carbon fiber sheet execution, tunnels predicted to be affected by the wind before resin hardening is taken a proper step.

　　 -The single-part fixing : It is necessary to fix the carbon fiber sheet physically until the resin hardens enough and to prevent stripping caused by the strong wind.
　　 -The execution order (jointing direction) : When we select the joint part, we execute it with little affecting to the joint in consideration of wind direction. (example. Execute from the opposite direction of wind)

n) Because the carbon fiber has electric conduction, the carbon fiber sheet may float. Therefore when the high-tension wire line, substation, power-transmission line exist near, cutting in the separated in advance is demanded.

o) Using the resin within syncope time as for the sheet adhesion means that practicing a series of processes from the resin mixing, spreading resin, the adhesion work of sheet and resin, and to finishing air drain method within the syncope time. To do so, it is necessary to mix the resin after preparing for complete works.

3-6) Closing
a) The carbon fiber sheet itself shut off the ultraviolet radiation to prevent the deterioration of resin, but in case that the surface of execution is exposed to the direct rays of the sun, it is desirable to coat with the proof against climate point (urethane system).

b) Other closings When we operate the closing handling except coating, we take the checking test, investigating sufficiently. The execution is based on the standard executing method of each material.

Method increasing the sections and decreasing the maximum stress by establishing more supporters of maximum stress loaded in the central part of Beam due to the excessive load.

By establishing the high-intensive cable, mono, or multi-strand in outside of structure pressed the excessive stress and giving tension, the effect of the distribution of removing extra stress right after reinforcement can be obtained. This is the method using a principle that we introduce the permanent to the structure by tensing the priestess tended arranged properly after constructing members of recast and the tension member is composed of the steel bars, single tracks of high-intensive railway line bounded with bundle.