Aramid Glass Hybird Fabric Reinforcement on Old Bridge of Changwat Suratthani,Thailand
In March, 2011, the flood disaster in the south ofThailandwas severe, as of 29 a total of 10 people died from unremitting six-day flooding. Especially Changwat Suratthani, where the impounded surface water reached up to 3 meters because of the flood and a lot of bridges were destroyed. In order to speed up the strengthening process of bridges and improve the flood control ability, undirectional reinforcement of glass fibre is adopted.
The loading text on the first step of first page and the second step of third page of the main bridge is conducted after detecting the bridge, according to loading test results, the strain calibration coefficient of principal measurement point at controlling section of the first step of first page of main bridge is greater than 1, the relative residual value of strain and deflection is less than 20%, and the strain and deflection calibration coefficient of principal measurement point at controlling section of the second step of third page is greater than 1, the relative residual value of strain and deflection is less than 20%. The bearing capacity of this bridge is insufficient.
The bridge pier and beam column are also subject to different degrees of damage, which made a serious impact on stability of the bridge as well as on safety and smoothness of vehicle driving, under the strike of the flood.
Main mechanical performance index
Standard value of tensile strength (MPa)
Elasticity modulus (Gpa)
Fabric (I class)
Engineering design of maintenance and reinforcement
The scope of pasting fabric at beam bottom is determined according to detection conclusion and technical parameters provided by testing unit. An overall fabric is pasted at the position of its bridge location according to structural crack location in the report (the 13th hole of right width and 14th hole of left width of main bridge, 5th hole, 7th hole and 14th hole of ramp), of which for the reason that the 13th and 14th hole have pasted prestressed glass fiber board in the third page of main bridge, the fabric is only pasted on the 12th and 15th hole, the 5th hole of Z ramp being the first page, the 7th hole being the second page and the 14th hole being the third page, therefore, the fabric is pasted on all lines at ramp.
3、Construction technology of pasting fabrics
3.1、Surveying engineering: make a lofting on the bridge according to the location of pasting fabrics confirmed in construction drawings, draw out the area of pasting fabrics and carry out the construction process to paste the area, the four angles of the column are required to be circular bead with radius of 20mm. Measurement accuracy required: the error is no greater than ±10mm.
3.2.Surface treatment: the concrete surface within construction work area are all polished with angle grinder, the polishing depth shall not less than 0.5mm, and the surface layer is required to be intact without any plasma skin, loss mass, dust oil and grease. Use air compressor nozzle and hairbrush to eliminate the dust and loss materials. There’s a need to adopt ensilage dump blower or dust collector to completely sweep away the surface dust and keep dry. The surface evenness is required to be equal or lesser than 5mm/m. At the paste location of intersection angle, a bevel process is carried out on the concrete surface to polish into arc shape, which the the radius of beam is not less than 20mm.
3.3 Crack repair: as to elastic fracture sealed, make a closed repair with full-brash way of the whole area while pasting fabrics.
3.4Clipping of fabrics
（1）Tailor the fabrics in strict accordance with the size the design required.
It is strictly forbidden to chamfer the fabrics and prevent it from wiredrawing phenomenon.
Pay attention to keep the tailored fabrics clean without pollution.
3.5 Collocate and brush underlying glue
Collocate the underlying glue in strict accordance with process stipulation provided by manufacturer.
Use roller brush to evenly paint on the concrete surface with underlying resin. Carry out the construction of next process as soon as possible after being confirmed to be dry with finger touching on glue surface.
3.6 Leveling materials
Collocate leveling materials in strict accordance with process stipulation provided by manufacturer.
The repair on concrete surface selects acetone to wipe off the floating dust on the surface, use leveling materials to fill the surface indentation, smear it as smooth hook face without edges and corners in the position of segment difference and intersection angle.
Use leveling materials to restore as smooth arc at intersection angle, the radius is greater than 20mm.
Use the scraper, whose the width of tool bit ≥100mm, to repair and level, the leveling degree is subject to the grain of unobvious trace of scraper blade and scarping knife by visual inspection.
Carry out the construction of next process as soon as possible after being confirmed to be dry with finger touching on surface of leveling materials.
3.7Collocate and brush impregnating resin or paste resin
Please read the operating manual offered by the manufacturer carefully before collocating the binder.
Ensure each mixing amount according to the actual environment temperature on the spot and paste area in order to prevent waste.
Collocate in strict accordance with metering of weight ration.
Collocate according to mix proportion offered by manufacturer and technological requirements and there must be a special person responsible for it. There shall be no oil and impurities in the mixing container and on the stirrer. Stir it towards one direction (clockwise) until the color and lustre are equal without bubbles produced, and prevent dust and impurities from sneaking into.
The binder collocated shall be used up within service time as required.
Scrub the concrete surface again before pasting fiberglass to ensure no dusts on the paste surface.
Smear the collocated impregnating resin on the paste position evenly with the process stipulation offered by manufacturer. It’s a must to conform to the requirements of stabilization, accuracy and uniformity when brushing structural adhesive on the concrete surface, namely: stabilization means brush with an appropriate force and try not to fall off to the greatest extent; accuracy means the brushing is within the control line; uniformity means an accordant thickness within brushing scope.
3.8 Paste fabrics
（1）Paste the fabrics on the specified position with hands pressing gently, there’s also needed to be steady, accurate and uniform when pasting the fabrics, and it requires an appropriate force for unwinding so as to make it smooth without crumple, fracture. Use specified roller to roll towards the fiber direction, it’s a must to roll from one side to another side when rolling, and it’s inadvisable to roll and rub at one position back and forth, let the glue permeate into fibers in the rolling to achieve a full inflitration and squeezed-out bubbles so as to make impregnating resin soak into fibers fully, it’s forbidden to damage fibers when rolling. An overall lap length of all directions is greater than 200mm when it’s required to carry out an overlap joint of fabrics..
Repeat the above steps when making a multilayered paste, carry out the following paste process as soon as possible after the impregnating resin on fiber surface being confirmed to be dry with finger touching on glue surface.
Smear impregnating resin evenly on the last fabric surface.
3.9Completion of works: the maintenance time is 48 hours and guard against using sharp instrument scraping and touching fiber surface and pulling by people. In order to facilitate the follow-up underground engineering, carry out a rough sand-scattering processing on fiber surface, subject to be adhesive on figures, during 6-12 hours of fabric paste.
3.10Construction technology measures and quality control points
（1） It’s obliged to check and test performance index of factory certification and product quality inspection report of raw material products of fiberglass when entering the construction site.
The concrete surface treatment of base materials is one of the most critical processes for fiber reinforcement construction, and it requires to wipe out floated coat, reveal the concrete structure layer and clear away peeling, loosened, cellular and corrosive faulty concrete on the component surface reinforced. Use epoxy mortar to repair to be smooth, carry out a gap filling or joint sealing treatment in advance if the component is crannied, then polish it smoothly, clean up and keep dry. The interarea is required to be smooth without umbilication and the corners of Yin and Yang shall be sophisticated.
The colloid used for paste fibers shall be collocated in strict accordance with product specification, and the field environmental condition shall conform to the requirements of the product.
Collocate a small amount of adhesion agent each time, it’s forbidden to reuse the remaining and overdue adhesion agent.
The overlapping length of force direction of fibers is not less than 200mm.
In order to ensure that the fiberglass may reliably coordinate with concrete in phase, an additional anchoring method can be adopted.
Fine laying-off, it’s forbidden to employ fiber strips with irregular edge and outer-concave and inner-convexchannel angle.
In the process of pasting fiberglass, there’s a need to roll in place to guarantee the fiber materials are fully impregnated and effectively pasted.
Enhance the inspection and acceptance work of fiberglass paste. The paste quality between fiber and concrete is tested by using a hammer to stroke or pressing the surface of the fiber, and the total effective area is not lower than 95%. Needle-injecting colloid method can be adopted to rectify when the empty drum area is less than 1000m2. When the empty drum area is greater than 1000m2, it’s appropriate to cut off the fiberglass at the position of empty drum and conduct a lap joint again to paste equivalent fiberglass sheet, and the length of lap joint is greater than 100mm.