China arch bridge reinforcement scheme?

Keywords: concrete arch bridge reinforcement scheme

1. Bridge technical standards are adopted for reinforcement.

(1) Design vehicle load grade: highway -II, crowd 3.0 kN/㎡, deck composition: net-9m+2× 1.0m (sidewalk).

2, reinforcement basis and data

Technical Standard for Highway Engineering (JTJB 01-2003) is the standard of the Ministry of Communications. Code for Design of Highway Bridges and Culverts (bound volume of 1989), Code for Construction Design of Highway Bridges and Culverts (JTJ 041-2000), Standard for Inspection and Evaluation of Highway Quality (JTJ 07 1-98) and Technical Specification for Highway Maintenance. Original design document of Renyi Bridge (Taiyuan Highway Branch 197 1 year).

3. Key points of steel bar design

(1) In the calculation of superstructure, Dr. Bridge (finite element program of plane bar system) is used to calculate the temperature change after live load, dead load and reinforcement, and the most unfavorable load combination is used for control design.

(2) The substructure is calculated as gravity pier, and the calculated load is the most unfavorable combination of all possible loads according to the General Code for Design of Highway Bridges and Culverts. The design is controlled by the most unfavorable load combination. The foundation calculation shall be carried out in accordance with the Code for Design of Foundation and Foundation of Highway Bridges and Culverts, combined with the actual situation of this bridge, and calculated according to the improvement coefficient of foundation bearing capacity of the old bridge.

(3) The bridge deck is calculated as one-way slab and cantilever slab, and cantilever jump beam is used for checking section strength, shear resistance and overturning resistance.

(4) Relevant parameters: relative humidity is 70%, differential settlement of pier and abutment is 10 mm ... The temperature difference between bridge deck and other structures is 5℃.

4, reinforcement method

According to the present situation of the bridge and the requirements of improving the bearing capacity of the bridge and widening the deck, the reinforcement methods are determined as follows:

4. 1 main arch ring

The main arch ring is reinforced with 8cm thick 30 # concrete, and the arch rib and arch wave are reinforced with cast-in-place reinforced concrete. First, clean the mortar plastering layer with a thickness of 1cm on the surface of the main arch rib, then drill holes at the bottom and side of the main arch rib, and plant steel bars at the specified position. After being fixed firmly with epoxy resin, hang steel mesh, drill holes and plant steel bars inside the main arch wave, anchor and spray concrete, and increase the cross section of arch rib and arch wave for reinforcement. U-shaped steel bars are drilled at the bottom of the diaphragm wall, and 30 # concrete with 8cm thickness is anchored and sprayed to strengthen the lateral connection. Arch angle and arch back should be chiseled away from mortar plastering first. Chiseling, cleaning, drilling, planting steel bars, binding steel mesh at the back of arch corner and the root of No.2 bent frame of arch machine, and reinforcing with cast-in-place reinforced concrete 10cm thick.

4.2 Arch building

The arch building is reinforced by 6cm thick 30 # concrete bolting and shotcreting, bent frame and abdominal arch ring; The abutment front wall is reinforced with 6cm thick 30 # concrete. First, chisel away the mortar plastering with a thickness of 1cm on the surface of the main bent, cut the hair around the bent and the inside of the abdominal arch, clean it up, then drill holes and plant rebar around the bent and the inside of the abdominal arch according to the specified position, fix it firmly with epoxy resin, hang steel mesh, and finally anchor concrete. 3cm thick 10# cement mortar plastering on the outside of the solid abdomen section of the arch building.

4.3 Deck

The bridge deck is reinforced by cast-in-situ reinforced concrete side walls on both sides of the original bridge, and precast reinforced concrete cantilever beams, cast-in-situ reinforced concrete carriageways and precast microbend sidewalks are symmetrically added. After the reinforced concrete cantilever beam is prefabricated in place. The reserved reinforcement shall be welded with the bridge deck reinforcement and bound with the cantilever slab reinforcement. Integral pouring of steel fiber reinforced concrete on bridge deck. Pay attention to prevent overturning when placing the cantilever beam, and the height of the cantilever beam should conform to the treatment of the cross slope of the bridge deck. Micro-curved pavement plates are stamped on the cantilever beam, railings are added on both sides of the sidewalk, and the micro-curved pavement plates are plastered with 3cm thick 10# cement mortar. TST expansion joints with a width of 30cm and a depth of 25cm are set near the two abutments of the bridge deck. After the bridge deck pouring is completed, the deformation joints are cut at the top positions of 1# and 2# piers, with a depth of 3cm and a width of 3 mm, and the joints are filled with asphalt after cleaning.

4.4 Abutment and Foundation

The method of bolting and shotcreting 6cm thick No.30 concrete is used to strengthen the front wall of abutment. Chisel away the abutment surface, plant reinforcement, hang steel mesh, clean it up, and then reinforce it with shotcrete. The abutment cap is reinforced with anchor shotcrete, and the thickness of No.30 concrete is 8cm. Chisel the front of abutment cap, plant reinforcement, hang steel mesh, weld the steel mesh of abutment cap with the steel bar of main arch rib, clean the concrete surface, and then spray concrete for reinforcement.

The pier is jointed with 10# mortar, and the pier cap is reinforced by hanging steel mesh on the outside and 8cm thick shotcrete.

According to the actual excavation geological data and the actual situation, the foundation treatment is carried out, and the pier foundation is protected by 20# flaky concrete.

5, bridge reinforcement construction sequence

(1) pier, abutment and foundation treatment.

(2) Remove the sidewalks and railings of the old bridge.

(3) Remove the bridge deck pavement, side walls and fillers on the arch. In the above-mentioned demolition process, each span is carried out symmetrically from the middle of the span to the arch foot, and the demolition of each span is carried out synchronously and symmetrically, so as to balance the stress on the pier and prevent collapse due to excessive one-way thrust.

(4) At the same time, reinforce the main arch ring, the buildings above the arch and the front wall of the abutment.

(5) Cast-in-situ concrete side wall, fill crushed stone filler on arch, adjust transverse slope, install cantilever beam, cast-in-situ cantilever slab on carriageway and steel fiber concrete on bridge deck.

(6) Install sidewalks, railings and expansion joints, and complete all reinforcement works.

6. Reinforce the main materials

6. 1 concrete

30 # sprayed concrete is used for arch rib, arch wave and buildings above arch, 30 # cast-in-place concrete is used for arch back and wet joint, 30 # steel fiber concrete is used for bridge deck, 30 # precast concrete is used for cantilever beam and microbend plate, 25 # precast concrete is used for railing, 30 # cast-in-place concrete is used for pier (platform) and 20 # cast-in-place concrete is used for foundation.

6.2 reinforcement

The steel bars used in the design are Grade I and Grade II. Unless otherwise specified, when the rebar diameter is greater than or equal to 12 mm, ribbed rebar (Grade II rebar) conforming to GB- 1499-98 current national standard shall be adopted; When the rebar diameter d is less than d< 12mm, round steel (i.e., Grade I rebar) conforming to the current national standard GB-13013-91shall be adopted.

6.3 Others

(1) Epoxy resin adhesive and epoxy resin mortar are determined by experiments according to the requirements of relevant specifications and product descriptions.

(2) This bridge has only one TST expansion joint at both ends of abutment.

7, construction methods, key points and matters needing attention

(1) The main arch ring (main arch rib, arch wave and cross beam) is wrapped with steel mesh, and the section is enlarged by shotcrete. The construction shall be carried out in strict accordance with the bolting and shotcreting technology.

(2) The buildings on the arch (bent frame, belly arch ring) are wrapped with steel mesh, and the section is enlarged with sprayed concrete. Construction shall be carried out in strict accordance with the bolting and shotcreting technology.

(3) Bridge deck and sidewalk widening construction. (1) The bridge deck is made of steel fiber concrete, and 37.5kg of needle-like steel fiber is added to 1m3 concrete; (2) Cantilever cantilever beam is installed in place, and bridge deck reinforcement is welded to ensure stability. In order to ensure that the root of cantilever beam (slab) is practical and reliable, its pouring construction should be formed once with the bridge deck; (3) Dismantle the bridge deck, and remove all the original lime slag fillers and side walls on the arch. Cast-in-situ reinforced concrete side wall No.30 is filled with gravel filler with good water permeability, and the cross slope of the bridge deck is adjusted to 2% (the cross slope is formed by gravel filler on the arch), and then steel fiber concrete with a thickness of 25cm is poured on the bridge deck; ④ The expansion joint adopts TST rubber telescopic body, and a professional team is hired for construction to ensure the engineering quality; ⑤ Masonry retaining walls on both sides of the bridge head, build approach roads, and connect the roads on both sides of the bridge. According to the alignment of Qingxu-Gujiao Highway, it should be comprehensively planned, leaving enough length to meet the requirements and prevent bumping at the bridge head.

(4) substructure and protection works. The substructure construction and quality standards shall be implemented in accordance with Technical Specification for Highway Bridge and Culvert Construction (JTJ 041-2000), Standard for Quality Inspection and Evaluation of Highway Engineering (JTF 071-98) and relevant regulations. For the old bridge protection project, check whether there are cracks, subsidence, etc. And treat diseases.

(5) Remove the weathered layer scoured on the bridge pier surface, and use 10# cement mortar for plastering and jointing.

(6) The surface mortar of the sprayed concrete part of the original bridge structure shall be removed, chiseled and cleaned before the sprayed concrete construction can be carried out. When planting reinforcement on the original bridge structure, drill a hole with a depth of 8cm on the structure, and the diameter of the hole is determined according to the diameter of the reinforcement to be planted. After hole cleaning, pour epoxy resin glue, and then insert reinforcement. After the bonding is firm, the steel mesh can be hung.

(7) Strengthen technical supervision and testing, improve technical equipment and formulate strict technical measures.

(8) Pay attention to technical measures and files, collect technical data in time, and keep up with the construction progress. Complete technical data, scientific, standardized and earnest.

(9) Adhere to the policy of "safety first, prevention first" in production safety, set up placards at the site, set up warning signs in dangerous areas, and set up mechanical and electrical equipment safety operation procedures boards. All unsafe behaviors and illegal operations are strictly prohibited.

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