Cast in situ continuous box girder scheme and support calculation

The expressway super large bridge is 2858.12m long in total. The existing road pavement is 20m wide, asphalt pavement, two-way four lane, no median, 3.5m wide lane, 2m wide hard shoulder and 1m wide earth shoulder. In the design, (32+48+32) m continuous beam is used for crossing, and the beam body is constructed by cast-in-situ support method. After completion of the bridge, normal traffic on Provincial Highway 309 will be restored. 　

The eighth joint of AK0+572 bridge on XX interchange turn of XX expressway is 4 × 20m 4-span continuous cast-in-place box girder. The starting and ending pile numbers are 20 #~Yibin abutment, and the corresponding mileage is Ak0+900~Ak0+900. The box girder section is a single box with two chambers, the beam height is 1.4m, and the deck width is 10.5m. The second hole (22 #~23 # piers) of the continuous beam of this couplet spans the hillside with a gradient of 1:1 and a height difference of 8m. The 23 # pier is located on the hillside, 5m away from the slope toe. The mark of cast-in-place box girder concrete is C40. 8cm C40 cast-in-place concrete and 10cm asphalt concrete are used for bridge deck pavement. ）In order to reduce damage to existing hillsides and ensure safety during construction, the following support scheme is proposed for construction in the overall construction scheme: erecting buttress with bowl shaped scaffold at the slope toe; Build ground beams on the hillside; I56a I-beam is used as the main beam to erect the door opening at the buttress and beam, and the calculated span is 8m. （2） Specific construction process 1. Construction process 1. Leveling the site, hardening the foundation, erecting piers and building ground beams, erecting longitudinal distribution beams, erecting transverse support beams, installing longitudinal main beams, installing transverse main beams, erecting scaffolding 2. Construction process (1) erecting piers, erecting piers with bowl shaped scaffolding, The erection parameters are: the vertical and horizontal directions of the upright within the base plate range are 0.3m; The horizontal spacing of vertical poles within the flange plate is 0.6m, and the longitudinal spacing is 0.3m; The step distance of cross bar is 0.6; The cross bridging shall be set up every other row horizontally and not less than 5 times longitudinally. Since the buttress is not perpendicular to the line direction, at least 5 rows of short side scaffolds shall be erected. The scaffold is erected on a 30cm thick C15 concrete base. The concrete base is 12m long, 1.5m wide and 30cm thick. After the installation of buttress jacking, a 2m long 10 × 15cm square timber shall be longitudinally placed on the jacking as a distribution beam. 　　

1、 Project overview The project runs through the North Ring Road and crosses the xx River. It is designed as a 3 × 21.233 m three span simply supported beam section single box six cell prestressed concrete continuous box girder with a height of 1.1 m, deck width of 23.70-32.34, bottom plate width of 28.38 m, single side wing plates of 2.000 m and 2.123 m, the cross slope of the top plate is vertical with the web of the deck, and the bottom plate of the box girder web is provided with air vents, with a diameter of 10 cm. Each room is provided with three corresponding holes. Prestressed steel tendons shall be 270 grade Φ j15.24mm high strength and low relaxation steel strands conforming to ASTM416-97 standard, with standard strength Ryb ≥ 1860Mpa and nominal area A=140mm2. The starting stake number is KO+848.611, the ending stake number is KO+917.210, and the intersection angle is 19.6204o.  

The data are compiled by well-known domestic enterprises for famous bridge projects. The north bank approach of the bridge is 194m long, with a span of 3 × 46+50+6 (abutment) m, the south bank approach is 240m long, with a span of 4 × 46+50+6 (abutment) m, the approach is 434m long, the bridge width and subgrade width are 35m, and constant cross-section prestressed concrete continuous box girder is used. The box girder cross bridge adopts single box six compartment section, The height at the center line is 3.5m, and the bridge deck is laid in two directions by 2%. The bridge height changes from 3.5m at the center line to 3.16m. The top plate of the box girder is 34m wide and 28cm thick, and the bottom plate is 21m wide and 25cm thick. The inclined web of box girder is 7.389m long and 20cm thick. The bottom plate of the hanging wall corbel at the junction with the platform between the ribs is 29.702 meters wide, and the mid span web of the box girder is 50 cm thick. At L/4~L/5, a web width transition section is set, and at the fulcrum, a diaphragm with a width of 1.5~3.0 meters is set to form a concealed capping beam, and a transverse prestressed steel tendon is configured. [Content excerpt] The approach bridge concrete box girder is constructed with a span by span erection cast-in-situ scheme, Cast in situ in sequence from the rib platform to the abutment, set construction joints at the cantilever of L/5 (9.0m from the center of the front pier of the secondary span) for each span... Erect two spans of supports at the same time, so as to construct the cantilever sections of the first span and the secondary span at the same time. After the concrete reaches the specified strength and the tensioning and grouting is completed, remove the supports of the first span and erect the supports of the third span, and carry out the construction in sequence. The support adopts the construction scheme of full hall bowl buckle support...... The support adopts WDJ Φ 48 × 3.5 mm steel pipe bowl buckle type steel pipe frame, and the vertical pole mainly adopts 3.0m, 2.4m, 1.8m, 1.2m. The vertical pole is lengthened and staggered. The length of the top pole is 1.5m, 1.2m, 0.9m, and the cross pole is 0.9m, 0.6m, 0.3m. The top and bottom brackets are adjustable braces...... [CAD and table attached] Bill of quantities of main engineering materials, layout of cross bridging, 3 CAD drawings of cross section of box girder of north bank approach bridge, 2 CAD drawings of support layout of span pier of box girder of approach bridge, 3 CAD drawings of cast-in-situ support layout of box girder of approach bridge, 2 CAD drawings of cast-in-situ support layout of box girder of approach bridge, bar chart of box girder construction progress, 34 pages in total,

The construction scheme for the reserved bracket door opening of cast-in-place prestressed concrete continuous box girder is detailed and can be used for reference.