The material parameters are: upper and lower chord: e = 20000000kn / ㎡, length L = 0.7m, section area a = 0.255 ㎡, moment of inertia I = 3.97e-6.
In box chamber area, the uniformly distributed load on the top surface of a Bailey beam is: 4862.4 / 12 * 20 = 20.26kn/m.
Each row of steel pipes are connected with [16 channel steel and i16 I-beam to improve the stability of buttress.
3.
4.2.3 calculation model of Bailey beam The single Bailey beam is a statically indeterminate structure.
The specific design scheme of the bracket with less support structure is as follows: the bracket is driven with steel pipe pile, and the steel pipe pile is driven with steel pipe pile Φ 630、 Φ 529 steel pipe, double rows of i40 I-steel cushion beams are arranged longitudinally and horizontally on the pile top; Bailey beam is adopted for the main truss of the bracket.
1.
The settlement of steel pipe pile with less support is controllable.
Square wood is laid on the bowl buckle frame, and the bottom formwork is installed on the square wood, and then the side formwork and end formwork are assembled.
4.2.2 calculation of Bailey beam load The most unfavorable load on a Bailey beam is as follows: standard section: diaphragm area, the uniformly distributed load on the top surface of a Bailey beam is: 2966.5 / 12 * 12 = 20.6kn/m.
4.1.2 support is adopted Φ When 630 steel pipe (wall thickness not less than 1cm) pile is used as the foundation, the calculation process can be referred to Φ 529 calculation of steel pipe driving depth.
The tower beam adopts consolidation system.
2.1 the construction scheme of less support is to make the steel pipe pile into a bent form as the support pier of the support, use the steel pipe to erect the Bailey piece on the ground to form the support, and use the bowl buckle frame set on the Bailey piece as the elevation adjustment component.
See the following figure for the elevation of the less support structure and the section of the standard section: 4.
Make full use of the characteristics of steel pipe pile and Bailey frame, with large bearing capacity and small deformation.
2.
Project Overview: the starting point stake on the west side of the bridge is K0 + 895.0m, the end stake on the east side is K1 + 735.0m, and the total length of the bridge is 840m, including 320m long main bridge, 200m long East and west approach bridges, and 120m long middle approach bridge.
The superstructure of the main bridge adopts the whole design, and the main pier foundation adopts the separated pile group foundation.
2.2 the construction of the main span of the bridge is located in the riverbed, with high groundwater level and large uncertain factors in flood season.
The ultimate bearing capacity of a single pile is divided into two parts: the ultimate bearing capacity of pile end soil and the ultimate friction resistance of pile side soil, namely: – the vertical ultimate bearing capacity of a single pile (KN); – pile end resistance; – the cross-sectional area of pile body (M2) ; – influence coefficient of vibration pile sinking on the friction around the pile of each soil layer; – length around the pile body (m); – ultimate friction of the soil around the pile (kPa); – length of each section of pile divided by soil layer (m) If the safety factor is taken as 2 according to the code for design of highway bridges and culverts, the allowable bearing capacity of driven friction piles under vertical compression is: according to the data provided in the geological report, the first layer within the main bridge is coarse sand, the buried depth of the bottom plate is 2.6-15.0m, the layer thickness is 2.6-10.7m, the average thickness is 5.26m, and the structure is slightly dense.
The support is characterized by using Beret instead of foundation treatment, high material turnover and utilization rate, strong applicability, safety and reliability, light support material weight, high degree of construction mechanization, and can effectively save the construction period.
Web member: e = 20000000kn / ㎡, length L = 0.7m, section area a = 0.1024 ㎡, moment of inertia I = 1.013e-6.
If considering the adverse conditions, there is coarse sand layer within 12m of steel pipe pile driving depth, it can be calculated Φ The allowable bearing capacity of single pile of 630 steel pipe pile is: therefore, within the range of all medium coarse sand, the soil depth of support steel pipe pile should be greater than 9m.
The bridge deck is 41.5m wide and the outer cantilever is 2.5m.
The tower body is arranged between the non motor vehicle lane and the motor vehicle lane.
In addition, during the actual pile driving construction, the static bearing capacity of steel pipe pile is controlled by the dynamic measurement method of single pile bearing capacity according to the actual situation, so that each pile can reach the design allowable bearing capacity.
36 rows of Bailey beams are arranged horizontally, and each row of Bailey beams is assembled by 27 Bailey pieces.
The transverse connection system is assembled on the Bailey beam, and channel steel [16 is arranged as the distribution beam, and the stiffness meets the requirements.
I = 1.5% cross slope shall be set on the bridge deck.
In flange area, the uniformly distributed load on the top surface of a Bailey beam is: 628.8 / 12 * 4 = 13.1kn/m.
Ф The top surface of 630 steel pipe column uses two i40b I-beams along the bridge as the distribution beam; two i40b I-beams along the bridge are arranged on it.
4.2 calculation of Bailey beam bearing capacity: 4 6 m + 9 m + 12 m is selected for the crossing system in the general layout × 4 + 7.5m + 6.8m + 2.56M nine span continuous Bailey beams (one quarter of the main bridge).
After the full support foundation is soaked in water, the foundation bearing capacity will decrease significantly, which is easy to cause uneven settlement and uncontrollable settlement.
If considering the favorable situation, the upper 5.26m within the driving depth range of steel pipe pile is coarse sand layer, and the rest are round gravel layer, the soil penetration depth of steel pipe pile should be greater than 9m.
The middle is supported on two rows of vertical columns, 11 steel pipe columns in each row are arranged perpendicular to the center line of the bridge; each row of buttresses are made of Ф 630 steel pipe column with 80cm connection at the top of the column × 80cm × 2cm steel plate.
The second layer is round gravel, the layer thickness is 8.3-19.2m, the average thickness is 15.5m, and the structure is medium dense dense If considering the adverse conditions, the steel pipe pile is driven into coarse sand layer within 12m depth, then it can be calculated Φ The allowable bearing capacity of single pile of 529 steel pipe pile is: if considering the favorable situation, the upper 5.26m within the driving depth of steel pipe pile is coarse sand layer, the rest is round gravel layer, and 9m is taken for steel pipe pile, it can be calculated Φ The allowable bearing capacity of single pile of 529 steel pipe pile is: therefore, within the range of all medium coarse sand, the soil penetration depth of steel pipe pile should be greater than 10.7m.
The cable tower adopts a simple and lively appearance design.
The calculated maximum stress of Bailey beam is 188n / mm2 and the calculated minimum stress of Bailey beam is 203n / mm2, which are less than the allowable stress of Bailey beam 273n / mm2, so they meet the strength requirements.
Bailey longitudinal beam is arranged on it, i16 I-beam is arranged on the top surface of Bailey longitudinal beam, and bowl buckle support is arranged on it × 15cm square timber as beam, 10 × 10cm square timber as longitudinal beam.
Inclined rod: e = 20000000kn / ㎡, length L = 0.984m, section area a = 0.1024 ㎡, moment of inertia I = 1.013e-6 The calculated maximum axial tension is 190878n and the calculated maximum axial pressure of Bailey beam is 201220n.
The height above the bridge deck of the main tower is 34.21m, and the section of the tower body is 4m wide along the bridge direction and 2.5m wide in the transverse direction.
Stress calculation of the support: 2021 Practical reference of municipal roads and bridges Baidu network disk member 4.1 calculation of bearing capacity of steel pipe pile 4.1.1 Φ Calculation of bearing capacity of 529 steel pipe pile (designed according to 40 tons of single pile): according to the data provided in the South engineering geological exploration report, the main bridge construction support adopts Φ 529 steel pipe (wall thickness not less than 1cm) pile is used as the foundation and struck with a vibrating hammer with an exciting force of 90kN.
A bowl buckle frame is set on the channel steel to adjust the camber.
Selection of construction scheme: considering the construction characteristics and environmental factors of the project, the less support construction scheme is adopted for the support form of box girder of the main bridge.
The structure is a prestressed concrete cable-stayed bridge with single tower and double cable planes.
The bridge deck is arranged with horizontal double towers.
The main beam adopts variable height separated double box section.
The calculated maximum deformation of Bailey beam is 0.00824mm, which is less than the maximum allowable deflection of Bailey beam [v] =12000 / 400 = 30mm; meet the stiffness requirements..
