Construction of cable-stayed bridge of Panyu Bridge?

The following is the relevant content about the construction of the Panyu Bridge cable-stayed bridge brought to you by Zhongda Consulting for your reference.

1. Design Overview and Technical Features

1.1 Design Overview

Panyu Bridge is a large bridge connecting Guangzhou City and Panyu City on the main road across the Pearl River. , located 3.9km downstream of Luoxi Bridge. As the number of vehicles traveling to and from Guangzhou increases from Panyu, Shunde, Zhongshan, Jiangmen, Zhuhai and other places, the completion of the Panyu Bridge will effectively alleviate the traffic pressure on the Luoxi Bridge.

The total length of the bridge is 3467m. The main bridge is a twin-tower space cable-stayed bridge with dense cable floating system and a fully prestressed concrete structure. The main span is 380m, the bridge span combination is 70 91 380 91 70m, the main beam is the side main beam DP section, up to 37.7m wide, the bridge deck is equipped with 8 lanes and sidewalks; the clear navigation height is 34m, the main tower is inverted Y shape, and the tower height is self-supporting It is 140.3m from the table top; the cables are made of parallel steel wire bundles protected by HDPE hot extrusion sheaths, ***244 reported, the standard cable distance on the tower is 1.3m, and the standard cable distance on the beam is 6m. The bilateral piers of the auxiliary piers are hollow thin-walled flexible piers, which serve as both tension piers and longitudinal and horizontal thrust-resistant piers. The main tower foundation is adopted. 3. om diameter bored piles and large-volume solid caps, corresponding to 9 piles per tower column and 18 piles per tower, with the pile bodies embedded in weakly weathered mudstone. The 82# main pier on the Fangao side is located in the water, with a capping size of 54x23.5x6m; the 83# main pier on the Guangzhou side is located on the shore, with a capping size of 48xl7x6m

1.2 Technical features

Cable-stayed There are many variations and combinations of towers, beams, and cables in the design of the bridge structure. Based on considerations of navigation, aesthetics, and regional symbolism, the Banshu Bridge adopted a cable-stayed bridge plan, and the design focused on component size, form selection, and combination. Contains the following features:

(1) Using th3.om large-diameter bored piles and large-volume caps;

(2) Fully prestressed concrete structure;

(3) The main beam of the DP section with a width of 37.7m has a fixed span ratio of 37.7/380 (close to 1/10), which correspondingly increases the span of the main tower beam and the lateral size of the cap;

(4) An inverted Y-shaped tower forest is used. Due to the width-to-span ratio, the lateral slope of the tower columns reaches 3:l.

The above design features put forward higher requirements for construction. Compared with domestic cable-stayed bridges that have been built, since the width of the concrete main beam and the slope of the tower are the largest, we except for In addition to the rational application of high-performance concrete and prestressed construction technology, it has also developed construction technologies such as climbing formwork and hanging basket casting. The diameter of bored piles and the size of the cap used for the foundation also rank first among domestic cable-stayed bridges. , requiring reasonable organization of large-scale foundation construction, we fully combined the geological and hydrological conditions of the bridge location and adopted a unique low-cost and high-speed construction plan in the foundation construction.

2. Layout of the construction site and main production facilities

The bridge runs north-south. The construction sites on both sides of the bridge are arranged on the east side of the bridge and are divided into two major functional areas: living area and production district. Considering the wind direction all year round, the living area is arranged on the east side of the production area, so that the production area is close to the bridge on the west side of the site, which shortens the transportation distance within the site. Sporadic material and tool warehouses and transportation are arranged in the production area from east to west. Wharf, lifting and transportation wharf, steel structure processing workshop, sand and gravel storage yard, cement warehouse, concrete mixing station, Panyu Bank also set up a water construction trestle on the east side of the bridge. The sand, gravel and cement used for construction are all transported to the site by water and transported ashore by belt conveyors; the lifting dock is not equipped with fixed lifting equipment and relies directly on truck cranes or floating cranes to complete the lifting work; the finished cable storage yard is located in a large A maximum of 48 cable coils can be stored on the water construction steel platform of the barge and auxiliary pier.

In addition to a 50m'/h automatic mixing station each, the South and North Bank mixing stations are also equipped with a 4-in-1 0.4m small mixer. When constructing large-volume components, in addition to the construction site mixing station supplying materials In addition, it also relies on the supply of commercial concrete, whose transportation distance is about 15km. On-site concrete transportation is completed by mixer trucks, dump trucks, concrete pump trucks or trailers.

3. Construction technical measures

3.1 Basic engineering

The main bridge spans the Lijiao waterway of the Pearl River system, which is a tidal river with the average highest water level over the years. Huangji is 2.406m, and the average tidal range is 2.906. , the design average flow velocity is 0.97m/s, and the water depth at the 82# pier is about 10m. The bedrock at the bridge location is mud sandstone, with a large strength dispersion of 2.3MPa-23MPa, and the mudstone has the characteristics of softening when exposed to water; the covering layer is similar to most areas in Panyu, consisting of silt mixed with fine sand and medium coarse sand, with a thickness of 10 -20m.

The construction of l.sin bored piles and caps in the side piers and auxiliary piers of the cable-stayed bridge is relatively conventional, using non-circulating rotary drilling rigs and hanging box cofferdam construction. In the construction of 3.0m piles and large-volume caps in the main pier, low-cost and high-speed measures were adopted based on the existing equipment and experience:

(l) As for the casing, prefabricated reinforced concrete was used The inner diameter of the protective tube is 3.3m, and the wall thickness is 10cm. The protective tube is sunk using two measures: a 30t vibrating hammer and a self-made mud grab to catch mud in the hole. For geological conditions where the covering layer is silt mixed with fine sand, the protective tube can be lowered Sinking into strongly weathered rock faces.

(2) Hole formation comprehensively applies forward circulation, reverse circulation, secondary hole formation and other processes; hole cleaning uses both the forward circulation hole cleaning method of parallel mud pumps and gas lift reverse circulation. hole cleaning method. The main technical measures during the construction were flexibly organized around increasing the drilling speed and preventing perforation at the bottom of the casing. For example, when opening the hole, use forward circulation drilling, and switch to reverse circulation drilling after reaching a certain depth of the rock; use 1.8 for the first hole. After the m drilling rig drilled, the vibration and pressure were again grasped to protect the pipe, and the second hole was drilled using a 3.0 m drilling rig.

(3) For the underwater concrete pouring of the pile body, a single 30Cm conduit is used to pump small gravel concrete with a slump of 16-20cm to the funnel for pouring bucket by bucket, so that the concrete can be subjected to stress while ensuring the pouring time. Impact vibration, and it is easier to flow through the steel cage with a clear spacing of only 4cm.

(4) Pier No. 82 cap adopts steel plate cofferdam construction. The supports in the cofferdam are directly transformed from the bored pile construction platform and can bear force in both directions. Sand bags are thrown outside the weir, sand and stone powder are filled inside the weir, and then the water is drained directly to pour the cushion concrete. For the construction of high piles and large caps with a water depth of about 10m, this method shortens the preparation time for bored pile construction, avoids the most difficult underwater concrete bottom sealing work, and fully integrates the hydrogeological conditions on site.

(5) The 83# pier cap foundation pit excavation and maintenance structure adopts the method of vibrating and sinking the precast concrete casing. The diameter of the casing is 1.6m, the wall thickness is 5cm, and it is driven with a 30t vibrating hammer. 6m below the ground, the top of the casing is supported by Bailey beams, which can be used as an excavator walkway. The excavation adopts a step-by-step method, advancing section by section from both sides laterally to the center line of the bridge, divided into 6m sections. While excavating, 3m piles and shaped steel are used to support the bottom of the casing. After digging to the design elevation, sand cushioning and concrete pouring are immediately carried out. Cushion and dig forward for the next section. Under the geological conditions of saturated silt and fine sand, this method can excavate to a depth of 6m, while the casing maintenance structure only consumes 260m’ of 20# concrete, which is a very economical approach.

3.2 Main tower and main beam construction

3.2.1 Construction method

The main tower and main beam are constructed using the cast-in-place section method. In addition to the beams being poured in two steps, the tower body is constructed in 4.5m sections with horizontal construction joints. Although horizontal construction joints increase the difficulty of formwork processing, pumping concrete is necessary for towers with large slopes; above Except for the 0# and l# blocks and the cross-tail section which are cast on the bracket, the remaining sections are constructed section by section on the hanging basket using the balanced outrigger method. The length of each section is 6m and the amount of concrete is about 15om' . For the main beam construction, the side spans were cast in advance on the supports and the mid-span single cantilever cast-in-situ construction method was compared. This method was rejected based on three reasons:

(1) The bracket cost is higher, which is higher than that of the hanging basket;

(2) The construction of the mid-span control main beam is always Construction period;

(3) The line shape of the main beam needs to be determined in advance and cannot be adjusted section by section like on the hanging basket.

3.2.2 Construction technology equipment

Three types of vertical transportation equipment, including construction tower cranes, construction elevators and concrete pumps, are used in the construction of the main tower. The maximum lifting capacity of the tower crane is 160KN. In order to ensure the lifting radius and attachment safety of the tower crane during the construction of the double main beams of the main tower of the wide bridge, the tower crane is arranged on the center line of the bridge. At the same time, in order to maximize the use of existing equipment, both elevators and concrete pumps adopt secondary The relay transportation method, especially the use of 2 straight climbing elevators instead of inclined climbing elevators, saves equipment investment costs.

The construction formwork of the main tower column adopts turning formwork. The turning formwork consists of 4 sections of 1.5m high steel formwork. After each construction, one section is turned over and the bottom 3 sections are kept, and the top section is retained as the interface mold. , the template is divided into blocks and a set of templates can be used for the lower, upper and upper tower columns. In order to facilitate basic operations such as formwork installation and steel bar binding, a tower column construction scaffolding platform is set up according to the height of the lower, middle and upper tower columns and construction characteristics:

(1) The lower tower column platform is directly supported by earth mounds The platform is based on the platform and is built with profiled steel and bamboo wood materials;

(2) The middle tower column adopts a self-designed integral light climbing frame. This climbing frame utilizes the cross-bridge dimensions of the frame itself. and fulcrums to enhance the stability of the frame against overturning. The frame consists of upper and lower horizontal space trusses surrounding the tower columns and connecting lattice columns between the two-layer row frames. Supporting corbels are arranged on all four sides of the frame body, which are supported on the embedded parts of the poured tower columns. The total weight of the frame body, the self-weight of the formwork and other construction loads is within the range of the fulcrum. A 4-layer horizontal scaffolding platform is set up on the frame as needed. The total weight is 22t and can bear a construction load of 25t, which meets the special needs of construction on large slopes to the tower. The climbing frame can climb with the floor slab or independently. Then lift the formwork;

(3) The upper tower column is the only upright section of the whole tower. Considering the need for cable extension and shock absorber installation in the future, a simple scaffolding platform is adopted. The method is to install the tower on the completed tower. The county pre-buried the I-beam beams and set pedals on the beams.

Heavy-duty brackets are used in the construction of the main tower beams, and the brackets are in the form of beam pillars. The support base is the Lux Tower cap; the load-bearing beams are Bailey beams; the columns are made of 55cm high-strength prestressed concrete tubes, and every six groups are supported by column hoops and connecting villages to form a lattice column. The choice of this column form avoids the problem caused by the difference between the temperature rise of the steel column and the concrete tower column, thereby avoiding the forced displacement of the fulcrum, which is important to ensure that the beam concrete does not suffer from early cracking.

The construction of the main beam 0# and 1# blocks and the end section of the side span also uses beam-pillar heavy-duty brackets, and the bracket materials are the same as the main tower beams.

The 104 cantilevered 6-meter-long standard sections of the main beam are cast-in-place and use a cable hanging basket to ensure that the internal force and elevation of the main beam construction can be effectively controlled. The hanging basket absorbs and develops the existing domestic The cable hanging basket technology has achieved the following technical results:

(l) Researched and designed a steel anchor box. The anchor box has comprehensive functions. On the one hand, it serves as the anchoring notch for the stay cable on the main beam; on the other hand, it serves as a temporary connection structure between the stay cable and the hanging basket, realizing a space pull cable; at the same time, it also serves as a cable sleeve on the beam. The positioning base of the tube and the hanging basket are horizontally restrained along the bridge direction, which not only facilitates the positioning of the sleeve on the beam, but also transfers the horizontal component of the stay cable on the hanging basket to the completed main beam.

(2) In addition to the hanging basket itself that can be raised and lowered by 0.3m, the top form of the bridge deck and the inner form of the main beam can also be raised and lowered by 2.2m. This enables the cross beams to be cast integrally with the side main beams and bridge decks to meet the design requirements for limiting stress on the bridge deck without hindering the forward movement of the hanging basket.

(3) The width of the hanging basket exceeds 40m, and the 37.7m wide section including the beam is poured in one go.

During the construction of the side-span closed section, the side-span hanging basket is set back 4.0M, the cast-in-place bracket at the end is used to lengthen it longitudinally, and then the sling is used to connect the cantilever end of the bracket to the cantilever end of the main beam to form a semi-sling. The bracket is used to cast the closed section vertically on the semi-suspended bracket.

The construction of the mid-span closed section is completed by using a hanging basket in the mid-span. First, remove one upside-down basket and move the other hanging basket forward. Use a sling to hang the cantilever end of the hanging basket. After removing the hanging basket, Festival. The hanging basket becomes a simply supported platform supported on both sides of the closed section by its own C-shaped structure and slings, and the mid-span closed section can be poured on the hanging basket.

3.2.3 Control measures for stability, internal forces and deformation during construction

For bridges constructed using the cast-in-place segment method, the structural system undergoes multiple transformations to form the final structure. During construction, it is necessary to control the stability, internal force and deformation of each state of the bridge structure and each load condition; it must also meet the design requirements for the final geometric dimensions and dead load internal force state of the bridge structure; at the same time, attention must be paid to the construction structure itself stability, internal forces and deformation. These three are often connected and guaranteed by each other.

Construction of large-slope tower columns of Panyu Bridge. Three means: stiff steel frame, temporary tie rods and temporary braces are used as control measures for stability, internal force and deformation during construction:

(l) Stiff steel frame is installed on the upper, middle and lower tower columns It is set in the middle and is mainly used to resist the overturning force generated by the current pouring section of steel bars and concrete. Due to the inclination of the middle tower column, this overturning force reaches 14000kN·M

(2) Temporary tie rod In the setting of the lower tower, 3 channels are installed. The tie rod material is O32 cold-drawn grade IV steel bar. Before the construction of the main tower cross beam is completed, the tower column acts as a cantilever beam to bear force. The tie rod is used to control the concrete stress and stress of the lower tower column. The tower columns were deformed. After the construction of the cross beams was completed, the cross beams and the lower tower formed a portal-shaped frame, and the tie rods were removed only at this time.

(3) The braces are set on the middle tower column, with 7 braces installed. The braces are made of Bailey beams and new bridges. Before the construction of the intersection section of the middle and upper towers is completed, The middle tower column acts as a cantilever beam to bear force. On the one hand, the braces are used to control the stress of the concrete in the middle tower and the deformation of the tower column. On the other hand, it can be used as an attachment structure for the construction tower crane and elevator. After the construction of the intersection section of the middle and upper towers is completed, the middle tower column will form Triangular rigid frame, in this case the struts are only used as attachment structures for the tower crane and elevator.

When the tower column construction is completed, the final tension or jacking force in the temporary tie rods and braces must be equal to the horizontal component of the tower column's mesh weight, ensuring that the lateral internal force of the tower column when the tension and braces are removed is equal to the force of the first landing. The internal force, tension force or jacking force when installing the tension and support rods must be calculated from the completed construction state of the tower column using the inversion method.

The main beam construction adopts temporary consolidation measures of towers and beams to transfer the unbalanced moment during the beam construction process to the main tower. The towers, beams, and cables during the symmetrical cantilever construction process are as a whole. The overturning stability of the external statically determined structure is entirely guaranteed by the strength of the tower columns. Therefore, at this stage (before the side spans are closed), the construction unbalanced load is strictly controlled and a variety of observation methods are used (such as cap settlement and tower top deflection). ) as the main construction measure, and temporary wind-resistant cables are used to ensure wind-resistant stability.

The control of internal forces and deformation during the construction of the main beam is ensured by strict construction control work. For each suspended main beam segment, the construction control team provides the empty basket formwork elevation of the hanging basket before pouring. And the pulling cable force of the hanging basket corresponding to the specific amount of concrete pouring. The initial pulling cable force to the final pulling cable force are calculated according to the limited C-shaped hook reaction force. During the pouring process, the elevation of the front end of the hanging basket changes up and down, but the final pulling force after the pouring is completed The elevation of the hanging basket behind the cable is the same as the elevation of the hanging basket after the initial pulling cable and before pouring. That is, during the concrete pouring process, the pulling cable force is determined according to the principle of "the elevation of the main beam remains unchanged" or "the reaction force of the C-shaped hook remains unchanged". After the poured section reaches the specified strength and the main beam is prestressed, the hanging basket is lowered and the pull cable is converted into a formal cable anchored directly to the concrete main beam. At this time, the cable is stretched for the last time. It is the tension force calculated according to the method of formal assembly and disassembly after parameter correction. In theory, after tensioning according to this force, there is no need to adjust the cable.

3.2.4 Measurement and positioning methods during construction

Three technical measures are mainly formulated for construction measurement and positioning: one is the position setting out of the cast-in-situ section of the main tower in the space; The second is the spatial positioning of the hanging basket during the suspended casting construction of the main beam segments; the third is: the setting out and positioning measures of the space cable-stayed anchor sleeves on the main tower and main beam.

(l) Main Tower In order to ensure that the inclination deviation of the main tower is not greater than 1/3000, and at the same time try to facilitate construction, after accuracy analysis, we adopted a polar coordinate direct stakeout plan. A high-grade precision triangulation network was established on the construction site, a forced alignment measuring station was established, and a high-precision total station was used for direct setting out, which not only met the design requirements, but also avoided the inconveniences of other methods such as the "big roof method".

(2) The positioning requirements for the sleeve on the tower are very strict and must be strengthened in two aspects. First, establish an axis control on the main beam block 0# with a higher precision than the triangular network. network; the second is to decompose the positioning of the sleeve into several items. First, accurately locate the rigid skeleton, and then accurately calculate the position of the sleeve on the skeleton sleeve positioning base. Use the axis network to mark the center and mark it on the skeleton. Mark the corresponding position of the sleeve according to the calculation, and the final positioning of the sleeve becomes a simple task of making the two marks coincide.

(3) Construction of main beam hanging basket and sleeve on the beam. During the construction of the main beam, the measurement and setting out of the entire section and the positioning of the sleeve are carried out together. First, fix the sleeve, formwork and hanging basket. knot, and then use the axis network on the bridge as the control basis, use jacks to push and pull the hanging basket front and back, squeeze left and right, and lift up and down as adjustment means to accurately position the hanging basket, and at the same time complete the positioning of the template and sleeve on the hanging basket. , so that the work procedures can be reduced and the overall control effect can also meet the requirements.

3.3 cable installation

The cable installation work is adapted to the construction method of the cable hanging basket. The cable is dragged from the bottom of the bridge to the bridge deck through the winch, and is first placed on the bridge deck. Place the pan, and then the anchor end of the stay cable is first connected to the pull cable steel anchor box placed on the bridge deck. The pull cable steel anchor box is then connected to the hanging basket through high-strength bolts. Finally, the tension end of the cable is connected to the main tower through hoisting and jack pulling.

The cable installation of this bridge is completed by tower crane, winch, probe rod, soft traction equipment and bridge deck truck crane. Compared with the existing domestic planar cable pull cable hanging basket hanging method, because the cable and The temporary connection method of the hanging basket is different. When the anchor end of the cable is connected to the hanging basket, there is no need to use jack equipment and extension screws. Instead, the steel anchor box is connected to the hanging basket with high-strength bolts.

The cable is initially used as a pull cable for the hanging basket. It can transfer part of the weight of the poured concrete directly to the main tower, reducing the burden on the hanging basket and the completed cable and beam structure, and transferring the weight of the main beam during the construction process. Negative bending moment is controlled within the allowable range. After the bolts connecting the anchor box and the hanging basket are removed, the stay cable is converted into a formal cable stay between the beam and the tower.

4. Construction organization measures to speed up the progress

The Panyu Bridge cable-stayed bridge is a cast-in-place prestressed concrete structure. The total concrete engineering volume is shown in the following table: The design of this bridge is It is a plan with a long construction period, but the construction period required by Party A for this bridge is very urgent. Therefore, the construction plan and construction organization must consider the overall progress requirements. In addition to requiring early strength of the concrete, the method to strive for the construction period also needs to consider increasing the number of working areas and try to carry out construction as much as possible. Some possible parallel assignments. Since this bridge has many large-sized and large-volume components, one-sided requirements for early strength of concrete can easily bring side effects of hydration heat. Therefore, during the construction of this bridge, more attention was paid to the organization of parallel operations during construction, and the following measures were taken:

(1) During the construction of the main tower foundation on the water, the construction of 3.0m bored piles was operated in parallel with the steel sheet pile cofferdam. The technical measure of transforming the bored pile platform into a support within the cofferdam provides the possibility for such parallel operations. , during the actual construction, the cofferdam and bored piles were completed almost at the same time, saving a lot of time.

(2) The construction of the main tower foundation pit enclosure structure on the shore is carried out in parallel with the 3.0m bored piles. After the 3.0m bored piles are partially completed, the prefabrication, sinking and drilling of the protection will be carried out. After the piles are completed, the foundation pit can be excavated.

(3) The handling of 3.0m pile quality accidents is carried out in parallel with the cap construction. Under the premise that the reinforcement measures for the 3.0m pile above the water have been fully demonstrated and affirmed, on the one hand, the core pulling of the 3.0m pile and the defective parts are carried out For press-fit repair, on the one hand, the cap is poured, and the post-poured portion is reserved at the position of the defective pile on the cap. After the pile repair is accepted, the reserved part on the cap is poured, so that the construction of the cap will not be caused by the repair of the pile body. Strong and delayed.

(4) The lower tower column and main tower beam support formwork work are carried out in parallel. This can be implemented as long as attention is paid to the overall layout of the lower tower column construction tripod and beam support layout.

(5) The construction of the middle tower column shall be carried out in parallel with the cast-in-situ construction of the main beam 0# and l# block supports.

(6) The assembly of the hanging basket and the dismantling of the main beam 0# and l# block brackets and the main tower beam pipe pile brackets are carried out in parallel. These pipe pile brackets prevent the hanging basket from being assembled in the elevated position. If you wait for the brackets to be removed before assembling the hanging basket, the construction period will be delayed by 15 days. We set up the Bailey beam bracket at a position that does not hinder the removal of the pipe pile bracket. The hanging basket was assembled on the Bailey beam bracket. After the pipe pile bracket was dismantled, the rail flat car on the Bailey beam bracket was used to move it along the bridge. Hang the basket to the vertical lifting position.

(7) Tower crown construction and main beam cantilever casting are carried out in parallel.

(8) Use the maintenance period of the main beam to complete the work of laying out the cables and connecting the cables to the anchor box. After the hanging basket is in place, the anchor box can be connected to the hanging basket, saving time on hanging the rope. Full preparations must be made when taking the above parallel operation measures, and in addition to technical measures, necessary safety management measures must also be taken.

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