Construction technology of CFST arch bridge of Jianghan Third Bridge in Wuhan

Construction Technology of Steel Pipe Concrete Arch Bridge of Jianghan Third Bridge in Wuhan Yang Qihai, Qiu Guoping (Sanqiao Department, Ministry of Railways, Huadu 510800, China) The bridge type is novel, the structure is complex, the technical content is high, the construction is difficult, and the construction adopts the series-new Process, new method. This paper briefly introduces the steel pipe arch truss section hoisting and concrete pumping jacking construction technology of the main span steel tube arch bridge of Jianghan Third Bridge. The process has achieved great success and good economic benefits, and it is worthy of promotion and reference in similar engineering construction.

1 Overview The main bridge of Jianghan Third Bridge in Wuhan City has a net span of 280.0m and a steel tubular concrete truss tie-bar without hinged arch bridge. The bridge is located in Hanyang Qingchuan, and Hanshui is the father. The total length is 302.926m, the width is 20.0m, and the two-way four lanes. The structure of the bridge shows opinions.

The upper structure of the bridge is mainly composed of the main arch of the concrete-filled steel truss, the boom, the tie rod, the beam and the longitudinal beam (see). The main arch of the concrete-filled steel tubular truss is provided with two arch ribs, and the arch rib is an equal-section truss with a height of 5.5 m and a width of 2.4 m, mainly composed of 4 The erection of the main span steel pipe arch truss section is carried out by the cable hoisting of the cable hoisting and hanging cantilever. After the bare arch is assembled, the welded head slab is fixed, the arched foot groove concrete is used, and the structure is converted into a hingeless arch by the two hinged arches; The buckle is gradually relaxed step by step, and concrete pumping is carried out. The concrete pumping adopts a single-tube symmetric pumping lifting and one-to-top construction method. This paper focuses on the pipe truss section hoisting and concrete-filled concrete pumping construction process.

2 Steel pipe arch truss section hoisting 2.1 hoisting plan The bridge is located in the downtown area of ​​Wuhan, which is a typical urban bridge. The steel pipe arch hoisting scheme is optimized by technology, construction, demolition, transportation and economy, and is selected from many schemes. The cable hoist is used to pull the shackle to hang the cantilever assembly construction plan. The tower height is nearly 110. 0m, which is a space high tower frame structure in which the cable tower and the buckle tower are combined into one (see). The cable crane is a three-span continuous cable hoist (Hanyang) +290.126m+134.00m (Hankou). There are 1 group on the upper and lower sides. Each group of 2 sports cars has a total of 4 sports cars. The maximum hoisting weight is 1200kN. The weight of each sports car is 300kN. Each group of two-two hoisting weight is 600kN, and the upstream and downstream hoisting weight is 1200kN. The tower root adopts a consolidation type, which aims to make the structure itself resist a certain displacement, so as to achieve no horizontal wind, reduce demolition, and save investment. the goal of. The buckle and anchor cable are made of ice 5mm high strength and low relaxation steel stranded wire harness and OVM anchor. The truss section is manufactured by the factory and hoisted by the waterway to the bridge. This hoisting scheme combines the construction features of arch bridges, cable-stayed bridges and even suspension bridges. It is the essence of Jianghan Third Bridge with high technical content and difficult construction.

Lifting and arranging of steel pipe arch truss section 2.2 Lifting sequence and construction steps According to the structural characteristics of the arch bridge and comprehensive consideration of various factors and construction practice, the determined lifting sequence is: first Hanyang, Houhankou, symmetrical on both sides, first upstream, downstream, upper The downstream is symmetric and welded to the cross braces to form a stable structure. The hoisting construction steps are as follows: the arch section is factory acceptance, the arch section is under the river, the transportation, and the positioning cable hoisting sports car is moved in position. ※The jacking, the shackle, the anchor cable, the hoisting, the seat, the opposite point, the joint bolt Tighten the ※ pull buckle, anchor cable, adjust the arch axis, tension the tie rod, loose hook ※ measurement and inspection, and then adjust the cycle hoisting until Helong, joint plate welding.

2.3 Implementation points and measures Due to the large weight of the steel tube arch truss section, the cable hoist cannot be longitudinally moved during lifting and can only rise and fall vertically. After the arch section is delivered to the construction site, it should be stopped below the lifting point and firmly positioned with the positioning ship. Due to the limitation of navigation conditions, the lifting time of each section should not exceed 4 hours. Therefore, all preparations should be fully prepared before lifting. The arch section should be sleek and slow when lifting, in case the action is too large, causing the tower to change rapidly, which will affect the buckle and anchor system and the installed steel pipe arch. At the same time, it is strictly forbidden to be installed by the suspended steel pipe arch truss segment. Steel pipe arch. In any case, the horizontal displacement of the tower shall not exceed 20cm. When adjusting the axis, the offset shall be adjusted first, then the elevation and mileage shall be adjusted, and the elevation may be pre-lifted by 5~8cm; the offset shall be adjusted by the transverse cable wind, and the elevation and mileage shall be tensioned. Buckle and anchor cable adjustment; buckle and anchor cable are all pulled at one end, the Other end is fixed with P anchor, the tension end is on the tower, and the fixed end is respectively on the steel pipe arch segment and the rear anchor; the tension jack should be in advance Correction, symmetrical when tensioning, grading tension, graded load is preferably 50~100kN. The buckle and anchor cable strands are protected by rubber sheath to prevent electric welding and oxygen cutting burns; because the buckles and anchor cables are externally prestressed, and the stress is within (0.2~0.4)as, it is small, to ensure the buckle, The anchor system is safe and reliable, and is anchored with double anchor heads to prevent loosening of the clips.

2.4 Steel pipe arch truss arch ribs Helong steel pipe arch truss arch ribs Helong uses a single rib integral hoisting dragon, first upstream, rear and downstream, and finally connected to the vault. Helong is difficult, but it is beneficial to the main structure. There are two sections in the Helong section, with an upstream section length of 29.809m, a downstream section length of 29.652m, a section weight of 57.04t, a vault cross-length of 16.400m and a weight of 29.20t. When hoisting, it should be completed as much as possible, and the interval should not be too long. .

2.5 Construction method When the steel pipe arch truss section is hoisted, the temperature of the hoist should be controlled at 17*C according to the design requirements, and it is allowed to float between 12~22*C. Because the Helongkou is the upper and lower inverted "eight" mouth, in order to facilitate the "embedded" Helongkou of the Helong section, the following measures must be taken when lifting: 1 select the lower limit of the temperature of the closed dragon; 2 pull the tight buckle, The anchor cable will raise the steel pipe arch truss at both ends of the Helong section by 5 ~ 10cm; when the Helong section enters the Helongkou, the oblique hanging oblique insertion method is adopted; after the Helong section enters the Helongkou, the 100kN guide chain should be used to adjust the point immediately. Align the bolt holes at one end of the Hanyang shore and put on half of the bolts at intervals, tighten them, and then wait for the temperature to rise until the bolt holes in the Han port can be adjusted. Immediately put on the bolts, tighten them, and finally, wear the other half at the same time. Bolts and tightening; after the Helong section is installed, the structure realizes the system conversion, which changes from the cantilever state to the two-hinge arch structure; at this time, the thrust of the arch is sharply large. Therefore, the tension of the front of the dragon, the time of the dragon and the time of the dragon must be tensioned. The rod balances the arch thrust to ensure structural safety.

2.6 Quality Index Before and after the lifting of the steel pipe arch truss section, the construction technical quality indicators (see Table 1) are controlled within the allowable range, especially the arch axis deviation, buckle, anchor cable force and tower displacement. It effectively guarantees the safety of the structure during the construction phase.

Table 1 before and after construction of the technical quality indicators of each test point elevation error / tm two ribs symmetry point elevation deviation / tm single rib symmetry point elevation deviation / cm arch rib plane deviation / cm Helong front Helong 3 3 2 3 concrete pipe pump Send 3.1 concrete pumping scheme Steel pipe arch truss in the main arch of the arch rib and the upper and lower slabs must be filled with C50 compensation shrinkage concrete, 8 string pipes, 4 slabs, metering concrete 2306.3m3, where the string tube is filled The concrete is 1818.7m3, the single pipe is filled with 227.3m3, the concrete is filled with 487.6m3, and the concrete is filled with 121.9m3. The concrete pumping adopts the single-tube symmetric pumping lifting and single-top construction method. The pumping jacking horizontal distance is nearly 150.0m, the height is up to 70. The chord pumping is completed in 8 times; in addition to considering the symmetry of the two banks, the pumping should pay attention to the symmetry of the upper and lower sides, strictly abide by the principle of symmetrical loading, pumping sequence see. The concrete is mixed with the concrete factory set up on site and directly supplied for pumping.

3.2.1 Pumping concrete characteristics Concrete is self-contained concrete, which does not vibrate during perfusion, and has good compactness after coagulation and hardening; it has compensating shrinkage, ie compensating shrinkage concrete, its micro-expansion rate> shrinkage rate; good pumpable Sexuality, in the process of pumping and ascending, it can always maintain excellent performance state; the bleeding rate is small and the fluidity is large, which is convenient for the concrete to automatically expand and fill; under high temperature construction conditions, it can be solidified and hardened without cracking.

Concrete material composition: FDN-9001 high-efficiency water-reducing plasticizer; Grade I fly ash; No. 525 ordinary cement; expansion agent EA; Bahezhong 6~3.0, mud content d gravel, continuous grading, crushing value < 8% needle-like content <6% mud content 3.2.3 concrete mix ratio The weight of each component of concrete per cubic meter of concrete is: cement 470.0kg; sand agent 75.0kg; fly ash 60.0kg; composite superplasticizer 7.86 Kg. 3.2.4 Actual mixing concrete performance index 0cm; extended 3.3 construction method One concrete factory on each side of the bank, equipped with two 500ml forced mixing machines to ensure the concrete output is more than 40.0m3 / h, each pumping within 6h Completion, extension shall not exceed 8h. The pump shall be used for m. For the domestic bridge construction, the rare fm slab pumping is divided into e4t times. The Weilish Blish West German UBSC14 type uses 2 sets of spare 1.c sets; the machine is set on the abutment, the pump The pipe is covered along the arch shaft once, and the diagonal line is arranged to minimize and avoid the use of the elbow. The radius of the pipe at the outlet of the pump and the inlet of the steel pipe should be greater than 1. 0m. The length of the short pipe of the inlet and outlet connecting pipe should be greater than 1.0m. When mixing concrete, the metering should be accurate, the mixing should be uniform, and the net mixing time should be greater than 2 minutes. Before pumping, it should be set at 0.5m in the middle of the splicing plate. 4 Conclusion Jianghan Sanqiao steel pipe arch truss section hoisting began on August 25, 1999, the same year November 24, Helong, lasted nearly 3 months, after deducting the impact of the production and supply of steel pipe arch segments and navigation, shipping and other factors, The actual hoisting time is less than 2 months; the hoisting better solves the influence of the cable tower and the buckle tower on the hoisting of the steel pipe arch. The concrete-filled concrete tube pumping began on April 15, 2000 and ended on May 28 of the same year. It lasted less than one and a half months, and the construction was extremely smooth without any abnormality. It can be seen that the construction and selection of the concrete-filled steel tubular arch of the main bridge of Jianghan Third Bridge is more practical and has strong guidance and applicability.