MSS滑移模架施工工艺及技术控制Proceedings of the fourteenth annual meeting of the society of bridge and structural engineering, Chinese society of Civil EngineeringChinese Institute of civil engineering of bridge and structural engineering institute proceedings of the fourteenth annual conference of the Nanjing Yangtze River Bridge project. Construction technology and technical control of MSS sliding die setNanjing Yangtze River Bridge 50m bridge constructionLiu Jizheng, Qi Lujie, Wang Xiaoshan(Shandong Province Traffic Engineering Corporation, Nanjing Yangtze River Bridge Project Department)[Abstract] this paper briefly introduces the structure and composition of MSS slip and its application in construction. Sliding formwork; construction technology; deflection control I. General Situation of the projectNanjing Yangtze River Bridge North Bridge bridge upper structure for 16m*30m and 5m*50m PC with variable cross section continuous beam bridge. The whole bridge section is composed of two single box and single chamber beam sections separated from top to bottom, and a central partition cover plate is arranged in the middle. among5 * 50m approach bridge in30m approach bridge and the main bridge transition section, the bridge is located in land and water, land a hole, four holes on the water, the peak water level 7m. Therefore, it is very important to choose an optimum construction scheme.Two, scheme comparisonBased on the bridge position of 50m bridge, two schemes should be adopted for the construction of superstructure: 1. Supportconstruction, set up a full support with one hole on the river bank, insert four hole copper pipe pile in water, and build a steel pipe pile support. Adopt the construction without scaffold. That is, the introduction of foreign advanced equipment - sliding die frame for construction.The first construction plan is the traditional construction method of our company. There are abundant construction experience, the technology is easy to control, but this scheme for water construction, heavy workload, Jixietaiban, the economy is not reasonable, the construction schedule is not ideal. Second kinds of construction schemes, advanced construction equipment, with the leading domestic level, but this kind of equipment is used for the first time our company, the technology is difficult to control, for the construction of water in the middle span cast-in-place continuous beam bridge is particularly suitable for. Synthetic manifold reasonsIn consideration of Nanjing bridge project of the company ultimately decided to use no scaffolding construction that the introduction of MSS sliding formwork system.Three, sliding mode profilesThe MSS slide beam introduced by our company is mainly composed of six parts, the bracket (Niu Tui), the main beam (Gang Xiangliang), the crossbeam, the back beam, the external die and the internal die. Each part is equipped with an internal hydraulic or mechanical system. The structure and function of each component are as follows:1. bracketBrackets are commonly called brackets and triangular structures. Through the reserved hole (diameter: 80cm*100cm) insert attached to the pier on the pier. Its role is to supportthe main girder, the main girder load transfer to the pier on the bracket. A sliding block is arranged on the top face of each bracket. It is equipped with two pairs of 20t horizontal automatic moving hydraulic jacks.A 450t vertical automatic hydraulic jack, a longitudinal moving hydraulic jack. The main beam is embedded in the overhead travelling crane. In order to reduce the friction between the main beam and the crown when moving in longitudinal direction, the crane is equipped with a poly four vinyl slide board, and the main beam is positioned in the direction of the slab, the direction of the bridge and the vertical height through the three hydraulic system.2. main beamThe sliding girder is a pair of steel box girders. The section size of the steel box girder is wide: 2.0m, height: 3.0m, length 64.8m, divided into six sections - 10.7m + 4*0.8m+10.9m). The joints are connected by friction type high strength bolts. In order to make the main beam slide along the bridge from the upper hole to the next hole, the front and back of the main beam is equipped with a bridge type nose bridge, long 21m. The main girder is a load bearing component of the sliding mode, weighing about 350t. The main beam is provided with a window, and the crossbeam is provided with a main beam; a vertical hydraulic jack, a mechanical jack and a horizontal jack are arranged in the window. The steel beam is hinged with the main beam through the pressure system, and the main beam is subjected to the construction load of the external, internal and upper structure transferred by the crossbeam.3. beamThe whole sliding mode has 18 pairs of cross beams, the beam is "H" type, the steel structure size is 35cm*90cm*900cm, eachpair of beams for pin connection, the beam spacing 3.6m, the beam has no pin hole, in order to install the external mold support. The cross beam can be adjusted vertically and transversely through the pressure system in the main beam. 4. external dieThe outer mold comprises a bottom plate, web plate, rib and flange component. The floor plate is directly laid between the two adjacent transverse beams and corresponds with the crossbeam. The connecting direction of each pair of bottom plates along the direction of the cross beam is connected by common bolts. The outer template joint is in the outer mould central axis. Total floor width 6.5m. The web, rib and flange also corresponds with the beam, and through the template bracket and the supporting beams are provided to install. 5. internal modelSet along the internal mold mold shifting system including the template, electric car, rail and beam model. The transverse transportation and installation of electric car to complete the. The electric car is equipped with a hydraulic system, through which the hydraulic system to complete the installation of internal die.Four 、 construction principle and process flow of Slipform The installation and adjustment of slip and slip mold MSS template is "hydraulic" as the driving force to the hydraulic jack to work in control equipment, hydraulic control device, the hydraulic jack push, thus completing the adjustment in place, the cross beam and the inner and outer mould installation and adjustment. Before construction, first of all, the preparation of the construction along the technical program. The purchase of special equipment, machinery and equipment, leasing large lifting equipment. Sliding mode constructionaccording to the following procedures: (Niu Tui) bracket assembly, girder assembling and related construction design tools in place, lifting bracket girder hoisting and installation, beam main beam in place, laying floor, installation of formwork support, installation and construction of the outer web and flange plate, plate, die. Five, slip form site specific assemblyThe quality of field assembly of slip form directly affects the quality, schedule and construction safety of box girder construction. Therefore, when assembling,According to the design drawings along the die, in strict accordance with the "steel construction technical specifications" for operation, for high-strength bolt joint surface, careful inspection, one by one surface treatment, so as to achieve the proper coefficient of friction. High strength bolt connection, take the initial and final material express, repeated operation, make every bolt meet the design of torque wrench torque value, and periodic calibration, ensure the connecting force strength, preventing engineering accidents, affecting the quality of construction safety and construction (with) parts must be removed or treated qualified rear can use. Bracket assembly on site: because the bracket is triangular and has a certain height, the site assembly is unstable and should be supported by a triangular support. The lifting bracket placement, pier reserved hole, with the top bracket by leveling leveling, so that the crane on the surface smooth slip. In order to prevent the carriage capsized in the force, each of the bracket is composed of thread to pull, embedded pier, so the installation bracket should be on the other side of unilateral temporary placement of a carrying pole, wear thread tension, to prevent instability.The main beam is installed; because the main girder is self important, the whole hoisting is difficult. During construction, the crane is hoisted at two times, and temporary support is arranged in the span to carry out the closure assembly. This requires the temporary support of the elevation of accurate measurement and slope, so that the steel beam in the middle of the smooth docking, assembly.After the main girder is assembled, the crossbeam is placed at the main beam window, and the main beam is placed under the influence of the hydraulic system, and the bridge is positioned accurately in the direction of the hydraulic system when all the beams are installed. A total station or theodolite is installed at the center of the pier, the bridge axis is released, the crossbeam is adjusted according to the axis of the bridge, and the bottom plate is laid with a pin, and the axis deviation is controlled within 5mm. Then, the installation of the web and flange plates.When assembling the slip form, the parts are required to be connected reliably. After assembly, the utility model can be safely and reliably checked, and can be used for the construction of the upper structure.Six 、 adjustment of template and elevation controlIn order to better set camber, this set of sliding formwork is designed with LCM formwork, and the design is supported by sheet iron. According to the actual construction practice, taking into account the quality of the cast beam body, we adopted the putty to add the curing agent to adjust the caulking and smoothing. As a kind of better mending joint material, it has good curing speed and high strength. It meets the requirement of construction specification. The quality of the cast beam is better.Elevation control: it is difficult for the construction of the sliding mode to reserve a certain degree of arch so that the beam can reach its design elevation as much as possible. Therefore, the source of the deflection value of the construction frame should be considered comprehensively; the theoretical calculation of deflection value should be accurate. The source of this set of sliding mode deflections has the following four aspects:(L) deflection value of concrete self weight (value supplied by manufacturer VCE company);(2) the deflection caused by the cantilever boom (without considering the weight of the sliding form) is calculated according to the 13mm (according to the triangle distribution) and adjusted accordingly when measured;(3) prestressed tensioning the camber, between the front and rear pivot part according to parabola distribution, parabolic center maximum deflection according to 20mm, the maximum cantilever deflection according to 13mm (according to triangle);(4) the deflection caused by the settlement of the bracket is calculated according to 10mm.Through observation, deflection deflection calculation and the actual construction process of the accord, but slightly different, so in the construction of a hole, careful observation of each construction stage, measuring the deflection value changes, but compared with the theoretical calculation, so as to guide the construction of the next hole; reduces the construction error, guarantee the construction of the girder elevation and the design elevation deviation is reduced to less than 1cm.Seven, the construction process of box girderThe 50m approach box girder adopts equal section beam, the beam height is 2.6m, the box girder roof thickness is constant, the web and floor thickness change, the bridge width is 32m, and the upper and lower separate single box single chamber section, the straight bridge. Box girder construction from the beginning of the shore, each construction at the next gap in the gap 8m (L / 6 near) continuous construction, construction process flow chart shown in figure 1.Because the construction operation is cyclical, in order to improve work efficiency and speed up the construction process, each process should be compact and connected. At the same time, the preparation of the next process is effectively shortened, and the construction period is shortened.During the construction, the first pouring hole, the template before and after the pivot in before and after the piers, and other casting hole. In order to ensure the smooth construction joint, located in front of the pier top pivot, after the pivot on the cantilever end has been pouring completed, the rear suspension rod lifting beam main beam, as a support.The pouring of concrete adopts one casting construction method, and the two step is carried out. Pour the bottom and the web first and then pour the roof. And start from the end of the cantilever to prevent excessive deflection deformation of the main beam span.In the end of construction need to move across, first sliding off the rack, demoulding, lift the connection beam according to pin horizontal slip, outside, avoid the pier, then the longitudinal slip to the next hole. The main beam with a connecting rod, a crossbeam and a template is unstable when moving; in order to achieve balance, the concrete counterweight is arranged outside the main beam.Eight, concluding remarksThe construction of the project adopts the sliding formwork method, with a high degree of mechanization. The complete process such as formwork, steel bar, concrete and tensioning technology can be completed in the mold base. At the same time as the construction work period, and not subject to the interference of external factors, not only for the project management, but also can improve the quality of the project, to speed up the construction schedule, shorten the construction period, the construction period is the fastest single hole with only 12 days to complete. And it is crucial to complete the construction of 50m approach bridge before the closure of the main bridge.The movable scaffolding system requires a set of equipment and accessories, in addition to a considerable amount of steel, it needs a set of mechanical power equipment and automatic device, a large investment, in order to improve the efficiency, must solve the assembly and scientific management problems.The construction of 50m approach bridge adopts this set of moving formwork, which solves these two problems. The main components along the die are assembled, which can be used in bridges of different spans, different bridge widths and different shapes, so as to enlarge the service surface and reduce the construction cost. In the construction of the professional construction team, organization of scientific management, the fixed operation, do use equipments, and pay attention to maintenance and maintenance equipment, give full play to the ability to use the equipment, and achieved good economic benefits.Reference[l] Ministry of communications, First Highway EngineeringBureau. Highway Construction Manual (bridge and culvert). Beijing: people Communications Press, 1985[2] fan Lichu. Prestressed concrete continuous girder bridge. Beijing: China Communications Press, 1985.1。
