RU2242559C1 - Method for cyclic movement of solid reinforced concrete bridge span in longitudinal direction - Google Patents

Abstract

FIELD: building, particularly erection of preloaded reinforced concrete span structure having different span types and cross-sections.

SUBSTANCE: method is used for erecting span structure above existent buildings, structures, service lines, deep ravines and other barriers arranged along bridge axis. Bridge has side walls or ribs, upper or lower plates and straight reinforcement arranged in upper plate and located from inner surface of side walls or ribs. Method of bridge movement to piers involves concreting span structure sections in concrete form; reinforcing thereof and connecting the first one of formed sections to launching nose having length equal to 50%-60% of that of span structure section to be connected with it; moving above section by push jack and connecting next sections; arranging tightened through bundle of reinforcement in side walls thereof and in ribs after all span structure sections installation in design position; connecting reinforcement of all span structure sections. Form is made of two parts having sliding blocks, namely the first, lower, block supported by four hydraulic jacks and used for concreting lower plate, and the second block used for concreting side walls or ribs and upper plate. Section form is arranged behind push jacks along one concreting section. Launching nose is connected to front span structure section by means of single strands tightened by single-strand jacks. Movement is carried out with the speed of 7.5-12.5 m/h with push jack force not exceeding half of vertical force created by lifting jacks additionally used for span structure section movement. Length of through reinforcement bundle is not less than summary length of three span structure sections.

EFFECT: reduced time for bridge building and carrying out special supplementary works in spans.

3 dwg

Description

The proposed method relates to the construction of prestressed reinforced concrete spans of various spans and cross sections. This method is especially effective when it is necessary to construct spans over existing buildings, structures, communications, deep ravines and other obstacles located on the axis of the bridge.

Known methods for constructing reinforced concrete spans of various lengths by the methods of hinged installation of prefabricated reinforced concrete blocks, hinged concreting in separate sections, mounting individual prefabricated beams with subsequent integration into continuity above the supports or near the supports, as well as the method of concreting the span on solid scaffolds cannot be applied when passing bridge routes over buildings, structures and other obstacles due to the limited construction height or the inability to arrange Mosti and crane equipment installation on an existing building.

The closest known method is the construction of a bridge, overpass, characterized in that it includes the construction of supports and at least one continuous along the span of forming at least one branch in the cross section of reinforced concrete longitudinal beams that perform on slipway of monolithic or precast-monolithic reinforced concrete by concreting in removable formwork section by section with reinforcement of non-tensile and tensile reinforcement with subsequent production using an advance backing nn-cyclic sliding of the sections until each of them is placed in the design position, while the tensioned reinforcement is placed in closed channels in the form of bundles, including those formed from wire strands (ropes), and / or rods, and / or tapes of high-strength material, including from metal, or metal, or high-strength carbon-containing or polymer filaments, with some of the channels being straight and part of the channels being curved or polygonal with a configuration and arrangement mainly in a vertical section in convexities and concavities corresponding to or proportional to the diagram of bending moments, the working reinforcement located in rectilinear channels is strained within each section before its sliding and moving from the slipway, and the reinforcement located in curvilinear or polygonal channels is pushed or stretched in the channels after sliding the span or the pushed branch of it and strain after the slide of all the sections forming the span, or its pushed part, or its branch, while the ratio the cross sections and / or the bearing capacity of the reinforcement, tensioned section by section, and reinforcement, tensioned after sliding into the design position of the entire overhanging part or branch of the superstructure, are taken as calculated. The slipway is made of base, racks, beam cage and formwork supported by jacks with concrete walls, which are placed along the edges and axis of the concrete section of the span, and steel sheets are laid on the top of the walls, the joints are welded, and the upper surface of the sheets is cleaned, ground and coated with antifriction grease, mainly silicone, plywood sheets are laid on top of steel sheets with a length shorter than the distance between the formwork and the additional support near it, and a width exceeding the width of the steel x sheets. Before concreting the sections, the channel formers are placed in the design position on reinforcing pads that are located at a distance from each other along the channel former, then they are installed in the design position of the anchor, bundles of high-strength strands are formed in the installed channel formers with the strands fixed in anchor devices, the channel formers are connected to anchor devices with sealing of all joints at the upper and lower points of the bend of the reinforcement to the transit additional drainage tubes are installed on the channel formers, and the transit channel formers are filled with plastic pipes to give the channel former more rigidity, high-strength strands are trimmed mechanically, and after concrete sections of the span structure are designed to be designed, high-strength beams are tensioned, while tensioned reinforcement is injected before or immediately after spans of the span section.

The tension of the beams of high-strength strands is produced by assigning the amount of tension for each section individually in accordance with the perceived load. When performing a section of plate-ribbed or box-shaped concreting, the sections of the superstructure on the slipway are made in two stages, on the first of which two ribs or ribs and the lower bottom of the box-beam are concreted simultaneously. When performing the section of the superstructure, the slab concreting of the section is carried out in one stage, for which the elements of the formwork of the section are mounted on the slipway. After concreting sections of the superstructure produce exothermic curing of concrete. The span slide is made by four jacks, which are installed in front of the abutment with the possibility of connection by means of four reinforcing bars with steel beams mounted in the span, and for sliding the first section of the span, two of the four rods are attached to the outback. The span is based on freestanding reinforced concrete racks of rectangular cross-section (RU No. 2208084 C1, class E 01 D 21/00, 2003).

The proposed technical solution does not require special auxiliary arrangements in the spans where obstacles are located, and can be carried out with a limited construction height of reinforced concrete spans, which is determined by calculation.

This is achieved by the fact that the method of cyclic longitudinal sliding onto supports of continuous reinforced concrete span structure of a bridge with side walls or ribs and an upper or lower slab and reinforcing in the form of straight beams in the upper slab and on the inner side of the side walls or ribs includes concreting in the formwork of the sections of the spans , their reinforcement and connection of the first of the manufactured sections with an outback, the length of which is 50-65% of the length of the span section connected to it, followed by a slide to the pushing house an atom with building up in the following sections, while the formwork is preferably made of two parts with sliding pillows: the first, lower, rest on four hydraulic jacks and are used for concreting the bottom plate, and the second is used for concreting the side walls or ribs and for concreting the top plate, the formwork sections are placed behind the pushing jacks along the length of one section of concreting, and the avanbek is attached to the front section of the span by means of single strands that are pulled in a single strand jacks, the slide is produced at a speed of 7.5-12.5 m / h, the horizontal force developed by the pushing jacks does not exceed half the magnitude of the vertical force created by the lifting jacks additionally used when sliding, and after placing all sections of the span in the design position in their side walls or ribs are placed prestressing transit beams of reinforcement, the length of which is not less than the length of three sections of the span, and produce the union of the reinforcement of all sections of the span.

The invention is illustrated by drawings, where:

figure 1 presents a diagram of the concreting of the first section and the installation of the outback,

figure 2 presents a diagram of the slide superstructure using advanceback and concreting the second section,

figure 3 presents a diagram of the slide superstructure using advanceback and concreting the third section.

Auxiliary arrangements with the proposed method of work are located outside the bridge dimensions:

- slipway polygon 1 with formwork for concreting sections of 2 spans;

- steel outback 3, which is temporarily attached to section 2 of the reinforced concrete span for a sliding period in order to reduce bending moments and transverse forces in the cross section of the span when sliding;

- a pushing device 4 for the longitudinal slide of sections 2 of the superstructure.

Reinforced concrete span in the same sections with longitudinal sliding experiences various (including alternating) forces. Therefore, a mandatory element of each stage of the slide is the installation or removal (sometimes both) of temporary high-strength beams, as well as the installation of transit prestressing reinforcement after the end of the slide on the supports. For a longitudinal slide, a device is used (for example, according to RF patent No. 2163276), including a group of jacks, some of which raise the span section, while others push it. In the span use channel formers (for example, according to patent No. 2178046).

Above each support 5, special side-bearings are installed, along which the span glides.

The method of cyclic longitudinal slide (CPN) consists in concreting individual parts of the span in place, with 1/3 or 1/2 of the length of the span located in a covered slipway polygon directly behind one of the foundations. Each concreted section of the “capture” of continuous span is prestressed before the slide. For sliding, special hydraulic equipment and supporting parts with a low coefficient of friction are used, along which the span moves over the intermediate supports. The technical advantages of this in situ concreting design include the following:

- the advantages of factory manufacturing are realized at the landfill due to the repeatability of work operations and the independence of work from weather conditions,

- excluded scaffolds, the assembly and disassembly of which is associated with a large investment of time, as well as the constraint of the existing movement,

- excludes frequent expansion joints in the span.

In this case, the cost of work depends on the cost of materials, wages and the cost of formwork. Reducing the cost of these components can be obtained by:

- repetition of similar work operations,

- reuse of easily assembled and disassembled forms and structures,

- pre-harvesting conventional and prestressed fittings,

- transportation of materials over short distances,

- good quality control of concrete work,

- protection of the work zone from weather conditions, which guarantees the performance of work strictly on schedule,

- the possibility of reuse of scaffolds and equipment in other works,

- reduction of labor costs and ensuring the highest control over work due to the concentration of most of the work inside the indoor landfill.

In general, the CPM method is applicable for the construction of bridges both on a straight line and on a curve of the same radius. The curve can also be in a vertical plane. Bridges constructed using this method have a length of 100 to 1200 m. However, the minimum bridge length should be about 300 m in order to absorb the cost of formwork and equipment and make this method competitive. It is not necessary that the bridge have the same spans. If one or two spans are longer than the others, the slide can be performed using temporary supports. The spans of 40-50 m are considered optimal spans. The value of end spans should be within 75% of the average spans. The magnitude of the central prestressing for the slide is very important, therefore, it is necessary to carefully select the cross section of the structure during design. The correct position of the concrete sections at the landfill and the provision of the exact height of the formwork are of prime importance for a successful slide. Formwork is usually made of two ready-made parts: the first for the bottom plate and the second for the side walls or ribs and the top plate. This separation guarantees a working weekly production cycle for one section of the superstructure and provides maximum performance, especially for large bridges. A separate integral formwork can be used with a corresponding reduction in the cost of the construction of the landfill, however, in this case, the work cycle will be 8 days to provide care for the concrete on the inner surface for 24 hours before concreting the top plate. The function of the central voltage is to ensure that the cross-section of the span perceives all positive and negative moments with any change in its position above the supports. Straight bundles in the upper plate and on the inner side of the side walls have sprocket butt couplings and are placed in each of two (of three) sections and provide the necessary longitudinal prestressing. The installation of beams in relatively thin upper and lower plates requires special anchoring. In some cases, with relatively large bridge spans (more than 50 m), the central prestressing force is too high for the last stage of construction. To get out of the situation, set temporary beams, which are removed after installation of the span in the final position. Transit beams are installed when the slide is completed and the span has taken its design position. These beams, the length of which reaches 90-100 m, depending on the spans of the bridge, are located in the side walls of the span with the location of the anchors on the inside of the box section for aesthetic reasons.

There are two alternative methods of cyclic longitudinal slide.

A}. Pulling method

This method uses conventional prestressing jacks and strand bundles that allow the span to be pulled by a frame fixed to the rear end of the penultimate section.

B}. Push method

This method uses synchronized jacks located under the span, which lift and then push the span due to friction between the steel of the jack and concrete.

The pushing method has significant advantages over the pulling method, the most significant is the ability to change the direction of movement at any time, for example, back up. This may be necessary, for example, due to extremely large friction on the supports at the moment of starting in cold weather, which causes large deformations of the supports. The ability to immediately change direction in this case is very important. It is necessary to take into account some issues related to the location of the pushing jacks, namely, it is very important to determine the acceptable size of the area for installing the pushing equipment: for anchoring the jacks used to transmit horizontal force, as well as the place for installing the brake shoes, which are steel plates on which the superstructure rests all the time, excluding the sliding time. The formwork is usually placed behind the pushing jacks along the length of one concreting section. This increases the vertical response to the jacks and balances the moment from the console.

When designing the supports, it is important to limit the horizontal force that affects the lower part of the supports to the maximum. In this case, the maximum permissible deviations of the support occur as a result of the effect of the maximum horizontal force and permissible friction. An electronic control system mounted in the upper part of the support and connected with jacking equipment accurately controls the deviations of the support and avoids their maximum value. The important thing is the correct placement of the supporting parts, taking into account the tolerances for the placement of flat jacks for lifting the span and placing the permanent supporting parts in the design position. For large horizontal forces (which arise when the second set of equipment is turned on at support N1), the combination of temporary supports is a possible solution for the perception of these forces.

The slipway range consists of one or two sites, depending on whether the span grip is concreted in one formwork or in two. The landfill is serviced by cranes, has a concrete plant and areas for the manufacture of reinforcing cages and the performance of prestressing structures. On the back of the formwork there is a paved area to protect the beams from possible contact with the ground. The roller system allows the beams to fit comfortably during the span sliding process. Usually the landfill is 15-20 meters away from the abutment. Between the landfill and the abutment are temporary supports with a distance between them of 6-7 meters and with sliding devices on them. According to the conditions of multiple turnover, the formwork is made of metal, wood is not used. The lower part of the formwork rests on four hydraulic jacks. On the sides (about 0.5 m), which also play the role of sliding zones, special guides are used, combined with neoprene-Teflon support pillows that provide a low coefficient of friction. Opening the side parts of the formwork, as well as the inner formwork (in the case of a box section) also performed using hydraulic jacks.

 The final number of prestressed beams in the case of applying the CPN method is 40% more in road bridges (in railways a little less) compared to the span concrete method in place. This is because, in addition to central prestressing, it is also necessary to produce structural stress in transit beams. The number of permanent beams can be reduced by introducing temporary beams that can be removed and reused in construction. In any case, the increase in the cost of prestressing with the CPN method is far overlapped by many other advantages and savings. For the prestressing device, beams of 100 tN of power are used for road bridges, and for railway bridges of 170 tN of power. The bundles are joined after 2-3 concreting hooks using couplings according to the patents of the Russian Federation No. 2094578, 2094577. The bundles in the top plate are wound onto drums so as not to interfere with the preparation of the next “grab”. Transit beams are located in the walls of the superstructure, their average power is 200-300 tN. These bundles have a length of 90-100 m to facilitate the task of freely pushing them into the channels, and have tension anchors at each end. The tension of these beams is performed after the final installation of the span in the design position. However, the beams can be pulled in advance if necessary, but in this case the channels must be filled with an aqueous solution of the anticorrosive compound, which must be washed out of the channel before injection.

Sliding equipment consists of, for example, two jacks, one of which raises the span, freeing it from the brake pads, and the other provides the push of the span. The speed of the slide is about 10 m / h, so a concreted area of 15-20 m in length can be pushed in 2 hours. Temporary support parts consist of a concrete slab with a stainless steel sheet attached to the upper surface to limit sliding friction. After the end of the slide, these supporting parts are replaced by constant ones, usually one comprehensively movable and one linearly movable. Glass support parts have been developed that can be used both temporary and permanent. These supporting parts consist of standard glass supporting parts with specially elongated top plates, which have on their surface a stainless sheet that provides sliding during sliding. After the end of the slide, these supporting parts work as permanent previously being combined with wedges.

The process of turning temporary supporting parts into permanent ones using flat jacks for these purposes becomes an easy operation if special supporting parts are used. The lateral guides are designed so that they can be installed at any time when sliding. These guides are connected to the supports using beams.

The manufacture of a box beam using two sets of formwork is carried out in the following sequence.

Monday

Morning. Lowering the bottom and outer formwork. High tensile reinforcement tension and slide.

After lunch. Cleaning and lubricating formwork. Beam preparation.

Tuesday. Installation of fittings and channel formers in the bottom plate.

Wednesday

Continuation of reinforcing the bottom plate. Installation of reinforcement for the top plate and walls. Concreting the bottom plate.

Thursday

Continuation of the installation of the reinforcement of the upper plate and walls, the installation of embedded parts and parts for prestressing.

Friday

Concreting of walls and top plate.

Saturday

Sunday

Curing. In case of low temperatures, steaming is used.

The advantages of the cyclic sliding method are that a team of 14 people makes a span section (15-20 m) per week.

Claims (1)

A method of cyclic longitudinal sliding onto supports of continuous reinforced concrete span structure of a bridge with side walls or ribs and an upper or lower plate and reinforcement in the form of straight beams in the upper plate and on the inner side of the side walls or ribs, characterized in that it includes concreting in the formwork of the span sections structures, their reinforcement and the connection of the first of the manufactured sections with an advance back, the length of which is 50-65% of the length of the span section connected to it, followed by pushing a jack with building-up in the following sections, while the formwork is made of two parts with sliding cushions: the first, lower, rely on, preferably four, hydraulic jacks and are used for concreting the bottom plate, and the second, which is used for concreting the side walls or ribs and for concreting the top slabs, and the formwork of the sections is placed behind the pushing jacks along the length of one section of concreting, and the avanbek is attached to the front section of the span using single strands that are tight They are called single-strand jacks, sliding is carried out at a speed of 7.5 - 12.5 m / h, the horizontal force developed by the pushing jacks, not exceeding half the magnitude of the vertical force created by the lifting jacks additionally used when sliding, and after placing all sections of the span in the design position in on their side walls or ribs are placed prestressing transit beams of reinforcement, the length of which is not less than the length of three sections of the span, and combine the reinforcement of all sections of the span th structure.

Images