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Application of ZLD Automaticly Continuous Launching System in the Construction of Prestressed Concrete Composite Box-girder Bridge with Corrugated Steel Webs

Dou Yong-zhi*, Sun Chang-jun, Wei Fu-tang

Liuzhou OVM Engineering CO., Ltd., Liuzhou, Guangxi, China

Abstract: The incremental launching construction method firstly is applied to the prestressed concrete composite girder bridge with corrugated steel webs and the bridge belongs to Zhengzhou Longhai Road Fast Track Project at Chang-zhuang reservoir in domestic. Under this background, ZLD automaticly continuous launching system is applied to the prestressed concrete composite girder bridge with corrugated steel webs and the construction scheme design, related construction technology and key points is introduced. Engineering practice shows that the advantage is synchronous control, automation, flexible construction, the force of incremental launching can be adjusted according to level of reaction force and deformation at the pier top. The construction efficiency, safety and reliability is improved for launching engineering, and it has a wide application prospect.

Keywords: automaticly continuous launching system, prestressed concrete composite box-girder bridge with corrugated steel webs, incremental launching construction method

Citation: Dou Yong-zhi, Sun Chang-jun, Wei Fu-tang, Application of ZLD Automaticly Continuous Launching System in the Construction of Prestressed Concrete Composite Box-girder Bridge with Corrugated Steel Webs. American Journal of Civil Engineering and Architecture, 4 (1). 6-16. January 2016. doi:10.12691/ajcea-4-1-2

1. Introduction

At present, incremental launching construction method of prestressed concrete composite box-girder bridge with corrugated steel webs has been in a few foreign bridge applications [1,2]. By the end of 2013, it is a bridge firstly based on incremental launching method to construct a bridge in domestic and the bridge belongs to Zhengzhou Longhai Road Fast Track Project at Chang-zhuang reservoir in domestic, see Figure 1. Incremental launching construction method of prestressed concrete composite box-girder bridge with corrugated steel webs has three innovations as follows. Firstly, it is the first time to the types of box-girder bridge incremental launching construction in domestic. Secondly, it is the length of the most for the launching length of single box-grider bridge. Thirdly, it is the first time to technologies that the inclined web is used for the box-girder design, see Figure 2, and the corrugated steel webs is useded for making a guide girder, the blank of technology is filled in domestic.

Figure 1. The incremental launching construction’s panorama of prestressed concrete box-girder with corrugated steel webs

Figure 2. The section of prestressed concrete box-girder with corrugated steel webs(Units: mm)

The upper structure of main line viaduct is prestressed concrete composite box-girder with corrugated steel webs. And the upper structure construction is used for incremental launching construction method. Two opposite linked respectively is launched from both ends to the YP10 pier. The prefabricated platform of girder and temporary piers is located in the connection ends of two span. Girders is divided into three types. The types are guide girder section, launching section and cast-in-place section.

The section of guide girder is located in the first span of girder sections at the front part. The length is 35 m for guid girder. The corrugated steel webs is used as main structure of guide girder in order to save material consumption of guide girder steel. Launching section is consist of one 27.5 m segment and several 50 m segments. The cast-in-place section is located in curve segment. It is maked use of prefabricated platform support in order to reduce difficulty of incremental launching construction in the curve.

The total length of prestressed concrete composite girder bridge with corrugated steel webs is 940 m. It is divided into YU01 and YU02. The length of YU01 is 450 m. It is divided into nine segments. Five segments of launching are included (excluding the guide girder segment). The length is 262.5 m, and the rest are cast-in-place segment. The length is 187.5 m, see Figure 3. The length of YU02 is 490 m. It is divided into ten segments. Six segments of launching are included(excluding the guide girder segment), the length is 312.5 m, and the rest are cast-in-place segment, the length is 177.5 m, see Figure 4. The incremental launching distance of YU01 and YU02 is 575 m.

Figure 3. The incremental launching figure of YU01 bridge girder (Units: m)

Figure 4. The incremental launching figure of YU02 bridge girder (Units: m)

The construction scheme of prestressed concrete composite box-girder bridge with corrugated steel webs multi-point synchronous launching is designed in this project combined with ZLD automaticly continuous launching system. The flexible steel hinge lines, supporting system, traction anchoring system, slide system, rectifying system, LSD hydraulic launching jack group, computer control and hydraulic synchronous launching in principle are used. Prestressed concrete composite box-girder bridge with corrugated steel webs is prefabricated in turn each segment combined with prefabricated platform, and each segment in turn is slipped in place by slide systems on the pier top.

2. Brief Introduction of ZLD Automaticly Continous Launching System

ZLD automaticly continuous launching system is manufactured by Liuzhou OVM Machinery Co., Ltd. It is mainly composed of automaticly continuous launching jack, automaticly continuous launching pumping station, console, travel switch and some flexible steel wire, etc [3]. The automaticly continuous launching jack is composed of two jacks in longitudinal series as an indivisible integer. The relationship of jacks, pump and console is as shown in Figure 5.

Figure 5. The relationship of jack, pumping stations and console

The control process is as follows. The travel switch is used as an motion sensing element for ZLD automaticly continuous launching system. The signal of jack piston position is transmitted to the console by travel switch. The signal is carried on a logical combination by the console. And the control signal is passed to the automaticly continuous launching pump station. The movements of the corresponding automaticly continuous launching jack is controlled by pump station through the solenoid valve. A closed loop system formes the process. The various actions of the jack can be adjusted automatically.

The main characteristic of ZLD automaticly continuous launching system is continuity and synchronization. It is continuity that a large object level is launched continuously and uniformly tens of meters or even hundreds of meters away or horizontal rotating any angle. It is synchronization that several jacks work synchronously. That effects of the project is affected by repeated start and repeated stop. It is advantaged over when multi-points incremental launching. And the speed of construction is greatly accelerated.

3. Scheme and Implementation of Multi-points Synchronous Lanunching Construction

3.1. Overall Scheme

The incremental launching of YU02 bridge girder is introduced mainly as follows in this paper.

The weighs of YU02’s launching segment is about 7047 ton (including guide beam)in the project. The longitudinal slope of 0.5% is existed along the bridge when launched. The coefficient of starting static friction is taken to be 0.1, The maximum horizontal force of jacking is taken to be 740 ton when launched. The maximum launching span is taken to be 50 m. Temporary piers are not arranged between the permanent piers. And multi-points synchronization incremental launching construction method is taken by incremental pulling. Firstly, the slide system is arranged on the temporary pier and permanent pier which is located in prefabricated platform. The reaction supporting system is arranged on the permanent pier of YP11 to the permanent pier of YP16. Two automaticly continuous launching jacks which model is ZLD100, see Table 1, are arranged on one pier. Twelve jacks for launching are arranged on six piers. The total horizontal launching force is distributed according to pushing stiffness of each permanent pier. It is included that YP16 pier and prefabricated temporary pier platform is connected into a whole through a link rod, and it has larger pushing stiffness as the main pier to share the larger horizontal launching force. The preformed hole is respectively provided with traction anchorage system in the top and bottom board of prestressed concrete composite beam with corrugated steel webs. And it is connected to reaction supporting system by flexible steel wires. The girder is pulled to realize the launching and sliding. The tensile strength of steel wires is 1860 Mpa. The nominal diameter of steel wires is 15.24 mm. The number of steel wires is eight. In addition, it is required to carry out the dynamic active rectification of the girder when launched, and the limit position system is set up on the permanent pier of YP11 to the permanent pier of YP16.

Table 1. The technical performance of ZLD100 automaticly continuous jacking

Six sets of ZTB automaticly continuous launching pumping station are controlled by a computer console, see Table 2. Two automaticly continuous launching jack of ZLD100 is drived synchronously by each pump to pushing and slip. At the same time, a field controller is set up on each pier, a pumping station and two sets of launching jacks are controlled by a field controller with a touch screen display. At the same time, all the data are transmitted to the console. The operation panel is equipped with emergency stop switch, remote or local selection switch, alarm indicator, etc. In the remote control condition, stop operation can only be carried out by the field control box. In the local control state, the field control box can be used for any one or more of the jack on the pump station to carry out automatic and manual operation.

Table 2. The technical performance of ZTB automaticly continuous pumping stations

3.2. Design Key Points of Multi-points Synchronous Launching System

Dynamic foundation of multi-points launching construction is the first design key point as follows [4].

[picture] | (1)

In which,

- Jack Jacking Force of i Pier

- Supporting Force of i Pier

- Slide Friction Coefficient of i Pier

- Total Weight of Lanuching Box-girder

- Longitudinal Slope Design of Lanuching Box-girder

Symbol "+" indicates the uphill, and symbol "-" indicates the downhill.

The physical meaning of the expressions is as follows. The launching device is dispersed in each bridge pie and temporary pier to distract the resistance of each pier horizontal reaction force. The girder begans to be moved when the sum of launching force is equal to the sum of drag.

Synchronization of equipment is the second design key point as follows.

The circuit of ZLD automaticly continuous launching system pump station is designed to ensure that two jacks are controlled by a pump on the same pier top. Pump valve is used to make sure that the flow of two jacks is same. Overflow valve is used to make sure that the limit of jack is not exceeded. On single pier synchronization and safety of two jacks is ensured. In addition, the synchronization of the equipment is monitored by the jack, displacement and pressure monitoring. It is achieved by real-time control of the computer.

Control strategy of continuous launching is the third design key point as follows.

The control strategy is based on launching force, the displacement of the pier top, the speed of the synchronous control, load tracing and balanced control. Based on the supporting force and horizontal displacement of the piers top, the launching force and speed of the launching jack is used as the controlled variable, and the force and the velocity of two control is realized. In order to avoid the phenomenon of girder sudden movement, the method of centralized control, hierarchical pressure and differential limit is adopted [5]. The coefficient of static friction is 0.1, and the coefficient of dynamic friction is 0.05. Horizontal launching force is expected to be calculated by the coefficient of static friction and the coefficient of dynamic friction. When the horizontal launching force is loaded until the girder is moved, the horizontal launching force is gradually reduced to the load level to adapt the variation of the friction coefficient, and the synchronous launching of each pier is achieved.

At the same time, the horizontal force of the pier top is kept in a controllable range. Guarantee measures are as follows.

Firstly, limit pressure control of single pier launching device is used to ensure that the launching force is not overrun.

Secondly, the active limiting measures are used to adjust the displacement. When the deviation of displacement at the pier top reaches the setting value, the launching force is automatically adjusted by means of horizontal limit device at the pier top and real-time monitoring of displacement at the pier top. So the displacement of the pier top is kept in a controllable range.

The main points of the design are to ensure that the design specification and construction safety requirements is meeted by the deflection of the beam axis, the displacement of the pier column, the stress state of the beam and the pier column.

3.3. Incremental Launching Construction Process

The process flow of incremental launching construction is as shown in Figure 6.

Figure 6. Process flow chart of incremental launching construction

3.4. Main Incremental Launching Temporary Facilities

3.4.1. Prefabricated Platform Slide System

Prefabricated platform is the site of precasting girders and launching transition, see Figure 7. It includes the platform of pouring segmental girders, the platform of processing template, reinforcing bar and steel cables, and the platform of installing guide girder. It is composed of.bored pile foundation, foundation platform, steel pipe pile supporting pier, slide pier of steel pipe pile and distribution beam of pile top, lifting system of bottom templet, bottom templet system, support connection system and so on.

The slide syste.m is arranged on slide pier of steel pipe pile. The slide system consists of slide beam, stainless steel plate, MGE plate of polymer material [6], see Figure 8. Slide beam is welded into a box structure by steel plate. Before and after the slide along the bridge is processed into slope type to facilitate feeding MGE plate. The stainless steel plate is tiled on the slide beam plate on the course of outsourcing, and is fixed by welding. All welded joints need to be polished. The grease is evenly coated on the slide beam.

The thick of MGE plate is 35 mm, it is provided with a storage tank side and is tiled on the slide beam. The side of sliding friction is composed of the stainless steel surface and MGE surface. Four MGE plates are arranged on the slide beam and the size of each plate is 0.6 m by 0.6 m.

Figure 7. The figure of prefabricated platform(Units: m)

Figure 8. The slide system of prefabricated platform’s elevation(Units: mm)

3.4.2. Permanent Pier Slide System

The slide system of permanent pier is set on the embedded parts of bearing block. It is welded and fixed on embedded parts. Slide system is the same as prefabricated platform’s slide beam, see Figure 9, Figure 10. Six MGE plates are arranged on the slide beam and the size of each plate is 0.6 m by 0.6 m.

Figure 9. The slide system of permanent pier’s elevation (Units: mm)

Figure 10. The slide system of permanent pier’s side elevation (Units: mm)

3.4.3. Reaction Supporting System

Reaction supporting system of jack is set in the permanent pier. And it is connected by six row prestressed reinforcement with pier. Pier is set the pre-buried hole of reinforcement.

Reaction supporting system is composed of the reaction bracket, triangle supporting frame of jack, prestressed reinforcement, see Figure 11. The section of reaction bracket is designed into the shape of the groove back-to-back, it is easy that traction steel wires are passed through continuous launching jack. And the bracket support is set to strengthen the local cantilever end of reaction bracket. Each bar of jack triangular supporting frame is welded together by double channel steel, and it is welded into a triangular frame by the connecting plate. The nominal diameter of prestressed reinforcement which is connected with the pier is 32 mm, the yield strength of prestressed reinforcement is 785 MPa. It is pre-tensioned to guarantee that reaction bracket and pier shafts are respectively anchored by locking when installation.

Figure 11. The reverse force holding system’s elevation(Units: mm)

3.4.4. Traction Anchoring System

The traction anchoring system is set up in the end of prestressed concrete composite girder with corrugated steel webs. The channel is pre-buried in the box-girder roof and the box-girder floor. At the same time, the location should be avoided in the layout of prestressed reinforcement.

The traction system is composed of the traction anchor column, the upper beam, the traction steel wires, the anchoring device and so on, see Figure 12. The section of traction anchor column is designed into the shape of the groove back-to-back, it is easy that traction steel wires are passed through the anchoring device. And the bracket support is set to strengthen the local cantilever end of traction anchor column.

The traction anchor column is connected to the upper beam by the fastening bolt, and is fixed on the box-girder roof. The upper beam is used to share the force in vertical component when launching. Anchorage, clip and clamp device is composed of anchoring device, the anchoring device is produced by Liuzhou OVM Machinery Co., Ltd.

Figure 12. The traction anchor system’s side elevation (Units: mm)

3.4.5. Limit Position System

Limit position system is arranged on each side of the permanent pier. And it is connected with pier by two row prestressed reinforcement. The pre-buried hole of reinforcement is set in the pier.

Limit position system is composed of the reaction bracket, guide wheel, prestressed reinforcement, correcting jack and so on, see Figure 13. The section of reaction bracket is designed into box section. The guide wheel is connected to the reaction bracket by the bolt. It is easy that the correcting jack is installed to realize correctiong construction. The nominal diameter of prestressed reinforcement which is connected with the pier is 32 mm, the yield strength of prestressed reinforcement is 785 MPa. It is pre-tensioned to guarantee that reaction bracket and pier shafts are respectively anchored by locking when installation.

Figure 13. The limiting and rectifing system’s side elevation (Units: mm)

3.5. Main construction points

3.5.1. The Slide System, Reaction Supporting System, Limit Position System and Traction Anchorage System in Place

Firstly, the slide system on slid pier is used for doubling as the pouring bottom template of prestressed concrete combination girder floor with corrugated steel webs in prefabricated platform. It is assured that the seams around the bottom template are flush, closely sealed and strengthened by support. It is necessary to avoid producing dislocation in the seams when pouring concrete floor, thus packing skateboard on the slide surface and push sliding construction is affected.

Secondly, the construction of permanent pier is completed, slide system at pier top, reaction supporting system and limit position system can be installed. The slide system of pier top is welded with the embedded parts of pier top, and is fixed. The elevation of slide surface meets to requirements of incremental launching construction. The reaction supporting system of pier, limit position system is connected to piers by prestressed reinforcement. And the prestressed reinforcement is anchored by stretching.

Thirdly, the prestressed concrete composite girder with the corrugated steel webs is completed and the bottom template is completed in the prefabricated platform. Then the traction anchoring system can be installed. It is required to ensure that the center of the traction rope and the jack is in a straight line when the installation of traction anchorage system.

3.5.2. Installation of ZLD Continuous Launching System

The jacks are hoisted in place according to the number. The guide, safety clamp and sensing device is installed in accordance with the provisions of the construction. Note is as follows.

Firstly, jack and the base application is fixed with bolt to facilitate disassembly and assembly, and it is ensure that the center hole of the jack, reaction supporting frame, and traction anchor column reserved hole is in a straight line. The center deviation is not more than 5 mm, or the steel hinge lines are blend due to torsion when incremental launching.

Secondly, each corresponding line is connected according to the design number between the jack and hydraulic pump. It is necessary to check and verify the connection after the completion of the connection. It is ensure that the pipeline is not mistaken.

Thirdly, the control room is placed under the bridge, and the control signal is sent to the top of the platform by cable. Electrical wiring and cable should be laid and fixed to avoid the staff to trample or avoid hard damage.

3.5.3. Installation of Steel Hinge Line

When the jack is in place, the platform is put on the bottom of the jack to install steel hinge lines. Note is as follows.

Firstly, the clip on up holder of the jack is opened with a hydraulic pump station, and the clip of safe holder and guiding holder are supported.

Secondly, the steel hinge lines are passed through the comb pallet, safety holder, launching jack and guiding holder according to the number of sequentially. The length of stretching out guide holder is about 1 m, and the clip of holder is pressed.

Thirdly, steel hinge lines are intervally arranged to the left and to the right. It is easy to pass steel hinge lines with guide device of wire.

Fourthly, steel hinge lines which is passed through the reserved hole of reaction force supporting frame are combed by comb pallet. And it is anchored in the holder of traction anchoring column. It is ensure that the steel hinge lines are not intertwined and are not cross. The length of stretching out anchor plate is more than 50 mm. The screws of anchor plate are fastened.

Fifthly, the torsion angle of the holder is adjusted so that the steel hinge lines has no integral torsion.

3.5.4. Pre-tightening Steel Hinge Line

Steel hinge lines must be preloaded with single chain before force. The pre-tightened force is about 1.5 ton for each one. It is ensure that the stress of each strand is basically the same. The jack is adjusted to manual launching state after pre-tightening, and the whole bundle of steel strands is pre-tightened by jack.

3.5.5. System Debugging

The installation of the system is completed, and the machine is tested. It is ensure that the operation which is in the manual process or automatic process is correctly corresponded with operation of the device.

When online is debugged, the pumping stations is started and the manual operation mode is selected. The actuators action of stretched cylinder or shrinking cylinder is controlled in the console panel. And it is checked if the action is correct. The detecting element of stroke detecting device is adjusted to be normal for the contact and detection of the detection device.

The manual test of system is completed. The automatic mode system is selected to check action coordination and synchronization of each jack. If it does not meets to the design requirements, the reasons is found seriously and troubleshooting is solved. Until the system's action meets to the full coordination, it is showed that the system debugging is normal qualified.

3.5.6. Prepare Work before Incremental Launching

The hydraulic system, circuit system, anchor fixture system, control and display system and steel hinge line is thoroughly and carefully checked before launching. And it is recorded in table. Also prefabricated platform is checked to ensure that the longitudinal and transverse contact is completely removed between main structure of launching and around the temporary structure.

3.5.7. Pre-launching Adjustment

Firstly, the main jack are controlled back to the start position. And the manual mode of launching is ready.

Secondly, the system is controlled by manual operation. The pump pressure is adjusted at a time. The jack is gradually increased the load by 20%, 40%, 60%, 80%, 85%, 90%, 95%, 100%. It is observed and recorded at any time when loading.

Thirdly, the prestressed concrete composite beam with the corrugated steel webs is launched to the distance of 50 mm by manual mode. And the structure is observed in the progress.

Fourthly, it is checked whether the structural weld and structural deformation is normal.

Fifthly, it is checked whether all the equipment is normal.

3.5.8. Formal Launching Process

Firstly, after the slide of main girder is started by manual operation mode which launching system is controlled, it is converted to the automatic operation mode which the main girder is automaticly continous launching. The horizontal displacement on the pier top and pressure sensor readings is controlled when launching. The horizontal displacement on the pier top is determined by total station survey readings. And the horizontal displacement on the pier top meets to the allowable range of structural safety. The horizontal displacement of the pier top is kept in close contact with the pump operation personnel at any time to guide the pump operation. At the same time, the pump operation is adjusted by the pressure sensor readings at any time.

Secondly, if the setting error of the control system is exceeded for the synchronization error in the process of automatic launching, the system will be automatically adjust. If the maximum error of the control system is exceeded for the synchronization error in the process of automatic launching, the system will be automatically entered the emergency stop and waited for the adjustment. When the adustment is completed, it is entered pre-launching state and automatic launching is started again.

Thirdly, the influence of the synchronous control error on the component is observed during incremental launching. The maximum value of oil pressure and the minimum value of of oil pressure are recorded during incremental launching. And it is monitored at the time whether the status of launching structure is in the specified range. The error is required to be dynamic correction when the error is occured.

Fourthly, the load, the structure state is monitored at any time during launching. And it is monitored at any time whether the push channel is open.

Fifthly, the axis shift of the main girder is monitored at any time during the process of automaticly continuous launching, If the main girder axis is deviated from the design axis to a distance of 30 mm, the the correcting jack located in the rear end of the guide wheel is started to active dynamic correction.

3.5.9. Implementation of Incremental Launching Project

On August 1st, 2014, first prestressed concrete composite girder section with steel webs is launched to the distance of 32.3 m. The length is 27.5 m, the weight of girder section is 910 ton. The average speed of launching is 8 m per hour. The launching process lasts eight hours. It is showed that the advantages is automation, simple control during construction process, stable and reliable to achieve the desired good engineering effect for ZLD automaticly continuous launching system.

4. Conclusion

ZLD automaticly continuous launching system is applied in the launching construction of prestressed concrete composite beam with steel webs. The efficiency of construction is greatly improved, and the construction period is shortened. Because its own characteristic is synchronous control, automation, safe and reliable, it is easy to control in the construction process. Therefore, the advantage is construction area of less, good overall structure, construction period short for the bridge launching construction method. ZLD automaticly continuous launching system has a wide application prospect.

References

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[2]   | Li Guang-hui, Zhang Jian-xun, “Incremental launching technique for construction of PC box-shaped girder bridge with corrugated steel web,” Construction technology (in China), 39(7). 118-120. July. 2010.
[3]   | Wei Fu-tang, Xie Yong-hong, Wei Yong-sheng, “Application of YDCLD automatic continous launching system in incremental launching construction,” Highway (in China), (2). 29-34. February. 2001.
[4]   | Dong Qi-jun, “Jacking construction of a continuous steel box beam,” Construction technology (in China), 34 (5). 20-22. May. 2005.
[5]   | Ren Ming-fei, Liu Xiao-xia, “Design and construction of prestressed concrete launching continuous grider in the flat curve for Dong Hai Bridge,” Prestress technology (in China), (2). 17-21, 34. April. 2005.
[6]   | Li Yan-zhe, Cai Hong-zhen, “Design and innovation on the incremental launching construction method for the Taohuayu Yellow River Bridge,” Construction technology (in China), 42(11). 69-72, 91. November. 2013.