Abstract：To ensure the successful erection of thirteen-span 900t box girders at the approach section of Tongling Yangtze River Bridge along the Hefei-Fuzhou High-speed Rail. The girder moving device is specially designed and manufactured for the purpose of moving the box girder to the other end of the portal piers horizontally. And the relevant construction procedures are formulated. The design focuses on the sliding track，bearing slide block and pushing mechanism of the device. The goal is completing the erection work of thirteen-span 900t box girders safely and with good quality within the specified construction period.

Keywords：Horizontal movement of 900t box girder at the top of the pier；equipment composition；design and calculation

中圖分類號(hào)：U445.55+9 文獻(xiàn)標(biāo)識(shí)碼：A 文章編號(hào)：1004-7344（2018）17-0143-04

1 Project Overview and Design Requirements

The approach section of Tongling Yangtze River Bridge along the Hefei-Fuzhou High-speed Rail is a parallel design of four railway lines. One side is the Hefei-Fuzhou high-speed double track rail while the Lujiang-Tongling double track rail on the other side. Every 2 box girders form a span，and 13 span of the approach section are built on portal piers. During the erection process of 900t box girders，one box girder on the Hefei-Fuzhou high-speed rail line can be normally erected and the other box girder on the Lujiang-Tongling rail line must be moved horizontally on top of the pier after the successful erection of bridge girder erection machine in order to be put into place.

The height of the bridge pier is 40m. The weight of the box girder is 900t where the length，width and height of the box girder are 32.6m，12m，3.4m. In order to adapt to the frequent movement on different piers，the girder moving device should be characterized by convenient assembly and disassembly and is able to adapt to the complex construction site environment. The box girder cannot be adjusted longitudinally after horizontal movement on top of the pier，thus it requires high precision alignment. And the horizontal moving devices at the adjacent piers must be provided with high degree of synchronization and unilateral adjustment capability.

2 Construction Scheme for Girder Moving Work

2.1 General Construction Process Scheme

The construction scheme for transportation and erection of box girder for the approach section of Tongling Yangtze River Bridge along the Hefei-Fuzhou High-speed Rail is divided into six sections to complete：

（1）Mounting the horizontal moving devices on the adjacent piers and fixing them with anchors.

（2）Placing the box girder of the Lujiang-Tongling rail line on the horizontal moving device by bridge girder erection machine.

（3）Adjusting the box girder longitudinally.

（4）Moving the box girder horizontally to the other side of the piers by the horizontal moving device.

（5）Adjusting the box girder horizontally and put it in place.

（6）Removing the horizontal moving device and mounting it on the next portal pier.

（7）Erecting the box girder of the Hefei-Fuzhou high-speed rail line by bridge girder erection machine.

（8）Shifting the bridge girder erection machine to the next span and prepare for the following erection work.

2.2 Construction Procedure

The box girder on the Lujiang-Tongling rail line should be erected by the bridge girder erection machine and moved horizontally towards the right side of the portal piers in advance. Then the box girder on the Hefei-Fuzhou high-speed rail line can be erected. The specific construction procedure is as follows：

（1）Fixing the hydraulic jacking device

Four hydraulic jacking devices should be fixed on the adjusted piers according to the requirement of the Longitudinal and horizontal lifting positions before landing the girder in position. The function of the hydraulic jacking devices is to make sure the horizontal moving devices can be disconnected with the box girder and removed successfully. And the hydraulic jacking devices can adjust the elevation of the box girder to the designed elevation for grouting work.

（2）Mounting the horizontal moving devices on the adjacent piers

①Levelling

Taking one point every 1M within the range of the slide and using the level gauge to retest the elevation of the pier platform. And adjusting the height difference of base cushion according to the retest data to ensure the bottom of the installation position of the same pier is in the same elevation. The position of the whole slide needs to be leveled with mortar.

②Fixing the sliding track

The sliding track should be put in place by crane according to the pre-drawn installation locating line on the pier platform. Then using chemical bolts to fix the sliding track on the pier platform. 10 chemical bolts should be fixed on each side of the sliding track.

③Lifting the slide block，hydraulic pump and the horizontal hydraulic pushing cylinder to the pier platform by crane and fixing them on the sliding track.

④Assembling and testing. The slide block，horizontal pushing cylinder，hydraulic pump and the power line should be fixed on the sliding track in sequence. No load testing operation should be conducted before moving the girder.

（3）Placing the box girder of Lujiang-Tongling rail line on the girder moving device.

①M(fèi)easuring the elevation difference among the slide blocks on the same side with the level gauge，and leveling them with sheet iron plate according to the measuring results. It is to make sure all the slide blocks on the same side are on the same level.

②Girder lifting

Lifting the box girder to a certain position where is 2～5cm to the top of the girder moving devices by using bridge girder erection machine.

③Alignment and Landing

Adjusting the box girder longitudinally according to the longitudinal position line and then landing the box girder slowly to the support units of the girder moving device，leveling the box girder with the cylinder.

（4）Adjusting the box girder horizontally and putting it in place.

①M(fèi)arking scale on the sliding track，and making sure the horizontal moving distance of both ends of the box girder are the same. And when the difference is more than 50mm，the movement should be stopped and the difference shall be adjusted. The girder moving operation can be continued after adjusting，and when the box girder is in place，the box girder should be aligned horizontally with the girder moving device.

②Removing the girder moving device and Elevation adjustment. Jacking up the box girder with the hydraulic jacking device after the alignment operation and then the girder moving device can be removed. Adjust the elevation to make sure the mortar layer thickness is in the allowed range.

③Grouting the support saddle after the box girder is in place，and the erection work of one box girder is completed.

（5）Removing the Girder Moving Device

The girder moving device should be adjusted back to the initial position and then disconnect the power line and cut off all the chemical bolts. Then the girder moving device should be disassembled from top to bottom in sequence. The sliding track needs to be dragged to the side of Hefei-Fuzhou High-speed Rail Line by using motor hoist and then the whole girder moving device will be lifted to the next pier by using crane.

（6）Erecting the box girder of the Hefei-Fuzhou High-speed Rail Line by bridge girder erection machine.

①Reverting the beam of the bridge girder erection machine to its initial position. And continue with the girder feeding and erecting work on the side of Hefei-Fuzhou High-speed Rail Line.

②Removing and fixing work of the hydraulic jacking device. The hydraulic jacking device will be removed when the mortar strength of the support saddle of the box girder for Lujiang-Tongling Rail Line meets the requirements. Then the hydraulic jacking device will be fixed on the side of Hefei-Fuzhou High-speed Rail Line according to the same requirements.

③Erecting the box girder of the Hefei-Fuzhou High-speed Rail Line on the same pier by bridge girder erection machine.

④Shifting the bridge girder erection machine to the next span and preparing for the following erection work.

3 Composition of the Girder Moving Device

Two units of girder moving devices were fixed on the two adjacent piers perpendicularly to the erection direction of box girder. The sliding tracks on the two adjacent piers should be fixed in the same level.

（1）Sliding track for horizontal movement. Each unit of sliding track consists of 5 segments and the length of the sliding track is 23m. The sliding track is made of 40mm steel plate and welded with 150mm high guide baffle on both sides. A cylinder joint should be welded on the outside pf the guide baffle every 2.5m. 10mm thick teflon plate is laid inside the inside the sliding track as the friction pair.

（2）Bearing slide block. The front and rear bearing slide block are placed on the sliding track for supporting the box girder，being connected by the connecting rod. The teflon plate is arranged at the bottom of the slide block as friction pair that forms a friction system with the sliding track，and the cylinder joints are welded on both sides of the rear slide block，which function as the thrust points.

（3）Pushing mechanism： Each set of the pushing mechanism is composed of two hydraulic pushing cylinders，one hydraulic pump and the connecting hydraulic pipes and valves. The cylinder is mounted between the external joint of the sliding track and the joint on both sides of the rear bearing slide block，and the hydraulic pump is connected to the oil cylinder with the hydraulic pipe and the valve. The pushing mechanism is placed on the pulley and it moves along with the box girder during the pushing process.

The total horizontal stroke length of the device is 14. 3m and the horizontal moving speed is 40cm/min.

4 Design Calculation of the Girder Moving Device

4.1 Sliding Track for Horizontal Movement

In order to ensure the flatness requirement during the horizontal movement of the box girder，the sliding track for horizontal movement should be installed on leveling cushion. The cushion under the sliding track should be paved with the quick drying mortar and covered with thin steel plate for leveling. The sliding track should be anchored inside the concrete at the pier platform and all the connecting joints should be overlapped and fastened with bolts.

（1）The bottom plate of the sliding track is made of 40mm steel，which transfers the supporting force to the concrete of the pier platform directly and therefore the strength calculation is unnecessary.

（2）Strength calculation of the cylinder joint on the sliding track：

M=■×a+■×b=■×45mm+■×100mm=163125kg·cm；

W=■=■=144cm3；

σ■=■=■=113.2MPa；

[σ]stands for permissible stress of Q235 steel plate.

[σ]=235/1.5=156.7MPa.

σ■<[σ]，indicating that the Q235 steel support can meet the supporting strength requirement.

4.2 Bearing Slide Block

（1）There is positive pressure stress on the bearing slide block caused by the girder gravity，and it is calculated as follows：

There are 4 bearing sliding blocks，and P stands for the support force of the bearing sliding block. P =900t/4 =225t

A stands for the stressed sectional area of the compressive stress.

A=700mm×16mm×3+500mm×16mm×3=576cm2

σ■ stands for the compressive stress on the sliding block support.

σ■ =225t/576cm2=39. 1MPa

[σ]stands for permissible stress of Q235 steel plate.

[σ]=235/1.5=156.7MPa

σ■<[σ]，indicating that the Q235 steel plate support can meet the supporting strength requirement.

（2）During the horizontal movement process of the box girder by the hydraulic pushing cylinders，the bearing slide block is not restricted horizontally from top to bottom，therefore，there is no horizontal bending moment and the calculation of the horizontal strength of the slide block is unnecessary.

（3）The calculation method for the compressive stress on the rear slide block support is the same as the calculation for the cylinder support outside the sliding track.

（4）Calculation of the weld strength of the support：

σ=■=■=20.4MPa

σ<[σ]，indicating that the weld strength meet the requirement.

4.3 Pushing Mechanism

4.3.1 Cylinder Selection

The coefficient of friction is calculated according to the weight of the 32m/900t box girder. The coefficient of friction between the slide block and the sliding track is 0.04 and the static coefficient of friction is 0.1 when starting the movement.

F stands for the maximum thrust of moving the box girder.

F=900t×1000×9.8×0. 1 =882kN.

There are four hydraulic pushing cylinders on both sides of the sliding tracks，and P stands for the horizontal operating thrust of each cylinder. P=F/4=220.5kN.

The cylinder has an elevation of 5 degrees，and P stands for the positive operating thrust of the cylinder. P=220.5kN/cos5°=221.3kN.

The cylinder pressure is 21MPa，and A stands for the minimum sectional area of cylinder piston. A=221. 3kN/21MPa=105. 3cm2.

D stands for the cylinder piston diameter or the cylinder inner diameter. D = 150mm.

A stands for the actual section areaof the cylinder piston. A=176.7cm2.

A=176.7cm2 > 105.3 cm2 （the minimum sectional area）

The cylinder actual section area is greater than the required minimum area.

P stands for the thrust produced by the cylinder. P=21MPa× 176.7cm2=371.kN.

371.kN> 221.3kN，the cylinder thrust is greater than the required operating thrust，indicating that the cylinder thrust can meet the operation requirements.

The pressure bar stability is calculated based on the diameter of the piston rod，and D stands for the diameter of the piston rod.D =75mm，L=2.5m，P=221.3kN，d=75mm

Sectional moment of inertial： I=■=1552368.2mm4

Sectional inertia radius： i=■=18.75mm

μ is valued 0.7 considering one end hinged and the other end fixed.

λstands for the flexibility of the pressure bar.

λ=■=93.3<100.

The flexibility of the pressure bar is less than 100. The pressure bar is a long rod and the critical stress is calculated by the empirical formula，therefore，

σ■=a-bλ=310-1.14×93.3=203.6MPa，

Critical force：P■=A·σ■=900kN.

According to this，the safety coefficient：n=■=■=4.07 is obtained，and the cylinder piston rod coefficient nw is generally 4-6，d stands for the diameter of the piston rod，therefore，the stabilization can be obtained when d is 100mm.

4.3.2 Hydraulic Pump Selection

The total horizontal movement length is 14.3m. Considering the weight of the box girder and the synchronization of pushing mechanisms on both sides，for safety purposes，the pushing speed of the cylinder represented by s，is 24m/h，that is 40cm/ min. Inside the cylinder，the flow rate represented by q is calculated below： q=s· A=40cm/min ×176.7cm2=7.1L/min.

The two adjacent piers are respectively provided with a hydraulic station and a hydraulic pump. Every hydraulic pump controlling 2 hydraulic pushing cylinders，and then required flow rate of the hydraulic pump represented by Q is calculated below： Q=2· q = 14. 2L/ min.

4.3.3 Motor Selection

The required motor power is 6.59kW and the calculation formula is shown below：

W = 16L/min× 21MPa/60/0. 85 = 6.59kW.

Therefore，the7.5kw three-phase asynchronous motor is selected according to the required motor power.

4.3.4 Performance parameters of the pushing system（refer to the bellow table 1 for detailed information）

4.3.5 Schematic Diagram of Hydraulic System （refer to the bellow Figure 4）

Adjustment of the device： Starting the motor，and adjusting the relief valve to control the system pressure within 31.5MPa，otherwise the pressure relief will happen. Then starting the manual valve，and adjusting the one-way throttle valve to control the speed of the hydraulic pushing cylinder，to ensure all cylinders work precisely synchronized.

5 Equipment Operation and Key points

5.1 Operation of the Girder Moving Device

（1）The sliding tracks are installed on the pier platform. Two parallel positioning lines are drawn on the adjacent piers，along which the sliding tracks are installed on the piers. Adjusting the height difference of base cushion according to the level gauge test data to ensure the bottom of the installation position of the same pier is in the same elevation. The position of the whole sliding track needs to be leveled with mortar and sheet iron plate. The sliding track should be anchored with chemical bolts.

（2）Mounting the bearing slide block，hydraulic pumping station and the hydraulic pushing cylinder on the sliding track.

（3）Assembling and Testing. The working pressure and the pushing speed of the hydraulic equipment should be adjusted in advance. No load testing operation should be conducted three times before moving the girder.

（4）Girder erection： Making sure all the slide blocks are on the same level and placing the box girder on the bearing slide blocks.

（5）The pushing work at the two adjacent piers should be started at the same time. The operating personnel on the two adjacent piers should suspend the pushing work every two minutes to check and adjust the pushing distance deviation.

（6）Jacking up the box girder with the hydraulic jacking device after the alignment operation and then the girder moving device can be removed.

5.2 Key Points

（1）Measuring the elevation difference among the slide blocks on the same side with the level gauge，and leveling them with sheet iron plate according to the measuring results. It is to ensure the elevation difference between the two slide blocks on the same side is less than 3mm.

（2）Two personnel with interphones should be assigned to each pier platform during the process of the horizontal movement to observe the condition of the sliding track and the slide blocks. The horizontal movement should be stopped immediately if any abnormal condition was observed.

（3）Marking scale on the sliding track，and making sure the horizontal moving distance of both ends of the box girder at the two adjacent piers are the same. And when the difference is more than 50mm，the movement should be stopped and the difference shall be adjusted.

（4）The sliding tracks should be kept clean without any debris，and should be lubricated by the lubricating oil.

（5）The girder movement should be carried out under the unified command and the command signals should be clear. All the personnel participating in the girder movement should be provided with interphones.

（6）For safety purpose，lighting facilities should be provided during the nighttime operation. The lighting lamp can be fixed on the front and rear supporting legs of the bridge girder erection machine and each side of the pier should be provided with at least three lighting lamps.

6 Conclusion

The girder moving device had been manufactured and put into operation on 18th February，2013. And the erection work of 26 pieces of box girder was completed successfully by 6th March，2013.

It proves that all the functions of this girder moving device can meet the design requirement and the field requirement. The girder moving device improved the construction efficiency and met the expected goal.

References

[1]Handbook of Design，Version5（2010.1），China Machine Press

[2]YANG，P.Y. ZHU，F(xiàn).Y.（2003.7），A Brief Handbook of Hydraulic System Design，China Machine Press

[3]QU，Y.Y.（2008.7），Electrical Control Design Atlas of Construction Equipment，China Machine Press.

[4]Electrical Safety of Machinery - Electrical Equipment of Machines - Part 1： General Requirements（GB5226.1-2002）（2013.12）.

[5]Common Mechanical Engineering Materials（2010.1），Chemical Industry Press.

[6]Safety Management Manual of Passenger Railway Box Girder？Transport and Erection（2008.2），China Railway Publishing House.

[7]Construction equipment of Passenger Railway Box Girder Fabrication，Transport and？Erection（2008.2），China Railway Publishing House.

[8]LI，A.，SHI S.M. YIN H.D.（2011.6），Technology for Exchange Construction of Abutments for Ballastless Track Bridge on Shanghai-Hangzhou High Speed Railway，Railway Standard Design.

[9]Technical Specification for Railway Bridge Erection by Girder-erecting Machine（TB10213-99）（2010.12），China Railway Publishing House.

This article was translated from a Chinese article published on Jiangxi Building Materials （ISSN 1006-2890）April 2013. The original is on open access article available online （http：//kns.cnki.net/KCMS/detail/detail.aspx dbcode=CJFQdbname=CJFD2013filename=JXJC201304152v=MjIyMTM0NUFab1I4ZVgxTHV4WVM3RGgxVDNxVHJXTTFGckNVUkxLZlp1WnRGeWprVnJyTEx6WEJiYkc0SDlMTXE=）.

*Corresponding translator： Tel. +2348038951155； E-mail： daishunfa@ccecc.com.cn （Dai Shunfa）.

收稿日期：2018-5-14