How to make highway bridge concrete girders?
Highway Bridge concrete girders could be made by 4 methods: full span prefabrication, segments prefabrication, full span cast-in-place and segment cast-in-place
- Full span girder fabrication in the precast yard
Build precast yards to prefabricate precast girders, after stressing, the girders are transported by girder carrier to rear part of the beam launcher and then are lifted to proper position. Rail girder carrier has small pressure on the bridge deck, but costs much.
Front part of beam launcher for girders carrying and installing could erect precast girders on the abutment, and the rear part could carry girders in the precast yard, so it saves one set gantry crane.
The most widely used tires girder carrier nowadays could go about 15km. to reduce pressure on the bridge deck, the beam launcher goes to next pier by self-balancing method. Full span girder installation is suitable for bridges with a large quantity of precast girders.
- Segment girder prefabrication
After girder segments are prefabricated, tires carrier carrys them to rear part of beam launcher or under the bridge, then the beam launcher lifts them segment by segment and coats glue, and tension them to an entirety. The construction period for a complete span may take 10 days. The construction method is suitable for bridges in the city or across the river.
- Full span cast-in-place girder
Steel pipe supporting in the urban construction has a long assembly time and a large influence on traffic.
In the mountain area, the movable supporting system is widely used. Put mould plate, inner formwork and steel cage on the supporting part, pour concrete once to make full span cast-in-place box girder, begin to produce another girder after 12 days later
- Segment cast-in-place
The traveling formwork is mostly used. Firstly make cast-in-place segment with formwork on the pier, then symmetrically make two pieces of girders to two sides, repeat it until the bridge deck is connected.
The construction method is widely used in railway bridge across highway, has a small influence on ground traffic.
How to construct high speed railway bridge?
To construct high speed railway bridge with design speed 300km/h, we have to learn how to produce concrete girders, Generally, there are two ways as below:
How to handle precast girder segments joints in the bridge construction?
With different precast girder segments joints treatment methods, it is divided as dry assembly method and wet joints assembly.
Dry assembly method refers to cohere all segments together by coating epoxy resin in the assembly, then tension them to be one entirety.
Wet joints assembly means to pour cast in situ concrete into joints with about 50cm wide between two segments, the beam launcher could move to next span only after the cast in situ concrete reaches the strength. With the waiting time, the construction time for one span with wet joints assembly will take about 10 days, while the dry method assembly only takes 3-4 days.
Dry assembly method has a lot of advantages comparing with other construction methods:
- Compared with full span cast in situ method: the latter must set support and the ground base must have a higher load bearing capacity, so it will have a big influence on the traffic and environment under the bridge; besides, the construction period takes a long time;
- Compared with full span precast girder installation method: the latter could not transport to a long distance with large dimension, the precast yard must be built nearby, so construction in the city could not meet the demand easily. Transportation in short distance also has higher demands on road, investment and environment.
So more and more urban bridge construction projects use dry assembly method.
Fast worksite shifting of overhead launching gantry
If we disassemble and reassemble the overhead launching gantry as it finishes installing bridge girders, it will cost a lot of time and manpower and money, so fast worksite shifting to another place is necessary.
After finishing installing precast girders, hydraulic cylinders in the support legs jack up the complete machine, then 2 sets of girder carriers drives into the proper position of overhead launching gantry, lower down the main girder onto the girder carriers, take back hydraulic cylinders, then 2 sets of girder carriers carry the overhead launching gantry to the next worksite.
Like this, we do not need to disassemble the launching gantry, it is transfered to another worksite easily and conveniently.
How about safety monitoring system of launching gantry?
Nowadays, Safety monitoring system is mandatory safety device for launching gantry in China, because it could greatly reduce the accidents rate and ensures personnel safety. Below functions could help you to better understand the safety monitoring system:
- Have the function to monitor and record operation status of launching gantry, including data like overhead trolley longitudinal moving distance, height, overhead trolley lateral moving distance, weight, wind velocity, levelness, perpendicularity of support legs, the complete machine longitudinal and lateral moving journey, the data could be recorded in local monitor and stored in the remote server to meet the demand on accidents analysis of launching gantry;
- Have the function to monitor tilting degree of launching gantry, analyze the safety condition of beam launcher by measuring longitudinal inclining and inclining angle of stand column, send alarming signals as inclining of launching gantry is in critical state;
- Have the function to monitor wind velocity in the real time, which reminds driver to operate the launching gantry safely;
- Have the function of long distance monitoring on safety state of launching gantry at real time, which could meet the demand on remote management.
How about renting of beam launcher?
Beam launcher is used to erect precast girder in bridge construction projects. Generally it has a large self weight and long production period and higher price. So when people could not afford it, they choose to rent a second used one.
China and Indonesia sign a formal agreement on Djakarta-Bandung high speed railway project with started construction in November
Djakarta local time October 16, China consortiums lead by China Railways Corporation sign a formal joint venture agreement with Indonesia state-owned consortiums, the joint venture will be in charge to build and operate the high speed railway project from Djakarta to Bandung.
How about maintenance of cranes?
China will compete to tender for British high speed railway project
For current Sino-British Relation, UK Prime Minister Cameron described it as “the year 2015 is not only the golden year of Sino-British relation, but also a golden age will be established in the coming 5 years”.
To attract investment, England specially declared a competitive tender in China for No.2 high speed railway construction project with total value 11.8 billion pounds.
Safety operation rules for launching gantry
In the bridge construction, safety operation rules shall always come first for personnel safety and smooth operation.
