Gantry crane conventional installation methods

overhead gantry crane general bottom-up approach according installation, first installed on the track running carriage and lower beam, and then were installed on both sides of the flexible legs and rigid legs, and with the temporary wind cable rope legs firmly. The truss girder assembly is required in advance in the field, can be used as benchmarks carts walking track will be assembled on the main beam cross track. Main beam assembly, should pay attention to maintaining its position across the upper camber to compensate for the weight deflection arising sinking. Main beam conventional installation method is to use other lifting equipment using single or dual lift lifting cranes, lifting the main beam horizontally in place. Before lifting the main beam must be accurately calculate its center of gravity position, and accordingly determine auxiliary crane lifting point positions and loads. The dual-lift crane should be based on reasonable performance auxiliary steel crane  lifting load distribution, each auxiliary crane lifting load shall not exceed the allowable load of 80%. According 40t/40m gantry crane girder situation, choose two from the weight of 50t class crawler crane truck crane or lift crane, lifting to meet the requirements. The use of single-lifting, you need to select from the weight of the crane 100t grade, tonnage greater uneconomical.
Girder weight of large, general lifting mechanism, crane cab car and other components are installed in the main beam after installation.
2 lifting girder installation method separately
Auxiliary crane at the construction site configuration is not big enough case, you can use the main beam tilt lifting separately to install, this method of installation projects are rare, novel methods for the selection of auxiliary crane less demanding, more economical.
40t/40m separately girder  hoist gantry crane  lifting installation method is as follows: first, the main beam assembly on the ground, due to the need unilateral lifting of the main beam on one side of the cantilever section of the flexible legs temporarily installed, then the main beam length of 44.526m, 5 total weight 42.792t. With an auxiliary crane girder flexure leg to terminal A as the fulcrum, the C-terminus of the rigid leg lift girders, and then another small auxiliary crane or chain hoists to move the assembled rigid legs under the main beam, the rigid leg in an inclined state to connect with the main beam (see Figure 2a); Then auxiliary crane lifting girder flexure leg side, with another small cranes or hoists to move the assembled flexible leg girders for connection with installation; Finally, install the main cantilever section and other parts.
In order to ensure that the main beam after unilateral lifting, supported on one side with a rigid leg accurately track connections need to calculate in advance the main beam cross on a good track position. Shown in Figure 2 the relevant dimensions, calculate results OA = 43.10m, before lifting the primary beam does not cross on the track when the leg-side end rigidity should exceed the distance track 44.526-43.1 = 1.426m ( See Figure 2b).
Auxiliary crane hoisting load F shown in Figure 2a can also be calculated from the parameters, when the main beam from the horizontal position when lifting Fmax = 212.9kN; when the main beam is connected with the rigid leg Fmin = 206.1 kN.
Lifting the leg-side main beam flexure shown in Figure 3. After calculation, when the main beam angle from the 21.86 ° -0 ° a change, lifting force from the 235.16-190.6kN change.
Can be drawn from the above analysis, the main beam 1 from installing optional auxiliary weight of 50t crane can be.
3 technical and economic comparison
(A) conventional main beam lifting method, the maximum load of the main auxiliary crane girder weight of 42.79t, at least level configuration of the crane 100t; lifting method used separately, assisted greatly reduce the load on the crane, the maximum lifting load is only 23.5t,sino hoist 50t-level configuration of the crane can be, in general, can meet the needs of the field, effectively reducing installation costs.
(2) conventional main beam lifting method requires the rigid and flexible legs are installed before lifting girder, two legs must pull rope wind cable is not conducive to field operations; while lifting method used separately, simply pull another side of the leg wind cable rope, lower requirement for the installation site, more conducive to operation, and rigid legs connected with the main beam to form a stable state and easier to secure.
(3) the conventional method of the main beam lifting, lifting legs when two officers must also configure the installation, aerial personnel, and must be continuous operation, thereby increasing safety risks; while lifting method used separately, two legs can be divided into sub- combinations and installation of the venue requirements reduced, relatively small venue can also be installed, while reducing the continuous operation time, reduce the security risk.
(4) Hoisting separately compared with the conventional lifting, although the rigid legs with the main beam will be too inclined state, the installation process is more complex, more difficult, but only need a lifting capacity of 50t auxiliary crane, as long as the the installation process to take appropriate measures, the method is feasible.
(5) main beam control separately lifting method focuses on one side of the rigid leg lifting, mainly girder assembly is placed in the ground must be accurate in order to ensure a rigid girder lifting legs with accurate place.
By 40t/40m girder gantry crane installation methods analysis and calculation, the same can be applied to other box-shaped truss gantry crane installation, combined with on-site to choose the timing of economic, security and mounting solutions.