An Investigation On Mechanical Properties Of Welded Grillage Slabs Large Scale Crawler Crane

Because of the maturity and application of modularization construction technology, the large crawler crane is playing a very important role during large-scale project. Compared with the ordinary bearing capacity of foundation, the pressure passed by pedrail is very large, so the cost of foundation treatment is also very high, if pedrail contacts with the ground directly. In order to reduce the requirements of bearing capacity of foundation, the welded grillage slabs turn to be an indispensable accessory to distribute load.The difference is unacceptable between the available calculation model of the welded grillage slabs and actual situation, although the welded grillage slabs have been calculated, analyzed, and put into practice. Apparently, there still is not a reasonable and practical calculation model on the welded grillage slabs, which could directly influence the calculation results of crane-welded grillage slabs-soil foundation interaction system. The crane could topple if guiding practical work with incorrect calculation model.Using general-purpose finite element program ANSYS, three kinds of regular calculation model of welded grillage slabs are proposed in this thesis, verified feasibility systematically. Comparison results showed that: cantilever beam model can be used to estimate the section of the welded grillage slabs as simplified model; elastic foundation beam model can be used as simplified model to analyze mechanical properties of the welded grillage slabs; contact model could calculate the welded grillage slabs accurately and reflect its stress states. In addition, simplified model coefficients of cantilever-beam model and elastic-foundation-beam model are proposed in the paper.During the research of crane-welded grillage slabs-soil foundation interaction system, the biggest difficulty is the lack of necessary experimental data, which makes the analysis uncertainly and also restricts application of practical engineering design. In this thesis, the field experimentation on prototype of the welded grillage slabs are designed and carried out. The experimentation is carried out at a practical engineering site and the load is applied by heaping weight gradually. The purpose of the experimentation has three points: to accumulate necessary experimental data and understand the mechanical characteristics and regularity of the overall system; to analyze the interactional mechanism; to obtain the values of strain and displacement under different levels of load, compared with the calculation results, and to verify the feasibility of calculation models.Reliability analysis showed that the structure parameters of the welded grillage slabs have different effect on reliability. Optimized design is given based on the reliability analysis, which makes the processing much easier and could save more materials.Simulation of mobile crane shows that the maximum stress appears when the crane moves to the middle of the welded grillage slabs, which should be considered when carrying out the design of the welded grillage slabs.The research of mechanical properties of the welded grillage slabs under different foundation conditions shows that the welded grillage slabs'stress, deformation and the ability of distributing load could be controlled by changing the coefficient of subgrade reaction, which is carried out by altering the thickness of sand under the welded grillage slabs.