The Research On Design Theory Of Dynamic Machine Foundation

The advantages and disadvantages of the theory of quality-spring-damper and the theory of elastic half-space were discussed in this dissertation first, and based on the results of the development of elastic half-space theory in recent decades, developed a set of composite lumped parameter model compatible with the theory of quality-spring-damper using equation equivalence method, its reliability has been proved by the theory and the author,s experiment, And using the engineering examples (the dynamic response of125000kN press foundation was calculated by making use of this model), the results of calculations were compared to further illustrate the reliability of the model. In the underfunded of China Association for Engineering Construction Standardization project’study of dynamic machine foundation design theory and its application’, the main achievements of this dissertation what the author studys after years are described as follows:1.Based on elastic half-space theory and the latest research results of the foundations oscillating experiments and numerical analysis, a set of the composite lumped parameter model (CLPM) was developed by adopting equation equivalence method, which suits to vertical, torsional, swaying and rocking vibration of the lumped foundation. All of oscillation frequencies, a realistic range of Poisson’s ratios, all foundation base shapes, and complicated embedment are considered.2. With the new model, dynamic responses of a complicatedly-shaped surface and embedment foundation vibration harmonic vertically, torsionally, horizontally, rockily is calculated respectively and in good agreement with the results obtained by the formulas(supported by results of comprehensive experimental and numerical analysis), which have been developed by the theory of elastic half-space for computing the dynamic stiffness and damping coefficient of foundations harmonically oscillating on a homogeneous half-space, the amplitude difference of surface and embedment foundation is:verticality1.95%and embedment10.7%, torsion3.13%and embedment2.31%, horizontality9.16%and embedment22.91%, in lateral direction, rock0.17%and embedment12.31%, respectively.3. In the pits of20m×10m×4m, based on concrete lumped model of foundation designed for0.5m×0.5m,283kg and1.0m×0.5m,566kg, a steel ball of5.5kg happens free-fall motion and circular motion by the initial velocity. Free vibration of foundation perturbed vertically and torsionally was achieved in case of surface and embedment respectively. 4. Compare the result of experiment to the result of calculation performed with vertical and torsional CLPM, which shows a better closed agreement is found. The difference of vertically vibration of0.5m×0.5m and1.0m×0.5m surface foundation is16.2%and44.4%respectively, embedment foundation is33.2%and26.3%respectively; the difference of torsion vibration of0.5m×0.5m and1.0m×0.5m surface foundation is7.8%and14.1%respectively, embedment foundation is15.5%and14.5%respectively.5.The dynamic response of125000kN press foundation was calculated by making use of this CLPM proposed in this paper and the cod for design of dynamic machine foundation and the theory of wave scattering, the results of calculations were compared with the experimental results to further illustrate the model is correct. The amplitude of calculation of125000kN press foundation by making use of three models, the amplitude of calculations of the CLPM proposed in this paper is the smallest that it is the most economical in the design of dynamic machine foundation by using the model presented in this paper.The CLPM of block foundation deduced in this paper translates the dynamic parameter of the relevant frequency parameters based on theory of half-space elastic, into constant parameters which has nothing to do with frequency of perturbation load. The advantages of the composite lumped parameter model are clear concept and simple calculation. It is practical for power equipment lumped foundation of arbitrarily shaped and complicatedly embedded lumped foundations. Adopting CLPM can reduce or omit experiments. The multiple degrees of mechanical vibration theory can be used to canculate the dynamic response of block foundation based on elastic half-space as long as the known of foundation soil shear modulus, basic bottom shape and buried for status. This model from the dimensionless frequency factor influence, theoretically, applies to all frequencies including continuous frequency, playing an important reference role for the earthquake response analysis of structural engineering.