عنوان مقاله [English]
Machine foundations induce a wide range of dynamic shear strain in foundation bed. Dynamic properties of soils including the damping ratio and the dynamic stiffness intensely depend on the level of generated dynamic shear strain. Therefore, considering the appropriate dynamic properties of a foundation bed corresponding to the generated dynamic shear strain is vital to have a better evaluation of the dynamic response of a machine foundation. This paper presents the design and construction of an apparatus namely “Foundation Model Response Test (FMRT)”. This apparatus provides the tests to investigate the dynamic properties of machine foundation and underlying bed, in a wide range of dynamic shear strain by employing a various range of dynamic excitation forces and static weight (dead weight). The FMRT apparatus could be used in the field to evaluate the dynamic response of the undisturbed bed and on the prepared bed in the laboratory test pit. Two types of steady-state and free vibration tests could be conducted by employing the FMRT apparatus. Steady-state vibration tests induce larger shear strain in bed, whereas free vibration tests induce smaller shear strain. Correlation the results of these two type of tests, dynamic responses and dynamic properties of foundation bed in a wide range of dynamic shear strain would be achieved. The accuracy and validity of all FMRT tests are possible to monitor precisely and any unwanted noises and modes of vibration are possible to control surely by evaluating the Fast Fourier Transform (FFT) of all sensors data when conducting tests. Several steady-state and free vibration tests have been conducted to show the performance of the designed apparatus. Moreover, the method of calculation, controlling unwanted vibration and correlation of free and steady-state example tests has been submitted. FMRT tests are low-cost, repeatable, non-destructive and reliable tests which make the evaluation of the dynamic response of machine foundation possible accurately.