By substituting the impact force into the surface response formula of a semi-infinite body, the ground response caused by the impact force can be calculated.
1.2 Vibration Time-Domain Process Analysis of Vehicles Driving on Speed Bumps Here, the displacement input is assumed to be and the structural response is assumed to be . Based on the calculation using the speed bump cross-sectional shape formula, we can set ug2 equal to 0 and ug2 equal to 1. Then, the force between the wheel and the ground is 1. The calculation of the impact force on the ground during the vehicle's bounce first determines the critical speed. Below this speed, the vehicle will not bounce, and the wheels will roll down the speed bump contour. Above the critical speed, the vehicle will jump directly from the top of the speed bump.
1. For a speed bump with a width of 380cm and a height of 5cm, fit the non-free descent height using a sine function: hf = 2gt² = 1g(2ti). 2. The descent height of the speed bump profile is: hh. Analyze the instantaneous situation when the vehicle tires just reach the top of the speed bump: The descent height of the speed bump profile is the free descent height (75km/h). If the speed exceeds this, the vehicle will experience a jumping phenomenon.
Then calculate the magnitude of the impact force. Compared to the overall stiffness of the vehicle, the road surface is approximated as a rigid body (stiffness difference of one order of magnitude). Adzf1.Ad is the vertical displacement of the vehicle under static load. Fd is the vehicle's weight. K is the vehicle's equivalent stiffness.
The strain energy in this process is 81Fd - (m1 + h = 1.8735 times the mass of the vehicle itself, which means the impact force is 1.8735 times the mass of the vehicle itself.
2. Ground Response Analysis Based on the stiffness matrix method of layered soil, the ground response under impact force can be calculated. In this paper, the soil layers are divided into three layers. Specific parameters are shown in Table 1. Table 1: Soil Layer Parameters Soil layer shear modulus G/MPa Soil layer thickness/cm Shear wave velocity Am.s Compression wave velocity/(m°s) Concrete layer Compacted layer Calculation formula for semi-infinite space: The response of the semi-infinite body surface can be obtained through calculation.
3. Field Measurement and Analysis 1. Measurement location: West Fourth Road, Zijingang Campus, Zhejiang University. Vehicles passed over speed bumps at speeds of 1050 km/h and 60 km/h, respectively, and vibrations in three directions (x, y, and z) were measured (x is perpendicular to the lane, y is parallel to the lane, and z is vertical). To reduce error, each condition was repeated once. The measured vibration peak values are shown in Table 2. From Table 2, it can be seen that the vibration magnitude in the x-direction (vehicle speed A/km/h) has a certain degree of randomness, but the vibration in the y and z directions steadily increases with increasing vehicle speed.
4. Conclusion This paper divides the process of a vehicle passing over a speed bump into three distinct stages: the impact of the tires on the speed bump, the vibration of the vehicle system on the speed bump, and the impact of the vehicle landing on the speed bump. For each stage, modeling and analysis are performed, and the interlayer stiffness matrix method is used to calculate the ground response. Finally, data is collected and analyzed through actual measurements.
