Method and apparatus for measuring the load bearing capacity of a platform

• US 6,513,384 B1
• Filed: 04/20/2001
• Issued: 02/04/2003
• Est. Priority Date: 11/05/1998
• Status: Expired due to Term

• Current Assignee: Laboratoire Central Des Ponts et Chaussees
• Original Assignee: Laboratoire Central Des Ponts et Chaussees
• Inventors: Leroy, Maurice, Froumentin, Michel, Marignier, Jacques, Quibel, Alain, Morel, Guy
• Primary Examiner(s): Williams, Hezron
• Assistant Examiner(s): SAINT SURIN, JACQUES M
• Application Number:
  US09/830,001
• Time in Patent Office: 655 Days
• Field of Search: 735/94, 731/46, 73/8, 737/88, 737/90, 736/36, 736/39
• US Class Current: 73/594
• CPC Class Codes: E02D 1/022 by investigating mechanical properties of the soil E02D1/027 takes precedence
• CPC Class Codes: G01M 7/00 Vibration-testing of structures; Shock-testing of structures G01M9/00 takes precedence
• CPC Class Codes: G01N 2203/0244 Tests performed "in situ" or after "in situ" use
• CPC Class Codes: G01N 2203/0284 Bulk material, e.g. powders
• CPC Class Codes: G01N 2203/0623 using piezoelectric gauges
• CPC Class Codes: G01N 2203/0676 Force, weight, load, energy, speed or acceleration
• CPC Class Codes: G01N 3/34 generated by mechanical means, e.g. hammer blows
• CPC Class Codes: G01N 3/50 by measuring rolling friction, e.g. by rocking pendulum G01N3/54 takes precedence
• CPC Class Codes: G01N 33/24 Earth materials G01N33/42 takes precedence
• CPC Class Codes: G01N 33/42 Road-making materials G01N33/38 takes precedence

Abstract

The invention relates to a method and an apparatus for measuring the lift of a transport infrastructure road level and industrial floors. The apparatus comprises a wheel borne by a chassis pivotally mounted on a trailer towed by a vehicle. An unbalanced member causes the wheel to vibrate. The vertical acceleration of the chassis and of the wheel and the angle of the centrifugal force of the unbalanced member with the vertical, are continuously measured. The total force applied by the wheel, the chassis and the unbalanced member is calculated from the measurements of the accelerations, as is the deflection of the road level by double integration of the acceleration of the wheel.

Claims

1. Method for continuously measuring the stiffness of a transport infrastructure road level and industrial floors, wherein it comprises the following steps of:

rolling on the road level a wheel of mass Mr suspended beneath a chassis of mass Mc,

subjecting the wheel to vertical vibrations by means of an unbalanced member rotating about the axis of the wheel and subjected to a centrifugal force Fc,

measuring as a function of time the vertical acceleration Gr of the wheel and the vertical acceleration Gc of the chassis by means of acceleration sensors mounted on the wheel and on the chassis,

measuring as a function of time the angular phase φ

between the direction of the centrifugal force Fc of the unbalanced member and the vertical by means of a sensor,

calculating as a function of time the vertical component FTA of the force applied by the wheel on the road level,

calculating as a function of time the vertical deformation d undergone by the road level from the measurement of the vertical acceleration Gr of the wheel,

establishing for each cycle of vibration the loop of the vertical component FTA with respect to the deformation d,

calculating at each cycle of vibration the gradient of the loop in the branch of the ascending vertical components in order to obtain the stiffness of the road level.

2. The method of claim 1, wherein the gradient of the loop is calculated in the range of ascending vertical components included between 30% and 90% of the maximum vertical component.

3. The method of claim 1, wherein the elastic modulus of the road level is calculated by multiplying the value of the stiffness by a coefficient of calibration C determined by prior experimentation.

4. The method of claim 1, wherein the frequency of the vibrations is included between 20 and 50 HZ.

5. The method of claim 1, wherein the wheel is advanced at a speed close to 1 m/sec.

6. The method of claim 1, wherein the speed of displacement of the wheel is measured continuously.

7. The method of claim 1, wherein the average stiffness of the road level per unit of distance covered is calculated by calculating the average of the stiffnesses calculated for the cycles of vibrations corresponding to this unit of distance covered.

8. The method of claim 7, wherein the average stiffnesses calculated as a function of the distance are continuously displayed on a display screen.

9. Apparatus for carrying out the method of claim 1, wherein it comprises:

a towable trailer resting on wheels for rolling over the ground,

a chassis of mass Mc mounted on the trailer so as to be able to pivot about a transverse axle,

a wheel of mass Mr equipped with an unbalanced member and suspended beneath the chassis,

means for rotating the unbalanced member,

a first acceleration sensor mounted on the chassis,

a second acceleration sensor mounted on the wheel,

a sensor detecting the angle of the unbalanced member,

means for calculating the vertical deformation undergone by the road level, as a function of time,

means for establishing, upon each cycle of vibration, the loop of the vertical component with respect to the deformation, and means for calculating the stiffness of the road level upon each cycle of vibration.