Measuring device and method for horizontal dynamic impedance of specified foundation depth based on differential response analysis of pulse excitation

Patent metadata

Field	Value
Publication number	US-11066805-B2
Application number	US-201816477184-A
Country	US
Kind code	B2
Filing date	Mar 19, 2018
Priority date	Mar 19, 2018
Publication date	Jul 20, 2021
Grant date	Jul 20, 2021

Abstract

A measuring device and method for horizontal dynamic impedance of specified foundation depth based on differential response analysis of pulse excitation. The measuring method is realized based on the measuring device. Two rigid piles with different lengths are embedded into different foundation depths. Motion characteristics of the two rigid piles in the process of collision impact with the outside are different under the same pulse excitation. Dynamic impedance of specified foundation depth is deduced from the formula according to the differential response. Single-degree-of-freedom oscillators are arranged on the pile heads of the two piles, and strain gauges are arranged on the bottoms of the single-degree-of-freedom oscillators to obtain stress states of the single-degree-of-freedom oscillators, thereby calculating the relative displacements of the single-degree-of-freedom oscillators. This is simple in structure, reliable in measurement and convenient in data collection and processing.

First claim

The invention claimed is:

1. A measuring device for horizontal dynamic impedance of specified foundation depth based on differential response analysis of pulse excitation, the measuring device comprising a bracket ( 1 ), a bidirectional electromagnetic exciter ( 2 ), single-degree-of-freedom oscillators ( 3 ), strain gauges ( 4 ), a raft ( 5 ), two rigid piles ( 6 ), a photosensitive band ( 7 ), laser sources ( 8 ) and an information collector ( 9 ), wherein
the two rigid piles ( 6 ) with different lengths are embedded into different foundation depths; the single-degree-of-freedom oscillators ( 3 ) with different frequencies are arranged on pile heads of the two rigid piles ( 6 ) according to the frequency of an actual structure, and the natural vibration frequencies of the single-degree-of-freedom oscillators ( 3 ) are regulated by regulating the heights and the mass of the single-degree-of-freedom oscillators ( 3 ); the strain gauges ( 4 ) are vertically arranged on the bottoms of the single-degree-of-freedom oscillators ( 3 ) and used for measuring bottom strain of the single-degree-of-freedom oscillators ( 3 ); laser source ( 8 ) is arranged respectively on each of the single-degree-of-freedom oscillators; absolute displacements of the single-degree-of-freedom oscillators ( 3 ) at each moment are measured through the photosensitive band ( 7 ) arranged at one side parallel to the axes of the two rigid piles ( 6 ) and the information collector ( 9 ) connected with the photosensitive band ( 7 );
the raft ( 5 ) is arranged on the junction of the rigid piles ( 6 ) and a foundation surface and is used for ensuring that the junction of the rigid piles and the foundation surface is static; the bidirectional electromagnetic exciter ( 2 ) is installed on the raft ( 5 ) through the bracket ( 1 ) and is positioned between the two rigid piles ( 6 ) to ensure that impact loads on the two rigid piles ( 6 ) are the same; the bidirectional electromagnetic exciter ( 2 ) can instantly eject an oscillator to impact a pile head through electromagnetic change.

2. A measuring method for horizontal dynamic impedance of specified foundation depth based on differential response analysis of pulse excitation, wherein the measuring method is realized based on the measuring device, and a pile head reserved on the foundation has a length of h 0 ; the instantaneous acting force F=m′ü′ of the bidirectional electromagnetic exciter ( 2 ) on the pile head is obtained according to the acceleration ü′ exerted to an excitation block by the bidirectional electromagnetic exciter ( 2 ) and the mass m′ of the excitation block; the following physical quantities are obtained through measurement: the instantaneous acting force F of the exciter on the pile head, the mass M of a short pile, the mass M′ of a long pile, a distance h n from the bottom of a soil layer to the ground surface and the mass m of the single-degree-of-freedom oscillator; the method specifically comprises the following steps:
1) the bidirectional electromagnetic exciter ( 2 ) ejects the oscillator, and the oscillator comes into full contact with the pile head of the rigid pile ( 6 ) and rebounds to obtain the instantaneous acting force F;
2) the vertical strain ε on the bottom of a cantilever bar of the single-degree-of-freedom oscillator ( 3 ) is measured through the strain gauge ( 4 ) on the bottom of the single-degree-of-freedom oscillator ( 3 ); the relative displacement u s (t) of the single-degree-of-freedom oscillator ( 3 ) at a certain moment is obtained through calculation; and the speed {dot over (u)} s (t) of the single-degree-of-freedom oscillator ( 3 ) relative to the pile head and the relative acceleration ü s (t) are obtained through differential;
3) the displacement u z (t) of the single-degree-of-freedom oscillator ( 3 ) at a certain moment is measured through the information collector ( 9 ) by means of the laser source ( 8 ) arranged on the single-degree-of-freedom oscillator ( 3 ) and the photosensitive band ( 7 ) arranged on the raft ( 5 ); speed {dot over (u)} z (t) and acceleration ü z (t) are obtained through differential; and displacement u q (t), speed {dot over (u)} q (t) and acceleration ü q (t) of the pile head are obtained:
u q ( t )= u z ( t )− u s ( t ), {dot over (u)} q ( t )= {dot over (u)} z ( t )− {dot over (u)} s ( t ), ü q ( t )= ü z ( t )− ü s ( t )  (1)

4) for the short pile a, the following dynamic equation is used:
MΣü q ( t,h )+Σ c ( h ) {dot over (u)} q ( t,h )+Σ k ( h ) u q ( t,h )= F−mü s ( t )  (2)

to obtain:

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Assignees

• Univ Dalian Tech

Inventors

• Li Jianbo
• Liu Weihong
• Li Zhiyuan
• Lin Gao

Classifications

• E02D33/00 Primary

  Testing foundations or foundation structures (testing methods and apparatus, see the relevant subclasses of class G01; testing structures or apparatus as regards function, in general, G01M; testing or determining chemical or physical properties, in general G01N) · CPC title

• E02D27/32 Primary

  Foundations for special purposes {(for paving of roads E01C3/00)} · CPC title

• E02D27/34

  Foundations for sinking or earthquake territories (building constructions with protection arrangements against earthquakes E04H9/02) · CPC title

• G01H15/00

  Measuring mechanical or acoustic impedance · CPC title