JPS62211406A - Method for vibrating structure - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a vibration excitation method applied to vibration experiments of long structures such as bridges.

[Conventional technology]

Conventionally, various methods have been used to vibrate structures such as bridges, but the following two methods are listed as representative methods in relation to the present invention.

(Simply driving a vehicle on a bridge with impact vibration caused by 11 vehicles can cause drying vibrations, but the vibration amplitude is so small that it is hardly applicable as an excitation method for experiments. .

Therefore, as a method of obtaining a large excitation force, as shown in Fig. 2, a method may be used in which a heavy vehicle 3 such as a truck is driven over an obstacle 2 and an impact force is applied to the bridge 1 at that time. there were.

(2) Vibration by a vibrator This is a method in which a vibrator 5 is installed on the bridge and the force generated by the vibrator is applied to the bridge 1, and is the method most often used in conventional vibration experiments. It is.

As shown in FIG. 3, the vibration exciter 5 generally utilizes an eccentric weight W7'z attached to the rotating shaft 6 in principle. Here, W is the weight weight! is the acceleration of gravity, r is the eccentric distance from the axis of the eight, and ω is the angular frequency of rotation.

[Problem that the invention seeks to solve]

Problems with the conventional technology include the following.

(1) Since the number of impact-exciting obstacles caused by a vehicle is one, the force acting on the bridge is only a single impact force, and the amount of vibration response amplitude generated by this is extremely small and a large response amplitude cannot be obtained. I couldn't.

In addition, since a single impact force contains many frequency components simultaneously, many vibration components of bridge vibration are simultaneously induced, and vibration components other than the vibration component targeted for the experiment, i.e.
This results in a distorted vibration waveform that contains a lot of noise, and the accuracy of the experiment decreases.

(2) Excitation by an exciter In the case of exciter excitation, the excitation force is F=! It becomes deω2. In this case, in order to obtain a large excitation force, it is necessary to increase the weight W of the weight or the rotation radius r of the weight, and a large-scale exciter is required. In particular, in a range where the vibration period is long and the helical angular frequency ω is small, such as in a bridge, the excitation force becomes significantly small.

In addition, in the case of an exciter, a motor is usually used as the drive source, so in order to obtain a large excitation force, a high-output motor is required), and ordinary bridges do not have electric power equipment. It requires an electric crab with an exciter drive.

[Means for solving problems]

A plurality of obstacles or more are successively installed on the top surface of a bridge at appropriate intervals, and a vehicle is run on the obstacles at a constant speed to continuously apply an impact force to the bridge.

At this time, the relationship between the installation interval of obstacles and the vehicle's running speed is adjusted so that the time interval (period) at which the vehicle passes over the adjacent obstacles matches the natural period of the bridge, or is an integral multiple of the natural period. make it match.

[Effect]

By continuously applying a large impact force synchronized to the natural period of the bridge to the bridge, the vibration amplitude of the bridge gradually grows and a large vibration amplitude can be obtained.

〔Example〕

An example is shown in FIG.

This is an example in which four rows of obstacles 2 are installed on the top surface of a bridge 1. The vehicle is caused to travel at a constant speed y in the traveling direction 4, passing over obstacles 2 one after another.

At this time, if the natural period of the bridge is T (seconds), the traveling speed of the vehicle is adjusted so that the time interval at which the vehicle passes an adjacent obstacle is rT (seconds).

FIG. 1<6) is a diagram schematically showing the excitation force that acts on the bridge due to this, and the force acts at intervals of period T (seconds).

Figure 2 (c+l) schematically shows the vibration response of the bridge when it receives this excitation force, and the vibration components of the period (seconds) synchronize and gradually grow larger.

〔Effect of the invention〕

By applying the impact force generated when a vehicle overcomes an obstacle to the bridge continuously, and by synchronizing the time interval at which the impact force acts to the natural vibration period of the bridge, we created a bridge that was the subject of an experiment. It is possible to induce a large vibration amplitude.

Compared to conventional methods, it is possible to easily induce large vibration amplitudes in bridges.

[Brief explanation of drawings]

Fig. 1 (A is a side view as an embodiment of the present invention;
61 is a diagram schematically showing the excitation force acting on the bridge according to the embodiment of the same figure (cL), and the same figure (e) is a diagram schematically showing the excitation force acting on the bridge according to the embodiment of the same figure (cL).
FIG. 2 is a diagram schematically showing the vibration response of a bridge when subjected to an excitation force of . FIG. 2 shows a conventional vibration excitation method using a vehicle, and FIG. 3 shows a conventional vibration excitation method using a vibrator. 1... Bridge, 2... Obstacle, 3...
Vehicle 4...Vehicle travel direction Sub-agent Patent attorney Shige Okamoto 2 persons Figure 3

Claims (1)

[Scope of Claims] A plurality of obstacles are installed at predetermined intervals on the upper surface of a long structure such as a bridge, and a vehicle is run over the obstacles at a constant speed, and the distance between the installation intervals of the obstacles and the vehicle's running speed are determined. A method for exciting a structure, characterized in that the relationship is adjusted so that the time interval (period) during which a vehicle passes over an obstacle matches the natural period of the structure or an integral multiple of the natural period.