Abstract: An example crown assembly includes a button tube, a crown, a spring piece, a switch, and a fastening frame. The crown includes a crown cap and a crown stem that are connected. The spring piece includes a first plate, an elastic arm, and a second plate. Two ends of the elastic arm are connected to the first plate and the second plate. When pressure is exerted on the crown cap, the crown stem is capable of moving along the axis and pushing the first plate away from the end that is of the elastic arm and that is connected to the second plate, to enable the first plate to press the switch. The elastic arm is capable of generating elastic deformation, and when the pressure on the crown cap is released, the first plate is capable of pushing the crown stem away from the switch under elasticity of the elastic arm.

Abstract: The disclosure provides a method for identifying a modal frequency of a beam bridge by considering influence of environmental temperature. The method includes the following steps: installing a sensor on a newly-built beam bridge without damage, measuring a dynamic response of the beam bridge cinder ambient excitation, recording temperature data, processing by a modal parameter identification method to obtain a modal frequency value at the temperature, and starting from a modal frequency corresponding to the temperature, carrying out iterative calculation to obtain the modal frequency at any temperature. The modal frequency value at any temperature is obtained by arranging a small number of sensors and carrying out a small number of tests, so that the influence of the temperature on the modal frequency is quantified, furthermore, the part of environmental influence is eliminated in future damage evaluation of the beam bridge, which allows for a more accurate damage evaluation result.

Abstract: The disclosure provides a method for identifying a modal frequency of a beam bridge by considering influence of environmental temperature. The method includes the following steps: installing a sensor on a newly-built beam bridge without damage, measuring a dynamic response of the nearn bridge cinder ambient excitation, recording temperature data, processing by a modal parameter identification method to obtain a modal frequency value at the temperature, and titarling from a modal frequency corresponding to the temperature, carrying out iterative calculation to obtain the modal frequency at any temperature.