FLEXURAL VIBRATION OF FIXED SUPPORTED BEAMS
- 1. FLEXURAL VIBRATION OF FIXED SUPPORTED BEAMS SRINIVAS REDDY.S R19MCE13
- 2. • The dynamic bending of beams, also known as flexural vibrations of beams, was first investigated by Daniel Bernoulli in the late 18th century. • Resonance frequencies of beams with various types of end supports were examined for flexural vibration. • The natural frequencies associated with flexural vibrations are of much lower magnitude than those of torsional and axial vibrations. • The purpose of flexural vibration analysis is to know the structural behavior under the influence of various loads and to get the necessary information for design such as deformation, moments and dynamic forces etc INTRODUCTION
- 3. Response of the beams due to moving loads: • A single concentrated load is assumed to move with a uniform velocity the practical application for this problem occurs in bridges ,aircraft , carriers etc. • Automobiles , aircrafts , etc., while moving over the deck produces a number of effects , with increases the stresses in the structural members. some of them are the impact effect due to unbalanced parts of the vehicle ,impact effect due to irregularities of the deck surface and the effect on the structure due to smooth running of the vehicle. 1. The mass of moving load is considered to be small in comparison to the mass of the deck. This case is to be analysed as an elastic beam subjected to a moving load 2. The mass of moving load is considered to be larger in comparison to the mass of beam is neglected and the weight of vehicle is considered as a concentrated weight so the problem reduces to SDF system
- 4. fixed flexural vibration testing method of beams for timber guardrails • Young’s modulus is one of the properties that is related to the strength and can be obtained without damaging the specimen. One method for measuring Young’s modulus is a flexural vibration test. • A beam for a timber guardrail is fixed to a post by a bolt through a bracket (Fig. 1). Therefore, the end conditions of the beams used as timber guardrails are thought to be between those of simply supported ends and fixed ones. • the resonance frequency of a beam with fixed ends is about twice as large as that of a beam with simply supported ends, according to the Euler-Bernoulli elementary theory on bending. timber guardrails
- 6. VIBRATION TEST To obtain the resonance frequency of the first mode by bending, flexural vibration tests were conducted by the following procedure. • An apparatus (End condition controller) shown in Fig. was used to provide various end conditions. • By screwing a bolt attached to a load cell, the test beam was compressed. • The compressing load was measured by the load cell and recorded by a data logger .Motion of the beam was detected by a microphone in the center part • The signal was processed through a fast Fourier transform (FFT) digital signal analyzer to yield high-resolution resonance frequencies.
- 7. Changes in resonance frequency with compression for 5-mm-thick spruce (left) and 10-mm-thick spruce (right)
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