Analysis And Test For Performances Of The Members In Existing Space Truss

Large span space structures in china have developed rapidly during the past ten years. The number of practical engineering is large, the shape of space structures tends to be diverse, and the corresponding theoretical research and technique of structure design grow up gradually.As a mature large span space structure type, the space truss has the advantages of nicer structural capability and the saving of the stuff which are widely accepted by civil engineers. But with the wider utilization of the truss , some collapses in the engineering occur because of the variation of the characteristics of the truss member under the influences of the surroundings and the service function.Various ways and advantages and disadvantages of working stress test and damage detection are summarized in this paper. And embarking on members vibration testing, analysis and test for the performance of the members in existing space truss are carried out.First, natural frequency of Euler-Bernoulli beam with elastic bearing and without the axial force is put forward. And numerical method is used to solve the equation by a program designed by the author, and the influences of shearing deformation and rotatory inertia (Timoshenko beam) on frequency are analyzed.And then the influence of axial force on natural frequency of flexural vibrating beam is analyzed. Natural frequency of Euler-Bernoulli beam with elastic bearing with axial force is put forward by differential equation. And the numerical method is used to solve the equation by a program designed by the author. Flexural stiffness of supports of members with bolted spherical joint is put forward for tensile members and compressive members, the sensitivities of parameters influencing the frequency such as the axial force N, the inertial moment I, the flexural stiffness of supports k1= k2, vertical stiffness of supports k3= k4 are analyzed.Relevant technology of structural test is also discussed in this paper, such as the selection of exciting methods, the advantage of hammering test, the choose of the hammer material and mass, the theory of model parameter identification .Combining with the theory above, the impulse exciting test of members in existing space truss is carried out in this paper. The exciting method is hammering testand hanging sandbag, the apparatus of frequency measuring are the random signal and vibration analysis system CRAS QL-108 signal analysis system.Comparisons between the measured value and the calculated value of the frequency are made, and the error analyses are also carried out. The possibility of the measured frequency to calculate the axial force N and the inertial moment I is analyzed, and some conclusions are reached: the axial force varies significantly as the frequency error varies, but the inertial moment varies slightly as the error varies. So, it is very difficult for the measured frequency to calculate the axial force on the condition of the current testing accuracy of the frequency. But the inertial moment can be derived by the measured frequency.Finally, some conclusions are summarized and the topics for further research are put forward to.