Research On Vibration Serviceability Of Floor Of Tianjin Library

With the development of complex structures, the problems of floor vibrationserviceability due to pedestrian excitation appeared. By taking the truss-suspendedfloor of the new Tianjin library as the research object, the study of vibrationserviceability of floor has been conducted. Based on modal test and vibration test, thegeneral methods of finite element modeling and comfort calculation were obtained.According to the above analysis, the serviceability of floor in the library has beenevaluated.First of all, based on the review of domestic and foreign literatures, evaluationcriteria and index system of floor vibration serviceability were introduced. Comparingthese standards, the evaluation criterion provided by CSA and AISC/CISC was chosenfor this article: If the fundamental natural frequency of floor is between4Hz and8Hz,the peak acceleration should be lower than1.5%g.The frequencies and modal shapes of the floor were obtained by modal test, andthey were compared with the numerical calculated results. Then the method ofdetermining boundary conditions by the boundary stiffness was proposed, and theapplicable finite element model was established. It was concluded that the floor modelwith fixed supports from columns and pinned supports from the vertical web memberprovided the most appropriate representation of the real structures. This method withexcellent generality could promote the study in the future. On this basis, time historyanalysis targeting at the peak acceleration of floor was finished. Under variableanalysis, the influence of walking load frequency, loading position, the number offloor modal, and software solving method on vibration response under pedestrianexcitation was assessed. It demonstrated that the maximum response of floor wasdetermined by modal resonance. The maximum response was achieved when the firstmodal resonance load was applied on the first mode shape center.Finally, comparative analysis of theoretical and experimental studies revealed thatthe acceleration given by calculation and measurement showed good agreement underwalking condition. Under synchronous walking, the measured value was0.115m/s2,and the calculated value was0.0997m/s2, which meet the limit requirements. The peakacceleration under single jump condition was0.1406m/s2and was less than0.15 m/s2.With the increase in distance between feeling points and incentive points thevibration attenuated significantly. But the acceleration response exceeded the limitunder multi-jumping condition. In conclusion, the results indicated that the responsesof human induced vibration satisfied the demand the requirements in serviceabilitylimit state. The floor of multimedia reading room under walking does not affect theserviceability. However, jumping and other strenuous exercise should be avoided.