Acceleration Response Spectrum For Predicting Lightweight Floor Vibration Based On The Full Path Of The Source-path-receiver

With the emergence and rapid development of low-quality and high-strength building materials,many lightweight large-span structures such as CFS composite floor,long span air corridors emerge in large numbers,making the floor mass only half or less than that of the ordinary concrete floor.Compared with the cast-in-place floor,the boundary condition of the lightweight floor is more weakened,and the frequency is more reduced.Therefore,compared with the traditional floor,the human-induced vibration serviceability problem is more likely to occur.In order to solve the problem of human-induced vibration of large span floor,it is necessary to control the acceleration amplitude of the floor for a given dynamic load.For a given dynamic load,the response spectrum method is an efficient method to calculate the maximum response.Most of the floor acceleration response spectrum research are not fully consider the interaction between pedestrian and structure.If the action of pedestrian on the floor is simply regarded as a pedestrian load,the evaluation results may be inaccurate.However,the above studies did not establish the vibration comfort evaluation directly based on the response of receiver in the source-path-receiver full path,but adopted the peak response limit of the structure under the source-path as the vibration comfort standard.In practical engineering applications,the limit value of vibration comfort of footbridge is often inconsistent with the actual feeling of people.It is obviously not accurate to regard the response of the structure as a criterion for evaluating the vibration serviceability of human.Hence,it is necessary to consider the peak acceleration of the receiver acting on the structure as one of the criteria for evaluating serviceability.In order to evaluate the vibration comfort of light span floor,this paper considers the existing research status,and firstly designs the acceleration response spectrum of lightweight long-span floor under pedestrian load.Then,the effects of the response spectrum design before and after considering the human-structure interaction are compared.The source-path-receiver full path method of human induced vibration serviceability assessment is adopted in this paper.Taking Cold-Formed-Steel(CFS)composite floor with lightweight and dense modal as an engineering example,the dynamic responses of the floor and receivers of different ages and genders are analyzed when the pedestrians crosses the floor at a normal step frequency.Finally,the vibration serviceability of the floor and the receiver is assessed by the method of cumulative probability.The main contents of this paper include the following aspects:(1)This study takes Cold-Formed-Steel(CFS)composite floor with lightweight and dense modal as an engineering example,and using MATLAB to build large span floor under standard pedestrian incentive calculation model.The vibration control equation of the lightweight floor uses differential quadrature(DQ)-integral quadrature(IQ)mixing method to discretize the governing equation.The data such as natural frequency of floor and acceleration root-mean-square response are draw into related response spectrum curve.According to the laws of statistics,response spectrum curve is divided into up-platform-down three parts,and every part of the expression is solved respectively.Under the same conditions,the acceleration predicted by the response spectrum was compared with the time history value and peak value in the form of tables and pictures respectively.It is found that the design response spectrum can provide effective guidance for adjusting the comfort level of floor vibration.(2)The pedestrian is seen as the mobile biomechanical model with mass-stiffness-damping.The equation of pedestrian-floor interaction coupled vibration control is established and solved.This chapter takes Cold-Formed-Steel(CFS)composite floor with lightweight and dense modal as an engineering example,and using MATLAB to build large span floor under standard pedestrian incentive calculation model.The data such as natural frequency of floor and acceleration root-mean-square response are draw into related response spectrum curve.Compared with the response spectrum of light floor under walking excitation,the feasibility and advantages of the method are verified.(3)In order to consider the influence of human dynamic parameters on human-induced vibration serviceability of lightweight floors,Based on the given progress,different ages and genders receivers are selected to represent different human dynamic parameters.By adopting the evaluation and analysis method of the full path,the equation which considering pedestrian,floor and receiver is established and solved by appropriate method.The Cold-Formed-Steel(CFS)composite floor with the lightweight is selected as an example,when the pedestrian walks across the structure at a normal step frequency,the 1 s root-mean-square(RMS)curve and acceleration curve of the floor and receivers are obtained respectively,as well as the corresponding cumulative probability of the floor and the receivers under the different step frequency.(4)According to the full path analysis method theory in the last chapter,the data such as natural frequency of floor and acceleration root-mean-square response are draw into related response spectrum curve.Then,every part of the expression is solved respectively.By comparing predicted response spectrum curve between the floor and receiver,it is shown that the design value of structural response spectrum is not accurate enough to replace thereceiver.When evaluating and predicting the vibration comfort of the receiver,it is necessary to design the response spectrum for the receiver.