Vertical Vibration Analysis Of Large-span Prestressed Secondary Beam Floor Based On Acceleration Response

Based on the comfort assessment criteria for the peak acceleration of the floor,as proposed by the American Association of Steel Structures(AISC),this paper takes the actual height of the prestressed secondary beam floor as a background,and changes the beam height,thickness and thickness of the flat beam.Formed 11 kinds of floor plans.The single-load loading simulation analysis was carried out for each floor plan and the specific influence law of structural self-vibration frequency,structural damping ratio,load frequency,human body weight and load type in the vibration process of the floor was studied.In addition,simulations analysis were performed on 18 multi-person synchronized motions(including low,medium and high frequency load conditions)including 3 artificial conditions,9/10 artificial conditions and 20 artificial conditions The main result are:(1)According to the previous research results,11 structural arrangements for the large-span prestressed secondary beam floor are designed by adjusting the prestressed secondary beam height,floor thickness,and flat beam floor thickness.And establish the corresponding ANSYS 3D solid finite element model.(2)Based on the previous research results,the modal analysis of the finite element model is used to study the influence of relevant structural arrangement parameters on the vertical vibration frequency of the floor.From the perspective of improving the natural vibration frequency of the floor,the results show that increasing the height of the prestressed secondary beam and adding the flat beam floor is an effective measure,and the effect of increasing the thickness of the floor is not certain.(3)After extracting the first six modes of each floor,the transient response analysis of each scheme is carried out by modal superposition method.The results show that the vertical vibration acceleration response of the floor is mainly affected by the structure of the floor and the load.Specific factors include: the natural vibration frequency,mass,stiffness,damping ratio of the floor,as well as the type,frequency and human weight of the human load.(4)As the structural damping ratio increases,the vertical acceleration of the vertical vibration of the floor is significantly reduced.This rule can be used in the vertical vibration control of the floor.(5)As the frequency of human loads increases,the overall level of peak acceleration of the floor increases.At the same time,for the structure of the floor similar to this project,when the load frequency is close to 1/2 or 1/3 of the natural vibration frequency of the floor,the peak acceleration of the floor has a maximum value due to the resonance.(6)The simulation results of jumping load and walking load of single and multi-person show that the jump load response may reach 3.58~3.81 times of the walking load response and 4.79~5.02 times of the two-way frequency.Therefore,jump loads of the same frequency are more disadvantageous than walking loads.(7)Increasing the height of the prestressed secondary beam can reduce the peak acceleration of the vertical vibration of the floor(except for the resonance type);changing the thickness of the floor is not clear for controlling the peak acceleration;adding the flat beam floor can significantly reduce the peak acceleration.However,the effect of further increasing the thickness of the bottom plate is not significant.(8)Under the conditions similar to this project,the vertical vibration acceleration caused by the two-frequency resonance is the largest,which may control the design of the comfort of the floor.However,when the fundamental frequency of the structure is greater than twice the range of the human load frequency,the three-way resonance response and the non-resonant acceleration response at higher frequency human loads should be considered.(9)In the evaluation of the comfort of the floor-like resonance,the appraisal standard for the peak acceleration of the floor proposed by AISC is good.However,for non-resonant situations,the peak acceleration of the floor may only last for a short period of time.Therefore,it is necessary to comprehensively consider the influence of the acceleration amplitude and its action time,and use a more reasonable comfort evaluation standard.