Field Research On Comfort Level Of A Gymnasium Equipped With Long-span Prestressed Girders Floor System Under Human-induced Load

Because of the special structural arrangement of long-span prestressed girders floor, the reduced height of this structure is less than others. On account of the characteristics such as large span, light mass, big flexible, problem of vibration comfort is more likely to happen to this floor. As the structure system is used in gymnasiums, it has to often bear various rhythmed exercise, such as walking, running, jumping, playing balls, dancing and so on. Vertical vibration problem of this kind of floor is more serious than reinforced concrete floor. Although vibration problem unlikely cause safety problem of structure, people will be uneasy and be hard to bear if the vibration is so strong. Gymnasiums used as the site always full with people, suddenly vibration may cause panic in the crowd, and hidden trouble in safety. In order to fully realize advantage of long-span prestressed girders floor, and avoid vibration problem, additional baseboard is used in engineering design. To verify the improved effects, three aspects of research were carried out.Firstly, according to result data of previous finite element analysis, monitoring point arrangement was confirmed. Aim at service condition of gymnasiums and some influence factors of vibration response, 25 kinds of working conditions were designed, such walking, running, jumping and dancing with different amount of people, to test vertical vibration response of long-span prestressed girders floor. According to analysis result of the 200 groups of data, some influence factors and change rules of floor vibration response were found.While frequency remain unchanged, the ratio of vibration response caused by several people to vibration response caused by single people is ?9)~n(n equals to the number of people), and grows to ?9). While the number of people and frequency remain unchanged, vibration response caused by walking along beams is little bigger than walking perpendicular to beams, and vibration response caused by walking on slabs is little less than walking on beams. While number, frequency and route remain unchanged, the heavier or the stronger the tester is, the bigger vibration response is. Vibration response is connected with amplitude of human-induced load. While the number of people remain unchanged, vibration response becomes greater and greater as frequency of people approach natural vibration frequency of the floor little by little. Jumping and playing balls can impact floor, and cause bigger impact force than other exercise. This impact force can expand vibration response, and bring about harmful influence. Vibration response may be weakened as synchronism become inferior or application point become dispersive.Secondly, according to identification of modal parameter under the working condition with no people, the first three natural vibration frequency and mode of vibration were acquired. Compared with the result of finite element analysis, these two methods tend to be identical. According to identification of modal parameter under other 25 kinds of working conditions, the natural vibration frequency in each working conditions is similar.Finally, comparing existing norm and standard at home and abroad, some evaluation indexs were selected, such as acceleration-vibration level, fundamental frequency, RMS acceleration, peak acceleration and vibration amplitude. Based on measured data and special using environment of gymnasiums, the evaluation criterions applying to comfort level of this kinds of gymnasiums were selected. The results show that long-span prestressed girders floor equipped additional baseboard meet comfort requirements of vertical vibration under each human-induced load.