| Floor vibration is a problem that has always been associated with the use of the building.The vibration of the floor is an important factor affecting the comfort of the wooden architecture.The parallel chord truss is light,high-strength and durable,suitable for large-span floor structures,It becomes an important wooden floor joist member after sawn timber and I-beam.In this paper,two kinds of web system and two different wooden truss joists span are used.The vertical vibration problem of the slab is combined with modal analysis,pedestrian excitation acceleration analysis,displacement analysis of the slab under static load and transfer function analysis of floor vibration.Finally the effect of strongbacks and strappings on the vertical vibration law of wooden truss joist combination floor slab.The main conclusions drawn under the experimental conditions of this paper are as follows:1.When the spacing of floor joist is the same,there is no significant difference between the two parallel chord wooden truss joist used in this paper on floor vibration and vertical displacement.The first frequency of floor vibration with 600 mm joist spacing is about 12 Hz,while the first frequency of floor vibration with 400 mm joist spacing is about 15 Hz.2.The strongbacks perpendicular to the direction of the floor joists have little effect on the first-order vibration frequency of the floor;the floor with 400 mm joist spacing,the strongbacks have a significant influence on the second and third-order frequencies,and the number of strongback increases,The second and third order vibration frequencies of the floor increase accordingly.The floor with 600 mm joist spacing,as the number of strongbacks increases,only the third-order frequency changes significantly.3.The strongback can effectively reduce the vertical displacement of the floor.When the number of strongback is increased from 0 to 4 rows,the vertical displacement reduction at the center position of the floor with the spacing of 400 mm and 600 mm is almost the same under the concentrated load of 1 k N.4.The influence of strapping to frequency spacing of floor vibration modes is related to the spacing of joist.For the floor with 400 mm joist spacing,the influence of strapping on the first and second vibration frequencies is not obvious;Compared with the floor with 600 mm and 300 mm strapping spacing,the third vibration frequency of the floor with 400 mm strapping spacing is the largest;For the floor with 600 mm joist spacing,the influence of strapping on the top three order vibration frequencies is not obvious.5.With the increase of the number of strongback,the peak value of the vibration transfer function develops from near to far.For the floor with the same joist spacing,the web system of wood truss has obvious influence on the vibration transfer function.6.Strapping has little effect on the vibration transmission path perpendicular to the direction of floor joist.After installing the strapping,the peak value distribution area of the transfer function changes slightly.However,with the increase of the number of strapping,the peak value in the region near 20 Hz increases.The contribution of low frequency vibration signal to floor vibration response becomes larger.7.For the floor vibration response,the effect of strongback on reducing the floor vibration response under pedestrian excitation is more obvious than that of strapping,and the root mean square acceleration is more significant than that of peak acceleration evaluation of strongback and strapping on the floor vibration response.8.The response results of pedestrian excitation paths are different.With the increase of the number of strongback,the peak acceleration and root mean square acceleration of vibration along S and L lines of floor excitation path decrease.The peak acceleration along W lines is affected by accidental errors of pedestrian excitation,and the regularity is poor.In addition,the thickness of particleboard also has obvious influence on vibration transmission. |
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