FUNDAMENTAL STUDY ON WALKING VIBRATION OF CROSS LAMINATED TIMBER FLOOR WITH FINISHING JOIST FLOOR

Abstract

 Walking vibration can cause complaints to building users on building floor, especially on timber floor. However, the estimation method of walking vibration at the design stage is still not established. In the previous study, the vibration characteristics of a CLT floor subjected to walking vibrations was measured. Then, the finite element model was also created to investigate the influence of varying material properties and boundary conditions on the vibration performance of the floor. Furthermore, via measurement three specimens of CLT floor, the influence of CLT floor-wall connection upon vibration characteristics was investigated. Finally, through analytical modeling based on these results, the span table of CLT floor from the viewpoint of walking vibration was presented.

 In this study, continuing from the previous study, to reveal the influence of finishing joist floor on CLT floor on walking vibration, CLT floors made of two kinds of materials with finishing joist floor were investigated. At first, vibration characteristics of the CLT floors without joist floor and with joist floor subjected to walking vibration were measured. Then, via some investigation about parameters, element shapes, and walking excitation force, four finite element models were also created and the analysis methods to reproduce the measured results were obtained.

 The investigation procedure and result are described as follows;

 1) Vibration characteristics of two CLT floors (one is made of KARAMATSU, the other is made of TODOMATSU) without joist floor were measured through static loading test, dynamic impact test and walking vibration test. It was found that the stress was transmitted not only in the strong axis direction but also in the weak axis direction regardless the half lapped joints, as in the previous study.

 2) Vibration characteristics of two CLT floors with joist floor were measured through dynamic impact test and walking vibration test. Comparing to the results measured without joist floor, it was found that the natural frequency was increased by the finishing joist floor despite of the floor weight increase. And the damping ratio was slightly increased by the finishing joist floor. Furthermore, the VLT index decreased by 8dB, and the evaluation of the walking vibration on the annoyance scale was improved in two categories by the finishing joist floor.

 3) In the final analysis models which can reproduce the measured results, the half lapped joint was set as lower vertical gap, the elements on the floor with no vertical support were set as loading their weights at the point. In addition, the finishing joist floor was set as the elements of the same size, shape, and material properties.

 4) The walking vibrations on these floors were reproduced by the analysis method which was presented in the previous study.