00078 Lin Hu - Timber Design Society

2.2.2 Subjective Evaluation
The key objective of the subjective evaluation of
vibration performance is to define the maximum
annoying vibration level that can be acceptable to the
majority of occupants of residential floors.
To more closely mimic normal living conditions during
subjective performance evaluations, the CLT floor
assemblies were carpeted and furnished with a cabinet
and two vases filled with water and flowers, as shown in
Figures 5 and 6. The reason for decorating the china
cabinet using flowers and water is because these objects
are good indicators of floor excessive vibrations. If the
floor is vibrating at high level when a person is walking
by the cabinet, he/she will notice the flower and the
water moving. In Figure 6, you also can see some kind
of china cabinet with glassware. It has been observed
that the glassware in the china cabinet is another good
indicator of excessive vibrations. Typically, with poor
floors, one can easily notice the rattling of glassware in
the room. In these Figures, you could also see a chair
located in the centre of the floor. During the subjective
evaluation, if the person is sitting on the chair and feels
the floor vibrating when someone is walking by the
chair, then the floor vibration is most likely not
acceptable.
Figure 6: Subjective evaluation while the evaluator is
sitting, feeling, and observing the floor movement
The evaluator was then asked to sit on the chair, while
another person would walk on the floor according to a
pre-designated pattern (Figure 6). The walking pattern is
such that the person walks at least two times along the
two diagonal directions from one corner of the floor to
the other, then walks at least two times along the middle
lines in the parallel and perpendicular directions of the
subfloor panels. Again the evaluator was observing the
three clues, i.e. seeing, hearing and feeling regarding
floor vibration performance. Immediately after the
evaluation, the evaluator is asked to fill out a
questionnaire which provided an overall performance
rating for the floor as well as a score for the three key
performance-related clues.
2.2.3 Static Concentrated Load Test
This test was conducted to determine the maximum
static deflection of the floor under a 1 kN concentrated
static load. This is a measure of the entire stiffness of the
floor.
Figure 5: Subjective evaluation while the evaluator is
walking, feeling, and observing the floor movement
At least twenty persons were asked to evaluate the
performance of a floor subjectively. Only one evaluator
was allowed on the floor at a time. He or she first walked
freely on the floor while observing clues related to floor
performance (Figure 5). The clues included movement of
the flowers and the water, rattling of the china cabinet,
and feeling the movement of the floor.
The basic elements needed to measure static deflection
under a concentrated load are: 1) a stable reference from
which to measure floor movement, 2) an accurate and
sensitive deflection measuring device, and 3) a mobile
loading system. In this study, the concrete ground floor
was used as the reference. Two electronic gauges having
a resolution of 0.001 mm were used as the deflection
measuring devices as shown in Figure 7. The deflection
gauges were mounted to the free ends of two rods in
contact with the concrete ground floor surface. The end
of one deflection gage was fixed to the bottom of the
middle point of the centre CLT panel to measure the
static deflection of the floor centre. The end of the
second deflection gauge was fixed to the bottom of the
middle point of the joint of two CLT panels to measure
the static deflection of the joint. The concentrated static
load was applied by a person standing over each CLT
panel’s centre, floor edges and the joints in turn while
recording the measurement at the gauge location. Figure
8 shows the static loading process using the tester’s
weight. The deflection profile of the floor was generated
from a complete set of measurements. Three