CAPÍTULO IV: MARCO PROPOSITIVO
4.5 FASE II: EJECUCIÓN DE AUDITORÍA
4.5.5 Hoja de hallazgos
Similar procedures to those used in the Zoology
test were used to maintain a check on the accuracy of the recorded displacements and the repeatability of the
response of these buildings. The displacement
recording equipment was calibrated on the shaking
table three times during these tests, once at the start and finish of the test seriee and a further calib�ation check was made when the equipment was moved from the
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Physics Building to the Chemistry Building. The
relative calibration of the four horizontal meters was checked at weekly intervals by placing them together
(all aligned in the same direction) and exciting the building at several frequencies. Relative variations between the displacements determined from these tests were usuatiy attributable to a reduction in damping within a displacement meter due to the silicon oil leaking through a faulty seal and the oil surface dropping below the calibration level.
A check on the degree of response of the structure during the recording of each set of displacements was provided by one of the horizontal displacement meters located on the roof of the structure near the exciter during the tests. Sets of displacement measurements, from this reference displacement meter, for four of the test series are presented in Table 601. The
discrepancies in these measurements may be due to either variations in the response of the building
between measurements or to inaccuracies in the recording system, or possibly a combination of both.
The maximum
deviation from the average of these results is slight, being less than 2\ percent.
The absolute accuracy of the horizontal and
vertical displacement results was estimated as better than 6 percento
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Physics 1st Physics 1st Chemistry 1st Chemistry 1st
Translation Mode Torsional Mode Translation Torsional
Mode Mode
Test Displ. Test Displ. Test Displ. Test Displ.
No. No. No .. No.
PL3B 17.2 Pr3B 27.8 CLlB 14.8 CT2B 30.8 PL4Bl 17.2 Pr4B 28.4 CL2B 14�9 CT3B1 31.0 PL4B4 16.9 Pf6B1 28.8 CL3B 15.0 CT3B2 30.6 PL4B6 1 7 0 1 PI'6B2 28.6 CL4B
15.2
CT3B3 31. 1 PL5Bl 16 .. 8 Pr6B3 28.4 CL5B 15.3 CT4Bl 30.0 PL5B2 17.2 PT7Bl27.8
CL6Bl14.8
CT4B2 29.6 PL5B3 17.4 PT7B2 28. 1 CL6B2 15.0 CT4B3 30.0 PT7B3 28.0 CL7B1 1 5. 1 CT5B 30.4 PT7B4 28.4 CL7B2 15.0 CL7B3 1 5. 1 Average 1 7. 11 28025 15.02 30.44 Maximum 1. 75% 2% 1.86% 2.45% Devi- ation(units as for displacement response curves)
Typical notation - PL3B - Physics, Lateral, Test No.3, Eccentric weight B.
Table 6.1 Comparison of Displacement Measurements at Resonance from Reference Displacement
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6. 5 TEST ING PROCEDURE
The testing procedure and equipment layout was similar to that developed on the Zoology Buildingo Initial tests
were undertaken to determine points of maximum response of the individual structures, and the machine then positioned using the data obtained from these preliminary tests to examine fully each of the modes excited of the three
separate structures. Modes in which t_he three structures interacted were also excited and the shapes of these
determined. The Link structure was excited only in the north-south direction, both with the brass cover plates
over the seismic break fixed down and with these plates
unscrewed. The displacement measurements were restricted to the basement (where appropriate), ground, first,
second, fourth, sixth and roof levels generally, these being considered sufficient to obtain the displaced shape of the structure. Measurements of the vertical displace- ment were restricted to the ground and first floors and
the basement area.
The exciter and reference horizontal displacement meter were operated from within a tent adjacent to the exciter. The oscilloscripts were installed in a room on the east end for the Physics Building tests, and in a room at the west end for the tests on the Chemistry and Link structures and also when measuring the response of the structure as a whole. Both rooms were on the sixth
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floor of the buildings and were, as indicated previously, maintained at a constant temperature0 Each room was used
in turn as the test control centre, and also for storing the displacement measuring equipment when not in use.
The warm temperature of these rooms ensured that no faults occurred within the electronic equipment as a result of condensation, as happened several times in the cold damp conditions of the Zoology Building. The three mobile horizontal displacements meters (one in conjunction with the vertical displacement meter) were used to determine the various mode shapes of the structure. Communication between the three personnel operating these mobile meters and the operators of the oscilloscript and vibration
exciter was again maintained by field telephones.
Throughout these tests the D.Co amplifier of the oscilloscript was set at maximum gain and the variation in amplification of the signal from the displacement pick-up was obtained by adjusting the gain on the A.G. amplifiers of the carrier wave measuring bridges.
This system gave the more reliable results because the amplifiers of the oscilloscripts were more stable than those of the bridges due to the variable temperatures and operating conditions to which the bridges were exposed.
To determine the s.teady state response of thi.s building it proved necessary to run the exciter at a
116 constant frequency for a minimum period of two minutes before recording the vibration to ensure that the
steady state condition was obtained, the longer period being due to the large size of the structure in
relation to the Zoology Building.
Testing of the Chemistry-Physics Buildings was restricted principally to early morning (prior to
�unri�e) when there are generally still frosty conditions at this time of yearo The still conditions
were
necessary due to the effect of wind-induced vibrations both on the displacement of the structure and the
frequency of the excitero