3rd & 4th 7-ROW BRICK SPECIMEN TEST 13/07/05

Construction of the specimens
The third and fourth 7-rows brick specimens were built identically (i.e. followed the same numbering order).

Loading pattern

3rd Specimen: Fixed 15Hz fixed frequency
The specimen was loaded at fixed frequency of 15Hz, slowly increasing over 8minutes the maximum displacement amplitude till collapse of one of the wall leaves. The maximum acceleration was 0.25g. This tests proves that high frequency / low energy waves can cause significant damage.

4th Specimen: Time History - System Resonance
A generated time history was used to load the specimen. The amplitude of the maximum displacements was gradually increased until the shake table went into resonance causing major deformation of the specimen. After the resonance, the specimen was again loaded with the same time history at increasing maximum displacements. The irregularity of the time history seemed to cause more damage the sinusoidal loading.
See time history detail

Test observations:

3rd Specimen
-At 15Hz the infill consolidation was significant starting from 0.05g and major around 0.2g
-Between 0.2-0.25g the bricks started to move with respect to each other, deforming the wall leaves.
-The "strong" leave failed first, most probably due to the deformation suffered during the test

4th Specimen
-Significant compaction was observed even at small amplitudes of the time history
-The system resonance caused both leaves to displace outwards vertically and the leaves to slightly "buckle" out-of-plane.
-Further time history loading increased the inter-block displacement and the buckling of the leaves

3rd & 4th SONE WALL DYNAMIC TEST 11/07/05
Frequency: 20Hz/0.53g - Resonance

Construction of the specimens

The third and fourth stone specimens were built with similar but not identical dimensions as the previous two specimens.

Loading pattern

Both specimens were to be loaded at fixed frequency of 20Hz, slowly increasing the maximum displacement amplitude. In both cases the system went into resonance, with a peak acceleration of 0.6 - 0.07(noise) = 0.53g. It is assumed that the frequency during the system resonance did not vary much (the system's natural frequency is around 18Hz).
The second specimen was loaded at 1, 5, 15 for a short period of time and small amplitude before loading it at 20Hz. The system resonance caused a big jump, from 0.05g to 0.53g in the acceleration, which prevented testing the specimen's behavior at high frequency and low acceleration.

Test observations:

-Both specimens were stable at 20Hz and less than 0.04g
-Both specimens failed at 20Hz (?) and 0.53g due to the shake table going into resonance
-The failure of both specimens was mainly due to shear fluidification
-The video of the 4th stone specimen shows how the stones "flow" due to shear loss

2nd SONE WALL DYNAMIC TEST 05/07/05
Frequencies: 2nd Specimen: 7 to 19Hz

Download Test Video 2nd Stone Specimen

Construction of the specimen

The second stone specimen was built (Fig. 1,4) with similar but not identical dimensions (Fig. 3) as the first specimen. In spite of numbering the individual stones, it was found difficult to follow the same order (Fig. 1) and obtain an acceptable specimen. In future tests, the stone specimens should be built with uniformly shaped stones to ensure consistency between specimens and tests.

Loading pattern

The specimen was loaded from 7 to 19Hz, with a maximum acceleration of 0.38g. At each frequency the displacement amplitude was increased gradually over a period of about 2 minutes. Due to the fact that at higher frequencies the readings of the displacement were not clear, the accelerometer's output voltage was recorded (Fig. 5) and used to find the acceleration.


Test observations:

-At 7Hz, 0.11g the specimen was stable
-At 9Hz, 0.12g some stone dislocations were observed
-At 11Hz, 0.17g the main failure occurred, but one part of the wall remained stable
-At 13Hz, the flow rate of the gravel infill increased
-At 15Hz, a second failure occurred
-At 17-19Hz, stones moved around

1st SONE WALL DYNAMIC TEST 05/07/05
Frequencies: 1 to 19Hz

Download Test Video 1st Stone Specimen

Construction of the specimen

The two stone specimens were built (Fig. 2,4) with similar but not identical dimensions (Fig. 3). In spite of numbering the individual stones, it was found difficult to follow the same order (Fig. 1) and obtain an acceptable specimen. In future tests, the stone specimens should be built with uniformly shaped stones to ensure consistency between specimens and tests.

Loading pattern

The specimen was loaded from 1 to 19Hz with a maximum acceleration of 0.5g (Fig. 3). At each frequency the displacement amplitude was increased gradually. The total testing time was about 20 minutes

Test observations:

-At frequencies between 1 and 5Hz and max. acceleration of 0.05g the specimen was stable
-At 7Hz the specimen showed some deformation
-At 9Hz, 0.1g a partial failure occurred
-At 11Hz, 0.36g the main failure occurred
-From 13-19Hz minor stone movement

2nd 6-ROW BRICK DYNAMIC TEST, Frequencies: 7- Hz, 04/07/05

Construction of the specimen

The specimen was built to a height of 6 rows, which was 3 rows less than the average static failure height of 9 row, and 3/4" was was introduced all the way to the 7th row as infill.

Loading pattern

The specimen was loaded at 7 and 9Hz and a maximum acceleration of 0.14g (Fig.3). At each frequency the displacement amplitude was increased gradually over a period of 3 minutes.

Test observations:

-At 7Hz shear fluidization / compaction was observed
-At 9Hz the rate of shear fluidization increased and the wall deformed.

1st 6-ROW BRICK DYNAMIC TEST, Frequencies: 1-9 Hz, 04/07/05

Download Test Video of 1st 6-Row Specimen

Construction of the specimen

The specimen was built to a height of 6 rows, which was 3 rows less than the average static failure height of 9 row, and 3/4" was was introduced all the way to the 7th row as infill.

Loading pattern

The specimen was loaded at1, 2, 7Hz and a maximum acceleration of 0.2g. At each frequency the displacement amplitude was increased gradually to a maximum of 1mm..

Test observations

-Between 1 and 5Hz no significant compaction/shear fluidization was observed
-At 7Hz the compaction was significant
-At 9Hz the shake table system resonated and the specimen failed in sliding

1st and 2nd 7-ROW BRICK DYNAMIC TEST 04/07/05
1st: Frequencies: 1-7Hz
2nd: Frequencies: 7-10Hz

Download Test Video of 1st 7-Row Specimen

Construction of the specimens

The two specimens were built to a height of 7 rows, which was 2 rows less than the average static failure height of 9 row, and 3/4" was was introduced all the way to the 7th row as infill. To maintain the consistency among the different specimens the individual bricks were numbered.
To facilitate the observation of the infill behavior its lateral restraint was made with Plexiglas.

Loading pattern

The first specimen was loaded at 1, 3, 5, and 7Hz and a maximum acceleration of 0.21g. At each frequency the displacement amplitude was increased gradually over a time period of 2-3 minutes to a maximum of 1mm, except for 1Hz to 1.5mm (Fig. 5).
The second specimen was loaded at 7 and 9Hz and a maximum acceleration of

Observations made during the dynamic test of the 1st specimen:

-At 1 and 3Hz the infill did almost not seem to compact.
-At 5Hz very significant compaction was observed and some infill was added.
-At 7Hz it seemed that the rate of compaction diminished. Lateral sliding of the left leaf could be observed.

Observations made during the dynamic test of the 2nd specimen:

-At 7Hz there was shear fluidization
-At 10Hz the rate of shear fluidization as well as the deformation of the wall increased

DYNAMIC TEST BRICK WITHOUT INFILL: 02/0705

Construction of the specimen

The specimen was built to a height of 7 rows, which was 2 rows less than the average static failure height of 9 rows. To maintain the consistency among the different specimens the individual bricks were numbered. No infill was used in this test.

Test Setup

The test setup on the 1 DOF shake table had the following characteristics:
-The specimens were built aligned with the line of motion/acceleration
-Two angles, one on each side, were welded to the table platform to prevent the specimen from sliding along the base
- The in-plane boundary to retain the gravel was built using t-sections and plexiglas. The plexiglas allows to see the general behavior of the infill and measure its settlement.
-Instrumentation: the shake table was instrumented with an accelerometer and a LVDT.

Preliminary adjustments

To ensure that the shake table received the same signal as the one programmed, the following preliminary runs were done with the actuator and the shakeable without the specimen:

1. Actuator
The signal was sent to the actuator alone, which had an accelerometer fixed to it, and the acceleration of the actuator (video) was measured and compared to the programmed acceleration.

2. Fine-tuning of the shake table
A series of tests were run at different frequencies to compare the input parameters to the readings obtained. These parameters included acceleration and displacement. The tests were initiated at a frequency of 1Hz and zero displacement. The displacement/acceleration was gradually increased maintaining the frequency constant, up to a maximum acceleration of 1g. This operation was repeated at 2, 5, 10, 20, and 30Hz.

The results showed that the input parameters matched the readings with a average error maximum error of 5%. In addition a frequency sweep test, 1-35Hz was run.

Loading pattern

Initially, it was decided that the loading pattern for the first dynamic test was going to be a frequency sweep from 1 to 35Hz at constant displacement of 0.5mm and the duration of each frequency was to be set at 2sec. This loading could not be applied because during the frequency sweep the actuator-shake table system got into resonance and started vibrating out of control. It was decided to manually adjust the frequency and then increase the displacement/acceleration.

Dynamic test

The table shows the loading used during the first dynamic test experiment. During the test the following observations were made:

-At 2Hz the "weaker" leave of the wall started oscillating out-of-plane (perpendicular to the motion of the table) and the "stronger" oscillated in plane. This oscillation was due to the irregularities in the blocks used.
-At 3Hz the top blocks started to rotate with respect to the other blocks
-At 4Hz the "stronger" (stiffer) of the two leaves started oscillating out of plane
-At 5Hz the bricks started to displace with respect to each other

I believe that this behavior was the result of the irregularities in the shape of the bricks. This seems to confirm that in the case of irregular stone masonry the stones will also dislodge themselves.

BRICK STATIC TESTS

Download Static Failure Video

Two UR dry brick masonry specimens were built and tested statically. The average static failure height will be used as a reference for the dynamic tests, which will be conducted at height 1-2 rows lower than the static failure height.

Construction procedure

1. The specimens where built up to a height of 9 rows
2. The infill (2/3") was introduced up the seventh row
3. Rows 8 and 9 were removed and the stability of the specimen was checked
4. Rows 8 and 9 were put back on the specimen and a 10th row was added
5. Additional infill was added to a total height of 7 1/2 rows
6. Rows 9 and 10 were removed and the specimen stability was checked
... This procedure was followed till the static failure by overturning of one of the specimen leaves occurred.

To ensure consistency among the different specimens, the individual bricks where numbered and the specimens where built keeping the same numbering order

Static test failure height:
First test: 8 1/2 rows
Second test: 9 1/2 rows

2nd specimen @ 8 1/2