Precast Bent System for High Seismic Regions: Laboratory Tests of Column-to-Footing Socket Connections

APPENDIX C: DAMAGE PROGRESSION

Specimen SF-1

Photo shows flexural cracks in the precast column.

Figure 122. Photo. Specimen SF-1 flexural cracks after cycle 4-1 (+1.00/-1.00 target drift ratio).

Photo shows first significant spalling that occurred in cycle 6-2.

Figure 123. Photo. Specimen SF-1: first significant spalling at cycle 6-2 (+2.48/-2.48 target drift ratio).

Damage in the plastic hinge region increased with cycling.

Figure 124. Photo. Specimen SF-1: plastic hinge became more pronounced in subsequent cycles. Photo taken during cycle 8-1 (+4.28/-4.28 target drift ratio).

Figure 125. Photo. Specimen SF-1: first noticeable bar buckling was the N-NW bar in cycle 9-2 (+7.40/-7.40 target drift ratio).

$Photo shows N-NE bar fractured on the north side of specimen SF-1.$

Figure 126. Photo. Specimen SF-1: N-NE bar fractured first when the column was loaded to peak in cycle 10-2 (+10.65/-10.65 target drift ratio).

Photo shows plastic hinge region in specimen SF-1.

Figure 127. Photo. Specimen SF-1: damage after the cyclic testing.

No damage was observed in the spread footing after cyclic testing.

Figure 128. Photo. Specimen SF-1: no damage to the footing was observed after the cyclic testing.

After cyclic testing, the column was pushed axially in an attempt to punch the precast column through the spread footing. The column crushed at 842 kips load before the column could punch through the spread footing.

Figure 129. Photo. Specimen SF-1: damage the end of testing. The column crushed after application of vertical load of 842 kips.

Specimen SF-2

Figure 130. Photo. Specimen SF-2: flexural cracks after cycle 3-2 (+0.83/-0.83 target drift ratio).

Photo shows first significant spalling, which occurred in cycle 7-1.

Figure 131. Photo. Specimen SF-2: first significant spalling at cycle 7-1 (+2.97/-2.97 target drift ratio).

Photo shows the column fully spalled after cycle 8-1.

Figure 132. Photo. Specimen SF-2: the column fully spalled after cycle 8-1 (+4.28/-4.28 target drift ratio).

Photo shows first noticeable bar buckling observed in cycle 9-3.

Figure 133. Photo. Specimen SF-2: first noticeable bar buckling was the N-NW bar in cycle 9-3 (+7.40/-7.40 target drift ratio).

$Photo shows N-NE bar fractured on the north side of specimen SF-2.$

Figure 134. Photo. Specimen SF-2: N-NW bar fractured first when the column was being loaded to peak in cycle 10-2 (+10.65/-10.65 target drift ratio).

Photo shows the plastic hinge region of specimen SF-2 after cyclic testing.

Figure 135. Photo. Specimen SF-2: damage after the cyclic testing.

Figure 136. Photo. Specimen SF-2: no damage to the footing was observed after the cyclic testing.

After cyclic testing, the column was pushed axially in an attempt to punch the precast column through the spread footing. The column crushed at 819.5 kips load before the column could punch through the spread footing.

Figure 137. Photo. Specimen SF-2: damage the end of testing. The column crushed after application of vertical load of 819.5 kips.

Specimen SF-3

Photo shows horizontal crack formed near the column-to-footing interface.

Figure 138. Photo. Specimen SF-3: significant horizontal crack in cycle 3-1 (+0.69/-0.69 target drift ratio).

Photo shows separation at the column-to-spread footing interface.

Figure 139. Photo. Specimen SF-3: separation at column-footing interface in cycle 5-3 (+1.72/-1.72 target drift ratio).

Photo shows first diagonal crack forming in cycle 6-1.

Figure 140. Photo. Specimen SF-3: first diagonal cracking in cycle 6-1 (+2.06/-2.06 target drift ratio).

Photo shows first column spalling forming in cycle 6-2.

Figure 141. Photo. Specimen SF-3: first column spalling in cycle 6-2 (+2.48/-2.48 target drift ratio).

Specimen SF-3 had a thin footing, while specimens SF-1 and SF-2 had thick footings.

Figure 142. Photo. Specimen SF-3: radial footing crack propagation in cycle 6-2 (+2.48/-2.48 target drift ratio).

Photo shows a large horizontal crack about 8 inches above the interface in cycle 6-2.

Figure 143. Photo. Specimen SF-3: large horizontal crack in cycle 6-2 (+2.48/-2.48 target drift ratio).

Photo shows a large column flexural crack forming near the column-to-spread footing interface. Cracks are forming about 2 inches, 8 inches, and 12 inches above the interface.

Figure 144. Photo. Specimen SF-3: large column flexural cracks occurring in cycle 7-2 (+3.57/-3.57 target drift ratio).

Full spalling was reached in cycle 9-1. Full spalling reached 8 inches above the column-to-spread footing interface.

Figure 145. Photo. Specimen SF-3: full column spalling in cycle 9-1 (+6.16/-6.16 target drift ratio).

First spalling in the footing occurred near the column-to-spread footing interface on the north side.

Figure 146. Photo. Specimen SF-3: first footing spalling in cycle 9-2 (+7.40/-7.40 target drift ratio).

Transverse steel (spiral) first became visible in cycle 9-3.

Figure 147. Photo. Specimen SF-3: transverse steel exposed in cycle 9-3 (+7.40/-7.40 target drift ratio).

Longitudinal bar became first visible in cycle 9-3 near the column-to-spread footing interface.

Figure 148. Photo. Specimen SF-3: first exposure of longitudinal reinforcement in cycle 9-3 (+7.40/-7.40 target drift ratio).

$Longitudinal bar fracture was observed in cycle 10-1.$

Figure 149. Photo. Specimen SF-3: fracture of transverse reinforcement in cycle 10-1 (+8.87/-8.87 target drift ratio).

Major footing spalling occurred in cycle 10-1.

Figure 150. Photo. Specimen SF-3: major footing spalling occurring in cycle 10-1 (+8.87/-8.87 target drift ratio).

Figure 151. Photo. Specimen SF-3: major cracks in the concrete core in cycle 10-2 (+10.65/-10.65 target drift ratio).

Photo shows the condition of the specimen before the last cycle. The column had hinged above the foundation, and major spalling occurred in the thin spread footing.

Figure 152. Photo. Specimen SF-3: condition of specimen just before last cycle.

In cycle 10-3, the specimen punched through the thin spread footing in a combined punching shear and moment transfer.

Figure 153. Photo. Specimen SF-3: column after punching through in last cycle (cycle 10-3, +10.65/-10.65 target drift ratio).

Photo shows the condition of the plastic hinge region after the column had punched through the thin spread footing.

Figure 154. Photo. Specimen SF-3: column after punching though in last cycle (cycle 10-3, +10.65/-10.65 target drift ratio).