CDT-0 CDT-1 CDT-2 CDT-3 Component

mapping

Primary components Secondary components

CDT-0 to 1 CDT-1 to 2 CDT-2 to 3 Above CDT-3

CDT-0 CDT-1 NA NA

NA indicates that these CDTs are not defined for the secondary components

Table 5.8: Component level damage state descriptions – Component Damage Thresholds (CDT) for Primary Components

CDT-0 CDT-1 CDT-2 CDT-3 Component damage states No damage Aesthetic damage Repairable minor functional damage Repairable major functional damage Component replacement

Table 5.9: Component level damage state descriptions – Component Damage Thresholds (CDT) for Secondary Components

CDT-0 CDT-1

Component damage states

No damage Aesthetic damage/

Repairable minor functional damage

Repairable major functional damage/ Component replacement

175 5.5.1 Columns

Curvature ductility, µφ, is the chosen EDP for columns. The columns in the pre

1971 design era have very poor confinement of the longitudinal reinforcement due to the large spacing between the transverse reinforcement (#4 stirrups at 12 in on center is a commonly adopted standard). It is realized that curvature ductility has its limitations in terms of applicability to non-ductile columns which is characteristic of the pre 1971 design era; it is chosen to maintain consistency, with added conservatism to the threshold values. A lot of information is available on the performance of bridge columns and experimental results pertinent to columns are documented in Veletzos et al. (2006), Berry and Eberhard (2003, 2004), Mackie and Stojadinovic (2005). Four damage states, CDT-0 through 3 are chosen and the median µφ values characterizing these damage states along

with observed damage and typically employed repair strategies are documented in Table 5.10. Pictorial representations of typical column force deformation relationships with expected damage is shown in Figures 5.8 through 5.10.

Figure 5.8: Depiction of CDTs for pre 1971 designed brittle columns (Sahs et al, 2008)

Force

Displacement CDT-0

CDT-1 _CDT-2

Figure 5.9: Depiction of CDTs for 1971-1990 era designed strength degrading column (Sahs et

al, 2008)

Figure 5.10: Depiction of CDTs for a post 1990 designed ductile column (Sahs et al, 2008)

CDT-0 Force Displacement CDT-1 CDT-2 CDT-3 Force Displacement CDT-0 CDT-1 CDT-2 CDT-3

177

Table 5.10: Median values of column CDTs along with damage description and likely emergency and permanent repair strategies

Design era

CDT level

µφ Damage description Typical emergency

repair

Typical permanent repair Pre 1971

Brittle column

CDT-0 0.80 Cracking None Seal and paint

CDT-1 0.90 Minor cover spalling anywhere along the column height

None Epoxy injection; minor concrete removal and patch; seal and paint CDT-2 1.00 Large shear cracks; major spalling; exposed

core; confinement yield (no rupture)

Shoring very likely Add Class-F jacket CDT-3 1.20 Loss of confinement; longitudinal bar buckling

or rupture; core crushing

Closure/detour; shore deck if to re-open

Replace column or bridge 1971-

1990 Strength degrading

column

CDT-0 1.00 Cracking None Seal and paint

CDT-1 2.00 Minor cover spalling anywhere along the column height

None Epoxy injection; minor concrete removal and patch; seal and paint CDT-2 3.50 Major spalling; exposed core; confinement

yield (no rupture)

Possibly shoring Major concrete removal and patch; add Class-F jacket

CDT-3 5.00 Loss of confinement; longitudinal bar buckling or rupture; core crushing; large residual drift

Closure/detour; shore deck if to re-open

Replace column or bridge Post 1990

Ductile column

CDT-0 1.00 Cracking None Seal and paint

CDT-1 4.00 Minor cover spalling concentrated at the top

and bottom of the column None Epoxy injection; minor concrete removal and patch; seal and paint CDT-2 8.00 Major spalling; exposed core; confinement

yield (no rupture)

Possibly shoring Major concrete removal and patch; add Class-F jacket

CDT-3 12.0 Loss of confinement; longitudinal bar buckling or rupture; core crushing; large residual drift

Closure/detour; shore deck if to re-open

5.5.2 Abutment Seat and Joint Seal

A detailed description of the available seat width and joint seals assembled in the seats was provided in Section 3.5.6 of Chapter 3. Bridge classes with seat abutments have a potential for unseating at the abutments. Along with columns, the seat is considered a primary component. In addition to the evaluation of unseating potential, damage to the joint seal is also monitored considering the same EDP as the unseating potential. Similar to the unseating potential associated with the abutment seat, damage to joint sealant is commonly observed in bridges after earthquakes. The joints are typically sealed with some kind of a joint sealant and damage to the sealant is considered a secondary component. The different types of joint sealants were also mentioned in Chapter 3. Bridge seat widths chronologically increased from the 4 – 12 in (S1) range in the Pre 1971 design era to 12 – 18 in (S2) range in the 1971-1990 design era and 18 – 24 in (S3) and greater than 24 in (S4) range in the Post 1990 design era. The Phase I and II retrofit programs addressed this issue by retrofitting the pre 1971 and 1971-1990 to the post 1990 seat categories by the provision of restrainers and pipe seat extenders. Therefore, all the four categories of seat widths, S1 through S4 exist in the pre 1971 design era, while categories S2 through S4 exist in the 1971-1990 design era and only the S3 and S4 categories exist in the post 1990 design era bridges. Further, the joint gap is based on the movement rating (MR) of the bridge and a joint seal (Type A or B) is typically used for joints with MR less than 2 in, and a joint seal assembly (strip or modular) is used for joints with MR greater than 2 in. Joint seals are considered in the case of all the bridge classes considered in this study. In the case of MSCC-BG bridges, due to the presence of larger gaps with MR greater than 2 in for a few bridges, the effect of gap size is investigated on the fragility curves. The displacement of the joint and damage to the seal is highly correlated with damage to the abutment backwall in the case of seat type