Chapter 20 — Rehabilitation, Preservation, and Life-Cycle Design (8 questions)

The FHWA Bridge Preservation Guide (HIF-11-042) places preservation, rehabilitation, and replacement in a strict priority hierarchy. Which statement most accurately captures the intent of that hierarchy at the network level?

A concrete deck without preservation deteriorates linearly from NBI = 9 at year 0 to NBI = 4 at year 40. A cyclic preservation program applied at years 12, 24, 36 raises the current rating by +1.2 at each application. Assuming the same underlying decline rate between applications, at what age (years) does the preserved deck first drop below NBI = 5?

A 2-inch LMC overlay (γ = 145 pcf) is placed on an existing interior girder deck at spacing S = 8.0 ft. Compute the additional distributed dead load on the girder due to the overlay (kip/ft).

Using ACI 440.2R, size a CFRP wrap on the circular RC column shown. Compute the number of plies n required to develop a confining pressure f_l = 0.60 ksi. (Round up to the next whole ply.)

An external post-tensioning tendon is installed on a simple-span girder. After all losses P_eff = 250 kips and the eccentricity at midspan is e = 18 in. Compute the midspan relief moment ΔM (k-ft) contributed by the tendon.

Alternative B — preservation + rehab: spend $0.20 M at year 0, $0.60 M at year 15, then $2.00 Mreplacement at year 40. Compute the NPV of Alternative B at a real discount rate r = 4 % (report as $M, positive number, two decimals).

For the retrofitted composite girder shown, compute the Design Inventory rating factor RF_Inv per AASHTO MBE §6A.4.2 using the values on the reference card. Report to two decimal places.

A Category E′ welded-attachment detail on a steel girder is cracked and is retrofitted with a drill stop-hole at the crack tipfollowed by a slip-critical bolted cover splice across the cracked flange (see figure). Per AASHTO §6.6.1.2 / FHWA fatigue retrofit guidance, which statement is most correct?