Abdeldjelil
"DJ" Belarbi, Ph.D., P.E., Lesley Sneed, Ph.D., P.E., and Young-Min
You, Ph.D., P.E.
The use of precast-prestressed concrete panels is popular in the construction of concrete bridge decks. For composite decks consisting of precast panels and cast-in-place topping, partial-depth precast-prestressed concrete panels can serve as formwork for the cast-in-place concrete slabs and accelerate the construction of bridge decks in a cost-effective way. Traditionally these panels are reinforced with mild steel temperature reinforcement in the traffic direction along with lowrelaxation seven wire steel prestressing strands perpendicular to the traffic direction (along the span length of the panel).
This research has examined spalling of several partial-depth precast prestressed concrete bridge decks. It was recently observed that some bridges with this panel system in the MoDOT inventory have experienced rusting of embedded steel reinforcement and concrete spalling issues in the deck panels. Hence, an investigation was initiated to determine the causes and development of solutions including alternate design options for these panels.
As part of this research, a survey of transportation agencies was conducted to determine the extent of use of precast-prestressed concrete bridge deck panels and to compare the behavior of these systems. To comprehend fully and define accurately the cause of the spalling problem observed in partial-depth precast prestressed concrete bridge deck panels, a series of investigations of bridge decks with the bridge deck paneling systems was also conducted. Findings from the field investigations indicated that spalling observed in the precast prestressed concrete panels is the result of the penetration of water and chlorides through the transverse reflective cracking in the cast-inplace (CIP) topping at the panel joint locations, to the interface between the CIP topping and the precast prestressed concrete panels, then through the precast prestressed concrete panels to the prestressing tendons located near the panel joints. Because of the deicing frequency and tactics used by MoDOT, routing and sealing treatment was recommended on a regular basis for transverse reflective cracks at the panel joint locations. This treatment is particularly critical for full-depth transverse cracks and at the girder positive moment regions, where relatively lower levels of CIP topping reinforcement are used (compared with negative moment regions).
Panel deck system modifications evaluated for potential use in new construction included an increase in tendon side cover, the addition of fibers or corrosion inhibitor to the panel concrete mixture, an increase in reinforcement in the cast-in-place concrete topping, and the substitution of edge tendons with epoxy-coated steel or carbon fiber reinforced polymer tendons. These modifications were investigated in terms of structural performance and serviceability with respect to the current design. Efficiency of the proposed solutions was examined and validated through fundamental laboratory studies and numerical simulations using finite element modeling. Of the system modifications evaluated in this research, increase in side cover was found to be the most effective for new construction in terms of cost and constructability. Increase in reinforcement in the cast-in-place concrete topping slab and substitution of panel edge tendons with epoxy-coated steel or carbon fiber reinforced polymer tendons were also found to be effective, although more costly.
The use of precast-prestressed concrete panels is popular in the construction of concrete bridge decks. For composite decks consisting of precast panels and cast-in-place topping, partial-depth precast-prestressed concrete panels can serve as formwork for the cast-in-place concrete slabs and accelerate the construction of bridge decks in a cost-effective way. Traditionally these panels are reinforced with mild steel temperature reinforcement in the traffic direction along with lowrelaxation seven wire steel prestressing strands perpendicular to the traffic direction (along the span length of the panel).
This research has examined spalling of several partial-depth precast prestressed concrete bridge decks. It was recently observed that some bridges with this panel system in the MoDOT inventory have experienced rusting of embedded steel reinforcement and concrete spalling issues in the deck panels. Hence, an investigation was initiated to determine the causes and development of solutions including alternate design options for these panels.
As part of this research, a survey of transportation agencies was conducted to determine the extent of use of precast-prestressed concrete bridge deck panels and to compare the behavior of these systems. To comprehend fully and define accurately the cause of the spalling problem observed in partial-depth precast prestressed concrete bridge deck panels, a series of investigations of bridge decks with the bridge deck paneling systems was also conducted. Findings from the field investigations indicated that spalling observed in the precast prestressed concrete panels is the result of the penetration of water and chlorides through the transverse reflective cracking in the cast-inplace (CIP) topping at the panel joint locations, to the interface between the CIP topping and the precast prestressed concrete panels, then through the precast prestressed concrete panels to the prestressing tendons located near the panel joints. Because of the deicing frequency and tactics used by MoDOT, routing and sealing treatment was recommended on a regular basis for transverse reflective cracks at the panel joint locations. This treatment is particularly critical for full-depth transverse cracks and at the girder positive moment regions, where relatively lower levels of CIP topping reinforcement are used (compared with negative moment regions).
Panel deck system modifications evaluated for potential use in new construction included an increase in tendon side cover, the addition of fibers or corrosion inhibitor to the panel concrete mixture, an increase in reinforcement in the cast-in-place concrete topping, and the substitution of edge tendons with epoxy-coated steel or carbon fiber reinforced polymer tendons. These modifications were investigated in terms of structural performance and serviceability with respect to the current design. Efficiency of the proposed solutions was examined and validated through fundamental laboratory studies and numerical simulations using finite element modeling. Of the system modifications evaluated in this research, increase in side cover was found to be the most effective for new construction in terms of cost and constructability. Increase in reinforcement in the cast-in-place concrete topping slab and substitution of panel edge tendons with epoxy-coated steel or carbon fiber reinforced polymer tendons were also found to be effective, although more costly.
No comments:
Post a Comment