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From page 188... ... 186 4.1 introduction This chapter provides essential information and steps to be considered in developing a bridge-deck system for a particular project in order to meet both strength and service life requirements. Section 4.2 describes various deck systems and their known advantages and disadvantages, as summarized in Table 4.1. Read the entire page →
From page 189... ... 187 Chapter 4. BRiDGE DECKS BRiDGE DECKS the main system used in the United States, are further described in this chapter. Read the entire page →
From page 190... ... 188 DESiGN GUiDE FOR BRiDGES FOR SERviCE LiFE 4.2.1.1 Cast-in-Place Concrete Systems on Beams or Stringers As shown in Figure 4.1, CIP bridge decks on beams or stringers are typically reinforced with mild steel reinforcement. They are generally 7.5 to 9 in. Read the entire page →
From page 191... ... 189 Chapter 4. BRiDGE DECKS weight of the bridge. Read the entire page →
From page 192... ... 190 DESiGN GUiDE FOR BRiDGES FOR SERviCE LiFE Precast concrete deck panel systems include both transverse and longitudinal slots for connections. The transverse slots are typically grout-filled keyways connected in a manner similar to the adjacent-member bridge systems. Read the entire page →
From page 193... ... 191 Chapter 4. BRiDGE DECKS 4.2.2.1 Metal Grid Decks A metal grid deck system is a prefabricated module system consisting of main I- or T-shaped sections and secondary crossbars combined to form a rectangular or diagonal pattern. Read the entire page →
From page 194... ... 192 DESiGN GUiDE FOR BRiDGES FOR SERviCE LiFE The orthotropic deck has been most commonly used in the United States for longspan bridges in which the minimization of dead load is paramount and for redecking bridges on urban arterials. Orthotropic construction has tremendous potential for use in short- to medium-span girder bridges. Read the entire page →
From page 195... ... 193 Chapter 4. BRiDGE DECKS 4.2.3 timber Bridge Decks Timber bridge decks have been used for hundreds of years, but increases in vehicle loads have typically restricted their use to low-volume roadways. Read the entire page →
From page 196... ... 194 DESiGN GUiDE FOR BRiDGES FOR SERviCE LiFE overlay adherence to the FRP material was noted in early applications of this technology. Connections for crashworthy barriers for FRP decks present additional challenges. Read the entire page →
From page 197... ... 195 Chapter 4. BRiDGE DECKS Many interrelated factors during the design, construction, and management phases of a bridge deck's service life must be considered in developing long-lasting, cost-effective bridge decks. Read the entire page →
From page 198... ... 196 DESiGN GUiDE FOR BRiDGES FOR SERviCE LiFE 4.3.1.1.1 Traffic-Induced Loads Traffic-induced loads include the effects of truck and other vehicular traffic on the riding surface of the bridge. Bridge-deck loading has a degree of uncertainty that must be addressed during the design of the bridge, especially when achieving long service life is an objective. Read the entire page →
From page 199... ... 197 Chapter 4. BRiDGE DECKS Wear and abrasion. Read the entire page →
From page 200... ... 198 DESiGN GUiDE FOR BRiDGES FOR SERviCE LiFE 4.3.1.2 Natural or Man-Made Hazard Bridge-Deck Considerations The environment to which the bridge deck is subjected can have a significant influence on its service life. Environmental influences comprise hazards from both natural and sources and include effects from areas with adverse thermal climate, climates, and chemical climates, as well as from chemical properties of the materials and outside agents, such as fire. Read the entire page →
From page 201... ... 199 Chapter 4. BRiDGE DECKS to the traffic railing barriers bounding the bridge. Read the entire page →
From page 202... ... 200 DESiGN GUiDE FOR BRiDGES FOR SERviCE LiFE 4.3.1.2.4 Reactive Ingredients Reactive ingredients within the mix used for bridge decks can affect service life performance as the reactive ingredients alter the volumetric stability of the concrete. These influences primarily occur naturally. Read the entire page →
From page 203... ... 201 Chapter 4. BRiDGE DECKS The traditional design method assumes flexural action to describe the behavior of bridge-deck spanning between supporting girders and ignores the axial forces created in the bridge deck as a result of arching action. Read the entire page →
From page 204... ... 202 DESiGN GUiDE FOR BRiDGES FOR SERviCE LiFE significantly reduce the need for reinforcement in the bridge deck, and reduction of reinforcement in the bridge deck significantly reduces the sources of corrosion. Research in Canada in the past 20 years (Newhook and Mufti 1996) Read the entire page →
From page 205... ... 203 Chapter 4. BRiDGE DECKS 4.3.1.3.1b Expansion Joints Expansion joints are provided to relieve system-framing restraints that can cause a buildup of tension stresses in the superstructure and the bridge deck. Read the entire page →
From page 206... ... 204 DESiGN GUiDE FOR BRiDGES FOR SERviCE LiFE The reason for the observed differential displacement shown in Figure 4.13 is illustrated in Figure 4.14, which shows the displacement of the Phase 1 girders due to creep and shrinkage. At about 90 days after completion of Phase 1, the girders experience maximum creep and shrinkage displacement. Read the entire page →
From page 207... ... 205 Chapter 4. BRiDGE DECKS When the deck elevations of the two phases do not match, the contractor may attempt to force the two separate superstructure portions together. Read the entire page →
From page 208... ... 206 DESiGN GUiDE FOR BRiDGES FOR SERviCE LiFE Creep and shrinkage. The creep and shrinkage properties of concrete mixes can affect the service life performance of bridge decks. Read the entire page →
From page 209... ... 207 Chapter 4. BRiDGE DECKS Handling of concrete affects the final product. Read the entire page →
From page 210... ... 208 DESiGN GUiDE FOR BRiDGES FOR SERviCE LiFE concrete. In contrast, when the deck is cast in the morning, the temperature differential between the center of the deck and the surface of deck is much higher. Read the entire page →
From page 211... ... 209 Chapter 4. BRiDGE DECKS Rather than repeat the discussion of the many performance-related service life issues inherent with concrete systems described in Section 4.3.1, this section describes the factors affecting service life specific only to precast concrete bridge-deck systems. Read the entire page →
From page 212... ... 210 DESiGN GUiDE FOR BRiDGES FOR SERviCE LiFE decisions made during the design and detailing of the bridge deck, fabrication and manufacturing requirement, quality of construction, and decisions concerning the level of inspection and testing performed during future operation and maintenance. 4.3.2.1.1 Design and Detailing Bridge-Deck Considerations Decisions made during the design and detailing phase of a bridge project can significantly influence the service life of the precast bridge deck. Read the entire page →
From page 213... ... 211 Chapter 4. BRiDGE DECKS 4.3.2.1.2 Composite Action For precast systems such as full-depth deck panels, the design philosophy addresses either a composite or a noncomposite connection of the deck panels to the supporting superstructure element. Read the entire page →
From page 214... ... 212 DESiGN GUiDE FOR BRiDGES FOR SERviCE LiFE in ill-fitting pieces that require unintended adjustments in the field, leading to spalling and other structural failures caused by localized, nonuniform contact surfaces that were not anticipated during design. 4.3.2.1.4b Transportation and Lifting Methods Precast components must be moved from the casting facility to their final position in the bridge. Read the entire page →
From page 215... ... 213 Chapter 4. BRiDGE DECKS 4.4.1 Strategies to mitigate Load-induced Effects This section addresses concrete bridge decks. Read the entire page →
From page 216... ... 214 DESiGN GUiDE FOR BRiDGES FOR SERviCE LiFE Bridge decks can also be designed for overload conditions with adequate determination of the potential for overload and the frequency of its application. Additional strength requirements for overloads can be addressed by increasing the thickness of the deck. Read the entire page →
From page 217... ... 215 Chapter 4. BRiDGE DECKS • Using low-modulus concrete mix design to allow the deck to accommodate the shrinkage strain with less tension force, which can reduce cracking. Read the entire page →
From page 218... ... 216 DESiGN GUiDE FOR BRiDGES FOR SERviCE LiFE application of prestressing, and the use of external protection systems. These enhancement strategies are described in the following sections. Read the entire page →
From page 219... ... 217 Chapter 4. BRiDGE DECKS 4.4.3.2 Concrete Mix Design The impermeability of concrete enhances the protection of bridge-deck reinforcement. Read the entire page →
From page 220... ... 218 DESiGN GUiDE FOR BRiDGES FOR SERviCE LiFE of elasticity to allow deck strain with lower tension force, and high creep to allow reduced locked-in stresses over time. Bridge-deck concrete can also be enhanced by incorporating proper materials and admixtures: • Proper cement selection. Read the entire page →
From page 221... ... 219 Chapter 4. BRiDGE DECKS 4.4.3.3 Reinforcement Selection The selection of bridge-deck reinforcement can enhance the service life of the bridge deck and increase resistance from corrosion and section loss, particularly in marine environments or in areas where deicing salts are used. Read the entire page →
From page 222... ... 220 DESiGN GUiDE FOR BRiDGES FOR SERviCE LiFE posttensioning is contingent on the proper incorporation of durability enhancements, as well. Refer to Chapter 3 for additional information on the durability concerns of posttensioned systems. Read the entire page →
From page 223... ... 221 Chapter 4. BRiDGE DECKS An important property of a sealer is its vapor transmission characteristics. Read the entire page →
From page 224... ... 222 DESiGN GUiDE FOR BRiDGES FOR SERviCE LiFE 4.4.4 Strategies to improve Production and operations Improving the performance of bridge decks relies on following proper methods and procedures during construction. The strategies to improve production and operations are included in Table 4.8. Read the entire page →
From page 225... ... 223 Chapter 4. BRiDGE DECKS If the bridge deck cannot be cast in one operation, the appropriate location of construction joints and the proper sequencing of the deck pour can improve performance. Read the entire page →
From page 226... ... 224 DESiGN GUiDE FOR BRiDGES FOR SERviCE LiFE • Using admixtures in the concrete design to increase the time to initial set until all construction activities affecting the deflection of adjacent supporting members have been completed; • Delaying the casting of the deck between adjacent phases of construction by adding a closure pour to be completed after the casting of the deck on the supporting members for both phases; and • Addressing differential shrinkage between the phase-constructed closure pours and the adjacent completed bridge phases using procedures identified in Section 4.4.2.1. 4.4.4.2 Formwork Formwork for bridge decks can be either removable or stay-in-place. Read the entire page →
From page 227... ... 225 Chapter 4. BRiDGE DECKS compounds and maintaining a wet curing environment, such as under a moist burlap covering, for 7 to 10 days. Read the entire page →
From page 228... ... 226 DESiGN GUiDE FOR BRiDGES FOR SERviCE LiFE 1b. Identify local factors aﬀecting service life. Read the entire page →
From page 229... ... 227 Chapter 4. BRiDGE DECKS Selection of the overall concrete bridge-deck system may be affected by the following factors: • Need for accelerated construction to shorten overall user impacts; • Maintenance of traffic requirements that may dictate construction staging; • Commitments made during the NEPA process, such as acceptable noise levels, access limitations, or environmental and biological limitations that may dictate a precast system; • Availability of special mix designs to provide a more durable concrete; • Availability and construction expertise to incorporate prestressing to compress the concrete, minimizing or eliminating tension in the concrete; Figure 1.18. Read the entire page →
From page 230... ... 228 DESiGN GUiDE FOR BRiDGES FOR SERviCE LiFE • Availability of and the construction expertise to incorporate internal and/or ancillary protective systems for the bridge deck; and • Ability to provide an alignment and/or a bridge drainage system to prevent ponding of water and soluble pollutants on the bridge deck. Read the entire page →
From page 231... ... 229 Chapter 4. BRiDGE DECKS After each feasible bridge-deck alternative has undergone fault tree analysis to identify all possible factors that may affect service life, the procedure continues with Process A, which is developed in Figure 4.19 and described next. Read the entire page →
From page 232... ... 230 DESiGN GUiDE FOR BRiDGES FOR SERviCE LiFE Process A includes the following steps: Step 1A Identify the individual factors affecting service life by considering each branch of the fault tree defined in Section 4.3. Step 2A For each identified factor, use the design criteria to evaluate whether the factor has an effect on the service life of the bridge deck. Read the entire page →
From page 233... ... 231 Chapter 4. BRiDGE DECKS wear and abrasion and differential shrinkage cannot easily use concrete with both high strength and a low modulus. Read the entire page →
From page 234... ... 232 DESiGN GUiDE FOR BRiDGES FOR SERviCE LiFE tABLE 4.12. bridge-deck SeLection StrAtegieS: PrecASt SyStemS Potential Deterioration Mode Material Selection and Protective Measures Selection Maintenance Mode Life-Cycle Costs Initial Long-Term Differential shrinkage and thermal restraint Low-modulus concrete, proper bearing design None Low Low Wear and abrasion Overlay and/or membrane Continual overlay replacement 5 to 20 years Medium Medium Wear and abrasion High concrete strength, hard aggregates None Low Low Wear and abrasion Sacrificial thickness and overlay Continual overlay replacement 5 to 20 years Low Medium Reinforcement corrosion Overlay and/or membrane Continual overlay replacement 5 to 20 years Medium High Reinforcement corrosion Corrosion-resistant rebar None High Low Reinforcement corrosion External protection systems Continual inspection and system maintenance High High Reinforcement corrosion Application of compression by design to eliminate tension None Medium Low Reinforcement corrosion Application of compression through posttensioning Continual inspection, supplemental posttensioning Medium Medium ASR Refer to Chapter 3 for material component–based solutions na na na ASR Blended aggregates, proper drainage None Medium Low ASR Blended aggregates, waterproof membrane, proper drainage Continual overlay replacement 5 to 20 years Medium Medium ACR Refer to Chapter 3 for material component–based solutions na na na Note: na = not applicable. Read the entire page →
From page 235... ... 233 Chapter 4. Read the entire page →
From page 236... ... 234 DESiGN GUiDE FOR BRiDGES FOR SERviCE LiFE Step 9. Alternatives Comparison and Deck System Selection The final step in the process is the comparison of bridge-deck system alternatives. Read the entire page →

From page 188...

... 186 4.1 introduction This chapter provides essential information and steps to be considered in developing a bridge-deck system for a particular project in order to meet both strength and service life requirements. Section 4.2 describes various deck systems and their known advantages and disadvantages, as summarized in Table 4.1.