Design Guide for Bridges for Service Life (2013)

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415 9.1 introduction Bridge elements are subjected to various loads, including traffic and environmental loads that result in movement of the bridge elements. One of the key factors affecting the service life of bridges is how to address thermal expansion and contraction of the bridge elements. This design issue is handled in two distinct ways. One option is to provide expansion joints at designated locations within the superstructure. By doing so, the designer forces the entire thermal deformation to take place at these discrete locations. The other option is to make the superstructure and deck continuous and assume that the thermal movement will be accommodated by the flexibility of the sub- structure, such as with the use of integral abutments. In such cases, the joint is usually moved away from the bridge abutment and placed near the end of the approach slab. This chapter provides essential information for enhancing the service life of bridge expansion joints. The process begins with developing an understanding of the types of bridge joints that may be considered for a particular project. The viable expansion joint types are further evaluated for factors that adversely affect their service life, and individual strategies are developed to mitigate these adverse effects. The overall strat- egy selection is then developed, blending these sometimes-conflicting individual strate- gies. The components of an overall strategy should include • Identification of appropriate design methodologies, • Selection of durable expansion device types considering life-cycle costs, • Specification of best practices for construction, and • Development of an effective maintenance plan. 9 ExpANSiON DEviCES

416 DESiGN GUiDE FOR BRiDGES FOR SERviCE LiFE Section 9.2 describes the different types of expansion devices used in practice, as well as their various advantages and disadvantages. Section 9.3 discusses reported potential factors that could affect the service life of the different expansion devices, and Section 9.4 provides strategies for enhancing expansion device service life. 9.2 deScriPtionS oF vAriouS exPAnSion joint deviceS Many types of expansion joints exist to meet the needs of a wide array of bridge types. However, it is important for the designing engineer to select the proper expan- sion joint, as this is the most crucial step in enhancing the service life of an expansion device. When selecting the proper expansion device it is important to consider the total anticipated displacements, bridge skew, and other special considerations, such as proprietary system requirements and accommodations for deicing agents. An ideal expansion joint (Lee 1994) is able to • Accommodate thermal expansion and contraction, • Accommodate movement caused by traffic-induced loads, • Provide a smooth ride, • Prevent the creation of hazards and safety issues, • Accommodate needs during snow removal, • Prevent leaking of moisture and other chemicals to elements below the superstructure, • Have a long service life, • Be maintenance free or require minimal maintenance, and • Be cost-effective. There are many different joint types, and often the terminology used to describe them differs from agency to agency or manufacturer to manufacturer. One approach to categorizing expansion joint systems is to divide the various joints into three catego- ries on the basis of the maximum longitudinal movements that they can accommodate, as follows: 1. Expansion joints capable of accommodating small longitudinal movements (less than about 3 in.), 2. Expansion joints capable of accommodating medium longitudinal movements (be- tween 3 and 5 in.), and 3. Expansion joints capable of accommodating large longitudinal movements (in excess of 5 in.). The three types of expansion joint are described in the remainder of this section.

417 Chapter 9. ExpANSiON DEviCES 9.2.1 Expansion Joints with Small movement Capabilities 9.2.1.1 Compression Seal Joints In an expansion joint that uses a compression seal, the opening throughout the entire bridge-deck width is filled with a neoprene elastomeric section that forms a waterproof joint, as shown in Figure 9.1 (Purvis 2003). The neoprene elastomeric is installed by squeezing and inserting the seal into a preformed joint opening (Chang and Lee 2002). Steel or special concrete materials are sometimes used to strengthen the joint face. To facilitate the movement of the joint, the seals are usually made semihollow with inter- nal diagonals and vertical neoprene webs (like a truss structure). However, some types are made of closed section foam. The squeezing of the neoprene elastomeric section is meant to ensure that it will be in compression, thereby sealing the joint. Figure 9.1b shows an armored version of a compression seal joint. A recent trend within transpor- tation agencies has been to eliminate the horizontal leg of the angle used and to attach the vertical leg to the deck with shear studs. This expansion joint type allows total movement of up to 3 in. 9.2.1.1.1 Features • Movement from 0.25 to 3.0 in. is allowed. • The seal needs to be made the right size for the needed range of movement. • The semihollow cross section with the internal diagonal and vertical neoprene webbings forms a truss action that allows the section to compress toward the sides of the joints and become watertight. • Sometimes foams are used instead of semihollow cross sections; these foams form a closed section, but the movement range is the same. Figure 9.1. (a) Plain and (b) armored compression seal. Source: Purvis 2003. )b( )a( )b( )a(

418 DESiGN GUiDE FOR BRiDGES FOR SERviCE LiFE • The compression seal fits into the sides of the joint by using a lubricant material that also functions as an adhesive that bonds the seal to its place. • Splices should be avoided in this type of seal. 9.2.1.1.2 Advantages • Some agencies report minimal required maintenance and a good life span for these seals. • This type of joint is recommended mostly for areas with moderate temperature extremes. 9.2.1.1.3 Disadvantages • It is reported that large sustained compressive movement forces air from the seal material, which may not recover when the joint opening expands. • Some agencies do not report good performance for this type of seal, citing damage from debris, traffic, and snowplows. • Leakage has been reported shortly after installation. • It has been reported to dislodge and lose compression over time. • This type of joint is not recommended for extreme temperature ranges. • The seal needs to be installed at relatively low temperatures, or it is more difficult to install and prone to damage. • According to some reports, the compression seal loses its capability to retain initial compression recovery due to loss of resilience, particularly if the movement range is large. 9.2.1.2 Poured Sealants The poured sealant systems used today mainly consist of two parts: a polyethylene foam backer rod and a pourable silicone sealer (Purvis 2003), as shown in Figure 9.2. The backer rod keeps the sealant from spilling through the opening. During installa- tion, it is very important to keep the joint edges clean so that the silicone sealant bonds tightly. The performance of this type of joint will improve if it is poured when the ambient temperature is at the middle of the historical range. Traditionally, this type of joint could handle movements up to 3/16 in., but newer systems can accommodate up to 3 in. of movement (Purvis 2003; Chang and Lee 2001).

419 Chapter 9. ExpANSiON DEviCES Figure 9.2. Poured sealant joint type. 9.2.1.2.1 Features • Traditional systems were good for shorter spans on which the movement need was 3/16 in. (5 mm) or less. However, newer systems accommodate larger movements depending on the sealant material. • The most common sealant used today is silicone. 9.2.1.2.2 Advantages • This type of joint is maintaining popularity because, according to reports, newer systems are serving well if installed properly. • The silicone polymer used is self-leveling and rapid curing. • The performance of this type of seal is not affected by joint walls that are not perfectly made. • They are easy to repair. • It is easy to remove a portion of the sealant, clean the sides of the joint, and refill the joint. • The quick maintenance process makes traffic disruption very short. 9.2.1.2.3 Disadvantages • The first poured seal materials were heated asphalt or coal tar products that did not perform satisfactorily for many transportation agencies. • Polymer materials used to have problems such as debonding, splitting, and dam- age from noncompressible debris. • Earlier, damage to the deck edge also caused the joint sealant to fail.

420 DESiGN GUiDE FOR BRiDGES FOR SERviCE LiFE 9.2.1.2.4 Requirements • The thickness of the silicone at the center should be no more than half the width of the joint. • It is important that the bottom of the silicone does not bond to the material below. • Poured sealants perform best if the seal is poured when the ambient temperature (which must be above 40ºF) is at the middle of the historical range or the joint opening is at the midpoint. 9.2.1.3 Asphaltic Plug Joints Figure 9.3 shows a typical detail for an asphaltic plug joint. It is a simple detail that can be used with concrete deck overlays. In this system, a center opening around the joint is prepared (about 20 in. wide and 2 in. deep), and a steel plate is placed in the opening as shown in Figure 9.3. The asphaltic material is then placed over the steel plate to seal the joint. The maximum movement allowed by this system is about 2 in. (Pemmaraju et al. 2006; Mogawer and Austerman 2004). 9.2.1.3.1 Features • Movements less than 2 in. (50 mm) are allowed. • The system is suitable for concrete decks, especially when used with an overlay layer. • “A popular application is on decks where a waterproof membrane, topped by bituminous (asphalt) concrete overlay, has been added” (Purvis 2003). • This system may work better in restricted climate conditions. 9.2.1.3.2 Advantages • Installation and repair are easy. • Installation and repair are low cost. • There is a low susceptibility to snowplow damage. • The system can be cold milled. 9.2.1.3.3 Disadvantages • “This seal was developed almost exclusively for bridge-deck joints without curbs, barriers, parapets, etc., and does not provide an effective method of sealing joint upturns, especially for longer decks and skewed deck joints where joint movement will degrade the system, resulting in early system failure” (Purvis 2003). • Some problems have also been reported, among them are softening in hot weather, debonding of the joint–pavement interface, and cracking in very cold weather.

421 Chapter 9. ExpANSiON DEviCES Figure 9.3. Asphaltic plug joints: (a) typical detail and (b) commercially available details. Sources: (a) Mogawer and Austerman (2004) and (b) courtesy D.S. Brown. (a) (b) Source: (a) Mogawer and Austerman (2004) and (b) courtesy D.S. Brown. • In areas of heavy traffic volumes, this seal may rut or delaminate over time. • Rapid temperature changes can damage this type of seal. 9.2.1.4 Sheet Seal Joints As shown in Figure 9.4, the sheet seal joint consists of a sheet of fiber-reinforced elas- tomeric membrane tied to both sides of the joints. This joint type can accommodate up to 4 in. of longitudinal movement. The kink in the membrane allows the expansion and contraction of the joint, while keeping it watertight. This system could be used for rehabilitation of medium-span bridges. The membrane used in this system is provided in a variety of shapes, configurations, and sizes (Chang and Lee 2001).

422 DESiGN GUiDE FOR BRiDGES FOR SERviCE LiFE 9.2.1.5 Sliding Plate Joints Figure 9.5 shows a typical sliding plate joint. According to some literature (Purvis 2003), this type of joint could also be classified as an open joint, as it does allow some level of leakage while preventing most debris from passing though the opening. This system consists of a steel plate spanning an open joint and embedded in adjoining deck slabs. It can accommodate movements up to 3 in. Currently, these joint types can even handle larger movements, depending on the thickness of the plate used, and they are not used without a trough below. 9.2.1.5.1 Advantages • Sliding plate joints effectively prevent debris from passing through the opening. 9.2.1.5.2 Disadvantages • The system is noisy under traffic as a result of loosening over time. • It is prone to safety hazards due to detaching. • Anchorage problems can occur between the plate and the concrete. • Anchors can be corroded over time and are prone to fatigue damage from traffic loads. Figure 9.4. Sheet seal expansion joint. Source: Yuen 2005. Figure 9.5. Sliding plate joint system. Source: Yuen 2005.

423 Chapter 9. ExpANSiON DEviCES • Damage accumulated at the unsupported edge of the sliding plate causes a weak spot for traffic-impact loads. • Snowplow blades can damage both the sliding plate and the anchors. • The impact on the plate from traffic loads can be increased due to deterioration of the roadway surface close to the joint. • Sliding joints are not recommended for highways with considerable truck traffic loads. • It is not considered a watertight joint. 9.2.1.6 Open Joints Figure 9.6 shows an example of an open joint with trough and armoring angles. The early versions of open joints were constructed without trough and armoring angles; however, most departments of transportation (DOTs) are no longer using open joints without a trough. These joint types are best suited for small movements (less than 1 in.). Armoring provides protection against traffic impact, and the trough protects bridge elements below the joints from moisture and debris that cause deterioration. 9.2.2 Expansion Joints with medium movement Capabilities 9.2.2.1 Strip Seals Figure 9.7 shows a typical configuration for a strip seal joint. The main elements are a V-shaped membrane made using elastomeric material mechanically attached to an ex- truded metal piece anchored to the joint edges with studs (Purvis 2003). The maximum Figure 9.6. An example of an open joint with trough and armoring angles.

424 DESiGN GUiDE FOR BRiDGES FOR SERviCE LiFE Figure 9.7. Strip seal expansion joint. movement that can be accommodated by this joint system is about 5 in. (Chang and Lee 2002). Strip seal joints have gained popularity in recent years, and most DOTs are relatively more satisfied with strip seal joints than with other joint types. 9.2.2.1.1 Advantages • Strip seals are the most positively evaluated seals by agencies surveyed during the study reported in NCHRP Synthesis 319 (Purvis 2003). • The seal is watertight if properly installed. • Under desirable conditions, strip seals have a longer service life than any other kind of seal. 9.2.2.1.2 Disadvantages • Replacement is difficult. • Strip seal splices should be avoided. • Snowplow blades can damage the seal. • Problem areas for this type of seal usually occur at locations of rapid cross-section change, both in the vertical or horizontal direction of the deck, like the gutter line. • During expansion, noncompressible material at tiny cracks could create membrane tears. This material can also cause ruptures, resulting in loss of watertightness. • Occasionally, the seal comes loose from the extruded metal holding piece. 9.2.3 Expansion Joints with Large movement Capabilities 9.2.3.1 Modular Expansion Joints Modular joints were developed to accommodate large longitudinal expansion and contraction movements by combining multiple neoprene strip elements. Depending on the number of combined strips, modular joints can accommodate movement from 6 to 28 in. Modular expansion joints are mainly used for bridges with more complex

425 Chapter 9. ExpANSiON DEviCES movements. They consist of several metallic pieces, which makes them prone to fa- tigue. The modular expansion joint system consists of sealer, separator beams for seal- ers, and support bars for separator beams. Sealers can be strip, compression, or sheet seal type. Separator beams are usually extruded or rolled metal shapes to join the seals in a series. The separator beams are supported on support beams at frequent intervals (Chang and Lee 2001). Figure 9.8 shows a schematic of one commercially available modular joint. 9.2.3.1.1 Features • The system consists of three elements: sealers, separator beams, and support bars. • Modular joints are considered a closed joint system, so they protect the compo- nents below from damage due to water, salt, and other problems associated with deck runoff. • They are used for all types of long spans. It is the best alternative for large movements. 9.2.3.1.2 Advantages • They can accommodate large movements over 4 in. (100 mm); the typical move- ment is between 6 and 24 in. Figure 9.8. Modular expansion joint system. Source: Courtesy D.S. Brown.

426 DESiGN GUiDE FOR BRiDGES FOR SERviCE LiFE • They can be sized according to the magnitude of movement and have been de- signed to accommodate movements of more than 7 ft (very long span). • Joint seals have been continuously improved. • The system is improving with experience and research. New design provisions in the LRFD Bridge Design Specifications (AASHTO 2012) incorporate recent fatigue-related research. 9.2.3.1.3 Disadvantages • Problems have included fatigue cracking of welds (older designs); damage to the equalizing spring, the neoprene sealer material, and the support; and damage from snowplows. • The system is complex and must be capable of expanding and contracting to accommodate very large movements and must remain watertight while being sup- ported by a movable framing system. • The high initial and maintenance costs have caused many DOTs to return to using finger joints for large movements and placing additional emphasis on proper drainage. • There are only two primary suppliers, which limits competition. • Mixed performance results have been reported. 9.2.3.1.4 Requirements • Some agencies use modular expansion joints exclusively to accommodate large movements. • Watertightness and fatigue resistance are important considerations, and some states have developed or are developing specifications to ensure these considerations. 9.2.3.2 Finger-Plate Joints Figure 9.9 shows a typical finger-plate joint system. Two pieces of steel are anchored either to the deck or the steel superstructure and cover the joint opening. Grooves in each of the plates fit loosely together like fingers. The majority of the finger-plate joint systems in use have a trough, as shown in Figure 9.9, to catch water and debris and carry them away from the superstructure to prevent deterioration (Purvis 2003; Chang and Lee 2001). A variation of this concept is to offset the location of the finger assembly to one side of the deck opening so that the fingers from one side slide over an embedded plate in the deck on the other side. The advantage of this design is that the deck opening is covered, which limits the amount of debris that can fall through.

427 Chapter 9. ExpANSiON DEviCES 9.2.3.2.1 Features • The system consists of finger-like plates attached to both sides of the super structure and usually includes a drainage trough. • It is considered an open-joint system. 9.2.3.2.2 Advantages • These joints can accommodate large movements (over 3 in.). • The system experiences fewer durability problems in comparison with modular joints and tends to have fewer problems than many other joints. • DOTs have opted to use finger joints on longer spans. 9.2.3.2.3 Disadvantages • The upward bending of the ends of the fingers results in increased noise, a rough riding surface, and occasionally broken fingers. • The most common problem is concrete deterioration around the joint. • The only corrosion protection for the components below is the drainage trough. • Problems are usually caused by poor drainage trough design. • Cleaning and flushing are often difficult and are rarely performed. Figure 9.9. Examples of a finger-plate joint system. Figure 9.9. Examples of a finger-plate joint system.

428 DESiGN GUiDE FOR BRiDGES FOR SERviCE LiFE 9.2.3.2.4 Requirements • Watertightness and good drainage are important considerations for finger-plate expansion joints. Use of appropriate slope (minimum 1%) can easily address this requirement. • When using finger-plate expansion joints, following the installation requirements specified by the manufacture is important. • Maintenance of the trough and routinely cleaning the debris are essential when using finger-plate expansion joints. 9.3 FActorS And conSiderAtionS inFLuencing exPAnSion joint Service LiFe Joint performance is perhaps the most important factor affecting the deterioration of bridge elements. A leaky joint allows salt and other chemicals to penetrate below the deck and causes many maintenance and deterioration problems. A FHWA study (Fincher 1983) reported that over a 5-year period, more than 60% of joints evaluated were leaking water, and the other 40% had problems that were actually decreasing their service lives. Wallbank (1989) evaluated 200 concrete bridges and found leaking expansion joints to be the major cause of bridge element deterioration. The reduced service life of bridge expansion devices is primarily related to deficien- cies, which may be load induced; caused by man-made or natural hazards; or result from production defects in construction processes and/or design details or operational procedures. These deficiencies are illustrated in the fault tree shown in Figure 9.10. 9.3.1 Load-induced Expansion Joint Considerations Load-induced bridge-deck deterioration can be attributed to either loads induced by the traffic that the bridge-deck expansion device carries or characteristics dependent on the overall bridge system. These load-induced factors are introduced in the fault tree in Figure 9.11. 9.3.1.1 Traffic-Induced Load Considerations Traffic-induced loads include the effects of truck and other vehicular traffic on the rid- ing surface of the bridge. Bridge-deck loading, and thus the loading on the expansion devices, has a degree of uncertainty that must be addressed during the design of the bridge, including vehicle weights and frequency of application; vehicle axle and tire spacing; vehicle location on the deck; and variability in vehicle suspension systems, which can affect impact assumptions. The assumptions in loading must be carefully reviewed when establishing the criteria to be used and checked for bridge expansion device design. Typically the service life of bridge-deck expansion devices will be af- fected by fatigue response to repetitive loading, overload, and wear and abrasion.

429 Chapter 9. ExpANSiON DEviCES 9.3.1.1.1 Fatigue Fatigue is caused by the repetition of applied loads that result in a degradation of the strength resistance of the components used to resist tensile stresses that occur in expan- sion devices (especially in modular expansion joints and other large-movement joints). 9.3.1.1.2 Overload Despite weight limit regulations in most states that define load limits for permit and legal truck configurations, overloads exceeding these limits are not specifically con- trolled. There are few weigh stations for checking these loads, and they are usually only found on major roadway facilities, such as Interstate highways. Enforcement of the laws against these overloads on other facilities is limited to spot checks by code enforcement officials. Figure 9.10. Expansion joint reduced service life fault tree. Reduced Service Life of Bridge Deck Caused by Deficiency Caused by Obsolescence Natural or Man-Made HazardsLoad Induced Production/ Operation Defects

430 DESiGN GUiDE FOR BRiDGES FOR SERviCE LiFE Figure 9.11. Load-induced deficiency fault tree. Load Induced WearFatigue System- Dependent Loads Snow Plow System- Framing Restraint Traffic- Induced Loads ThermalOverload Figure 9.11. Load-induced deficiency fault tree. Overloads result in additional flexural stresses in bridge decks and expansion devices that can cause excessive cracking and movements not accommodated by the original design. Heavier tire loads may also affect the wear and abrasion on the struc- ture. Multiple applications of these loads can also affect the fatigue behavior of the deck expansion devices. 9.3.1.1.3 Wear and Abrasion Wear and abrasion is typically affected by high traffic volumes, high tire loads, and the types of tires used by the vehicles. In cold climates, tires may have enhanced features to aid in traction, such as deep grooves, studs, and chains. These added tire features, although they aid traction, can abrade the surface of the bridge expansion joints. 9.3.1.1.4 Snow Plow Impacts from snow plows are special considerations that need to be addressed in the selection of expansion joints. Repeated impacts from snow plows can cause expansion devices to function incorrectly and even make driving over them unsafe.

431 Chapter 9. ExpANSiON DEviCES 9.3.1.2 System-Dependent Loads System-induced loads include the effects of the bridge system configuration on the behavior of the bridge-deck expansion devices. These effects are accentuated by re- straints provided through the bridge system and bridge-deck boundary conditions and can result in significant locked-in stresses. 9.3.1.2.1 System-Framing Restraint Boundary conditions for the longitudinal and transverse restraint of bridges can result in tension that may lead to cracking in bridge decks under cold-weather conditions. These boundary condition restraints are introduced through design by the choices made relating to bearing types and their fixity and sliding assumptions. Fixed bear- ings provide an anchor that is intended to restrict “walking” of the superstructure, which results from shrinkage and cycling of expansion and contraction; they are usu- ally located longitudinally near the point of zero movement of a supported multispan superstructure unit. These fixed bearings, used in combination with bearings designed to allow the superstructure to either move or slide over the top of the substructure, reduce restraining forces that would otherwise be required to resist the movement. 9.3.1.2.2 Thermal Temperature changes can result in changes in bridge movement, which can affect the service life of expansion joints. 9.3.2 natural or man-made Hazard Considerations The environment to which the bridge deck is subjected can have a significant influence on the service life of bridge decks and consequently the expansion devices. These environmental influences include hazards from both natural and man-made sources and include effects from areas with adverse thermal climates, coastal climates, and chemical climates, as well as from chemical properties of the materials and outside agents, such as fire. These natural and man-made hazards are introduced in the fault tree in Figure 9.12. 9.3.2.1 Thermal Climate Thermal climate influences on bridge-deck expansion device service life performance are primarily due to cold-weather climates. These influences are both man-made, from the application of deicing salts, and natural, in the case of freeze–thaw. 9.3.2.1.1 Application of Deicing Salts Agencies in cold-weather climates dealing with ice and snow on roadways and bridges have traditionally applied deicing salts to melt the ice and snow to facilitate tire trac- tion on their facilities. These chloride-laden compounds can corrode expansion joint steel components.

432 DESiGN GUiDE FOR BRiDGES FOR SERviCE LiFE Figure 9.12. Natural or man-made hazards fault tree. Figure 9.12. Natural or man-made hazards fault tree. Natural or Man- Made Hazards Coastal Climate Deicing Salts Salt Spray Corrosion Corrosion- Inducing Chemicals Thermal Climate Freeze–Thaw Chemical Climate The cross slope built into bridge decks for drainage purposes causes salt to wash toward the bridge gutter adjacent to the traffic railing barriers bounding the bridge. Removal equipment that scrapes snow from the bridge deck will also deposit residual snow laden with deicing salts at this location, resulting in a very high concentration of chlorides. 9.3.2.1.2 Freeze–Thaw Spalling and cracking of the concrete deck as a result of freeze–thaw at the sites of ex- pansion joints could have adverse effects on the joint-to-deck connections and possibly on the performance of the device, as well.

433 Chapter 9. ExpANSiON DEviCES 9.3.2.2 Coastal Climate Coastal climate influences on bridge expansion joint service life performance are pri- marily due to chlorides introduced through salt spray and effects from high humidity. These influences both occur naturally. Coastal regions are subjected to a chloride-laden saltwater environment and a combination of wind and wave action that causes these chlorides to become airborne as salt spray. The susceptibility of the bridge expansion joints to these environmental influences depends on the height of the bridge deck above the water elevation. The salt spray wets the surfaces, leaving a chloride residual that can cause steel components of expansion devices to corrode. 9.3.2.3 Chemical Climate Chemical climate influences on service life performance can be attributed to corrosion- inducing chemicals or other chemicals that can have detrimental effects on exposed neoprene elements. These influences can occur naturally or can be man-made. Corrosion-inducing chemicals from adjacent industries and residuals from pollu- tion can be introduced to the bridge deck and joints and attribute to reduction in bridge expansion joint service life. As an example, oil- and coal-burning facilities release sul- fur dioxide and nitrogen oxide into the air, which cause acid rain consisting of sulfuric and nitric acids. These acids can dissolve cement compounds in the cement paste and calcareous aggregates and leave crystallized salts on concrete surfaces that can lead to spalling and the corrosion of reinforcing bars at the site of expansion devices, as well as components of the joints themselves. 9.3.3 Production and operation Bridge-Deck Considerations Decisions made for the production of bridge expansion devices and activities during the bridge’s operation can have a significant influence on the service life of bridge ex- pansion joints. These production and operation influences, which are introduced in the fault tree in Figure 9.13, include decisions made during the design and detailing of the bridge expansion joints and decisions regarding the quality of construction, the level of inspection and testing performed during operations, and maintenance implementation. 9.3.3.1 Design and Detailing Bridge-Deck Considerations Decisions made during the design and detailing phase of a bridge project can signifi- cantly affect the service life of the bridge. It is incumbent on designers to understand the implications of these decisions in order to make rational choices that will improve the service life of bridge expansion devices. 9.3.3.2 Construction Attention to good practices during construction and installation is crucial to the long- term durability of expansion devices. Well-qualified and well-trained workers and well-executed workmanship increase productivity, reduce material waste, and provide

434 DESiGN GUiDE FOR BRiDGES FOR SERviCE LiFE Figure 9.13. Production–operation and design–detailing defects fault tree. Figure 9.13. Production–operation and design–detailing defects fault tree. Production/ Operation Defects Construction MaintenanceInspectionDesign/Detailing Visual Installation Handling Expansion Joints Nondestructive Testing expected service life. Proper use of test methods is needed to ensure that quality expan- sion joints are achieved. 9.3.3.3 Maintenance Plan: Monitoring of Condition An effective maintenance plan must include provisions to adequately monitor the structure in order to identify deficiencies at an early age so that appropriate repairs can be performed before the deficiency propagates into an irreparable condition. The plan should address proper inspection, collection of data, and prompt action on reported deficiencies. 9.3.3.4 Inspection Requirements and Intervals Inspection is a valuable tool for increasing the service life of bridges. Identification of deterioration at an early stage is essential to providing corrective actions in a timely manner in order to maximize the owner’s investment in the structure. The scope and

435 Chapter 9. ExpANSiON DEviCES interval of these inspections should be calibrated on the basis of bridge expansion device performance history for the applicable deck hazard exposures. Inspection per- sonnel should be properly trained to identify this deterioration. 9.4 overALL StrAtegieS For enhAnced bridge exPAnSion jointS Service LiFe Providing bridge expansion joints with enhanced service life requires a full under- standing of the potential deterioration mechanisms. These mechanisms are associated with load-induced conditions, local environmental hazards, production-created defi- ciencies, and lack of effective operational procedures. This process is presented in this section. The intention of this section is to provide guidelines for selecting the most appro- priate individual strategy to achieve the desired service life. 9.4.1 Design methodology With limited funds available for bridge construction, first-cost economy is often an overriding factor in critical bridge joint selection decisions. However, to take advantage of the long-term advantages of durable expansion joints, service life enhancement strat- egies must apply a cascading series of economy, design, construction, and maintenance measures. The success of the strategy selection process is dependent on the ability to predict service life and the incorporation of best practices to enhance service life. 9.4.2 Expansion Joint System Selection In general, selection of bridge expansion joints is historically based on locally accepted construction practices and procedures, which result in an economical deployment. Proposed enhancements to these systems would need to be assessed on the specific long-term performance of these systems. As noted in Section 9.3, there are numerous deficiencies that result in a reduction of service life, and these conditions may not nec- essarily occur at the specific project site under consideration. It is the design engineer’s responsibility to understand local practice and its performance history and to perform sufficient investigation of the project site, its environment, and other design conditions before selecting an expansion joint and its potential enhancements. 9.4.3 Life-Cycle Cost Analysis Once a series of strategies has been developed, the evaluation of these strategies is performed through a life-cycle cost analysis, which assesses the overall long-term cost of a strategy throughout the target service life of the structure. Life-cycle cost analysis is discussed in detail in Chapter 11 of the Guide. The analysis should consider all costs associated with the construction required, implementation trials and testing, and all future maintenance actions required through the life of the structure.

436 DESiGN GUiDE FOR BRiDGES FOR SERviCE LiFE 9.4.4 Construction Practice Specifications Once the bridge expansion joint system is selected, a proper set of specifications must be developed to ensure the appropriate standard of care is used during construction. It should be noted that many agencies and manufacturers have specific requirements for temperature setting for expansion joints to allow maximum range of movements; these requirements need to be considered during design and construction. 9.4.5 maintenance Plan An effective maintenance plan must be developed to ensure the assumptions regarding maintenance upkeep made in the bridge expansion joint selection process are prop- erly identified for staff and budget requirements. If the bridge owner cannot com- mit to such a program, then strategies for low-maintenance life-cycle costs should be recommended. 9.4.6 Retrofit Practices for Expansion Devices Expansion joints in bridges are not typically retrofitted as it is common practice to replace the joints when they reach the end of their service life. Due to the perishable nature of these expansion joints, it is important that they be properly maintained in order to maximize the life of such devices. 9.4.7 technology tables for Expansion Joint Devices Table 9.1 is a series of technology tables that summarizes service life and durability is- sues related to expansion joints and aids the designing engineer in selecting the proper expansion device. The table provides service life issues related to most expansion joints used in practice. The information could be used in several ways at the design or main- tenance level. The purpose of the technology table is to identify the most common types of service life problems encountered in commonly used expansion joints; this information can subsequently be used to provide possible solutions to service life prob- lems encountered with expansion joints. A review of the technology tables indicates that the following modes of failure are observed when various expansion joints are used: • Damage to various expansion joint components, such as steel armors, as a result of snowplow usage; • Inadequate design, installation, and maintenance; • Accumulation of debris, leading to limited movement; • Lack of timely maintenance; • Limited service life; and • Leakage. The ultimate consequence of these service life problems is that joints start leaking and causing damage to bridge elements below the deck.

437 Chapter 9. ExpANSiON DEviCES tABLE 9.1. bridge jointS technoLogy tAbLeS Field-Molded (or Field-Formed) Joints Range of Movement: Less than 1 in. Expected Range of Service Life: 8 to 9 years Service Life Problem Solutions Advantages Disadvantages System Preservation Requirements Spalling and cracking of adjacent concrete Deeper notch. Field-molded joints are inexpensive and easy to install. They are best suited for single- span bridges with a maximum length of ~100 ft. This detail is an economical solution for simple-span bridges with spans of less than ~100 ft, especially in low-traffic areas where a few hours of interruption to traffic is not a major problem. It requires maintenance and has a short service life. In most cases, it needs complete replacement every 2 to 3 years. It requires regular 3-year inspection and replacement in most cases. Filling with silicone. Beveling edges of concrete. Placement of correct silicone thickness. Correctly mixing silicone material. Installation problems Training installation technicians. Providing detailed installation plans by the manufacturer or contractor. Having a representative of the joint supplier on site during installation. Snowplow damage Not allowing inferior quality of bonding agents. Installing slightly below the top of the deck elevation. Debris accumulation Inspecting and cleaning regularly. Water leakage Draining water away from the joint. Insulation. Hot-weather damage Using high-quality silicone sealer. (continued)

438 DESiGN GUiDE FOR BRiDGES FOR SERviCE LiFE tAbLe 9.1. bridge jointS technoLogy tAbLeS (continued) Plug Seal Joints Range of Movement: Less than 2 in. Expected Range of Service Life: 1.5 to 20 years Service Life Problem Solution Advantages Disadvantages Seal material does not always fill the joint completely Reapplication of the joint. Low instances of snowplow damage. Low cost of installation and maintenance. Damage due to sudden changes in temperature. Early joint failures in skewed and/or long decks Avoid the system in skewed and/or long decks. Softening in hot weather Proper selection of materials considering climate conditions. Debonding of the joint– pavement interface Reapplication of the sealant. Cracking in very cold weather Proper selection of materials considering the climate conditions. Rutting or delamination over time due to heavy traffic volumes Reapplication of the joint. (continued)

439 Chapter 9. ExpANSiON DEviCES tAbLe 9.1. bridge jointS technoLogy tAbLeS (continued) Compression Seal Joints Range of Movement: 0.25 to 2.5 in. Expected Range of Service Life: 2 to 20 years Service Life Problem Solution Advantages Disadvantages High deformation due to extreme temperature variation Use only at moderate temperature extremes. Ease of installation. Not very prone to snow plow damage. Have received very good performance ratings from various agencies. Poor workmanship, leading to service life problems, is reported. In some instances, poor workmanship has resulted in joints leaking immediately after installation. Damage due to snowplow Use better consolidation of concrete around the steel armors. Leakage after installation Use high-solids urethane adhesive prior to insertion of the seal. Prevent twisting during installation. Dislodging over time Use better adhesive materials to anchor the seal to its place. Installing at low temperature. Loss of compression over time Use material with lower creep property. Size using a working range of 40% to 85% of its uncompressed width. Ozone sensitive Use material with high resistance property for ozone side effects. (continued)

440 DESiGN GUiDE FOR BRiDGES FOR SERviCE LiFE tAbLe 9.1. bridge jointS technoLogy tAbLeS (continued) Sliding Plate Joints Range of Movement: Less than 4 in. Expected Range of Service Life: Up to 30 years Service Life Problem Solution Advantages Disadvantages Corrosion of steel material used Determine selection of corrosion-resistant material (anchor). Comparable to armored butt joints, except that the sliding plate prevents, for the most part, the movement of debris below the joint. Movement of the sliding plate can easily be hindered by debris that accumulates in the slot.Bending and fatigue of the sliding plate Use thicker plates. Better design of surround material. Use high-tensile-strength steel. Drainage (clogging) Trough with steep slope. Conduct regular maintenance. Strip Seal Joints Range of Movement: Less than 5 in. Expected Range of Service Life: Up to 20 years Service Life Problem Solution Advantages Disadvantages Tearing of neoprene membranes Replace neoprene membrane. Good performance record. High degree of water tightness. If the membrane is set low, the debris can accumulate faster than it can be maintained. If it is set high, it will be prone to snow plow damage. High initial cost and replacement. Corrosion Determine selection of corrosion-resistant material (armoring). Debris accumulation Perform regular maintenance. Damage due to snowplow Set the neoprene membranes lower. (continued)

441 Chapter 9. ExpANSiON DEviCES tAbLe 9.1. bridge jointS technoLogy tAbLeS (continued) Finger-Plate Joints Range of Movement: More than 4 in. Expected Range of Service Life: 15 to 50 years Service Life Problem Solution Advantages Disadvantages Clogging of the joint Trough with steep slope. Suitable for large movements. Allows flushing of debris and prevents leakage and overflow. Good performance record. High initial cost and prone to snowplow damage if not designed correctly. Horizontal misalignment during construction can cause the fingers to jam. Vertical misalignment can result in poor ride quality and noise. Perform regular maintenance. Anchorage failure Construction QC. Design. Use stronger materials. Bent fingers (load related) Use thick plates. Use replaceable fingers. Misaligned fingers Ensure proper installation and avoid horizontal or vertical misalignments. Corrosion Design (corrosion-resistant material). (continued)

442 DESiGN GUiDE FOR BRiDGES FOR SERviCE LiFE tAbLe 9.1. bridge jointS technoLogy tAbLeS (continued) Modular Expansion Joints Range of Movement: Greater than 5 in. Expected Range of Service Life: 10 million cycles Service Life Problem Solution Advantages Disadvantages Fatigue cracking of welds High-purity materials, new fatigue design and details. Can accommodate very large movement. Incorporates many components and is high maintenance; therefore, many agencies are reverting to the use of finger-plate joints. Water leakage at seal splice Curbs to guide drainage away. Debris accumulation in seals Perform maintenance crew clean out once per year. Run joint through opening in parapet with a catch basin. Direct drainage away from joints in order to wash debris away. Reflective cracking in concrete above support box Use a thicker top plate to support box. Use an increased concrete cover over support box. Use a #3 reinforcing bar over anchorage detail to minimize cracks. Drainage build-up Curbs or upturns.

443 Chapter 9. ExpANSiON DEviCES 9.4.8 Strategy table for Expansion Joints Selecting the appropriate expansion device for the required movement range is the most critical step in enhancing the service the life of these joints. Table 9.2 summarizes the information presented in this chapter and proposes recommended strategies when expansion devices are to be used. The table is intended to serve as a guide to the de- signer in selecting bridge expansion devices.

444 DESiGN GUiDE FOR BRiDGES FOR SERviCE LiFE tA B LE 9 .2 . St rA te gy t Ab Le F or e xP An Si on j oi n tS M ax im u m Lo n g it u d in al M o ve m en ts (i n .) St ra te g y P o te n ti al D et er io ra ti o n M o d e O p ti o n s to Im p ro ve Se rv ic e Li fe Li fe -C yc le C o st D if fi cu lt y A ss o ci at ed w it h R ep la ce m en t P er fo rm an ce R ec o rd Ex p ec te d Se rv ic e Li fe (y ea rs ) In it ia l M ai n te n an ce Le ss t ha n 1 in . Fi el d- m ol de d or o th er eq ui va le nt jo in t ty pe s Se e Ta bl e 9. 1 Pr ov id e se co nd la ye r pr ot ec tio n Lo w H ig h Lo w G oo d 1 to 3 Be tw ee n 1 an d 4 in . C om pr es si on s ea l jo in t (3 in . m ax .) Se e Ta bl e 9. 1 Pr ov id e se co nd la ye r pr ot ec tio n M ed iu m H ig h H ig h Ve ry g oo d 3 to 3 0 St rip s ea l j oi nt s Se e Ta bl e 9. 1 Pr ov id e se co nd la ye r pr ot ec tio n M ed iu m H ig h H ig h Ve ry g oo d 3 to 3 0 La rg er t ha n 4 in . Fi ng er -p la te jo in ts Se e Ta bl e 9. 1 Se e Ta bl e 9. 1 H ig h H ig h H ig h Ve ry g oo d 10 t o 50 M od ul ar e xp an si on jo in ts Se e Ta bl e 9. 1 Se e Ta bl e 9. 1 Ve ry h ig h Ve ry h ig h Ve ry h ig h G oo d 10 t o 50