Serb Guardrail - South Ashland Interchange, California State Line Section...
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The Self Restoring Barrier (SERB) is a proprietary guardrail unit comprised of a single tubular thrie beam held outward from the supporting wooden posts by pivoting metal arms, its height above the ground secured by short cables attached to the top to the wooden posts. Two SERB guardrail systems were installed on the Pacific Highway (Interstate 5) in southern Oregon as part of an Experimental Features Project for the Oregon Department of Transportation (ODOT). The SERB guardrails were placed along the same alignment as the previous standard guardrail. The SERB guardrails were placed along the same alignment as the previous standard guardrail. The SERB guardrail is designed to redirect vehicles (including larger vehicles) when struck, yet require little or no maintenance after being struck by smaller vehicles. During the three years of in-service performance, the SERB guardrails had experienced some damage to the rail, and were not yet repaired. A problem with the lag screw that connects the support cable to the guardrail post has been found: the lag screw has been slipping from the weight of the thrie beam, allowing the guardrails to sag. However, the guardrails were still functional in 90% of the length of installation. The local maintenance district opted to remove the SERB in July of 1993. Reasons cited for renewal included, high cost, man-power, and traffic control in a dangerous work zone. This final report covers the three evaluation and removals of the SERB guardrails.
Microsilica Modified Concrete for Bridge Deck Overlays
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This final report presents information collected by ODOT personnel from bridge deck overlays constructed in Oregon between 1989 and 1995. Decks were placed on a variety of existing bridge types prepared using hydrodemolition, milling, and diamond grinding followed by sand, water or air blasting. Both latex and microsilica overlays were placed under a variety of environmental conditions. The study investigated causal relationships between construction and environmental factors and deck cracking and delamination and, where warranted, recommends procedures to minimize these distresses.
Statistical analyses of available environmental and construction information from several overlays constructed between 1989 and 1993 failed to clearly establish the cause(s) of delamination or cracking. Petrographic studies of cores taken from these decks appear to show increased microcracking in substrates prepared with milling compared to those prepared with hydrodemolition. Diamond ground substrates were not included in this phase of the study. This analyses supports increased use of hydrodemolition over milling.
In an effort to establish the casual relationships, detailed environmental and material property data were collected during construction on five bridges in 1995. Statistical analyses of data provides information on the range of environmental conditions under which bridge deck may be placed, however, little cracking or delamination was noted in any of the five bridges. Thus, the cause(s) were not identified.
Concrete Bridge Deck with Isotropic Reinforcing
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Isotropic reinforcing is the placement of reinforced steel uniformly both longitudinally and transversely on the bottom and top of the bridge deck. It is an alternate to deck reinforcing designs based on the traditional “Westergaard” distribution of bending moments. The Federal Highway Administration (FHWA) approved the use of isotropic reinforcement for this project.
Isotropic reinforcing was place in the USBR Canal Bridge deck (Klamath Falls) and is being evaluated as an Experimental Features project. The bridge deck was constructed in December 1992 in two separate stages. While there were a few problems with this project, none were related to the isotropic reinforced deck being constructed, and will not affect the performance of this deck over time. The bid to install this deck was based on a cost estimate of $12.36/S.R. ($133.05/m²).
Field Application of an Arc-Sprayed Titanium Anode for Cathodic Protection of Reinforcing Steel
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This study provided the first field trial of a catalyzed, arc-sprayed titanium anode for cathodic protection of steel reinforced concrete structures. Catalyzed titanium as an anode material offers the advantage of long life due to the inherent non-corrosive nature of the metal in atmospheric exposure. To continue to serve as an anode, the titanium will require a periodic and easily accomplished re-application of the catalyst rather than reapplication of the metal. The purpose of this study was to evaluate the installation and operation of the catalyzed titanium anode and to evaluate the economics of the titanium anode system compared to arc-sprayed zinc.
The initial phase of the study included modification of the spray equipment for spraying titanium wire and determination of the optimal spray parameters for applying the titanium anode to the bridge. Coating resistivity was found to be the best measure for evaluating the effectiveness of the coating. Decreasing spray distance, increasing current, and using nitrogen as the atomizing gas (propellant) all decrease coating resistivity. A multiple regression equation developed from the collected data showed that, for the data collected in this study, spray gun travel speed and atomizing gas pressure have an insignificant effect on coating resistivity
Coating analysis showed that the arc-sprayed titanium is a non-homogeneous coating due to reactions with atmospheric gases. The coating contains, on average, 88 weight percent titanium. The principal coating constituents are a-Ti containing interstitial nitrogen, interstitial oxygen, and y-Ti0 with the possibility of some TIN. The coating consists of alternating layers of a-Ti rich and y-Ti0 rich material. The use of nitrogen as the atomizing gas results in a coating with less cracking, more uniform chemistry, and therefore, lowers coating resistivity than is produced using air atomization.
The field trial resulted in installation of 280 m2 (3015 ft2) of catalyzed, arc-sprayed titanium on the Depoe Bay Bridge. Several lessons were learned during the field trial. Although use of a grade 1, annealed titanium wire for spraying was found to reduce equipment wear, frequent equipment maintenance caused by rapid wear of the copper spray tips had a significant impact on operator productivity. The switch-mode power supply furnished with the spray equipment was unable to provide the stable arc needed for smooth operation of the spray equipment. Current distribution plates embedded flush in a concrete patch material proved to be the best method for providing a low resistance connection between the anode and the power supply.
Although some difficulty was experienced during the field trial, the costs for performing this work exceeded the bid costs for installing arc-sprayed zinc on this same structure by just 18 percent. If the long-term performance of the catalyzed titanium anode system is proven, the arc-sprayed titanium system will provide a life cycle cost advantage over the arc-sprayed zinc system.
Armorform Articulating Block Mat Erosion Control System
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ARMORFORMÂ® Articulating Block Mat (ABM) was used as part of a bridge replacement project at the Salmon Creek Bridge abutments in the summer of 1991. ABM was selected to replace riprap which was continually being undermined by the erosion of the streambed. ABM was selected due to its ability to maintain its structure (articulate) and withstand erosion. The original design requiring the mat to be keyed into the bank could not be constructed according to the manufacturer due to product limitations. Therefore, contrary to the original design, the flanks of the mat were not embedded into the bank to protect against undermining from bank erosion.
The ABM did work well during the flood event in February of 1996. Although the northwest corner was undermined, the blockmat articulated and changed slope to partially fit the void. Because the bank erosion stopped near the edge, it appears that the ABM also retards embankment erosion. However, the gap was not filled completely which allowed the rushing water to flank the mat increasing the damage. Downstream, some of the blocks were torn away from the mat while others were uncovered in the toe trench. Since the riprap placed by maintenance to retard the erosion is end dumped rather than keyed into the channel bottom and bank, the stream will probably continue to flank the ABM.
Future designs subject to similar flow conditions should consider keying the upstream edge 10 ft (3 m) into the bank and burying the toe 8 ft (2.4 m) into the channel bottom. In addition, the design should include riprap to protect the flanks of the mat. The ideal situation would be to construct the mat as designed with the fan shaped ends. The ABM appears to be most suited for active streambeds susceptible to erosions with slopes steeper than 1.5H:1V (steeper than is reasonable to place riprap).
Future designs should also consider the configuration of the ABM blocks. Consideration should be given to configuring the blocks so that there is no vertical alignment offset versus staggering the blocks. Aligned rows of blocks would allow articulation in all directions.
Least Cost Transportation Planning in ODOT
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This project is intended to suggest ways in which least-cost planning principles could be incorporated into the transpiration planning process. The Mt. Hood corridor was chosen for examination. The examination of the planning process highlighted several differences between a least-cost planning approach and the present process. First, the corridor chosen is designated as an Access Oregon Highway, and this designation sets certain level of several standards that do not appear to be consistent with a least-cost planning process. Second, the analysis of future outcomes was not as detailed as might be required for a least cost planning process. Third, the process was more deterministic than would be expected with least cost planning, since the latter emphasizes uncertainty in forecasts and the need for flexibility. Fourth, the range of alternatives considered appeared to be more narrowly defined than one would find with least cost planning, and fifth, the analysis of travel patterns and possible diversion to other routes was not extensive as might be done for least cost planning. Many of these constraints were due to specific requirements of the planning process or of the environmental process. Various approaches to evaluating alternatives for the Mt. Hood corridor are detailed and discussed. The types of data needed and the the likely cost of the analysis are specified for different approaches. These include cost-benefit analysis, cost-effectiveness or problem-oriented analysis, and estimation of decision-maker preferences. It is concluded that the general concept of Least-Cost Planning is readily adaptable to transportation planning; however, the specific methodolgy is still not well-defined and there are substantial knowledge gaps regarding the effect of various policies. In particular, there is little information on the effectiveness of various non-construction alternatives in responding to increases in demand for transportation services. It appears to be both feasible and desirable to move in the direction that has been identified as "Least-Cost Planning, characterized as a planning process that seeds to improve the efficiency of the transportation system, primarily by considering alternatives to new construction as methods to provide transpiration services. Demand management systems, pricing systems, and land use systems are among the options that should be evaluated along with rod construction, transit construction, and other supply oriented management systems.
Evaluation of Raised and Recessed Pavement Markers
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Oregon has been using recessed markers for approximately 10 years on all types of roads, west of the Cascade mountains,. The recessed markers are protected from snow plowing operation and may last longer that raised markers, however, their life expectancy of effectiveness has never been evaluated. Standing water and/or debris has been observed in the recessed grooves which reduces the reflectivity of the markers. In addition, the effect of studded tire wear, abrasion from sanding materials, and traffic on markers has never been fully evaluated. Paint striping and raised markers are still good alternatives for marking state highways. Paint has a minimal life cycle cost with minimal traffic impacts during replacement. Skip lines enhanced by raised markers provide excellent lane delineation both visually and audibly. However, the reflectivity of the markers may drop much as 70% in the first year. Because to costs of raised markers are around $250 more per year per mile than paint, they should only be used when it is cost effective or when needed to improve traffic safety. Skip lines enhanced by recessed markers cost approximately $100 per mile more that skip lines enchanted by raised markers. This cost is based on a three-year life for recessed markers, 12-year analysis period and a discount rate of 4%. Recessed markers also do not perform as well as raised markers. The initial performance is reduced strictly because they are recessed. The slots collect debris, rain and snow and when covered are ineffective. Indication are that a maintenance program to remove the debris would not the viable. We recommend That:
1) Because of the expense and poor performance, recessed markers should not be used by ODOT
Paint striping and raised markers are the best alternative for marking our state highways.
Consideration should be given to the selection of marker of paint based on ADT and
2) Durable marker should be considered for special applications
Geotextile Reinforced Bridge Approach Embankment
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An experimental construction method was evaluated at the Lost River Bridge in Klamath County to reduce the discontinuity between the bridge and the roadway. The method included combining soil in six 300 mm lifts interlaced with geotextile reinforcement. The original plan was to replace the bridge and construct a wider bridge at the site. The final plan included building only sliver fills with no control sections (i.e., no non-reinforced embankments).
The site was surveyed after construction to determine any settlement of the foundation or fill material. One year after construction, no settlement was measured. Due to a lack of a control section, no conclusions or recommendations for this type of construction method can be made.
Latex Modified Fiber Reinforced Concrete Bridge Deck Overlay
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In an attempt to increase the tensile strength of LMC and reduce cracking, steel fibers were added to a LMC mix. The results are what is termed as "latex- modified, fiber-reinforced concrete" (LMFRC). LMFRC was placed on Hayden Bridge as an experimental overlay.
The LMFRC overlay has performed well and has not yet developed any visible cracks. The overlay has not delaminated or rutted. The skid resistance is comparable to a standard PCC deck.
Recommendations for improved construction practices can be found in the Construction1 Interim Report that was prepared in June 1993. Finally, because of its improved Performance, a LMFRC overlay may be considered as a permitted alternative to LMC.
Overlay Design for Unstable Asphalt Mixes
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The first objective of this study was to evaluate the relative rutting characteristics of overlaid pavements, where the overlaid section (i.e., new "base") had previously exhibited rutting. A second study objective was to develop criteria for the design of overlays for unstable "bases." The mixtures were evaluated in an LCPC Wheel Tracker. Slabs of the dense graded "base" mixtures and a typical open graded overlay mixture were evaluated by themselves as well as in three alternative configurations of composite layered slabs to simulate an overlaid pavement. A Repeated Load Creep Test was also conducted on cylindrical specimens of the base and overlay mixtures. The use of the wheel tracking device did not provide a satisfactory means of evaluating either the open-graded overlay mixture or the composite slabs. This was predominantly because of the need to confine the open-graded mixture in the test "mold." This could be achieved in the future by preparing the specimens in the molds, an option not available to the researchers for this study. Tentative criteria for overlaying rutted pavements were developed. It is proposed that the Repeated Load Creep Test be conducted at 25° C for both base and overlay mixtures. After 2000 load repetitions, if the permanent strain for either mix exceeds 1 percent (10,000 microstrain), the overlay of this base should not be pursued. If the mixes pass the creep criterion, they should be tested at 60° C in a layered slab configuration in the Wheel Tracker and if the rutting is less than 10 mm after 50,000 passes, the field overlay project should proceed. If the rutting is more than 10 mm after 10,000 passes, the project should not proceed. If the rutting falls between these two limits, an overlay could proceed with an adjusted mix design or if the truck traffic for the project is light.
Evaluation of Rutting Potential of Oregon Surface Mixes
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The purpose of this study was to evaluate the rutting potential of selected asphalt concrete mixes used in Oregon. Dense and open-graded, as well as large stone, mixes were considered. The experimental design included one asphalt cement, two aggregates, and nine different combinations of mix type and lift thickness. Specimens were fabricated in the lab by means of rolling wheel compaction and then evaluated by two methods: the LCPC (Laboratories Central des Ponts et Chaussees) wheel tracking device and the simple shear device developed as part of the Strategic Highway Research Program (SHRP). With the wheel tracking device, rutting potential was characterized in terms of rut depth and rutting potential; with the simple shear devices did discriminate among the various mix types. Based on these limited data, the relative ranking of mixes with respect to rutting potential is A > B > C > F(best to worst) in the simple shear device and B = C > A. > F in the LCPC rut tester. The limited laboratory testing of the F-mixes (open-graded) suggests that it might be prone to rutting which is contradictory to its observed performance in the field. Also, the layered F-mixes performed better than did the F-mix alone. Additional testing with increased confinement, in both the wheel tracking and shear devices, is clearly warranted. Finally, additional laboratory test data would permit the performance criteria for the Oregon mixes in terms of both test devices.
Rubber Modified Asphalt Concrete (METRO RUMAC) Evaluation
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This report covers the construction in 1992 of test sections on two projects using asphalt concrete modified with tire rubber. One project's test sections are part of a single lift overlay on a lightly traveled two-lane road south of Klamath Falls, Oregon. The other project's test sections are part of the base course of a three-lift overlay on a heavily traveled four-lane divided highway between Eugene and Springfield.
All test sections use a dense-graded rubber modified asphalt concrete developed for the METRO agency of the Portland, Oregon urban area (METRO RUMAC). Control sections were paved with conventional asphalt concrete adjacent to the test sections. The test sections are compared to these control sections.
The METRO RUMAC was successfully blended for both projects by adding unopened bags of the rubber to the pugmill of the mix supplier's batch plants. The rubberized mixes could be placed and compacted by conventional equipment. One project's test sections could not be rolled to the desired density. An improper mix gradation may have prevented compaction. The other project's test sections could be compacted to the desired density. Immediately after compaction, construction traffic traveled on one project's hot METRO RUMAC pavement, and the vehicle's tires adhered to and damaged the surface.
Experience on these projects indicate that the specification limits for crumb rubber need to be revised, and in some cases, the percentage of rubber required in the METRO RUMAC needs to be lowered to obtain satisfactory mix properties. In addition, solvent extractions were successfully used on one project to determine the overall gradation of the METRO RUMAC.
Sampling and testing methods were developed to see if the crumb rubber added to these pavements met the MEIT0 RUMAC specifications.
After construction, both project's METRO RUMAC and conventional pavement sections had similar appearances and surface friction values. On one project, the test and control section's ride quality was compared, and the METRO RUMAC and conventional mixes had similar characteristics.
The METRO RUMAC mixes cost 1.3 to 2.0 times as much as their conventional counterparts. Much of this cost was due to the addition of the rubber, and the extra asphalt required by the rubberized mixes.
Polypropylene Fiber Reinforced Concrete Detention Ponds
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In 1991, two Durafiber polypropylene fiber reinforced concrete lined detention ponds were constructed. The detention ponds are located on the north side of the 181st Avenue Interchange, on the Columbia River Highway (I-84), approximately ten miles east of Portland, Oregon.
The original design called for the detention ponds to be constructed with six-inch thick welded wire fabric reinforced concrete over an impermeable geo-membrane. An alternate to this design, replacing the welded-wire fabric reinforced concrete with polypropylene fiber reinforced concrete, was proposed by the contractor through a no cost price agreement and approved by the Oregon Department of Transportation (ODOT) and Federal Highway Administration (FHWA). The replacement of welded-wire fabric reinforced concrete with polypropylene fiber reinforced concrete created no problems with respect to mixing, placing, workability, finish-ability, or visual appearance. The use of fiber reinforced concrete on this project resulted in a small cost reduction relative to the use of welded wire fabric reinforced concrete. However, as a result of the field observations made during the final site visit, it was concluded that the reinforcing fibers appeared to have provided no added value toward strengthening the ponds shot-creted layers; although, the ponds are performing satisfactorily.
ODOT Research Unit Staff should do the following:
- If funds are available, the fiber reinforced concrete should continue to be monitored until it fails.
- If polypropylene fiber reinforced concrete is used on another ODOT project, it should be evaluated.
Repair of Rutting Caused by Studded Tires
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Rutting caused by studded tire wear has become a major issue in Oregon because of the impact on the infrastructure and the increase in driving hazards. It is estimated that the cost to mitigate the damage from studded tire use in 1993 alone is $42 million state-wide. The ruts caused by the studs lead to reduced pavement life which increases the life cycle costs. The safety hazards include an increase in splash and spray and hydroplaning during rainy weather.
Polymer Concrete Bridge Deck Overlays
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This report documents the construction and performance of two thin polymer concrete (with polyester/styrene resins) bridge deck overlays. The overlays were constructed in Biggs and Maupin, Oregon in June 1993. Several problems were encountered during construction that resulted in bare spots and/or a rough riding surface. The bare spots could be attributed to the polymer concrete curing before aggregate placement. Maintaining a uniform grade and providing a smooth riding surface was difficult because of bare spot repair, cold joints, and joint repair. More than 900 sq. ft of delamination was noted at the Deschutes river Bridge within six months following construction; 4,500 sq. ft. was noted after 1 1/2 years. More than 2,200 sq. ft. of delamination was noted at the Maupin Bridge after six months; 6.600 sq. ft. was noted after 1 1/2 years. The polymer concrete has broken loose and is easily removed in blocks. Both overlays are scheduled for removal in the fall of 1995. We recommend that controlled field tests of polymer concrete (with polyester/styrene resins) be required before these products are used extensively by ODOT. When the next polymer concrete overlay is constructed the following recommendations should be followed to aid proper placement: a) Drains shall be temporarily covered to keep the slurry mix out.
b) All decks striping shall be removed prior to overlay construction.
c) The contractor shall be required to maintain a continuous delivery of materials to the bridge deck
during overlay construction. The amount of material available for application should be evenly
matched with the number of construction workers.
d) Joint repair shall include the removal of material 12 to 18 inches on each side of the joint. Heave
shot blasting or 1/4 inch diamond grinding shall be used for concrete removal around the joints. The
material used to fill the joint shall be feathered in to provide a smooth riding surface.
e) Workers shall not be allowed to walk on the fresh overlay to broadcast the aggregate.
f) The aggregate shall be broadcast from a distance to provide uniform coverage and allow the wind to
remove finer particles.
g) The overlay shall be feathered to zero inches at the drains to reduce the possibilities of standing
water at the curb line.
h) Final raking shall be in the direction of traffic .
i) If edge tape (duct tape) is used, it shall be removed as soon as possible ( if the mix sets up, edge
tape removal may cause delimitation).
j) Gauge rakes shall be checked and hooks replaced frequently to maintain the specified minimum
thickness of overlay.
Soil Nailing of a Bridge Embankment Report 2: Design and Field Performance Report
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Soil nailing has recently been introduced in Oregon as an alternative lateral earth support method. The first permanent soil nail wall on the state's highway system was used where an underpass was widened under the existing Oregon Slough Bridge in Portland, Oregon to provide for additional traveling lanes. The project required removal of the existing south end slope and the construction of a soil nail wall in front of the pile-supported end bent to permanently retain the existing bridge fill embankment. Construction and post-construction monitoring was performed to study the new wall's performance.
This report describes the design and the performance of the Interstate-5 soil nail wall. The instrumentation program implemented during the construction of the wall is discussed in detail. The instrumentation data at two vertical cross sections is presented and data interpretation is discussed. The performance predicted by the original design methodology is compared critically to the measured.
Based on the results of our study, it may be concluded that:
- the Interstate-5 Swift-Delta soil nail wall is performing well within structural safety limits for both the wall and the bridge abutment,
- tensile forces are maximum inside the soil nailed earth mass at some distance from the facing,
- a relative movement in the range of 118 to 114 inch (3.1 8 MM to 6.34 MM)is necessary to mobilize the tensile capacity of the soil nails,
- the Davis method overestimates the nail forces in the lower nails and underestimates the nail forces in the upper nails, and
- Terzaghi and Peck's braced cut empirical earth pressure diagram appears to be in reasonable agreement with measured loads to date.
Crumb Rubber Modified Asphalt Concrete in Oregon
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Since 1993, the Oregon Department of Transportation (ODOT) has been monitoring performance of seventeen rubber modified asphalt and asphalt concrete sections constructed on Oregon highways. he study originated in response to the Intermodal Surface Transportation Efficiency Act (ISTEA, 1991) which mandated the use of tire rubber in pavements. The ISTEA requirement was eventually repealed, however, the study continued to document pavement performance in an effort to determine if rubber modified asphalt concrete pavements are feasible in terms of construction and life cycle cost. The rubber modified sections that performed the worst included those constructed using the dry process (rubber modified asphalt concrete—RUMAC). The sections performing the best included open graded mixes constructed using the binder PBA-6GR (a rubber modified asphalt). fter five years, the PBA-6GR pavements were performing as well or better than the control sections. he cost of the mixes constructed in 1993 and 1994 with PBA-6GR was about 12% more than the control sections. Over the life of the pavement, the terminal blend asphalt rubber (PBA-6GR) may be cost effective. This report documents the performance of the rubber modified and control sections including distress information, skid and ride data and laboratory testing results. In addition, non-ODOT projects were reviewed and discussed.
Long Continuous Bridge Deck Evaluation John Day River Bridge Clatsop County
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The John Day River Bridge, near Astoria, Oregon was built with a continuous deck length of 1,105 ft. (340 m). The rationale for designing the John Day River Bridge with an unusually long continuous deck is in part based on the site's very mild climate. Overall temperature changes in the deck are in the range of 50'F (28-C). The objective was to monitor and evaluate the impacts which may result from expansion, contraction, or shrinkage of the bridge deck. This bridge has shown no significant signs of distress which may be related to expansion/contraction of the bridge deck. Deck measurements show that the bridge has not expanded or contracted more the anticipated amount.
In the future, if the long continuous bridge deck design is considered, recommendations include:
- locating the bridge on stable fill,
- providing for controlled cracking, and
- providing for expansion, contraction or shrinkage between the bridge ends and the impact panels.