Abstract:
The SR99-Spokane Street Over-crossing is located in Seattle, Washington, and was built in the late 1950s. Its construction is mostly of reinforced concrete; the reinforcement detailing is poor by modern seismic standards, particularly with respect to confinement, and the underlying soils are also weak. Furthermore, the structure contains many "outrigger bents", in which columns are displaced from their ideal locations to accommodate passage of railroad tracks beneath the structure. These outrigger bents cause significant asymmetry in the structure that could lead to unusual and undesirable seismic response. In this study, the seismic response of the structure was evaluated analytically and seismic retrofit strategies were developed and evaluated. In a companion experimental study by Washington State University (WSU), the as-existing structure was investigated by testing scale models of representative bents, and one retrofit strategy was also tested. In this report, modeling approaches are discussed in detail, and the results of evaluations of the as-existing structure as well as the retrofit strategies are presented. Some components of the structure (e.g. the deck, the already-jacketed columns and the soil-foundation-structure system) were found to be critical to an accurate determination of response and were therefore modeled in some detail. Site-specific ground motions at three different hazard levels were used. The structure was found to be vulnerable, especially to the 72- and 475-year ground motions. The knee-joints that connect the outrigger beams and columns were found to be the most critical components, and their vulnerability was shown to be influenced by the type of retrofit performed on the outrigger column. Retrofit strategies included some designed to increase the strength and ductility of the components, and some intended to reduce the demands on them.

Authors:
Inouye,B., Lehman,D. E., Stanton,J. F., Kramer,S. L.

Keywords:
columns, concrete, construction, ductility, evaluation, experimental, hazard, ITS, knee-joints, modeling, models, outriggers, reinforced concrete, reinforcement, retrofit, seattle, seismic, seismic response, soil-structure interaction, strength, Washington, Washington state

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External Links: http://www.wsdot.wa.gov/research/reports/fullreports/596.1.pdf http://wsdot.wa.gov/Research/Reports/500/596.1.htm

Abstract:
This study investigated retrofitting measures for improving the seismic performance of existing multi-column bridge bents. Experimental tests were conducted on 1/4.5-scale footing and column assemblages which incorporated details that were selected to represent deficiencies present in older bridges. Various retrofit measures for the bents were evaluated. The specimens were subjected to increasing levels of cycled inelastic lateral displacements under constant axial load. Specimen performance was evaluated on the basis of load capacity, displacement ductility, strength degradation and hysteretic behavior.Tests on the as-built specimens resulted in severe cracking in the footings due to insufficient joint shear strength in the column/footing connections. However, due to structural redundancy, the bents continued to resist lateral loads until eventual bent failure occurred as a result of flexural hinge degradation in the columns.Measures developed previously for retrofitting single-column bent bridges were found to be effective in improving the performance of the footings and columns. When all substructure elements were retrofitted, a ductile bent response was obtained. Retrofitting only some of the substructure elements resulted in incremental improvements in performance according to the number of elements retrofitted. While extensive damage occurred in the unretrofitted elements, the damaged regions continued to transfer forces during testing, enabling a stable bent response until failure occurred within one or more of the retrofitted elements.The addition of a stiff link beam just above the footings was found to be effective in preventing damage in the footings during testing, and a reasonably ductile bent response was achieved. Because the link beam retrofit may not require retrofitting of the footings, this strategy may be a very cost-effective approach for retrofitting multi-column bents.

Authors:
McLean,D. I., Kuebler,S. E., Mealy,T. E.

Keywords:
seismic retrofitting, reinforced concrete, bridge, substructures, multi-columns bents, research

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Abstract:
Lap splices in reinforced concrete members typically consist of bars overlapped and placed in contact with each other. In the case of a large-diameter foundation shaft connecting to a smaller-diameter column, it is not possible to have the longitudinal bars be continuous, nor is it possible to provide a standard lap splice; instead an offset or noncontact lap splice of the longitudinal bars is required. With a noncontact lap splice, transfer of forces from one spliced bar to the other occurs through the surrounding concrete, and transverse reinforcement is typically required to provide satisfactory splice performance. Current code provisions on noncontact lap splices are very limited.This study experimentally investigated the behavior of noncontact lap splices in bridge column-shaft connections. Tests were performed on near full-scale panel specimens, representing a cross-section of a column-shaft connection, and on 1/4 scale column-shaft specimens under both monotonic and cyclic loading. Variables investigated included lap splice length, lapped bar spacing, and spacing of transverse reinforcement. Specimen performance was evaluated in terms of load capacity, failure mechanism, and strength degradation.Two-dimensional and three-dimensional truss models were developed to predict, the behavior of noncontact lap splices. Experimental results supported the proposed behavioral models. Inclined cracks developed in the concrete which defined compression struts running between the offset lapped bars. Transverse reinforcement was required to provide equilibrium to the struts. Tests on specimens detailed based on the proposed models resulted in no strength degradation or slippage of the lapped reinforcing bars even when subjected to cyclic loading. Equations were proposed for the design of noncontact lap splices, including recommendations for required overall lap length and transverse reinforcement.

Authors:
McLean,D. I., Smith,C. L.

Keywords:
reinforced concrete, bridge, reinforcing splices, columns, foundation shafts, research

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Abstract:
This study investigated retrofitting measures for improving the seismic performance of the substructures of existing bridges. Retrofit measures for both pile-supportes and spread footings were investigated. Experimental tests were conducted on 1/3-scale footing and column assemblages which incorporated details that were selected to represent deficiencies present in older bridges. Retrofit measures were applied to both the columns and footings. The speciments were subjected to increasing levels of cycled inelastic lateral displacements under constant axial load. Specimen performance was evaluated on the basis of load capacity, displacement ductility, strength degradation and hysteretic behavior.Tests on the as-built speciment resulted in a brittle failure due to insufficient joint shear strength in the column/footing connection. An added reinforced concrete overlay provided an effective retrofit for the as-built footings. The overlay resulted in increased shear resistance, allowed for the addition of a top mat of reinforcement to provide negative moment strength, and increased the positive moment capacity by increasing the effectve depth of the pile cap. All retrofitted specimens developed plastic hinging in the columns with a resulting ductile response under the simulated seismic loading. Special detailing was required in the column lap splice regions in order to maintain the integrity of the splices. In specimens that were overturning critical, increased overturning resistance was provided by enlarging the footing plan size, by providing additional piles, or by providing tie-downs through the footing.

Authors:
McLean,D. I., Saunders,T. D., Hahnenkratt,H. H.

Keywords:
seismic retrofitting, reinforced concrete, bridge, substructures, research

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Abstract:
An engineering team from the University of Washington (UW) evaluated the seismic vulnerability of the Alaskan Way Viaduct, located in Seattle, Washington. This report presents the evaluation of a typical three-bay unit that was designed by The City of Seattle Engineering Department (SED). The evaluation team performed response-spectrum analyses and nonlinear analyses for the fixed-base condition. The team considered a widely used soft-soil spectrum and worst-case, site-specific spectra. Wherever possible, the UW team evaluated the vulnerability for each failure mode following procedures proposed; by the Applied Technology Council; and by researchers at the University of California, San Diego.The evaluation team found that the vulnerability of the Alaskan Way Viaduct exceeds that of bridges built to current standards. The vulnerability is a result of a combination of two factors: (1) the design ground motion would strongly excite the viaduct; and (2) many of the structural components lack the ductility required by current standards. The following deficiencies were identified as the most critical.*The lower-story columns have inadequate transverse reinforcement, and could fail in shear before they develop their flexural capacity.*The first- and second-story joints have inadequate confinement reinforcement, and during strong ground motions, they could experience a diagonal-tension failure.*If the base of the lower-story columns develop their flexural capacity, the footings could fail in shear.

Authors:
Knaebel,P., Eberhard,M. O., de la Colina,J.

Keywords:
bridge, earthquake, evaluation, reinforced concrete

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Abstract:
An engineering team from the University of Washington (UW) evaluated the seismic vulnerability of the Alaskan Way Viaduct, located in Seattle, Washington. This report presents the evaluation of a typical three-bay unit that was designed by WSDOT. The evaluation team performed response-spectrum analyses and nonlinear analyses for both fixed-base and pinned-base conditions. The team considered a widely used soft-soil spectrum and worst-case, site-specific spectra. Wherever possible, the UW team evaluated the vulnerability to each failure node following two or three procedures, including those proposed by the Applied Technology Council (1983) and Priestley, Seible, and Chai (1992).The evaluation team found that the vulnerability of the Alaskan Way Viaduct exceeds that of bridges built to current standards. The vulnerability is a result of a combination of two factors: (1) the ground motion is likely to strongly excite the viaduct; and (2) many of the WSDOT unit's structural components are likely to behave in a brittle manner. The following deficiencies were identified as the most critical.*The first-story column-reinforcement splices are too short, they have too little confinement reinforcement, and they are located in regions likely to experience large ductility demands.*The column/beam joints have inadequate confinement reinforcement, and during strong ground motions, they could experience a diagonal tension failure.*The shear strength of the first-story columns is marginal.*If the first-story columns develop their flexural capacity during an earthquake, the pile-supported footings could fail in shear.

Authors:
Eberhard,M. O., de la Colina,J., Ryter,S.

Keywords:
bridge, earthquake, evaluation, reinforced concrete

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Abstract:
This study was part of a Washington State Department of Transportation (WSDOT) program to assess the vulnerability of multiple-span highway bridges built before 1984. During the first series of static tests (Phase I), discussed in a previous report, a three-span, reinforced concrete bridge was subjected to large lateral loads. In Phase II, described in this report, the researchers greatly reduced the resistance that the abutments provided so that they could evaluate the lateral-load resistance of the piers. The researchers then subjected the piers to large, transverse cyclic displacements with drift ratios of 0.5, 1.0, 2.0, and 3.0 percent.The piers resisted repeated loadings to a force equal to one third of the bridge's weight. The envelope to the pier's hysteretic response indicated that the system yielded at a drift ratio of 0.7 percent. Whereas the top of the columns spalled at large drift ratios, the damage to the bottom of the columns was limited to flexural cracks. The pier's measured response was compared to that calculated by the researchers, the California Department of Transportation, and the WSDOT. The calculated responses were found to be strongly sensitive to the assumed steel and soil properties. On the basis of the experience gained in performing the tests, the researchers made recommendations for those planning to perform future tests of large structures. In -addition, while acknowledging the limitations of a single series of static tests, the researchers concluded that (1) the tests should serve as a benchmark against which to evaluate proposed analytical models, (2) at an effective acceleration of 0.2g, the seismic damage to the isolated bridge would probably be minor, (3) at an effective acceleration of 0.4g, the piers would likely sustain heavy damage, and (4) the WSDOT should investigate the influence of soil properties on column damage to determine when geotechnical tests are warranted.

Authors:
O'Donovan,T., Eberhard,M. O., MacLardy,J. A., Marsh,M. L.

Keywords:
bridge, earthquake, piers, reinforced concrete, tests, modeling, lateral loads

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Abstract:
Transverse reinforcement in bridge columns normally consists of spiral reinforcement in columns with circular cross-sections and tied reinforcement in columns with square or rectangular cross-sections. The circular shape of spiral reinforcement in inherently efficient in providing confinement to the concrete core and restraint of longitudinal bar buckling. In contrast, rectangular columns require cross-ties and/or overlapping ties in addition to the perimeter tie in order to provide adequate confinement and restraint of bar buckling. As an alternative reinforcing scheme, interlocking spiral reinforcement has been used in California for columns with rectangular cross-sections. However, several important design elements are not addressed in th Caltrans specification, and the performance of columns with interlocking spirals has not been fully established.This study experimentally investigated the seismic behavior of columns incorporating interlocking spirals under flexural, shear and torsional loadings. The main tests were performed on approximately 1/5-scale column speciments subjected to incraeasing levels of cycled inelastic displacements under constant axial load. Rectangular and oval cross-sections with either two interlocking spirals or conventional ties were investigated. Variables studies included the performance of interlocking spirals compared to ties, the amount of spiral overlap, an the size of longitudinal bars required in the overlap region to maintain spiral interlock.Columns with interlocking spirals performed as well or better than columns with ties, despite approximately 50% more transverse reinforcement being provided in the tied columns. Test results indicated improved performance when the center-to-center spacing of interlocking spirals was not greater than 0.6 times the spiral diameter. At least four longitudinal bars of approximately the same size as the main longitudinal reinforcement are required in the overlap regioin to maintain spiral interlock. Procedures were developed for predicting the axial, shear, flexural and torsional strengths of columns with the interlocking spirals.

Authors:
McLean,D. I., Buckingham,G. C.

Keywords:
seismic design, bridge, columns, reinforced concrete, transverse reinforcement

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Abstract:
This study was part of a Washington State Department of Transportation (WSDOT) program to assess the vulnerability of highway bridges built before 1984. Researchers applied slowly-varying transverse loads to a three-span, reinforced concrete bridge, including the superstructure, piers, and abutments. The purpose of the test was to measure the transverse stiffness of the bridge and to estimate each support's contribution to stiffness. The researchers also evaluated analytical models by comparing the calculated and observed responses. The bridge was extremely stiff and strong. In two cycles to a load equal to 45 percent of the bridge's weight, the maximum bridge displacement was 0.15 inch. During these cycles damage was minimal. At a load equal to 65 percent of the bridge's weight, the pier displacement was 0.30 inch. After the bridge had been excavated, the stiffness decreased to 15 percent of its original stiffness. The stiffness further decreased to 8 percent of the initial stiffness after the superstructure had been isolated from the abutments. The University of Washington (UW), California Department of Transportation (CALTRANS) and WSDOT models underestimated the stiffness of the bridge in its initial state. The UW model probably overestimated the resistance of the polystyrene at the abutments and underestimated the stiffness of the soil at the wingwalls. The CALTRANS model was too flexible because it neglected the resistance of the bearing pads and polysterene, and underestimated the soil stiffness. The researchers concluded that (1) the test can serve as a valuable benchmark against which to evaluate proposed seismic-evaluation procedures and models, (2) bridges that are similar to the test bridge are not highly vulnerable to transverse motions, (3) complex soil modeling is not justified if soil test data are not available, and (4) nonlinear analysis was necessary to reproduce the details of the observed response.

Authors:
Eberhard,M. O., MacLardy,J. A., Marsh,M. L., Hjartarson,G.

Keywords:
bridge and construction, bridge, earthquake, reinforced concrete, tests, modeling, lateral loads

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Abstract:
This study investigated retrofitting measures applied to 2/5 scale shear deficient columns representative of rectangular bridge columns in the Puget Sound area of Washington state. The retrofit methods studied included external hoops applied over the height of the column and full-height rectangular steel jacketing. Test specimens consisted of a single column connected at the base to a rectangular footing. The specimens were subjected to increasing levels of cycled inelastic displacements under constant axial load. The performance of the specimens was evaluated in terms of load capacity and ductility. Tests on the as-built column resulted in a brittle shear failure at the calculated yield displacement, i.e., at a displacement ductility level of u = 1. Both retrofit methods improved the behavior of the deficient column. With the external hoop retrofit, performance of the retrofitted columns was only moderately improved over that of the as-built column. Brittle fracture of the retrofit hoops limited the load carrying capability and ductility enhancement, and displaced ductility level of u = 2 and 4 were achieved. With rectangular steel jacket retrofit, performance was significantly improved over that of the as-built column. The jacket retrofit resulted in a ductile column response with good load carrying capability through u=8. When this retrofit was applied over the full height of the column, the steel jacket increased the column shear strength enough that flexural failure resulted. Although buckling of the steel jacket and longitudinal reinforcement occurred near the maximum moment section, sufficient confinement to the hinging region was provided by the buckled steel jacket to maintain load-carrying capability.

Authors:
McLean,D. I., Bernards,L. L.

Keywords:
structures, seismic, bridge columns, seismic retrofitting, reinforced concrete, shear failures

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Abstract:
The University of Washington (UW) team reviewed the Washington State Department of Transportation (WSDOT) report titled 'Earthquake Analyses of the Alaskan Way Viaduct' and performed an independent assessment of two typical sections of the structure. Additional analyses were performed to investigate the influence of some factors that were not considered in the WSDOT report. The input motion and geotechnical characteristics assumed in the WSDOT report were consistent with the information available to the WSDOT and the UW. However, the paucity of information available regarding the seismological risk and the subsoil conditions precluded the possibility of reliability estimating the input motion, foundations stiffness, foundation capacities, and potential for liquefaction. Inspection of the structural plans suggested that timber-concrete spliced piles in the section of the structure built by WSDOT might be particularly vulnerable. The elastic dynamic models generated by WSDOT and those constructed for this study were found to give comparable natural periods in the first three modes. Those in the higher modes differed because of the disparate ways in which the structures were modeled. However, the higher modes provided only a small portion of the total response, so the differences in calculated response were small. For the WSDOT designed part of the structure, g-ratings and dynamic code ratios were established by assuming that the reinforcement would reach its yield strength. The present study found the structure to be generally weaker than did the WSDOT study. Some of the ratings showed a consistent relationship with those given by the WSDOT study, while others showed considerable scatter. Regardless of the resolution of the discrepancies, both analyses indicated that the demands on structural members would be likely to greatly exceed their capacities. The main shortcomings in the structure appeared to be inadequate confinement steel and development lengths that were too short. Because no distress was observed after the 1965 Seattle earthquake, these calculations are undoubtedly conservative. However, the response of those brittle details cannot be predicted reliably without further investigation. The University of Washington team is proposing further study to verify seismic safety of the structure.

Authors:
Brown,C., Eberhard,M. O., Kramer,S. L., Roeder,C. W., Stanton,J. F.

Keywords:
bridge, reinforced concrete, earthquake, foundation

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Abstract:
The seismic performances of three retrofitted and one control, half scale, circular, reinforced concrete columns were studied. The columns were 10ft. high and 18 in. diameter cantilevers. The longitudinal flexural steel was spliced to the foundation dowels just above the fixed base. A concentric axial load of 20 fc Ag was continually applied during testing. The free ends of the cantilevers were translated to produce a maximum displacement of four times than necessary to produce yield in the longitudinal reinforcing steel. This loading was repeated with both positive and negative displacements in a quasi-static manner until the lateral forces required to produce these displacements approached zero. The measure of seismic durability used was the number of such cycles that a column sustained before losing structural integrity. The arrangement was intended to model that of bridge columns constructed during the 1960's. Three columns were retrofitted with prestressed, externally located circular hoops at intervals along the lower 4 ft. The spacing and size of these ties varied from column to column. The control column sustained less than two cycles before losing structural integrity; the retrofitted columns sustained a minimum of twelve cycles.

Authors:
Coffman,H. L., Marsh,M. L., Brown,C.

Keywords:
bridge and construction, reinforced concrete, bridge, columns, earthquake resistance, retrofitting, repair, splices, hoops, confined concrete, ductility, infrastructure, plastic hinges, inelastic deformations

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Abstract:
Bridge foundations in seismic regions are usually designed to withstand the plastic hinge moments that develop at the bases of the columns. Various hinge details have been proposed to reduce or even eliminate the moments transferred to the foundations, and thereby reduce the sizes and costs of the foundations. This study experimentally investigated the behavior of column specimens incorporating different moment-reducing hinge details. Tests were performed on reinforced concrete column specimens subjected to increasing inelastic lateral displacement under constant axial load. The study investigated effects on hinge performance of several parameters, including vertical discontinuity in the hinge detail, level of axial load, low-cycle fatigue characteristics, column aspect ratio, and different amounts of longitudinal and transverse reinforcement. The test results of this investigation showed that hinge details can be incorporated into columns to significantly reduce the moment capacity at the base of the columns. However, the moments are not negligible, as is sometimes assumed for design with the moment-reducing hinge details. Providing vertical discontinuity in the hinge resulted in reduced distress in the longitudinal reinforcement and improved the performance of the hinge. Preliminary design recommendations were proposed for the comprehensive design of moment-reducing hinge details at the base of the bridge columns.

Authors:
McLean,D. I., Lim,K. Y.

Keywords:
bridge and construction, seismic loading, reinforced concrete, plastic hinges, foundation

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Abstract:
A side bearing block foundation is used to resist overturning moments and lateral forces. Theoretical and experimental investigations were made to determine the ultimate moment capacity of a reinforced concrete footing subjected to vertical and horizontal loads and an overturning moment. The theoretical ultimate moment capacity was assumed to occur when the ultimate soil resistance was reached along the side bearing walls. It was found the resultant friction force at the base of the foundation greatly influenced the foundation to resist an overturning moment. The experimental ultimate moment capacity was determined from a deflection curve obtained from field data. A theoretical ultimate moment capacity was determined with the use of a finite el computer The results each of the three determinations were in acceptable agreement. Recommendations for further are made.

Authors:
Sorensen,H., Toreh,R.

Keywords:
base, computer, concrete, data, experimental, finite element, footing, forces, foundation, foundations, friction, loads, overturning, piles, reinforced concrete, resistance, soil, soil mechanics, soil pressure, stability, walls

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Abstract:
Under FHWA Demonstration Project No. 34, \"Cathodic Protection for Reinforced Concrete Bridge Decks,\" a slotted cathodic protection system was installed on the ES ramp in the Woodinville Interchange during the summer of 1985. The slotted cathodic protection system involves sawing by slots longitudinally in the existing deck at one-foot centers. Platinum wire or carbon strand wire is placed in the cut slots first and then conductive polymer is filled in the slots. Electric power from a rectifier supplies current to the wire and conductive polymer. The current then flows to the top mat reinforcing steel, giving the steel protection from further corrosion. The objective of the demonstration project was to familiarize the Washington State DOT with this new technology. This objective was fulfilled. Some problem areas with the system were identified during the work:1.A more positive method of finding grounding locations from the anode to nicks, ties, etc. needs to be developed. Perhaps an instrument can be used to supplement visual inspection. 2.The necessity for having a minimum of 112-inch cover from the bottom of the slot to the top of the needs to be resolved. 3.A better method of installing the conductive polymer needs to be developed. Hand spreading of the material from plastic bags results in sloppy work. 4.Procurement time for the rectifier needs to be shortened. 5.The project, once it has started, moves along very rapidly, there is very little time for on-the-job training of workers. Workmen should have prior experience at this work. In remote areas, sources of electrical power may not be available. It will be necessary for sources of power, such as solar panels or long-lasting batteries to be developed for this system.

Authors:
Roper,T. H., Henley,E. H. Jr

Keywords:
bridge, bridge deck, bridge decks, cathodic protection, concrete, concrete bridge, construction, corrosion, Deck, developed, flow, inspection, plastic, polymer, project, protection, reinforced concrete, reinforced concrete bridge, reinforcing, reinforcing steel, steel, steel protection, supply, System, technology, training, Washington, Washington state

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Abstract:
Under FHWA Demonstration Project No. 34, \"Cathodic Protection for Reinforced Concrete Decks,\" a non-slotted cathodic protection system was installed on the deck of the Yakima Bridge near Yakima, Washington, in the summer of 1985. The project involved repairing deck, then fastening Raychem pre-manufactured anodes to the deck to impress current to the mat rebar. Impressing current through the concrete to the top mat steel prevents corrosion of the steel. A latex modified concrete overlay was placed over the deck anode. The objective of the demonstration project to familiarize the Washington State DOT with new technology. This objective was fulfilled. Some problem areas with the system were identified during the work: 1.A more positive method of finding electrical grounding locations from the anode to nicks, ties, etc., needs to be developed. Some ties were exposed during the scarifying operation Perhaps an instrument can be used to supplement visual inspection. 2. An effective technique of allowing concrete trucks to drive on the anode without damaging needs to be developed. 3.An effective method needs to be developed to locate breaks in the anode as well as shorts. 4. In remote areas, sources of electrical power may not be available. It will be necessary sources of power, such as solar panels or long-lasting batteries to be developed for this system. 5. Since the project, once it has started, moves along very rapidly, there is very little time on-the-job training of workers. Workmen should have prior experience at this work. These problems need to be overcome to obtain a better quality product.

Authors:
Roper,T. H., Henley,E. H. Jr

Keywords:
bridge, bridge deck, bridge decks, cathodic protection, concrete, concrete bridge, construction, corrosion, Deck, developed, inspection, latex modified concrete, overlay, project, protection, quality, reinforced concrete, reinforced concrete bridge, steel, System, technology, training, truck, trucks, Washington, Washington state

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Abstract:
Problems with existing sludge disposal practices, combined with new information about its nutritive and soil-conditioning qualities, have led to accepted practices of land application of sludge. Both the Department of Transportation, as an agency with large land holdings and landscaping needs, and municipalities in Washington state may benefit from land application of sludge on roadsides.The use of sewage sludge on roadsides can potentially improve the growth of erosion control grasses, shrubs and trees while minimizing the costs for subsequent reseeding, replanting, or refertilization. Proper site selection and management techniques can potentially minimize public health and environmental impacts from heavy metals, nitrates, pathogens and organic toxicants. Steep roadside slopes, where erosion control is most needed, present a challenge to existing sludge application techniques, but one that is not insurmountable.A review of current national and local research, and a cost comparison analysis, have shown that roadside utilization of sludge may be a feasible practice without infringing on the health, safety and welfare of the public. Tasks are outlined for a demonstration study to investigate application techniques, vegetation types, public health and environmental impacts, and public acceptance and education.

Authors:
Cahn,D. C., Horner,R. R.

Keywords:
bridge and construction, bridge deck, waterproofing membrane, reinforced concrete, corrosion, salt, deterioration

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Abstract:
This study field tests and evaluates conditions of five bridge decks in Washington rehabilitated and waterproofed by WSDOT System 'C' membrane and paved with asphalt concrete overlay. The study also reviews and evaluates the WSDOT's membrane selection criteria. Based on the results obtained, the membrane system was generally effective in preventing chloride intrusion into concrete decks. Deterioration in concrete and corrosion in rebar, however, was detected. The deterioration was concentrated around, in the boundary, and within the rehabilitated areas. Those test sections which satisfied the WSDOT membrane selection criteria for protection of existing bridge decks showed minimum levels of concrete deterioration. Included in the study are also recommendations regarding rehabilitating, waterproofing, and testing bridge decks as well as selecting bridge decks for membrane waterproofing.

Authors:
Babaei,K.

Keywords:
bridge and construction, bridge deck, waterproofing membrane, reinforced concrete, corrosion, salt, deterioration

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