RAILROAD BRIDGE PERFORMANCE IN PAST EARTHQUAKES. Zolan Prucz, Ph.D., P.E., Modjeski and Masters, Inc St. Charles Ave.

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1 RAILROAD BRIDGE PERFORMANCE IN PAST EARTHQUAKES Zolan Prucz, Ph.D., P.E., Modjeski and Masters, Inc St. Charles Ave., Room 400 New Orleans, LA Telephone (504) Fax (504) Duane E. Otter, Ph.D., P.E. Transportation Technology Center, Inc. P.O Box 11130, DOT Road Pueblo, CO Telephone (719) Fax (719)

2 ABSTRACT A recent study sponsored by the Association of American Railroads indicates that generally accepted practices for railroad bridge design produce structures that perform well in earthquakes. Shaking typically has not been a problem for railroad bridges in past earthquakes. Ground movements have caused most of the damage. Design elements such as massive rigid piers and stiff structures combined with simple spans, large bearing seats, and minimal skew have provided good performance in earthquakes. Some of these elements contrast with present highway bridge design practice. High live load design requirements compared to highway bridges, along with sound detailing practices help to provide earthquake resistant structures and explain why some design elements perform well for railroad bridges but are not used for highway bridges. Researchers constructed a database containing information about 3,500 railway structures located in areas affected by earthquakes. The database includes structure data and estimated ground motion characteristics at structure locations based on earthquake ground motion records and other available data. In addition to quantifying damage sustained by railroad bridges (usually minimal), significant effort was placed on quantifying the number of bridges and the magnitude of the ground motion they sustained without damage. From these records, trends can be identified to note details that performed particularly well or poorly, which can be useful in the development of bridge seismic design and evaluation guidelines. This paper presents a summary of statistics and a review of bridge and detail performance under various seismic and soil conditions, along with recommendations for good seismic performance. Key Words: railroad bridges, seismic performance, earthquake effects on bridges, earthquake damage, earthquake resistant design.

3 1. INTRODUCTION Although earthquake damage to railway structures has been relatively limited, significant efforts have been made during the last 10 years to ensure adequate seismic performance in the future. In 1993, the American Railway Engineering and Maintenance-of-Way Association (AREMA) established a stand-alone committee on seismic design (AREMA Committee 9) to develop seismic design guidelines specific to railway structures. In 1997, the U.S. Department of Transportation and the Japanese Ministry of Transport signed an agreement with the objective of improving the general understanding of the behavior of railway structures in earthquakes and reducing the potential for casualties, damage, and disruption of traffic. Transportation Technology Center, Inc. (TTCI), under the sponsorship of the Association of American Railroads (AAR), has conducted studies including the development of seismic response criteria and testing seismic resistance on ballasted and open deck steel bridge spans. The AAR has also sponsored seismic full-scale resonance tests conducted by the University of Nevada, Reno. This project is also part of the efforts that are being made to improve the understanding of the behavior of railway structures during earthquakes. Its main objective is the review and evaluation of the past performance of both damaged and undamaged structures.

4 Specific project tasks were to: Collect information on earthquakes, affected regions, and potentially affected railway structures. Collect information on railway structure performance. Build database of performance of structures. Identify trends and details related to structure performance. Make recommendations regarding seismic design and detailing. Although the main emphasis was on bridge structures, the performance of other railway structures such as the tunnels, track, embankments, railway facilities, and rolling stock was also reviewed and assessed. The bridge data collected consisted of information on each bridge s structure characteristics such as type, length, height, number of spans and span length, as well as information on its seismic performance. Other data collected included general earthquake information (magnitude, intensity, duration, mechanism, felt and damaged areas, and general effects), ground motion data (distribution of intensity, strong motion records, and attenuation relations), geotechnical data (soil conditions, liquefaction potential, and slope stability), and performance information on nearby structures (highways and buildings). The sources of information used included published reports and articles, books, conference and workshop proceedings, and communications with railroad bridge engineers. Based on the information collected, a Microsoft Access database was developed that documents the performance of railway structures during past earthquakes and allows for structure performance analysis. Since the extent of damage sustained by railroad bridges has

5 been relatively low, most of the data collected documents undamaged structures. Survey of the performance of undamaged structures subjected to strong ground vibrations and movements also offers a valuable source of information that has generally not been utilized. 2. EXTENT OF DAMAGE TO RAILWAY STRUCTURES 2.1 General With the exception of a few large earthquakes discussed in the following sections, the damage to railway structures has been light to moderate and limited to relatively few structures. The proceeding paragraphs include a general description of the performance of railway structures during the 1886 Charleston Earthquake, the 1906 San Francisco Earthquake, and the 1964 Alaska Earthquake, which caused the most extensive damage. Structure characteristics, site characteristics, and individual structure performance information from these and other earthquakes that were close to railroad lines are included in the Structure Performance Database described in Section 4. A detailed review and summary of railway structure damage during earthquakes may be found in (1). 2.2 Charleston Earthquake of 1886 One of the first well documented surveys of damage to railway track, embankments, and bridge structures was conducted by C. E. Dutton after the 1886 earthquake in Charleston, South Carolina,(2), which has an assigned magnitude of 7.7. The main objective of the survey was to locate the epicenter(s) of the earthquake. The information collected included a detailed account of the earthquake effects on the ground and to the structures in the area. Locations and structures that were not damaged were also surveyed and reported.

6 Although railroad track at some individual locations sustained significant lateral and vertical distortions, the damage to bridges was somewhat limited to several long timber trestles on loose sand deposits or swampy areas and to the bridge crossings over the Ashley River and the Rantowles Creek. Both crossings included a drawbridge with timber trestle approaches on flat, marshy land. The damage report for the Ashley River crossing states that the drawbridge was closely jammed by the earthquake, the immediate cause being the sliding or creeping of both river banks towards the center of the stream, carrying the trestle with them. At Rantowles Creek, it was similarly reported that the river banks slid toward midstream, piles dragged attached bents from vertical positions, superstructure flexed transversely and vertically, stringers bulged upward, rails damaged, and caps of bents pulled upward. During the damage survey the effects of the ground conditions on the degree of damage were noticed, but not fully understood. The report describes a broad sandy flat section of a higher elevation where surprisingly there was no damage even though the damage around this section was severe, noting that the change of intensity is so abrupt as to suggest some exceptional cause or condition. 2.3 San Francisco Earthquake of 1906 The damage to railway structures during the 1906 earthquake that occurred in San Francisco, California, assigned magnitude of 8.3, has also been surveyed and reported in detail(3). During the earthquake, several timber trestles were seriously damaged, but the damage descriptions note the lack of damage to other bridges and the relation of the

7 damage to the soil conditions. It is reported that over marshes the timber trestles suffered more or less from the movement of the soft material into which the piles were driven, while at other locations the effect on trestles was very slight. Movable bridges across small creeks and inlets around the San Francisco Bay (generally on soft ground) were affected by a slight movement of their piers. A swing span at Black Point over Petaluma Creek, which was open at the time of the earthquake, was shifted on the pivot pier about 2 feet. With a few exceptions, fixed bridges (other than the timber trestles) were not affected seriously. The bridges over the Russian River at Healsdburg and Bohemia were shifted slightly on the piers at one end, and one of the piers of the Southern Pacific Bridge across the Pajaro River at Watsonville moved upstream about 3 feet. The Southern Pacific Bridge, which spanned over a fault line across the Pajaro River near Chittenden, was the only bridge to sustain serious damage. The damage consisted of pier movements, cracked wing-walls, displaced coping stones, and horizontal cracking of piers. Although the damage was significant, the bridge managed to accommodate a relative movement of 3.5 feet between abutments, without collapse. One of the end spans was dragged off the bridge seat, but it did not fall, being held up by the riveted connection to the next span to the east and by the fastenings of the rail. The survey of the damage caused by this earthquake revealed and documented for the first time how local geology and soil conditions play a key role in the severity of shaking and permanent ground deformations, and in the extent and severity of structure damage.

8 2.4 Alaska Earthquake of 1964 The most extensive damage to railway structures occurred during the Alaska earthquake of 1964, which had a long duration and a local magnitude of 8.4. A thorough, welldocumented survey of the effects of the earthquake was made and published in a series of reports, including a separate report on railway structures.(4) It was found that almost all the structure damage resulted from transient and permanent displacements of the foundation materials. The damage to timber trestles included compression of the decks followed by large vertical and lateral distortions, shifting of bents toward the streams, and shifting and tilting of abutments. Bridges with steel superstructures experienced shifting and tilting of piers, and movement of superstructures on top of piers after failure of bearings and anchor bolts. The damage to the track and the embankment was extensive over an affected area of about 100 miles. In this area, which is underlain by unconsolidated sediments, 125 bridges and over 110 culverts were damaged. The damage was concentrated at sites with especially soft, water-laid, non-cohesive young sediments. Similar structures on older, drier sediments, or on till or bedrock, were nearly undamaged. It was noted that the seismic shaking mobilized the sediments, which then spread laterally toward topographic depressions such as stream crossings where bridge superstructures compressed and their supports crowded together toward the center of the stream channels. Analysis of the bridges damaged by displaced foundation materials found a strong correlation between total sediment depth and the severity of the damage. About 50 percent of the damaged bridges had severe damage, and all of them were underlain by

9 more than 100 feet of sediments. About 26 percent of the damaged bridges had moderate damage; of which about 30 percent were underlain by more than 100 feet of sediment, 50 percent by feet of sediment, and 20 percent by less than 50 feet of sediment. About 24 percent of the damaged bridges had slight damage; of which about 20 percent were underlain by more than 100 feet of sediment, 50 percent by feet of sediment, and 30 percent by less than 50 feet of sediment. From the analysis of the data collected, it was found that the damage generally increased with: Increasing thickness of unconsolidated sediments. Decreasing depth to the water table. Proximity to topographic depressions. Proximity to the area of maximum strain-energy release. The relationship between the damage, the local geology, and physiography was found to be so clear that maps of surficial geology and physiography were used to identify only a few geologic-physiographic units that correlated the damage to the site. Based on these and other findings, the following general conclusion was made: In an area subjected to a large long duration earthquake, structures on thick water-laid non-cohesive wet young sediments that range from silt to gravel and have a wide range in penetration resistance values should be expected to sustain severe damage, either from displacements of the foundation materials, or from severe ground motion. (4)

10 3. PERFORMANCE OF UNDAMAGED STRUCTURES Although the number of railway structures damaged in earthquakes is relatively low, the total number of railway structures that survived earthquakes without damage is quite high. Review and analysis of the performance of undamaged structures is as important, if not more so, as that of damaged structures to the understanding of structure response to earthquakes. This was noted as early as 1889, when referring to the Charleston earthquake C. E. Dutton wrote, it is as interesting and quite as important to know what the earthquake failed to do as to know what it did. (2) In order to analyze the performance of undamaged structures during earthquakes, an extensive search was made to collect information on those earthquakes that could potentially cause structural damage to railroad lines and the structures within the affected area, as well as the effects of the earthquake at the structure site. The information collected was entered into a structure performance database, which is described in the following section. 4. STRUCTURE PERFORMANCE DATABASE The structure performance database provides easily accessible information on structures that experienced earthquakes, the earthquake affects at the site and the performance of the structure. It also provides a means for the analysis of the data. Two databases À a Structure Damage Database, which included damaged structures and a Structure Survivability Database, which included undamaged structures, were originally developed and later combined into one. The database format is Microsoft Access 2000.

11 4.1 Database Structure General In its simplest form, a database is a table with columns that represent specific types of information (fields) and rows that represent sets of information called (records). When the table becomes large and includes repeat information in its records, a database will allow for the use of several tables with different types of data, which can be related to each other in such a way as to allow for data query. Other important features of a database include forms, queries, and reports. The forms make it easy to view and enter information into the tables, the queries allow for locating and retrieving specific information based on certain criteria, and the reports allow for printing the data Database Tables and Forms The main tables in the Structure Survivability Database include EARTHQUAKES, STRUCTURES, and PERFORMANCE. Other related tables include Railroad LINES, REFERENCES, and several tables with abbreviation information. Figure 1 shows a sample view of a portion of the STRUCTURES table. The PERFORMANCE table is related to the information included in the EARTHQUAKES and STRUCTURES tables through an earthquake ID field and a structure ID field. In this table format, data is not repeated and the tables are kept to a manageable size. Figure 2 shows a detailed view of the relationships between tables, which also lists the fields in each table. The database forms include Earthquakes, Structures, Performance, References, and Railroad Lines. Each form allows for a convenient way of viewing and entering data in

12 the appropriate tables. The forms show the table fields displaying one record at a time. A Switchboard (see Figure 3) introduces the user to the database options and provides access to the database forms. Figures 4, 5 and 6 provide views of the Earthquakes, Structures and Performance forms, and Figure 7 shows a view of the References and Railroad Lines forms. The following is a description of the main tables: Earthquakes: The EARTHQUAKES fields include the date and location of the earthquake, as well as information on the earthquake magnitude, intensity, duration, mechanism, displacement, and rupture location and length. Fields that describe the felt and damaged area, the general effects, and the general damage that was caused by the earthquake are also included. To maintain a relatively complete listing of past earthquakes, all those with a magnitude of about 5.5 and over were included, even though many of them did not affect railroad lines. Structures The STRUCTURES fields include information on the location of the structure, the year built, the number of similar structures at one location, the structure length and maximum height to top of rail, the number of spans, the length of the longest span, the alignment, the superstructure type, the deck type (open or ballasted), the span type (fixed or movable lift, swing or bascule), the substructure types, and the soil type. This table also includes a description of the structure and its history and a description of the soil conditions. Table 1 lists the bridge superstructure and substructure types considered, along with their abbreviations.

13 Performance The PERFORMANCE fields include earthquake and structure ID s, distance of the structure to the epicenter or to a well-defined fault line, an estimate of the ground acceleration and the earthquake intensity at the site, damage intensity level, damage types, and cause of damage. Also included are descriptions of the damage to the structure and to nearby structures. Table 2 lists the damage intensity levels, the damage types, and the causes of damage considered, along with their abbreviations Database Queries Queries provide an easy way of retrieving, reviewing, and sorting specific information based on desired criteria, even when the data comes from several linked tables. An example of a query design is included in Figure 8. This query retrieves selected fields of all records of bridges and provides a count of structures based on the following criteria: Span length larger or equal to 40 feet. Bridge height larger or equal to 45 feet. Bridge site had either an acceleration larger or equal to 0.3g, an intensity larger or equal to 7, or a distance from the epicenter of 20 miles or less. Bridge had no damage. Figure 8 shows the results of the query. The use of queries allows for the retrieval of very specific information, such as for example, a list of through truss bridges with concrete piers, located at a site susceptible to liquefaction that experienced shifting of the superstructure on top of the substructure.

14 4.2 Applications The database can be used to: Obtain structure and performance data for a specific structure and earthquake. Obtain structure and performance data by structure type or structure characteristics (e.g., length, height). Obtain structure and performance data for a specific range of ground accelerations, intensities, or distances from earthquake epicenter. Obtain structure and earthquake data by damage type, cause, or intensity. Input future structure, earthquake, and seismic performance information. 4.3 Future Database Development While the more recent earthquakes and their effects on structures have been well monitored and documented, the information available from earlier earthquakes is limited. As a result, there is missing information (such as ground acceleration at a specific site) in the database entries. However, some of the missing data may become available as research and reporting on the past earthquakes continues. As earthquakes continue to occur, increasingly accurate information will be generated from the strong motion instrumentation network in place today, and it is expected that this database will continue to be updated.

15 5. STATISTICAL TRENDS The total number of structures included in the database STRUCTURES table is 3,508, of which 3,243 are bridges, 145 culverts, 74 tunnels and the rest are other structures. Since some of these structures experienced more than one earthquake, the number of structures listed in the PERFORMANCE table is larger. It includes 4,313 structure cases, of which 3,969 are bridges, 228 culverts 74 tunnels and the rest are other cases. The 3,969 bridge cases include 1,139 timber trestles, 708 bridges with longer span steel superstructures (DPG, TPG, DTP, DTR, TTP, TTR and PTR), 1,180 bridges with shorter span steel superstructures (RTB and SBM), and 942 bridges with concrete superstructures (PCB, PCG, PCS and RCS). Table 1 lists the structure abbreviations. Out of a total of the 3,969 bridge cases, only about 100 bridges had moderate or severe damage, which is a very low number from a statistical perspective. Therefore, the statistical data described herein includes only undamaged structures. Figure 9 includes histograms of undamaged bridge performance. Figure 9a shows the relation of the number of bridges to their distance from earthquake epicenters for all bridge types located within 70 miles of earthquake epicenters. About 560 bridges were located with a distance of 10 miles or less from earthquake epicenters and about 2,200 bridges were located with a distance of 30 miles or less from earthquake epicenters. Figure 9b shows a histogram of the earthquake intensity at undamaged bridge sites, for all bridge types located in areas that experienced an earthquake intensity of VII or higher. There were about 46 bridges in an area of intensity IX or higher, about 707 bridges in an

16 area of intensity VIII or higher, and 2,730 bridges in an area of intensity VII or higher. Figure 9c shows a ground acceleration histogram for bridge sites that experienced an acceleration of over 0.2g without damage. Two bridge sites had a ground acceleration of 1.2g and about 140 bridge sites had a ground acceleration of over 0.5g. The total number of bridges that survived a ground acceleration of over 0.3g and 0.2g is about 670 and 1,390, respectively. Similar information can be obtained for specific bridge types, bridge characteristics, locations, and earthquakes. 6. SUMMARY OF FINDINGS The review and evaluation of the seismic performance of damaged and undamaged structures showed several trends and similarities between earthquakes. In general: The damage to railroad bridges has been relatively limited, and that which did occur was a result of ground movements in areas such as flood plains, wet alluvial valleys, marshy lands, or manmade fills. Within a certain range of distance, the nature of the ground had a greater effect on structural damage than the distance from the fault or the epicenter. The severity of ground-induced damage increased with the thickness of the sediments. There was extensive track and embankment damage in locations where moderate to severe bridge damage occurred. Railroad bridges on bedrock or firm soil typically survived earthquakes without damage À even in areas where other structures were damaged.

17 Ground shaking and ground movements have had different effects on bridges. The damage to railroad bridges due to ground shaking has been minimal. The damage to other structures such as highway bridges caused by ground shaking could be traced to design and detailing practices. A large number of railroad bridges have been in close proximity to earthquake epicenters and have experienced high intensity and ground acceleration levels without damage. Simple spans and large bearing support areas on top of piers helped accommodate ground-induced movement and tilting of piers. Bearing and anchor bolt failures and shifting of cap stones allowed movement of superstructures on top of piers, which prevented more extensive damage to the substructure 7. RECOMMENDATIONS Because of their different effects, measures to improve a bridge s response to ground shaking and to ground movements are listed separately. Factors that contribute to good seismic response to ground shaking include: Proper selection of structure type and configuration, as well as sound design. Characteristics such as simplicity, symmetry, and regularity. Good detailing. Current railroad bridge design and construction practices typically follow these requirements.

18 Ground conditions susceptible to seismic induced movements should generally be avoided. However, when this is not possible, the following suggestions may help to reduce damage in these areas: Avoid bridge and foundation types that cannot withstand differential movements, such as rigidly connected substructure and superstructures. Design of bridges that cross or are located at the edges of stream channels to accommodate both the compression that develops as stream banks move closer together and the horizontal skewing that usually accompanies compression. Use simple spans to accommodate differential vertical displacement of the foundations. Wide pier and abutment bearing surfaces and bridge bearings that can allow considerable end travel. Avoid crossing channels at an angle to prevent lateral skewing of bridges due to the movement of stream bank sediments towards the center of the channel. Presently, most of the seismic bridge design provisions are based primarily on structure design for ground accelerations. It is recommended that future seismic provisions also include ground movement criteria as a main design case. 8. ACKNOWLEDGEMENTS The authors would like to acknowledge the sponsorship of the Association of American Railroads. The assistance provided by William G. Byers and Donald E. Lozano,

19 Burlington Northern Santa Fe Railway, and Kevin Moran, Union Pacific Railroad, is greatly appreciated. 9. REFERENCES 1. Byers, William G., Railroad Bridge Behavior During Past Earthquakes, Building an International Community of Structural Engineers, S.K. Gosh & Jamshid Mohammadi, eds., ASCE, 1996, pp Dutton, Clarence Edward, The Charleston Earthquake of August 31, 1886, Ninth Annual Report, U.S. Geological Survey, Government Printing Office, Washington, D.C., 1889, pp Wallace, J.H. et al, Report of Committee on the Effect of the Earthquakes on Railway Structures, The Effects of the San Francisco Earthquake of April 18th, 1906 on Engineering Constructions, Paper No. 1056, Appendix E, Transactions ASCE, Vol. LIX, December 1907, pp McCulloch, David S. and Bonilla, Manuel G., Effects of the Earthquake of March 27, 1964, on the Alaska Railroad, USGS Professional Paper 545-D, U.S. Government Printing Office, Washington, D.C., 1970.

20 TABLE 1. Database Structure and Soil Descriptions, and Abbreviations Superstructures Substructures CAB Concrete Arch Bridge ca Concrete Abutments CEB Concrete Encased Beam cb Concrete Bents DPG Deck Plate Girder cp Concrete Piers DTP Deck Truss Pinned sb Steel Bents DTR Deck Truss Riveted sbc Steel Bents on Concrete Foundation PCB Pre-stressed Concrete Box sc Steel Cylinder Piers PCG Pre-stressed Concrete Girder st Steel Towers PCS Pre-stressed Concrete Slab sa Stone (or Masonry) Abutments PTP Pony Truss Pinned sp Stone (or Masonry) Piers PTR Pony Truss Riveted tb Timber Bents RCS Reinforced Concrete Slab or Box cpp Concrete Pivot Pier RTB Rail Top Bridge (Stringer) spp Stone (or Masonry) Pivot Pier SBM Steel Beam Span mcs Misc. Concrete Substructure TPG Through Plate Girder mss Misc. Steel Substructure TST Timber Stringers mts Misc. Timber Substructure TSP Timber Span Others: TTP Through Truss Pinned CULVERT TTR Through Truss Riveted or Bolted TUNNEL MS Movable, Swing TRACK ML Movable, Lift EMBANKMENT MB Movable, Bascule FACILITY Deck Car OD Open Deck LOCOMOTIVE BD Ballasted Deck TRAIN Track Soil T Tangent fs Firm Soil C Curve ss Soft Soil S Spiral ls Liquefiable Soil

21 TABLE 2. Database Damage Description and Abbreviations Damage Intensity No damage L Light damage (does not affect traffic) M Moderate damage (may affect traffic) S Severe damage or collapse Damage Type 1 Shifting or tilting of bents, piers or abutments 2 Cracks or anchor bolt damage at the base of steel towers 3 Abutment damage 4 Concrete column damage 5 Concrete pier damage 6 Masonry pier damage 7 Collapsed bents, piers or abutments 8 Shifting or tilting of bent caps, cap stones or concrete pedestals 9 Damage of bearings and/or anchor bolts 10 Damage of end diaphragms or cross frames 11 Shifting of superstructure on top of piers 12 Unseated spans 13 Compression of superstructure 14 Vertical or horizontal distortion of the superstructure 15 Collapsed spans due to inadequate support width 16 Failure of approaches and fill material behind abutments 17 Damage of counterweight guides in vertical lift bridges 18 Tunnel damage 19 Highway or other structures on track 20 Landslide on track 21 Track horizontal or vertical distortion or pull apart 22 Culvert damage 23 Embankment failure 24 Overturned cars and/or locomotives 25 Derailed trains 26 Damage to railroad buildings and facilities Cause of Damage A B C D E F G H Ground vibrations Movement of alluvium material towards stream channels Local ground movement due to soil failure or seismic shock waves Loss of soil resistance due to liquefaction Lateral pressure from backfill Landslide Fault offset Tidal wave

22 Figure 1. View of Database STRUCTURES Table

23 Figure 2. Database Table Relationships

24 Figure 3. Database SWITCHBOARD

25 Figure 4. Database EARTHQUAKES Form

26 Figure 5. Database STRUCTURES Form

27 Figure 6. Database PERFORMANCE Form

28 a) REFERENCES Form b) Railroad LINES Form Figure 7. Other Database Forms

29 a) Query Design b) Query Results Figure 8. Example of Query Design and Query Results

30 All Bridge Cases; Dist. from Epicenter <= 70 Miles 1000 No. of Bridge Cases Distance from Epicenter (Miles) a) Undamaged Bridge Distance from Earthquake Epicenters All Bridge Cases; Intensity >= VII (MM) 2500 No. of Bridge Cases VII VIII IX X Intensity (MM) b) Earthquake Intensity at Bridge Sites All Bridge Cases; Acceleration > 0.20g No. of Bridge Cases Ground Acceleration (xg) c) Ground Acceleration at Bridge Sites Figure 9. Histograms of Undamaged Bridge Performance

31 Listing of Table Titles and Figure Captions Table Titles Table 1. Database Structure and Soil Descriptions, and Abbreviations Table 2. Database Damage Description and Abbreviations Figure Captions Figure 1. View of Database STRUCTURES Table Figure 2. Database Table Relationships Figure 3. Database SWITCHBOARD Figure 4. Database EARTHQUAKES Form Figure 5. Database STRUCTURES Form Figure 6. Database PERFORMANCE Form Figure 7. Other Database Forms Figure 8. Example of Query Design and Query Results Figure 9. Histograms of Undamaged Bridge Performance