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INTRODUCTION

Soon after the 2007 collapse of the I-35W Bridge over the Mississippi River, speculations flew regarding the cause of this catastrophic failure. Only five days after the failure, one bridge engineer was quoted as saying, “Rivets are old technology …” and that “rivets slip”, implying that a riveted connection may be the cause for the collapse. Though the main truss gusset plates soon after were recognized as the true cause for the collapse, these statements reflect the general misunderstanding bridge engineers have for the way riveted connections work and their durability. With essentially no major riveted bridge construction for over four decades, the bridge construction community has steadily forgotten how rivets work, and when compared to the work horse slip-critical, high strength bolts, rivets appear both inferior and relatively simple. On the contrary, riveted construction may be the most studied structural connection overall. From 1860 through the 1940s, over 1400 articles and papers in North America and Europe were written discussing the performance of these heated and manipulated metal cylinders. However, riveted construction will always be a labor-intensive operation, and rivets were rapidly replaced starting around 1960 as welding and high-strength bolts became the preferred methods of structural connection. This transformation occurred due to economic considerations, not concern for the performance of riveted connections.

A BRIEF HISTORY OF RIVETED BRIDGE CONNECTIONS

Metal rivets had been used for centuries to connect small metal straps. Only with the development of larger rivets in the early 1800s could rivets then be truly considered for structural applications. However, the first American iron bridge of the 1840s used bolts and threaded rods to connect members. Central Park’s famous Bow Bridge (1862) incorporates countersunk bolts to attach adjacent segments of the cast iron arch. The first use of structural rivets on a European bridge was built in 1860. In the United States, rivets were first used on iron bowstring and other small bridges in the late 1860s, steadily replacing bolts as a means of fabricating built-up bridge members. Pin-connections dominated truss connections into the 1890s, but with the increased acceptance of rivets and the development of pneumatic rivet guns, rivets gradually replaced pin connections for all but the largest truss connections. Though rivets dominated the field of structural connections through the 1950s, their reign was not completely respected. Structural riveting, especially with field connections, required at least four workers in a gang. Labor costs for riveting led engineers to investigate alternate connection methods as early as 1920. The 1920s saw the development of the cold-driven rivet-bolt known as the structural ribbed bolt (discussed later). This connection was used sparingly on bridges, most notably on floor beams connections for the strictly utilitarian pony trusses fabricated by the Ohio Bridge Company in the 1950s.

Design and Performance of Riveted Bridge Connections William J. Vermes, P.E., Jones-Stuckey, Ltd., Inc., Akron, Ohio KEYWORDS: Rivets, bridge connections, friction, bearing, shear stress, fatigue, fabrication. ABSTRACT: From the late 1800s to 1960, riveted construction was the predominant connection method of both steel bridge fabrication and erection. Now, nearly a half-century since the general use of rivets ended, many American engineers, unfamiliar with riveted design, look at rivets with suspicion and as an inferior connection. However, review of past riveted construction practices, recent research and current field observations of riveted steel bridges show that riveted connections are indeed an enduring and premium fastener among existing bridge connections.

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However, the true competition and eventual successors to rivet were welding and high-strength bolts. Both of these connections saw early development and testing by the 1930s. With smaller work gangs and thorough testing, welding and bolting were generally accepted by the 1950s. After 1960, many new steel bridge constructions were completed utilizing shop riveting and the relatively efficient bolted connection for all field connections. By the end of the 1960s, riveted connections on bridges were gone. Among the last riveted constructions found on American bridges are the shop rivets installed on the suspension bridge towers of the Second Delaware Memorial Bridge (Wilmington, Delaware, opened 1965) and the field connections of the lost I-35W Bridge over the Mississippi River (Minneapolis, Minnesota, opened 1967). HOW RIVETS WORK The popular understanding among today’s bridge engineers regarding how rivets work has been passed down from the conservative view set forth by our engineering forefathers 100 years ago or so. Rivets are viewed strictly as a bearing connection (Figure 1). No clamping force is considered from the rivet shank, and thus no load is transferred between adjoining steel members via friction between their faying surfaces. This is a very simplistic view for the rivet is a very complex connection and difficult to calibrate. Because of this complexity, the interaction between the heated rivet and the fabricated hole, quality riveting was more of an art than an analytic procedure.

Figure 1 – Rivet Terminology

THE RIVET Before installation, cold rivets are placed in a forge where they are cooked (heated) to a cherry red color. The actual required temperature of the rivet is in a narrow range from 1850 to 1900° F for approximately 20 minutes. Heating rivets for too long or at too high of a heat will result in defective rivets, either “burned” rivets with pitting on the shop head (Figure 2), or added brittleness due to a changed crystalline structure within the rivet steel. Conversely, to heat a rivet too little results in a rivet shank that does not fill the hole completely. Temperatures within these forges can be difficult to calibrate, and thus heating rivets requires a feel for metal that now lies with today’s blacksmiths.

Figure 2 – Pitting on Head Indicating “Burned” Rivet (Note: This photo was

taken after 77 years of service.) Once the rivet is adequately cooked, it is placed in the rivet hole and bucked up (held in place) on the shop head side. The protruding shank is then pressed into the semispherical shape. Shop rivet heads were formed with a single hit from presses while field rivet heads were made with multiple hits using hand-held pneumatic rivet hammers, also affectionately known as hell dogs by ironworkers. The initial contact on the rivet shank would upset the shank; viz. the first contact would cause the shank to swell, filling the rivet hole completely with rivet shank, at least in theory. Past and present examinations of cut rivet sections show that gaps ranging from 0.005 to 0.03 inches occur between the shank and base metal. These gaps are more likely to occur at the center and shop head end of the rivet, and was more pronounced with rivets having longer grips, or shank length (Figure 3).

Shop Head

Plies Field Head

Shank

Figure 3 – Comparison of Gap Between Rivet Shank and Base Metal

THE RIVET HOLE By the early 1900s, bridge engineers knew that the performance of the riveted connection also depended on the method that the rivet hole was made and the quality of the rivet hole alignment. Typically, there are three methods of hole fabrication: punched, subpunched & reamed and drilled. Punched holes are the less desirable as severe deformations occur along the hole perimeter, providing microcracking and uneven bearing areas for the rivet shank. Drilled holes were time consuming, required frequent changing of drilled bits (especially with A8 nickel steel of the 1910s through 1930s) and produced much heat in the base metal. The preferred and common method for rivet hole fabrication was the hybrid subpunch and ream (drill) approach. Numerous tests conducted up through 1940 generally concluded that the subpunch and ream method produced holes with the fewest defects and provided the best fatigue resistance in the riveted connection (Figure 4).

Figure 4 – Various Rivet Hole QualitySubpunched & Reamed (Left

Punched (Right)

Comparison of Gap Between Rivet

By the early 1900s, bridge engineers knew that the performance of the riveted connection also depended on the method that the rivet hole was made and the quality of the rivet hole alignment. Typically, there are three methods of hole

cation: punched, subpunched & reamed and drilled. Punched holes are the less desirable as severe deformations occur along the hole perimeter, providing microcracking and uneven bearing areas for the rivet shank. Drilled holes were time

d frequent changing of drilled bits (especially with A8 nickel steel of the 1910s through 1930s) and produced much heat in the base metal. The preferred and common method for rivet hole fabrication was the hybrid subpunch and ream

ous tests conducted up through 1940 generally concluded that the subpunch and ream method produced holes with the fewest defects and provided the best fatigue resistance in

Various Rivet Hole Quality:

(Left) &

QUALITY OF THE INSTALLED RIVETInspections of removed rivets reveal a multitude of questions that have contributed to contractors’ claims of the “extreme difficulty” in removing rivets without damaging the base metal. As one would expect, these questions have a multitude of answers. One difficulty encountered by fabricators and ironworkers with the placement and removal of rivets is the occasional misalignment of the steel plies, known as the camming effectthe hole, the hot rivet, 1/16″ smaller in diameter than the rivet hole, is flexible enough to be placed in an imperfectly aligned hole. Additionally, for shop driven rivets, it was determined that excessive force from the hydraulic presses used to the rivets would compress the base metal and deform the edge of the rivet hole, producing at times deep grooves to the newly driven rivet shank (Figure 5).

Figure 5 – Comparative Hole Deformation Under Increasing Shop Hydraulic Forces

When rivets are driven with pneumatically rivet hammers in the field, the ironworker needs to apply an even and consistent force on the rivet hammer to form an even and concentric rivet head. Failure to do so was considered grounds for rejection by the inspector and the subsequent removal of the rivet. A list of defective rivet characteristicsAppendix A. Examination of pre-1890s rivets removed during bridge rehabilitations generally show that nonconcentric rivet heads and uneven shanksthe location of each steel ply of the rivet hole (Figure 6). Review of rivets removed from bridges erected in the 1910s through 1930s show the nearperfect shape of nearly all rivet heads and alignment

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QUALITY OF THE INSTALLED RIVET Inspections of removed rivets reveal a multitude of questions that have contributed to contractors’ claims of the “extreme difficulty” in removing rivets

ase metal. As one would expect, these questions have a multitude of

One difficulty encountered by fabricators and ironworkers with the placement and removal of rivets is the occasional misalignment of the steel

camming effect. When placed in ″ smaller in diameter than

the rivet hole, is flexible enough to be placed in an hole. Additionally, for shop

driven rivets, it was determined that excessive force from the hydraulic presses used to upset and drive the rivets would compress the base metal and deform the edge of the rivet hole, producing at times deep grooves to the newly driven rivet shank

Comparative Hole Deformation

Shop Hydraulic Forces en rivets are driven with pneumatically rivet

hammers in the field, the ironworker needs to apply an even and consistent force on the rivet hammer to form an even and concentric rivet head. Failure to do so was considered grounds for rejection by the

ector and the subsequent removal of the rivet. characteristics is included in

1890s rivets removed during bridge rehabilitations generally show that non-concentric rivet heads and uneven shanks showing the location of each steel ply of the rivet hole (Figure 6). Review of rivets removed from bridges erected in the 1910s through 1930s show the near-perfect shape of nearly all rivet heads and alignment

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of the shanks. This drastic improvement in quality must be attributed to the overall constant refinement of the craft by bridge fabricators and erectors in the early 20th Century.

Figure 6 – Extreme Camming of Shank on Iron

Rivets from an 1875 Truss Bridge DESIGN ASSUMPTIONS & VALUES

For over a century, there has been no change regarding the way allowable stresses for rivets have been presented to designers. Allowable shear stresses have been determined based on the cross sectional area of the shank and the grade of the rivet steel, while allowable bearing stress is based on the product of the diameter and plate thickness of the ply. With increased yield strength of rivet steel and base metal, improved craftsmanship of riveting and rivet hole alignment and fabrication, allowable rivet stresses steadily rose during the 20th Century. A sampling of these values is shown in Table 1 and expanded further in Appendix B. Additionally, standard practice called for the installation of 20 to 25% more rivets in field connections than design called for to account for the non-ideal working conditions and the added difficulty for ironworkers to drive rivets perfectly.

Stress Allowable Stress (psi)

1903 Cambria 1923 1953

AASHO 2009 ASSHTO

* Shear 6,000 7,500 13,500 20,000 Bearing 12,00 15,000 27,000 40,000

* For high-strength A502 steel Table 1 – Comparison of Allowable Shear and

Bearing Stress

Still, allowable stresses do not fully describe how rivets work, and despite extensive research performed on riveted connections, engineers typically stated several simplistic rules regarding how rivets work: The most common rules-of-thumb were, and still are: 1. Rivets completely fill the holes they are driven into,

2. Any friction between plies is neglected, 3. Bending stresses in rivets are neglected, and 4. Stress is evenly distributed throughout joint.

The root of these assumptions is due to the difficulty for engineers to quantify the tensile stress in the rivet shank and the resulting clamping force of the rivet onto the plies as the rivet shank cooled. However, past tests performed of riveted connections revealed that these four assumptions are all false. However, bridge engineers had known that these assumptions were incorrect beginning at the early stages of riveted bridge construction. In Designing of Ordinary Highway Bridges (1888), Waddell discussed both the means that rivets work and the uncertainty of their long-term performance:

Where two plates are riveted together, the rivets, driven when hot, contract, or tend to contract, in length when cooled, thus drawing the plates together, and producing a friction, which it is necessary to overcome before shear can come upon the rivets. Whether this friction will continue indefinitely is doubtful, for rivets occasionally become loosened when the structure is subjected to oft-repeated loads; so it is not legitimate to become dependent upon the friction in order to reduce the number of rivets…. Again: if the friction were to be dependent upon it would be only right to allow for the initial tension on the rivets, which tension is great enough to force off the heads.

The above text likely contributed to establishment of the first two assumptions. Furthermore, though he does not mention the phenomena by name, Waddell’s statement likely contained one of the earliest discussions of slip within loaded riveted connections. As stated previously, rivet shanks are not in complete contact with the circumference of the rivet holes and friction contributes to the performance of the connection. To demonstrate and quantify, researchers performed numerous lab tests in the 1930s to better understand how rivet truly work. One such test involved simple rotation tests of

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adjoining plies about solitary rivets, indicating that friction is indeed present. A more definitive test measured the initial tension present in cooled rivets of 3- and 5- inch grips (the total length of the steel plies). After measuring the distance between fixed points on both rivet heads, the tension was relieved as one of the steel plies was removed by a lathe. The measured recoverance (contraction) of the rivet demonstrated that the rivets were subjected to tensile stresses commonly above the yield stresses, and that the rivets were stretched in the order of 0.0012 inches per inch of shank as they cooled and were not permitted to correspondingly contract. Additionally, one lab test of the 1930s identified slight bending within rivet shanks through observations of slight deformations of drilled holes placed within rivet shanks, and just like bolted connections, many lab results have demonstrated that stresses are not distributed evenly throughout a connection. HOW RIVETS SLIP Perhaps with the inspection of rivet holes following removal of the rivet, many contemporary engineers have concluded that the misalignment of the plies is evidence of slipped riveted connections that they have heard of. Rivets do indeed slip, but not immediately upon loading, and not necessarily at the same stress level. In a report released in 1924, it was shown that initial slip may occur at shear stresses anywhere from 2,500 to 10,500 psi, and continue on until 15,000 to 20,000 psi shear stresses are reached. During this “slip stage”, where friction between the plies is overcome, the rivet may be viewed as passing from a friction connection to a bearing connection, or maybe even a bending connection. Still, this stress is beyond all allowable shear stresses of the time. Figure 7 shows a typical shear stress-strain curve of one such test, with slip occurring from approximately 5,000 to 18,000 psi. Please note that the total slip occurring is less than 0.008 inches, and that the slip occurring at and below the allowable shear stresses of the various periods, say 10,000 to 13,500 psi, is perhaps only 0.003 inches. At shear stresses of 18,000 psi and above is where the riveted connection truly act as a bearing connection.

Figure 7 – Comparison of Gap Between Rivet

Shank and Base Metal Instead of performing as a bearing connection as has commonly been assumed or a friction connection that high-strength bolts are known to be, riveted connections probably act as a hybrid connection – part bearing, part friction. It is this dual characteristic, difficult to individually quantify their contributions of each component, which have led engineers to maintain the long-held simple perception of riveted connections.

STRUCTURAL RIBBED BOLTS

Structural ribbed bolts were first introduced in the 1920s and by the mid-1930s, one manufacturer had claimed that their structural ribbed bolt had already been used on numerous bridge constructions. Dardelet was a significant manufacturer of this type of fasteners, also known as interference-body bolts (Figure 8). The claimed advantage of these rivet bolts was that they were driven while cold with the ribbed tight against the fastener hole, the ribs deforming as they grind against the rim of the hole.

Figure 8 – Catalogue Photo of the Dardelet

“Rivet-Bolt”

Ribbed bolts first appear in the ASSHO highway bridge specifications in 1953, with allowable shear and bearing stresses slightly less than traditional hot rivets. Installation was secured with a wrenchtightened nut, but no claims of frictional resistdue to shank tension have been found. Ribbed bolts were undoubtedly replaced by high-strength bolts just like rivets had been.

HOW RIVETS HAVE PERFORMED

Not only has engineering folklore stated that rivets slip, it had been stated that rivets can lotime. While Waddell was still making this claim in the 1920s, documented cases are hard to find. This phenomenon is most likely due to an initial installation error rather than failure of the rivet itself. If insufficient rivet stock was placed in resulting formed head will be too small, resulting in a lack of clamping force, and a deficient shank not filling the hole and providing little contact bearing area. A possible example of poor riveting leading to failed rivets occurred on the Fink-truss modified, through girder Torii-Gawa Bridge (Japan, built 1887), where worn and loose rivets were found throughout a top flange to web area and adjacent web stiffeners (Figure 9).

Figure 9 – Wear to Shanks of Loose RivetsTorii-Gawa Bridge (Japan, 1887)

The most common occurrence of rivet failure, albeit partial failure, is the random sheared rivet head. The author’s experience with this failure is that pack rust between the plies likely produces additional tensile stresses with localized corrosion in the

Ribbed bolts first appear in the ASSHO highway bridge specifications in 1953, with allowable shear and bearing stresses slightly less than traditional hot rivets. Installation was secured with a wrench-tightened nut, but no claims of frictional resistance due to shank tension have been found. Ribbed bolts

strength bolts

Not only has engineering folklore stated that rivets slip, it had been stated that rivets can loosen over

Waddell was still making this claim in documented cases are hard to find. This

phenomenon is most likely due to an initial error rather than failure of the rivet itself.

If insufficient rivet stock was placed in the hole, the resulting formed head will be too small, resulting in a lack of clamping force, and a deficient shank not filling the hole and providing little contact bearing area. A possible example of poor riveting leading to

truss modified, Gawa Bridge (Japan, built

1887), where worn and loose rivets were found throughout a top flange to web area and adjacent

Wear to Shanks of Loose Rivets,

(Japan, 1887) The most common occurrence of rivet failure, albeit

is the random sheared rivet head. The author’s experience with this failure is that pack rust between the plies likely produces additional tensile stresses with localized corrosion in the rivet

shank (Figure 10). As discussed previously, this failure results in a localized loss in frictional resistance but possibly not bearing resistance.

Figure 10 – Sheared Rivet Head Due to Pack Rust

FATIGUE PERFORMANCE With the adoption of fatigue prone details and fatigue classifications, rivets have been designated as a Category D fatigue prone detail, resulting in a maximum allowable stress range of 7 ksi, similar to some welded details. With rivets, fatigue failure occurs with crack propagating from the rivet hole, not the rivet itself (Figure 11). Conversely, highstrength bolts are a Category B detail, and have an allowable 16 ksi stress range. With millions of rivets in tensile connections present on American briin daily service from 40 to over 100 years, there relatively so few fatigue failures of rivets

Figure 11 – Fatigue Crack Propagating From and Through Rivet

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shank (Figure 10). As discussed previously, this failure results in a localized loss in frictional

not bearing resistance.

Sheared Rivet Head

Due to Pack Rust

With the adoption of fatigue prone details and fatigue classifications, rivets have been designated as a Category D fatigue prone detail, resulting in a maximum allowable stress range of 7 ksi, similar to some welded details. With rivets, fatigue failure occurs with crack propagating from the rivet hole, not the rivet itself (Figure 11). Conversely, high-strength bolts are a Category B detail, and have an allowable 16 ksi stress range. With millions of rivets in tensile connections present on American bridges in daily service from 40 to over 100 years, why are

fatigue failures of rivets?

Fatigue Crack Propagating From

Rivet Hole

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First, the common philosophy regarding the difference between the bolts and rivets is that bolts provide a clamping force that will arrest microcracks or flaws occurring along the edge of the connections hole. With the lesser clamping force that rivets provide, lab tests performed in the 1970s and 80s indicated that riveted connections worst general representation for fatigue occurred in the Category D boundary for approximately 1,000,000 cycles (Figure 12).

Figure 12 – Compiled Fatigue Data for

Riveted Connections However, the limited testing of riveted connections out in the 2,000,000 cycle ranges show fatigue failures at and above the Category C level. Furthermore, maximum stress range of primary riveted connections often is found to be below 5 ksi, well below the stress range for Category D details at 2,000,000 cycles and beyond. Further research conducted at Lehigh University under John Fisher in 1985 concluded that “Steel connections with good clamping force and normal bearing ratios can be considered equivalent to Category C.” Later, in 2003, the newly released Manual for Condition Evaluation and Load and Resistance Factor Rating (LRFR) for Highway Bridges (2003) states quite simply: Base metal at net sections shall be evaluated upon

the requirements of Category C.

CRACKING DUE TO STRESS CORROSION Though rivet fatigue cracks may be less of a concern now, cracking is probably more prevalent due to stress corrosion caused by the combination of thinning of connecting plies and secondary bending stresses from the pack rust deformation (Figures 13 & 14).

Figure 13 – Pack Rust Between Flange Angle and Web Plate Resulting in Vertical Bowing Between Rivets (multiple spots, including at red arrow)

Figure 14 - Stress Corrosion Crack Resulting From Localized Bending From Pack Rust and Localized Section Loss PROPER RIVET REMOVAL

Steel truss bridge rehabilitations often require removal of both complete steel members and individual components. With this, numerous rivets must be removed to the chagrin of ironworkers. Unfortunately, the bridge engineering community does not yet appear to have a universally accepted procedure that is both good for the bridge, the owner and the contractor. Rivet removal by rivet hammer, first with a chisel bit to shear the rivet head off and then with a blunt bit to push the firm rivet out, is hard on the

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ironworker’s body. Because of this, contractors will advocate for burning the rivet out with a torch. Despite assurances that the base metal will not be damaged, too often this is not the case (Figure 15). Furthermore, on at least one occurrence, a design engineer permitted torch removal of rivet with the upsizing of the connection (e.g., removing a 7/8" rivet, reaming the rivet hole 1/8" larger in diameter, and fastening with a 1" bolt). Unfortunately, this procedure still resulted in unnecessary damage to the structure with no benefit to the owner.

Figure 15 – Damaged Truss Web Base Metal

During Rivet Removal Via Torch Another method available was incorporated on the Main Avenue Bridge Rehabilitation in Cleveland, Ohio. This rivet removal method involved using a proprietary cutting torch called “Slice” that would pierce the rivet with a concentrated acetylene flame. The rivet head was then sheared off with a pneumatic hammer (rivet buster), and the rivet driven out. The performance of this method is summarized as follows by the bridge engineer, Bill Beyer, who oversaw this work:

The piercing seemed to make the head and shank removal much easier. I thought that it worked very well, although I noticed that as the project progressed, the men appeared to get more careless with the piercing, and I would see holes in the remaining base material that had been damaged by the Slice rod.

Currently, the best method for rivet removal perhaps is a two-step method similar to that being performed on the current Golden Gate Bridge Seismic Retrofit. First, a drill is placed over the rivet to be removed, and the head is removed with the drill bit stopping at the base metal. Next, a smaller drill is used to remove significant portions of the shank, relieving

much of the pressure along the shank–rivet hole interface. The result is undamaged base metal and an efficient method for the ironworkers to perform the required repairs (Figure 16). To get straight to the point, the best ways to remove rivets with minimal chance of damaging the original steel do not include any torches, heat or flames. If torches are used, damage to the base metal can and eventually will occur.

Figure 16 – Drilled Out Rivets, Golden Gate Bridge Seismic Retrofit

RIVETS IN THE 21st CENTURY

Noting that there are numerous steel vehicular and railroad bridges in good condition that were built in the 1920s and earlier, it is apparent that riveted bridge connections will be around for many, many decades to come. With the endurance of riveted steel bridges, engineers will continue to need to understand how these connections work and perform. More importantly, however, there is a revival in the practice of riveting, though currently a very modest one. With the rehabilitation of historic truss bridges, historic preservation offices and engineers are increasingly looking for ways of maintaining the appearance and interpretation of these bridges. Structural rivets are still readily available, and they are still available at retail costs in the same range as high-strength bolts. The challenge is retraining engineers and contractors on the how to rivet, which has been and steadily happening over the last 10 years.

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One such example of new riveting for historic bridge restoration was performed on the Zoarville Station Bridge in Tuscarawas County (Figure 17), a rare Fink truss incorporating Phoenix columns for its primary compression members. Built in 1868, it nearly collapsed after decades of abandonment. Following a great civic and fund raising effort, the bridge was disassembled for repair. Several of the original Phoenix columns could not be reused, and these members were replicated with shop riveted connections (Figure 18). Furthermore, field connections were also riveted, resulting in a unique historic bridge preserved for future generation. New structural riveting has been performed on historic bridge rehabilitations in Michigan, Indiana, Ohio and Washington, and a historic bridge rehabilitation requiring riveted connections is currently planned in Texas. Once again, rivets are here to stay.

Figure 17 – Restored Zoarville Station Bridge

(1868), Near Bolivar, Ohio

Figure 18 – One 1868 Iron Rivet (Left) & One

2007 Steel Rivet (Right)

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ACKNOWLEDGEMENTS

Vern Mesler, VJM Metal Craftsman, LLC Doug Lockhart, Blacksmith,

Maker of the Hand Forge, Logan, Ohio Phil Fish, Wisconsin DOT (retired) Bill Beyer, HNTB, Kansas City, Missouri Tony Hatem, HNTB,

Golden Gate Bridge Seismic Rehabilitation William C. Barrow, Cleveland State University

Special Collections David A. Simmons, Ohio Historical Society

REFERENCES

“ ‘I THOUGHT I WAS DEAD’, Survivors tell of horror as bridge collapses”, The Cleveland Plain Dealer, Tuesday, August 7, 2007, p. A6. Riveted Joints, A critical Review of the Literature Covering Their Development, with Bibliography and Abstracts of the Most Important Articles, The American Society of Mechanical Engineers, 1945. Bibliography on Bolted and Riveted Joints, American Society of Civil Engineers, 1967. Ketchum, Milo S., Design of Highway Bridges, McGraw-Hill, Inc., New York, 1920, pp. 469-75. Blakelock, David H., Slip of Riveted Joints in Single and Repetitive Loading, Engineering News-Record, Vol. 92, June 5, 1924, pp. 972-3. Landon, R.D., Comparative Strength of Short and Long Rivets, A Thesis Presented to the Faculty of the College of Engineering University of Cincinnati, May 12, 1927. Defects in Railway Bridges and Their Remedies, Proceedings of the Symposium on the Failure and Defects of Bridge and Structures, Japan Society for the Promotion of Science, Tokyo, Japan, December 1958, p. 27-29. Zhou, Y.E., Assessing Remaining Fatigue Life of Existing Riveted Steel Bridges, Recent Developments in Bridge Engineering, Proceedings of the Second New York City Bridge Conference, 2003, p. 198-200. Wilson, Wilbur M. and Thomas, Frank P., Fatigue Tests of Riveted Joints, the Engineering Experiment Station, University of Illinois, May 1938.

Shedd, Thomas Clark, Structural Design in Steel, John Wiley & Sons, New York, 1934. pp. 270-2. Field Manual for Bridge Inspectors, Maryland State Roads Commission, 1932, pp. 75-80. Out, Johannes M.M. and Fisher, John W., Fatigue Strength of Weathered and Deteriorated Riveted Members, Fritz Engineering Laboratory, Lehigh University, October 1984. Davis, R.E., Woodruff, G.B. and Davis, H.E., Tension Tests of Large Riveted Joints, Engineering News-Record, Vol. 122, February 16, 1939, pp. 220-221. Manual for Condition Evaluation and Load and Resistance Factor Rating (LRFR) for Highway Bridges, ASSHTO, October 2003, pp. 7-1.

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Common signs of defective rivets include the following: 1. Loose rivets. 2. Rivets where either head is not in full contact with the plate. 3. Burned rivets, caused by overheating and possibly brittle (See Figure 2). 4. Split head rivet, caused by overheating and driven too cold. 5. Soldier cap rivet, caused by excessive length of rivet, giving a lip around the

head of the rivet (Figure A-1). 6. Rivet with unfilled head, caused by too short shank or driven too cold (Figure A-2). 7. Spherical head rivet, caused by being driven too cold (Figure A-2). 8. Rivet with head not concentric with the axis of the rivet. 9. Rivet being driven when plates are not drawn up properly and metal and metal is

wedged between plates. 10. Caulked rivets. These are loose rivets that may have been caulked so to appear and

sound tight. This is done by tilting the pneumatic hammer or snap at an angle when driven or using a cold chisel to caulk down the lip of a rivet head.

Any of the above defects could result in the removal of the defective rivet by cutting or drilling. However, the inspector may permit a defective rivet to remain if its remove may loosen adjacent rivets.

Figure A-1 – Soldier Cap Head and Figure A-2 – Unfilled Rivet Heads Unsymmetrical Head

Appendix A – Common Characteristics of Defective Rivets

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Year Reference Allowable Stress per Rivet (psi)

Shear Bearing

1878 Practical Treatise on the Construction of Iron Highway, 2nd Ed., Alfred P. Boller -- 10,000

1888 The Designing of Ordinary Highway Bridges, 4th Ed., J. A. L. Waddell

Shear was not a factor as rivets were considered to fail in bending.

12,000 (Class A Bridge) 15,000 (Class B & C Bridges)

1900 Southern Pacific Railroad (Cooper Specifications) 9,000 16,000

1902 Roofs and Bridges, Jacoby & Merriman 12,000 24,000 1903 De Pontibus, 2nd Ed., J. A. L. Waddell 10,000 (Shop Rivets)

8,000 (Field Rivets) 20,000 (Shop Rivets) 16,000 (Field Rivets)

1909 General Specifications for Steel Highway Bridges & Electric and Street Railway Viaducts, Bernt Berger

12,000 (Shop Rivets) 9,000 (Floor System, Shop) (Reduce 1/3 for field rivets)

18,000 (Shop Rivets) 14,400 (Floor System, Shop) (Reduce 1/3 for field rivets)

1916 Bridge Engineering, J. A. L. Waddell 10,000 (Shop Rivets) 8,000 (Field Rivets)

20,000 (Shop Rivets) 16,000 (Field Rivets)

1920 General Specifications for Steel Railway Bridges

12,000 (Shop Rivets) 9,000 (Field Rivets)

24,000 (Shop Rivets) 18,000 (Field Rivets)

1920 The Design of Highway Bridges, Milo S. Ketchum

12,000 (Shop Rivets) 10,000 (Field Rivets)

24,000 (Shop Rivets) 20,000 (Field Rivets)

1934 Structural Design in Steel, Thomas Clark Shedd

11,200 (Hand Driven) 13,500 (Power Driven)

22,400 (Hand Driven) 27,000 (Power Driven)

1935 Standard Specifications for Highway Bridges, 2nd Ed., The American Association of State Highway Officials

12,000 (Shop Rivets) 10,000 (Field Rivets)

24,000 (Shop Rivets) 20,000 (Field Rivets)

1953 Standard Specifications for Highway Bridges, 6th Ed., The American Association of State Highway Officials

20,000 (H.S. Rivets) 13,500 (Power Driven) 11,000 (Ribbed Bolts)

40,000 (H.S. Rivets) 27,000 (Power Driven) 20,000 (Ribbed Bolts)

2009 Standard Specifications for Highway Bridges, The American Association of State Highway Transportation Officials

20,000 (High Strength Rivets)

40,000 (High Strength Rivets)

Note: Waddell specified the same allowable stresses that he professed in De Pontibus (1903 edition) and

Bridge Engineering (1916).

Appendix B – Survey of Rivet Allowable Stresses