Evaluation and Repair of Wrought Iron and - Purdue e-Pubs ...
Evaluation and Repair of Wrought Iron and - Purdue e-Pubs ... Evaluation and Repair of Wrought Iron and - Purdue e-Pubs ...
22The practice of restoring historic bridges for pedestrian use is very commonthrough out the country. This practice is viewed by many as an effective compromisebetween keeping the historical validity of a bridge and keeping it structurally safe to use.Francis E. Griggs, Jr is the director of Historic Bridge Programs at Clough, Harbour &Associates LLP. He has rehabilitated and reconstructed many historic bridges in thismanner. One bridge in particular is an 1864 Moseley Wrought Iron Bridge that wasmoved to the Campus of Merrimack College in N. Andover, MA (Griggs, 1997).2.3.2 Carroll Road Bridge, Maryland, 1879The Carroll Road Bridge was a wrought iron Pratt through bridge that spanned 92feet and was constructed in Baltimore County, Maryland in 1879. This bridge consistedof two wrought iron trusses with a wooden deck supported by stringers. The upper andlower chords of the trusses are made up of eyebars with pin connections. Pin connectionsare a typical type connection found in many historical truss type bridges.The Baltimore County Department of Public Works decided to rehabilitate theCarroll Road Bridge in order to preserve the historic character and upgrade the live loadcapacity of the bridge to modern vehicle standards. This preservation project is explainedin the paper Upgrading and Recycling of Pin-Connected Truss Bridge by PinReplacement by Shahin Taavoni (1994).In the initial phase of the study, a visual inspection of the bridge was completed.Also material shavings where taken from the bridge to determine the type of metal in thebridge. Chemical analysis results determined that the material was wrought iron. Duringthe visual bridge investigation it was found that the pin connections on the bridge werenot acting symmetrically.
23The lack in symmetry found at the pin connections was a result of dynamic effectsof the live load and past repairs. Corrosion and fatigue could also lead to movement inthe eyebars but was not considered to be an issue for this bridge. An analysis of the lackof symmetry and resultant effects determined that the pins needed to be replaced with ahigher strength material and the eyebars moved back to a symmetrical position. Thiswould ensure that the pins would not experience an unsafe amount of shear, that theeyebars would all carry the load equally.The rehabilitation of the bridge consisted of taking apart the trusses andreassembling them with higher strength pins. Members added during past repairs werealso removed. Many of these past repairs involved the addition of a third component in aprevious two component member. To sustain the higher load the third component wouldbe removed and the two component member would be replaced with a stronger twocomponent material. Finally, spacers were added to the pin connection to ensure thatsymmetry would be maintained in the future.Rehabilitation using the pin replacement method turned out to be efficient,expeditious and economical according to Taavoni. It could also be easily adapted tomany other historic truss bridges that have similar pin connections.2.3.3 Chestnut Ford Bridge and Hubby Bridge, Iowa, circa 1900Construction on the Des Moines River in Iowa lead to the removal of five iron pinconnected truss bridges in that area. The first of these bridges, the Chestnut Ford Bridge,was subjected to service load testing, and supplementary static and fatigue tests of tensioneyebars taken from the bridge. The second bridge, the Hubby Bridge, was also subjectedto service load testing and eyebar laboratory testing, but also went through an ultimateload test. The paper Service Load and Fatigue Tests on Truss Bridges by Hotten A.
- Page 1 and 2: Purdue UniversityPurdue e-PubsJTRP
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- Page 6 and 7: epairing a bent wrought iron tensio
- Page 8 and 9: vPageCHAPTER 3TEST PROCEDURES FOR M
- Page 10 and 11: ixLIST OF FIGURESFigurePageFigure 1
- Page 12 and 13: xiFigurePageFigure 3.30 Top View of
- Page 14 and 15: xiiiFigurePageFigure 5.12 Typical T
- Page 16 and 17: xvAppendix FigurePageFigure D.7 Ini
- Page 18 and 19: viiiAppendix TablePageTable A.5 Det
- Page 20 and 21: iiiThe authors would also like to t
- Page 22 and 23: 2but also what material properties
- Page 24 and 25: 4microstructure of the metal. The c
- Page 26 and 27: 62. LITERATURE SEARCHBefore experim
- Page 28 and 29: 8imperfections, the performance of
- Page 30 and 31: 10wrought iron. Adding the slag aft
- Page 32 and 33: 12method for manufacturing wrought
- Page 34 and 35: 14patents for their process and tra
- Page 36 and 37: 16This method of testing of structu
- Page 38 and 39: 18plot of this percent elongation d
- Page 40 and 41: 20significant variation in the perc
- Page 44 and 45: 24Elleby, Wallace W. Sanders, F. Wa
- Page 46 and 47: 26From all the surveys that were di
- Page 48 and 49: 28Table 2.1 Average Ultimate Streng
- Page 50 and 51: 30Figure 2.3 Wrought Iron “Sponge
- Page 52 and 53: 32Histogram of Kirkaldy Wrought Iro
- Page 54 and 55: 34Percent Occurance in Range - %45.
- Page 56 and 57: 3660Combined Wrought Iron BarsTensi
- Page 58 and 59: 38The Bell Ford Bridge consisted of
- Page 60 and 61: 40Two. These samples were taken fro
- Page 62 and 63: 42specimens were of constant cross
- Page 64 and 65: 44Along with rectangular tensile co
- Page 66 and 67: 46After the initial test loading wa
- Page 68 and 69: 483.6 Fatigue TestingTo develop a b
- Page 70 and 71: 50The final specimen category consi
- Page 72 and 73: 52This analysis was completed using
- Page 74 and 75: 54After the initial test was comple
- Page 76 and 77: 56completed, but before the surface
- Page 78 and 79: 58readings, load cell readings and
- Page 80 and 81: 60Figure 3.3 Donated Eyebars 4 and
- Page 82 and 83: 62Figure 3.7 Heated Areas in Blue o
- Page 84 and 85: 64Figure 3.11 Detail Used in Groove
- Page 86 and 87: 66900080007000y = 27.153xR 2 = 0.99
- Page 88 and 89: 68Figure 3.19 Charpy Impact Testing
- Page 90 and 91: 70Figure 3.23 Eyebar Connection in
23The lack in symmetry found at the pin connections was a result <strong>of</strong> dynamic effects<strong>of</strong> the live load <strong>and</strong> past repairs. Corrosion <strong>and</strong> fatigue could also lead to movement inthe eyebars but was not considered to be an issue for this bridge. An analysis <strong>of</strong> the lack<strong>of</strong> symmetry <strong>and</strong> resultant effects determined that the pins needed to be replaced with ahigher strength material <strong>and</strong> the eyebars moved back to a symmetrical position. Thiswould ensure that the pins would not experience an unsafe amount <strong>of</strong> shear, that theeyebars would all carry the load equally.The rehabilitation <strong>of</strong> the bridge consisted <strong>of</strong> taking apart the trusses <strong>and</strong>reassembling them with higher strength pins. Members added during past repairs werealso removed. Many <strong>of</strong> these past repairs involved the addition <strong>of</strong> a third component in aprevious two component member. To sustain the higher load the third component wouldbe removed <strong>and</strong> the two component member would be replaced with a stronger twocomponent material. Finally, spacers were added to the pin connection to ensure thatsymmetry would be maintained in the future.Rehabilitation using the pin replacement method turned out to be efficient,expeditious <strong>and</strong> economical according to Taavoni. It could also be easily adapted tomany other historic truss bridges that have similar pin connections.2.3.3 Chestnut Ford Bridge <strong>and</strong> Hubby Bridge, Iowa, circa 1900Construction on the Des Moines River in Iowa lead to the removal <strong>of</strong> five iron pinconnected truss bridges in that area. The first <strong>of</strong> these bridges, the Chestnut Ford Bridge,was subjected to service load testing, <strong>and</strong> supplementary static <strong>and</strong> fatigue tests <strong>of</strong> tensioneyebars taken from the bridge. The second bridge, the Hubby Bridge, was also subjectedto service load testing <strong>and</strong> eyebar laboratory testing, but also went through an ultimateload test. The paper Service Load <strong>and</strong> Fatigue Tests on Truss Bridges by Hotten A.
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