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 ...
126Keating (1984) stated that the splice plate detail was an adequate repair since thefatigue lives for these connections were comparable to the steel components. This wasbecause the crack growth was “arrested by the wrought iron stringers.” The crack wouldbegin propagating through the thickness of the wrought iron eyebar and then turn andpropagate along the length of the eyebar (in the direction of rolling). The stress beingapplied to the eyebar with the splice plate was then parallel to the crack growth, makingcrack propagation minimal and the fatigue life of the wrought iron higher. Even thoughthe fatigue life of the splice plate repair was very long, the pattern of the crack growthcreates the need to check for any type of block shear failure that might occur.The splice plate repair may be an adequate repair, but for aesthetic reasons, abetter method to shorten a loose eyebar is two remove a section from the eyebar and thendirectly weld the two pieces together using the welding procedure tested in this study.Tensile coupons that included a full-penetration butt welded joints were evaluated. It wasdetermined that weld detail and process utilized in preparing the tensile testing couponsprovided sufficient overall performance. The welded wrought iron tensile strength wasnot affected, but the ductility was slightly lower.It is recommended that a similar procedure and detail be utilized when shorteninga wrought iron eyebar. The welding procedure utilized in this study is outlined in detailin Appendix D. It is also recommended that, if possible, a welding procedurespecification (WPS) be developed and a sample of the repaired material be tested toensure proper performance when using the WPS.It is important to recognize the lack of ductility that may exist in a shortenedmember. Although, elastic shortening of a member will not typically reduce the ductilityof a member, additional shortening that induces plastic strain will reduce the ductility.This is due to the amount of overall plastic strain that is lost during the life of the memberwhen it is elongated. This phenomenon was prevalent during testing that was completedduring this study when comparing the wrought iron that had experienced visual damage
127to wrought iron that had not. The wrought iron that experienced significant damageexhibited a much lower percent elongation and, therefore, was much less ductile.5.7 Investigation and Repair of Damaged and Bent MembersMany existing historic iron truss bridges have been damaged by vehicular trafficor severe storms. In these bridges, there are typically a number of members that havebeen bent or twisted to the point where the member either fails or its strength iscompromised. In extreme cases, the bridge may collapse due to severe damage. Forexample, Figure 5.13 shows a number of members from the Bell Ford Bridge after it hadcollapsed. As seen in the photograph, the members are severely misshaped and damaged.In the testing that was completed for this study, some of the damaged Bell FordBridge members were machined into tensile testing coupons and then tested to determinetheir strength. Of the damaged members, some had been heat straightened and one hadbeen mechanically straightened. The results from the heat straightened samples weresuperior to the results of the mechanically straightened specimen. The heat straightenedsamples were more ductile and had adequate tensile strength, while the mechanicallystraightened specimen was less ductile and failed at a lower tensile stress.The mechanically straightened tensile coupon had poor percent elongation resultsand a lower ductility because repeated straightening of the specimen without heatdepleted the amount of plastic strain that was available in the material. When using heatto straighten a wrought iron member, the plastic strain in the material is not affected.Therefore, it is recommended that when straightening any damaged wrought iron bridgemember, heat should be added.Figure 5.14 illustrates the method that was used to heat straighten the eyebarsfrom the Bell Ford Bridge. In this method, the wrought iron is first heated slowly in a
- Page 96 and 97: 76Figure 3.35 Front View of Eyebar
- Page 98 and 99: 78strength from the existence of pe
- Page 100 and 101: 80The carbon content present in the
- Page 102 and 103: 82value may not be very accurate bu
- Page 104 and 105: 84strengths was found to be 29,940
- Page 106 and 107: 86wrought iron bars were investigat
- Page 108 and 109: 88stresses are induced. These perma
- Page 110 and 111: 90toughness the material. The test
- Page 112 and 113: 92From the finite element analysis,
- Page 114 and 115: 94Table 4.1 Chemical Analysis of Ey
- Page 116 and 117: 96Table 4.3 Tensile Coupon Test Res
- Page 118 and 119: 98Table 4.5 Charpy Impact Test Resu
- Page 120 and 121: 100Table 4.7 Comparison of Strain G
- Page 122 and 123: 102Figure 4.1 Typical Micrograph of
- Page 124 and 125: 104Figure 4.5 Fracture Surface of D
- Page 126 and 127: 106Comparison of Tensile Strengthfo
- Page 128 and 129: 108Combined Wrought Iron Bar Histor
- Page 130 and 131: 110Figure 4.17 Macrograph of Weld u
- Page 132 and 133: 112Figure 4.21 Cleavage Fracture of
- Page 134 and 135: Figure 4.25 Elongation of Hole in E
- Page 136 and 137: 116signs on or near the bridge that
- Page 138 and 139: 118testing of historic wrought iron
- Page 140 and 141: 120so that they would act in symmet
- Page 142 and 143: 122The reasons for the differences
- Page 144 and 145: 124The second corrosion pattern mod
- Page 148 and 149: 128charcoal fire until it is red ho
- Page 150 and 151: 130Figure 5.3 Picture of Bottom Cho
- Page 152 and 153: 132Figure 5.7 Using Force After Usi
- Page 154 and 155: 134Figure 5.11 Reassembling a Pin C
- Page 156 and 157: 1366. SUMMARY, CONCLUSIONS AND IMPL
- Page 158 and 159: 138rectangular in shape. These eyeb
- Page 160 and 161: 140were joined together with a full
- Page 162 and 163: 1424. The Charpy impact energy of t
- Page 164 and 165: 144connections are unsymmetrical, i
- Page 166 and 167: 146LIST OF REFERENCESAASHTO (1998).
- Page 168 and 169: 148Hodgkinson, Eaton (1840). Experi
- Page 170 and 171: 150Appendix A. Data Collected From
- Page 172 and 173: 152Table A.1 Wrought Iron Bar Tensi
- Page 174 and 175: 154Table A.1 (continued) Wrought Ir
- Page 176 and 177: 156Table A.2 (continued) Wrought Ir
- Page 178 and 179: 158Table A.3 Wrought Iron Angle Ten
- Page 180 and 181: 160Table A.4 (continued) Summary of
- Page 182 and 183: 162Table A.4 (continued) Summary of
- Page 184 and 185: 164Table A.5 (continued) Detailed I
- Page 186 and 187: 166Table A.5 (continued) Detailed I
- Page 188 and 189: 168Table A.5 (continued) Detailed I
- Page 190 and 191: 170Table A.5 (continued) Detailed I
- Page 192 and 193: 172Table A.5 (continued) Detailed I
- Page 194 and 195: 174Table A.5 (continued) Detailed I
126Keating (1984) stated that the splice plate detail was an adequate repair since thefatigue lives for these connections were comparable to the steel components. This wasbecause the crack growth was “arrested by the wrought iron stringers.” The crack wouldbegin propagating through the thickness <strong>of</strong> the wrought iron eyebar <strong>and</strong> then turn <strong>and</strong>propagate along the length <strong>of</strong> the eyebar (in the direction <strong>of</strong> rolling). The stress beingapplied to the eyebar with the splice plate was then parallel to the crack growth, makingcrack propagation minimal <strong>and</strong> the fatigue life <strong>of</strong> the wrought iron higher. Even thoughthe fatigue life <strong>of</strong> the splice plate repair was very long, the pattern <strong>of</strong> the crack growthcreates the need to check for any type <strong>of</strong> block shear failure that might occur.The splice plate repair may be an adequate repair, but for aesthetic reasons, abetter method to shorten a loose eyebar is two remove a section from the eyebar <strong>and</strong> thendirectly weld the two pieces together using the welding procedure tested in this study.Tensile coupons that included a full-penetration butt welded joints were evaluated. It wasdetermined that weld detail <strong>and</strong> process utilized in preparing the tensile testing couponsprovided sufficient overall performance. The welded wrought iron tensile strength wasnot affected, but the ductility was slightly lower.It is recommended that a similar procedure <strong>and</strong> detail be utilized when shorteninga wrought iron eyebar. The welding procedure utilized in this study is outlined in detailin Appendix D. It is also recommended that, if possible, a welding procedurespecification (WPS) be developed <strong>and</strong> a sample <strong>of</strong> the repaired material be tested toensure proper performance when using the WPS.It is important to recognize the lack <strong>of</strong> ductility that may exist in a shortenedmember. Although, elastic shortening <strong>of</strong> a member will not typically reduce the ductility<strong>of</strong> a member, additional shortening that induces plastic strain will reduce the ductility.This is due to the amount <strong>of</strong> overall plastic strain that is lost during the life <strong>of</strong> the memberwhen it is elongated. This phenomenon was prevalent during testing that was completedduring this study when comparing the wrought iron that had experienced visual damage
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