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    CROSTI_IABMAS-ITALY CROSTI_IABMAS-ITALY Presentation Transcript

    • MILANO, ITALY, OCTOBER 14, 2013 IL COLLASSO DEL PONTE I-35W A MINNEAPOLIS COME ESEMPIO DI INGEGNERIA FORENSE Chiara Crosti “Sapienza” University of Rome, chiara.crosti@uniroma1.it
    • CASE STUDY THE FACT: COLLAPSE OF THE BRIDGE ON I 35-W MINNESOTA, AUGUST 1ST 2007 The I-35W Mississippi River Bridge (officially known as Bridge 9340) was an eight-lane, deck truss bridge, designed by the engineering consulting firm of Sverdrup & Parcel and Associates, the design plans were approved by the Minnesota Department of Transportation (Mn DOT) on 1965 and opened to traffic on 1967. http://www.dot.state.mn.us/i35wbridge/ntsb/finalreport.pdf chiara.crosti@uniroma1.it
    • CASE STUDY • • • The deck truss comprised in two parallel Warren trusses (east and west) with verticals. The east and west main trusses were spaced 22 m apart and were connected by 27 transverse welded floor trusses spaced 11.6 m on centers and by two floor beams at the north and south ends. Steel gusset plates were used on all the 112 connections of the two main trusses. All nodes had two gusset plates on either side of the connection. http://www.dot.state.mn.us/i35wbridge/ntsb/finalreport.pdf chiara.crosti@uniroma1.it
    • CASE STUDY After this tragedy, the Federal Highway Administration (FHWA) focused its attention on all the 465 steel deck truss bridges present in the National Bridge Inventory [NTSB, 2008]. “The term “fracture critical” indicates that if one main component of a bridge fails, the entire structure could collapse. Therefore, a fracture critical bridge is a steel structure that is designed with little or no load path redundancy. Load path redundancy is a characteristic of the design that allows the bridge to redistribute load to other structural members on the bridge if any one member loses capacity. “ chiara.crosti@uniroma1.it
    • FORENSIC INVESTIGATION National Transportation Safety Board, NTSB, 2008 “Collapse of I-35 W Highway Bridge, Minneapolis, Minnesota, August 1, 2007” Accident Report, NTSB/HAR 08/03 PB 2008916213, Washington D.C. 20594. chiara.crosti@uniroma1.it
    • FORENSIC INVESTIGATION 5/67 THE MAIN CAUSE: The primary cause was the under-sized gusset plates, at 0.5 inches (13 mm) thick; U10-W [*] National Transportation Safety Board, “Collapse of I-35 W Highway Bridge, Minneapolis, Minnesota, August 1, 2007” Accident Report, NTSB/HAR 08/03 PB 2008-916213, Washington D.C. 20594. 2008. chiara.crosti@uniroma1.it
    • FORENSIC INVESTIGATION FINITE ELEMENT MODEL FOR OUTSIDE WEST GUSSET PLATE AT U10W Stress contours for outside (west) gusset plate at U10W at time of bridge opening in 1967 Yield stress of 51.5 ksi 1977-1998 South North [*] National Transportation Safety Board, “Collapse of I-35 W Highway Bridge, Minneapolis, Minnesota, August 1, 2007” Accident Report, NTSB/HAR 08/03 PB 2008-916213, Washington D.C. 20594. 2008. chiara.crosti@uniroma1.it
    • FORENSIC INVESTIGATION 6/67 THE ADDITIONARY CAUSE: 2 inches (51 mm) of concrete were added to the road surface over the years, increasing the dead load by 20%; 1977, Renovation: Increased Deck Thickness 1998, Renovation: Median Barrier, Traffic Railings, and Anti-Icing System 2007, Repair and Renovation: Repaving [*] National Transportation Safety Board, “Collapse of I-35 W Highway Bridge, Minneapolis, Minnesota, August 1, 2007” Accident Report, NTSB/HAR 08/03 PB 2008-916213, Washington D.C. 20594. 2008. chiara.crosti@uniroma1.it
    • FORENSIC INVESTIGATION FINITE ELEMENT MODEL FOR OUTSIDE WEST GUSSET PLATE AT U10W Stress contours for outside (west) gusset plate at U10W after 1977 and 1998 renovation projects Yield stress of 51.5 ksi South North [*] National Transportation Safety Board, “Collapse of I-35 W Highway Bridge, Minneapolis, Minnesota, August 1, 2007” Accident Report, NTSB/HAR 08/03 PB 2008-916213, Washington D.C. 20594. 2008. chiara.crosti@uniroma1.it
    • FORENSIC INVESTIGATION 7/67 THE ADDITIONARY CAUSE: The extraordinary weight of construction equipment and material resting on the bridge just above its weakest point at the time of the collapse [*] North South U10-W 184 380 lbf (820 kN) of gravel 198 820 lbf (884 kN) of sand 195 535 lbf (870 kN) of parked construction vehicles and personnel [*] National Transportation Safety Board, “Collapse of I-35 W Highway Bridge, Minneapolis, Minnesota, August 1, 2007” Accident Report, NTSB/HAR 08/03 PB 2008-916213, Washington D.C. 20594. 2008. chiara.crosti@uniroma1.it
    • FORENSIC INVESTIGATION 7/67 THE ADDITIONARY CAUSE: The extraordinary weight of construction equipment and material resting on the bridge just above its weakest point at the time of the collapse [*] North South U10-W 184 380 lbf (820 kN) of gravel 198 820 lbf (884 kN) of sand 195 535 lbf (870 kN) of parked construction vehicles and personnel Pier 6 [*] National Transportation Safety Board, “Collapse of I-35 W Highway Bridge, Minneapolis, Minnesota, August 1, 2007” Accident Report, NTSB/HAR 08/03 PB 2008-916213, Washington D.C. 20594. 2008. chiara.crosti@uniroma1.it
    • FORENSIC INVESTIGATION FINITE ELEMENT MODEL FOR OUTSIDE WEST GUSSET PLATE AT U10W Stress contours for outside (west) gusset plate at U10W on August 1, 2007 Yield stress of 51.5 ksi South North [*] National Transportation Safety Board, “Collapse of I-35 W Highway Bridge, Minneapolis, Minnesota, August 1, 2007” Accident Report, NTSB/HAR 08/03 PB 2008-916213, Washington D.C. 20594. 2008. chiara.crosti@uniroma1.it
    • FORENSIC INVESTIGATION FINITE ELEMENT MODEL FOR OUTSIDE WEST GUSSET PLATE AT U10W Stress contours for outside (west) gusset plate at U10W on August 1, 2007 Yield stress of 51.5 ksi [*] National Transportation Safety Board, “Collapse of I-35 W Highway Bridge, Minneapolis, Minnesota, August 1, 2007” Accident Report, NTSB/HAR 08/03 PB 2008-916213, Washington D.C. 20594. 2008. chiara.crosti@uniroma1.it
    • BRIDGE COLLAPSE 12/44 8/31 chiara.crosti@uniroma1.it
    • BRIDGE COLLAPSE 13/44 8/31 chiara.crosti@uniroma1.it
    • BRIDGE COLLAPSE 14/44 8/31 chiara.crosti@uniroma1.it
    • BRIDGE COLLAPSE 15/44 8/31 chiara.crosti@uniroma1.it
    • BRIDGE COLLAPSE 16/44 8/31 chiara.crosti@uniroma1.it
    • BRIDGE COLLAPSE 17/44 8/31 chiara.crosti@uniroma1.it
    • BRIDGE COLLAPSE 18/44 8/31 chiara.crosti@uniroma1.it
    • BRIDGE COLLAPSE 19/44 8/31 chiara.crosti@uniroma1.it
    • BRIDGE COLLAPSE 20/44 8/31 chiara.crosti@uniroma1.it
    • BRIDGE COLLAPSE 21/44 8/31 chiara.crosti@uniroma1.it
    • BRIDGE COLLAPSE 21/44 8/31 chiara.crosti@uniroma1.it
    • BRIDGE COLLAPSE 22/44 8/31 chiara.crosti@uniroma1.it
    • BRIDGE COLLAPSE 23/44 8/31 chiara.crosti@uniroma1.it
    • BRIDGE COLLAPSE 24/44 8/31 chiara.crosti@uniroma1.it
    • BRIDGE COLLAPSE 25/44 /31 chiara.crosti@uniroma1.it
    • FORENSIC INVESTIGATION INSPECTION REPORTING FOR I-35W BRIDGE, 1983-2007 chiara.crosti@uniroma1.it
    • FORENSIC INVESTIGATION INSPECTION REPORTING FOR I-35W BRIDGE, 2006 GUSSET PLATE??? chiara.crosti@uniroma1.it
    • FORENSIC INVESTIGATION BOWED GUSSET PLATE AT NODE U10 chiara.crosti@uniroma1.it
    • FORENSIC INVESTIGATION INSPECTION REPORTING FOR I-35W BRIDGE chiara.crosti@uniroma1.it
    • FORENSIC INVESTIGATION 26/67 FHWA GUIDELINES, (2009) RESISTANCE OF GUSSET PLATES: GUSSET PLATES SUBJECT TO SHEAR GUSSET PLATES IN COMPRESSION GUSSET PLATES IN TENSION RESISTANCE OF FASTENERS SHEAR RESISTANCE OF FASTENERS PLATE BEARING RESISTANCE AT FASTENERS http://bridges.transportation.org/Documents/FHWA-IF-09 014LoadRatingGuidanceandExamplesforGussetsFebruary2009rev3.pdf chiara.crosti@uniroma1.it
    • FORENSIC INVESTIGATION 40/67 CRITICAL REVIEW OF THE FHWA GUIDELINES: • • • Stiffness of framing members, that increase the ultimate compression capacity of the gusset plate; Influence of the initial imperfections, that decrease the ultimate compression capacity of the gusset plate; Edge buckling vs. Gusset plates buckling, from that the importance of making consideration not only on the length of the free edge, but also length of equivalent column is important for buckling For LRFR and λ ≤ 2.25 (assumes δ ≤ L /1500) Gusset Plates What if δ > L /1500) ? Framing member stiffness chiara.crosti@uniroma1.it
    • NIST PHYSICAL INFRASTRUCTURE PROGRAM NIST Physical Infrastructure Program chiara.crosti@uniroma1.it
    • NIST PHYSICAL INFRASTRUCTURE PROGRAM FHWA SETUP** [**] Iadicola M., Ocel J., Zobel R., “Quantitative Evaluation of Digital Image Correlation for Large-Scale Gusset Plate Experiments”, IABMAS2012, Stresa, Lake Maggiore, Italy, July 8-12. chiara.crosti@uniroma1.it
    • NIST PHYSICAL INFRASTRUCTURE PROGRAM FHWA TEST, VIRGINIA (2010) chiara.crosti@uniroma1.it
    • SIMPLIFIED CONNECTION MODEL 7/28 FHWA, 2009 Hand calculation Advanced computing modeling chiara.crosti@uniroma1.it
    • MODELING OF GUSSET PLATE CONNECTIONS 45/6 7 SUB-STRUCTURING ANALYSIS – SIMPLIFIED LINEAR CONNECTION MODEL N. Nodes: 28330 n. Dof : 169980 n. Elements S4R and S3R: 27670 Connection element 1 Connection element 3 n. connection elements: 5 Each connection element has a 6x6 stiffness matrix Connection element 4 chiara.crosti@uniroma1.it
    • 3D MODEL OF THE I35-W BRIDGE 3D FINITE ELEMENT MODEL U10 W South North Nodes: 1172 Beam elements: 1849 ALL RIGID JOINT ALL RIGID JOINT + 1 SEMI-RIGID JOINT chiara.crosti@uniroma1.it
    • NONLINEAR ANALYSES RESULTS 56/67 18/28 NONLINEAR ANALYSES RESULTS South North Node at midspan 7 6 RIGID JOINTS 4 3 2 1 0 -0.7 -0.6 -0.5 -0.4 -0.3 Dz (m) chiara.crosti@uniroma1.it -0.2 -0.1 0.0 Load Factor 5 SEMI-RIGID JOINT
    • NONLINEAR ANALYSES RESULTS 57/63 19/28 NONLINEAR ANALYSES RESULTS Compression Tension 1.8 1.6 1.4 1.2 1.0 0.8 0.4 0.2 -2.0E+07 -1.0E+07 0.0E+00 1.0E+07 Axial Forces (N) 2.0E+07 Load Factor 0.6 0.0 3.0E+07 What is important to underline is not onlyCONNECTION 2 the possibility to catch the collapse due to the failure of CONNECTION 1 CONNECTION 3 CONNECTION 4 CONNECTION 5 AXIAL CAPACITY CONNECTION 1 the connection, but moreover to classify the cause of the collapse which, in this case, happened AXIAL CAPACITY CONNECTION 2 AXIAL CAPACITY CONNECTION 3 AXIAL CAPACITY CONNECTION 4 because of the achievement for one of the connection elements of the maximum capacity in AXIAL CAPACITY CONNECTION 5 compression. chiara.crosti@uniroma1.it
    • CONCLUSION 62/67 CONCLUSIVE CONSIDERATIONS Deformed shape (scale displacement of 10) at the ultimate load (Pu) of 1.2+07 N Connection Load Tension or member ratio compression 1 0.28 Compression 2 0.56 Tension 3 1.00 Compression 4 0.02 Tension 5 0.41 Tension What is important to underline is not only the possibility to catch the collapse due to the failure of the connection, but moreover to classify the cause of the collapse which, in this case, happened because of the achievement for one of the connection elements of the maximum capacity in compression. chiara.crosti@uniroma1.it
    • CONCLUSION FURTHER DEVELOPMENTS I-35W Bridge was subjected constantly to inspection to assess its safety but even with that people in charge did not notice that the bridge was about to fail. A future work could be to develop parametric study on some particular shapes of gusset plates in order to identify some “critical” points where the monitoring of the out-plane displacements, could give to the owners of the bridges a warning of what it is happening in the connection. An idea of monitoring could have been done with a technique of monitoring developed by NIST who focuses its research on two areas of structural health monitoring: •development of non-destructive techniques; and •analysis for determining the degraded condition of infrastructural components and their subcomponents. •Results from monitoring ** •FEA results •FHWA test [**] Iadicola M., Ocel J., Zobel R., “Quantitative Evaluation of Digital Image Correlation for Large-Scale Gusset Plate Experiments”, IABMAS2012, Stresa, Lake Maggiore, Italy, July 8-12. chiara.crosti@uniroma1.it chiara.crosti@uniroma1.it
    • CONCLUSION [**] Iadicola M., Ocel J., Zobel R., “Quantitative Evaluation of Digital Image Correlation for Large-Scale Gusset Plate Experiments”, IABMAS2012, Stresa, Lake Maggiore, Italy, July 8-12. chiara.crosti@uniroma1.it
    • CONCLUSION I-35W SAINT ANTHONY FALLS BRIDGE (September 2008) There are 323 sensors that regularly measure bridge conditions such as deck movement, stress, and temperature chiara.crosti@uniroma1.it
    • CONCLUSION ACKNOWLEDGMENT The author would like to acknowledge: •Professor Franco Bontempi and his team, www.francobontempi.org, for the support and the help, •the Metallurgy division of the National Institute of Standard and Technology (NIST) in particular Dr. Dat Duthinh for the support and the help, •Eng. Piergiorgio Perin for providing the use of the finite element code Straus, and •NTSB and FHWA for allowing the access to the detailed FE model used in the investigation of the collapse of the I-35 W Bridge. chiara.crosti@uniroma1.it