New Methods for Inspection and Evaluation of Steel Gusset Plate ...

New Methods for Inspection and Evaluationof Steel Gusset Plate ConnectionsChristopher Higgins, Ph.D., P.E.O. Tugrul Turan, Ph.D.Michael Scott, Ph.D.Sinisa Todorovic, Ph.D.University of Texas at AustinApril 4, 2013

Introduction & Background•Gusset plates present need•Geometry needed for analysis• Verification of designdrawings• As-built data•Collection of data is timeconsuming and expensive•Results are variable

Overall Approach• Capture images in field with digitalcameras (snooper, climbing, fromground level)• Process images into scaledorthophotos• Extract geometric data (machinevision techniques)• Produce FE models (OpenSees)• Run nonlinear finite elementanalyses to rate connections(OpenSees)• No high-level training required• Integration from constructioninspection to rating and archiving

Methodology• Many fabricated steelelements lie in plane :2-D correspondencessimplify transformation• Point correspondences usedto map points based oncentral projection.• Need to establish controlpoints in the real worldimage.X ’ is point inphotographicimage plane(pixel)X is point in “realworld” imageHartley and Zisserman, Multiple View Geometry in Computer Vision, 2004

Methodology• Relate image points (pixels) toreal world control points viatransformation matrix•Remove image perspective(rectification)•Direct Linear Transform (DLT)algorithm•H is 3x3 transformation matrix•Minimum of 4 control points(8 DOF and 1 for scale)•Over constrained to estimateerrorsXi' XiHYi' Y i 1 1 X ’ and Y ’ arepoint coordinatesonphotographicimage plane(pixles)X and Y are pointcoordinates inreal world image

Remember I35W?

MethodologyReference Targets and Image PointsMultiple Scales• Large – 24 and 8 in.• Ultra Corrosion-Resistant PureTitanium (Grade 2) bar• 9 control points• Horizontal reference (memberangles)• Small – 0.8 in. and 0.24 in.• Magnetic base, 9 control points• Can establish auxiliaryreference points for 3Dimaging with niobiummagnets or chalk

Multi-Scale Imaging0.24 in.

Strain Relief Liquid-Tite ® Conduit Grips Flexcor ® Wire Mesh GripsApplication – Liquid-Tite ® Conduit GripsK-10Flexcor ® Wire Mesh GripsStrain Relief Liquid-Tite ® Conduit Grips■ Used on Liquid-Tite flexible metal conduit. Preventsconduit pull-out from connecting fitting subject to stress,tension and vibration.Features■ Mesh is made of single weaveStainless Steel.■ Fitting is made of Diecast Steel.Insulated Non-Insulated FittingCatalog Comparison Catalog Comparison SizeNumber Number Number Number InchesMale StraightSTB-38SF 074-09-3511 ST-38SF 074-09-3401 1/2 (3/8*)STB-50SF 074-09-3512 ST-50SF 074-09-3402 1/2STB-75SF 074-09-3513 ST-75SF 074-09-3403 3/4STB-100SF 074-09-3514 ST-100SF 074-09-3404 1STB-125SF 074-09-3515 ST-125SF 074-09-3405 1-1/4STB-150SF 074-09-3516 ST-150SF 074-09-3406 1-1/2STB-200SF 074-09-3518 ST-200SF 074-09-3408 2STB-250SF 074-09-3520 ST-250SF 074-09-3410 2-1/2STB-300SF 074-09-3522 ST-300SF 074-09-3412 3Male 45 DegreeMale 90 DegreeSTB-4538SF 074-09-3561 ST-4538SF 074-09-3441 1/2 (3/8*)STB-4550SF 074-09-3562 ST-4550SF 074-09-3442 1/2STB-4575SF 074-09-3563 ST-4575SF 074-09-3443 3/4STB-45100SF 074-09-3564 ST-45100SF 074-09-3444 1STB-45125SF 074-09-3565 ST-45125SF 074-09-3445 1-1/4STB-45150SF 074-09-3566 ST-45150SF 074-09-3446 1-1/2STB-45200SF 074-09-3568 ST-45200SF 074-09-3448 2STB-45250SF 074-02-097 ST-45250SF 074-09-3450 2-1/2STB-45300SF 074-02-098 ST-45300SF 074-09-3452 3STB-9038SF 074-09-3541 ST-9038SF 074-09-3421 1/2 (3/8*)STB-9050SF 074-09-3542 ST-9050SF 074-09-3422 1/2STB-9075SF 074-09-3543 ST-9075SF 074-09-3423 3/4STB-90100SF 074-09-3544 ST-90100SF 074-09-3424 1STB-90125SF 074-09-3545 ST-90125SF 074-09-3425 1-1/4STB-90150SF 074-09-3546 ST-90150SF 074-09-3426 1-1/2STB-90200SF 074-09-3548 ST-90200SF 074-09-3428 2STB-90250SF 074-09-3550 ST-90250SF 074-09-3430 2-1/2STB-90300SF 074-09-3552 ST-90300SF 074-09-3432 3Note:*The fitting thread size is 1/2" for 3/8" Liquid-Tite conduit.■ UL514B Listed.■ CSA C22.2 18.FittingCatalog Comparison SizeNumber Number InchesFemale StraightST-38FSF 074-02-021 1/2 (3/8*)ST-50FSF 074-02-022 1/2ST-75FSF 074-02-023 3/4ST-100FSF 074-02-024 1Selection• Refer to page K-17 for further assistance.• Determine Liquid-Tite size.• Determine whether insulated or non-insulated fitting required.• Determine fitting type.2002 National Electrical Code ® Section 368.8(B)(4)Branches from Busways. Branches from busways shall bepermitted to be made by the following: (4) Strain relief cable grips shallbe provided for the cord or cable at the busway plug-in device andequipment terminations.2002 National Electrical Code ® Section 314.23(H)Pendant Boxes. Boxes shall be permitted to be supported bypendants in accordance with the following: (1) Flexible Cord. Boxesshall be permitted to be supported from a multiconductor cord or cablein an approved manner that protects the conductors against strain,such as a strain-relief connector threaded into a box with a hub.All devices listed on this page conform to NEMA WD-1 and WD-6.

Implementation - Software• Loads image• Automatically Identifies target (minimizing error of target points)• Calculates H matrix, measurement errors, and standoff correction• Creates and saves rectified scaled orthographic photograph• Automatically identifies fasteners and assigns members to thembased on geometry• Identifies plate boundaries• Outputs geometric data of image features• Conducts scripted NLFE analysis for multiple limit states inOpenSees (automatic meshing, loading, and extraction of results)using image data (new plate element and meshing algorithms)• Rate connection using LRFR, Allowable, or LFR

Image Rectification ToolExampleMATLAB

Laboratory Example

Field Implementation ExamplesExample: ODOTOriginal ImageRectified

Field Implementation ExamplesOriginalRectifiedExample: SEPTA, Gannet-Flemming

Field Implementation ExamplesExample: SEPTA, Gannet-FlemmingOriginal

Field Implementation ExamplesExample: SEPTA, Gannet-FlemmingOriginalRectifiedD. L. (kips) L. L. (kips) LL I. (kips) (I) C. F. (kips)DL+LL+IM+CF(kips)- Max Min Max Min Max Min Comp. Ten.L4-L5 136 540 0 69 0 -6 0 NA 745U4-L514 145 -90 18 -11 -5 14 -92 191U5-L5-13 14 -99 2.00 -13 4 0 -125 7

Example –Complex CNC Fabrication

Example: As-Built Deviations from DesignDesign DrawingTypical View of ConnectionDifferences are subtle to the eye

Real vs Ideal Compared• Typical View ofConnectionWork point shifted due tomember alignment!Extra bolts!Plate clipped differently

Other Needs: Combine Multiple Images+=

Mosaic from Multiple Images

Close-Range Requirements (climbingand other practical needs)Obstructed ViewFish-Eye Image

FisheyeEquisolid-angle projection:• Nikon D300• Nikkor Fisheye, 10.5 mm• Resolution = 4288 x 2848• Sensor Size = 23.6 x 15.8mmEquisolid-angle projection:2 21 x ysin( arctan( ))x 2c2 z2 y 1 x 2 21 x ysin( arctan( ))y 2c2 z2 x 1y x, yImage coordinatesx, y, z Real world coordinatesc Principal distance

DefishedEquisolid-angle to Pinhole:x c1 1x y22 x1 2 tan(2sin ( )) y2 x2 22c2121y c1 11 12 212y x22 y1 2 tan(2sin ( )) x2 y2 22c2121x, yPinhole image coordinatesx, y Fisheye image coordinatescc Pinhole principal distance Fisheye principal distance

Close-Range StepsFisheye Image@ arms lengthDe-FishedRectified

3D Imaging – Plate Imperfections+=

3D Imaging – Plate Imperfections=+Also can get 3D

Fabricate Retrofit Plates from ImagesCape Cod, MassachusettsShop drawings were incorrect!30

Tracking Changes Over Time

Use Machine Vision to Scan ImagesID TargetLocate features (fasteners and edges)Look for changes33

Nonlinear FE Analysis from Image DataX,Y,Z geometry (digital image),Thickness of plate (field measured),Material (drawings),Ratio of member forces (stress sheet)

Scripted NLFEA from Image Data•Yielding of the Plate•Non Sway Buckling(Euler Buckling)•Sway Buckling(Euler Buckling)NeedMemberInteraction!•Easy, fast and convenient for parametric studies, however since the member stiffness is notintroduced, can not capture the sway buckling.•Member stiffness can be introduced as a spring attached to the fastener locations•Calibration according to experiments

Automatic Output Generation (Service)Combined Members : von Mises StressesLook for yielding at integration points, neglect fasteners

Validation of Methods by Experiments

Gusset Plate Experimental Setup

Summary• Suite of imaging tools for rapid and accurate collection ofgusset plate field geometry• Implemented in practice by DOTs and consultants• Image data used in scripted FEA or for manual evaluations• Easily compare as-built with design drawings• Methods validated through large-size experiments• Quantitative image data enrich inspection and evaluation• Integration of inspection and analysis tasks speeds ratingand increases fidelity• Transformative for bridge evaluation and management

AcknowledgementsBruce Johnson – Chief Bridge EngineerSteven Soltesz – Research CoordinatorOregon TransportationResearch and EducationConsortium

AcknowlegementsFHWA Turner Fairbank HRLNew York DOTOregon DOTCalifornia DOTTexas DOTWisconsin DOTNorth Carolina DOTIdaho DOT•FHWA pooled fund study #1302http://www.pooledfund.org/

Questions?