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Mahoning Valley Connector Spillway Bridge (11-05-10)
- 1. over the Deer Creek Reservoir Spillway Stark County, Ohio
- 2. Owner is the Stark County Park District Subcontractor to Stevens-Painton, Corp. Contract Documents by ms consultants Design/Build/Fabricator US Bridge’s Longest Single Span
- 4. Span = 248 ft. c/c of bearings Width = 14 ft. rail/rail Bow string arch truss (Pratt type, with a curved or arching top chord) 18 Panels Profile grade vertical curvature
- 5. 7” Concrete Deck Slab Pedestrian Live Load = 65 psf Vehicular Live Load = H15 Truck Wind Pressure = 75 psf
- 6. AASHTO Standard Specifications for Highway Bridges 17th Edition, 2002 Load Factor Design (LFD) Method AASHTO Guide Specifications for Design of Pedestrian Bridges, 1997
- 7. H15 (15 T) (6k front axle, 24k rear axle) Agency design vehicle wped = the greater of: 85 psf ∙(0.25+(15/√A1)) or 65 psf Guide Specification Section 1.2.1.1
- 9. ASTM A709 Gr. 50W which means A588 Gr. 50 (weathering) Painted Hand Railing & Bridge Ends Stay-in-Place (SIP) forms Future Wearing Surface of 20 psf Laminated Elastomeric Expansion Joints Strip Seal Expansion Joint Shippable Units – 8 field sections per truss
- 10. Hand computations Computer analysis of gravity loads using Truss Analysis Rating Program (TRAP) by University of Maryland’s BEST Center Top chord stability analysis using Excel Spreadsheet or by hand (for the sections without sway bracing) Other Excel Spreadsheets for bolted or welded connections
- 15. Truss Analysis
- 16. Truss Analysis
- 17. Truss Analysis
- 18. Truss Analysis
- 19. Truss Analysis
- 20. Truss Analysis
- 21. Deflections affect fabricated geometry DDL=7.25” Dead Load Deflection MVC = 18.75” Vertical Curve Offset
- 31. U.S. Bridge in Cambridge, OH
- 32. U.S. Bridge in Cambridge, OH
- 34. Plate Processing
- 36. Layout & Cutting
- 37. Laydown
- 38. Shop Assembly
- 39. Shop Assembly
- 41. Finish (Paint)
- 42. Delivery
- 43. Thank you!
Editor's Notes
- Design build fabricate – on this particular project we were not of course the builder, that was Stevens. And it is with mentioning that this bridge is note worthy to our company, because it is the longest single span we have fabricated. The previous record for us was a similar pedestrian bridge in Vermont
- These are the steps we are involved with to design and fabricate the superstructure.
- These are the basic criteria to begin to define the geometry of the bridge.
- Some basic criteria to plan the design loadings of the bridge.
- Basic design codes or specs we used and design method.
- Here is an H15 for non bridge designers And also a code provision based that allows us to lessen the pedestrian live load for large deck areas.
- Here is the cover of the code we used for this design. If this bridge were to be designed this year, we would be using the newest edition which looks like this. It is much more robust than the old one and in line with the LRFD Design Spec.
- Lastly, here are a few more design criteria that were need or use to complete our design work. These are found either in the contract documents, special provisions, or coordinated with the contractor or driven by our choice based on experience.
- These are the basic calculation methods we use to analyze and design our members.
- The reason I put this reference up here is that the 3rd item mentioned above is very important to our work and that is the top chord stability check.
- It is an important stiffness check sometimes called a U-Frame Analysis, that is performed to evaluate and confirm that the relative stiffness between floor beams and the truss vertical/top chord members is such that the top chord members will not laterally deflect beyond an allowable amount ensuring that they can reach their designed loading and not buckle prematurely. We did on this bridge for the short approach sections where there is no sway bracing.
- Just a sample of some hand calculations for a floor beam design.
- Here’s a screen shot of our TRAP program establishing the node geometry.
- And member definitions
- And one of the live load conditions
- Here’s a plot in TRAP that is graphic geometry check.
- Some results output
- Deflection output
- Mentioning deflections … many times, not just strength will control a design, depending on the criteria for deflection response and the member sizes first selected. We use the dead load deflection result to set our planned fabrication camber. For this bridge, we needed to add the vertical curve offset amount to this camber to get our total fabricated camber.
- Now we’re ready to begin to draw the engineering drawings
- We model our bridges in three dimensions and utilize software or methods to capture and define the pieces and assemblies for naming, detailing and quantity counts. This bridge was drawn in what to us is, an already out dated method of 3D AutoCAD, which used layer control and view port manipulation. If this bridge were being designed today, we have advanced this method to something more integrated with software to true BrIM, which attaches data to the solids we draw and allows for an accounting of pieces, assemblies, drawings, details, and can export these details to CNC machine files.
- So here are some screen captures of our drawings. I’ll show you the total sheet and then blow up a particular detail in it. Here is our title sheet. You can see the project criteria is echoed in the left hand corner.
- Here is a framing and elevation plan. Here you can see we are defining major dimensions, sizes and field segments.
- Here is the transverse sections at the abutment and in the middle of the bridge. Again you can see important dimensions, framing connections and the planned deck construction.
- Here is a sheet depicting field construction of the expansion joints and the make up of the bearings.
- This sheet is very important to the contractor as it shows field segments and their lifting weights and splice details. In the first blow up we show the lifting weights of one truss’s segment. In the next blow up, we show or annotate that the assembled trusses, floor beams, decking and railing lifting weights.
- This is just showing a bill of material list in our drawings. For this project we had two of these sheets to list the materials.
- Lastly here is an example of a detail of a curved top chord member. You can see we show its straight length and arc length dimension so our shop can layout and check against them. one
- Real quickly now we’ll go through some slides of our facility that will give you an idea of how we fabricate and prepare the steel. Some of the shots are during processing for this job. Some are not.
- Here’s an aerial shot of our shops and facilities.
- Here’s a view of what we call our beam line or drill line. This is a 3-axis drill line that is CNC controlled rapidly increases our drilling abilities. This is not a piece from Deer Creek.
- This is our plate line where we can drill holes and burn plate shapes. It uses a plasma torch head and also uses drill inserts for hole drilling. The plate rests on wooden slats surrounded by water which removes the smoke and fumes from burning from the air. Again not Deer Creek.
- This is one of our shot blasting machines we use to clean or final prep the steel, depending on the final finish called for. Again probably not Deer Creek.
- Here is one of the Deer Creek bridge’s top chord members being readied to be cut to length.
- Again same shop, we are laying the pieces down for one of Deer Creeks field sections, and arranging them to form the planned “unloaded” camber in preparation for tack and then production welding.
- Next shop over, were have got all of the members arranged and are fitting and welding them in place.
- Back to the first shop, same thing for the opposing segment.
- Now this is not Deer Creek, but it is a weathering steel truss, bound for Georgia, but it shows you the are area where we sand blast the weathering steel before shipping to ensure a uniform appearance.
- This is a view of our paint shop. We painted Deer Creek’s railing and bridge end sections and members here.
- Trucks are loaded in the shops they were fabricated in but many times they end up in one of our trucking areas where we store loads awaiting delivery.