Koby Greene, PE, CWI

FABRICATION AND DESIGN DETAILS AND PITFALLS

The purpose of this presentation is to discuss some of the consideration often overlooked in contract design details

ABOUT ME• BS Civil Engineering from RPI (2009)• D.A. Collins Construction Co., Inc.

• Structural Steel Erection Estimating and Management• Structural Lifting Estimating and Management• Structural Steel Repair Estimating and Management• Miscellaneous Metal Fabrication Estimating and

Management• Project Management

STRENGTHENING DETAIL

ENLARGED STRENGTHENING PLAN

Missing Fillet Welds

FILL PLATE STRENGTHENING SOLUTION

Accommodates most scenarios – not skewed girders

BENT PLATE SOLUTION

NEW BEARING INSTALLATION AND ALIGNMENT• Sole plate not to extend beyond the end of the girder• Minimum distance from edge of masonry plate to edge of

concrete 3”• Minimum distance from anchor bolt to edge of concrete face 8”• Maximum offset from perfect alignment specified on the contract

drawings (or by specification) – center of bearing to center to stiffener

NEW BEARING INSTALLATION – ANCHOR BOLTS

POTENTIAL PITFALLS• Proposed pedestal height

• Not enough room for cast in place anchors• Drilling and grouting into cap/seat having rebar interference

• Sole plate dimensions• Sufficient room to weld to bottom flange or bolster• Drilling and grouting interference (sole plate wider than

anchor bolt spacing)• Girder bottom flange dimensions

• Sufficient room to weld to sole plate or bolster• Drilling and grouting interference (girder bottom flange wider

than anchor bolt spacing)• Crossframe interference with drilling equipment

OPTIONS• Hang bearings and pour up – no longer allowed in near future• Taper girder flanges• Offset anchor bolt holes• Remove/Reinstall Crossframe• “Trap” anchor bolts under sole plate• Coupling Nut

DRILL AND GROUT CONTRACTOR DESIGN

• Need loading in order to provide design• Spacing and edge distance determined by contract design

NEW WELDED STIFFENER

• Little room to produce acceptable weld between the existing and proposed stiffeners

• Neglects room for existing crossframe/diaphragm and bolts

NEW ANGLE STIFFENER

• Does not have the welding concern• Still does not account for diaphragm• Skewed girders are more difficult to accommodate

WELDING CONSIDERATIONS

• Process• Heat Input• Weld Terminations• Intersecting Welds• Access

SMAW• Portable• Prequalified• All position• Flux coating on electrode• Manual• Starts and Stops• Most Common for Field Welding

FCAW AND GMAW

• Fairly portable• Requires PQR• All position• FCAW can be used with our without shielding gas• Gas shielding requires little or no wind during welding• Semi-automatic

SAW• Not very portable• Requires PQR• Limited to flat and horizontal positions• Uses a granular flux• Can be semi-automatic or automatic

HEAT INPUT• Preheat

• Remove moisture• Lowers cooling rate• Helps to alleviate hydrogen cracking• Reduces shrinkage stress

• Interpass Temperature• Result of weld pass(es)

• Can cause damage from inadequate or excessive temperature

WELD TERMINATIONS• Weld holdback• Weld return• Weld Tabs

INTERSECTING WELDS• Can cause excessive residual stress

• Especially in highly restrained areas or base metals with yield and tensile strengths of similar values

ACCESS• Electrode angle (Drag and Work)• Groove angle• Equipment

BOLTING CONSIDERATIONS• Minimum/Maximum edge distances and spacing• Tightening clearances• Tensioning

BOLT EDGE DISTANCE AND SPACING• NYSSCM• AASHTO• AISC

TIGHTENING CLEARANCE• Sufficient room required to install bolt and properly tension

• Bolt Length• Tensioning equipment

TENSIONING - NYSSCM• Turn of Nut (Preferred)• Direct Tension Indicator

TAKEAWAY• When the existing geometry and constructability considerations

are neglected in the contract design details…• Schedule Delays• Additional Cost

PDH QUESTION #1What is the minimum distance from the anchor bolt to the edge of concrete face?• Minimum distance from anchor bolt to edge of concrete face 8”

PDH QUESTION #2What is the most common process used for field welding?• Shielded Metal Arc Welding (SMAW)

PDH QUESTION #3What is the preferred bolt tensioning method allowed by NYSDOT?• Turn of Nut