CTR Annual Symposium

50 years of Innovation in Bridge Design and Construction

April 23, 2014

Details, Details, Details

The devil is in the detailsor

The beauty is in the details

• A large part of the TxDOT Research Program has been improvement in the detailing of transportation structures to guide design and construction

• Hallmarks of the program– Identification of problem areas from

designers, contractors, or maintenance personnel

– Large-scale tests– Implementation of research findings

Examples—Concrete Structures• Development and splices of reinforcement• Anchor bolt design• Epoxy-coated bars—performance and quality control• Dapped ends of beams—strut and tie models• T-headed bars• Use of precast panels for bridge decks

– Elimination of thickened ends– Skewed bridges

• Repair and strengthening of bridge girders– Damage from over-height loads– Use of CFRP for strengthening

Development and splices of reinforcement

• 1960’s – Ferguson began work on development and use of large

bars• 1970’s and 80’s

– Reevaluation of data – Tests on wall-type specimens, – Effects of Casting position, Consolidation and

superplasiticizers, Impact loading, Interaction with shear• 1990’s

– Bundled bars– Headed bars

Why was this research important?

• Greatly improved understanding of bond because the tests were large scale

• Provided data that led to major changes in bridge and building codes

• Findings were incorporated into the TxDOTDesign Manuals

• Gained national and international attention for TxDOT research program

Anchor Bolts• First work in 1977 resulted in a design equation that was

widely used because there was no other guidance.

• In 2007, the behavior of anchor bolts in ASR/DEF damaged drilled shafts was studied

• Design codes now contain guidance for a large variety of cases involving anchorages in concrete

Bridge Decks• The use of precast, prestressed concrete (PC)

panels for stay-in-place formwork presented a difficult construction detail at expansion

IBTS I-Beam Thickened Slab Detail

Full-scale precast panel (PC) deck

11

Armored joint Sealed expansion joint

No skew

Full-scale skewed bridge deck

UTSE Uniform thickness

IBTS Thickened slab

}

Results• Thickened slab not needed so panels could be

placed at expansion joints• Formwork at joints no longer needed leading

to a safer work environment• Expansion joint hardware could be placed in

topping slab• Punching shear and

flexural capacity of deck at edge was much greater than expected loads

Materials

• Epoxy-coated bars for durability• High-strength concretes and effects of additives• Fiber and alloy steels in corrosive environments• Higher strength steels—80 to 100ksi bars are

being studied and will likely be permitted in codes in the near future

• Materials for life extension--FRP’s, coatings, chemical treatments

Structural Repair and Strengthening

• Similar damage to railroad bridge over Steck Ave. in Austin• Damaged girder brought to Ferguson Lab for evaluation;

repair of severed tendons; and replacement of damaged concrete

Damage to WaelderBridge over I-10 due to over-height load

Damage to Waelder Bridge over I-10 due to over-height load

Structural Repair and Strengthening

• For increased truck traffic and loadings• Use of CFRP materials for improving shear

strength of bridge girders• Combination of CFRP sheets and CFRP anchors

can be used for I and T sections where complete wrapping is not possible

Other topics

• Fatigue studies of steel bridge girders and illumination poles

• Stability of steel girder superstructures• Bolted and welded connections• Behavior of elastomeric bearing pads• Stability of concrete arches—Fort Worth

Impact

• Viewed as leader among states in supporting research that changed bridge design and construction practice

• Influenced structural bridge and building codes worldwide

• Provided training for a cadre of knowledgeable engineers who became leaders in the structural engineering profession

Recognition • Charles S. Whitney Award 1980 from ACI for

noteworthy engineering development work in concrete design or construction

• Alfred E. Lindau Award 2005 from ACI for outstanding contributions to reinforced concrete design practice

• Citations for outstanding individual bridge projects

• Numerous awards for technical papers based on TxDOT-sponsored projects

Personal Reflections

• TxDOT Research Program– Cooperation– Collaboration– Implementation

• The most rewarding research of my career • Played a pivotal role in the development of Civil

Engineering at the University of Texas and in the State of Texas

THANK YOU FOR THESE OPPORTUNITIES