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INSTRUCTORS:
Nicolas Begasse de Dhaem
Mi Jin Jung
Bassem Andrawes
Balaram Luitel
Purpose and Background
These presentations were recorded at the ASCE Structures Congress 2025.
Rehabilitation of Prestressed Concrete Voided Slab Bridges with Minimal Impact to Traffic (12 minutes)
This presentation focused on the rehabilitation of aging prestressed concrete voided slab (or “sonovoid”) bridges, particularly those affected by deterioration of transverse post-tensioning and shear keys. The innovative method involved installing transverse dowels and applying CFRP laminates to restore load-sharing between adjacent beams without altering the bridge profile. Load testing and finite element modeling confirmed improved deflection behavior and allowed the use of AASHTO live load distribution factors again. The method minimizes added weight and disruption to traffic, aligning with environmental and economic goals. Challenges addressed include varied concrete cover depths and the development of reliable epoxy for overhead application. Laboratory tests validated the bond strength of dowels, especially when combined with CFRP, increasing shear resistance significantly.
Strength of Continuous Beams Prestressed with Bonded and Unbonded Strands (15 minutes)
This presentation examined how bonded and unbonded post-tensioned strands influence the shear strength of continuous concrete beams, particularly those with draped tendons. The speaker analyzed inconsistencies in current AASHTO shear design methods for grouted versus ungrouted ducts and presented a finite element modeling approach to validate more unified treatment. The results showed that the presence of grout has negligible impact on shear strength, while neglecting draped strands in compression zones can lead to overly conservative designs. The study proposed simplifying design by using reduced web width regardless of grout presence and including all strands in shear calculations. This research contributes to more accurate, less conservative shear strength predictions and design practices.
Transverse Prestressing of End Regions of Pretensioned Concrete Bridge Girders (22 minutes)
This presentation introduced an innovative approach to mitigate end-splitting cracks in pretensioned concrete girders using shape memory alloy (SMA) stirrups. These smart materials can be thermally activated to induce transverse prestressing without mechanical jacking or anchorage blocks. The study evaluated stress transfer, detailing (e.g., hook behavior), and effects on shear capacity through small- and full-scale specimens and finite element modeling. Results demonstrated a significant reduction in end region tensile strains and splitting cracks, as well as unexpected gains in shear strength. The SMA solution offers a practical and cost-effective way to enhance durability and reduce reinforcement congestion. Issues such as hook opening and thermal activation techniques were also addressed.
Partial Composite Action in Prestressed Concrete I-Girder Bridges (17 minutes)
This presentation explored the presence and implications of partial composite action in prestressed concrete I-girder bridges, particularly during early service life. Using a Texas bridge as a case study, the researcher examined construction practices, surface roughness, and composite behavior through field inspections, non-destructive evaluation, and load testing. The results confirmed that full composite action was achieved at the time of construction, even though older bridges often exhibit partial composite behavior due to degradation. High concrete strength and rough interface surfaces contributed to strong initial performance, exceeding design expectations. This study provides a reference for future assessments of composite action deterioration over time and highlights the importance of initial interface quality and fabrication practices.
Benefits and Learning Outcomes
Upon completion of this course, you will be able to:
- Describe an innovative method for rehabilitating voided slab bridges using transverse dowels and CFRP laminates with minimal traffic disruption.
- Explain the impact of bonded and unbonded strands on the shear strength of continuous post-tensioned concrete beams and implications for AASHTO design methods.
- Identify the benefits and challenges of using shape memory alloys for transverse prestressing in precast concrete bridge girders.
- Discuss how composite action is achieved and assessed in prestressed I-girder bridges during early service life using field evaluation techniques.
Assessment of Learning Outcomes
Students' achievement of the learning outcomes will be assessed via a short post-test assessment (true-false, multiple choice, and/or fill in the blank questions).
Who Should Attend?
- Construction Engineers
- Structural Engineers
- Project Managers
- General Contractors
- Early Career Professionals
- Builders
How to Earn Your CEUs/PDHs and Receive Your Certificate of Completion
To receive your certificate of completion, you will need to complete a short post-test and receive a passing score of 70% or higher within 1 year of purchasing the course.
How do I convert CEUs to PDHs?
1.0 CEU = 10 PDHs [Example: 0.1 CEU = 1 PDH]