Monday, March 30, 2026 10:00 AM - 11:00 AM, Sky Harbor B
The objective of this session is to inform the audience about the innovative applications of Shape Memory Alloys (SMAs) in prestressing concrete bridges. These emerging metallic materials have the unique ability to change shape when heated, which opens up a wide range of unconventional prestressing applications in concrete structures. This mini session will emphasize the superior performance of SMA prestressed transverse reinforcement, including stirrups and spirals, in various bridge elements such as precast girders and piers.
Learning Objectives:
(1) Provide a basic understanding of how Shape Memory Alloy (SMA) bars can be used for concrete prestressing;
(2) Demonstrate the impact of using prestressed transverse reinforcement in concrete members (stirrups and spirals);
(3) Illustrate how SMA transverse reinforcement can reduce steel congestion while still improving the performance compared to conventional steel reinforcement;
(4)
Novel Repair Technique for Transversely Cracked Bridge Decks Using a Coupled Prestressing Plates System With Shape Memory Bars
Presented By: Ernesto Perez Claros
Affiliation: University of Illinois Urbana-Champaign
Description: As concrete bridge infrastructure continues to age and experience increasing service loads, the construction industry requires innovative and effective strengthening and repair methods. Recent research has proven that the adaptive prestressing system (APS) using shape memory alloys (SMAs) is a competitive alternative to conventional materials for introducing effective and targeted prestressing. This presentation presents a novel repair technique based on APS that transfers prestressing forces through coupled prestressing plates (CPPs). The proposed approach is experimentally evaluated using a laboratory bridge deck specimen containing pre-existing, cyclic-induced transverse cracks with residual widths of up to 0.024 in. After mounting two CPPs on the underside of the damaged specimen and connecting APS elements to the plates, prestressing forces are introduced into the repair assembly through thermal activation of the SMA fuses. Next, the repaired deck specimen is subjected to cyclic loading with varying frequencies and amplitudes. The experimental results are used to develop and calibrate a finite element model, which is then used to optimize the design of the repair system. The experimental and numerical results demonstrate the effectiveness of the new technique for closing transverse cracks in bridge decks.
A New Design of Precast Concrete Bridge Piers with SMA Spirals
Presented By: Bassem Andrawes
Affiliation: Univ of Illinois at Urbana-Champaign
Description: Reinforced concrete bridge piers in high seismic zones often experience steel congestion, particularly in new constructions with strict transverse reinforcement requirements in plastic hinge regions. Shape memory alloys (SMAs) have proven effective in retrofitting seismically deficient piers through active confinement, offering unique thermal prestressing capabilities, whereas other strengthening methods in plastic hinge regions have proven problematic. It is often not feasible to apply external confinement in the embedded portion of plastic hinge regions using traditional cast-in-place construction techniques. Precast concrete offers a unique advantage of sequentially applying steel and SMA confinement, which reduces steel congestion in plastic hinge regions without increasing the seismic demand. The seismic performance of the proposed SMA-confined precast bridge pier is evaluated numerically and compared to that of traditional reinforced concrete piers through seismic fragility analysis. Furthermore, a hybrid confinement technique for precast concrete bridge piers incorporating both SMA and UHPC is experimentally evaluated through axial compression tests on concrete cylinders.
Addressing the Issue of End Splitting Cracks in Precast Girders using SMA Stirrups
Presented By: Bassem Andrawes
Affiliation: Univ of Illinois at Urbana-Champaign
Description: In prestressed concrete bridges, deep-height girders with I-shaped or Bulb-Tee section profiles are commonly used for long-span constructions. These section shapes feature wide flanges designed to accommodate prestressing strands, while the narrow web reduces the overall volume of concrete. However, this geometry can lead to splitting cracks during the de-tensioning of the prestressing strands. These cracks occur due to the high compressive forces applied to the flanges, which create bending moments at mid-height because of eccentricity. This study explores a method to mitigate splitting cracks during de-tensioning by using a unique prestressing material, shape memory alloy (SMA), as transverse reinforcement. An experimental investigation is conducted on reduced-scale I-shaped specimens using a setup that simulates excessive loading in the girder's end region. Test results demonstrate that the SMA transverse reinforcement increases cracking strength by up to 85%. This experimental study is complemented by a detailed numerical investigation aimed at quantifying the prestressing effects of SMA reinforcement in the end region of girders to further reduce the occurrence of splitting cracks.