Project Title

Structural Enhancements to Adapt to Impacts of Climate Change

Collaborating Universities

University of Virginia
351 McCormick Dr.
P.O. Box 400742
Charlottesville, VA 22904-4742
www.virginia.edu

Principal Investigator(s)

Devin Harris (UVA) - Email: dharris@virginia.edu
Osman Ozbulut (UVA) - Email: ozbulut@virginia.edu

Funding Source(s) and Amounts Provided (by each agency or organization)

USDOT: $135,000 (Federal)

Total Project Costs

$135,000 Federal

Agency ID or Contract Number

DTRT13-G-UTC33

Start Date

10/01/14

Completion Date

05/31/16

Description

Changing climate is expected to considerably impact the health of civil infrastructure systems. As extreme weather events such as hurricanes, tropical storms, prolonged intense temperatures occur more frequently, state transportation agencies are in need of strategies to avoid, minimize or mitigate potential consequences. The potential adverse effects of the extreme events on civil infrastructure include but not limited to premature deterioration of infrastructure system; extra stresses through thermal expansion in bridges; damage to roads, coastal highways, and tunnels due to heavy precipitation and increased runoff; increased fatigue problems in sign, signal and bridge structures due to extreme winds; and increased scouring problems in bridges due to higher stream runoff and rising sea levels.

The objective of this research is to reduce the vulnerability of civil infrastructure systems in light of expected climate change and associated increase in extreme weather events by developing and integrating advanced composite materials into sustainable structural design. In particular, shape memory alloy-based composites and ultra high performance fiber reinforced concretes will be explored, both independently and as a hybrid composite.

Shape Memory Alloys (SMAs)

SMAs have unique properties such as high strength, very good fatigue and corrosion resistance, large damping capacity, re-centering capability, and ability to undergo large deformations. SMA materials will be used to reinforce a thermoset polymer matrix to produce SMA Fiber Reinforced Polymers. SMA materials have superelastic properties that will overcome the brittle behavior of carbon or glass FRP and provide ductility. SMAs are expected to enhance the damping capacity and toughness of the matrix and provide re-centering ability. SMA composite panels will be fabricated using the vacuum assisted hand lay-up technique. A metal plate will be fixed in place, on the lay-up table, to ensure fabrication of flat panels first. Then, a non-porous release film will be attached to isolate the SMA composite panels from the metal plate. Peel ply will be added over the non-porous release film to facilitate peeling of the SMA composite panels after epoxy curing. Afterwards, SMA strips will be placed on the peel ply and impregnated in the epoxy using a roller. Another peel ply will be applied over the SMA and then a porous release film. In order to provide an air bath to facilitate absorbing the excess of the epoxy, a breather ply layer will be added over the porous release film. Finally, nylon bag with an opening for the vacuum port will be attached to a sealant tape over the metal plate to seal the entire system. A vacuum pump will be connected to the vacuum port and a vacuum pressure will be applied for 24 hours to remove air bubbles and excess epoxy. After 24 hours, the vacuum pump, nylon bag, and release films will be removed. The SMA composite panels with peel plies will then be left to cure in air at ambient temperature for another 24 hours. After 48 hours of fabrication, the peel plies will be removed and the SMA composite panels will be cured under the same conditions for another 12 days before being tested.

SMA composites with different reinforcement volume fractions will be prepared. A Dynamic Mechanical Analyzer (DMA) will be used to measure tensile properties of the fiber and the damping properties of the resin, fiber, and composite. To determine the transformation temperatures of the SMA fibers and the degree of cure in the resin and the composite, a differential scanning calorimeter (DSC) will be used. Monotonic and cyclic tensile testing of the test coupons will be conducted at different strain levels. To measure the damage resistance of the SMA composite, the impact tests will be conducted as per ASTM D7136 [82]. In addition, scanning electron microscopy (SEM) will be performed on various polished surfaces and the fracture surfaces of damaged surfaces to study the presence of voids, fiber pull-out, fiber-matrix debonding, and the interfaces between SMA fibers and resin.

Ultra-high Performance Concrete (UHPC)

Ultra-high performance concrete can be classified as a cementitious composite with fiber reinforcement. The cementitious matrix is extremely dense and provide very high strength, but more importantly a compact microstructure that is virtual impermeable to contaminants, making the material extremely durable and robust. In addition, the fiber reinforcement provides resistance to micro-cracking, analogous to conventional reinforcement at the macro-scale. Transportation agencies have explored the applications of UHPC for a number of years, but its integration into standard practice has been limited by skepticism surrounding the proprietary formulation of commercially available products and their costs; however, in recent years, a number of formulations have been developed with an emphasis on non-propriety designs and locally sourced materials. While these formulations have shown promise, their consistency and performance have not been proven to be comparable to the commercially available products that have dominated the UHPC market in recent years.

UHPC test specimens will be developed from both non-proprietary and proprietary formulations for evaluation of both mechanical (e.g. compressive, tensile, flexural, and both) and durability (e.g. chloride ion, freeze-thaw, scaling) characteristics. Much of this information is available in literature, but no studies have included comparative evaluations under similar conditions. These mechanical properties will provide the basis from which decisions on material application can be formulated (e.g. which material is appropriate for new and rehabilitation applications in infrastructure). In addition, to providing mechanical and durability properties, the comparative analysis is expected to provide considerable insight into the challenges associated with implementation, such as batching/mixing complexity, curing requirements, and cost.

Hybrid Composite – SMA Reinforced UHPC

While these two materials alone provide a great deal of promise for transportation applications, their hybridization has the potential to provide even more benefit to the end user. Following the individual material assessment, designs integrating the combination of these materials (SMA and UHPC) will be explored and refined for applications to transportation infrastructure systems. The objective will be to leverage the unique performance characteristics of the base materials to develop sustainable transportation design solutions that are sustainable, adaptable and resilient to environmental change and multi-hazards.

 

Implementation

Potential implementation of project outcomes

The results of the project have potential applications for implementation and/or deployment that can be used by DOTs and others, where the project team can perform additional studies to apply advanced composites for rehabilitation of concrete structures.

Impacts

Expected benefits and impacts

The results of this research will enable the improved damage resistance and increased service life of civil infrastructure systems, and lead to more efficient infrastructure design under extreme weather events. These activities are potentially transformative since it could promote the use of advanced composites with unique properties such as high ductility, high corrosion resistance, high workability, self-centering and self-sensing abilities, and good fatigue resistance in a wide range of civil engineering applications to design more sustainable structures.

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