Research | Tatar Research Group

CAREER: Durable Biomimetic Adhesives for Structural Engineering Applications

Sponsor: National Science Foundation

This Faculty Early Career Development (CAREER) program will provide a new, nature-inspired and durable adhesive joints in concrete structures by mimicking mussel adhesion. Adhesive joints are used in multiple engineering fields to accelerate production, prolong product life, reduce stress concentrations, and control maintenance costs. Structural engineering, however, relies on bulkier and less economical mechanical joining methods as the existing adhesives are not durable in wet environments. Inspired by mussels’ ability to establish and maintain adhesion to mineral substrates underwater, this project will create a moisture-resistant adhesive joining method for structural concrete. This progress in adhesives technology will (1) improve resilience of existing infrastructure by enabling innovative, durable repair and retrofitting methods and (2) stimulate the advancement of disruptive construction techniques (e.g., additive manufacturing and prefabricated construction) for affordable housing and next-generation civil infrastructure.

Mitigating Cracking in Ultra-High Performance Concrete Bridge Connections

Sponsor: USDOT, Center for Integrated Asset Management for Multimodal Transportation Infrastructure Systems (CIAMTIS)

In the proposed project, we are collaborating with Prof. Farshad Rajabipour to (1) develop and investigate an innovative method for repeatable surface-texturing of precast concrete substrate in the connection region to enhance mechanical bond strength between UHPC and NC; and (2) investigate methods of reducing shrinkage in UHPC to mitigate interfacial and cohesive cracking. The findings from this work will improve the reliability of bridges constructed utilizing ABC techniques. The project, therefore, contributes to improved durability and extended life of transportation infrastructure, one of the primary objectives of CIAMTIS.

TuFF Internal Wrap for Rapid Pipeline Repair (TuFF iWRAP)

Sponsor: ARPA-E

The University of Delaware has created the “TuFF internal WRAP for Rapid Pipeline Repair” (TuFF iWRAP) program, establishing a novel composite material feedstock and robotic placement process to fabricate stand-alone structural pipe within existing pipelines. The project’s innovation is enabled by a low-cost, high-performance, and conformable short fiber feedstock based on the Tailorable universal Feedstock for Forming (TuFF) material. A two-step repair strategy is proposed, where straight and slightly curved pipe sections will be internally wrapped and then repaired using complex geometry pipe transitions, such as T-joints, diameter reductions, and steep bends. If successful, the TuFF iWRAP project would lower costs by 50%, extend the length of pipe repair sevenfold, and reduce societal costs by maintaining gas delivery to customers during repair.

Extending the Service Life of Rigid Pavement Joints with Self-Healing Sealants

Sponsor: USDOT, Center for Integrated Asset Management for Multimodal Transportation Infrastructure Systems (CIAMTIS)

According to a recent Federal Highway Administration (FHWA) technical advisory, most state transportation agencies defer or completely ignore joint sealant maintenance, which leads to accelerated deterioration of their assets in the long term. Drawing on an interdisciplinary collaboration between structural and materials engineering (Tatar), materials science (Kloxin), and concrete and pavement engineering (Brand), the research team will address the problem of poor sealant performance by conducting research to address the following project objectives:
(1) synthesize a new sealant with repeatable self-healing abilities that will extend the service life of joint seals;
(2) characterize the performance of the new self-healing sealant at the materials level under typical environmental conditions experienced by pavement joints; and
(3) validate the project’s contribution through intermediate-scale mechanical and accelerated testing of realistic pavement contraction joint test specimens.
Successful completion of the project has a tremendous potential to significantly reduce the maintenance costs and extend the service life of concrete pavements.

The project seeks to assess the long-term performance and effectiveness of fiber-reinforced polymer (FRP) composites in facilitating rapid structural renewal of deteriorated concrete bridges in the Federal Region 3. Although FRP composites have been extensively used to strengthen and repair deteriorating bridges across the country, data warranting their long-term performance is lacking. The need for research on the durability of FRP composites for infrastructure was highlighted in a recent congressional hearing and a National Institute of Standards and Technology (NIST) report. The state of Delaware has the first (1994) externally bonded FRP repair installed on a publicly owned bridge in its inventory, offering a unique opportunity to study the durability characteristics of these materials over a timespan of over 25 years and contribute to a prominent national research need.

Durability Assessment of Externally Bonded Fiber-Reinforced Polymer (FRP) Composite Repairs in Bridges

Sponsor: USDOT, Center for Integrated Asset Management for Multimodal Transportation Infrastructure Systems (CIAMTIS)

Bonding of Overlays to Ultra-High Performance Concrete

Sponsor: Delaware Department of Transportation

DelDOT has implemented innovative ultra-high performance concrete (UHPC) in a state-owned bridges. UHPC offers significant cost-savings for the state due to its superior mechanical properties that allow for thinner structural components, excellent durability properties, and strong bonding to the conventional concrete substrate. However, the bonding quality between UHPC components and typical overlay materials used by DelDOT such as latex modified concrete (LMC), polyester polymer concrete (PPC), and thin epoxy overlay. Existing literature also does not address this concern. Main aim of the proposed work is to elucidate the bonding characteristic between the typical overlay materials used in the state bridge projects and UHPC, and propose a set of guidelines for implementation. To achieve the project aim, the research program was divided into four tasks: (1) literature review, (2) field evaluation of overlay bonding to UHPC, (3) laboratory pull-off experiments to determine UHPC-overlay bond strength and failure mode; and (4) reporting and dissemination.

Structural Performance Verification of Structural Pipe Liners for Corrugated Metal Pipes

Sponsor: Delaware Department of Transportation

The objective of this project is to verify the structural performance of structural pipe liners with varying thicknesses applied to corrugated metal pipes through full-scale testing. Testing is needed to validate the ultimate strength and failure modes of these liners, which are believed to provide adequate resistance in the absence of the host conduit due to corrosion. The proposed research program is divided into seven tasks: (1) kick-off meeting, (2) literature review, (3) materials testing, (4) structural analysis, (5) full-scale testing, and (6) structural verification, and (7) reporting and dissemination. The project team will build upon the existing knowledge and results provided by the Transportation Pooled Fund Program on Structural Design Methodology for Spray Applied Pipe Liners in Gravity Storm Water Conveyance Conduits (with several partner states including Delaware) to provide additional experimental and analytical results that can support the development of a national design standard, which does not currently exist for applied structural spray liners. The research team is qualified and excited to perform the proposed tasks and collaborate with DelDOT personnel on a critical maintenance strategy that can be cost-effective with potential widespread use by other DOTs once verified.

Load Rating of Bridges and Culverts with Missing or Incomplete As-Built Information

Sponsor: National Academy of Sciences, National Cooperative Highway Research Program (NCHRP)

Lack of as-built information for bridges and culverts is a problem that many state departments of transportation (DOTs) are facing across the nation. Analytical load-rating of bridges and culverts can only be successfully performed with complete information of the structure’s as-built composition. When missing as-built information, conservative assumptions are often used, which can result in load postings with economic and logistical implications. There is uncertainty about the level of uniformity in the way different DOTs approach the problem of load rating the structures with missing or incomplete plans.
In a recent survey, the majority of surveyed states reported more than 100 bridges with missing plans in their inventory. In some of the surveyed states, bridges with missing as-built plans exceed 25% of the total bridge inventory. The methods used to obtain missing information vary significantly between different jurisdictions. Employed methods range from diagnostic and/or proof load testing, using engineering judgement, a range of non-destructive testing techniques to determine materials and geometrical properties, to utilizing conservative assumptions.
The objective of this synthesis is to document current practices for load rating of bridges and culverts with missing or incomplete as-built plans used by DOTs.

Smart Polymer Sealant for Natural Hazard Resilient Energy-Efficient Buildings

Sponsor: University of Delaware Research Foundation

Conventional sealants at fenestration-to-wall interfaces often fail which leads to energy lossess due to outdoor air infiltration, and moisutre damage to structural and non-structural building components due to unmanaged wind-driven rain ingress. Main cause of damage to the sealants are cyclic deformations at fenestration-to-wall interfaces induced by building thermal movements. As our population continues to grow, especially in the coastal communities, it is becoming increasingly important to limit financial burden of energy losses and natural hazard-related damages—a task that this project aims to contribute towards. The herein proposed research will address the identified problem with the conventional sealant technology by conducting work on two fronts to: (1) understand the extent of thermal movement at the fenestration-to-wall interface through combined numerical modeling and experimental measurements in buildings; and (2) develop a smart, durable, self-healing polymer sealant for building envelope applications that utilizes shape-memory effect to synchronize the sealant deformation with the thermally-induced fenestration-to-wall interface gap size change. The knowledge this project will generate is critical for advancing the hazard resilience and energy efficiency of the built environment.

Design of Anchors for Rapid and Durable Strengthening of Bridges with Externally Bonded Carbon Fiber Reinforced Polymers

Sponsor: USDOT, Center for Integrated Asset Management for Multimodal Transportation Infrastructure Systems (CIAMTIS)

Over 19% of bridges in the Federal Region 3 are structurally deficient; thus, a reliable strengthening technique such as anchored externally bonded CFRP has potential to rapidly address some of the bridge deficiencies. The objectives of the research are twofold: (1) to define the change in behavior and failure modes between unanchored and anchored externally bonded CFRP in flexure; and (2) to propose additions to the existing flexural strengthening design guidelines (e.g., ACI 440.2R-17 [1]) based on the findings. This research is expected to greatly impact the development of American Concrete Institute (ACI) design guidelines under the auspices of ACI Committee 440. To ensure relevance and significant impact on the current state of practice, the project team is partnering with the ACI 440 committee (see attached letter of support in Appendix C) which is championing the development of design guidelines for anchored CFRP.

Performance of Reinforced Concrete Structures with Externally Bonded Fiber Reinforced Polymer Composite Retrofits in the 2018 Anchorage, Alaska Earthquake

Sponsor: National Science Foundation

Externally bonded fiber-reinforced polymer (EBFRP) composites can be used to seismically retrofit structures in a simple and economical manner. However, lack of documented evidence of their performance during an earthquake still limits their widespread adoption. This Grant for Rapid Response Research (RAPID) will study the effects of the November 30, 2018, earthquake (magnitude 7.0) in Anchorage, Alaska, on the performance of EBFRP composite retrofits in reinforced concrete buildings. The 2018 earthquake, which impacted the same region that was severely damaged by the 1964 Great Alaskan earthquake (magnitude 9.2) ground shaking, provides an opportunity to evaluate the effectiveness of EBFRP retrofits in a high-intensity earthquake and learn about their performance. This study will, for the first time, provide information on the performance of EBFRP retrofitted structures in an earthquake that occurred in the United States. The collected data will contribute to improved building retrofit design standards and construction practices, which will cultivate safe buildings and communities resilient to earthquakes, thus promoting national welfare. The findings will benefit practitioners and researchers by providing a unique data set to benchmark the numerical models used to simulate the response of retrofitted structures. The data will be archived and disseminated through the NSF-supported Natural Hazards Engineering Research Infrastructure (NHERI) Data Depot and Reconnaissance Integration Portal (https://www.DesignSafe-ci.org). The graduate student participating in the project will gain valuable research training in field data collection and post-earthquake reconnaissance. This award supports the National Earthquake Hazards Reduction Program.