Jovan Tatar

• PhD
• Associate Professor at University of Delaware

This research explores complementary shear strengthening and anchorage effects of CFRP U-wraps on reinforced concrete beams strengthened in flexure using externally bonded CFRP sheets. Through experimental testing of large-scale beams, the research aims to enhance the understanding of how the dual strengthening and anchorage functions of U-wraps in...

Concepts of sustainability, climate change, and resilience have become increasingly important in undergraduate education across all engineering disciplines. Solutions to climate change require interdisciplinary efforts and it is important to engage undergraduate students in these topics to develop a workforce that is capable of tackling these chall...

Externally bonded wet-layup carbon fiber-reinforced polymer (CFRP) strengthening systems are extensively used in concrete structures but have not found widespread use in deficient steel structures. To address the challenges of the adhesive bonding of wet-layup CFRP to steel substrates, this study investigated the effect of core–shell rubber (CSR) n...

Although carbon fiber-reinforced polymer (CFRP) composites have been extensively used to rehabilitate many deficient bridges, data warranting their long-term performance is lacking. Current durability testing of CFRP composites involves accelerated conditioning as a part of material specification requirements to ensure that they maintain mechanical...

This research investigated the durability of fiber anchors in bond-critical CFRP systems for concrete structures. While the durability of CFRP and CFRP-concrete bond is well-studied, the durability of fiber anchors in typical bond-critical applications remains unexplored. To address this gap, fiber anchors were tested in 152×152×508-mm notched beam...

This study compared the mechanical properties of a recyclable flax fiber reinforced polymer composite (FFRP) with a covalent adaptable network (CAN) matrix to an FFRP composite with a conventional (unrecyclable) epoxy resin matrix. The results indicated that composites fabricated via vacuum-assisted resin transfer molding (VARTM) exhibited up to 19...

A novel posttensioning technique using nickel‐titanium‐niobium (NiTiNb) shape memory alloy (SMA) wires for the repair of reinforced concrete beams was evaluated numerically. A finite element model of a reinforced concrete beam was developed within a damage mechanics framework to simulate concrete cracking and subsequent posttensioning. The predicte...

As transportation agencies largely neglect joint sealant maintenance in concrete pavements, water infiltration into the deteriorated joint and subgrade often results in base softening, erosion, and faulting, posing a significant financial burden on taxpayers. To improve the durability performance of concrete pavement sealants, an elastomer with sel...

This paper describes a novel composite placement process to fabricate stand-alone structural pipe within existing legacy pipelines-with no disruption in gas service. The process utilizes low-cost, UV-curable, glass fiber reinforced plastics (GFRP) for discrete preforms made from continuous fiber fabrics. These sections are designed to meet 50-year...

Joints often control the design of composite structures because they represent locations of high stress concentrations. Adhesive joints offer several benefits over mechanically fastened connections such as reduced stress concentrations, and higher joint efficiency. This study evaluates the performance of stepped lap adhesive joints. The novelty lie...

This study evaluated the bond performance of overlays bonded to ultra-high performance concrete (UHPC) within the context of Delaware Department of Transportation (DelDOT) bridge applications. Polyester polymer concrete (PPC), latex modified concrete (LMC), and modified class D concrete (MCD) are applied as overlays on UHPC components to protect th...

Externally bonded carbon fiber-reinforced polymer (CFRP) composites have been instrumental in the flexural strengthening of concrete structures. However, intermediate crack debonding from the concrete substrate is a governing failure mode in most externally bonded CFRP applications, limiting the composite strength utilization and deformability of a...

Damage of highway bridges due to over-height vehicle collisions is experiencing a noteworthy increase in the United States. This paper provides an overview of various prevention and protection schemes, including re-routing methods, warning systems, clearance augmentation, impact absorbers, and a description of contemporary damage repair techniques....

The effectiveness of externally bonded carbon fiber reinforced polymer (CFRP) composites for structural rehabilitation depends on their long-term performance. Current durability testing of CFRP composites involves accelerating conditioning to ensure that they maintain their mechanical properties during service life. However, without field data, rel...

This study assesses physical and chemical properties of fiber reinforced polymer (FRP) composite materials aged in Alaska’s subarctic climate. Carbon FRP (CFRP) and glass FRP (GFRP) samples were collected in 2019 from the exterior and interior of Ted Stevens International Airport (TSIA, retrofitted in 2008) and McKinley Tower (MKT, retrofitted in 2...

Buried culverts are important structures within our civil infrastructure that convey water beneath roadways, bridges, and other systems while also being load bearing. However, many culverts are deteriorating and reaching the end of their design life span. Spray applied pipe liners (SAPLs) have become a popular rehabilitation strategy to strengthen...

Bridge owners are routinely faced with the challenge of rating bridges or culverts that are missing information. Concrete bridges and culverts make up the largest percentages of bridges with missing information. While some guidance is provided in the AASHTO Manual for Bridge Evaluation for load rating bridges with missing information, it is limited...

Externally bonded fiber-reinforced polymer (EBFRP) composites are a cost-effective material used for repair and seismic retrofit of existing concrete structures. Even though EBFRP composites have been extensively utilized over the past 20 years as seismic retrofits, there are few data documenting their performance in a real shaking event or after l...

Externally bonded carbon fiber-reinforced polymer (CFRP) composites have been instrumental in the flexural strengthening of concrete structures because of their high strength-to-weight ratio, corrosion resistance, rapid and easy installation, and reduced cost compared to complete or partial component replacement. However, a governing failure mode i...

Owing to their high strength-to-weight ratio, corrosion resistance, rapid and easy installation, and lower cost when compared to complete or partial component replacement, externally bonded carbon fiber-reinforced polymer (CFRP) composites have been instrumental in the flexural strengthening of concrete structures. However, debonding from the concr...

Effectiveness of externally bonded carbon fiber reinforced polymer (CFRP) composites for structural rehabilitation depends on their long-term performance. Current durability testing of CFRP composites involves accelerating conditioning to ensure that they maintain their mechanical properties during service life. However, without field data, relatin...

As part of the effort to improve the seismic performance of buildings in Alaska (AK), many of the deficient structures in Anchorage, AK, were retrofitted—some with externally bonded fiber-reinforced polymer (EBFRP) composite systems. The 2018 magnitude 7.1 Cook Inlet earthquake that impacted the same region offered an opportunity to evaluate the pe...

Although externally bonded fiber-reinforced polymer (FRP) composites are commonly employed to strengthen reinforced concrete members, the durability of these rehabilitation measures is not well understood. This work includes the examination of FRP-strengthened girders after 12 years of service exposed to brackish water, including assessments of rem...

Externally bonded fiber-reinforced polymer (FRP) composites are extensively used for repair and strengthening of concrete structures. The longevity of FRP repairs depends primarily on the durability of adhesive bonds between FRP and the underlying concrete substrate, which is established through epoxy adhesives. In this study, the effect of hygroth...

Externally bonded fiber-reinforced polymer composites have been in use in civil infrastructure for decades, but their long-term performance is still difficult to predict due to many knowledge gaps in the understanding of degradation mechanisms. This paper summarizes critical durability issues associated with the application of fiber-reinforced poly...

Concrete girders can suffer from serviceability issues due to excessive cracking and deflection. In response to this problem, a novel heat-induced post-tensioning technique utilizing unbonded near-surface mounted nickel–titanium–niobium (NiTiNb) shape-memory alloy (SMA) wires was proposed and evaluated. SMAs are a class of smart materials that can...

Concrete girders can suffer from service-ability issues due to excessive cracking and deflection. In response to this problem, a novel heat-induced post-tensioning technique utilizing unbonded near-surface mounted nickel-titanium-niobium (NiTiNb) shape-memory alloy (SMA) wires was proposed and evaluated. SMAs are a class of smart materials that can...

Engineered cementitious composites (ECC) is a class of high-performance fiber-reinforced cementitious composites featuring metal-like strain-hardening behavior under tension and high ductility. The highly ductile behavior of ECC often results in high impact resistance and energy absorption capacity, which make ECC suitable for applications in struc...

Even though epoxy adhesives are used extensively in concrete structures, little fundamental research has been conducted regarding bond formation mechanisms between the adhesive and concrete substrate, which obscures our understanding of degradation mechanisms in the bonded joints. When epoxy adhesive is applied to the concrete substrate, a transiti...

Externally bonded fiber-reinforced polymer (FRP) composites represent a simple and economical solution for repairing and strengthening concrete structures. However, the potential for debonding failure in such strengthening systems becomes prominent when FRP-concrete bonds undergo environmental degradation induced by moisture. Low-viscosity Bispheno...

In 2017, American Society of Civil Engineers (ASCE) reported that 9.1% of national bridges are classified as structurally deficient. Many of these bridges are concrete bridges that also suffer from girder serviceability issues such as excessive deflections and cracking. In response to this problem, external post-tensioning techniques utilizing stee...

When exposed to harsh environmental conditions, the adhesive bond between epoxy and concrete was found to depend almost entirely on the effectiveness of the mechanical interlock which is contingent upon the ability of the adhesive to properly wet and penetrate the substrate. The current study is an investigation of the existence of a distinct inter...

Epoxy adhesives are widely used in concrete structures. However, a common concern regarding the adhesive joints in the infrastructure is their durability when exposed to harsh environments, most particularly, high levels of moisture. The adhesive bond between epoxy and substrate resists applied loads by a combination of chemical (hydrogen) bonds an...

Harsh environmental conditions can reduce the bond strength of externally bonded FRP composites. Current design guidelines in the US, ACI 440.2R and AASHTO FRPS-1, do not explicitly consider the effects that harsh environments may have on the long-term durability of externally bonded FRP systems. In conjunction with the notched-beam three-point ben...

Externally bonded fiber-reinforced polymer (FRP) composites are an effective method to increase the strength and stiffness of bridge superstructures. They have also been touted as a method to prevent or mitigate corrosion of steel reinforcement by reducing the diffusion of chlorides into concrete. Composite durability is generally evaluated using a...

Carbon fiber-reinforced polymer (CFRP) is becoming a method of choice for repair and strengthening of many environmentally aged structures, bridges in particular. Durability of such CFRP repairs/strengthening efforts still remains uncertain. This paper presents the findings from structural and materials testing conducted on a CFRP-wrapped bridge gi...

Externally bonded fiber-reinforced polymer (FRP) composites are becoming a method of choice for the repair/strengthening of civil structures, some of which are situated in environments detrimental to FRP-concrete bond durability. Based on analysis of an extensive database of durability test results from notched-beam three-point bending tests, a bon...

Lack of understanding and confidence in the long-term performance of externally bonded fiber-reinforced polymer (FRP) composites in concrete structures still inhibits their application in repair of aged structures. While synergistic effects of multiple exposure conditions can be severe, it is generally agreed that the single most significant issue...

Fiber reinforced polymer (FRP) composites are becoming a material of choice for strengthening and repair of bridges. In such applications, these materials are consistently subjected to mild to severe environmental impacts. Under such fluctuations in temperature, high humidity and/or tidal water immersion, bond between FRP and concrete degrades, dec...

Performance of adhesive bond between epoxy and concrete in externally bonded FRP composites is critical in most FRP applications and plays a significant role in long-term durability. Characterizing the relative contribution of chemical and mechanical bond is necessary to fully understanding the effect that moisture has on bond. A unique direct shea...

This report describes a research project to investigate accelerated aging protocols for fiber-reinforced polymer (FRP) reinforcement of concrete. This research was conducted in three stages. In the first stage, various spectroscopic techniques were used to investigate the chemical bonding between epoxy and cement. Evidence suggests that hydrogen bo...

Adhesion of bonded FRP composites to the concrete surface is critical for adequate structural performance of the repaired system. Near the flexural cracks, FRP composite bond failures typically represent a mode II crack growth characteristic. In this paper a direct shear test method is developed to determine the fracture energy under Mode II loadin...

Efforts are underway to develop standardised tests to assess the bond capacity of FRP bonded to a concrete substrate. While several bond test configurations have been proposed and some standard tests have been promulgated, many use difficult-to-handle specimens or require relatively complex test apparatuses. This paper focuses on a simple beam-bend...

A four-point Iosipescu shear test is used to evaluate the effects of CFRP reinforcement on crack width development and the corresponding stress of the internal steel reinforcement. The test program indicates that the steel reinforcement yields following cracking in a concrete beam test specimen containing a No. 10 (No. 3) 71 mm2 (0.11 in2)-420 MPa...