Christos G Papakonstantinou

University of Thessaly | UTH · Division of Structural Engineering

Fiber Reinforced Polymer (FRP) composites may be successfully used in numerous structural strengthening applications. One of these applications is as a confining material for reinforced concrete structural elements. Research has shown its effectiveness both in seismic retrofit of existing reinforced concrete columns as well as in new construction o...

This paper presents an experimental study on the flexural strengthening of reinforced concrete (RC) beams with externally bonded layers of textile-reinforced mortar (TRM), as a means of improving their flexural response. The main aim of this study was to investigate the effect of the mortar type in the performance of TRM strengthening system, while...

Cement production industry is responsible for about 5% of the total anthropogenic CO2 emissions. Alternative materials with reduced carbon footprint progressively introduced in the construction industry could be an effective and sustainable solution to mitigate this impact. This paper examines the replacement of standard cement-based binder with ge...

This paper presents a comparative assessment of the compressive behaviour of rubberised concrete (RuC) confined with FRP jackets. In total, three RuC mixes were investigated with rubber content of 6%, 12% and 18% of the total aggregate volume, as well as a conventional concrete mix as a reference. A total of 100 cylindrical concrete specimens (Ø100...

Fiber-reinforced polymers (FRPs) are widely used as composite materials in civil engineering applications to rehabilitate or strengthen reinforced-concrete structural elements. The purpose of this study was to compile an extensive and up-to-date experimental database based on the compressive tests conducted on circular confined concrete structural...

Featured Application: Provide the compressive strength of fiber reinforced polymer confined concrete specimens with machine learning tools based on real, experimental measurements. Abstract: Accurate estimation of the mechanical properties of concrete is important for the development of new materials to lead construction applications. Experimental...

This paper presents an experimental investigation of the mechanical properties of rubberised concrete confined with basalt-fibre textile-reinforced mortar (TRM) jackets. The main aim is to evaluate the effectiveness of the TRM confinement scheme on cylindrical rubberised concrete specimens by examining five different mixtures (rubber content rangin...

Old and seismically prone buildings are in need of strengthening in order to comply with the latest building codes and to prolong their service life. For over two decades fiber-reinforced polymers (FRP) have been successfully used for this purpose. However, the poor performance in high temperatures of organic matrices has led researchers to investi...

This paper presents results of an experimental study on seismic response of reinforced concrete (RC) T-beams with shear deficiencies strengthened with externally bonded steel fiber reinforced polymer (SFRP) strips. Seven cantilever RC beams were strengthened with externally bonded uniaxial SFRP strips in a U-shape configuration and were tested unde...

This study deals with material properties of Portland cement concrete (PCC) made with aggregate that is replaced with recycled asphalt pavement (RAP). A series of PCC mixtures were produced and tested in uniaxial compression using RAP aggregate as substitute of fine and coarse natural aggregate. The main variable was the percentage content by weigh...

The use of composite overlays to strengthen or rehabilitate existing structural elements has been investigated over the past few decades. The most common composites that were used are based on Glass or Carbon fibers impregnated in an organic polymeric matrix, known as GFRP or CFRP, respectively. Thus, many design codes throughout the world provide...

Externally bonded Fiber Reinforced Polymer (FRP) materials can be used to increase the shear strength of reinforced concrete (RC) structural members. These composite materials are typically based on organic matrices, which are used to impregnate the fibers and provide bond to the concrete surface. Existing analytical models were derived using exper...

The shear strengthening behaviour of R/C beams, when applying FRP strips externally with or without anchoring, is studied. This is done by subjecting six specimens of prototype dimensions with or without such strengthening to four-point bending. Specimens strengthened with either carbon or steel FRP strips without the use of anchors exhibited a mod...

The aim of this study is to investigate the shear behavior of reinforced concrete beams strengthened with either Carbon (CFRP) or Steel (SFRP) fiber Reinforced Polymers. The investigation also includes the use of an anchoring system. The strengthened reinforced concrete beams along with a non-strengthened control beam were tested monotonically unde...

The aim of this study is to upgrade the shear capacity of reinforced concrete (R/C) beams strengthened with either Carbon (CFRP) or Steel (SRP) fiber Reinforced Polymers with strips having the form of either closed or open hoop external transverse reinforcement. This investigation also includes the use an anchoring device. Seven prototype specimens...

This study investigates the bond behavior of corroded reinforcing steel confined with carbon fiber reinforced polymer (CFRP). Corrosion of steel reinforcement in reinforced concrete structural elements could pose a significant problem that may result in loss of structural capacity and even failure. Very few studies have investigated the performance...

By far, carbon and glass fibers are the most popular fiber reinforcements for composites. Traditional carbon composites are relatively expensive since the manufacturing process requires significant heat and pressure, while the carbon fibers themselves are inherently expensive to produce. In addition, they are often flammable and their use is restri...

There are a limited number of experimental results available on the retrofit of prestressed concrete structural elements. In addition, there is a lack of analytical models dealing with the flexural performance of such elements. This study addresses the latter problem by presenting a methodology for analysis and design of prestressed concrete flexur...

Biocomposites are typically formed by binding natural fibers derived from plants or cellulose using organic binders. The fibers that are used are normally industrial by-products and, hence, they are abundant and inexpensive. One such material is sawdust, and varieties of composite boards are being manufactured utilizing sawdust as filler material....

The aim of this paper was to investigate the tensile and flexural properties of hybrid laminates made with titanium sheets and high modulus carbon fiber composites. Grade II titanium was used, which exhibits great high-temperature performance and creep resistance, low weight, and high strength. An inorganic fireproof matrix, known as geopolymer, wa...

Steel-reinforced polymer (SRP) composite materials are very attractive due to their low weight and high strength. The ease of installation which significantly reduces repair time and expense is another major advantage. One of the main disadvantages of SRP materials is that the matrices used for their fabrication are typically organic and thus th...

The aim of this study was to investigate the flexural behavior of reinforced concrete beams strengthened with a novel strengthening system. Concrete beams were strengthened with a hybrid retrofit system consisting of high strength steel cords impregnated in an inorganic fireproof matrix (Geopolymer). The strengthened reinforced concrete beams along...

A fiber-reinforced polymer (FRP) composite jacket was applied to the reinforced concrete pier caps of the Silver Spring Cove Bridge in Rhode Island. Since this highway overpass bordered a nearby marina, the corrosive environment of the Atlantic Ocean played a major role in the degradation of the concrete and reinforcing steel. The pier caps exhibit...

The objective of this study was to manufacture fire-resistant biocomposite sandwich plates using waste sawdust as filler and an inorganic potassium aluminosilicate binder. Using binder contents of 29% and 34%, twelve biocomposite plates were fabricated without using any specialized equipment, heat, or pressure, thus producing an environmentally con...

Over the past decade several researchers investigated the use of advanced composite materials for strengthening and rehabilitation of reinforced concrete structural elements. Glass, Carbon and Aramid fiber reinforced polymers were initially used. The brittleness of these systems led a group of researchers into the investigation of high strength ste...

This investigation evaluates the compressive strength and the fire performance of two different types of syntactic foams made by embedding randomly dispersed spheres in fire-resistant, polysialate matrix. The first type of foam utilized ceramic spheres with densities ranging from 0.40 to 0.48 g/cm3, while the second type incorporated expanded polys...

A low temperature cure inorganic matrix, known as geopolymer or polysialate, is Currently being investigated for use in high temperature applications. It provides an excellent opportunity for achieving the goal of producing low cost high temperature resistant composite. This paper deals with the fatigue performance of composites made using this mat...

Protective coatings are being used to seal and protect the concrete surfaces. The most common coatings are based on organic matrices. Their main drawback is their inability to release vapor pressure buildup that causes damage in the concrete and delamination of the coatings. This paper deals with the performance of a new inorganic fireproof coating...

Large quantities of waste tires are generated every year. The proper disposal of the tires creates an increasing problem that needs to be addressed. Many researchers have investigated the use of recycled tire products in several traditional Civil Engineering materials. The use of crumb rubber and tire chips in Portland cement concrete has been the...

The current state of the art in detecting immediate and long-term railway track problems involves both inspectors walking the track lines and train cars instrumented with accelerometers and ultrasonic sensors that are capable of detecting wear of the rail and breakages. Additionally, a widespread practice of sensing rail continuity by using the tra...

Results reported in this paper deal with the bond properties between concrete and an inorganic polymer Fiber Reinforced Polymer (FRP). Tests were conducted using reinforced and plain concrete beams strengthened with carbon fibers and inorganic matrix. Beams were tested under flexural monotonic loading. None of the beams failed by FRP delamination,...

This investigation deals with core materials (syntactic foams) made by embedding randomly dispersed spheres in a Geopolymer matrix. This type of syntactic foam was employed as a light core material for composite sandwich panels with high strength face skins. Syntactic foams are a special kind of particulate composite materials made of a matrix and...

Titanium has been used to meet ever-stricter standards for high-temperature performance, creep resistance, low weight and high strength. Having low density, a high melting point, and high tensile strength it seems like the perfect material for numerous applications. For structural applications where flexural stiffness and strength play the most imp...

High strength composites are being used for making lightweight structural panels that are being employed in aerospace, naval and automotive structures. Recently, there is renewed interest in use of these panels. The major problem of most commercial available sandwich panels is the fire resistance. A recently developed inorganic matrix is investigat...

Synopsis: Use of high strength composites for repair and rehabilitation of bridges and parking decks is steadily increasing. Since these structures are subjected to fatigue loading, the performance of strengthened beams under this type of loading needs to be evaluated. An analytical procedure that incorporates cyclic creep of concrete and degradati...

Two classes of composite made using either ceramic matrix with high temperature fibers or carbon/carbon have been used for various applications that require high temperature resistance, over three decades. However, their use has been limited to special applications because of the high costs associated with fabrication. Typically the composites are...

The objective of the presented study is to examine the effects of glass fiber reinforced polymer (GFRP) composite rehabilitation systems on the fatigue performance of reinforced concrete beams. Experiments were conducted on beams with and without GFRP composite sheets on their tensile surfaces. The specimens were 152 3 152 3 1,321 mm reinforced con...

Typescript. Thesis (M.S.)--University of South Carolina, 2000. Includes bibliographical references (leaves 74-78).