Constantin E. Chalioris

• MS, PhD
• Professor (Full) at Democritus University of Thrace

The behaviour of reinforced concrete shear-critical beams with rectangular cross-section and continuous rectangular spiral reinforcement as transverse reinforcement under monotonous loading is experimentally investigated. Further, an advanced rectangular spiral reinforcement that has shear-favourably inclined vertical links is also presented and te...

The behaviour under torsion of reinforced concrete beams with steel fibres as mass reinforcement is experimentally investigated. Short hooked-ended steel fibres with aspect ratio lf/df = 37.5 are used. Test results of 35 beams with rectangular, L-shaped and T-shaped cross-sections tested in pure torsion are presented and discussed. Various configur...

An analytical approach for the prediction of the torsional response of reinforced concrete (RC) beams strengthened with fibre-reinforced-polymer (FRP) materials is described. The analysis method employs the combination of two different theoretical models: a smeared crack model for plain concrete in torsion for the elastic till the first cracking re...

The European building stock is aging and needs renovation. Holistic renovation approaches, including Vertical Forest (VF) systems, are emerging as sustainable alternatives to demolition and reconstruction. This paper reviews and defines missing reliable damage and hazard intensity measures for the holistic renovation of existing reinforced concrete...

The need to strengthen the existing reinforced concrete (RC) elements is becoming increasingly crucial for modern cities as they strive to develop resilient and sustainable structures and infrastructures. In recent years, various solutions have been proposed to limit the undesirable effects of corrosion in RC elements. While C-FRP has shown promise...

Climate change induces extreme effects with lower-than-designed restoration periods, imposing the necessity of strengthening the structural integrity of existing and mainly older RC structures, which are often demonstrated to be under-reinforced in terms of the shear capacity, mainly due to outdated and old design codes/standards. Thus, finding cos...

Due to insufficient transverse reinforcement, the retrofitting of beam–column joints (BCJs) in existing reinforced concrete (RC) frame structures is commonly required to alter their brittle behavior. The construction industry has extensively embraced carbon-fiber-reinforced polymers (C-FRPs) as near-surface-mounted (NSM) reinforcement. Monitoring t...

The fiber-reinforced polymer (FRP) strengthening of reinforced concrete (RC) elements with torsional deficiencies has not yet been extensively studied. Existing studies have primarily focused on rectangular RC beams. The few studies on L or T-shaped beams have used open-form retrofitting methods. However, premature debonding of the retrofitting fro...

Reinforced Concrete (RC) members in existing RC structures are susceptible to shear-critical due to their under-reinforced design. Thus, implementing a retrofitting technique is essential to eliminate the casualties that could arise from sudden and catastrophic collapses due to these members’ brittleness. Among other proposed techniques, using Carb...

This study addresses the critical need for effective torsional strengthening techniques in reinforced concrete (RC) structures, with a focus on T-beams. Existing methods, particularly those utilizing externally bonded fiber-reinforced polymer (FRP) composites, have been extensively studied for axial, bending, and shear loads, but torsional behavior...

Existing reinforced concrete buildings frequently require shear-strengthening to ensure structural integrity, and externally bonded carbon fiber-reinforced polymers (EB-CFRP) have become a wide-applicable approach. However, slabs and geometric restrictions impede wrapping the element, necessitating incomplete U-shaped applications vulnerable to deb...

Reinforced Concrete (RC) structures subjected to earthquakes can suffer from shear failure, which is often characterized by the formation of critical diagonal cracks and abrupt partial or total collapse. Externally Bonded Fiber-Reinforced Polymer (EB-FRP) sheets and laminates have been a popular method for strengthening shear-vulnerable RC structur...

The need for rehabilitation of Reinforced Concrete (RC) structures is highlighted by the increased requirements for adequate resistance to seismic actions. Recently, a novel Fiber Reinforced Polymer (FRP) -based strengthening approach utilizing FRP ropes has been introduced. The application of this new technique seems to have promising results when...

The present research delves into the experimental investigation of the mechanical properties of bee bricks, which serve as nesting habitats for solitary bees. The study aims to provide valuable insights into the efficacy of these bricks as eco-friendly alternatives emphasizing a low energy footprint. It is designed as a masonry unit to provide nest...

Effective damage identification is paramount to evaluating safety conditions and preventing catastrophic failures of concrete structures. Although various methods have been introduced in the literature, developing robust and reliable structural health monitoring (SHM) procedures remains an open research challenge. This study proposes a new approach...

This experimental study investigates the influence of synthetic macro-fibers added in fiber-reinforced concrete (FRC) prismatic specimens on their flexural response and overall cracking performance. Application of a novel structural health monitoring (SHM) system that implements the electromechanical impedance (EMI) technique and the use of piezoel...

This comparative analysis focuses on evaluating the mechanical performance of nano-, micro-, and hybrid-reinforced cement mortars and pastes. Specifically, the flexural strength, compressive strength, and flexural toughness of multi-modified cementitious composites strengthened with single-walled carbon nanotubes (SWCNTs), micro-scale carbon fibers...

This experimental research examines the electromechanical properties of hybrid cement-mortar composites strengthened with different amounts of multi-walled carbon nanotubes (MWCNTs), carbon fibers (CFs), and polypropylene microfibers (PPs). The experimental program included optimal mechanical improvement at the nano and micro levels. The optimum mi...

Fiber Reinforced Concrete (FRC) has shown significant promise in enhancing the safety and reliability of civil infrastructures. Structural Health Monitoring (SHM) has recently become essential due to the increasing demand for the safety and sustainability of civil infrastructures. Thus, SHM provides critical benefits for future research to develop...

The brittle failure of unreinforced masonry (URM) walls when subjected to in-plane loads present low shear strength remains a critical issue. The investigation presented in this paper touches on the retrofitting of URM structures with textile-reinforced mortar (TRM), which enables shifting the shear failure mode from a brittle to a pseudo-ductile m...

Traditional methods for estimating structural deterioration are generally costly and inefficient, especially for non-accessible structural members. However, recent research has demonstrated that electro-mechanical impedance (EMI) or its inverse electro-mechanical admittance (EMA) measurements can be used to continuously monitor the structural integ...

Citation: Thomoglou, A.K.; Fantidis, J.G.; Voutetaki, M.E.; Metaxa, Z.S.; Chalioris, C.E. Mechanical Characterization of Nano-Reinforced Mortar: X-ray Micro-CT for 3D Imaging of Microstructure. Eng. Proc. 2023, 41, 4. https://doi. Abstract: Microstructural characteristics and mechanical properties of nano-reinforced cementitious mortar using multi-...

Reinforced concrete (RC) beam-column joints (BCJ) are crucial structural components, primarily during seismic excitations, so their structural health monitoring (SHM) is essential. Additionally, BCJ of existing old RC frame structures usually exhibits brittle behavior due to insufficient transverse reinforcement. To alter the brittle behavior of BC...

This research presents the results of a study of carbon nano- and/or micro-modified cement pastes composites and hybrid cement pastes reinforced with single-walled carbon nanotubes (SWCNTs), and micro-scale carbon fibers (CFs) in terms of strength, flexural toughness, electrical conductivity and sensing ability. The crucial parameter investigated i...

The current paper presents the results of an experimental study of carbon nano-, micro-, and hybrid-modified cementitious mortar to evaluate mechanical performance, energy absorption, electrical conductivity, and piezoresistive sensibility. Three amounts of single-walled carbon nanotubes (SWCNTs), namely 0.05 wt.%, 0.1 wt.%, 0.2 wt.%, and 0.3 wt.%...

Traditional methods for estimating structural deterioration are generally costly and inefficient. Recent studies have demonstrated that implementing a network of piezoelectric transducers mounted to critical regions of concrete structural members substantially increases the efficacy of the structural health monitoring (SHM) method. This study uses...

The favorable contribution of externally bonded fiber-reinforced polymer (EB-FRP) sheets to the shear strengthening of reinforced concrete (RC) beams is widely acknowledged. Nonetheless, the premature debonding of EB-FRP materials remains a limitation for widespread on-site application. Once debonding appears, it is highly likely that brittle failu...

Recent research has indicated that the implantation of a network of piezoelectric transducer patches in element regions of potential damage development, such as the beam–column joint (BCJ) area, substantially increases the efficacy and accuracy of the structural health monitoring (SHM) methods to identify damage level, providing a reliable diagnosi...

In this paper the cyclic lateral response of reinforced concrete (RC) beam-column joints with composite carbon fiber-reinforced polymer (CFRP) bars as a longitudinal reinforcement in the beam is simulated with finite element (FE) modeling using software Abaqus. An experimental project of two full-scale joint specimens subjected to cyclic loading wi...

This experimental study presents the effect of different surfactants on micro-scale carbon fiber (CFs) distribution into carbon fiber reinforced cement-based composites (CFRC) in terms of flexural and compressive strength, stiffness, flexural toughness, and strain-sensing ability. Conducting a narrative review of the literature focusing on the fibe...

In this study, a model for the estimation of the compressive strength of concretes incorporating metakaolin is developed and parametrically evaluated, using soft computing techniques. Metakaolin is a component extensively employed in recent decades as a means to reduce the requirement for cement in concrete. For the proposed models, six parameters...

The addition of short fibers in concrete mass offers a composite material with advanced properties, and fiber-reinforced concrete (FRC) is a promising alternative in civil engineering applications. Recently, structural health monitoring (SHM) and damage diagnosis of FRC has received increasing attention. In this work, the effectiveness of a wireles...

p>Nowadays there is an extended need for real-time applications of Structural Health Monitoring in existing concrete structures. This paper deals with the application of a new, low-cost and wireless SHM system that utilises small-sized piezoelectric transducers for continuous damage assessment of Fibre Reinforced Concrete specimen. A PZT-based Wire...

This paper carried out experimental research of concrete specimens with synthetic fibres under repeated splitting tension and uniaxial compression to investigate the efficiency of a proposed health monitoring methodology that implements surface-bonded piezoelectric transducers. The developed technique uses small-sized custom-made devices for diagno...

Modern industry can produce composite materials with a wide range of mechanical properties applicable in the medicine, aviation, and automotive industries, etc. However, the construction industry is responsible for a substantial part of the budgets worldwide and uses vast amounts of materials. Engineering practice has revealed that innovative techn...

Polymer Concrete (PC) is a composite material made by fully replacing the cement hydrate binders of conventional cement concrete with polymer binders or liquid resins. As expected, the physico-mechanical properties of PC concrete are governed by the composition of the PC mixture. The present study aims to examine the effect of the aggregate type an...

Torsional behavior and analysis of steel fiber reinforced concrete (SFRC) beams is investigated in this paper. The purpose of this study is twofold; to examine the torsion strength models for SFRC beams available in the literature and to address properly verified design formulations for SFRC beams under torsion. A total of 210 SFRC beams tested und...

The effectiveness of externally applied fiber-reinforced polymer (FRP) ropes made of carbon fibers in X-shape formation and in both sides of the joint area of reinforced concrete (RC) beam–column connections is experimentally investigated. Six full-scale exterior RC beam–column joint specimens are tested under reverse cyclic deformation. Three of t...

The necessity of ensuring the long-term sustainability of existing structures is rising. An important issue concerning existing reinforced concrete (RC) structures in seismically active regions is that a significant number of them lack the required earthquake-resistant capacities to meet the increased design earthquake demands. Inexpensive, fast an...

Back in the 90′s, the shear design of FRP-reinforced concrete beams was developed based on the shear design of conventional steel reinforced concrete beams. Since then, significant changes were implemented in the shear design provisions of internationally recognized design codes for conventional beams as well as being inconsistent and lack the agre...

The utilization and effectiveness of a custom-made, portable and low-cost structural health monitoring (SHM) system that implements the PZT-based electro-mechanical admittance (EMA) methodology for the detection and evaluation of the damage of flexural reinforced concrete (RC) beams is presented. Tests of large-scale beams under monotonic and cycli...

Synopsis: Recently the use of special reinforcement arrangements has been extended in reinforced concrete members under torsion. These arrangements include (a) continuous rectangular spiral reinforcement, (b) epoxy bonded Carbon Fiber Reinforced Polymer (C-FRP) sheets as external transverse reinforcement and (c) short steel fibers as mass reinforce...

The effectiveness and the sensitivity of a Wireless impedance/Admittance Monitoring System (WiAMS) for the prompt damage diagnosis of two single-storey single-span Reinforced Concrete (RC) frames under cyclic loading is experimentally investigated. The geometrical and the reinforcement characteristics of the RC structural members of the frames repr...

The use of fibers as mass reinforcement to delay cracking and to improve the strength and the post-cracking performance of reinforced concrete (RC) beams has been well documented. However, issues of common engineering practice about the beneficial effect of steel fibers to the seismic resistance of RC structural members in active earthquake zones h...

This paper investigates the ability of steel fibers to enhance the short-term behavior and flexural performance of realistic steel fiber-reinforced concrete (SFRC) structural members with steel reinforcing bars and stirrups using nonlinear 3D finite element (FE) analysis. Test results of 17 large-scale beam specimens tested under monotonic flexural...

The application of externally bonded fiber-reinforced polymer (EB-FRP) as shear transverse reinforcement applied in vulnerable reinforced concrete (RC) beams has been proved to be a promising strengthening technique. However, past studies revealed that the effectiveness of this method depends on how well the reinforcement is bonded to the concrete...

The effectiveness of slightly reinforced thin U-shaped cementitious mortar jacketing for the repair of damaged shear-critical reinforced concrete beams is experimentally investigated. The test project includes two parts. In the first one, five concrete beams over-reinforced against flexure and under-reinforced against shear with different ratio of...

Reinforced concrete (RC) beams under cyclic loading usually suffer from reduced aggregate interlock and eventually weakened concrete compression zone due to severe cracking and the brittle nature of compressive failure. On the other hand, the addition of steel fibers can reduce and delay cracking and increase the flexural/shear capacity and the duc...

Damage detection at early cracking stages in shear-critical reinforced concrete beams, before further deterioration and their inevitable brittle shear failure is crucial for structural safety and integrity. The effectiveness of a structural health monitoring technique using the admittance measurements of piezoelectric transducers mounted on a reinf...

Innovative reinforcement as fiber-reinforced polymer (FRP) bars has been proposed as alternative for the substitution of the traditional steel bars in reinforced concrete (RC) structures. Although the advantages of this polymer reinforcement have long been recognised, the predominantly elastic response, the reduced bond capacity under repeated load...

An analytical methodology for the calculation of the flexural and the shear capacity of concrete members with Fibre-Reinforced-Polymer (FRP) bars as tensional reinforcement is proposed. The flexural analysis is initially based on the design provisions of ACI 440.1R-15 which have properly been modified to develop general charts that simplify computa...

The effectiveness of a new retrofitting technique to upgrade the structural behaviour of reinforced concrete (RC) deep beams without steel stirrups using carbon fibre-reinforced polymer (CFRP) ropes as the only transverse shear reinforcement is experimentally investigated. Five shear-critical beams with rectangular and T-shaped cross-section are te...

A numerical approach for the evaluation of the flexural response of Steel Fibrous Concrete (SFC) cross-sections with arbitrary geometry, with or without conventional steel longitudinal reinforcing bars is proposed. Resisting bending moment versus curvature curves are calculated using verified non-linear constitutive stress-strain relationships for...

A new analytical approach for the evaluation of the shear strength of reinforced concrete beam-column joints with crossed inclined reinforcement is developed. The proposed model considers that a joint member resists to the applied shear via three mechanisms, the concrete diagonal strut, the steel conventional shear reinforcement truss and the X-bar...

The application of an innovative real-time structural health monitoring system is studied through tests performed on flexural and shear-critical reinforced concrete elements subjected to monotonic and cyclic loading. The test set-up involves a Wireless impedance/Admittance Monitoring System (WiAMS) that comprises specially manufactured small-sized...

This study presents an experimental effort for the damage assessment of concrete reinforcing bars using bonded piezoelectric transducers and the implementation of an integration analytical approach based on the electromechanical admittance method. Tests are performed in (i) single steel reinforcing bars with predefined and artificially induced dama...

Damage detection at early cracking stages in shear-critical reinforced concrete beams, before further deterioration and their inevitable brittle shear failure is crucial for structural safety and integrity. The effectiveness of a structural health monitoring technique using the admittance measurements of piezoelectric transducers mounted on a reinf...

Damage detection at early cracking stages in shear-critical reinforced concrete beams, before further deterioration and their inevitable brittle shear failure is crucial for structural safety and integrity. The effectiveness of a structural health monitoring technique using the admittance measurements of piezoelectric transducers mounted on a reinf...

An innovative portable wireless real time structural health monitoring system that can detect the earthquake damage and the structural integrity of reinforced concrete members in seismic-prone regions is experimentally evaluated. Damage detection is achieved by the use of piezoelectric transducers (actuators/sensors) and the implementation of an in...

Structural health monitoring along with damage detection and assessment of its severity level in non-accessible reinforced concrete members using piezoelectric materials becomes essential since engineers often face the problem of detecting hidden damage. In this study, the potential of the detection of flexural damage state in the lower part of the...

The use of photogrammetric surveys for the recording of the structural system status for historic masonry buildings is a new and sound tool for in-depth pathology understanding and rehabilitation decision-making. In this study, the structural system of two historic masonry buildings is investigated based on the recording data obtained via photogram...

Structural health monitoring along with damage detection and assessment of its severity level in non-accessible reinforced concrete members using piezoelectric materials becomes essential since engineers often face the problem of detecting hidden damage. In this study, the potential of the detection of flexural damage state in the lower part of the...

This study presents an effort for the damage assessment of reinforcing bars using bonded piezoelectric transducers and the implementation of an integration approach based on the electromechanical admittance method. The damage is the result of excessive elongation of the bar due to yielding caused by flexural deformation of are in forced concrete el...

Structural health monitoring along with damage detection and assessment of its severity level in non-accessible reinforced concrete members using piezoelectric materials becomes essential since engineers often face the problem of detecting hidden damage. In this study, the potential of the detection of flexural damage state in the lower part of the...

Structural health monitoring along with damage detection and assessment of its severity level in nonaccessible reinforced concrete members using piezoelectric materials becomes essential since engineers often face the problem of detecting hidden damage. In this study, the potential of the detection of flexural damage state in the lower part of the...

An effort for the detection of damages in the reinforcement bars of reinforced concrete members using PZTs is presented. The damage can be the result of excessive elongation of the steel bar due to steel yielding or due to local steel corrosion. In both cases the damage is simulated by considering reduced diameter of the rebar along the damaged par...

Recently, the use of continuous spiral reinforcement has been extended in reinforced concrete elements with rectangular cross-sections. The behaviour of reinforced concrete beams with rectangular cross-section and continuous rectangular spiral reinforcement as transverse reinforcement under pure torsion is experimentally investigated. The presented...

The use of steel fibres as shear resistance mass reinforcement has been well-documented and the possibility of partially or even fully replacing of stirrups with steel fibres has been examined. However, issues of common engineering practice about the optimum content of steel fibres in shear-dominated fibrous concrete beams have not yet been fully c...

The structural upgrading and rehabilitation procedure of a historic building representative of 1920s construction in Thessaloniki, Greece is presented. The case study building is a listed three-storey reinforced concrete flat-slab frame structure sited in Nikis Avenue in front of the old seaside of the city of Thessaloniki. Reinforced concrete colu...

The use of conventional and photogrammetric surveys is presented for the recording of two historic masonry buildings in Greece. The first one is a four-storey traditional tobacco warehouse of the late 19th century in Alexandroupoli which has been partially collapsed in 2005 and constituted an extremely dangerous working environment. The second is a...

This study presents morphology, pathology, recording method, applied rehabilitation procedure and constructional problems of a four-storey masonry building in Alexandroupoli which today is partially collapsed. It was constructed before 1900 and enlarged in 1924 to be used as tobacco warehouse. From 1950s onwards, it has been neglected and because o...

The influence of steel fibres in shear-critical reinforced concrete beams subjected to monotonic and cyclic loading is experimentally investigated. Seven short beams with shear span to effective depth ratio equal to 2 were constructed by steel fibrous concrete and by plain concrete as reference specimens. Hookended steel fibres with an aspect ratio...

In the technical literature the combination of conventional steel reinforcement and prestressing steel as strength reinforcement in a flexural concrete member is usually implied by the term partial prestressed element. Partially prestressed elements are used in the practice and their design is based on rational analysis, on the satisfaction of the...

The already published work on the use of self-compacting concrete jacketing is extremely limited whereas the influence of the repeated loading in retrofitted beams has not been examined yet. This paper presents the findings of an experimental study on the application of a reinforced self-compacting concrete jacketing technique in damaged reinforced...

This study presents an analytical approach to evaluate an optimum content of deformed steel fibres in shear-dominated fibrous concrete beams in order strength and ductility requirements to be satisfied. The proposed methodology is based on the calculations of the flexural and shear capacities and to the concept that a pure flexural response should...

This study presents experimental and analytical results obtained from the application of a reinforced self-compacting concrete jacketing technique for the rehabilitation of shear damaged reinforced concrete beams. Three shear-dominated beams were initially subjected to monotonic four-point bending loading. The damaged beams were first restored usin...

The application of a reinforced self-compacting concrete jacket for the structural rehabilitation of shear damaged reinforced concrete beams is experimentally investigated. Five beams were constructed and subjected to monotonic loading in order to exhibit shear failure. The damaged specimens were restored using relatively thin reinforced jackets an...

This study investigates the active control of the debonding procedure in dynamically loaded concrete members strengthened with Fibre-Reinforced-Polymer (FRP) materials using local smart piezoelectric actuators/sensors and electro-mechanical admittance concept. The proposed method is based on the estimation of the optimum electric voltage in order t...

The influence of steel fibres in shear reinforced concrete beams subjected to monotonic and cyclic loading is experimentally investigated. Seven steel-fibre-reinforced concrete beams and conventionally reinforced beams without steel fibres, used as control specimens, were constructed for the purposes of this study. Hook-ended steel fibres with two...

This study presents the experimental results of six reinforced concrete (RC) exterior beamcolumn joint subassemblages repaired using a thin easy-to-apply RC jacket. The examination of the effectiveness of this intervention for the seismic rehabilitation of old construction joints is studied. The proposed jacket has very small thickness and includes...

This study presents the experimental results of six reinforced concrete (RC) exterior beamcolumn joint subassemblages repaired using a thin easy-to-apply RC jacket. The examination of the effectiveness of this intervention for the seismic rehabilitation of old construction joints is studied. The proposed jacket has very small thickness and includes...

This experimental study investigates the effectiveness of crossed inclined bars (X-bars) as joint shear reinforcement in exterior reinforced concrete beam–column connections under cyclic deformations. Test results of 20 joint subassemblages with various reinforcement ratios and arrangements including X-bars in the joint area are presented. The X-ty...

This experimental study investigates the effectiveness of crossed inclined bars (X-bars) as joint shear reinforcement in exterior reinforced concrete beam–column connections under cyclic deformations. Test results of 20 joint subassemblages with various reinforcement ratios and arrangements including X-bars in the joint area are presented. The X-ty...

The use of a new type of reinforced concrete (RC) jacket for RC exterior beam–column connections damaged by seismic excitations is addressed and experimentally investigated. The proposed jacket has very small thickness and includes small diameter steel reinforcement. This jacketing applies at the joint region and at a small part of the columns and...

The present experimental investigation deals with the torsional strengthening of concrete beams without stirrups using epoxy-bonded carbon fibre-reinforced-polymer (FRP) sheets and strips as external transverse reinforcement. The experimental program comprises 14 rectangular and T-shaped beams tested under pure torsion. Based on the measured values...

The present study addresses an analytical method for the prediction of the entire torsional behaviour of reinforced concrete (RC) beams strengthened with externally bonded fibre-reinforced-polymers (FRP) materials. The proposed approach combines two different theoretical models; a smeared crack analysis for plain concrete in torsion for the predict...

The use of crossed inclined bars in external beam-column connections under cyclic deformations is experimentally investigated. For this purpose, test results of four Reinforced Concrete (RC) joint subassemblages subjected to constantly increasing pseudo-seismic loading are presented. The shear reinforcement in the joint area for two specimens was t...