Roman Wan-Wendner

Ghent University | UGhent · Department of Structural Engineering and Building Materials

Ultra high performance concretes (UHPCs) are cementitious composite materials with high level of performance characterized by high compressive strength, high tensile strength and superior durability, reached by low water-to-binder ratio, optimized aggregate size distribution, thermal activation, and fiber reinforcement. In the past couple of decade...

This paper presents: (1) statistical justification and calibration of model B4 using laboratory creep data and long-term bridge deflection data, and (2) statistical comparisons of various types with the existing creep prediction models of engineering societies. The comparisons include the 1995 RILEM Recommendation (Model B3), fib Model Code 1999, M...

The preceding article describes a new multi-decade creep and shrinkage prediction model, labeled B4, which extends and improves the previous RILEM recommendation B3, and a separate article presents a new large worldwide database of laboratory data on creep, drying shrinkage and autogenous shrinkage. This article presents the general optimization co...

Maintaining an adequate safety level in concrete bridges under gradual degradation due to traffic and environmental actions is not only an expensive task, but also filled with some level of uncertainty. Degradation in itself is not easily quantifiable because numerous aspects reduce the load-bearing capacity of a concrete bridge. Furthermore, the e...

Einleitung Bauwerkserhaltung Regelwerke für die Bauwerksprüfung Integrierte Lebenszyklusbetrachtung Schadensidentifikation an Bauwerken aus Konstruktionsbeton Systembetrachtung – Resttragfähigkeit geschädigter Bauwerke Degradationsmodelle für Bauwerke aus Konstruktionsbeton Zusammenfassung und Schlussfolgerung Literatur

The use of fibre-reinforced concrete (FRC) has been substantially increasing in the last few years, in different fields of the construction industry. Recently, many experiments have been performed to observe the short- and long-term mechanical behaviour of FRC, and several models have been formulated to capture its mechanical response. In this work...

The premature debonding phenomenon of fiber-reinforced polymer (FRP) composites, when externally applied to an RC structure , prevents this technology from fully exploiting its ability of increasing the strength of the member. This work focuses on the use of the lattice discrete particle model (LDPM) to simulate the bond behavior of FRP-concrete jo...

This work aims to develop advanced macro-and mesoscale numerical models to accurately reflect the mechanisms behind the initiation and propagation of concrete fatigue damage. A thermodynamically formulated generalized interface model, that relates fatigue damage growth to cumulative inter-aggregate sliding deformations, is used to describe the inte...

In order to determine the adhesive anchors’ capacity under tensile loading, two test methods (confined and unconfined) are suggested in the guideline. Improvements for one of the two configurations are proposed and tested in this paper. The alternative setup currently being evaluated is a modified version of the one proposed by the RILEM technical...

This contribution summarizes the largest available literature data collection on tensile and shear loaded anchor tests, obtained in two independent studies and performed by two different research groups. It was the objective of the two studies to investigate a possible effect that petro-graphically different coarse aggregate types may have on the t...

This paper presents the mechanical behavior of macro-synthetic fiber-reinforced concrete with polypropylene fibers (MSFRC) under varying temperature environments. The Lattice Discrete Particle Model (LDPM), a meso-scale model for concrete, is used for the plain concrete study. An extended version of LDPM taking into account the effect of fibers in...

Structural adhesives characterized a turning point in the post-connection of structural elements due to their excellent performances and ability to transfer stress without losing their integrity. These materials are typically particle-reinforced composites made by a thermoset polymer matrix and fillers. During the in-situ application of this materi...

Cast-in fasteners, like headed-studs, are important elements widely used in safety-critical applications of the building industry. They allow the connection of structural components through transfer of stresses from load-bearing elements to concrete. Their tensile strength in an unconfined configuration with wide supports depends on the concrete’s...

Concrete durability plays an important role in the serviceability of reinforced concrete structures. Deformation induced by shrinkage and thermal strains can lead to the initiation of cracks which in turn may develop into structural damage during several decades of service life. It is time-consuming and impractical to experimentally investigate the...

The need for reliable test data to verify scientific theories together with the necessity to calibrate code‐oriented expressions and their level of safety have pushed researchers to develop test databases. Such databases collect the work of multiple independent scientific initiatives compiling experimental evidences on similar test configurations b...

The interest and knowledge in the research field of 3D concrete printing are vastly increasing. With the rise of more established printing methods and materials, larger elements with a higher degree of geometric complexity can be printed. This allows to shift the research focus towards the structural application of 3D printed concrete. The need for...

FRP-to-concrete adhesive joints are being used increasingly often across a wide range of structural problems, as they provide the possibilities to overcome the uneven stress transfer and stress concentration often found in conventional mechanical anchor systems. For hybrid FRP/concrete substrates, however, the interfacial bond strength is mainly af...

This paper presents a large experimental campaign and the corresponding analysis quantifying mortar curing effects on the pull-out performance of bonded anchor systems. Standard confined pull-out tests were performed on two commonly used adhesive anchor systems. The two investigated bonded anchor systems were based on different materials, where the...

Employing CaO-based expansive agent (CaO-based EA) and superabsorbent polymer (SAP) in ultra-high performance concrete (UHPC) is a effective strategy to mitigate the shrinkage. The cracking identification can help to verify whether the cracking risk can be reduced. In this paper, the shrinkage cracking behavior of ultra-high strength mortar (UHSM,...

To assure high safety levels and functionality over the lifespan of concrete structures (50–100 years), it is important to understand the material’s behavior. As widely known, concrete changes its performance over time typically leading to enhanced material properties if deterioration mechanisms are neglected (e.g. Alkali-Silica Reaction). This con...

The research field of topology optimization (TO) has yet to find its way into the daily construction practice. With the fast evolution of the 3D concrete printing technology, however, this integration can take a large leap forward. The work reported in this paper explores the possibilities and challenges of applying TO for 3D printed concrete (3DPC...

Thermoset polymers are widely used in the civil engineering field, especially as adhesives, coatings, and matrices for composite materials. During the in-situ application of these materials, thermal activation is typically not possible, resulting in an undefined curing state of the system, which depends on the reaction kinetics and ambient conditio...

Chemically bonded anchors are connecting elements that allow transfer of stresses by adhesion. Their strength and failure mechanism depend on the concrete's confinement, properties of the bonding agent and the installation method. Several investigations on their sustained load behavior have been performed and current standards have adopted the use...

This study investigates moisture uptake and diffusion mechanisms in thermoset particle-filled composites for anchor applications. Two epoxy-based with low inorganic filler content and one vinyl ester-based with high inorganic filler content were studied. Material characterization revealed particle size distribution, particle density, the occurrence...

A preliminary study of two approaches for the internal structure generation utilized in the lattice discrete particle models (LDPM) [1] is presented. The presented methods used for particle generation and placement are meant to capture the internal structure of materials realistically. The first approach governs the positioning of the generated sph...

The mechanical performance of fibre reinforced concrete presents aspects still under investigation, mostly those regarding the long-term behaviour. Even if creep and shrinkage are two well-known phenomena that characterize concrete, in case of FRCs, and in particular of macro-synthetic Fiber reinforced concretes (MSFRCs), there are no reliable mode...

The safe design of fastening systems, especially considering the multi-decade performance, relies on a thorough understanding of mechanisms and processes that lead to excessive deformations or even failure in course of time. According to current design guidelines and standards, adhesive anchor system are designed based on the uniform bond model. Th...

In earlier research it was found that the fracture energy can be obtained from incomplete load-opening curves utilizing Sequentially Linear Analysis (SLA) (Czernuschka et al., 2018; Vorel et al., 2019). This method has the advantage that the traction-separation diagram (TS) becomes accessible without prior assumptions concerning its shape, which is...

Evolution of creep and shrinkage models for concrete structures in Austria and Germany - Evaluation of the current models regarding the sensitivity of the input parameter Concrete is one of the most important materials in civil engineering structures and finds its application in the building of bridges, ground engineering and building construction....

The stability of slender columns is a topic that has been dealt with in research and practice for many years. The importance of this topic also increases with the possibility of using non-linear modeling approaches to determine the stability and with the increasingly complex safety formats. In order to show the complexity and the variability associ...

During curing of thermosetting polymers, crosslinking results in hardening or stiffening of the material. In electronics, for example in encapsulating integrated circuits (die bonding), thermosets are fully cured in a controlled environment (under UV-light or within a thermal oven) such that the highest stiffness possible has been achieved. In buil...

Thermosetting polymers are used in building materials, for example adhesives in fastening systems. They harden in environmental conditions with a daily temperature depending on the season and location. This curing process takes hours or even days effected by the relatively low ambient temperature necessary for a fast and complete curing. As materia...

A large experimental campaign and its analysis are presented with the main goal to experimentally investigate possibly significant influence factors on concrete edge breakout, tested on bonded anchors that are loaded in shear towards a free edge. The main investigated influence factors are (i) the used coarse aggregate type, and (ii) the concrete a...

Numerical modelling of quasi-brittle materials arising from lattice or particle formulations is based on "a priori" discretisation of a medium according to an idealization of its granularity. This paper concentrates on the so-called Lattice Discrete Particle Model (LDPM), which provides accurate modelling of damage initiation and crack propagation...

Fibre reinforced concrete (FRC) is a composite material whose adoption is becoming widespread. The ability of exhibiting remarkable residual capacity after cracking of the cementitious matrix represents its characterizing feature. At present, studies dealing with the mechanical characterization of this material are mainly focused on the analysis o...

Given the growth in structural applications of fibre reinforced concretes (FRCs), the characterization of their mechanical performance, and the formulation of predictive models are necessary. When dealing with FRCs long-term behaviour, concrete creep deformations can be predicted but the fiber–matrix interaction produces new effects, i.e. non-linea...

The long-term behaviour of Fiber Reinforced Concrete is a topic still under investigation. Apart from the conditions related to the serviceability states, environmental conditions affect the material behaviour. The present work is focused on macro-synthetic fibres used as reinforcement. In fact, polymers suffer from creep and temperature affects th...

Creep and shrinkage of concrete are time-dependent deformations that influence primarily the serviceability, and in some cases also the safety, of reinforced concrete structures with and without prestressing. Shrinkage is mainly driven by both self-desiccation and moisture drying if exposed to lower relative humidity environments. In addition, and...

Concrete is undoubtedly the most important and widely used construction material of the last centuries. Nevertheless, mathematical models that can accurately capture the particular material behaviour under all loading conditions of significance are scarce at best. Although concepts and suitable models have existed for quite a while, their practical...

As thermoset polymers find frequent implementation in engineering design, their application in structural engineering is rather limited. One key reason relies on the ongoing curing process in typical applications such as post-installed adhesive anchors, joints by structural elements or surface-mounted laminates glued by adhesive polymers. Mechanoch...

Non-linear finite element analyses have intrinsic model and user factors that influence the results of the analyses. However, non-linear finite element analysis can provide a tool to assess safety using realistic descriptions of material behaviour with actual material properties. A realistic estimation of the existing safety and capacity of slender...

Motivated by tunnel accidents in the recent past, several investigations into the sustained load behavior of adhesive anchors have been initiated. Nevertheless, the reliable lifetime prediction of bonded anchor systems based on a relatively short testing period still represents an unsolved challenge due to the complex nonlinear viscoelastic behavio...

Motivated by tunnel accidents in the recent past several investigations into the sustained load behavior of adhesive anchors have been initiated. Nevertheless, the reliable life-time prediction of bonded anchor systems based on a relatively short period of testing still represents an unsolved challenge due to the complex non-liner viscoelastic beha...

Fiber Reinforced Concrete (FRC) is an innovative composite material whose important capabilities are currently investigated both experimentally and numerically. The development of a reliable predictive numerical model requires the careful consideration of concrete heterogeneity and random or oriented arrangement of fibres reinforcement. Among the m...

The curing reaction of thermosetting resins is associated with chemical shrinkage which is overlapped with thermal expansion as a result of the exothermal enthalpy. Final material properties of the polymer are determined by this critical process. For adhesive anchor systems the overall shrinkage behavior of the material is very important for the ul...

This contribution studies a well-known failure criterion and its application to the life-time prediction of adhesive anchor systems under sustained load. The Monkman-Grant relation, which has been previously applied to a wide range of materials, is for the first time applied to adhesive anchors installed in concrete. It postulates a linear relation...

Recently, a large experimental campaign was completed that attempted to establish a link between petrography of the coarse aggregate, the concrete material properties and the system response in terms of concrete cone capacity. The investigation focused on three normal strength concretes having different coarse aggregate types (quartz, limestone, ba...

A large experimental campaign was completed with the objective to determine how concrete composition and age affect the tensile load capacity of mechanical anchors with concrete cone breakout, tested in three different normal-strength concretes. Structural tests for cast-in headed stud anchors were performed at 28 and 70 days and compared to result...

This contribution studies a well-known failure criterion and its application to the life-time prediction of adhesive anchor systems under sustained load. The Monkman-Grant relation, which has previously been applied to a wide range of materials, is now applied to adhesive anchors installed in concrete. It postulates a linear relationship between th...

Nowadays, fastening systems represent a very important part of the construction industry due to their versatility and use in reconstruction. Therefore, it is essential to study and understand phenomena and effects influencing the lifetime of a fastening system. However, the mechanisms are complex and not yet fully understood. As a result, numerical...

The aim of this paper is to introduce and characterize, both experimentally and numerically, three classes of non-traditional 3D infill patterns at three scales as an alternative to classical 2D infill patterns in the context of additive manufacturing and structural applications. The investigated 3D infill patterns are biologically inspired and inc...

Sample preparation is an important step when testing the mechanical properties of materials. Especially, when carbon nanotubes (CNT) are added to epoxy resin, the increase in viscosity complicates the casting of testing specimens. We present a vacuum casting approach for different geometries in order to produce specimens from functional nanocomposi...