Josef Hegger

RWTH Aachen University · Institut für Massivbau

Due to the desire for slender buildings with variable room layout, flat slabs are a popular load-bearing element in building structures. However, the slab-column connection is often a governing detail in design due to concentrated load application and the associated risk of punching shear failure. To counter this, the punching shear behavior of fla...

Non-metallic reinforcement enhances the sustainability of concrete structures by allowing the replacement of conventional reinforcing steel and the design of slender members with reduced concrete cover or increasing structural capacity. These advances draw attention to serviceability criteria, such as crack width limitation, which become crucial fo...

In this study, the punching shear behavior of footings under biaxial eccentric loads is numerically investigated. Load eccentricities usually encountered in practice were primarily investigated on flat slabs, whereby the research on footings is still limited. Since the structural behavior of thick footings is significantly different compared to tha...

Determination of the maximum shear capacity of reinforced concrete (RC) beams and slabs has been a challenging task for over 100 years. Recently, the shear crack propagation theory (SCPT) was developed as a unified mechanics-based solution to determine the ultimate capacity and to explain the phenomenon of one-way shear in RC members without shear...

Non-metallic reinforcement increases the sustainability of concrete structures by facilitating a substitution of conventional reinforcing steel and allowing for a design of slender members with a reduced concrete cover or an increase in structural capacity. These advances draw attention to serviceability criteria, such as crack width limitation, wh...

Non-metallic reinforcement not only facilitates a substitution of conventional reinforcing steel, but also allows for slender members with a reduced concrete cover or an increase in structural capacity, significantly improving the sustainability of concrete buildings. The ability of non-metallic reinforcement in advancing the ultimate limit state f...

Due to its insensitivity to corrosion, textile CFRP (carbon fibre reinforced polymer) reinforcement enables the construction of thin-walled concrete structures such as shells, vaults and girder webs with minimal concrete cover. In contrast to tensile and flexural behaviour, strutting and compressive membrane action of cracked thin-walled carbon rei...

More and more often, semi‐precast reinforced concrete slabs with lattice girders are employed for industrial buildings or bridges, where they are exposed to high cycle fatigue loading. Despite research in recent years that has led to the formulation of an S – N curve for lattice girders, the effects of cyclic loading on semi‐precast slabs have not...

Eine hohe Verfügbarkeit und Leistungsfähigkeit der Verkehrsinfrastruktur ist von entscheidender Bedeutung für den Wirtschaftsstandort Deutschland, besonders in Zeiten stetig wachsender Verkehrszahlen. Ein wesentlicher Teil der 40–60 Jahre alten Brücken in Deutschland muss in den nächsten Jahren entweder verstärkt oder kurzfristig ersetzt werden. Zu...

Decades of research in the field of non-metallic reinforced concrete provide an extensive basis for a reasonable construction of structures without using steel rebars. The developed models and approaches allow for a broad and practical use of non-metallic reinforcement. In Germany, the need for design rules for the practical application are met by...

Non-metallic reinforcement not only facilitates a substitution of conventional reinforcing steel, but also leads to slender members with a reduced concrete cover or an increase in structural capacity. The ability of non-metallic reinforcement in advancing the ultimate limit state for concrete members directs attention to serviceability criteria, su...

The pursuit of structurally efficient elements that minimize material consumption while meeting structural performance requirements is becoming increasingly important due to escalating global environmental concerns. This relevance is particularly pronounced for high-performance concrete elements with high-strength FRP reinforcement, such as epoxy-i...

Neben der drastischen Reduktion von CO 2 ‐Emissionen bei der Zementherstellung ist ein effizienter Umgang mit knapper werdenden natürlichen Ressourcen wie Sand und Kies unumgänglich, um die Betonindustrie umweltfreundlicher zu gestalten. In diesem Zusammenhang erscheint die Verwendung rezyklierter Gesteinskörnung als sinnvolle Alternative zu natürl...

The limited understanding of the fatigue behavior of reinforced and prestressed concrete members is one of the reasons why many structures do not reach their expected service life. Without a deeper theoretical understanding of the fatigue phenomena in the various fatigue process zones, reliable fatigue life predictions are not possible. This paper...

Der Beitrag stellt die Nachweisverfahren in Stufe 2 zur Nachrechnung von Bestandsbrücken nach aktueller BEM-ING Teil 2 und deren Weiterentwicklung vor. Ausgehend von den Bemessungsmodellen der BEM-ING Teil 2 für Querkraft und Torsion werden weiterführende experimentelle Untersuchungen der drei Forschungseinrichtungen RWTH Aachen University, TU Münc...

Trotz entscheidender Weiterentwicklungen in den Nachweisformaten in Stufe 2 der Nachrechnungsrichtlinie lassen sich einige Bestandsbauwerke wegen der höheren Verkehrsbelastungen und den veränderten Bemessungsgrundsätzen weiterhin nur mit wissenschaftlichen Verfahren in Stufe 4 nachweisen. Dies stellt sowohl für Anwender als auch Entscheider in den...

Anhand von Querkraftversuchen an 16,5 m langen Spannbetonträgern werden die Einflüsse von Lastart, Querschnittsform, Einspanngrad, Bügelbewehrung und Vorspannung auf die Querkrafttragfähigkeit herausgearbeitet. Die experimentellen Untersuchungen bestätigten die neuen Bemessungsansätze für die Querkrafttragfähigkeit nach der BEM-ING Teil 2. Um noch...

Due to its insensitivity to corrosion, textile CFRP (carbon fibre reinforced polymer) reinforcement enables the construction of thin-walled concrete structures such as shells, vaults and girder webs with minimal concrete cover. In contrast to tensile and flexural behaviour, strutting and compressive membrane action of cracked thin-walled carbon rei...

Most shear tests are performed as standard three- or four-point bending tests, i.e., on one-way simply supported specimens subjected to concentrated loads. The major disadvantage is that these conditions usually do not correspond to the support and load condition of real structures. Structural members such as beams or slabs, are often multi-span co...

The pursuit of structurally efficient elements that minimize material consumption while meeting structural performance requirements is becoming increasingly important due to escalating global environmental concerns. This relevance is particularly pronounced for high-performance concrete elements with high-performance FRP reinforcement, such as epox...

In recent decades, FRP reinforcement has received increasing attention in engineering research of reinforced concrete composites due to its advantages over steel reinforcement, such as corrosion resistance and high strength. Due to brittle failure and high strength-to-stiffness ratio of the FRP reinforcement, the flexural behavior of FRP-reinforced...

In civil engineering, the analysis and characterisation of structural phenomena is key for the deviation of mechanical models and strongly depends on experimental studies. For this reason, the development of new measurement techniques plays a crucial role in research to allow capturing the mechanical behaviour of structures. In this context, distri...

In civil engineering, carbon is typically regarded as a modern material to serve as reinforcement in concrete structures. Compared to steel reinforcement, it features two substantial benefits: It is not sensitive to corrosion, and has an enormously increased tensile strength. In contrast, carbon reinforcement is sensitive to lateral pressure and la...

In diesem Beitrag werden Entwicklungen im Bereich der aktuellen Normung vorgestellt. Angesichts neuartiger Baustoffe und Bauprodukte sind Ingenieurmodelle zunächst in Bemessungsmodelle zu überführen. Hierbei sind Teilsicherheitsbeiwerte erstmalig festzulegen. Statistisch abgesicherte Teilsicherheitsbeiwerte sind bei fehlenden baupraktischen Erfahru...

Carbon textile reinforced concrete is a composite material made of a cementitious matrix and carbon fabrics that is being increasingly used in different structural applications. The unique properties of carbon reinforcement, such as its light weight, corrosion resistance and superior tensile strength, enable thin, material-efficient, and high-perfo...

Für die zweiten Generation von Eurocode 2 (prEC2) wurden neue Bemessungsregeln für Verankerungen und Übergreifungen von geraden Stäben erarbeitet. Diese neuen Regeln basieren auf dem Model Code 2010 mit dem zugehörigen Hintergrunddokument und unterscheiden sich grundlegend von den Regelungen des aktuellen Eurocode 2 (EC2) sowie dem zugehörigen nati...

Concrete bridges with low shear reinforcement ratios erected in the mid‐20th century are subjected to rapidly increasing traffic loads in the last decades. In the absence of precise methods for assessing the remaining service life, the detection of the slightest damage (e.g., cracks and corrosion) immediately leads to a partial or complete restrict...

Der Durchstanznachweis stellt bei der Bemessung von punktförmig gestützten Platten infolge der konzentrierten Lasteinleitung oftmals den maßgebenden Nachweis dar. Dabei ist in der Regel der Einfluss zusätzlich wirkender Biegemomente zu berücksichtigen. Während das Durchstanzen zentrisch belasteter Platten vielfach untersucht wurde, liegen zu exzent...

//english// Due to the demand for slender and functional buildings, flat slabs are a frequently used load-bearing element in building structures. Their slim design allows for efficient and variable floor design and thus sustainable use of buildings. However, the slab-column connection is often a governing detail in design due to concentrated load a...

The fatigue behavior of concrete has been usually investigated experimentally for loading scenarios with constant amplitudes. However, in reality the concrete components and structures such as wind turbine towers are subjected to loading scenarios with variable amplitudes. The existing design rules inadequately account for the effects of amplitude...

New design provisions for anchorage and lap design, based on Model Code 2010 and the related background document, have been proposed for the next generation of Eurocode 2 (prEC2). In this article, the new provisions are examined and compared with the provisions in current Eurocode 2 (EC2). In the first of the three parts of this study, design examp...

The determination of the maximum shear capacity of reinforced concrete (RC)-beams and slabs has been a challenging task for more than 100 years. To gain deeper insights into the shear capacity of RC members and to search for a mechanical solution to determine the ultimate capacity and to explain the phenomen of one-way shear, the so-called Shear Cr...

The fatigue behavior of concrete has been usually investigated experimentally for loading scenarios with constant amplitudes. However, in reality, concrete components and structures such as wind turbine towers are subjected to loading scenarios with variable amplitudes. Current design rules insufficiently capture the effect of amplitude changes and...

The development of restraint-induced stress in reinforced concrete members at an early age can be tested using setups applying either passive or active displacement control. To provide results relevant for the practical design of minimum reinforcement to limit the crack width, an actively controlled test setup for large specimens was developed to p...

Textile CFRP (carbon fibre reinforced polymer) reinforcement enables the construction of thin-walled structures such as double-curved shell structures or girder webs with minimal concrete cover due to their insensitivity to corrosion. In contrast to the tensile and flexural behaviour, the capacity of the compression strut of the thin-walled carbon...

In this paper, a novel 3D printing process for reinforced concrete structures called Additive Manufacturing of Reinforced Concrete (AMoRC) is proposed. The process consists of a continuous concrete extrusion process and an intermittent stud welding process, both carried out by a robotic arm respectively. The welding robot runs ahead of the concrete...

Within the scope of the collaborative research center CRC/TRR280 “Design strategies for material-minimized carbon reinforced concrete structures”, interdisciplinary researchers from TU Dresden, RWTH Aachen University and the Leibniz Institute of Polymer Research Dresden (Leibniz-Institut für Polymerforschung Dresden e. V.; IPF) mutually investigate...

This publication presents a digital image correlation (DIC) based technique applied to a shear test on a carbon-reinforced concrete member. DIC methods are based on image sequences where the first image is recorded under zero-load without deformations while further images are taken from deformed stages. The image processing starts with the computat...

Fatigue of plain concrete has been extensively researched for many years. Traditionally, investigations have focused mainly on compressive or tensile loading and little attention has been paid to shear loading (mode II). However, this type of loading has the advantage of providing precise load determination and a small, well-defined fracture surfac...

Shear behavior of reinforced concrete (RC) structures has been of particular interest in research for more than 100 years. Although many experimental campaigns have already been conducted, most of the tested specimens were simply supported, single span beams with concentrated loads. Thus, they are highly overrepresented in databases used for calibr...

During the past decades, significant advances have been made in the field of structural design and the use of probability-based safety methods. The motivation to use such methods is clear: By conducting probability-based analyses, designers can propose more comprehensive design models due to the exploitation of reserves, while simultaneously guaran...

The punching shear behavior of flat slabs has been mainly investigated on isolated specimens since experiments on continuous flat slab systems are expensive and complex. However, isolated specimens represent only the hogging moment area around the slab-column connection and thus neglecting system influences occurring in continuous slabs. The small...

A realistic prediction of the fatigue life of concrete under high-cycle loading scenarios with variable amplitudes is of utmost importance for a reliable and economically efficient design of structural infrastructures for transportation and energy supply. Current design codes estimate fatigue life under variable amplitudes using the Palmgren-Miner...

Composite dowels are an economically and technically reasonable alternative to the conventional shear connectors, the headed studs. However, their competitiveness is limited by the fact that they are only approved nationally and for a limited period of time, whereas headed studs are firmly anchored in European regulations. Numerous investigations,...

While the punching shear behavior of centrically loaded footings has been investigated in the past, the influence of unbalanced moments has remained almost uninvestigated for footings. Nevertheless, unbalanced moments are also transferred into the column by shear stresses requiring consideration in punching shear design. Here, design approaches oft...

The broad use of composite dowels as shear connectors in multi-span steel and concrete composite members is currently hindered by insufficient regulations for hogging moment regions, where the connectors are located in cracked concrete slabs and have reduced shear resistance. This paper reports on the results of three beam tests that illustrate the...

The second generation of Eurocode 2 incorporates formulations based on physical models which are general enough for the assessment of existing structures but can be simplified for the design of new structures, in order to improve the ease-of-use. One of the areas where these improvements are addressed is the shear verification of members without sh...

Semi‐precast slabs, where lattice girders serve both as reinforcement in the construction and in the final state, are characterized by a high flexibility and cost efficiency. Due to their technical and economic advantages, they are widely employed in constructions all over the world. In Germany, for example, they are used in about 70% of all floor...

Punching shear-reinforced flat slabs can fail in three modes: (i) inside the shear-reinforced zone, (ii) outside the shear-reinforced zone, or (iii) at the maximum punching shear capacity. By using the theory of structural systems reliability, this study investigates how these failure modes combined affect the safety level of reinforced concrete fl...

Der Durchstanznachweis stellt bei der Bemessung von Flachdecken infolge der konzentrierten, punktförmigen Lasteinleitung oftmals den konstruktiv bestimmenden Nachweis dar. Bei unregelmäßigen Deckensystemen oder Belastungen treten zudem ungleichmäßige Schubspannungsverteilungen im Durchstanzbereich auf. In der Tragwerksplanung stellt sich hierbei of...

Flexural shear behavior, which mainly concerns reinforced concrete (RC) slabs without shear reinforcement, is usually investigated by means of simply supported, beam‐shaped specimens. Only few tests are available where the cross‐section properties correspond to a slab (b ≫ h) or the support conditions lead to moment and shear force distributions of...

Tragwerke aus Carbonbeton sind insbesondere dann wirtschaftlich, wenn die Carbonbewehrung zum Vorspannen des Betons genutzt werden kann. Die Erfolgsgeschichte des Spannbetons basiert auf der Verwendung hochfesten Spannstahls, der es ermöglicht, dauerhaft hohe Vorspannkräfte in den Beton einzuleiten. Der Übergang vom Spannstahl zum festeren, leichte...

In den folgenden Abschnitten werden die Grundlagen des Bewehrens behandelt. Es werden Hilfestellungen und Bemessungsregeln vorgestellt. Im ersten Abschnitt werden die allgemeinen Konstruktionsdetails beschrieben. Dabei wird insbesondere auf die Wahl der Bewehrung und auf den Herstellungsprozess der bewehrten Betonbauteile eingegangen. Im zweiten Te...

Für Bauwerke wird in der Regel eine Lebensdauer von mehreren Jahrzehnten angestrebt. Entsprechend dauerhaft leistungsfähig müssen die verwendeten Materialien sein. Kapitel 9 beginnt mit einer kurzen Einführung in die Grundlagen des Ermüdungsverhaltens von Werkstoffen. Anschließend werden das Dauerstand‐ und das Ermüdungsverhalten von Carbon und Bet...

In Kapitel 7 werden die Nachweiskonzepte im Grenzzustand der Tragfähigkeit (GZT) behandelt. Ausgehend von den Prinzipien des Sicherheitskonzepts werden zunächst die Herleitung von Bemessungswerten des Bauteilwiderstandes und von Teilsicherheitsbeiwerten für Bauteile aus Carbonbeton erläutert. Danach wird auf die Ermittlung der Robustheitsbewehrung...

Structural behavior of reinforced concrete elements strongly depends on the interaction between the reinforcing bars and the surrounding concrete, which is generally referred as “bond in concrete”. In service conditions, the reinforcement-to-concrete bond governs deformability through the tension stiffening of concrete surrounding the bar as well t...

Structural behavior of reinforced concrete elements strongly depends on the interaction between the reinforcing bars and the surrounding concrete, which is generally referred as “bond in concrete”. In service conditions, the reinforcement-to-concrete bond governs deformability through the tension stiffening of concrete surrounding the bar as well t...

The fatigue of concrete has been the subject of research for many years, and yet, there are still open questions. In particular, the fatigue-induced damage evolution accompanied by a stress redistribution process propagating through the concrete structure is still not fully understood. So far, there are only few experimental studies addressing the...

The development of lightweight, high-performance cementitious composite materials such as carbon concrete has triggered the need for innovative design and construction methods for thin-walled structural elements with an optimal material utilization. Combining the material efficiency of carbon concrete with the form flexibility provided by parameter...

The punching shear behavior of flat slabs has been investigated in the past mainly on flat slab cutouts since experiments on continuous flat slab systems are expensive and complex. However, these cutouts represent only the hogging moment area around the slab-column connection and thus neglect system influences such as moment redistribution between sagg...

Das Verbundverhalten zwischen Stahl und Beton ist essenzieller Bestandteil für die Tragfähigkeit von Stahlbetonbauteilen. Der Verbund zwischen beiden Werkstoffen stellt sicher, dass die Stahlzugkräfte im Beton verankert bzw. zwischen Bewehrung und Beton übertragen werden können. Für die Bemessung und Konstruktion von Stahlbetonbauteilen liegt ein b...

The potential of textile-reinforced concrete is broad: it can be used in new structures and in the retrofitting of existing structural components. Designing textile-reinforced concrete requires knowledge about the mechanical properties of different textile types. To this, a standardised tensile test for fibre strands was used. The test aims to stat...

In the last decades, modern technological and research developments of textile-reinforced concrete have led to extensive applications in building and civil engineering structures all over the world. Examples of textile-reinforced concrete can be found in retrofitting of existing buildings, facade slabs or bridges. Despite its potential, the widespr...

Structures under repeated loading may fail prematurely due to fatigue of the interface between concrete and reinforcement. In this study, an experimental program is presented studying the bond behavior between normal-strength concrete and steel reinforcement under compressive monotonic and high cycle fatigue loading. Modified beam-end tests have be...

In the latest draft of the second generation of EC2 (prEC2), new design rules for anchorages and laps of straight bars are proposed. These new rules are based on ModelCode 2010 and the supporting background document. For the official enquiry phase, which ended in December 2021, the new design rules were reviewed and the results of these studies are...

Although part of every existing and new structural concrete member, necessary bond lengths are still an object of research on structural concrete. This paper presents the experimental investigation of reinforcement laps and the derivation of an empirical design model for the necessary lap length. To analyse the bearing capacity of reinforcement lap...

Die ungünstige Altersstruktur der Bundesfernstraßen in Deutschland und die erhebliche Zunahme des Güterverkehrs sind die wesentlichen Gründe für den allgemein schlechten Gesamtzustand zahlreicher Brückenbauwerke. Zusätzlich ergeben sich durch die Weiterentwicklung der Normen in Verbindung mit den Eurocodes häufig rechnerische Defizite. Genauere Nac...

Reinforced concrete is the most widely used building material today. It can be produced universally and cheaply almost anywhere in the world. However, this is accompanied by high CO2 emissions and considerable consumption of natural resources. In the DFG Priority Programme 1542, a wide variety of approaches were therefore investigated to find out h...

Given the recent developments in increasing road traffic and the limited capacities of the road networks in many countries, the necessity for durable and long-lasting roads with low maintenance is of outmost importance. This leads to a rethinking of typical construction methods in which continuously reinforced concrete roads (CRCP) provide an alter...

Flachdecken sind eine heute oft ausgeführte Konstruktionsform im Hoch‐ und Industriebau, die zu Beginn des 20. Jahrhunderts erstmals angewendet wurde. Flachdecken ermöglichen vor allem flexibel und nachhaltig nutzbare Gebäudestrukturen, die maßgeblich zur Verlängerung der Gesamtnutzungsdauer beitragen. Das durch die punktförmige Lagerung verursacht...

Despite extensive research in the past few decades, design of beams without shear reinforcement is still considered to be a challenging task. With the goal to provide realistic and simple engineering models many researchers have contributed to the development of analytical and numerical approaches that improved our understanding of the mechanical b...