Steel-fibre reinforced concrete in compo-site structures as a mean to increase re-sistance and ductility

in Stahlbau (2022), 91(12), 801-811

Steel-fibre reinforced concrete is a well-known material used for decades for industrial floorings, shot-crete, or other specific applications. Its use is now spreading in structural applications as a ... [more ▼]

Steel-fibre reinforced concrete is a well-known material used for decades for industrial floorings, shot-crete, or other specific applications. Its use is now spreading in structural applications as a complement or a substitute for conventional bar-reinforced concrete since the normative framework is ready to provide design approaches for several concrete applications. Nevertheless, some adaptations are needed for implementing steel-fibre reinforced concrete in the design approach for steel-concrete composite struc-tures whereby complementary aspects need to be considered. In this field, besides the increase of tensile properties and durability of the concrete member, a very important contribution may be given by the in-crease of the concrete ductility in compression. This property is conferred by the steel fibres which pro-vide a confinement effect increasing the plastic damage that the concrete matrix can absorb. If this prop-erty is widely accepted, its benefits are limited for the design of conventional concrete sections. Con-versely, for composite sections, the possibility to reach higher strains in compression means ensuring full exploitation of the strength capacity of structural steel. Besides reaching an optimization of already in-use cross-sections, this new material combination enhances the use of higher structural steel strengths in composite structures. [less ▲]

Determination of Slip Factor between CNC-Cut Serrated Surfaces of S355J2 Grade Steel Plates

in Buildings (2022), 12(995),

Determination of Slip Factor between CNC-Cut Serrated Surfaces of S355J2 Grade Steel Plates by Taygun Fırat Yolaçan and Markus SchäferStructural joint configurations realized with serrated steel surfaces ... [more ▼]

Determination of Slip Factor between CNC-Cut Serrated Surfaces of S355J2 Grade Steel Plates by Taygun Fırat Yolaçan and Markus SchäferStructural joint configurations realized with serrated steel surfaces have started to be used in the construction fields to assemble the primary and the secondary structural members of civil engineering structures. The main advantages of these joint configurations rely on their flexibility to accommodate construction tolerances and their slip-resistant load-bearing mechanism against dynamic loading conditions. Therefore, it is important to reliably establish the characteristic value of the friction coefficient or in other words the slip factor between the serrated steel surfaces to design reliable slip-resistant connections. In this study, the characteristic slip factor between the CNC-cut serrated surfaces prepared from S355J2 grade steel plates is determined to investigate the impact of the CNC-cutting procedure on the slip-resistant load-bearing behaviour of steel-to-steel interfaces. Five experimental tests were performed according to EN1090-2, Annex G. The results are presented as the load-slip curves, variation of the bolt pre-tension load level, nominal and actual slip factors for the tested configuration of the CNC-cut serrated steel-to-steel interface [less ▲]

Slim-Floor Bauweise – Bemessung und Ausführung

Presentation (2022, March 29)

Integration of design for shallow floor beam in prEN1994-1-1; design and construction for shallow floor construction

Bridge damage assessment based on static and dynamic flexibility matrices

in Bridge Safety, Maintenance, Management, Life-Cycle, Resilience and Sustainability (2022)

Being an indispensable part of transportation systems, Structural Health Monitoring (SHM) of bridges has been increasingly studied. Various SHM techniques not only enhance reliability and safety but also ... [more ▼]

Being an indispensable part of transportation systems, Structural Health Monitoring (SHM) of bridges has been increasingly studied. Various SHM techniques not only enhance reliability and safety but also reduce maintenance costs. Various bridge deteriorations change the structural properties, such as flexibility and stiffness. Therefore, damage assessment can be achieved by monitoring the structural matrices of bridges and tracking the deviations from the healthy-state or reference data. This paper focuses on damage detection of a prestressed concrete beam from a demolished bridge based on the flexibility matrix. The dynamic and static flexibility matrices are calculated numerically and experimentally when the beam is undamaged. The simulated and measured static flexibility matrices differ by only about 5 %. Additionally, the numerical dynamic flexibility matrix is strongly correlated with static results. The findings of this study can be employed as a basis for future damage detection applications when artificial damage is introduced. [less ▲]

Draft for second generation of prEN 1994-1-1, November 2021

Report (2021)

Development of second generation for Eurocode 4, part 1: prEN 1994-1-1: November 2021- Draft + Respons on comments

Non-linear Analysis of Circular Composite Columns

in Burgess, Ian (Ed.) Special Issue: Proceedings of Eurosteel 2021: Sheffield - Steel's coming home (2021, September)

Composite columns provide many advantages for the application in multi-story and high-rise buildings. However, EN 1994-1-1 does not provide rules for the design of circular concrete sections with fully ... [more ▼]

Composite columns provide many advantages for the application in multi-story and high-rise buildings. However, EN 1994-1-1 does not provide rules for the design of circular concrete sections with fully encased steel profiles according to the simplified methods. Normally, the simplified method for the design of composite columns is based on a normal force-moment interaction diagram which assumes plastic cross-section resistance. However, the moment resistance is to be reduced by a reduction factor M, considering among other the difference between strain-limited and plastic moment resistance. This reduction factor is developed and calibrated for composite compression members with concrete encased sections, partially encased sections and concrete filled rectangular and circular tubes. Comparison of plastic moment resistance to results based on strain limitation show that the application for circular section with encased steel section but without a steel tube may lead to unsafe results. The paper discusses different approaches for the determination of the N-M Interaction curve and the design on cross-section level. The results obtained from these methods are then compared to each other for different dimensions of cross-sections of circular columns; and for different ratios of reinforcements, various steel grades and for normal and high strength concretes. Furthermore, the investigation focuses on the validation of the reduction factor alfa_M and shows for which section types the values according to Eurocode 4 cannot be applied. [less ▲]

Behavior of downstand simply supported steel-concrete composite beam applying friction based demountable shear connection

in Burgess, Ian (Ed.) Special Issue: Proceedings of Eurosteel 2021: Sheffield - Steel's coming home (2021, September)

In order to improve sustainability of composite structures and promote the principles of circular economy in construction industry, novel demountable shear connector based on the frictional behavior was ... [more ▼]

In order to improve sustainability of composite structures and promote the principles of circular economy in construction industry, novel demountable shear connector based on the frictional behavior was developed within the framework of Work package 2 of parent project ECON4SD (Eco Construction for Sustainable Development) at the University of Luxembourg. The demountable composite floor system is composed out of modular concrete one-way solid slabs with equidistantly embedded Halfen HTA-CE rail channels, double symmetric steel I section and demountable connector device assembly based on HV high strength structural bolts for preloading that provides the demountable shear connection. In this paper trilinear behavior model is proposed for the force-slip behavior of aforementioned connector device complying to the results of the push test experimental campaign and the results of FEA simulations. Afterwards, parametric study is performed on the range of simply supported composite beams in propped and unpropped condition under uniformly distributed load applying the aforementioned shear connection validating the predictability of the composite beam bending behavior in accordance with the rules of EN 1994-1-1. [less ▲]

Digitalization in Construction, Computer-based Design for Structural Elements - BIM and structural engineering - Part 1: Impact of digitalization on structural engineering in the future

Learning material (2021)

To better understand the background and complexity of BIM and digitalization within structural engineering, the theoretical approach will highlight the underlying basics first. To draw the line from this ... [more ▼]

To better understand the background and complexity of BIM and digitalization within structural engineering, the theoretical approach will highlight the underlying basics first. To draw the line from this theory driven basics to real live application, the thesis will give multiple examples of how BIM is currently used in practice. In addition to the detailed explanation, these examples will serve as a base to analyze the current situation and problems which still need to be overcome. As far as possible for the respective research scope, potential areas of improvements will be outlined. To gain a better understanding of the current importance of BIM and digitalization within the German construction industry, engineers and companies will be surveyed. [less ▲]

Non-linear design for composite structures in steel and concrete in reference to Eurocode 4, Part 1-1

Learning material (2021)

The design of composite structures in steel and concrete for buildings follows the rules according to Eurocode 4: EN 1994-1-1. In the last years more and more individual composite members and cross ... [more ▼]

The design of composite structures in steel and concrete for buildings follows the rules according to Eurocode 4: EN 1994-1-1. In the last years more and more individual composite members and cross-section types have been developed. Those sections are not always fulfilling the requirements for the application of simplified design methods given by EN 1994-1-1 and therefore plastic resistance cannot always be applied. Furthermore there is an increasing demand for optimization in the design by using more advanced design methods. This optimization is concentrating on the use of individual shaped cross-sections and their efficiency, the composite shear connectors and consideration of their ductility and flexibility, investigation in the sequence of loading, time effects as well as concrete cracking and yielding of steel within the analysis. In addition it is to be mentioned that the draft for the second generation of Eurocode 4 provides more opportunities for advanced numerical methods. At least, the demand for more advanced numerical design methods is permanently increasing also due to the availability of powerful hardware and software applications. The target of this chapter is to introduce the advanced numerical design for composite structural members in steel and concrete and to explain the boundary conditions given by Eurocode 4 and related Eurocodes. Thereby the focus is more on the member and not on the global analysis. The computer-aided global analyses for the determination of action effects are well-known for years while the possibilities for nonlinear analysis based on shell and volume elements considering physical and geometrical nonlinearity becoming more important and will be further developed in future. However, there is not so much information available explaining the application of e.g. the general method in detail and guidance is missing by the code. Therefore the general method acc. to EN 1994-1-1/prEN1994-1-1 is the main focus of this contribution. In the following, some principles for the design according to EN 1994-1-1 are explained. Thereby the basics for the classification of cross-sections as well as the determination of inner forces for continuous beams will be pointed out. However, the focus is on the general method for the design of composite compression members. While in the case studies additional information for the structural analysis and the numerical investigation in composite beams is provided. This chapter will not repeat well-known explanations from the literature, which have been published many times but limits itself to the most important normative fundamentals, rather concentrate on the application of numerical methods for the design of composite structures. More details for global structural analysis and the design according to EN 1994-1-1 [1] are provided by the literature, e.g. [8], [40] and will not be further commented here. It should be noted that the here referred methods according to prEN 1994-1-1, prEN 1993-1-14 and prEN 1992-1-1 do not represent officially introduced design standards, until the introduction of the second generation of Eurocodes modification is not finalized. Therefore this references are to be understood as informative. Until the introduction of the second generation of Eurocodes further changes and adjustments may also to be expected. [less ▲]

Limitations of plastic bending resistance for composite beams deviated from strain-limitation

in Journal of Constructional Steel Research (2021), 180(106562),

Due to the demand for sustainable constructions, composite structures have become more important and lead to slim and economic solutions with a low structural self-weight. EN 1994-1-1 distinguishes ... [more ▼]

Due to the demand for sustainable constructions, composite structures have become more important and lead to slim and economic solutions with a low structural self-weight. EN 1994-1-1 distinguishes between four different cross-section classes for the determination of moment resistance. For the plastic moment resistance, it is assumed, that each cross-sectional fibre can plastify without any limit on the strain. For standard composite beams with sagging moments and a high plastic neutral axis, plastic resistance and strain-limited resistance give similar results. For sections with a large compression zone height xpl and limited rotation capacity, concrete failure in the compression zone can occur before the plastic moment resistance Mpl,Rd, is reached. The strain limit design becomes critical. This paper points out the impact of the concrete part on the design of composite beams. A parametric study comparing plastic and strain limited moment resistance of a considerable variety of cross-sections has been carried out to develop the beam design methods considering compression zone height for the next generation of Eurocodes. [less ▲]