Fakultät Architektur und Bauingenieurwesen

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http://hdl.handle.net/2003/39260

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Retrofitted building skins – Energetische Optimierung der Gebäudehülle im Bestand
(2022-07-19) Albus, Jutta; Rehnig, Lena
Um das Klimaziel der Bundesregierung zu erreichen, gilt die energetische Optimierung im Gebäudesektor als eine übergeordnete Aufgabe, die nicht nur die Erstellung neuer Gebäude, sondern auch die Ertüchtigung des Gebäudebestands betrifft. Gegenstand der Forschungs- und Lehrtätigkeiten des Lehrgebiets bilden Entwurfsentwicklungen, die durch innovative Gebäudehüllen und Fassadentechnologien einen nachhaltigen und ressourcenschonenden Beitrag auch für den hohen Anteil von Bestandsgebäuden leisten. Sanierungs- und Instandhaltungsmaßnahmen werden vor dem Hintergrund energetischer Optimierungsstrategien, nachhaltiger Gebäudekonzeption und ressourcenschonendem Materialeinsatz entwickelt und fokussieren dabei aktive und passive Maßnahmen. Dabei soll insbesondere der Anteil von bestehenden Büro- und Verwaltungsbauten betrachtet werden, der neben dem Wohngebäudebestand ein erhebliches Potential zur Reduzierung von CO2-Emissionen aufzeigt.
Experimental investigations of power-actuated fastenings in TRC
(2023-04-18) Langenbeck, A.D.; Spyridis, P.; Beßling, M.; Orlowsky, J.
In this study we investigate the application of direct fastenings in textile-reinforced concrete for the first time in international research. This efficient combination is promising regarding sustainability and load-bearing reliability due to the fine-grained material structure. We aim to assess the system's feasibility and establish the most favourable framework of practice. Within our test series, we modify the concrete strength, the number of textile layers, the type of textile and the setting process. The most promising results were achieved when using three layers of a symmetric textile regarding geometry and tensile strength without executing a predrilling. While using higher-strength concrete leads to a total load-bearing capacity of up to 7 kN, this implies lower visual quality compared to lower-strength concrete. The latter case, with an average nail performance of over 4 kN, indicates that the proposed fastening-material-combination is highly promising regarding future use cases.
Database of tunnel collapses and failures
(2023-03-17) Spyridis, Panagiotis; Mitroulis, Konstantinos; Proske, Dirk
This database contains data of collapses in tunnels during construction or operation and cases of extensive maintenance signifying the end of service life. It can form the basis for statistical interpetations as well as hisotrical review of various tunnel projects. This database also forms the basis for the investigations reported in the papers "Revised Comparison of Tunnel Collapse Frequencies and Tunnel Failure Probabilities" by P. Spyridis and D. Proske (DOI:10.1061/AJRUA6.0001107) and "Assessing the failure potential of tunnels and the impacts on cost overruns and project delays" by C. Paraksevopoulou, M. Dallavalle, S. Konstantis, P. Spyridis, A. Benardos (DOI:10.1016/j.tust.2022.104443)
Minimally invasive retrofitting of RC joints with externally applied SMA plate - adaptive design optimisation through probabilistic damage simulation
(2023-02-20) Molod, Mohammad Amin; Barthold, Franz-Joseph; Spyridis, Panagiotis
Beam–column joints are the critical section of many reinforced concrete (RC) structure types in which any failure could lead to the collapse of the entire structure. This paper attempts to employ a superelastic shape memory alloy plate as an innovative and adaptive external strengthening element to rehabilitate existing concrete beam–column joints and enhance the structure’s performance. An experimentally investigated beam–column joint is used as the case study, and it is investigated numerically to validate the effects of an innovative strengthening technique based on shape memory alloys. The results show that the proposed technique could increase the joint’s stiffness and reduce the risk of overall failure. A particular innovation in the proposed method is associated with the novel material itself but also with the fact that the increased potential costs of using special alloys are counteracted by its potential to produce these elements in an optimised industrially produced fastened plate. This fits-all construction product further allows a rapid and minimally invasive strengthening technique. Moreover, to achieve this, the plate is adaptively designed against random critical load combinations through probabilistic damage prediction.
Effect of the umbrella arch technique modelled as a homogenized area above a cross passage
(2023-01-26) Siad, Ibtissem; Akchiche, Mustapha; Spyridis, Panagiotis
The stability of tunnel cross passages excavated in soft soil has always been a major challenge. In recent years, new techniques based on the installation of pre-reinforcements before tunnel excavation have been developed to control excavation-induced deformation and surface settlements. In this paper, a finite element numerical simulation was conducted to study the reduction effect of an umbrella vault element modelled as a homogenized area on the deformations induced after the excavation of a cross passage. The results of this study show that the ground deformations can be controlled efficiently by using this type of pre-reinforcement. However, the findings showed that there is no effect of the umbrella arch length on the reduction of the ground deformations. This paper represents a very good demonstration of 3D modelling of tunnel junctions using pre-support techniques; it is the most advanced/appropriate research tool for studying the behaviour of cross passages and is useful as a paradigm for other researchers and practitioners.
Database of experimental results from punching shear tests with various types of reinforcement
(2023-01-31) Spyridis, Panagiotis; Mellios, Nikolaos; Uz, Okan; Walter, Lars
Direct slabs-column connections are a typical structural confgiuration because they allow greater clear heights and more versatile architectural layouts compared to beam frame support. In such structures, punching shear failure is often critical. Punching shear is characteristically brittle and it occurs without pronounced advance notice, whilst robustness through alternative load paths can not always be ensured. Hence progressive catastrophic collapses can occur and advanced design and existing structures assessment models are necessary. This dataset is a collection of available full-scale punching shear test results from international literature of the last 6 decades offered to researchers for metanalyses and comparisons with own research results. This also forms the basis of the publication: Mellios, N., Uz, O., & Spyridis, P. (2023). Data-based modeling of the punching shear capacity of concrete structures. Engineering Structures, 275, 115195.
Comparative study on the efficiency of simulation and meta-model-based Monte Carlo techniques for accurate reliability analysis of corroded pipelines
(2022-05-11) Seghier, Mohamed El Amine Ben; Spyridis, Panagiotis; Jafari-Asl, Jafar; Ohadi, Sima; Li, Xinhong
Estimation of the failure probability for corroded oil and gas pipelines using the appropriate reliability analysis method is a task with high importance. The accurate prediction of failure probability can contribute to the better integrity management of corroded pipelines. In this paper, the reliability analysis of corroded pipelines is investigated using different simulation and meta-model methods. This includes five simulation approaches, i.e., Monte Carlo Simulation (MCS), Directional Simulation (DS), Line Sampling (LS), Subset Simulation (SS), and Importance Sampling (IS), and two meta-models based on MCS as Kriging-MCS and Artificial Neural Network based on MCS (ANN-MCS). To implement the proposed approaches, three limit state functions (LSFs) using probabilistic burst pressure models are established. These LSFs are designed for describing the collapse failure mode for pipelines constructed of low, mid, and high strength steels and are subjected to corrosion degradation. Illustrative examples that comprise three candidate pipelines made of X52, X65, and X100 steel grade are employed. The performance and efficiency of the proposed techniques for the estimation of the failure probability are compared from different aspects, which can be a useful implementation to indicate the complexity of handling the uncertainties provided by corroded pipelines.
Tensile performance of headed anchors in steel fiber reinforced and conventional concrete in uncracked and cracked state
(2022-03-03) Spyridis, Panagiotis; Mellios, Nikolaos
Steel fiber reinforced concrete (SFRC) is currently the material of choice for a broad range of structural components. Through the use of SFRC, the entire, or a large portion of, conventional rebar reinforcement can be replaced, in order to improve the load-bearing behavior but also the serviceability and durability characteristics of engineering structures. The use of fiber reinforcement therefore plays a vital role in acute current and future construction industry objectives, these being a simultaneous increase in the service life of structures and the reduction of their environmental impact, in addition to resilience to extreme loads and environmental actions. Next to the extended use of SFRC, modern construction relies heavily on structural connections and assembly technologies, typically by use of bolt-type cast-in and post-installed concrete anchors. This paper addresses the influence of fiber reinforcement on the structural performance of such anchors in SFRC and, particularly, the load bearing behavior of single headed anchors under axial static loads in uncracked and cracked concrete. Along with a presentation of background information on previous studies of SFRC with a focus on anchor concrete breakout failure, the experimental investigations are described, and their results are presented and elaborated on by consideration of various research parameters. A comparison with current design approaches is also provided. The conclusions are deemed useful for structural engineering research and practice.
Probabilistic studies on the shear strength of slender steel fiber reinforced concrete structures
(2020-10-04) Olalusi, Oladimeji B.; Spyridis, Panagiotis
Shear failure is a brittle and undesirable mode of failure in reinforced concrete structures. Many of the existing shear design equations for steel fiber reinforced concrete (SFRC) beams include significant uncertainty due to the failure in accurately predicting the true shear capacity. Given these, adequate quantification and description of model uncertainties considering the systematic variation in the model prediction and measured shear capacity is crucial for reliability-based investigation. Reliability analysis must account for model uncertainties in order to predict the probability of failure under prescribed limit states. This study focuses on the quantification and description of model uncertainty related to the current shear resistance predictive models for SFRC beams without shear reinforcement. The German (DAfStB) model displayed the lowest bias and dispersion, whereas the fib Model 2010 and the Bernat et al., model displayed the highest bias and dispersion. The inconsistencies observed in the resistance model uncertainties at the variation of shear span to effective depth ratio are a major cause for concern, and differentiation with respect to this parameter is advised. Finally, in line with the EN 1990 semi-probabilistic approach for reliability-based design, the global partial safety factors related to model uncertainties in the shear resistance prediction of SFRC beams are proposed.

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