TY - GEN A1 - Fischer, Michael A1 - Lorenz, Werner T1 - Stahlbau unter Denkmalschutz - Grundinstandsetzung von Viadukt und Bahnhöfen der Hochbahnlinie U2 in Berlin-Prenzlauer Berg T2 - Stahlbau Y1 - 2011 U6 - https://doi.org/10.1002/stab.201101446 SN - 0038-9145 VL - 80 IS - 6 SP - 419 EP - 427 ER - TY - GEN A1 - Luong, Thi Mai Hoa A1 - Zabel, Volkmar A1 - Lorenz, Werner A1 - Rohrmann, Rolf G. T1 - Vibration-based Model Updating and Identification of Multiple Axial Forces in Truss Structures T2 - Procedia Engineering N2 - Safety assessment of existing iron and steel truss structures requires the determination of the axial forces and corresponding stresses in truss structural members. The results of the axial force determination can be integrated as part of a structural health monitoring scheme for existing trusses. In this work, a methodology is proposed to identify multiple axial forces in members of a truss structure based on the modal parameters. Vibration test allows the identification of the natural frequencies and mode shapes, globally of the truss structure as well as locally of the individual bars. The method calibrates the numerical model of the truss structure using a genetic algorithm and strategic validation criteria. The validation criteria are based on the identified natural frequencies and global mode shapes of the truss structure as well as information of the axial forces in the individual bars of the truss, which are estimated from the natural frequencies and five amplitudes of the corresponding local mode shapes of the single bars based on an analytical-based algorithm. The calibration allows the identification of the axial forces in all bars of the truss structure. For mode pairing strategy, a technique makes use of the enhanced modal assurance criteria with the calculation of the modal strain energies. Moreover, the modal strain energies are also used to select the relevant local mode shape of the individual bars. The feasibility and accuracy of the proposed methodology is verified by laboratory experiments on several truss structures. In situ tests on existing trusses are intended. The results from one of the laboratory tested structures, i.e. a two-bar system, are included in this paper. KW - Truss structures KW - axial force KW - dynamic test KW - model updating KW - optimization technique Y1 - 2017 U6 - https://doi.org/10.1016/j.proeng.2017.04.499 SN - 1877-7058 VL - 188 SP - 385 EP - 392 ER - TY - GEN A1 - Kurrer, Karl-Eugen A1 - Lorenz, Werner T1 - Bautechnikgeschichte in Deutschland T2 - Bautechnik Y1 - 2017 U6 - https://doi.org/10.1002/bate.201600098 SN - 0932-8351 VL - 94 IS - 5 SP - 274 EP - 294 ER - TY - GEN A1 - Luong, Thi Mai Hoa A1 - Zabel, Volkmar A1 - Lorenz, Werner A1 - Rohrmann, Rolf G. T1 - Non-destructive Assessment of the Axial Stress State in Iron and Steel Truss Structures by Dynamic Measurements T2 - Procedia Engineering N2 - This paper is concerned with the inverse identification of the stress state in axially loaded slender members of iron and steel truss structures using measured dynamic data. A methodology is proposed based on the finite element model updating coupled with nature-inspired optimization techniques, in particular the particle swarm optimization. The numerical model of truss structures is calibrated using natural frequencies and mode shapes from vibration tests, as well as additional information of the axial forces in selected truss members based on the experimentally identified modal parameters. The results of the identification are the axial forces or corresponding stresses in truss structures and the joint rigidity in relation to pinned and rigid conditions. Attention is given to several examined aspects, including the effects of the axial tensile and compressive forces on the dynamic responses of trusses, mode pairing criteria, as well as modeling assumptions of joints and the use of a joint rigidity parameter. Considering the pairing of modes, it is performed by adapting an enhanced modal assurance criterion that allows the selection of desired clusters of degrees-of-freedom. Thus, information extracted from the measurements related to specific modes is utilized in a more beneficial way. For modeling of joints, the numerical model of a truss structure includes rotational springs of variable stiffness to represent semi-rigid connections. Moreover, a fixity factor is introduced for practical estimation of the joint flexibility. The effectiveness of the proposed methodology is demonstrated by case studies involving simulated and laboratory experimental data. KW - Lightweight truss structures KW - stress state KW - modal parameters KW - finite element model updating KW - nature-inspired optimization technique Y1 - 2017 U6 - https://doi.org/10.1016/j.proeng.2017.09.447 SN - 1877-7058 VL - 199 SP - 3380 EP - 3385 ER - TY - CHAP A1 - Luong, Thi Mai Hoa A1 - Lorenz, Werner A1 - Rohrmann, Rolf G. A1 - Zabel, Volkmar A1 - Said, Samir T1 - Finite Element Model Calibration of a Historic Wiegmann–Polonceau Truss Based on Experimental Modal Parameters T2 - Experimental Vibration Analysis for Civil Structures: Testing, Sensing, Monitoring, and Control N2 - This paper describes the experimental calibration of an existing Wiegmann–Polonceau roof truss based on modal parameters. Dynamic tests allowed the determination of the natural frequencies and mode shapes of the global truss and of individual truss members. The global and local modal configurations as well as coupled vibration of truss members are discussed. In addition, as truss members are axially loaded, the effect of stress stiffening on the modal parameters is considered. Moreover, several finite element models with different modelling assumptions for the details of the connections and member geometrical characteristics such as gusset plates and turnbuckles were developed. A suitable numerical model was chosen to represent the truss structural behavior. This paper focuses on the local measurement and analysis strategies applied to single truss members. The possibility of using a local analysis method, namely methods that consider individual members as part of a structure, is demonstrated to assess the behavior of the global truss structure. The comparison of the results after calibration reveals a very good correlation between the experimentally identified and numerically estimated modal parameters of the historic truss. KW - Historic truss structures KW - Coupled vibration KW - Stress stiffening KW - Modal analysis KW - Finite element model calibration Y1 - 2017 SN - 978-3-319-67443-8 U6 - https://doi.org/10.1007/978-3-319-67443-8_18 SP - 212 EP - 224 PB - Springer International Publishing CY - Cham ER - TY - CHAP A1 - Lorenz, Werner T1 - "Vom Nutzen und Nachtheil der Historie für das Leben" Geschichte für Bauingenieure? T2 - Zehn Jahre Historische Wahrzeichen der Ingenieurbaukunst in Deutschland : Festschrift Y1 - 2017 SN - 978-3-941867-29-1 SP - 36 EP - 49 PB - Bundesingenieurkammer CY - Berlin ET - 1. Auflage ER - TY - CHAP A1 - Lorenz, Werner A1 - Heinzelmann, Dorothee A1 - Heinzelmann, Michael T1 - Das Bronzedachwerk der Vorhalle des Pantheons in Rom T2 - Bericht über die 49. Tagung für Ausgrabungswissenschaft und Bauforschung vom 4. bis 8. Mai 2016 in Innsbruck Y1 - 2017 SN - 978-3-945363-75-1 SP - 148 EP - 155 PB - Thelem CY - Dresden ET - 1. Auflage ER - TY - CHAP A1 - Lorenz, Werner A1 - Heres, Bernhard ED - Rheidt, Klaus ED - Lorenz, Werner T1 - Tüfteln-Testen-Besser machen. Die Großbaustelle Eremitage um 1840 T2 - Groß Bauen: Großbaustellen als kulturgeschichtliches Phänomen Y1 - 2018 SN - 978-3-0356-1157-1 SP - 133 EP - 146 PB - Birkhäuser Verlag CY - Basel ER - TY - CHAP A1 - Rheidt, Klaus A1 - Lorenz, Werner ED - Rheidt, Klaus ED - Lorenz, Werner T1 - Vorwort T2 - Groß Bauen: Großbaustellen als kulturgeschichtliches Phänomen KW - Großbaustellen KW - Baugeschichte KW - Bauforschung Y1 - 2018 SN - 978-3-0356-1157-1 SP - 7 EP - 11 PB - Birkhäuser Verlag CY - Basel ER - TY - CHAP A1 - Lorenz, Werner ED - Pelke, Eberhard ED - Brühwiler, Eugen T1 - What is construction history? T2 - Engineering History and Heritage Structures - Viewpoints and Approaches Y1 - 2017 SN - 978-3-85748-154-3 SP - 11 EP - 12 PB - IABSE CY - Zürich ER -