TY - JOUR A1 - Luong, Thi Mai Hoa A1 - Zabel, V. A1 - Lorenz, W., A1 - Rohrmann, R.G., T1 - Vibration-based model updating and identification of multiple axial forces in truss structures 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 PY - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-402263 SN - 1877-7058 VL - 188 SP - 385 EP - 392 PB - Elsevier AN - OPUS4-40226 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CHAP A1 - Luong, Thi Mai Hoa A1 - Lorenz, W. A1 - Rohrmann, R.G. A1 - Zabel, V. A1 - Said, Samir ED - Springer, Cham, T1 - Finite Element Model Calibration of a Historic Wiegmann–Polonceau Truss Based on Experimental Modal Parameters 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 - Modal parameters KW - Axial force KW - Dynamic test KW - Finite element method KW - Truss structures PY - 2017 SN - 978-3-319-67443-8 U6 - https://doi.org/10.1007/978-3-319-67443-8_18 SN - 2366-2557 VL - 5 SP - 212 EP - 224 PB - Springer International Publishing ET - 1 AN - OPUS4-42524 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Luong, Thi Mai Hoa A1 - Zabel, V. A1 - Lorenz, W. A1 - Rohrmann, R.G. T1 - Non-destructive assessment of the axial stress state in iron and steel truss structures by dynamic measurements 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. T2 - X International Conference on Structural Dynamics, EURODYN 2017 DA - 10.09.2017 KW - Axial force KW - Dynamic test KW - Model updating KW - Optimization technique KW - Truss structures KW - Modal parameters PY - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-419311 SN - 1877-7058 VL - 199 SP - 3380 EP - 3385 PB - Elsevier AN - OPUS4-41931 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -