@article{AlkamLahmer, author = {Alkam, Feras and Lahmer, Tom}, title = {A robust method of the status monitoring of catenary poles installed along high-speed electrified train tracks}, series = {Results in Engineering}, volume = {2021}, journal = {Results in Engineering}, number = {volume 12, article 100289}, publisher = {Elsevier}, address = {Amsterdam}, doi = {10.1016/j.rineng.2021.100289}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20211011-45212}, pages = {1 -- 8}, abstract = {Electric trains are considered one of the most eco-friendly and safest means of transportation. Catenary poles are used worldwide to support overhead power lines for electric trains. The performance of the catenary poles has an extensive influence on the integrity of the train systems and, consequently, the connected human services. It became a must nowadays to develop SHM systems that provide the instantaneous status of catenary poles in- service, making the decision-making processes to keep or repair the damaged poles more feasible. This study develops a data-driven, model-free approach for status monitoring of cantilever structures, focusing on pre-stressed, spun-cast ultrahigh-strength concrete catenary poles installed along high-speed train tracks. The pro-posed approach evaluates multiple damage features in an unfied damage index, which leads to straightforward interpretation and comparison of the output. Besides, it distinguishes between multiple damage scenarios of the poles, either the ones caused by material degradation of the concrete or by the cracks that can be propagated during the life span of the given structure. Moreover, using a logistic function to classify the integrity of structure avoids the expensive learning step in the existing damage detection approaches, namely, using the modern machine and deep learning methods. The findings of this study look very promising when applied to other types of cantilever structures, such as the poles that support the power transmission lines, antenna masts, chimneys, and wind turbines.}, subject = {Fahrleitung}, language = {en} } @article{AlkamLahmer, author = {Alkam, Feras and Lahmer, Tom}, title = {Eigenfrequency-Based Bayesian Approach for Damage Identification in Catenary Poles}, series = {Infrastructures}, volume = {2021}, journal = {Infrastructures}, number = {Volume 6, issue 4, article 57}, publisher = {MDPI}, address = {Basel}, doi = {10.3390/infrastructures6040057}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20210510-44256}, pages = {1 -- 19}, abstract = {This study proposes an efficient Bayesian, frequency-based damage identification approach to identify damages in cantilever structures with an acceptable error rate, even at high noise levels. The catenary poles of electric high-speed train systems were selected as a realistic case study to cover the objectives of this study. Compared to other frequency-based damage detection approaches described in the literature, the proposed approach is efficiently able to detect damages in cantilever structures to higher levels of damage detection, namely identifying both the damage location and severity using a low-cost structural health monitoring (SHM) system with a limited number of sensors; for example, accelerometers. The integration of Bayesian inference, as a stochastic framework, in the proposed approach, makes it possible to utilize the benefit of data fusion in merging the informative data from multiple damage features, which increases the quality and accuracy of the results. The findings provide the decision-maker with the information required to manage the maintenance, repair, or replacement procedures.}, subject = {Fahrleitung}, language = {en} } @phdthesis{Oucif, author = {Oucif, Chahmi}, title = {Analytical Modeling of Self-Healing and Super Healing in Cementitious Materials}, doi = {10.25643/bauhaus-universitaet.4229}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20200831-42296}, school = {Bauhaus-Universit{\"a}t Weimar}, pages = {208}, abstract = {Self-healing materials have recently become more popular due to their capability to autonomously and autogenously repair the damage in cementitious materials. The concept of self-healing gives the damaged material the ability to recover its stiffness. This gives a difference in comparing with a material that is not subjected to healing. Once this material is damaged, it cannot sustain loading due to the stiffness degradation. Numerical modeling of self-healing materials is still in its infancy. Multiple experimental researches were conducted in literature to describe the behavior of self-healing of cementitious materials. However, few numerical investigations were undertaken. The thesis presents an analytical framework of self-healing and super healing materials based on continuum damage-healing mechanics. Through this framework, we aim to describe the recovery and strengthening of material stiffness and strength. A simple damage healing law is proposed and applied on concrete material. The proposed damage-healing law is based on a new time-dependent healing variable. The damage-healing model is applied on isotropic concrete material at the macroscale under tensile load. Both autonomous and autogenous self-healing mechanisms are simulated under different loading conditions. These two mechanisms are denoted in the present work by coupled and uncoupled self-healing mechanisms, respectively. We assume in the coupled self-healing that the healing occurs at the same time with damage evolution, while we assume in the uncoupled self-healing that the healing occurs when the material is deformed and subjected to a rest period (damage is constant). In order to describe both coupled and uncoupled healing mechanisms, a one-dimensional element is subjected to different types of loading history. In the same context, derivation of nonlinear self-healing theory is given, and comparison of linear and nonlinear damage-healing models is carried out using both coupled and uncoupled self-healing mechanisms. The nonlinear healing theory includes generalized nonlinear and quadratic healing models. The healing efficiency is studied by varying the values of the healing rest period and the parameter describing the material characteristics. In addition, theoretical formulation of different self-healing variables is presented for both isotropic and anisotropic maerials. The healing variables are defined based on the recovery in elastic modulus, shear modulus, Poisson's ratio, and bulk modulus. The evolution of the healing variable calculated based on cross-section as function of the healing variable calculated based on elastic stiffness is presented in both hypotheses of elastic strain equivalence and elastic energy equivalence. The components of the fourth-rank healing tensor are also obtained in the case of isotropic elasticity, plane stress and plane strain. Recent research revealed that self-healing presents a crucial solution also for the strengthening of the materials. This new concept has been termed ``Super Healing``. Once the stiffness of the material is recovered, further healing can result as a strengthening material. In the present thesis, new theory of super healing materials is defined in isotropic and anisotropic cases using sound mathematical and mechanical principles which are applied in linear and nonlinear super healing theories. Additionally, the link of the proposed theory with the theory of undamageable materials is outlined. In order to describe the super healing efficiency in linear and nonlinear theories, the ratio of effective stress to nominal stress is calculated as function of the super healing variable. In addition, the hypotheses of elastic strain and elastic energy equivalence are applied. In the same context, new super healing matrix in plane strain is proposed based on continuum damage-healing mechanics. In the present work, we also focus on numerical modeling of impact behavior of reinforced concrete slabs using the commercial finite element package Abaqus/Explicit. Plain and reinforced concrete slabs of unconfined compressive strength 41 MPa are simulated under impact of ogive-nosed hard projectile. The constitutive material modeling of the concrete and steel reinforcement bars is performed using the Johnson-Holmquist-2 damage and the Johnson-Cook plasticity material models, respectively. Damage diameters and residual velocities obtained by the numerical model are compared with the experimental results and effect of steel reinforcement and projectile diameter is studied.}, subject = {Schaden}, language = {en} } @article{KreibichPirothSeifertetal., author = {Kreibich, H. and Piroth, K. and Seifert, I. and Maiwald, Holger and Kunert, U. and Schwarz, Jochen and Merz, B. and Thieken, A. H.}, title = {Is flow velocity a significant parameter in flood damage modelling?}, series = {Natural Hazards and Earth System Science}, journal = {Natural Hazards and Earth System Science}, doi = {10.25643/bauhaus-universitaet.3145}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20170425-31455}, pages = {1679 -- 1692}, abstract = {Flow velocity is generally presumed to influence flood damage. However, this influence is hardly quantified and virtually no damage models take it into account. Therefore, the influences of flow velocity, water depth and combinations of these two impact parameters on various types of flood damage were investigated in five communities affected by the Elbe catchment flood in Germany in 2002. 2-D hydraulic models with high to medium spatial resolutions were used to calculate the impact parameters at the sites in which damage occurred. A significant influence of flow velocity on structural damage, particularly on roads, could be shown in contrast to a minor influence on monetary losses and business interruption. Forecasts of structural damage to road infrastructure should be based on flow velocity alone. The energy head is suggested as a suitable flood impact parameter for reliable forecasting of structural damage to residential buildings above a critical impact level of 2m of energy head or water depth. However, general consideration of flow velocity in flood damage modelling, particularly for estimating monetary loss, cannot be recommended.}, subject = {Str{\"o}mungsgeschwindigkeit}, language = {en} } @phdthesis{Tietz, author = {Tietz, Robert}, title = {Adaptierte und objektivierte Minderkostenberechnung bei unwesentlichen M{\"a}ngeln in Shoppingcentern}, doi = {10.25643/bauhaus-universitaet.2567}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20160425-25674}, school = {Bauhaus-Universit{\"a}t Weimar}, pages = {162}, abstract = {Minderkostenberechnung bei unwesentlichen M{\"a}ngeln}, subject = {Vergabe- und Vertragsordnung f{\"u}r Bauleistungen}, language = {de} }