7.2 Ingenieurbau
Filtern
Dokumenttyp
- Zeitschriftenartikel (44) (entfernen)
Referierte Publikation
- ja (44) (entfernen)
Schlagworte
- Compressive strength (4)
- Train passage (4)
- Hammer impact (3)
- Slab track (3)
- Axle sequence (2)
- Bauwerksüberwachung (2)
- Bridge (2)
- Damage detection (2)
- Earth block masonry (2)
- Fatigue (2)
- Moisture content (2)
- Offshore (2)
- Relative humidity (2)
- Resonance (2)
- Soil erosion (2)
- Static axle loads (2)
- Structural Health Monitoring (2)
- Structural health monitoring (2)
- Train-induced ground vibration (2)
- Vehicle–track interaction (2)
- Acoustic emission (1)
- Acoustic emission analysis (1)
- Ambient excitation (1)
- Ansys Autodyn (1)
- Attenuation (1)
- Automated Modal Analysis for Tracking Structural Change during Construction and Operation Phases (1)
- Automated operational modal analysis (1)
- Axle impulses (1)
- Ballast track (1)
- Bauwerksdiagnostik (1)
- Bauwerksmonitoring (1)
- Bayesian analysis (1)
- Belastungstest (1)
- Benchmark (1)
- Boundary element (1)
- Box-Behnken (1)
- Bridge resonance (1)
- Bridge vibration (1)
- Brücken (1)
- Building and Construction (1)
- Cancellation (1)
- Cement-based composites (1)
- Civil and Structural Engineering (1)
- Coating (1)
- Cohesive granular materials (1)
- Compliance function (1)
- Compression tests (1)
- Computational (1)
- Concrete (1)
- Condensed Matter Physics (1)
- Continuous soil (1)
- Continuously inhomogeneous geological media (1)
- Continuously inhomogeneous soils (1)
- Crack damage detection (1)
- Cracks (1)
- DUCON® (1)
- Damage characterization (1)
- Damage evolution (1)
- Damage localization (1)
- Decision matrix analysis (1)
- Deterioration (1)
- Digitalisierung (1)
- Discrete Element Method (1)
- Discrete element method (1)
- Drucker-Prager (1)
- Ductility (1)
- Dynamic axle loads (1)
- E-modulus (1)
- Earth blocks (1)
- Earth masonry (1)
- Ermüdung (1)
- Erosion (1)
- Estimation (1)
- Features (1)
- Fequency domain (1)
- Fibre optic sensors (1)
- Filter effects (1)
- Finite element (1)
- Finite element analysis (1)
- Finite elements (1)
- Finite-element boundary-element method (1)
- Fly ash (1)
- GPA (1)
- GPU Parallel computing (1)
- General Materials Science (1)
- Geology (1)
- Geometric vehicle and track irregularities (1)
- Granular cohesion (1)
- Ground vibration (1)
- Grouted connection (1)
- Grouting (1)
- High-rise building (1)
- Horizontal wind turbine (1)
- Hydraulic jet erosion (1)
- Impact (1)
- Impact loading (1)
- Imperfektion (1)
- Impinging jet (1)
- Inclination angle (1)
- Inspection (1)
- Irregular soil (1)
- Jacket support structure (1)
- Jet erosion test (1)
- Jet impingement (1)
- LBM-DEM (1)
- Laminar flow (1)
- Lateral dynamic displacement (1)
- Lattice Boltzmann Method (1)
- Lattice Boltzmann method (1)
- Layered soil (1)
- Layered soils (1)
- Load identification (1)
- Load tests (1)
- Load vector (1)
- Load-bearing behaviour (1)
- Luminescence (1)
- Merkblatt (1)
- Metakaolin (1)
- Micro-reinforcement (1)
- Micromechanical modelling (1)
- Microsilica (1)
- Mitigation (1)
- Mix design (1)
- Mobile elements (1)
- Modal analysis (1)
- Model update (1)
- Model updating (1)
- Modell-Update (1)
- Modulus of elasticity (1)
- Moisture (1)
- Monitoring (1)
- Monitoring-informed inspection and maintenance planning (1)
- Multi-beam track model (1)
- Numerical modeling (1)
- Obstacles (1)
- Offshore geomechanics (1)
- Offshore wind turbine (1)
- Optimal sensor placement (1)
- Perfectly Matched Layer (PML) (1)
- Piaui state (1)
- Pile bending stiffness (1)
- Pile foundation (1)
- Planar tomography (1)
- Post-impact evaluation (1)
- Pressure (1)
- Quasi-static and dynamic tests (1)
- Quasi-static response; (1)
- Rail roughness (1)
- Railway bridge (1)
- Random dynamics and vibrations (1)
- Random stiffness variation (1)
- Randomly heterogeneous soil (1)
- Recovery experiments (1)
- Rehabilitation (1)
- Reinforced concrete structure (1)
- Reliability (1)
- Remote sensing vibrometer (1)
- Repair (1)
- Richtlinie (1)
- SHCC (1)
- Sandstone (1)
- Santa-marta (1)
- Scattered axle impulses (1)
- Scattering (1)
- Schrauben (1)
- Serra da cangalha (1)
- Shell buckling (1)
- Soil forces (1)
- Soil stiffness (1)
- Sorption isotherm (1)
- Static loading (1)
- Statistical evaluation (1)
- Statistical pattern recognition (1)
- Statistical tests (1)
- Stereo photogrammetry (1)
- Stiffness variation (1)
- Strain (1)
- Strength (1)
- Stress-strain relation (1)
- Stress–strain-relation (1)
- Structural system identification (1)
- Structural systems (1)
- Strukturmonitoring (1)
- Sustainable binders (1)
- System identification (1)
- TRC (1)
- Temperature effect (1)
- Temperature effect rejection (1)
- Temperature modeling (1)
- Track deflection (1)
- Track displacements (1)
- Track filter (1)
- Track filtering (1)
- Track-soil interaction (1)
- Train-induced vibration (1)
- Trench (1)
- Tunnel (1)
- Tunnel-to-surface reduction (1)
- UAS (1)
- UHPC (1)
- Ultrasonic testing (1)
- Unbounded domain (1)
- Uncertainty quantification (1)
- Value of information (1)
- Variational Bayesian statistics (1)
- Vehicle-track interaction (1)
- Vibration measurement (1)
- Viscosity (1)
- Vorspannung (1)
- Water Science and Technology (1)
- Wavenumber domain (1)
- Wheelset (1)
- Wind energy tower (1)
- Wind turbine tower (1)
- Windenergieanlage (1)
- Windenergieanlagen (1)
- Workability (1)
- layered soil (1)
Organisationseinheit der BAM
- 7.2 Ingenieurbau (44) (entfernen)
Paper des Monats
- ja (4)
Aim of this study is to provide information about moisture dependent material behaviour of unstabilised loadbearing earth blocks and mortars. Compressive strength and Young’s modulus were investigated after conditioning in varying relative humidity reaching from 40 % up to 95 %. The material composition and physical properties were investigated to understand the influence of relative humidity onto the mechanical properties. A normalisation of strength and stiffness by the values obtained at 23 ◦C and 50 % relative humidity reveals a linear dependence of compressive strength and Young’s modulus that is regardless of the material composition.
Thus, it is possible to describe the influence of relative humidity onto the load-bearing behaviour of unstabilised earth masonry materials in a generally valid formulation.
block and mortar types is analysed with particular regard to the influence of varying relative humidity. The uniaxial compressive strength and deformation characteristics of unstabilised earth blocks and mortars as well as of unstabilised earth block masonry are studied in detail and compared to conventional masonry to evaluate whether the structural design can be made accordingly. An increase of 30 % points in relative humidity leads to a reduction of the masonry´s compressive strength between 33 % and 35 % whereas the Young´s modulus is reduced by 24–29 %. However, the ratio between the Young´s modulus and the characteristic compressive strength of earth block masonry ranges between E33/fk = 283–583 but is largely independent of the relative humidity. The results show that the mechanical properties of the investigated unstabilised earth block masonry are sufficient for load-bearing structures, yielding a masonry compressive strength between 2.3 MPa and 3.7 MPa throughout the range of moisture contents
investigated. In general, the design concept of conventional masonry can be adapted for unstabilised earth masonry provided that the rather low Young´s modulus as well as the moisture dependence of both, compressive strength and Young´s modulus, are sufficiently taken into
account.
The statistical subspace-based damage detection technique has shown promising theoretical and practical results for vibration-based structural health monitoring. It evaluates a subspacebased residual function with efficient hypothesis testing tools, and has the ability of detecting small changes in chosen system parameters. In the residual function, a Hankel matrix of Output covariances estimated from test data is confronted to its left null space associated to a reference model. The hypothesis test takes into account the covariance of the residual for decision making. Ideally, the reference model is assumed to be perfectly known without any uncertainty, which is not a realistic assumption. In practice, the left null space is usually estimated from a reference data set to avoid model errors in the residual computation. Then, the associated uncertainties may be non-negligible, in particular when the available reference data is of limited length. In this paper, it is investigated how the statistical distribution of the residual is affected when the reference null space is estimated. The asymptotic residual distribution is derived, where its refined covariance term considers also the uncertainty related to the reference null space estimate. The associated damage detection test closes a theoretical gap for real-world applications and leads to increased robustness of the method in practice. The importance of including the estimation uncertainty of the reference null space is shown in a numerical study
and on experimental data of a progressively damaged steel frame.
Using digital twins for decision making is a very promising concept which combines simulation models with corresponding experimental sensor data in order to support maintenance decisions or to investigate the reliability. The quality of the prognosis strongly depends on both the data quality and the quality of the digital twin. The latter comprises both the modeling assumptions as well as the correct parameters of these models. This article discusses the challenges when applying this concept to realmeasurement data for a demonstrator bridge in the lab, including the data management, the iterative development of the simulation model as well as the identification/updating procedure using Bayesian inference with a potentially large number of parameters. The investigated scenarios include both the iterative identification of the structural model parameters as well as scenarios related to a damage identification. In addition, the article aims at providing all models and data in a reproducibleway such that other researcher can use this setup to validate their methodologies.
The fatigue process of concrete under compressive cyclic loading is still not completely explored. The corresponding damage processes within the material structure are especially not entirely investigated. The application of acoustic measurement methods enables a better insight into the processes of the fatigue in concrete. Normal strength concrete was investigated under compressive cyclic loading with regard to the fatigue process by using acoustic methods in combination with other nondestructive measurement methods. Acoustic emission and ultrasonic signal measurements were applied together with measurements of strains, elastic modulus, and static strength. It was possible to determine the anisotropic character of the fatigue damage caused by uniaxial loading based on the ultrasonic measurements. Furthermore, it was observed that the fatigue damage seems to consist not exclusively of load parallel oriented crack structures. Rather, crack structures perpendicular to the load as well as local compacting are likely components of the fatigue damage. Additionally, the ultrasonic velocity appears to be a good indicator for fatigue damage beside the elastic modulus. It can be concluded that acoustic methods allow an observation of the fatigue process in concrete and a better understanding, especially in combination with further measurement methods.
Automated modal analysis for tracking structural change during construction and operation phases
(2019)
The automated modal analysis (AMA) technique has attracted significant interest over the last few years, because it can track variations in modal parameters and has the potential to detect structural changes. In this paper, an improved density-based spatial clustering of applications with noise (DBSCAN) is introduced to clean the abnormal poles in a stabilization diagram. Moreover, the optimal system model order is also discussed to obtain more stable poles. A numerical Simulation and a full-scale experiment of an arch bridge are carried out to validate the effectiveness of the proposed algorithm. Subsequently, the continuous dynamic monitoring system of the bridge and the proposed algorithm are implemented to track the structural changes during the construction phase. Finally, the artificial neural network (ANN) is used to remove the temperature effect on modal frequencies so that a health index can be constructed under operational conditions.
Reliability analysis of deteriorating structural systems requires the solution of time-variant reliability problems.
In the general case, both the capacity of and the loads on the structure vary with time. This analysis can be approached by approximation through a series of time-invariant reliability problems, which is a potentially effective strategy for cases where direct solutions of the time-variant reliability problem are challenging, e.g. for structural systems with many elements or arbitrary load processes. In this contribution, we thoroughly Review the formulation of the equivalent time-invariant reliability problems and extend this approximation to structures for which inspection and monitoring data is available. Thereafter, we present methods for efficiently evaluating the reliability over time. In particular, we propose the combination of sampling-based methods with a FORM (first-order reliability method) approximation of the series system reliability problem that arises in the computation of the lifetime reliability. The framework and algorithms are demonstrated on a set of numerical examples, which include the computation of the reliability conditional on inspection data.
Die Infrastruktursysteme der Industriestaaten erfordern heute und in Zukunft ein effizientes Management bei alternder Bausubstanz, steigenden Lasten und gleichbleibend hohem Sicherheitsniveau. Digitale Technologien bieten ein großes Potenzial zur Bewältigung der aktuellen und künftigen Herausforderungen im Infrastrukturmanagement. Im BMBF-geförderten Projekt Bewertung alternder Infrastrukturbauwerke mit digitalen Technologien (AISTEC) wird untersucht, wie unterschiedliche Technologien und deren Verknüpfung gewinnbringend eingesetzt werden können. Am Beispiel der Maintalbrücke Gemünden werden ein sensorbasiertes Bauwerksmonitoring, bildbasierte Inspektion mit durch Kameras ausgestatteten Drohnen (UAS) und die Verknüpfung digitaler Bauwerksmodelle umgesetzt. Die aufgenommenen Bilder dienen u. a. als Grundlage für spätere visuelle Anomaliedetektionen und eine 3D-Rekonstruktion, welche wiederum für die Kalibrierung und Aktualisierung digitaler Tragwerksmodelle genutzt werden. Kontinuierlich erfasste Sensordaten werden ebenfalls zur Kalibrierung und Aktualisierung der Tragwerksmodelle herangezogen. Diese Modelle werden als Grundlage für Anomaliedetektionen und perspektivisch zur Umsetzung von Konzepten der prädiktiven Instandhaltung verwendet. Belastungsfahrten und historische Daten dienen in diesem Beitrag der Validierung von kalibrierten Tragwerksmodellen.
Impact resistance of reinforced concrete (RC) structures can be significantly improved by strengthening RC members with thin composite layers featuring high damage tolerance. Indeed, to limit the well-known vulnerability of cement-based materials against impact loading, the synergistic effects of short fibres and continuous textile meshes as hybrid reinforcement has been proved to be highly beneficial. This paper addresses the characterisation of novel cement-based hybrid composites through accelerated drop-weight impact tests conducted on rectangular plates at different impact energies. Two distinct matrices are assessed, with particular interest in a newly developed limestone calcined clay cement (LC3)-based formulation. Important parameters quantifying energy dissipation capability, load bearing capacity and damage are cross-checked to compute the ballistic limit and estimate the safety-relevant characteristics of the different composites at hand. Although textiles alone can improve the damage tolerance of fine concrete to some extent, the crack-bridging attitude of short, well-dispersed fibres in hybrid composites imparts a certain ductility to the cement-based matrices, allowing a greater portion of the textile to be activated and significantly reducing the amount of matrix spalling under impact.
Repair is an indispensable part of the maintenance of structures over their lifetimes. Structural grouting is a widely used remediation technique for concrete components, trenches, mine subsidence, dam joints, restoration of masonry structures, and geological stabilizations. A structural grout system should be injectable in narrow spaces and hence include ingredients with finer particles. Ultrafine cements are ideal for these type of demanding grouts due to their superior properties compared to that of the less expensive, but coarser ordinary Portland cement (OPC). Supplementary cementitious materials (SCMs) are often used to replace OPC clinker based binder in order to modify certain properties and to reduce costs. The most commonly used SCMs are fly ash (FA), and ground granulated blast furnace slag (GGBS). For various special applications microsilica (MS), and metakaolin (MK) are also used. Identifying the optimum replacement contents of OPC by SCMs are a challenge during the design of such grouts. The aim of this experimental study is to investigate the effect of the selected SCMs (FA, MS and MK) on the slump flow, time of efflux, viscosity, shrinkage, and compressive and flexural strength of ultrafine cement based grouts with constant water-binder ratio and superplasticizer content. The test program was formulated using Box-Behnken design principles. Maximum percentages of replacement with ultrafine cement was 6% by volume of cement for MS and 16% for FA, and MK. The results suggest that most investigated grouts have the potential to be used for structural applications. The appropriate quadratic models are then formulated through statistical tools and presented as response surfaces. The trends indicate that fly ash improves the rheological properties, whereas microsilica and metakaolin positively affect shrinkage and mechanical properties to some extent. Based on the influence of SCMs and priorities among the properties, Decision Matrix Analysis (DMA) is carried out to select the most suitable ones among the SCMs. The analysis suggests that microsilica and fly ash are more suitable as SCMs than metakaolin without affecting the properties.