Die Bewertung des Bauwerkszustands von Brückenbauwerken erfolgt in Deutschland anhand der auf Grundlage regelmäßiger Bauwerksprüfungen ermittelten Bauwerksnote. Eine Methodik zur Einbindung von ...Monitoringdaten in die Bauwerksbewertung existiert dagegen derzeit noch nicht. Dabei kann ein Bauwerksmonitoring zur Unterstützung der klassischen Bauwerksprüfung genutzt werden, um das Auftreten oder die Entwicklung von Bauwerksschäden vorübergehend oder dauerhaft zu überwachen und so die von den Schäden ausgehenden Risiken zu mindern. Des Weiteren können in vielen Fällen rechnerische Standsicherheitsdefizite mittels gezielt eingesetzter Messmaßnahmen kompensiert werden. Herausforderungen hinsichtlich der integralen Zustandsbewertung ergeben sich aus der unterschiedlichen Bewertung von Bauwerksschäden (Benotung) und Standsicherheitsnachweisen (Ausnutzungsgrad). Dieser Beitrag stellt eine Methodik vor, die Monitoringdaten und Bauwerksschäden in einer Echtzeitbewertungskennzahl aggregiert, die auch für Nichtfachleute verständlich ist. Neben dem allgemeinen Bewertungsverfahren, das bekannte Elemente aus dem Bewertungsschema nach SIB‐Bauwerke einschließt, werden zwei konkrete Anwendungsfälle anhand des smartBRIDGE‐Konzepts an der Köhlbrandbrücke in Hamburg gezeigt. Dabei handelt es sich um zwei aktuelle rechnerische Standsicherheitsdefizite, die durch eine messtechnische Überwachung kompensiert werden.
Aggregation of condition indicators for bridge structures based on inspection and monitoring data
In Germany, the assessment of existing structures is based on a uniform structural rating obtained from regular in situ inspections. However, a method to include monitoring data into the structural rating does not yet exist. Though, a structural monitoring can be used to monitor the occurrence or the growth of damages, thereby reducing the risks emanating from theses damages. Furthermore, calculative safety deficits can, in many cases, be compensated by specific monitoring measures. Challenges concerning the integral assessment result from the differences in the assessment of structural damages (rating) and limit state checks (utilization). This paper presents a method which aggregates monitoring data and structural damages into a real time condition indicator that is also comprehensible for non‐experts. Apart from the general rating procedure that includes well‐known elements of the rating system of the German structural information database “SIB‐Bauwerke”, two use cases of the smartBRIDGE concept for the Köhlbrandbrücke in Hamburg will be shown. The use cases consist of two current calculative safety deficits which are compensated by monitoring measures.
Abstract
Die Bewertung des Bauwerkszustands von Brückenbauwerken erfolgt in Deutschland anhand der auf Grundlage regelmäßiger Bauwerksprüfungen ermittelten Bauwerksnote. Eine Methodik zur Einbindung ...von Monitoringdaten in die Bauwerksbewertung existiert dagegen derzeit noch nicht. Dabei kann ein Bauwerksmonitoring zur Unterstützung der klassischen Bauwerksprüfung genutzt werden, um das Auftreten oder die Entwicklung von Bauwerksschäden vorübergehend oder dauerhaft zu überwachen und so die von den Schäden ausgehenden Risiken zu mindern. Des Weiteren können in vielen Fällen rechnerische Standsicherheitsdefizite mittels gezielt eingesetzter Messmaßnahmen kompensiert werden. Herausforderungen hinsichtlich der integralen Zustandsbewertung ergeben sich aus der unterschiedlichen Bewertung von Bauwerksschäden (Benotung) und Standsicherheitsnachweisen (Ausnutzungsgrad). Dieser Beitrag stellt eine Methodik vor, die Monitoringdaten und Bauwerksschäden in einer Echtzeitbewertungskennzahl aggregiert, die auch für Nichtfachleute verständlich ist. Neben dem allgemeinen Bewertungsverfahren, das bekannte Elemente aus dem Bewertungsschema nach SIB‐Bauwerke einschließt, werden zwei konkrete Anwendungsfälle anhand des smartBRIDGE‐Konzepts an der Köhlbrandbrücke in Hamburg gezeigt. Dabei handelt es sich um zwei aktuelle rechnerische Standsicherheitsdefizite, die durch eine messtechnische Überwachung kompensiert werden.
Abstract
Aggregation of condition indicators for bridge structures based on inspection and monitoring data
In Germany, the assessment of existing structures is based on a uniform structural rating obtained from regular in situ inspections. However, a method to include monitoring data into the structural rating does not yet exist. Though, a structural monitoring can be used to monitor the occurrence or the growth of damages, thereby reducing the risks emanating from theses damages. Furthermore, calculative safety deficits can, in many cases, be compensated by specific monitoring measures. Challenges concerning the integral assessment result from the differences in the assessment of structural damages (rating) and limit state checks (utilization). This paper presents a method which aggregates monitoring data and structural damages into a real time condition indicator that is also comprehensible for non‐experts. Apart from the general rating procedure that includes well‐known elements of the rating system of the German structural information database “SIB‐Bauwerke”, two use cases of the smartBRIDGE concept for the Köhlbrandbrücke in Hamburg will be shown. The use cases consist of two current calculative safety deficits which are compensated by monitoring measures.
•Employed ITSS method is initially validated for analyzing OBD under combined loading.•A good correlation was obtained from predicted and experimental results.•The effects of shear stress and the ...ratio of specimen width to length are obtained.
This paper investigates the fatigue property of U rib-crossbeam-deck connections in orthotropic steel bridge decks (OBD) under combined loading of bending and torsion by using the improved traction structural stress method. Applicability of the method for analyzing OBD under combined loads is validated by comparing the simulation results with the experimental results from the literature. The fatigue property of OBD in multiaxial stress states is studied by investigating the effects of the ratio of specimen width to length and combined loading amplitude. The trend and amplitude of the improved traction structural stress distribution change with an increase in the ratio of width to length.
•We tested four dapped beam ends under service and ultimate design loads.•Three beam specimens included modifications for reducing diagonal cracking at the reentrant corner.•In none the specimens the ...crack at the reentrant corner exceeded maximum allowed width under service load.•Longitudinal post-tensioning of the dapped end significantly improved the performance in terms of diagonal cracking.•The PCI Design Handbook conservatively predicted the load capacity of the specimens.
A common structural system in precast pre-stressed concrete girders with dapped ends has been intensively used in elevated viaducts recently built in Mexico City. A critical aspect of this solution resides in the possibility of a premature cracking in the reentrant corner of the dapped-end beam. An experimental research program was carried out to evaluate the performance of the present solution of the dapped end, both under service loading and ultimate design loads, and also to explore other solutions that could improve the performance in terms of the cracking of the reentrant corner.
Four dapped-end beams models at a 1:3.6 scale were built and tested under vertical loads. The first specimen reproduced the solution adopted in the prototype, which was designed and reinforced according to the recommendations of the PCI Design Handbook. To the second one a longitudinal post-tension was applied, in the third specimen diagonal bars replaced part of the hangers, and the fourth was provided with both diagonal bars and post-tensioning.
Experimental results allowed to conclude that, the specimens with longitudinal post-tensioning at the dapped, performed within the code requirements both under the service and ultimate loads, showed the best behavior in terms of cracking control. The strut-and-tie model proposed by Mattock provides a good prediction of the load capacity attained in the experimental specimens.
The emergence of stretchable electronic technology has led to the development of many industries and facilitated many unprecedented applications, owing to its ability to bear various deformations. ...However, conventional solid elastomer substrates and encapsulation can severely restrict the free motion and deformation of patterned interconnects, leading to potential mechanical failures and electrical breakdowns. To address this issue, we propose a design strategy of porous elastomer substrate and encapsulation to improve the stretchability of serpentine interconnects in island-bridge structures. The serpentine interconnects are fully bonded to the elastomer substrate, while segments above circular pores remain suspended, allowing for free deformation and a substantial improvement in elastic stretchability compared to the solid substrates. The pores ensure unimpeded interconnect deformations, and moderate porosity provides support while maintaining the initial planar state. Compared to conventional solid configurations, finite element analysis (FEA) demonstrates a substantial enhancement of elastic stretchability (e.g. ≈9 times without encapsulation and ≈ 7 times with encapsulation). Uniaxial cyclic loading fatigue experiments validate the enhanced elastic stretchability, indicating the mechanical stability of the porous design. With its intrinsic advantages in permeability, the proposed strategy has the potential to offer insightful inspiration and novel concepts for advancing the field of stretchable inorganic electronics.
A new self-centering concrete bridge column has been developed by the authors. The proposed bridge column uses unstressed partially unbonded seven-wire steel strands as elastic elements to reduce the ...residual displacement of the column after a strong earthquake. This research aimed to study the effect of concrete cover thickness ratio on the cyclic behavior of the proposed column. Four large-scale column specimens were tested using lateral cyclic loading. One column was the conventional concrete bridge column. The other three columns were the proposed self-centering bridge columns with varying concrete cover thickness ratios. Test results showed that partial unbonding effectively prevented the strands from yielding. The proposed columns showed post-yield stiffness ratios higher than the conventional column. The concrete cover thickness ratio did not significantly influence the hysteretic energy dissipation and the strain responses of longitudinal reinforcement. However, it had a significant impact on the post-yield stiffness ratio. The post-yield stiffness ratio of the proposed column tended to be inversely proportional to the concrete cover thickness ratio. A relationship was proposed between the concrete cover thickness ratio and the post-yield stiffness ratio for the preliminary design of the proposed column. Based on the relationship, the cover concrete thickness ratio should not exceed 5.1% to achieve a post-yield stiffness ratio of at least 5%, as recommended in the literature to control the residual displacement of a column.
This article proposes a continuous relative wavelet entropy–based reference-free damage detection algorithm for truss bridge structures. Advantages of the proposed method are that (1) there is no ...need to measure dynamic response of pristine structures, in other words, the method is reference-free; (2) it is suitable for highly nonlinear and nonstationary random response data due to the multiresolution signal analysis feature of the continuous wavelet transform; and (3) it is sensitive to slight damage extents (i.e. 5%–10%) for the tested damage type (i.e. loosening of bolts). In order to demonstrate consistency and sensitivity of the proposed method, multiple experimental tests using a laboratory-size truss structure were mainly conducted for various damage scenarios and progressive damage states. The proposed continuous relative wavelet entropy–based reference-free damage detection algorithm showed reliable damage localization capabilities, and it is proven as an effective method compared to other damage detection methods that are dependent on the measurement signals from pristine structures. Due to the generality of the proposed method, applications to identify other types of damage based on different types of signals can be expected.
Non-stationary spatially variable ground motions (SVGMs) are commonly modelled as multivariate oscillatory processes based on evolutionary power spectral density (EPSD) functions. The existing ...conditional simulation algorithms require the known EPSD functions. The EPSD functions are usually assumed to be identical for all locations, which is unreasonable for long-span bridges because variable soil conditions are practically observed at different bridge piers. This paper proposes a conditional simulation algorithm for non-stationary SVGMs in consideration of non-uniform site conditions. The spatial interpolation tool, termed inverse-distance-weighted (IDW) interpolation, is introduced to estimate the EPSD functions at sites without ground motion measurement. Subsequently, the covariance matrix of the random Fourier coefficients of the multivariate oscillatory processes can be calculated. The Kriging estimation is adopted to obtain the unknown random Fourier coefficients, from which the time histories of the non-stationary SVGMs can be conditionally simulated. The proposed conditional simulation algorithm is first validated through a numerical example, in which the EPSD functions of non-uniform sites are represented by a non-stationary Kanai-Tajimi spectrum with different soil parameters. Then, the algorithm is applied to the Jiuzhou Channel Bridge, a navigation channel bridge of the Hong Kong-Zhuhai-Macau Bridge (HZMB), with complex soil and water conditions. Based on the limited in-situ seismic measurement data, the site characteristics in the bridge area are analysed, and the ground motion time histories at all piers can be generated.
Summary
Identifying mode shapes of bridge structures typically require a dense array of stationary sensors to accurately capture mode shapes with appropriate spatial resolution. An alternative ...approach is developed here, which requires only a single pair of actuator and sensor. The mode shape identification involves, first, identifying the natural frequencies and modal damping ratios, followed by an estimation of the mass normalized mode shapes components at the excited and measured degrees of freedom. An input–output balance is employed with a series of inputs and outputs obtained from a sequence of tests. The sequence of tests include exciting and measuring at different locations along the bridge, using either a roving actuator and/or a roving sensor; the requirement for a unique identification is that the roving actuator and sensor must be collocated in at least one of the tests. The performance of the proposed method using different types of responses, namely, displacement, velocity, and acceleration, is assessed using numerical simulations. The effect of different types of errors in the identification process is also studied. The method is finally applied to experimental data obtained from laboratory scale tests.
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