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Investigation of temperature effects on ultrasonic velocity in a prestressed concrete bridge model
(2022)
Ultrasonic measurements have recently been applied in the context of structural health monitoring in civil engineering. The ultrasonic method is very sensitive to environmental conditions and material property changes, which might be caused by prestress losses and loading effects on the bridge. However, it remains a challenge to identify the damage mechanisms causing structural property changes from the above mentioned factors influencing ultrasonics. The focus of this contribution is to investigate the correlation between ultrasonic velocities and temperature by the coda wave interferometry (CWI) analysis. Long-term monitoring of a prestressed concrete bridge model under field conditions was carried out to observe the effect of temperature. The homogeneous change in concrete caused by temperature was revealed by applying the CWI method. The threshold value of the best correlation coefficients for the linear regression of temperature and ultrasonic velocity changes was also studied. Experimental assessment will provide a ratio for temperature correction to evaluate the pre-stressing force decrease and its consequences on crack opening or extension.
Investigation of temperature effects on ultrasonic velocity in a prestressed concrete bridge model
(2022)
Ultrasonic measurements have recently been applied in the context
of structural health monitoring in civil engineering. The ultrasonic method is very sensitive to environmental conditions and material property changes, which might be caused by prestress losses and loading effects on the bridge. However, it remains a challenge to identify the damage mechanisms causing structural property changes from the above-mentioned factors influencing ultrasonics. The focus of this contribution is to investigate the correlation between ultrasonic velocities and temperature by the coda wave interferometry (CWI) analysis. Long-term monitoring of a prestressed concrete bridge model under field conditions was carried out to observe the effect of temperature. The homogeneous change in concrete caused
by temperature was revealed by applying the CWI method. The threshold value of the best correlation coefficients for the linear regression of temperature and ultrasonic velocity changes was also studied. Experimental assessment will provide a ratio for temperature correction to evaluate the prestressing force decrease and its consequences on crack opening or extension.
This research is to perform passive and active measurements on a
large-scale prestressed concrete bridge model under the outdoor
condition. Multi sensors were applied to this test structure –
BLEIB, which is located at the BAM test site. The experimental
evaluation of ultrasonic wave propagation and seismic noise
recordings were considered for revealing the bridge damage
condition, as a basic for developing a reliable bridge monitoring
system.
Damage assessment of civil structures using wave propagation analysis and transmissibility functions
(2021)
This presentation shows the applicaiton of seismic interferometry to vibration recordings. The Normalized-Input-Output-Minimization (NIOM) method to reconstruct the virtual impulse wave propagation is introduced. We obtain wave velocities and transmissibility functions and consider them as reference values for the damage detection method. At the end, the evaluation results are presented by two examples: a 14-story RC building and a 64 m long pedestrian bridge.
Nowadays, civil engineers have applied prestressing technique to long span bridges to enhance the structural strength and to improve the structural performance in their life time.
However, it‘s not easy to avoid prestress loss during the construction or in service time. This problem will influence the function of the structures and worse make our life in danger.
Therefore, it‘s important to focus on the topic „bridge monitoring“ to make sure the structural property is "health". This presentation introduces the work which fulfills the research goal - birdge monitoring. A large-scale prestressed concrete bridge model was considered in this work. We obteined various damaged condition due to the different prestressed levels which we can change every time in the experiment.
The experimental measurement in two scales were demonstrated by ultrasonics and natural vibration of the bridge.
Structural health monitoring is a big issue of the prevention measure for civil structures in the seismic hazard region. The GIOTTO project aims to develop of the real time monitoring in civil engineering by use of the 6 DOFs sensors. This presented work is part of the GIOTTO Project. BAM offered the idea test structure BLEIB bridge for experiment. This prestressed concrete bridge model benefits us to have the various structural condition with different pre-stress. The passive and active monitoring were carried out. The seismic interferometry technique was considered to extract the virtual wave propagation in the structure comparable to the real impulse response excited by the hammer impact. Meanwhile the ultrasonic measurement was performed during the monitoring. The coda wave interferometry (CWI) was applied to investigate the wave velocity variation in two kinds of scale recordings at different prestressed states. The experimental result approves that the seismological noise- based methods are the appropriate evaluation tool for the measurement data.
Damage Assessment of Civil Structures Using Wave Propagation Analysis and Transmissibility Functions
(2022)
A common damage detection method in civil engineering is to monitor dynamic characteristics such as natural frequencies and modal shapes, which are directly related to the structural stiffness. However, the discrepancy in measured natural frequencies may result from environmental changes, the soil-structure interaction or effects caused by earthquakes. This makes it difficult to decide whether the local change in structural properties is caused by damage or other factors. To address this challenge and thus improve the current damage detection method, the wave propagation analysis method and the transmissibility relationship were considered. In our study, the wave propagation field in structures was reconstructed by applying the Normalized-Input-Output-Minimization (NIOM) method to vibration recordings. Wave velocities and transmissibility functions were considered as reference values for the damage indicators. This paper demonstrates the evaluation of local property changes in two examples of large-scale structures: a 14-story RC building and a 64 m long pedestrian bridge. The proposed damage indicators show a clear correspondence to structural changes.
This contribution introduces an investigation of a large-scale prestressed concrete bridge model (“BLEIB” structure at the BAM-TTS open air test site) by means of on-site cooperative measurements. This bridge has an external post-tensioning system and has been instrumented with the ultrasonic transducers, temperature sensors and optical fibers for Distributed Acoustic Sensing (DAS). Our experiment was designed to test the suitability of the novel 6C sensors developed within the framework of the GIOTTO project – the IMU50. The IMU50 sensor enables vibration measurements in translation along three axes and rotation around three axes. The geophone sensors were considered for complementary measurements of vertical velocity response. In the experiment, several perturbations were achieved by controlling the external influence factors such as loading and prestressing changes. The aim of the integrated measurement strategy was to fully observe the results of the condition change and to verify the effectiveness of multiple sensors for bridge monitoring.
This contribution introduces an investigation of a large-scale prestressed concrete bridge model (“BLEIB” structure at the BAM-TTS open air test site) by means of on-site cooperative measurements. This bridge has an external post-tensioning system and has been instrumented with the ultrasonic transducers, temperature sensors and optical fibers for Distributed Acoustic Sensing (DAS). Our experiment was designed to test the suitability of the novel 6C sensors developed within the framework of the GIOTTO project – the IMU50. The IMU50 sensor enables vibration measurements in translation along three axes and rotation around three axes. The geophone sensors were considered for complementary measurements of vertical velocity response. In the experiment, several perturbations were achieved by controlling the external influence factors such as loading and prestressing changes. The aim of the integrated measurement strategy was to fully observe the results of the condition change and to verify the effectiveness of multiple sensors for bridge monitoring.