Stefan Hurlebaus | Texas A&M University (original) (raw)

Uploads

Papers by Stefan Hurlebaus

Research paper thumbnail of Localization of notches with Lamb waves

Research paper thumbnail of Modelling and Control Techniques of an Active Vibration Isolation System

In the field of high-resolution measurement and manufacturing, effective anti-vibration measures ... more In the field of high-resolution measurement and manufacturing, effective anti-vibration measures are required to obtain precise and repeatable results. This is particularly true for experiments or processes where the typical amplitudes of the ambient vibration and the dimensions of the investigated or manufactured structures fall in the same range, e.g. submicron semiconductor production, holographic interferometry, confocal optical imaging, and scanning probe microscopy. In the active vibration isolation system examined, signals are acquired by extremely sensitive vibration detectors, and the vibration is reduced using either local analog feedback control or digital model-based control to drive electrodynamic actuators. This papers deals with the modelling and control techniques of such an active vibration isolation system. The modelling, parameter identification, and model updating procedure are described. The experimental setup for testing such an antivibration system is describe...

Research paper thumbnail of Systematic Assessment of Nondestructive Evaluation Techniques for External Post-tensioning and Stay Cable Systems

AbstractNondestructive evaluation (NDE) can provide invaluable information about the condition of... more AbstractNondestructive evaluation (NDE) can provide invaluable information about the condition of tendons in post-tensioned and cable-stayed bridges, which can facilitate preventative actions to mi...

Research paper thumbnail of Post-Tensioned Traffic Signal Structure: Experimental Natural Wind Response and Fatigue Assessment

Cantilevered traffic signal structures undergo wind-induced vibrations causing persistent stress ... more Cantilevered traffic signal structures undergo wind-induced vibrations causing persistent stress cycles that result in welded connection fatigue and fracture. A low-cost damage avoidance concept is proposed to apply post-tensioned prestress to eradicate the detrimental tensile mean stresses found in the tube-to-transverse end plate welded connections. A supplementary load path is introduced to balance the moments arising from the significant dead load associated with the cantilevered arm spanning the roadway, while offering a fail-safe mechanism. Field observations are made on a full-scale prototype structure in a natural wind environment without and with the proposed mitigation system installed; changes in the structure’s stress response are monitored. To quantify the benefit of the proposed system, the fatigue life is estimated using a deterministic framework considering the expected change in fatigue resistance and observed changes in natural wind response for two contrasting win...

Research paper thumbnail of Modelling bridge piers subject to alkali-silica reaction and delayed ettringite formation

Proceedings of the Institution of Civil Engineers - Bridge Engineering

Premature concrete deterioration in certain bridge piers in Texas, USA, has been attributed to th... more Premature concrete deterioration in certain bridge piers in Texas, USA, has been attributed to the deleterious effects of alkali–silica reaction and delayed ettringite formation. A semi-empirical e...

Research paper thumbnail of Nondestructive evaluation of grout defects in internal tendons of post-tensioned girders

NDT & E International

Abstract Post-tensioning systems provide safe and efficient construction solutions for long span ... more Abstract Post-tensioning systems provide safe and efficient construction solutions for long span bridges. Despite the improved grouting practices over the past decade, existing post-tensioning systems may have significant amount of grout defects, which could lead to corrosion of the strands. Condition assessment of post-tensioning systems is necessary to allow bridge owners to take timely, proactive actions to mitigate or prevent further deterioration and unanticipated tendon failures. A detailed experimental study conducted to assess the performance of nondestructive evaluation techniques in detecting grout defects within internal tendons is presented herein. Nondestructive evaluation techniques that include Ground Penetrating Radar, Impact Echo, Ultrasonic Tomography, and Ultrasonic Echo are evaluated in terms of detecting the location and severity of fabricated grout defects in a full-scale post-tensioned U-girder mock-up specimen. While Ground Penetrating Radar can identify the location and profile of the internal tendons, particularly metal ducts due to strong reflections, this method did not provide any information about the defect conditions within the tendon. Both Impact Echo and Ultrasonic Echo techniques are effective in identifying the location of grout defects, but could not differentiate between water, void, or compromised grout conditions. The study clearly demonstrates the need for NDE techniques that are applicable to anchorage regions, and that are capable of estimating the severity and nature of grout defects in internal tendons.

Research paper thumbnail of Concrete Tunnel Lining Evaluation Using Nondestructive Techniques: A Multi-method Case Study at Eisenhower Tunnel

An in-depth investigation of tunnel linings is performed at Eisenhower Tunnel, 60 miles west of D... more An in-depth investigation of tunnel linings is performed at Eisenhower Tunnel, 60 miles west of Denver, Colorado, using a combination of four nondestructive testing methods: air- and ground-coupled ground penetrating radar (GPR), ultrasonic echo (US echo), ultrasonic tomography (UST), and impact echo (IE). A robotic frame with pneumatically operated vacuum plates is used to automate GPR, US echo, and IE. UST was performed manually. These techniques are used to identify and locate the reinforcement mesh and structural steel ribs. Local changes in ultrasonic phase are calculated by phase analysis processing techniques and apparent relationships between positive and negative phase shifts and steel and air interfaces are observed. According to previous laboratory research, these relationships indicate the bonded state between the concrete and the embedded steel, but without ground truth verification this can only be suggested. It is shown that this combination of methods can be used synergistically to provide tunnel owners with the layout and possible condition of tunnel lining reinforcement and structural components.

Research paper thumbnail of Effect of Voids in Grouted, Post-Tensioned Concrete Bridge Construction: Volume 2–Inspection, Repair, Materials, and Risks

Research paper thumbnail of Nondestructive Evaluation Of Concrete Linings At Hanging Lake Tunnel

Research paper thumbnail of Use of Unmanned Marine Vehicles for Hurricane Damage Inspection

This paper describes the deployment of the custom Sea-RAI man-portable un-manned surface vehicle ... more This paper describes the deployment of the custom Sea-RAI man-portable un-manned surface vehicle and two commercially available underwater vehicles (the autonomous YSI EcoMapper and the tethered VideoRay) for inspection of the Rollover Pass bridge in the Bolivar ...

Research paper thumbnail of Experimental and computational investigation of a load-posted steel beam bridge

Research paper thumbnail of MIMO fuzzy identification of building-MR damper systems

Journal of Intelligent & Fuzzy Systems

This paper proposes a multi-input, multi-output (MIMO) nonlinear system identification (SI) of ci... more This paper proposes a multi-input, multi-output (MIMO) nonlinear system identification (SI) of civil structures equipped with magnetorheological (MR) dampers. The nonlinear SI model is developed through the integration of multiple MIMO autoregressive exogenous (ARX) input models, Takagi-Sugeno (TS) fuzzy model, weighted linear least squares, fuzzy C-means and subtractive clustering algorithms. To demonstrate the effectiveness of the MIMO ARX-TS fuzzy model, a seismically excited three-story building equipped with an MR damper is ...

Research paper thumbnail of Nondestructive Evaluation of External Post-Tensioning Systems to Detect Grout Defects

Journal of Structural Engineering

Research paper thumbnail of Development of a New Manual for Assessing Safety Hardware TL-3 Low-Profile Portable Concrete Barrier for High-Speed Applications

Transportation Research Record: Journal of the Transportation Research Board

A sight-distance problem is associated with use of 32-in. tall concrete longitudinal barriers, sp... more A sight-distance problem is associated with use of 32-in. tall concrete longitudinal barriers, specifically in certain work zone locations and at nighttime. These 32-in. tall barriers can obstruct drivers’ eyesight, making it difficult for drivers to detect oncoming vehicles on the other side of these barriers. To address this sight-distance problem while protecting the errant vehicles, researchers at the Texas Transportation Institute (TTI) developed a 20-in. tall low-profile portable concrete barrier (PCB) for use in low-speed work zones in the early 1990s. To address the problem for high-speed application, TTI researchers applied modifications to the 20-in. tall low-profile PCB. Researchers designed two retrofit metal rail systems to be added on top of the existing 20-in. tall low-profile PCB to address roadside and median applications. The systems successfully performed in full-scale crash testing according to NCHRP Report 350 Test Level (TL) 3 evaluation criteria. This paper de...

Research paper thumbnail of Modeling ASR/DEF Expansion Strains in Large Reinforced Concrete Specimens

Journal of Structural Engineering

Research paper thumbnail of Monitoring of the Stress Free Temperature in Rails Using the Acoustoelastic Effect

AIP Conference Proceedings

Research paper thumbnail of Identification of the Impact Location on a Plate Using Wavelets

Mechanical Systems and Signal Processing

This paper presents an experimental method that has been developed for detecting flexural waves i... more This paper presents an experimental method that has been developed for detecting flexural waves in plates by the use of piezoelectric films. The recorded signals are analysed by a 'wavelet transform'to determine arrival times of waves at different frequencies. These ...

Research paper thumbnail of Nondestructive Testing of Overhead Transmission Lines—Numerical and Experimental Investigation

AIP Conference Proceedings

Research paper thumbnail of Energy-balance assessment of shape memory alloy-based seismic isolation devices

Smart Structures and Systems

Research paper thumbnail of Computational Modeling of Aramid Fiber-Reinforced Polymer Prestressed Girder in Composite Action with Bridge Deck

ACI Structural Journal

ABSTRACT Aramid fiber-reinforced polymer (AFRP) tendons, which are inherently corrosion-resistant... more ABSTRACT Aramid fiber-reinforced polymer (AFRP) tendons, which are inherently corrosion-resistant, can be used to replace steel prestressing strands in bridge girders to enhance bridge sustainability. Despite ongoing experimental research, there is a lack of uniformity and consistency in testing procedures, definitions of material characteristics, and results. Therefore, a robust computational model is needed to perform a refined nonlinear analysis of full-scale AFRP prestressed girders. This paper presents the development of a computational model to numerically evaluate the flexural behavior of an AASHTO I-girder (Type I) prestressed with AFRP tendons in comparison to its conventional prestressing steel counterpart. Numerical results match experimental test data with a high degree of accuracy and reveal that an AASHTO I-girder prestressed with AFRP meets service and strength limit states. Numerical results also show that the deflection equation in ACI 440.4R overestimates the maximum deflection of the AFRP prestressed girder.

Research paper thumbnail of Localization of notches with Lamb waves

Research paper thumbnail of Modelling and Control Techniques of an Active Vibration Isolation System

In the field of high-resolution measurement and manufacturing, effective anti-vibration measures ... more In the field of high-resolution measurement and manufacturing, effective anti-vibration measures are required to obtain precise and repeatable results. This is particularly true for experiments or processes where the typical amplitudes of the ambient vibration and the dimensions of the investigated or manufactured structures fall in the same range, e.g. submicron semiconductor production, holographic interferometry, confocal optical imaging, and scanning probe microscopy. In the active vibration isolation system examined, signals are acquired by extremely sensitive vibration detectors, and the vibration is reduced using either local analog feedback control or digital model-based control to drive electrodynamic actuators. This papers deals with the modelling and control techniques of such an active vibration isolation system. The modelling, parameter identification, and model updating procedure are described. The experimental setup for testing such an antivibration system is describe...

Research paper thumbnail of Systematic Assessment of Nondestructive Evaluation Techniques for External Post-tensioning and Stay Cable Systems

AbstractNondestructive evaluation (NDE) can provide invaluable information about the condition of... more AbstractNondestructive evaluation (NDE) can provide invaluable information about the condition of tendons in post-tensioned and cable-stayed bridges, which can facilitate preventative actions to mi...

Research paper thumbnail of Post-Tensioned Traffic Signal Structure: Experimental Natural Wind Response and Fatigue Assessment

Cantilevered traffic signal structures undergo wind-induced vibrations causing persistent stress ... more Cantilevered traffic signal structures undergo wind-induced vibrations causing persistent stress cycles that result in welded connection fatigue and fracture. A low-cost damage avoidance concept is proposed to apply post-tensioned prestress to eradicate the detrimental tensile mean stresses found in the tube-to-transverse end plate welded connections. A supplementary load path is introduced to balance the moments arising from the significant dead load associated with the cantilevered arm spanning the roadway, while offering a fail-safe mechanism. Field observations are made on a full-scale prototype structure in a natural wind environment without and with the proposed mitigation system installed; changes in the structure’s stress response are monitored. To quantify the benefit of the proposed system, the fatigue life is estimated using a deterministic framework considering the expected change in fatigue resistance and observed changes in natural wind response for two contrasting win...

Research paper thumbnail of Modelling bridge piers subject to alkali-silica reaction and delayed ettringite formation

Proceedings of the Institution of Civil Engineers - Bridge Engineering

Premature concrete deterioration in certain bridge piers in Texas, USA, has been attributed to th... more Premature concrete deterioration in certain bridge piers in Texas, USA, has been attributed to the deleterious effects of alkali–silica reaction and delayed ettringite formation. A semi-empirical e...

Research paper thumbnail of Nondestructive evaluation of grout defects in internal tendons of post-tensioned girders

NDT & E International

Abstract Post-tensioning systems provide safe and efficient construction solutions for long span ... more Abstract Post-tensioning systems provide safe and efficient construction solutions for long span bridges. Despite the improved grouting practices over the past decade, existing post-tensioning systems may have significant amount of grout defects, which could lead to corrosion of the strands. Condition assessment of post-tensioning systems is necessary to allow bridge owners to take timely, proactive actions to mitigate or prevent further deterioration and unanticipated tendon failures. A detailed experimental study conducted to assess the performance of nondestructive evaluation techniques in detecting grout defects within internal tendons is presented herein. Nondestructive evaluation techniques that include Ground Penetrating Radar, Impact Echo, Ultrasonic Tomography, and Ultrasonic Echo are evaluated in terms of detecting the location and severity of fabricated grout defects in a full-scale post-tensioned U-girder mock-up specimen. While Ground Penetrating Radar can identify the location and profile of the internal tendons, particularly metal ducts due to strong reflections, this method did not provide any information about the defect conditions within the tendon. Both Impact Echo and Ultrasonic Echo techniques are effective in identifying the location of grout defects, but could not differentiate between water, void, or compromised grout conditions. The study clearly demonstrates the need for NDE techniques that are applicable to anchorage regions, and that are capable of estimating the severity and nature of grout defects in internal tendons.

Research paper thumbnail of Concrete Tunnel Lining Evaluation Using Nondestructive Techniques: A Multi-method Case Study at Eisenhower Tunnel

An in-depth investigation of tunnel linings is performed at Eisenhower Tunnel, 60 miles west of D... more An in-depth investigation of tunnel linings is performed at Eisenhower Tunnel, 60 miles west of Denver, Colorado, using a combination of four nondestructive testing methods: air- and ground-coupled ground penetrating radar (GPR), ultrasonic echo (US echo), ultrasonic tomography (UST), and impact echo (IE). A robotic frame with pneumatically operated vacuum plates is used to automate GPR, US echo, and IE. UST was performed manually. These techniques are used to identify and locate the reinforcement mesh and structural steel ribs. Local changes in ultrasonic phase are calculated by phase analysis processing techniques and apparent relationships between positive and negative phase shifts and steel and air interfaces are observed. According to previous laboratory research, these relationships indicate the bonded state between the concrete and the embedded steel, but without ground truth verification this can only be suggested. It is shown that this combination of methods can be used synergistically to provide tunnel owners with the layout and possible condition of tunnel lining reinforcement and structural components.

Research paper thumbnail of Effect of Voids in Grouted, Post-Tensioned Concrete Bridge Construction: Volume 2–Inspection, Repair, Materials, and Risks

Research paper thumbnail of Nondestructive Evaluation Of Concrete Linings At Hanging Lake Tunnel

Research paper thumbnail of Use of Unmanned Marine Vehicles for Hurricane Damage Inspection

This paper describes the deployment of the custom Sea-RAI man-portable un-manned surface vehicle ... more This paper describes the deployment of the custom Sea-RAI man-portable un-manned surface vehicle and two commercially available underwater vehicles (the autonomous YSI EcoMapper and the tethered VideoRay) for inspection of the Rollover Pass bridge in the Bolivar ...

Research paper thumbnail of Experimental and computational investigation of a load-posted steel beam bridge

Research paper thumbnail of MIMO fuzzy identification of building-MR damper systems

Journal of Intelligent & Fuzzy Systems

This paper proposes a multi-input, multi-output (MIMO) nonlinear system identification (SI) of ci... more This paper proposes a multi-input, multi-output (MIMO) nonlinear system identification (SI) of civil structures equipped with magnetorheological (MR) dampers. The nonlinear SI model is developed through the integration of multiple MIMO autoregressive exogenous (ARX) input models, Takagi-Sugeno (TS) fuzzy model, weighted linear least squares, fuzzy C-means and subtractive clustering algorithms. To demonstrate the effectiveness of the MIMO ARX-TS fuzzy model, a seismically excited three-story building equipped with an MR damper is ...

Research paper thumbnail of Nondestructive Evaluation of External Post-Tensioning Systems to Detect Grout Defects

Journal of Structural Engineering

Research paper thumbnail of Development of a New Manual for Assessing Safety Hardware TL-3 Low-Profile Portable Concrete Barrier for High-Speed Applications

Transportation Research Record: Journal of the Transportation Research Board

A sight-distance problem is associated with use of 32-in. tall concrete longitudinal barriers, sp... more A sight-distance problem is associated with use of 32-in. tall concrete longitudinal barriers, specifically in certain work zone locations and at nighttime. These 32-in. tall barriers can obstruct drivers’ eyesight, making it difficult for drivers to detect oncoming vehicles on the other side of these barriers. To address this sight-distance problem while protecting the errant vehicles, researchers at the Texas Transportation Institute (TTI) developed a 20-in. tall low-profile portable concrete barrier (PCB) for use in low-speed work zones in the early 1990s. To address the problem for high-speed application, TTI researchers applied modifications to the 20-in. tall low-profile PCB. Researchers designed two retrofit metal rail systems to be added on top of the existing 20-in. tall low-profile PCB to address roadside and median applications. The systems successfully performed in full-scale crash testing according to NCHRP Report 350 Test Level (TL) 3 evaluation criteria. This paper de...

Research paper thumbnail of Modeling ASR/DEF Expansion Strains in Large Reinforced Concrete Specimens

Journal of Structural Engineering

Research paper thumbnail of Monitoring of the Stress Free Temperature in Rails Using the Acoustoelastic Effect

AIP Conference Proceedings

Research paper thumbnail of Identification of the Impact Location on a Plate Using Wavelets

Mechanical Systems and Signal Processing

This paper presents an experimental method that has been developed for detecting flexural waves i... more This paper presents an experimental method that has been developed for detecting flexural waves in plates by the use of piezoelectric films. The recorded signals are analysed by a 'wavelet transform'to determine arrival times of waves at different frequencies. These ...

Research paper thumbnail of Nondestructive Testing of Overhead Transmission Lines—Numerical and Experimental Investigation

AIP Conference Proceedings

Research paper thumbnail of Energy-balance assessment of shape memory alloy-based seismic isolation devices

Smart Structures and Systems

Research paper thumbnail of Computational Modeling of Aramid Fiber-Reinforced Polymer Prestressed Girder in Composite Action with Bridge Deck

ACI Structural Journal

ABSTRACT Aramid fiber-reinforced polymer (AFRP) tendons, which are inherently corrosion-resistant... more ABSTRACT Aramid fiber-reinforced polymer (AFRP) tendons, which are inherently corrosion-resistant, can be used to replace steel prestressing strands in bridge girders to enhance bridge sustainability. Despite ongoing experimental research, there is a lack of uniformity and consistency in testing procedures, definitions of material characteristics, and results. Therefore, a robust computational model is needed to perform a refined nonlinear analysis of full-scale AFRP prestressed girders. This paper presents the development of a computational model to numerically evaluate the flexural behavior of an AASHTO I-girder (Type I) prestressed with AFRP tendons in comparison to its conventional prestressing steel counterpart. Numerical results match experimental test data with a high degree of accuracy and reveal that an AASHTO I-girder prestressed with AFRP meets service and strength limit states. Numerical results also show that the deflection equation in ACI 440.4R overestimates the maximum deflection of the AFRP prestressed girder.