An official website of the United States government
Fiber Bragg grating (FBG) sensors have been applied to assess strains, stresses, loads, corrosion, and temperature for structural health monitoring (SHM) of steel infrastructure, such as buildings, bridges, and pipelines. Since a single FBG sensor measures a particular parameter at a local spot, it is challenging to detect different types of anomalies and interactions of anomalies. This paper presents an approach to assess interactive anomalies caused by mechanical loading and corrosion on epoxy coated steel substrates using FBG sensors in real time. Experiments were performed by comparing the monitored center wavelength changes in the conditions with loading only, corrosion only, and simultaneous loading and corrosion. The theoretical and experimental results indicated that there were significant interactive influences between loading and corrosion for steel substrates. Loading accelerated the progress of corrosion for the epoxy coated steel substrate, especially when delamination in the epoxy coating was noticed. Through the real-time monitoring from the FBG sensors, the interactions between the anomalies induced by the loading and corrosion can be quantitatively evaluated through the corrosion depth and the loading contact length. These fundamental understandings of the interactions of different anomalies on steel structures can provide valuable information to engineers for better management of steel structures.
more »
« less
This content will become publicly available on June 1, 2025
Real-time Local Buckling Monitoring in Oil/gas Pipelines Using Fiber Optic Sensors
The occurrence of local buckling, an external anomaly in pipelines, significantly contributes to pipeline incidents, posing challenges in monitoring such localized anomalies, particularly during pipeline operations. This paper introduces an approach aimed at monitoring local buckling occurring in the compression bending area of pipeline sections. The proposed approach utilizes fiber Bragg gratings (FBGs) to facilitate real-time measurement of strain changes. Experimental tests were conducted on the steel pipe equipped with FBGs positioned near the top and bottom of the pipe, subjected to four-point loading test to generate bending and local buckling. The strain data obtained from FBGs enable effective detection and localization of bending and buckling deformations during the loading process. This research contributes to enhancing the capability to monitor external threats to pipelines, thereby fostering improved condition assessments and bolstering infrastructure resilience.
more »
« less
- Award ID(s):
- 1750316
- PAR ID:
- 10523409
- Publisher / Repository:
- Avestia
- Date Published:
- Format(s):
- Medium: X
- Location:
- University of Toronto, Toronto, Canada
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract Three-dimensional dynamics of flexible fibers in shear flow are studied numerically, with a qualitative comparison to experiments. Initially, the fibers are straight, with different orientations with respect to the flow. By changing the rotation speed of a shear rheometer, we change the ratioAof bending to shear forces. We observe fibers in the flow-vorticity plane, which gives insight into the motion out of the shear plane. The numerical simulations of moderately flexible fibers show that they rotate along effective Jeffery orbits, and therefore the fiber orientation rapidly becomes very close to the flow-vorticity plane, on average close to the flow direction, and the fiber remains in an almost straight configuration for a long time. This ‘ordering’ of fibers is temporary since they alternately bend and straighten while tumbling. We observe numerically and experimentally that if the fibers are initially in the compressional region of the shear flow, they can undergo compressional buckling, with a pronounced deformation of shape along their whole length during a short time, which is in contrast to the typical local bending that originates over a long time from the fiber ends. We identify differences between local and compressional bending and discuss their competition, which depends on the initial orientation of the fiber and the bending stiffness ratioA. There are two main finding. First, the compressional buckling is limited to a certain small range of the initial orientations, excluding those from the flow-vorticity plane. Second, since fibers straighten in the flow-vorticity plane while tumbling, the compressional buckling is transient—it does not appear for times longer than 1/4 of the Jeffery period. For larger times, bending of fibers is always driven by their ends.more » « less
-
attributed to loss of load carrying capacity of the individual members. Dominant failure modes in structural steel members include interactions between inelastic lateral torsional buckling, global buckling, and local buckling (referred to as Interactive Buckling). Accurate performance assessment of steel moment frames highly relies on the accuracy of the model-based simulations of such limit states. Commonly used concentrated hinge and fiber-based models fail to address the physics of this response leading to inaccurate performance assessment of structures. A nonlinear displacement-based fiber element [named Torsional Fiber Element (TFE)] to simulate monotonic and cyclic interactive buckling in steel members is proposed and implemented on OpenSees (an open-source finite element software). The element includes St. Venant as well as warping torsion response that are essential for lateral torsional buckling response in a wide-flange I-section, through enriched displacement fields and strain interpolation. Response of local buckling is represented in a quantitative manner using a novel multi-axial constitutive relationship with calibration of an effective softening behavior in the post-buckling response. Mesh dependency issue related to the softening material model is also discussed and addressed through a proposed non-local strain measure. The efficacy of the model is assessed through several continuum finite element simulations and experimental data.more » « less
-
Abstract Buckling, a phenomenon historically considered undesirable, has recently been harnessed to enable innovative functionalities in materials and structures. While approaches to achieve specific buckling behaviors are widely studied, tuning these behaviors in fabricated structures without altering their geometry remains a major challenge. Here, we introduce an inverse design approach to tune buckling behavior in magnetically active structures through the variation of applied magnetic stimuli. Our proposed magneto-mechanical topology optimization formulation not only generates the geometry and magnetization distribution of these structures but also informs how the external magnetic fields should be applied to control their buckling behaviors. By utilizing the proposed strategy, we discover magnetically active structures showcasing a broad spectrum of tunable buckling mechanisms, including programmable peak forces and buckling displacements, as well as controllable mechano- and magneto-induced bistability. Furthermore, we experimentally demonstrate that multiple unit designs can be assembled into architectures, resulting in tunable multistability and programmable buckling sequences under distinct applied magnetic fields. By employing a hybrid fabrication method, we manufacture and experimentally validate the generated designs and architectures, confirming their ability to exhibit precisely programmed and tunable buckling behaviors. This research contributes to the advancement of multifunctional materials and structures that harness buckling phenomena, unlocking transformative potential for various applications, including robotics, energy harvesting, and deployable and reconfigurable devices.more » « less
-
Thin (slender) steel plates possess shear strength beyond the elastic buckling load which is commonly referred to as the post-buckling capacity. Semi-empirical equations based on experimental tests of plate girders have been used for decades to predict the ultimate post-buckling strength of slender webs. However, several recent studies have shown that the current models for predicting the ultimate shear post-buckling capacity of thin plates are based on some incorrect assumptions regarding their mechanical behavior. As a result, the current design equations provide an approximate estimate of capacity for the range of parameters in the test data upon which they are founded. This paper explores the fundamental behavior of thin plates under pure shear. Such a fundamental examination of shear post-buckling behavior in thin plates is needed to enable design procedures that can optimize a plate’s shear strength and load-deformation performance for a wider range of loading and design parameters. Using finite element analyses, which are validated against available results of previous experimental tests, outputs such as plastic strains, von Mises stresses, principal stresses, and principal stress directions are examined on a buckled plate acting in pure shear. The internal bending, shear, and membrane stresses in the plate’s finite elements are also evaluated. In this study, these evaluations are performed for a simply-supported plate with an aspect ratio equal to 1.0 and slenderness ratio equal to 134. Results show that localized bending in the plates due to the out-of-plane post-buckling deformations appear to be a significant factor in the ultimate shear post-buckling capacity of the plate. Also, the compressive stresses continue to increase beyond the onset of elastic buckling in some regions of the plate, contrary to current design assumptions. Overall, this study provides new insights into the mechanics of shear post-buckling behavior of thin plates that can be exploited for design procedures that are consistent with mechanical behavior.more » « less
