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Papers by Rigoberto Burgueño
This paper presents how the length of the critical plastic region (Lpr) in slender columns is sig... more This paper presents how the length of the critical plastic region (Lpr) in slender columns is significantly larger than what is estimated from current models, which were developed for shorter columns. Experimental results from three large-scale slender reinforced concrete columns with aspect ratios (length to depth) up to 12 were used to explore the effect of slenderness on Lpr. Components of Lpr, including linear moment gradient, nonlinear moment gradient, and tension shift effect were extracted from the test data and the contribution from each component was determined. Experimental Lpr values were compared with American, European, and New Zealand design guidelines. All design codes considered in this study significantly underestimated Lpr except for seismic design provisions provided by Caltrans. Previous expressions for the length of the plastic region were reexamined in light of the new experimental data and strong disagreement between experimental and predicted Lpr was observed...
Open cell aluminum (Al) foams have been used as energy absorbers for decades. Their energy absorp... more Open cell aluminum (Al) foams have been used as energy absorbers for decades. Their energy absorption capacity can be enhanced by thickening the foam struts, or increasing the foam's relative density. However, the enhancement is compromised by the inherent characteristics of its stress–strain property relationship, whereby upon homogeneous strut thickening, an increase in the plateau stress without a reduction in densification strain cannot be achieved. In this work, to overcome this inherent barrier, nano-crystalline copper (Cu) was deposited onto the Al foam and novel 3-D Cu/Al, heterogeneously thickened, composite foam structured materials were fabricated and tested for the first time. A non-cyanide nano-crystalline copper electro-deposition system was setup for the coating of open-cell Al foam, and, the energy absorption capacity as a function of foam pore size and Cu coating thickness was investigated. A variety of characterization methods confirmed the nano-crystalline str...
The use of fiber-reinforced polymer (FRP) composites for new construction is still limited primar... more The use of fiber-reinforced polymer (FRP) composites for new construction is still limited primarily due to high costs and designs based on shapes best suitable to conventional materials. The layered and fiber dominated structure of FRP composites is most efficient when used under in-plane stress demands. Structural forms that most efficiently use tensile stress carrying capacity are membranes or thin shells. An analytical investigation is presented where an innovative optimization algorithm for the integrated shape and laminate optimization of free-form FRP shells was developed and used to generate two new bridge systems that efficiently use FRP composites in membrane-based forms. One concept makes use of a FRP membrane working compositely with a concrete slab to resist flexure while the second uses the FRP membrane in a dual suspension system supporting a deck through diaphragms. The resulting designs and a discussion on their performance under optimal and nonoptimal loading are p...
Natural fiber composites, or biocomposites, have recently gained much attention due to their low ... more Natural fiber composites, or biocomposites, have recently gained much attention due to their low cost, environmental friendliness, and their potential to compete with glass-fiber composites. The reported study demonstrates that biocomposites can be used for load-bearing components by improving their structural efficiency through cellular material arrangements. Laboratory-scale periodic cellular beams and plates were made from industrial hemp and flax fibers with unsaturated polyester resin. Material and structural performance was experimentally assessed and compared with results from short-fiber composite micro-mechanics models and sandwich analyses. Short-term analytical evaluation of full-scale cellular biocomposite components indicates that they can compete with components made from conventional materials.
AbstractIn this paper, three-dimensional (3D) continuum-based finite-element (FE) simulations are... more AbstractIn this paper, three-dimensional (3D) continuum-based finite-element (FE) simulations are implemented for estimating intermediate damage limit states in flexure-dominated ductile reinforced concrete (RC) bridge columns. Results from the 3D FE simulations were compared and validated against the experimental data from four large-scale tests. Statistical error measures and test analysis correlation metrics were utilized to quantitatively evaluate the accuracy of the models. The validated models were then applied to determine the intermediate damage limit states based on the simulation results. Onset of yielding was associated with the tensile strains on the extreme reinforcement, and compressive strains on the outer concrete surface elements were used to identify the initiation and significant growth of spalling of the cover concrete. The results show that the 3D FE simulations were efficient in predicting intermediate damage limit states in a consistent manner with the experim...
Bio-based clay/polymer nanocomposites using blends of styrene-based unsaturated polyester and epo... more Bio-based clay/polymer nanocomposites using blends of styrene-based unsaturated polyester and epoxidized methyl soyate were manufactured using solvent-based processing techniques. Four methods were evaluated to assess limitations related to solvent removal and incorporation of high clay and bio-resin content. Nanocomposite characterization was performed using electron microscopy and tensile tests. Solvent type, bio-resin addition sequence, and sonication energy were the key parameters governing processing efficiency and composite quality. Processes with bio-resin added after solvent removal show promise for the incorporation of high bio-resin and nanoclay contents. Use of acetone as a solvent with bio-resin added after solvent removal led to nanocomposites with good nanoclay dispersion and exfoliation, and high tensile modulus. Direct sonication in the base resin diluted with styrene led to enhanced and balanced gains in stiffness and toughness.
The buckling of cylindrical shells has long been regarded as an undesirable phenomenon, but incre... more The buckling of cylindrical shells has long been regarded as an undesirable phenomenon, but increasing interests on the development of active and controllable structures open new opportunities to utilize such unstable behavior. In this paper, approaches for modifying and controlling the elastic response of axially compressed laminated composite cylindrical shells in the far postbuckling regime are presented and evaluated. Three methods are explored (1) varying ply orientation and laminate stacking sequence; (2) introducing patterned material stiffness distributions; and (3) providing internal lateral constraints. Experimental data and numerical results show that the static and kinematic response of unstable mode branch switching during postbuckling response can be modified and potentially tailored.
Strand debonding is a common approach used to reduce cracking at the ends of pre-tensioned concre... more Strand debonding is a common approach used to reduce cracking at the ends of pre-tensioned concrete beams. While the method has been successful to some extent, end cracking of pre-tensioned beam ends continues to be a problem. Experimental and numerical approaches were conducted in this study in order to achieve a further understanding of strand debonding. Twenty-four small-scale prestressed concrete beam units were tested and used for the calibration of nonlinear finite element models simulating concrete-strand bond behavior, while three models of AASHTO box girders were established to investigate an incident of end cracking encountered in the manufacturing of a bridge girder. The numerical simulations were in good agreement with the experiment data and damage evidence on prestressed girders production indicating that the lack of bonding will maximize the dilation of strand after release in the debonded region and that such dilation may cause concrete damage in the debonded region ...
Volume 2: Modeling, Simulation and Control of Adaptive Systems; Integrated System Design and Implementation; Structural Health Monitoring
Recent advances in energy harvesting technologies have led to the development of self-powered mon... more Recent advances in energy harvesting technologies have led to the development of self-powered monitoring techniques that are energy-efficient. This study presents an intelligent damage identification strategy for plate-like structures based on the data provided by a network of self-powered sensors that communicate through a pulse switching protocol, which has been demonstrated as an effective means for minimizing communication energy demands. The energy-aware pulse switching communication architecture uses single pulses instead of multi-bit packets for information delivery, resulting in discrete binary data. A system employing such an energy-efficient technology requires dealing with power budgets for sensing and communication of binary data, which leads to time delay constraints. In this paper, a novel machine learning framework incorporating low-rank matrix decomposition, pattern recognition, and a statistical approach is proposed to overcome challenges inherent in algorithm desig...
International Journal of Structural and Civil Engineering Research
Caltrans Seismic design criteria (SDC) provides guidelines for designing bridge columns consideri... more Caltrans Seismic design criteria (SDC) provides guidelines for designing bridge columns considering the P-Delta effects in order to prevent destabilizing moments to become dominant. Caltrans SDC controls the P-Delta effects using a conservative limit for lateral displacement due to axial load, which is enforced by limiting the design target ductility demands on structural components. For columns with high P-Delta induced moments Caltrans requires the column to be analyzed using more advanced nonlinear time history analysis or the column should be redesigned to comply with Caltrans SDC guideline for ignoring the P-Delta effects. The intention of this research is to study the accuracy of the Caltrans SDC method in detecting the point which P-Delta effects can be ignored. When P-Delta effects can't be ignored engineering firms tend to redesign the columns (use bigger section sizes or increase the reinforcement ratio) in order to prevent performing more time consuming and computationally demanding nonlinear time history analysis or Incremental Dynamic Analysis (IDA) to justify the structural behavior with inclusion of the P-Delta effects. This research performs IDA on two similar columns which one of them comply with Caltrans Criterion and the other one fails to satisfy the maximum cap for P-Delta induced moment in order to ignore the P-Delta effects. This research provides suggestions on possible improvements for the Caltrans SDC criteria for ignoring the P-Delta effects.
International Journal of Structural and Civil Engineering Research
Nonlinear Static Analysis (NSA) is currently considered as one of the most commonly used methods ... more Nonlinear Static Analysis (NSA) is currently considered as one of the most commonly used methods to estimate capacity of structural components. It is relatively simple and computationally inexpensive to generate the force-displacement graph using pushover analysis, and unlike nonlinear dynamic analysis the obtained results can easily be interpreted. NSA has been the basis for multiple methods for designing columns with consideration of P-Delta effects. A precise solution for stability problem under dynamic loading requires consideration of the randomness of ground motions and material uncertainties. Static procedures such as NSA ignores the fact that characteristics of the ground motions such as intensity, frequency content, and duration varies from one earthquake record to the other. On the other hand, most engineering firms are reluctant to perform complex nonlinear time-history analysis due to its high computational cost and other inherent complexities. Among different methods which redesign columns for P-Delta effects using pushover analysis two methods which use same energy under force-displacement diagram and same effective stiffness at target ductility have been studied here. Caltrans SDC target ductility for single column bents supported on fixed foundation is considered as the design target. The main objective of this research is to identify the applicability regions of these two methods for designing RC bridge columns in order to compensate for P-Delta effects.
Journal of Bridge Engineering
Engineering Applications of Artificial Intelligence
Abstract Data mining methods have been widely used for structural health monitoring (SHM) and dam... more Abstract Data mining methods have been widely used for structural health monitoring (SHM) and damage identification for analysis of continuous signals. Nonetheless, the applicability and effectiveness of these techniques cannot be guaranteed when dealing with discrete binary and incomplete/missing signals (i.e., not continuous in time). In this paper a novel data interpretation framework for SHM with noisy and incomplete signals, using a through-substrate self-powered sensing technology, is presented within the context of artificial intelligence (AI). AI methods, namely, machine learning and pattern recognition, were integrated within the data interpretation framework developed for use in a practical engineering problem: data-driven SHM of plate-like structures. Finite element simulations on an aircraft stabilizer wing and experimental vibration tests on a dynamically loaded plate were conducted to validate the proposed framework. Machine learning algorithms, including support vector machine, k-nearest neighbor, and artificial neural networks, were integrated within the developed learning framework for performance assessment of the monitored structures. Different levels of harvested energy were considered to evaluate the robustness of the SHM system with respect to such variations. Results demonstrate that the SHM methodology employing the proposed machine learning-based data interpretation framework is efficient and robust for damage detection with incomplete and sparse/missing binary signals, overcoming the notable issue of energy availability for smart damage identification platforms being used in structural/infrastructure and aerospace health monitoring. The present study aims to advance data mining and interpretation techniques in the SHM domain, promoting the practical application of machine learning and pattern recognition with incomplete and missing/sparse signals in smart cities and smart infrastructure monitoring.
Expert Systems with Applications
Thin-Walled Structures
Abstract The multistable elastic behavior of a shallow dome with a cosine-curved profile is inves... more Abstract The multistable elastic behavior of a shallow dome with a cosine-curved profile is investigated in this work. The dome exhibits snap-through instability and could be used as a building block for energy dissipation mechanism in structures subjected to cyclic loading and high deformation demands. Numerical and experimental studies were carried on the geometric and material properties of the cosine-curved domes (CCD) under concentrated load at the apex. Finite element analyses (FEA), validated by experimental tests on 3D printed specimens, were conducted to study the controlling geometric and material properties of the CCD. Three types of response were recognized and discussed based on the force- and strain energy-displacement curves. Limitations on the geometric parameters that govern the recoverability of the original shape and the stability state upon load removal are also identified. In addition, empirical relations to estimate the limit-point load and displacement, and to characterize the snap-through response were developed. Good agreement was observed using the determined limits on the geometric parameters and the developed relations with the results from FEA and experimental tests.
This paper presents how the length of the critical plastic region (Lpr) in slender columns is sig... more This paper presents how the length of the critical plastic region (Lpr) in slender columns is significantly larger than what is estimated from current models, which were developed for shorter columns. Experimental results from three large-scale slender reinforced concrete columns with aspect ratios (length to depth) up to 12 were used to explore the effect of slenderness on Lpr. Components of Lpr, including linear moment gradient, nonlinear moment gradient, and tension shift effect were extracted from the test data and the contribution from each component was determined. Experimental Lpr values were compared with American, European, and New Zealand design guidelines. All design codes considered in this study significantly underestimated Lpr except for seismic design provisions provided by Caltrans. Previous expressions for the length of the plastic region were reexamined in light of the new experimental data and strong disagreement between experimental and predicted Lpr was observed...
Open cell aluminum (Al) foams have been used as energy absorbers for decades. Their energy absorp... more Open cell aluminum (Al) foams have been used as energy absorbers for decades. Their energy absorption capacity can be enhanced by thickening the foam struts, or increasing the foam's relative density. However, the enhancement is compromised by the inherent characteristics of its stress–strain property relationship, whereby upon homogeneous strut thickening, an increase in the plateau stress without a reduction in densification strain cannot be achieved. In this work, to overcome this inherent barrier, nano-crystalline copper (Cu) was deposited onto the Al foam and novel 3-D Cu/Al, heterogeneously thickened, composite foam structured materials were fabricated and tested for the first time. A non-cyanide nano-crystalline copper electro-deposition system was setup for the coating of open-cell Al foam, and, the energy absorption capacity as a function of foam pore size and Cu coating thickness was investigated. A variety of characterization methods confirmed the nano-crystalline str...
The use of fiber-reinforced polymer (FRP) composites for new construction is still limited primar... more The use of fiber-reinforced polymer (FRP) composites for new construction is still limited primarily due to high costs and designs based on shapes best suitable to conventional materials. The layered and fiber dominated structure of FRP composites is most efficient when used under in-plane stress demands. Structural forms that most efficiently use tensile stress carrying capacity are membranes or thin shells. An analytical investigation is presented where an innovative optimization algorithm for the integrated shape and laminate optimization of free-form FRP shells was developed and used to generate two new bridge systems that efficiently use FRP composites in membrane-based forms. One concept makes use of a FRP membrane working compositely with a concrete slab to resist flexure while the second uses the FRP membrane in a dual suspension system supporting a deck through diaphragms. The resulting designs and a discussion on their performance under optimal and nonoptimal loading are p...
Natural fiber composites, or biocomposites, have recently gained much attention due to their low ... more Natural fiber composites, or biocomposites, have recently gained much attention due to their low cost, environmental friendliness, and their potential to compete with glass-fiber composites. The reported study demonstrates that biocomposites can be used for load-bearing components by improving their structural efficiency through cellular material arrangements. Laboratory-scale periodic cellular beams and plates were made from industrial hemp and flax fibers with unsaturated polyester resin. Material and structural performance was experimentally assessed and compared with results from short-fiber composite micro-mechanics models and sandwich analyses. Short-term analytical evaluation of full-scale cellular biocomposite components indicates that they can compete with components made from conventional materials.
AbstractIn this paper, three-dimensional (3D) continuum-based finite-element (FE) simulations are... more AbstractIn this paper, three-dimensional (3D) continuum-based finite-element (FE) simulations are implemented for estimating intermediate damage limit states in flexure-dominated ductile reinforced concrete (RC) bridge columns. Results from the 3D FE simulations were compared and validated against the experimental data from four large-scale tests. Statistical error measures and test analysis correlation metrics were utilized to quantitatively evaluate the accuracy of the models. The validated models were then applied to determine the intermediate damage limit states based on the simulation results. Onset of yielding was associated with the tensile strains on the extreme reinforcement, and compressive strains on the outer concrete surface elements were used to identify the initiation and significant growth of spalling of the cover concrete. The results show that the 3D FE simulations were efficient in predicting intermediate damage limit states in a consistent manner with the experim...
Bio-based clay/polymer nanocomposites using blends of styrene-based unsaturated polyester and epo... more Bio-based clay/polymer nanocomposites using blends of styrene-based unsaturated polyester and epoxidized methyl soyate were manufactured using solvent-based processing techniques. Four methods were evaluated to assess limitations related to solvent removal and incorporation of high clay and bio-resin content. Nanocomposite characterization was performed using electron microscopy and tensile tests. Solvent type, bio-resin addition sequence, and sonication energy were the key parameters governing processing efficiency and composite quality. Processes with bio-resin added after solvent removal show promise for the incorporation of high bio-resin and nanoclay contents. Use of acetone as a solvent with bio-resin added after solvent removal led to nanocomposites with good nanoclay dispersion and exfoliation, and high tensile modulus. Direct sonication in the base resin diluted with styrene led to enhanced and balanced gains in stiffness and toughness.
The buckling of cylindrical shells has long been regarded as an undesirable phenomenon, but incre... more The buckling of cylindrical shells has long been regarded as an undesirable phenomenon, but increasing interests on the development of active and controllable structures open new opportunities to utilize such unstable behavior. In this paper, approaches for modifying and controlling the elastic response of axially compressed laminated composite cylindrical shells in the far postbuckling regime are presented and evaluated. Three methods are explored (1) varying ply orientation and laminate stacking sequence; (2) introducing patterned material stiffness distributions; and (3) providing internal lateral constraints. Experimental data and numerical results show that the static and kinematic response of unstable mode branch switching during postbuckling response can be modified and potentially tailored.
Strand debonding is a common approach used to reduce cracking at the ends of pre-tensioned concre... more Strand debonding is a common approach used to reduce cracking at the ends of pre-tensioned concrete beams. While the method has been successful to some extent, end cracking of pre-tensioned beam ends continues to be a problem. Experimental and numerical approaches were conducted in this study in order to achieve a further understanding of strand debonding. Twenty-four small-scale prestressed concrete beam units were tested and used for the calibration of nonlinear finite element models simulating concrete-strand bond behavior, while three models of AASHTO box girders were established to investigate an incident of end cracking encountered in the manufacturing of a bridge girder. The numerical simulations were in good agreement with the experiment data and damage evidence on prestressed girders production indicating that the lack of bonding will maximize the dilation of strand after release in the debonded region and that such dilation may cause concrete damage in the debonded region ...
Volume 2: Modeling, Simulation and Control of Adaptive Systems; Integrated System Design and Implementation; Structural Health Monitoring
Recent advances in energy harvesting technologies have led to the development of self-powered mon... more Recent advances in energy harvesting technologies have led to the development of self-powered monitoring techniques that are energy-efficient. This study presents an intelligent damage identification strategy for plate-like structures based on the data provided by a network of self-powered sensors that communicate through a pulse switching protocol, which has been demonstrated as an effective means for minimizing communication energy demands. The energy-aware pulse switching communication architecture uses single pulses instead of multi-bit packets for information delivery, resulting in discrete binary data. A system employing such an energy-efficient technology requires dealing with power budgets for sensing and communication of binary data, which leads to time delay constraints. In this paper, a novel machine learning framework incorporating low-rank matrix decomposition, pattern recognition, and a statistical approach is proposed to overcome challenges inherent in algorithm desig...
International Journal of Structural and Civil Engineering Research
Caltrans Seismic design criteria (SDC) provides guidelines for designing bridge columns consideri... more Caltrans Seismic design criteria (SDC) provides guidelines for designing bridge columns considering the P-Delta effects in order to prevent destabilizing moments to become dominant. Caltrans SDC controls the P-Delta effects using a conservative limit for lateral displacement due to axial load, which is enforced by limiting the design target ductility demands on structural components. For columns with high P-Delta induced moments Caltrans requires the column to be analyzed using more advanced nonlinear time history analysis or the column should be redesigned to comply with Caltrans SDC guideline for ignoring the P-Delta effects. The intention of this research is to study the accuracy of the Caltrans SDC method in detecting the point which P-Delta effects can be ignored. When P-Delta effects can't be ignored engineering firms tend to redesign the columns (use bigger section sizes or increase the reinforcement ratio) in order to prevent performing more time consuming and computationally demanding nonlinear time history analysis or Incremental Dynamic Analysis (IDA) to justify the structural behavior with inclusion of the P-Delta effects. This research performs IDA on two similar columns which one of them comply with Caltrans Criterion and the other one fails to satisfy the maximum cap for P-Delta induced moment in order to ignore the P-Delta effects. This research provides suggestions on possible improvements for the Caltrans SDC criteria for ignoring the P-Delta effects.
International Journal of Structural and Civil Engineering Research
Nonlinear Static Analysis (NSA) is currently considered as one of the most commonly used methods ... more Nonlinear Static Analysis (NSA) is currently considered as one of the most commonly used methods to estimate capacity of structural components. It is relatively simple and computationally inexpensive to generate the force-displacement graph using pushover analysis, and unlike nonlinear dynamic analysis the obtained results can easily be interpreted. NSA has been the basis for multiple methods for designing columns with consideration of P-Delta effects. A precise solution for stability problem under dynamic loading requires consideration of the randomness of ground motions and material uncertainties. Static procedures such as NSA ignores the fact that characteristics of the ground motions such as intensity, frequency content, and duration varies from one earthquake record to the other. On the other hand, most engineering firms are reluctant to perform complex nonlinear time-history analysis due to its high computational cost and other inherent complexities. Among different methods which redesign columns for P-Delta effects using pushover analysis two methods which use same energy under force-displacement diagram and same effective stiffness at target ductility have been studied here. Caltrans SDC target ductility for single column bents supported on fixed foundation is considered as the design target. The main objective of this research is to identify the applicability regions of these two methods for designing RC bridge columns in order to compensate for P-Delta effects.
Journal of Bridge Engineering
Engineering Applications of Artificial Intelligence
Abstract Data mining methods have been widely used for structural health monitoring (SHM) and dam... more Abstract Data mining methods have been widely used for structural health monitoring (SHM) and damage identification for analysis of continuous signals. Nonetheless, the applicability and effectiveness of these techniques cannot be guaranteed when dealing with discrete binary and incomplete/missing signals (i.e., not continuous in time). In this paper a novel data interpretation framework for SHM with noisy and incomplete signals, using a through-substrate self-powered sensing technology, is presented within the context of artificial intelligence (AI). AI methods, namely, machine learning and pattern recognition, were integrated within the data interpretation framework developed for use in a practical engineering problem: data-driven SHM of plate-like structures. Finite element simulations on an aircraft stabilizer wing and experimental vibration tests on a dynamically loaded plate were conducted to validate the proposed framework. Machine learning algorithms, including support vector machine, k-nearest neighbor, and artificial neural networks, were integrated within the developed learning framework for performance assessment of the monitored structures. Different levels of harvested energy were considered to evaluate the robustness of the SHM system with respect to such variations. Results demonstrate that the SHM methodology employing the proposed machine learning-based data interpretation framework is efficient and robust for damage detection with incomplete and sparse/missing binary signals, overcoming the notable issue of energy availability for smart damage identification platforms being used in structural/infrastructure and aerospace health monitoring. The present study aims to advance data mining and interpretation techniques in the SHM domain, promoting the practical application of machine learning and pattern recognition with incomplete and missing/sparse signals in smart cities and smart infrastructure monitoring.
Expert Systems with Applications
Thin-Walled Structures
Abstract The multistable elastic behavior of a shallow dome with a cosine-curved profile is inves... more Abstract The multistable elastic behavior of a shallow dome with a cosine-curved profile is investigated in this work. The dome exhibits snap-through instability and could be used as a building block for energy dissipation mechanism in structures subjected to cyclic loading and high deformation demands. Numerical and experimental studies were carried on the geometric and material properties of the cosine-curved domes (CCD) under concentrated load at the apex. Finite element analyses (FEA), validated by experimental tests on 3D printed specimens, were conducted to study the controlling geometric and material properties of the CCD. Three types of response were recognized and discussed based on the force- and strain energy-displacement curves. Limitations on the geometric parameters that govern the recoverability of the original shape and the stability state upon load removal are also identified. In addition, empirical relations to estimate the limit-point load and displacement, and to characterize the snap-through response were developed. Good agreement was observed using the determined limits on the geometric parameters and the developed relations with the results from FEA and experimental tests.