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Papers by Sergio Villar Salinas

Research paper thumbnail of Estimation of backbone model parameters for simulation of exposed column base plates

Journal of Constructional Steel Research, 2024

An approach is presented for the estimation of the parameters required to simulate the nonlinear ... more An approach is presented for the estimation of the parameters required to simulate the nonlinear monotonic (i.e., backbone) rotational response of Exposed-Column-Base-Plate (ECBP) connections subjected to moment and axial compression. A trilinear backbone curve is selected to represent the rotational response, defined by three deformation and two strength parameters; these properly represent the stiffness, strength, and ductility of the connections. This approach is accompanied by a tool to facilitate convenient estimation of the parameters. The approach is based on a combination of behavioral insights and physics-based models (for some parameters) as well as regression for other parameters, which are estimated from a dataset of eighty-four experiments on ECBP connections conducted over the last forty years in the United States, Europe, and Asia. Predictive equations are provided to estimate the various parameters defining the nonlinear response, and their efficacy is examined by comparing them with the test data; in addition, well-established techniques are implemented to avoid collinearity and the overfitting of regression models. The results show that the models presented in this work provide robust and accurate predictions for in-sample and out-of-sample data. Limitations are outlined.

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Research paper thumbnail of Influence of high axial compression ratios in RC columns on the seismic response of MRF buildings

Structural Engineering and Mechanics, 2024

Poorly designed reinforced concrete (RC) columns of actual moment-resisting frame (MRF) buildings... more Poorly designed reinforced concrete (RC) columns of actual moment-resisting frame (MRF) buildings can undergo Axial Compression Ratios (ACR) so high as their demand exceeds their capacity, even for serviceability gravity load combinations, this lack commonly leads to insufficient seismic strength. Nonetheless, many seismic design codes do not specify limits for ACR. The main contribution of this research is to investigate the need to limit the ACR in seismic design. For this purpose, three prototype 6 and 11-story RC MRF buildings are analyzed in this paper, these buildings have columns undergoing excessive ACR, according to the limits prescribed by standards. To better that situation, three types of alterations are performed: retrofitting the abovementioned overloaded columns by steel jacketing, increasing the concrete strength, and reducing the number of stories. Several finite element analyses are conducted using the well-known software SAP2000 and the results are used for further calculations. Code-type and pushover analyses are performed on the original and retrofitted buildings, the suitability of the other modified buildings is checked by code-type analyses only. The obtained results suggest that ACR is a rather reliable indicator of the final building strength, hence, apparently, limiting the ACR in the standards (for early stages of design) might avoid unnecessary verifications.

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Research paper thumbnail of Contribution of CFRP to the shear strength of retrofitted lightly-reinforced concrete panels

Journal of Building Engineering, 2021

Low-rise buildings with thin Reinforced Concrete (RC) walls that do not comply with the minimum w... more Low-rise buildings with thin Reinforced Concrete (RC) walls that do not comply with the minimum web shear reinforcement prescribed by current earthquake-resistant codes can be found in some Latin American countries. Previous experimental studies evidence that Carbon Fiber Reinforced Polymers (CFRP) strips may be used to retrofit RC walls for shear forces. The two models available in the literature to predict the contribution of CFRP to the shear strength of RC walls exclude key variables for assessing the seismic performance of lightlyreinforced concrete walls retrofitted with CFRP. In this research, a model for predicting the contribution of CFRP to the shear strength of lightly-reinforced concrete panels is initially developed. A model to correlate the contribution of CFRP to shear strength of lightly-reinforced concrete panels with that of thin and lightlyreinforced concrete walls is also proposed. The experimental program includes cyclic diagonal compression tests on fourteen lightly-reinforced concrete panels: one plain concrete panel and thirteen panels reinforced internally with web shear reinforcement-ratio equal to 0.11%; twelve retrofitted with CFRP, and one RC panel retrofitted with a concrete overlay conventionally reinforced with a welded-wire mesh. The CFRP configuration were diagonal or horizontal with one strip, and diagonal or horizontal with three strips. Three volumetric ratios of CFRP were studied in this research: 0.02%, 0.06% and 0.09%. The effectiveness of the configuration and volumetric-ratio of CFRP on performance of retrofitted panels was evaluated in terms of cracking patterns, failure modes, shear strength and energy dissipation capacity obtained from shear-strain curves measured during cyclic diagonal compression tests. The model proposed to predict the contribution of CFRP to the peak shear strength of retrofitted lightly-reinforced concrete panels depends on the properties, volumetric ratio and configuration of CFRP on the panel.

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Research paper thumbnail of Performance evaluation of structures with reinforced concrete columns retrofitted with steel jacketing

Journal of Building Engineering, 2021

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

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Research paper thumbnail of Qualification of Beam to Column Connections in Cold Formed Steel Frames

Revista de la Escuela Colombiana de Ingeniería, 2008

This paper describes the most important aspects of the second part of a cold formed steel member ... more This paper describes the most important aspects of the second part of a cold formed steel member connections research that is currently being done at the Universidad Nacional de Colombia. In this second stage the behaviour of two different connections are studied,, that is, extended continuity plates connection and side plates connection. This study looks at the results of a finite element analysis of the models, experimental testing on models (cyclic and monotonic tests), analysis and comparison between theoretical and experimental results, hysteretic curves of the connections, approximate calculation of energy dissipation coefficient for structures that use the types of connections studied, and finally, the application of whole results to cold formed steel frames design when these connections are used.

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Research paper thumbnail of Estimation of backbone model parameters for simulation of exposed column base plates

Journal of Constructional Steel Research, 2024

An approach is presented for the estimation of the parameters required to simulate the nonlinear ... more An approach is presented for the estimation of the parameters required to simulate the nonlinear monotonic (i.e., backbone) rotational response of Exposed-Column-Base-Plate (ECBP) connections subjected to moment and axial compression. A trilinear backbone curve is selected to represent the rotational response, defined by three deformation and two strength parameters; these properly represent the stiffness, strength, and ductility of the connections. This approach is accompanied by a tool to facilitate convenient estimation of the parameters. The approach is based on a combination of behavioral insights and physics-based models (for some parameters) as well as regression for other parameters, which are estimated from a dataset of eighty-four experiments on ECBP connections conducted over the last forty years in the United States, Europe, and Asia. Predictive equations are provided to estimate the various parameters defining the nonlinear response, and their efficacy is examined by comparing them with the test data; in addition, well-established techniques are implemented to avoid collinearity and the overfitting of regression models. The results show that the models presented in this work provide robust and accurate predictions for in-sample and out-of-sample data. Limitations are outlined.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Influence of high axial compression ratios in RC columns on the seismic response of MRF buildings

Structural Engineering and Mechanics, 2024

Poorly designed reinforced concrete (RC) columns of actual moment-resisting frame (MRF) buildings... more Poorly designed reinforced concrete (RC) columns of actual moment-resisting frame (MRF) buildings can undergo Axial Compression Ratios (ACR) so high as their demand exceeds their capacity, even for serviceability gravity load combinations, this lack commonly leads to insufficient seismic strength. Nonetheless, many seismic design codes do not specify limits for ACR. The main contribution of this research is to investigate the need to limit the ACR in seismic design. For this purpose, three prototype 6 and 11-story RC MRF buildings are analyzed in this paper, these buildings have columns undergoing excessive ACR, according to the limits prescribed by standards. To better that situation, three types of alterations are performed: retrofitting the abovementioned overloaded columns by steel jacketing, increasing the concrete strength, and reducing the number of stories. Several finite element analyses are conducted using the well-known software SAP2000 and the results are used for further calculations. Code-type and pushover analyses are performed on the original and retrofitted buildings, the suitability of the other modified buildings is checked by code-type analyses only. The obtained results suggest that ACR is a rather reliable indicator of the final building strength, hence, apparently, limiting the ACR in the standards (for early stages of design) might avoid unnecessary verifications.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Contribution of CFRP to the shear strength of retrofitted lightly-reinforced concrete panels

Journal of Building Engineering, 2021

Low-rise buildings with thin Reinforced Concrete (RC) walls that do not comply with the minimum w... more Low-rise buildings with thin Reinforced Concrete (RC) walls that do not comply with the minimum web shear reinforcement prescribed by current earthquake-resistant codes can be found in some Latin American countries. Previous experimental studies evidence that Carbon Fiber Reinforced Polymers (CFRP) strips may be used to retrofit RC walls for shear forces. The two models available in the literature to predict the contribution of CFRP to the shear strength of RC walls exclude key variables for assessing the seismic performance of lightlyreinforced concrete walls retrofitted with CFRP. In this research, a model for predicting the contribution of CFRP to the shear strength of lightly-reinforced concrete panels is initially developed. A model to correlate the contribution of CFRP to shear strength of lightly-reinforced concrete panels with that of thin and lightlyreinforced concrete walls is also proposed. The experimental program includes cyclic diagonal compression tests on fourteen lightly-reinforced concrete panels: one plain concrete panel and thirteen panels reinforced internally with web shear reinforcement-ratio equal to 0.11%; twelve retrofitted with CFRP, and one RC panel retrofitted with a concrete overlay conventionally reinforced with a welded-wire mesh. The CFRP configuration were diagonal or horizontal with one strip, and diagonal or horizontal with three strips. Three volumetric ratios of CFRP were studied in this research: 0.02%, 0.06% and 0.09%. The effectiveness of the configuration and volumetric-ratio of CFRP on performance of retrofitted panels was evaluated in terms of cracking patterns, failure modes, shear strength and energy dissipation capacity obtained from shear-strain curves measured during cyclic diagonal compression tests. The model proposed to predict the contribution of CFRP to the peak shear strength of retrofitted lightly-reinforced concrete panels depends on the properties, volumetric ratio and configuration of CFRP on the panel.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Performance evaluation of structures with reinforced concrete columns retrofitted with steel jacketing

Journal of Building Engineering, 2021

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Qualification of Beam to Column Connections in Cold Formed Steel Frames

Revista de la Escuela Colombiana de Ingeniería, 2008

This paper describes the most important aspects of the second part of a cold formed steel member ... more This paper describes the most important aspects of the second part of a cold formed steel member connections research that is currently being done at the Universidad Nacional de Colombia. In this second stage the behaviour of two different connections are studied,, that is, extended continuity plates connection and side plates connection. This study looks at the results of a finite element analysis of the models, experimental testing on models (cyclic and monotonic tests), analysis and comparison between theoretical and experimental results, hysteretic curves of the connections, approximate calculation of energy dissipation coefficient for structures that use the types of connections studied, and finally, the application of whole results to cold formed steel frames design when these connections are used.

Bookmarks Related papers MentionsView impact