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28 pages, 19661 KiB

Open AccessArticle

Open Ground Story Mid-Rise Buildings Represented by Simplified Systems

by José L. Cabrera, Sonia E. Ruiz and Amador Teran-Gilmore

Buildings 2024, 14(5), 1269; https://doi.org/10.3390/buildings14051269 - 1 May 2024

Cited by 1 | Viewed by 1031

An improved methodology for the condensation of Multi-Degree-Of-Freedom (MDOF) systems to equivalent Two-Degree-Of-Freedom (2EDOF) systems is presented. The methodology is applied to mid-rise buildings with Open Ground-Story and verified by means of Nonlinear Time History Analyses. The buildings studied are divided into two [...] Read more.

An improved methodology for the condensation of Multi-Degree-Of-Freedom (MDOF) systems to equivalent Two-Degree-Of-Freedom (2EDOF) systems is presented. The methodology is applied to mid-rise buildings with Open Ground-Story and verified by means of Nonlinear Time History Analyses. The buildings studied are divided into two main segments: (a) ground story, whose stiffness and lateral strength are both provided only by reinforced concrete moment-resisting frames; and (b) from the second story to the roof, whose stiffness and lateral strength are provided by confined masonry walls. The proposed methodology allows us to do the following: (a) get the closest approximation to the real behavior of the MDOF system through the use of hysteresis rules with strength and stiffness degradation in the simplified system; (b) analyze the behavior of an OGS whose lateral stiffness is lower than the stiffness of the stories above; and (c) identify in which of the two subsystems (either the ground story with reinforced concrete frames or the second story with masonry) the maximum seismic demand of non-linear behavior occurs. For most of the cases studied and different scenarios of non-linear behavior, the 2EDOF simplified system reasonably approximates the MDOF system’s response; however, when a local failure in an upper story causes the collapse mechanism, the 2EDOF system does not adequately approximate the response of the MDOF system. Full article

(This article belongs to the Special Issue Structural Engineering in Building)

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27 pages, 14497 KiB

Open AccessArticle

Seismic Performance of Steel Buildings with Eccentrically Braced Frame Systems with Different Configurations

by Juan Acosta, Edén Bojórquez, Juan Bojórquez, Alfredo Reyes-Salazar, Jorge Ruiz-García, Sonia E. Ruiz and Ivano Iovinella

Buildings 2024, 14(1), 118; https://doi.org/10.3390/buildings14010118 - 2 Jan 2024

Cited by 1 | Viewed by 2421

Abstract

Although eccentrically braced frames (EBFs) can be used with different configurations according to architectural requirements, it has not yet been indicated which configuration has a better seismic performance; therefore, this paper presents an analytical study focused on evaluating the seismic behavior of various [...] Read more.

Although eccentrically braced frames (EBFs) can be used with different configurations according to architectural requirements, it has not yet been indicated which configuration has a better seismic performance; therefore, this paper presents an analytical study focused on evaluating the seismic behavior of various steel buildings with EBF systems, factoring in different configurations. Furthermore, the objective is to compare the performances of EBF systems with one another, to learn more about their structural efficiency. The results obtained indicate that seismic response, in terms of peak interstory drifts, depends on the structural period and hysteretic behavior of the links, because high levels of plastic rotation increase lateral displacement. In addition, it was observed that maximum drift demands are concentrated in the lower floors where the links exhibit inelastic behavior, while the level of interstory drift decreases as height increases. Full article

(This article belongs to the Special Issue Structural Engineering in Building)

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19 pages, 9923 KiB

Open AccessArticle

Estimation of Uniform Risk Spectra Suitable for the Seismic Design of Structures

by Luis Buendía, Mauro Niño, Eduardo Reinoso and Carlos González

Buildings 2023, 13(9), 2165; https://doi.org/10.3390/buildings13092165 - 26 Aug 2023

Viewed by 1534

Abstract

The aim of this paper is to present a performance-based method to estimate uniform risk spectra (URS) for the seismic design and assessment of structures. These spectra, computed with the proposed methodology, provide the lateral capacity (in terms of spectral acceleration) that should [...] Read more.

The aim of this paper is to present a performance-based method to estimate uniform risk spectra (URS) for the seismic design and assessment of structures. These spectra, computed with the proposed methodology, provide the lateral capacity (in terms of spectral acceleration) that should be given to a structure, characterized by a reference single degree of freedom system, to achieve a predetermined exceedance rate of economic loss. This procedure involves the seismic hazard assessment necessary to define a seismic design level consistent with the accepted loss value, using a large enough number of synthetic seismic records of several magnitudes, which were obtained by means of an improved empirical Green function method. The statistics of the expected losses of a reference single degree of freedom system are obtained using Monte Carlo simulation, considering the seismic demand and the lateral strength of the structure as random variables. The method is divided into two main stages: (1) definition of the seismic hazard at the site of interest and (2) the probabilistic analysis of the seismic performance in terms of an economical loss ratio of nonlinear SDOF. To illustrate the proposed methodology and, subsequently, to validate it, a URS was computed for a site located in the Mexico City lake-bed zone, and its use in the design of three reinforced concrete frames is shown. The results show that the proposed spectra provide a sufficient approximation between the seismic risk level considered in the seismic design and that of the designed structure. It is concluded that the proposed procedure is a significant improvement over others considered in the literature and a useful research tool for the further development of risk-based earthquake engineering. Full article

(This article belongs to the Special Issue Structural Engineering in Building)

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20 pages, 4408 KiB

Open AccessArticle

Improving the Seismic Performance of Steel Frames under Mainshock–Aftershock Using Post-Tensioned Connections

by José R. Torres, Edén Bojórquez, Juan Bojórquez, Herian Leyva, Sonia E. Ruiz, Alfredo Reyes-Salazar, Leonardo Palemón-Arcos, J. Luz Rivera, Joel Carvajal and Henry E. Reyes

Buildings 2023, 13(7), 1676; https://doi.org/10.3390/buildings13071676 - 29 Jun 2023

Cited by 2 | Viewed by 1236

Abstract

In this study, the seismic responses of moment-resisting steel frames (MRSFs) with welded and post-tensioned connections under 28 artificial seismic sequences (mainshock–aftershock) are compared. For this aim, the mainshock are scaled at different ground motion intensity levels as a function of the spectral [...] Read more.

In this study, the seismic responses of moment-resisting steel frames (MRSFs) with welded and post-tensioned connections under 28 artificial seismic sequences (mainshock–aftershock) are compared. For this aim, the mainshock are scaled at different ground motion intensity levels as a function of the spectral pseudo-acceleration corresponding to the fundamental period of vibration of the structure Sa(T₁), whereas different intensity levels of the aftershocks are used for a percentage of the peak maximum acceleration of the mainshock. The seismic performance comparison of both structural systems is computed for the maximum, residual inter-story drift and hysteretic energy demands. The results show that post-tensioned frames significantly reduce the structural demands, especially in the case of residual inter-story drifts and hysteretic energy in comparison with moment-resisting steel frames with welded connections. The reductions in the structural response tend to be larger as the intensity of the aftershock tends to increase. Therefore, it is concluded that the use of post-tensioned connections is a great alternative to mitigate the seismic response of buildings subjected to seismic sequences. Full article

(This article belongs to the Special Issue Structural Engineering in Building)

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25 pages, 12299 KiB

Open AccessArticle

Functionality Loss and Recovery Time Models for Structural Elements, Non-Structural Components, and Delay Times to Estimate the Seismic Resilience of Mexican School Buildings

by Carlos González, Mauro Niño and Gustavo Ayala

Buildings 2023, 13(6), 1498; https://doi.org/10.3390/buildings13061498 - 10 Jun 2023

Cited by 2 | Viewed by 1693

Abstract

Concerns about prolonged downtime and functionality losses observed after recent seismic events have made it clear that seismic design is heading towards a resilience-based approach. However, there is still currently no clear consensus on how to quantify and interpret resilience. In this document, [...] Read more.

Concerns about prolonged downtime and functionality losses observed after recent seismic events have made it clear that seismic design is heading towards a resilience-based approach. However, there is still currently no clear consensus on how to quantify and interpret resilience. In this document, a probabilistic approach to estimate recovery times and functionality loss in buildings is presented, which allows for the estimation of seismic resilience through consideration of delay times and the behavior of non-structural elements. To achieve these goals, simple models that associate structural response and the resilience parameters (recovery time and functionality) are defined. The proposed approach was implemented in a database for public school buildings in Puebla City, where the expected times and functionality were obtained, thus allowing for quantification of the seismic resilience of each structure. Furthermore, target values for low and high resilience are proposed, which helps to identify the weakest elements in the educative Mexican infrastructure. The results showed that the inclusion of delay times and non-structural elements in resilience quantification is mandatory if an overestimation of resilience values is to be avoided. At the same time, the target values allow for the different structures to be categorized according to the resilience values obtained, finding that a significant portion of Mexican school buildings are underprepared in a resilience context. Full article

(This article belongs to the Special Issue Structural Engineering in Building)

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31 pages, 9028 KiB

Open AccessArticle

Seismic Risk of Weak First-Story RC Structures with Inerter Dampers Subjected to Narrow-Band Seismic Excitations

by Miguel A. Jaimes, Mauro Niño, Isaac Franco, Salatiel Trejo, Francisco A. Godínez and Adrián D. García-Soto

Buildings 2023, 13(4), 929; https://doi.org/10.3390/buildings13040929 - 31 Mar 2023

Viewed by 1829

Abstract

This study evaluates the seismic risk of weak first-story reinforced concrete (RC) structures retrofitted with inerter dampers at their ground level when subjected to narrow-band seismic excitations. The main advantages brought about by the ground-level inerters are the reductions in seismic demands (e.g., [...] Read more.

This study evaluates the seismic risk of weak first-story reinforced concrete (RC) structures retrofitted with inerter dampers at their ground level when subjected to narrow-band seismic excitations. The main advantages brought about by the ground-level inerters are the reductions in seismic demands (e.g., drifts, floor accelerations). This study shows that structures with inerters are reliable systems in terms of peak story drifts for large ground motions. For moderate ground-motion intensities, the opposite could occur, mainly for soft soil sites. The reliabilities of structures with inerter dampers at their ground level are in general higher for buildings under seismic intensities associated to limit state of incipient collapse, especially for low-height buildings. This could be reversed for intensities associated to the limit state of damage limitation. The findings of this study could guide practicing engineers to use inerter-based dampers in retrofitting ductile structures consisting of moment-resisting reinforced concrete (RC) frames subjected to narrow-band earthquake excitations in regions such as Mexico City. Full article

(This article belongs to the Special Issue Structural Engineering in Building)

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19 pages, 7255 KiB

Open AccessArticle

Vector-Valued Intensity Measures Based on Spectral Shape to Predict Seismic Fragility Surfaces in Reinforced Concrete Buildings

by Noel Zavala, Edén Bojórquez, Manuel Barraza, Juan Bojórquez, Almendra Villela, José Campos, José Torres, Ricardo Sánchez and Joel Carvajal

Buildings 2023, 13(1), 137; https://doi.org/10.3390/buildings13010137 - 5 Jan 2023

Cited by 3 | Viewed by 1775

Abstract

Although some studies have been conducted to compute fragility surfaces of buildings using vector-valued seismic intensity measures (IMs), in all the cases, the first component of the vector usually is the spectral acceleration at first mode of vibration of the structure Sa(T₁ [...] Read more.

Although some studies have been conducted to compute fragility surfaces of buildings using vector-valued seismic intensity measures (IMs), in all the cases, the first component of the vector usually is the spectral acceleration at first mode of vibration of the structure Sa(T₁). In this study, fragility surfaces of three reinforced concrete buildings (RCB) subjected to narrow-band ground motions obtained from soft soil of Mexico City are computed considering vector-valued IMs based not only on Sa(T₁), but also the velocity V(T₁), pseudo-velocity Sv(T₁), and normalized input energy by the mass E_I/m(T₁) as the first component. As second component of the vector-valued IMs, the Peak Ground Acceleration (PGA), Peak Ground Velocity (PGV), effective duration (t_D), earthquake damage potential (I_D) and four Np spectral shape-based parameters obtained through spectral acceleration (Np_Sa), velocity (Np_V), pseudo-velocity (Np_Sv), and input energy (Np_EI) have been analyzed. In order to obtain fragility surfaces, Multinomial Logistic Regression (MLR) was applied. It is observed that those vector-valued IMs based on the spectral shape proxies were more efficient to predict the probability of failure of RCB. For this reason, it is important to consider spectral shape vector-valued IMs in order to reduce uncertainty in the structural response of buildings under earthquakes. Thus, the use of two parameters instead of a single intensity measure improves the efficiency. Moreover, the fragility surfaces can be used for the seismic risk evaluation of buildings. Full article

(This article belongs to the Special Issue Structural Engineering in Building)

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21 pages, 6319 KiB

Open AccessArticle

Experimental Study on Characteristics of Pile-Soil Interaction in Screw Piles

by Jiakuan Ma, Lijuan Luo, Tong Mu, Hongtao Guo and Yong Tang

Buildings 2022, 12(12), 2091; https://doi.org/10.3390/buildings12122091 - 29 Nov 2022

Cited by 3 | Viewed by 3253

Abstract

A screw pile is a special-shaped pile with several advantages, including good bearing capacity, economy, and rapid construction. The calculation of the screw piles’ ultimate bearing capacity in the individual bearing failure state remains controversial. To address the problems of an unclear failure [...] Read more.

A screw pile is a special-shaped pile with several advantages, including good bearing capacity, economy, and rapid construction. The calculation of the screw piles’ ultimate bearing capacity in the individual bearing failure state remains controversial. To address the problems of an unclear failure mechanism and the pile–soil contact relationship in screw piles, we conducted large-scale direct shear tests using a partial amplification method. The variation law for soil stress and the failure pattern of soil around the screw teeth were analyzed. The bearing capacity of the screw shear plate with screw teeth was found to be significantly higher than that of the plane shear plate, while that of the screw pile first increased and then decreased with an increase in the screw pitch. The optimal screw pitch allowed the determination of the maximum bearing capacity. Furthermore, the optimal screw pitch was generally equal to the critical screw pitch, which distinguished the individual bearing failure from the cylindrical shearing failure. A new calculation method for the critical screw pitch and ultimate bearing capacity in the individual bearing failure state was presented, and its rationality was proved using the direct shear test results. The calculation of the critical screw pitch considers the shear strength of soil and the geometric parameters of the screw teeth, making it more widely applicable. These results can provide a theoretical basis for the subsequent design of screw piles. Full article

(This article belongs to the Special Issue Structural Engineering in Building)

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