Comparison of Spectral Density Models to Simulate Wind Records

Edén Bojórquez,Omar Payán-Serrano,Alfredo Reyes-Salazar,Adrián Pozos 대한토목학회 2017 KSCE JOURNAL OF CIVIL ENGINEERING Vol.21 No.4

Due to the lack of real wind records to perform dynamic analysis of structural systems, civil and structural engineers commonly use simplified and conservative approaches to consider the dynamic effects of wind. With the aim to provide wind records, several studies suggest that the use of spectral density models and configuration of basic wind speed and terrain roughness are adequate to simulate the velocity field of the turbulent wind; however, nowadays there is no enough information to conclude which is the best spectral density model to simulate wind records for various configurations of basic wind speed and terrain roughness. For this reason, in this paper different scenarios are simulated in order to study the behavior of six spectral density functions which are frequently used in wind engineering. It is observed that the models proposed by von Karman, von Karman-Harris and Solari are the best alternative to simulate wind records.

Prediction of hysteretic energy demands in steel frames using vector-valued IMs

Edén Bojórquez,Laura Astorga,Alfredo Reyes-Salazar,Amador Terán-Gilmore,Juan Velázquez-Dimas,Juan Bojórquez,Luz Rivera 국제구조공학회 2015 Steel and Composite Structures, An International J Vol.19 No.3

It is well known the importance of considering hysteretic energy demands for the seismic assessment and design of structures. In such a way that it is necessary to establish new parameters of the earthquake ground motion potential able to predict energy demands in structures. In this paper, several alternative vector-valued ground motion intensity measures (IMs) are used to estimate hysteretic energy demands in steel framed buildings under long duration narrow-band ground motions. The vectors are based on the spectral acceleration at first mode of the structure Sa(T1) as first component. As the second component, IMs related to peak, integral and spectral shape parameters are selected. The aim of the study is to provide new parameters or vector-valued ground motion intensities with the capacity of predicting energy demands in structures. It is concluded that spectral-shape-based vector-valued IMs. have the best relation with hysteretic energy demands in steel frames subjected to narrow-band earthquake ground motions.

Response transformation factors for deterministic-based and reliability-based seismic design

Edén Bojórquez,Juan Bojórquez,Sonia E. Ruiz,Alfredo Reyes-Salazar,Juan Velázquez-Dimas 국제구조공학회 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.46 No.6

One of the main requirements of the seismic design codes must be its easy application by structural engineers. The use of practically-applicable models or simplified models as single-degree-offreedom (SDOF) systems is a good alternative to achieve this condition. In this study, deterministic and probabilistic response transformation factors are obtained to evaluate the response in terms of maximum ductility and maximum interstory drifts of multi-degree-of-freedom (MDOF) systems based on the response of equivalent SDOF systems. For this aim, five steel frames designed with the Mexican City Building Code (MCBC) as well as their corresponding equivalent SDOF systems (which represent the characteristics of the frames) are analyzed. Both structural systems are subjected to ground motions records. For the MDOF and the simplified systems, incremental dynamic analyses IDAs are developed in first place, then, structural demand hazard curves are obtained. The ratio between the IDAs curves corresponding to the MDOF systems and the curves corresponding to the simplified models are used to obtain deterministic response transformation factors. On the other hand, demand hazard curves are used to calculate probabilistic response transformation factors. It was found that both approaches give place to similar results.

Estimation of peak wind response of building using regression analysis

Omar Payán-Serrano,Edén Bojórquez,Alfredo Reyes-Salazar,Jorge Ruiz-García 한국풍공학회 2019 Wind and Structures, An International Journal (WAS Vol.29 No.2

The maximum along-wind displacement of a considerable amount of building under simulated wind loads is computed with the aim to produce a simple prediction model using multiple regression analysis with variables transformation. The Shinozuka and Newmark methods are used to simulate the turbulent wind and to calculate the dynamic response, respectively. In order to evaluate the prediction performance of the regression model with longer degree of determination, two complex structural models were analyzed dynamically. In addition, the prediction model proposed is used to estimate and compare the maximum response of two test buildings studied with wind loads by other authors. Finally, it was proved that the prediction model is reliable to estimate the maximum displacements of structures subjected to the wind loads.

Multi-objective Optimization of Structural Steel Buildings under Earthquake Loads using NSGA-II and PSO

Manuel Barraza,Edén Bojórquez,Eduardo Fernández-González,Alfredo Reyes-Salazar 대한토목학회 2017 KSCE JOURNAL OF CIVIL ENGINEERING Vol.21 No.2

The aim of this study is to illustrate and compares the use of Genetic Algorithms (GAs) and Particle Swarm Optimization (PSO) for multi-objective optimization of two and three dimensional moment resisting steel structures subjected to earthquake loads. For this purpose, steel buildings with different characteristics are designed under earthquakes using the Non-dominated Sorting Genetic Algorithm (NSGA-II) and PSO as a tool to achieve the best structure in terms of: minimize the total structural weight (which is directly related with the costs), control of the maximum inter-story drift, and to satisfy the strength requirements of the AISC-LRFD specification. It is considered that all the steel structures are constituted by elements with W section (256 in total) taken from the LRFD-AISC Database. Although, the GAs and PSO are applied for moment resisting steel structures, the concepts can be extended for other structural systems. It is concluded that the use of NSGA-II and PSO reduce the structural weight and they are a very useful tools to improve the structural performance of the buildings. Finally, the structural buildings obtained via PSO are in general better solutions in comparison with the NSGA-II approach.

Control of peak floor accelerations of buildings under wind loads using tuned mass damper

Juan Acosta,Edén Bojórquez,Juan Bojórquez,Alfredo Reyes-Salazar,Omar Payán,Manuel Barraza,Juan Serrano 국제구조공학회 2022 Structural Engineering and Mechanics, An Int'l Jou Vol.81 No.1

Due to the frequency and magnitude of some loads produced by gusts of turbulent wind, building floors can develop lateral displacements and significant accelerations which can produce strong inertial forces on structural, non-structural elements and occupants. A device that can help to reduce the floor accelerations is the well-known Tuned Mass Damper (TMD); however, nowadays there is no enough information about its capacity in order to dissipate energy of turbulent wind loads. For this reason, in this paper different buildings with and without TMD are modeled and dynamically analyzed under simulated wind loads in order to study the reduction of peak floor accelerations. The results indicate that peak floor accelerations can be reduced up to 40% when TMD are incorporated in the buildings, which demonstrated that the Tuned Mass Damper is an efficient device to reduce the wind effects on tall buildings.

Seismic Hazard Maps Based on the Intensity Measure INp

Robespierre Chávez,Edén Bojórquez 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.1

In the present study, seismic hazard maps for a region of Mexico using the ground motion intensity measure INp which is based on the spectral shape parameter named Np are developed. The motivation to use this ground motion intensity measure to compute the seismic hazard is because recently it has been demonstrated its potential to predict the structural response of buildings subjected to earthquakes. In fact, several studies suggest that intensity measures based on Np are more efficient for nonlinear structural prediction compared with other parameters of the literature. The results of this study are presented as seismic hazard maps and uniform hazard spectra with 2 and 10% probability of exceedance in 50 years. It is important to say that this is the first time that seismic hazard maps using the ground motion intensity measure INp are developed.

Seismic response estimation of steel buildings with deep columns and PMRF

Alfredo Reyes-Salazar,Manuel E. Soto-López,José R. Gaxiola-Camacho,Edén Bojórquez,Arturo Lopez-Barraza 국제구조공학회 2014 Steel and Composite Structures, An International J Vol.17 No.4

The responses of steel buildings with perimeter moment resisting frames (PMRF) with medium size columns (W14) are estimated and compared with those of buildings with deep columns (W27), which are selected according to two criteria: equivalent resistance and equivalent weight. It is shown that buildings with W27 columns have no problems of lateral torsional, local or shear buckling in panel zone. Whether the response is larger for W14 or W27 columns, depends on the level of deformation, the response parameter and the structural modeling under consideration. Modeling buildings as two-dimensional structures result in an overestimation of the response. For multiple response parameters, the W14 columns produce larger responses for elastic behavior. The axial load on columns may be significantly larger for the buildings with W14 columns. The interstory displacements are always larger for W14 columns, particularly for equivalent weight and plane models, implying that using deep columns helps to reduce interstory displacements. This is particularly important for tall buildings where the design is usually controlled by the drift limit state. The interstory shears in interior gravity frames (GF) are significantly reduced when deep columns are used. This helps to counteract the no conservative effect that results in design practice, when lateral seismic loads are not considered in GF of steel buildings with PMRF. Thus, the behavior of steel buildings with deep columns, in general, may be superior to that of buildings with medium columns, using less weight and representing, therefore, a lower cost.

Review of Assumptions in Simplified Multi-Component and Codified Seismic Response Evaluation Procedures

Alfredo Reyes-Salazar,Achintya Haldar,Juana L. Rivera-Salas,Edén Bojórquez 대한토목학회 2015 KSCE JOURNAL OF CIVIL ENGINEERING Vol.19 No.5

Representation of an earthquake by orthogonal normal and principal components, accuracies of several rules to combine collinear and non-collinear responses of MDOF structures, and estimation of the relative importance of the effects of individual orthogonal components are addressed in this paper. Statistically there are no differences between normal and principal components in estimating axial load for the elastic case; the principal components, however, may produce about 11% larger axial load for the inelastic case. There are no major differences in estimating base shear in all cases. To combine the two horizontal components, the 30% and SRSS combination rules underestimate the collinear axial load by about 10%. For the case of three components, the underestimation by the 30% and SRSS rules are about 5% and 10%, respectively. When responses due to axial loads and bending moments are combined, the underestimation could be between 10 and 15% for both combination rules. The assumption that the vertical response is 2/3 of that of the horizontal component appears not to be very conservative. The assumption that the response produced by the minor horizontal component is 85% of that of the major horizontal component appears to be very conservative.

Demands and distribution of hysteretic energy in moment resistant self-centering steel frames

Arturo López-Barraza,Sonia E. Ruiz,Alfredo Reyes-Salazar,Edén Bojórquez 국제구조공학회 2016 Steel and Composite Structures, An International J Vol.20 No.5

Post-tensioned (PT) steel moment resisting frames (MRFs) with semi-rigid connections (SRC) can be used to control the hysteretic energy demands and to reduce the maximum inter-story drift (<i>γ</i>). In this study the seismic behavior of steel MRFs with PT connections is estimated by incremental nonlinear dynamic analysis in terms of dissipated hysteretic energy (<i>E_H</i>) demands. For this aim, five PT steel MRFs are subjected to 30 long duration earthquake ground motions recorded on soft soil sites. To assess the energy dissipated in the frames with PT connections, a new expression is proposed for the hysteretic behavior of semi-rigid connections validated by experimental tests. The performance was estimated not only for the global <i>E_H</i> demands in the steel frames; but also for, the distribution and demands of hysteretic energy in beams, columns and connections considering several levels of deformation. The results show that <i>E_H</i> varies with <i>γ</i>, and that most of <i>E_H</i> is dissipated by the connections. It is observed in all the cases a log-normal distribution of <i>E_H</i> through the building height. The largest demand of <i>E_H</i> occurs between 0.25 and 0.5 of the height. Finally, an equation is proposed to calculate the distribution of <i>E_H</i> in terms of the normalized height of the stories (<i>h</i>/<i>H</i>) and the inter-story drift.