Evaluation of performance of eccentric braced frame with friction damper

Vaseghi Amiri, J.,Navayinia, B.,Navaei, S. Techno-Press 2011 Structural Engineering and Mechanics, An Int'l Jou Vol.39 No.5

Nonlinear dynamic analysis and evaluation of eccentric braced steel frames (EBF) equipped with friction damper (FD) is studied in this research. Previous studies about assessment of seismic performance of steel braced frame with FD have been generally limited to installing this device in confluence of cross in concentrically braced frame such chevron and x-bracing. Investigation is carried out with three types of steel frames namely 5, 10 and 15 storeys, representing the short, medium and high structures respectively in series of nonlinear dynamic analysis and 10 slip force values subjected to three different earthquake records. The proper place of FD, rather than providing them at all level is also studied in 15 storey frame. Four dimensionless indices namely roof displacement, base shear, dissipated energy and relative performance index (RPI) are determined in about 100 nonlinear dynamic analyses. Then average values of maximum roof displacement, base shear, energy dissipated and storey drift under three records for both EBF and EBF equipped with friction damper are obtained. The result indicates that FD reduces the response compared to EBF and is more efficient than EBF for taller storey frames.

Evaluation of performance of eccentric braced frame with friction damper

J. Vaseghi Amiri,B. Navayinia,S. Navaei 국제구조공학회 2011 Structural Engineering and Mechanics, An Int'l Jou Vol.39 No.5

Nonlinear dynamic analysis and evaluation of eccentric braced steel frames (EBF) equipped with friction damper (FD) is studied in this research. Previous studies about assessment of seismic performance of steel braced frame with FD have been generally limited to installing this device in confluence of cross in concentrically braced frame such chevron and x-bracing. Investigation is carried out with three types of steel frames namely 5, 10 and 15 storeys, representing the short, medium and high structures respectively in series of nonlinear dynamic analysis and 10 slip force values subjected to three different earthquake records. The proper place of FD, rather than providing them at all level is also studied in 15 storey frame. Four dimensionless indices namely roof displacement, base shear, dissipated energy and relative performance index (RPI) are determined in about 100 nonlinear dynamic analyses. Then average values of maximum roof displacement, base shear, energy dissipated and storey drift under three records for both EBF and EBF equipped with friction damper are obtained. The result indicates that FD reduces the response compared to EBF and is more efficient than EBF for taller storey frames.

Probabilistic evaluation of separation distance between two adjacent structures

Naeej, Mojtaba,Amiri, Javad Vaseghi,Jalali, Sayyed Ghasem Techno-Press 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.67 No.5

Structural pounding is commonly observed phenomenon during major ground motion, which can cause both structural and architectural damages. To reduce the amount of damage from pounding, the best and effective way is to increase the separation distance. Generally, existing design procedures for determining the separation distance between adjacent buildings subjected to structural pounding are based on approximations of the buildings' peak relative displacement. These procedures are based on unknown safety levels. The aim of this research is to estimate probabilistic separation distance between adjacent structures by considering the variability in the system and uncertainties in the earthquakes characteristics through comprehensive numerical simulations. A large number of models were generated using a robust Monte-Carlo simulation. In total, 6.54 million time-history analyses were performed over the adopted models using an ensemble of 25 ground motions as seismic input within OpenSees software. The results show that a gap size of 50%, 70% and 100% of the considered design code for the structural periods in the range of 0.1-0.5 s, leads to have the probability of pounding about 41.5%, 18% and 5.8%, respectively. Finally, based on the results, two equations are developed for probabilistic determination of needed structural separation distance.

Probabilistic evaluation of separation distance between two adjacent structures

Mojtaba Naeej,Javad Vaseghi Amiri,Sayyed Ghasem Jalali 국제구조공학회 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.67 No.5

Structural pounding is commonly observed phenomenon during major ground motion, which can cause both structural and architectural damages. To reduce the amount of damage from pounding, the best and effective way is to increase the separation distance. Generally, existing design procedures for determining the separation distance between adjacent buildings subjected to structural pounding are based on approximations of the buildings’ peak relative displacement. These procedures are based on unknown safety levels. The aim of this research is to estimate probabilistic separation distance between adjacent structures by considering the variability in the system and uncertainties in the earthquakes characteristics through comprehensive numerical simulations. A large number of models were generated using a robust Monte-Carlo simulation. In total, 6.54 million time-history analyses were performed over the adopted models using an ensemble of 25 ground motions as seismic input within OpenSees software. The results show that a gap size of 50%, 70% and 100% of the considered design code for the structural periods in the range of 0.1-0.5 s, leads to have the probability of pounding about 41.5%, 18% and 5.8%, respectively. Finally, based on the results, two equations are developed for probabilistic determination of needed structural separation distance.

Effect of rigid connection to an asymmetric building on the random seismic response

Taleshian, Hamed Ahmadi,Roshan, Alireza Mirzagoltabar,Amiri, Javad Vaseghi Techno-Press 2020 Coupled systems mechanics Vol.9 No.2

Connection of adjacent buildings with stiff links is an efficient approach for seismic pounding mitigation. However, use of highly rigid links might alter the torsional response in asymmetric plans and although this was mentioned in the literature, no quantitative study has been done before to investigate the condition numerically. In this paper, the effect of rigid coupling on the elastic lateral-torsional response of two adjacent one-story column-type buildings has been studied by comparison to uncoupled structures. Three cases are considered, including two similar asymmetric structures, two adjacent asymmetric structures with different dynamic properties and a symmetric system adjacent to an adjacent asymmetric one. After an acceptable validation against the actual earthquake, the traditional random vibration method has been utilized for dynamic analysis under Ideal white noise input. Results demonstrate that rigid coupling may increase or decrease the rotational response, depending on eccentricities, torsional-to-lateral stiffness ratios and relative uncoupled lateral stiffness of adjacent buildings. Results are also discussed for the case of using identical cross section for all columns supporting eachplan. In contrast to symmetric systems, base shear increase in the stiffer building may be avoided when the buildings lateral stiffness ratio is less than 2. However, the eccentricity increases the rotation of the plans for high rotational stiffness of the buildings.

Nonlinear Vibration Control of Adjacent Steel MRF Structures Using Non-velocity Dependent Dampers Subjected to Various Seismic Excitations

Mohammad Amin Abbaszadeh,Hamed Hamidi,Hamid Rajabnejad,Seyed Abolfazl Naseri,Javad Vaseghi Amiri 한국강구조학회 2022 International Journal of Steel Structures Vol.22 No.3

Control of adjacent structures during an earthquake is one of the major challenges in engineering practices. Connecting two structures with the use of a damper is considered to be one of the eff ective vibration control and reducing damage approaches. Improving the seismic performance of weak structures by connecting them to substructures is an eff ective method. The type of dampers and the characteristics of input earthquake loading play an important role in the performance of connected buildings. In addition, some previous studies have shown that viscous dampers, besides the problem of sensitivity to temperature and oil leakage, could not be much eff ective against near-fault records. In this study, the vibration control of smaller frequency structures while connected to robust structures with two types of dampers (i.e., friction and yielding) was investigated Three distinctive sets of earthquake records were considered to be the excitation input data. To this end, three 3-, 5-, and 8-story buildings were selected and the eff ects of applying friction and yielding dampers to control their vibration while subjected to the abovementioned records were studied. The results imply that both dampers performed well when subjected to nearfault records; however, the performance varies depending on the type of earthquake. A maximum displacement reduction rate of 64% was observed. Friction and yielding dampers have shown more eff ective performance in the middle and at the top stories, respectively. As the number of stories increased, the eff ectiveness of lower stories dampers to reduce seismic responses decreased, so their application could be neglected.

Prediction of Lateral Confinement Coefficient in Reinforced Concrete Columns using M5’ Machine Learning Method

Mojtaba Naeej,Meysam Bali,Mohamad Reza Naeej,Javad Vaseghi Amiri 대한토목학회 2013 KSCE Journal of Civil Engineering Vol.17 No.7

Predicting the lateral confinement coefficient in reinforced concrete columns is a very important issue in structural engineering. Therefore, several experimental formulas have developed to predict it. Recently, soft computing tools such as artificial neural networks have been used to predict the confinement coefficient. However, these tools are not as transparent as empirical formulas. In this study, another soft computing approach, i.e. model trees have been used for predicting the confinement coefficient. The main advantage of model trees is that, unlike the other data learning tools, they are easier to use and more importantly they represent understandable mathematical rules. In this paper, a new formula that includes some structural parameter is derived using dimensionless parameter for estimating the confinement coefficient. A comparison is made between the estimated confinement coefficient by this new formula and formula given by others researches shows the accuracy of prediction.