• Structural Engineering and Mechanics
• /
• v.73 no.3
• /
• pp.303-317
• /
• 2020

In this study an innovative rocking zipper braced frame (RZBF) is proposed to overcome the deficiencies of common concentrically braced frames. RZBF is an improved rocking concentrically braced frame which is based on combination of rocking behavior and zipper columns. The base rocking joints and post-tensioned bars provide rocking response and restoring force, respectively. Also, zipper columns distribute the unbalance force over the frame height and reduce the damage concentration. To evaluate seismic performance of RZBF, a comparison study is carried out considering concentrically braced frame, zipper braced frame, rocking concentrically braced frame and RZBF. Thereby, a suite of non-linear time history analyses had been performed on four different types of archetypes with four, six, eight, ten and twelve stories. Frames were designed and non-linear time history analyses were conducted in OpenSees. To compare the seismic behavior of the archetypes, roof drifts, residual roof drifts, story drifts, the forces of first and top story braces, PT bars forces, column uplift and base shears were taken in to consideration. Results illustrate that using RZBF, can reduce the damage due to reduced residual drifts. Zipper columns enhance the seismic performance of rocking systems. As the number of stories increase in the RZBF systems, larger top story braces were needed. So the RZBF system is applicable on low and midrise buildings.

• Computers and Concrete
• /
• v.19 no.6
• /
• pp.689-699
• /
• 2017

An energy-based approach for determining earthquake safety of reinforced concrete frame structures is presented. The developed approach is based on comparison of plastic energy capacities of the structures with plastic energy demands obtained for selected earthquake records. Plastic energy capacities of the selected reinforced concrete frames are determined graphically by analyzing plastic hinge regions with the developed equations. Seven earthquake records are chosen to perform the nonlinear time history analyses. Earthquake plastic energy demands are determined from nonlinear time history analyses and hysteretic behavior of earthquakes is converted to monotonic behavior by using nonlinear moment-rotation relations of plastic hinges and plastic axial deformations in columns. Earthquake safety of selected reinforced concrete frames is assessed by using plastic energy capacity graphs and earthquake plastic energy demands. The plastic energy dissipation capacities of the frame structures are examined whether these capacities can withstand the plastic energy demands for selected earthquakes or not. The displacements correspond to the mean plastic energy demands are obtained quite close to the displacements determined by using the procedures given in different seismic design codes.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2006.04a
• /
• pp.1025-1032
• /
• 2006

The PVRC(Pressure Vessel Research Council) damping is for the response spectrum analysis of the piping system. In this study, the possibility to apply it to the time history analysis is evaluated to reduce the higher conservatism for the structural integrity. The evaluation was performed for the surge line connecting the pressurizer to the hot-leg, and the whole mode includes the RCS and the building structures with the surge line. The analyses were performed using ANSYS code. The first modal analysis shows the modes of the surge line are isolated from those of the other structures. The composite modal damping was calculated with PVRC damping for the surge line and RG 1.60 damping for the other structures by using ANSYS routines. Of the calculated composite modal damping values, the composite modal damping values related to the modes of the surge line were replaced with the PVRC damping values with respect to its frequencies. With this replacement, the composite modal damping values of the other structures were not changed. Based on this decouple characteristics, the time history analyses for the seismic events with PVRC damping for the surge line were performed. And the results show the resultant loads can be reduced by up to 50%.

• Earthquakes and Structures
• /
• v.15 no.6
• /
• pp.605-616
• /
• 2018

In this paper, an extended Cloud analysis method is developed for seismic fragility assessment of existing highway bridges in the southeast Queensland region. This method extends the original Cloud analysis dataset by performing scaled Cloud analyses. The original and scaled Cloud datasets are then paired to generate seismic fragility curves. The seismic hazard in this region is critically reviewed, and the ground motion records are selected for the time-history analysis based on various record selection criteria. A parametric highway bridge model is developed in the OpenSees analysis software, and a sampling technique is employed to quantify the uncertainties of highway bridges ubiquitous in this region. Technical recommendations are also given for the seismic performance evaluation of highway bridges in such low-to-moderate seismic zones. Finally, a probabilistic fragility study is conducted by performing a total of 8000 time-history analyses and representative bridge fragility curves are generated. It is illustrated that the seismic fragility curves generated by the proposed extended Cloud analysis method are in close agreement with those which are obtained by the rigorous incremental dynamic analysis method. Also, it reveals that more than 50% of highway bridges existing in southeast Queensland will be damaged subject to a peak ground acceleration of 0.14 g.

• Proceedings of the Earthquake Engineering Society of Korea Conference
• /
• 2005.03a
• /
• pp.277-283
• /
• 2005

Inelastic model of Second Jindo Bridge is investigated to perform nonlinear dynamic analyses with various earthquake ground motions. The modal analysis is performed to obtain dynamic characteristics of the bridge and verify the model. It proves that the model has an appropriate dynamic characteristic and its natural frequency is relatively low. Four ground motions are chosen for time history dynamic analyses; El Centro, Kobe, Taft, and Mexico earthquake. Each ground motion multiplied by specified factors to investigate damages of the structure. The analyses prove that responses of the bridge depend on the duration time and the frequency characteristics of ground motion, not only peak acceleration. Static push-over analysis of steel pylon shows that the dynamic analysis over-estimates the seismic behavior of steel pylon definitely. Nonlinear spring hinge model is suggest to improve the shortage of the inelastic model could not deliberate local buckling damage. According to the time history analysis of nonlinear spring hinge model, it is proved that the inelastic beam element analysis overestimate the seismic capacity of steel pylon unquestionably with a large amount of errors.

• Structural Engineering and Mechanics
• /
• v.44 no.3
• /
• pp.379-403
• /
• 2012

In recent years, the need for optimal design of structures under time-history loading aroused great attention in researchers. The main problem in this field is the extremely high computational demand of time-history analyses, which may convert the solution algorithm to an illogical one. In this paper, a new framework is developed to solve the size optimization problem of steel truss structures subjected to ground motions. In order to solve this problem, the covariance matrix adaptation evolution strategy algorithm is employed for the optimization procedure, while a generalized regression neural network is utilized as a meta-model for fitness approximation. Moreover, the computational cost of time-history analysis is decreased through a wavelet analysis. Capability and efficiency of the proposed framework is investigated via two design examples, comprising of a tower truss and a footbridge truss.

• Steel and Composite Structures
• /
• v.2 no.2
• /
• pp.113-128
• /
• 2002

The performance of steel MRF with rigid connections, proportioned by adopting different capacity design criteria, is evaluated in order to highlight the effectiveness of static non-linear procedure in predicting the structural seismic behavior. In the framework of the performance-based design, some considerations are made on the basis of the results obtained by both dynamic time histories and push-over analyses, particularly with reference to the damage level and the structure ability to withstand a strong earthquake.

• International Journal of Railway
• /
• v.3 no.2
• /
• pp.73-82
• /
• 2010

Global and local behaviors of a lightly RC shear walls are investigated in this paper. For the sake of cyclic behaviors, nominal ground accelerations of 0.15 g, 0.40 g and 0.55 g which associated with natural periods of the walls are applied as listed in French CAMUS-2000 shake table test. Modified Kent & Park model, Drucker-Prager model for concrete material and $Giufr\acute{e}$-Menegotto-Pinto model for rebar are used for time history analyses using fiber/solids elements respectively. Alternatively, Eulerian beam analysis are discussed by imposing inelastic hinges at the most possible plastic hinge location using modified Takeda's trilinear model with stiffness reduction. Relative displacements, base shears, bending moments of 5-story shear building with 36-tons of mass under bi-lateral seismic excitation are extracted and compared with EC-8, PS-92 and KBC-09 provisions. Multi-scaled degradation process; material damage, elemental fracture and structural failure in turn is discussed in the view of numerical accuracy, efficiency and limitation depending on three different model-based analyses.

• Computers and Concrete
• /
• v.30 no.2
• /
• pp.113-126
• /
• 2022

Reinforced concrete bearing walls (RCBWs) are one of the most applicable structural systems. Therefore, vulnerability analysis and rehabilitation of the RCBW system are of great importance. In the present study, in order to the more precise investigation of the performance of this structural resistant system, pushover and nonlinear time history analyses based on several assumptions drawing upon experimental research were performed on several models with different stories. To validate the nonlinear analysis method, the analytical and experimental results are compared. Vulnerability evaluation was carried out on two seismic hazard levels and three performance levels. Eventually, the need for seismic rehabilitation with the basic safety objective (BSO) was investigated. The obtained results showed that the studied structures satisfied the BSO of the seismic rehabilitation guidelines. Consequently, according to the results of analyses and the desired performance, this structural system, despite its high structural weight and rigid connections and low flexibility, has integrated performance, and it can be a good option for earthquake-resistant constructions.

• Earthquakes and Structures
• /
• v.22 no.3
• /
• pp.289-304
• /
• 2022

During strong ground motions, adjacent structures with insufficient separation distances collide with each other causing considerable architectural and structural damage or collapse of the whole structure. 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. This paper attempts to evaluate the influence of foundation flexibility on the structural seismic response by considering the variability in the system and uncertainties in the ground motion characteristics through comprehensive numerical simulations. Actually, the aim of this study is to evaluate the influence of foundation flexibility on probabilistic evaluation of structural pounding. A Hertz-damp pounding force model has been considered in order to effectively capture impact forces during collisions. In total, 5.25 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 of the study indicate that the soil-structure interaction significantly influences the pounding-involved responses of adjacent structures during earthquakes and generally increases the pounding probability.