International Journal of Earthquake and Impact Engineering (5 papers in press)
Comparative Study on Damping Models of Linear System Subjected to Arbitrary Dynamic Loading
by Tushar H. Bhoraniya, Sharadkumar P. Purohit
Abstract: Linear and non-linear damping models, correlated through equivalent damping coefficient, have been developed for discrete vibrating system employing energy equivalence principle at steady state response of the system. Application of, so developed, damping models to derive response of discrete vibrating system subjected to arbitrary dynamic loading is not obvious due to transient nature of the system. Thus, equivalent damping coefficient of damping models needs to be redefined to derive realistic transient response of the system. In the present study, First Cycle Damping Coefficient (FCDC) approach is proposed that uses the first cycle transient response of the system to derive equivalent damping coefficient for linear and non-linear damping models through Genetic Algorithm propelled energy equivalence with that of linear viscous damping model. A Single Degree of Freedom (SDOF) system with linear and non-linear damping models subjected to arbitrary dynamic loading are solved. Efficacy of proposed FCDC approach is established through experimental study on lightly damped single storey building model. Velocity squared damping model yields higher peak displacement response for the system vis-
Keywords: SDOF System; Damping Models; Equivalent Viscous Damping Coefficient; Energy per cycle; Arbitrary Dynamic Loading.
Seismic design and assessment of steel frames with visco-plastic dampers
by Jaehoon Bae, Theodore L. Karavasilis
Abstract: This paper evaluates the seismic performance of steel frames with visco-plastic dampers. The visco-plastic damper is realized by the in-series combination of a viscoelastic damper and a friction device. Its main goal is the reduction of storey drifts without significantly increasing the base shear force. A prototype steel building is designed as a high ductility steel moment-resisting frame (MRF). The MRF is then equipped with viscoelastic or visco-plastic dampers to achieve high seismic performance. Parametric designs of visco-plastic dampers with different activation forces for their friction devices are carried out. Non-linear dynamic analyses for a set of 20 earthquake ground motions scaled to the design and maximum considered earthquake intensities are carried out in OpenSees. Moreover, incremental dynamic analyses up to collapse are conducted. The response results highlight the effectiveness of the visco-plastic damper to control drifts, residual drifts, and the base shear force, while also providing an adequate seismic collapse resistance.
Keywords: Visco-plastic damper; Steel MRF; Seismic design; Resilience; Eurocode 8.
Critical Response Evaluation of Damped Bilinear Hysteretic SDOF Model under Long Duration Ground Motion Simulated by Multi Impulse Motion
by Hiroki Akehashi, Kotaro Kojima, Ehsan Noroozinejad Farsangi, Izuru Takewaki
Abstract: Multi impulse is used as a representative of a series of many-cycle harmonic waves which substantially simulate the long-duration earthquake event. An analytical formulation is developed for the elastic-plastic response of a single-degree-of-freedom (SDOF) damped structure with bilinear hysteresis under the critical multi impulse condition. Following the procedure for elastic-perfectly plastic models, a novel procedure using an energy balance law is introduced. In this procedure, under the multi impulse condition, only the free-vibration exists, hence the energy balance law can be applied easily. An approximate but effective treatment of the energy dissipated by the viscous damping is a new perspective. It is shown that based on an analytical solution, the critical maximum plastic deformation and the corresponding critical impulse timing can be determined in the steady state condition depending on the input values. To investigate the reliability and accuracy of the proposed approach, a comparison is made with the response analysis outcome to the corresponding sine wave as a representative of the long-duration earthquake ground motion (GM).
Keywords: Seismic response; Critical excitation; Critical response; Bilinear hysteresis; Viscous damping; Long-duration GM; Resonance; Multi impulse.
Zero Earthquake-Damage Buildings: the Challenge for Sustainability and Resilience in Seismic Areas
by Paolo Clemente, Giovanni Bongiovanni, Giacomo Buffarini, Fernando Saitta
Abstract: In the past earthquakes destroyed entire civilizations; today they can also cause huge economic and environmental damage, as demonstrated by the recent seismic events. It is essential to know the territory for careful choosing the sites for new residential and industrial developments, but also to know the existing buildings in order to plan the necessary measures and establish the right priorities, taking into account the sustainability and resilience requirements. Analysis and interventions, in fact, cannot ignore the need of not turning mortgage that our children are not able to pay off by either that to obtain a significant reduction of the damage is also essential to increase the ability to recover quickly after a disaster. Designing Zero Earthquake-Damage Buildings is certainly the best solution both for sustainability and resilience.
Keywords: sustainability; resilience; seismic actions; structural behavior; Zero Earthquake-Damage Buildings.
Analysis of Essential facilities and Occupancy Class for Earthquake Preparedness in Dhaka City
by Md. Sohel Ahmed
Abstract: A major earthquake has been forecast for Bangladesh in the near future due to its position at the junction of three continental plates. Should an earthquake occur, it is expected to be devastating, particularly in the capital city of Dhaka, due to a large number of high-rise buildings constructed on relatively unstable ground and the high population density of the metropolitan area. Of primary concern is the fact that such a massive earthquake would be very difficult for the government and non-governmental organizations to handle, due to the low quality of local infrastructure. In this paper, we use Statistical methods to identify correlations among the Occupancy classes, Essential facilities, and Population density in both of Dhaka North City Corporation (DNCC) and Dhaka South City Corporation(DSCC). Correlation analysis shows that Medical care and Emergency response are positively weak correlated in DNCC but negatively correlated in the Residential areas in DSCC. Multiple regression analysis indicates that the potential to efficiently respond to a disaster is relatively low concerning the Emergency response and Medical care facilities in both of DNCC and DSCC area. The findings reveal that Essential facilities in DSCC are fewer than those of DNCC and it is necessary to set up more essential facilities both in areas, particularly in DSCC area.
Keywords: Earthquake; Disaster management; Emergency response; Correlation analysis; Regression analysis.