Volume 3, Number 1, January 2012
An empirical predictive relationship correlating bracketed duration to earthquake magnitude, site-to-source distance, and local site conditions (i.e. rock vs. stiff soil) for stable continental regions of North America is presented herein. The correlation was developed from data from 620 horizontal motions for central and eastern North America (CENA), consisting of 28 recorded motions and 592 scaled
motions. The bracketed duration data was comprised of nonzero and zero durations. The non-linear mixed-effects regression technique was used to fit a predictive model to the nonzero duration data. To account for the zero duration data, logistic regression was conducted to model the probability of zero duration occurrences. Then, the probability models were applied as weighting functions to the NLME regression results. Comparing the bracketed durations for CENA motions with those from active shallow
crustal regions (e.g. western North America: WNA), the motions in CENA have longer bracketed durations than those in the WNA. Especially for larger magnitudes at far distances, the bracketed durations in CENA tend to be significantly longer than those in WNA.
bracketed duration; central/eastern North America ground motions; ground motion attenuation; ground motion predictive relationships; stable continental region ground motions; strong ground motion durations
Jongwon Lee: Paul C. Rizzo Associates, Inc., Pittsburgh, PA, USA
Russell A. Green: Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA, USA
Simplified equations for fundamental period of vibration of skeletal structures provided by most seismic design provisions suffer from the absence of any associated confidence levels and of any reference to their empirical basis. Therefore, such equations may typically give a sector of designers the false impression of yielding a fairly accurate value of the period of vibration. This paper, although not addressing simplified codes equations, introduces a set of mathematical equations utilizing the theory of error propagation and First-Order Second-Moment (FOSM) techniques to determine bounds on the relative
error in theoretically calculated fundamental period of vibration of skeletal structures. In a complementary
step, and for verification purposes, Monte Carlo simulation technique has been also applied. The latter, despite involving larger computational effort, is expected to provide more precise estimates than FOSM methods. Studies of parametric uncertainties applied to reinforced concrete frame bents – potentially idealized as SDOF systems – are conducted demonstrating the effect of randomness and uncertainty of various relevant properties, shaping both mass and stiffness, on the variance (i.e. relative error) in the estimated period of vibration. Correlation between mass and stiffness parameters – regarded as random variables – is also thoroughly discussed. According to achieved results, a relative error in the period of
vibration in the order of 19% for new designs/constructions and of about 25% for existing structures for assessment purposes – and even climbing up to about 36% in some special applications and/or circumstances – is acknowledged when adopting estimates gathered from the literature for relative errors in the relevant random input variables.
period of vibration; mass; stiffness; error propagation; monte carlo simulation
Sameh S.F. Mehanny: Structural Engineering Department, Cairo University, Dar Al-Handasah (Shair and Partners), Cairo, Egypt
The behavior of beam-column joints in moment resisting frame structures is susceptible to damage caused by seismic effects due to poor performance of the joints. A good number of researches were carried out to understand the complex mechanism of RC joints considered in current seismic design codes. The traditional construction detailing of transverse reinforcement has resulted in serious joint failures during earthquakes. This paper introduces a new design philosophy involving the use of additional diagonal bars within the joint particularly suitable for low to medium seismic effects in earthquake zones. In this study, ten full-scale interior beam-column specimens were constructed with various additional
reinforcement details and configurations. The results of the experiment showed that adding additional bars is a promising approach in reinforced concrete structures where earthquakes are eminent. In terms of overall cracking observation during the test, the specimens with additional bars (diagonal and straight) compared with the ones without them showed fewer cracks in the column. Furthermore, concrete confinement is certainly an important design measure as recommended by most international codes.
reversed cyclic loading; beam-column joint; plastic hinge; additional diagonal bars; displacement ductility; column shear force; crack propagation
Xilin Lu: State Key Laboratory of Disaster Reduction in Civil Engineering, Tongji University, Shanghai, China
Tonny H. Urukap, Sen Li and Fangshu Lin: College of Civil Engineering, Tongji University, Shanghai, China
Ductility inverse-mapping method for SDOF systems including passive dampers for varying input level of ground motion
Hyeong-Gook Kim, Shinta Yoshitomi, Masaaki Tsuji and Izuru Takewaki
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A ductility inverse-mapping method for SDOF systems including passive dampers is proposed which enables one to find the maximum acceleration of ground motion for the prescribed maximum response deformation. In the conventional capacity spectrum method, the maximum response deformation is computed through iterative procedures for the prescribed maximum acceleration of ground motion. This
is because the equivalent linear model for response evaluation is described in terms of unknown maximum deformation. While successive calculations are needed, no numerically unstable iterative procedure is required in the proposed method. This ductility inverse-mapping method is applied to an SDOF model of bilinear hysteresis. The SDOF models without and with passive dampers (viscous, viscoelastic and hysteretic dampers) are taken into account to investigate the effectiveness of passive dampers
for seismic retrofitting of building structures. Since the maximum response deformation is the principal parameter and specified sequentially, the proposed ductility inverse-mapping method is suitable for the implementation of the performance-based design.
capacity spectrum method; maximum ground acceleration; response spectrum; passive dampers; ductility inverse-mapping method; demand and capacity spectra; equivalent linear model; performance- based design
Hyeong-Gook Kim, Shinta Yoshitomi, Masaaki Tsuji and Izuru Takewaki: Department of Architecture & Architectural Engineering, Kyoto University, Kyotodaigaku-katsura, Kyoto 615-8540, Japan
Seismic damage and vulnerability of five historical masonry structures surveyed after the 1999 Kocaeli and Duzce, Turkey earthquakes are discussed in this paper. The structures are located in two neighboring cities that have been struck by five very large (Ms
seismic damage; historical Turkish mosques; masonry; deterioration; earthquake
Adem Dogangun: Department of Civil Engineering, Uludag University, Bursa, Turkey
Halil Sezen: Civil and Environmental Engineering and Geodetic Science, The Ohio State University, Ohio, USA