Journal of Seismology and Earthquake Engineering
Volume:13 Issue: 1, Spring 2011

The performance-based earthquake engineering requires reliable assessment of long-period ground motion particularly for tall buildings, base-isolated structures, long bridges, and structures that are designed to deform beyond the elastic range. The important issues involved in such assessments are: Empirical and theoretical tools for prediction of displacement response spectra; Analysis and incorporation ofnear fault effects; Spectrumscaling for different damping ratios and; Time domain simulation of long-period ground motion. These issues are elaborated through (1) the principles for modification of design basis spectra in the long-period range; (2) guidelines for time domain simulation of long-period ground motions; and (3) rules for selecting and scaling ground motion records to address long-period effects. This paper aims to review and discuss these issues with developments on GMPRs for peak ground displacement and 10s spectral acceleration, and example applications on earthquake hazard assessment for 10s spectral accelerations and its deaggregation in the Marmara Region, Turkey.

The North Tehran Fault is located at the southernmost piedmont of Central Alborz, north of Iran. It stands out as a major active fault menacing directly the city of Tehran, a 12 million people metropolis, and would have been the source of several major historical earthquakes in the past. The fault zone extends up to 110km and corresponds mainly to a reverse fault mostly crossing the northern suburbs of the Tehran metropolis, although NTF in its eastern part is characterized more as a left lateral strike slip active fault. We carried out a paleoseismological study of the fault zone in order to determine whether the fault was activated during the Holocene, and to define the characteristics of its activity in terms of kinematics and magnitude. Here in this paper we present only a part of our paleoseismological investigations trench TE2. Observations fromtwo trenches dug across the North Tehran fault scarp reveal evidence for a maximum of six surface-rupturing events within the late quaternary. According to the empirical relationships among average displacement per event and Moment magnitude [25], we can estimate six events Mw~ 6.5 associated with these ruptures in TE2 trench.

Based on Housner's assumption, the average input energy from earthquakes to a building modeled as a single degree of freedom (SDOF) system, is related mainly to total mass of the building. Thus, based on the above premise for low damping and relatively long period systems, the seismic input energy per unit mass of the system(SDOF or MDOF) ismainly related to the ground motion features. The present study attempts to analytically reveal the range of validity of these assumptions in linear systems and to find an optimal stiffness distribution over the height of high-rise shear linear buildings to minimize the seismic input energy. To accomplish this objective, it is shown from the spectral standpoint that input energy spectra generally is a function of the natural period of vibration, so the input energy is further related to the stiffness of structure, the mass, damping ratio and ground motion characteristics. Subsequently, it is demonstrated that for low to moderate height (up to 20 stories) shear type structures, the optimal distribution of stiffness obeys a parabolic form, while for taller structures, this formis a bell-shaped function.

Shear walls are among the most common lateral load resisting systems, which are not recognized as efficient ductile structural components. Using any opening in the wall leads to disperse the inelastic behavior across the height of the wall and employ both flexural and shear ductility capacity of the system at the base and around the openings, respectively. Simple models were utilized to study the role of large openings in inelastic dynamic behavior of shear walls. Despite the constant total input energy, the amount of dissipated energy at the lower part of these walls is decreased to about two-third the value of ordinary shear walls. Consequently, the ductility demand diminished in the plastic hinge at the base and the required reinforcement detailing becomes simpler. However, marginal gains observed in the structural response such as base shear, base moment, inter-story drift and story displacement. Furthermore, to obtain the crack patterns and the ductility of the walls, static inelastic analyses were carried out using accurate finite element models. The results reveal that despite a small reduction in the strength of shear walls with openings, the crack patterns distribute more uniformly, and the ductility increases as the opening becomes larger

This paper describes the impact of the 4th September 2010 and the 22nd February 2011 Canterbury earthquakes on masonry buildings. Christchurch and the surrounding areas have more than a thousand old buildings built of unreinforced brick and stone masonry. Several unreinforced masonry (URM) buildings were damaged (some very severely) in the September earthquake; whereas the February earthquake caused severe damage (many collapsed) to most URM buildings in Christchurch; requiring them to be demolished. As expected, retrofitted URM buildings generally performed better, but in the February earthquake several retrofitted buildings were also severely damaged. URM buildings with perimeter walls partially anchored using small and sporadic anchor bolts not extending to the full perimeter and height of the walls suffered severe damage. On the other hand, URMbuildings that were systematically retrofitted to avoid the perimeter walls from detaching fromeach other and fromthe floor and roof sustained the severe shakings of the February earthquake with only minor damage.