- مبلغ: ۸۶,۰۰۰ تومان
- مبلغ: ۹۱,۰۰۰ تومان
Determination of appropriate seismic demand is important for deriving reliable seismic forces for use in structural design and vulnerability assessment. Demand can be defined by either probabilistic or deterministic approaches depending on the use of the assessment. The use of probabilistic or deterministic approaches depends on the level of the assessment since deterministic can mostly be used for single structures whereas probabilistic for city or country level assessment. This paper presents demand characterization which is based on results of existing seismic hazard studies and local tectonic features around Islamabad–Rawalpindi region (study region) in Pakistan. Existing seismic zoning maps and recent probabilistic seismic hazard studies are reviewed, and the findings are used to quantify and compare the demand for a typical low-rise reinforced concrete building. As another option, deterministic demand is defined through spectra using suitable attenuation relationship which is assessed and validated using the Kashmir earthquake and other similar earthquakes data. Deterministic spectra for study region are generated by considering the critical local tectonic features. Federal Emergency Management Agency (FEMA 356) approach is used for smoothening of deterministic spectra, and the new spectral corner periods are calculated.
PSC-86 has the oldest seismic zoning map for Pakistan, and the provisions of this code can be used for calculating seismic design forces of existing engineered structures in building stock with basic seismic design considerations. This design category of RC structures must be considered for vulnerability assessment. In comparison with the latest BCP (2007) seismic zoning map, PSC-86 suggests very low seismic hazard for the study area and the Kashmir earthquake affected areas. The demand comparison shows that the existing building stock of study area is highly vulnerable.
Recent PSHA studies show significant variability in predicted PGA values for 500-year return period. For the study area, PMD-NORSAR  predicts the largest PGA value of 0.37 g. Hence, the seismic forces (V/W) according to PMDNORSAR  for the ductile and non-ductile four-storey RC structure are found to be significantly higher as compared to the seismic forces evaluated from PSC-86 spectrum. However, BCP  hazard value is commonly used these days for the seismic forces calculation of modern RC structures of the study area. Monalisa et al.  predicted the least PGA values of 0.15 g for the study area. The variability in probabilistic hazard predictions may be used in propagating the demand uncertainty in vulnerability assessment of building stock of study area.