عنوان مقاله [English]
In this study, the relationship between different definitions of duration with peak ground acceleration, focal depth, and soil conditions of the site using accelerometer records in Iran was calculated and presented. Then, 1054 three-component records of 197 seismic events recorded with a moment magnitude greater than or equal to 5.0 were used. All data for this study were obtained from the Road, Housing, and Urban Development Research Center (BHRC) in Iran. All records were for sites with focal depths and shear wave velocities within the first 30 m of depth. After preparing the records, the baseline correction was performed on them using Fortran programming and durations with g0.05 acceleration thresholds, uniform durations with g0.05 acceleration thresholds, significant durations 5-95% were calculated. Then, according to the Iranian 2800 earthquake code, soil type was grouped and the data were classified into three categories according to soil type. The data with soil group 4 were very low and unreliable. The results showed that with increasing peak ground acceleration, bracketed and uniform duration increased, while for significant durations, records with high significant durations generally have minor peak acceleration. Mathematical relationships were also shown for variations in any durations with peak ground acceleration and focal depth and soil type variations. Also, with softer soil, the slope of the bracketed and uniform duration relationship with PGA increased. Increasing the focal depth decreased the durability with different definitions. After a focal depth of 20 km, a threshold of 0.05g is usually less than 10 seconds. The relationship between shear wave velocity at 30 m depth and significant duration indicated that with increasing shear wave velocity, significant duration decreased. The relationship between the duration and maximum amplitude of earthquake ground motions was important for the seismic design of structures, especially reinforced concrete structures, which suffered from stiffness and reduced strength in successive earthquake cycles.