A Numerical Study on Comparison of 1D and 2D Seismic Responses of a Basin in Turkey
Murat Emre Hasal,
Recep Iyisan
Issue:
Volume 2, Issue 5, September 2014
Pages:
123-133
Received:
16 September 2014
Accepted:
5 October 2014
Published:
20 October 2014
Abstract: Local site conditions such as seismic bedrock depth, bedrock slope of the edge, geometry and characteristics of soil layers, topographical irregularities, etc. are the most important factors affecting earthquake ground motion in a specific site. The amplitude and frequency content of bedrock motion can be changed by local site effects, and this variation is denoted as an amplification or de-amplification. Among the several factors, basin edge effect plays an important role in the transformation of earthquake waves and increase of the surface motion duration and amplitude. The limited width of the soil layers or the edge geometry at the deep formations cause earthquake wave transformations, thus the amplitude of the surface ground motion may vary depending on its location. For this reason the frequency content of surface ground motion may differ from the calculated surface ground motion by one dimensional dynamic analysis. In this case two dimensional analysis is required. In this study, in order to compare the soil response under different strong ground motion, one and two dimensional dynamic analyses were performed by using the Dinar Basin model in Turkey. The acceleration time histories and absolute acceleration spectra were obtained for pre-selected points on the ground surface. The 2D/1D spectral acceleration ratios were calculated by dividing the absolute acceleration spectra obtained from two dimensional (2D) and one dimensional (1D) dynamic analysis. The variations of the spectral acceleration ratios (2D/1D) with distance from basin edge were evaluated for different period values. The calculated 2D/1D spectral acceleration ratios reached their maximum values at a certain zone (X/D<3) near basin edge for every interested period value. While approaching to center of basin models, especially at the zones after X/D=3 point it can be noticed that 2D/1D spectral acceleration ratios generally converged to 1 regardless of the edge bedrock slope values. The highest average spectral acceleration ratios were calculated when the relevant period values were between T=0.2~0.5 s. They took values varying between 2 and 3 for this period interval. A relationship between the results of 1D and 2D dynamic analyses was established. In addition, the approximate validity range of 1D and 2D dynamic analysis at the basin edges was investigated for the model.
Abstract: Local site conditions such as seismic bedrock depth, bedrock slope of the edge, geometry and characteristics of soil layers, topographical irregularities, etc. are the most important factors affecting earthquake ground motion in a specific site. The amplitude and frequency content of bedrock motion can be changed by local site effects, and this var...
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Strength Characteristics of Hand-Quarried Partially-Weathered Quartzite Aggregates in Concrete
Mark Adom-Asamoah,
Yaw A. Tuffour,
Russell O. Afrifa,
Charles K. Kankam
Issue:
Volume 2, Issue 5, September 2014
Pages:
134-142
Received:
11 November 2014
Accepted:
18 November 2014
Published:
27 November 2014
Abstract: The use of hand-quarried weathered quartzitic aggregates as the coarse component of concrete was investigated. Samples of hand-quarried quartzite aggregates exhibiting different degrees of weathering were evaluated in quality and their suitability as coarse component of concrete. The 7, 14, 28 and 56 day compressive strengths were obtained from 100mm concrete cube samples prepared with the weathered aggregates in 1:1:2, 1:1.5:3, 1:2:4 and 1:3:6 concrete mixes and different water: cement ratios 0.45, 0.5 and 0.6. Modulus of rupture beams were tested aged 28-days. Control samples were also tested for compressive and tensile strengths using sound granite aggregates obtained from a commercial quarry. The quality tests showed very little difference between the un-weathered quartzite aggregates and the sound granite aggregates. The weathered quartzite aggregates except the highly weathered grade were found to have properties that met specification requirements for concrete. However, the partially weathered aggregates were marginal in quality and had high water absorption values. The 28-day compressive strength of the partially weathered quartzite concrete averaged 86% of the granite. It is concluded that except when the degree of weathering is very high, the partially weathered quartzite stone could be used as coarse aggregates in concrete that would be subjected to low stresses.
Abstract: The use of hand-quarried weathered quartzitic aggregates as the coarse component of concrete was investigated. Samples of hand-quarried quartzite aggregates exhibiting different degrees of weathering were evaluated in quality and their suitability as coarse component of concrete. The 7, 14, 28 and 56 day compressive strengths were obtained from 100...
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