| PaperNO | Paper / Abstract |
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F1-011
10:50
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11:05
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DEPTH-DEPENDENT AMPLIFICATION BEHAVIOR OBSERVED FROM DOWNHOLE ARRAYS IN THE TAIPEI BASIN
During the 1999 Chi-Chi earthquake, the Taipei basin far from the epicenter also encountered severe damages owing to the local site effect and the amplification of ground motion. Therefore, this study aims to characterize the amplification behavior and focus on its correlation with the depth of bedrock. Seven downhole arrays installed at different locations within the Taipei basin (i.e. various depths of bedrock) are adopted for the analysis. The amplification factors at the short period (0.2s) and long period (1.0s) are first derived based on the surface and downhole measurements. Then, the depth correction factor (DCF) accounting for the depth effect is derived given a reference depth of bedrock. The obtained amplification factors for both short and long periods are higher than the NEHRP one, especially for the site with deep bedrock. In addition, the obtained DCF is generally consistent with the DCF in the NGA-WEST2 models.
Wan-Chi Lin, Chi-Chin Tsai
Amplification factor, basin, depth correction factor, depth of bedrock, downhole arrays
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F1-012
11:05
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11:20
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NUMERICAL STUDY OF GROUND RESPONSE FOR SITES WITH INCLINED LAYERS
In engineering practice, impact of geologic sediment on earthquake ground motion is often evaluated using one-dimensional (1D) ground response modeling scheme. However, when the geometry of the subsurface geologic structure is complex (e.g. inclined sediment layer), the ground response as predicted from conventional 1D analyses may not be able to capture the multi-dimensional site effect. In this study, a series of two-dimensional (2D) numerical simulations are performed to evaluate the ground response of “basin-type” geologic structures. Effects of impedance contrast and half-space condition on the ground response are explored. The prediction results are also compared to those obtained from conventional 1D modeling.
ON LEI ANNIE KWOK, Zhi-Rong Yang, Chun-Chieh Yao
ground response, inclined layer, site effect
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F1-014
11:20
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11:35
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SOIL DYNAMIC RESPONSE FOR SEISMIC MICROZONATION PURPOSES: RANCAGUA-MACHALI AND RENGO CITIES, CHILE.
Seismic microzonation maps for Rancagua, Machalí, and Rengo, all located in Cachapoal basin, Central Chile (Lat. between -34.00º and -34.50º), were generated based on near-surface geology, well stratigraphy information, and soil dynamical properties. In the past, the stated urban areas have suffered severe damage due to earthquakes occurrence (eg. M 8.0 Algarrobo 1985 earthquake scaled with MSK intensities of VII (Rancagua-Machalí) and VII-VIII (Rengo)). Rancagua lies adjacent to Machalí and both cover an area of approximately 120 km2. Rengo is located to the south with an extension of 50 km2. Cachapoal basin lies between two mountain chains (Andes and Coastal Cordillera), both linked to tectonic movements and mountain built from the subduction of Nazca plate beneath the South American plate. Basin sedimentology predominantly consists of alluvial deposits, mainly sand and gravel with patchy fine-grained sediments. At the foothills, of the Machalí urban area, volcanic ash deposits (Pudahuel Ignimbrite) crop out. A total of approximately 50 microtremor measurements at Rancagua-Machalí and 22 at Rengo were used to compute the predominant frequency f0 using horizontal to vertical spectral ration (HVSR), spatial auto correlation and F-K techniques were used to obtain Vs30 velocity profiles (average shear wave velocities). At the three localities, a triplet of maps was generated: a) HVSR vs frequency; b) Vs30 and c) microzonation maps. Results correlate well with near-surface geology; we defined 3 different types of soil, type A can be associated with the presence of volcanic ash deposits; type B a transitional zone, and type C that can be linked with fluvial deposits mainly gravel and dense sand deposits. Vs30 map of Rengo shows an interesting pattern which decreases from east to west, which could be related to the presence of more fine sediments at the west of the area although no changes of near surface geology are observed. Available maps are key products for seismic risk assessment and urban planning.
Laura Piñero-Feliciangeli, Pablo González- Mondaca, Felipe Leyton, Sergio A. Sepulveda
Chile, Earthquake Engineering, Microzonation, soil dynamic properties
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F4-011
11:35
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11:50
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Seismic Performance Assessment for Gravity Wharves – A Case Study of 2018 Hualien Earthquake
In this paper, procedure of seismic performance assessment for gravity wharves based on time-domain dynamic finite element analysis was proposed. Firstly, quantitative criteria for damage level differentiation were established according to case and literature review. Then, the finite element modeling of the gravity-wall-soil system for seismic response analysis was suggested, in which the soil plasticity as well as the excess pore pressure generation and corresponding soil degradation were considered to simulate the nonlinearity and liquefaction of soil. Thus, the seismic performance of a gravity wharf can be assessed by comparing the analyzed response and the damage criteria. Furthermore, a case study of the gravity wharf damage in the Port of Hualien during the 2018 ML 6.2 Hualien Earthquake was performed for the verification of the proposed procedure, demonstrating its applicability to reasonably evaluate the seismic performance of gravity wharves.
Yung-Yen Ko, Ho-Hsiung Yang, Chi-Wen Hu
finite element analysis, gravity wharf, seismic performance, Soil Liquefaction
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F1-018
11:50
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12:05
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COMPARISON OF DEEPSOIL AND LS-DYNA METHODS IN SITE RESPONSE ANALYSIS FOR NUCLEAR POWER PLANT
Considering the safety of nuclear power plant during the earthquake events is an important issue around the world. A lot of studies were focus on how to estimate the soil dynamic behavior and using numerical methods to simulate the site response. The software DEEPSOIL is current used to calculate the site response with one-dimensional soil column which involves the equivalent linear site response in frequency domain and nonlinear site response in time domain. However, the site response analysis is a nonlinear three-dimensional wave propagation phenomenon during an earthquake motion. The purpose of this study is to establish a nonlinear site response process in time domain by using LS- DYNAwhich provides the soil material with the hysteretic behavior. The calculating response from DEEPSOIL and LS-DYNA in 1D, 2D and 3D will be compared and discussed.
HsuanChih Yang, ShangYi Hsu, WeiKuang Chang
LS-DYNA, nonlinear soil behavior, site response analysis
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F5-013
12:05
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12:20
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INVESTIGATION EXAMPLE OF PIEZO DRIVE CONE USING VARIOUS PENETRATOIN DEVICES
Piezo Drive Cone (i.e., PDC) is a newly developed dynamic sounding tool which can estimate SPT-N values and soil classifications by the measurements of cone penetration depths and excess pore pressures during the dynamic penetration into ground. PDC can choose whether the penetration device is Ram Sounding (i.e., SRS) or Mini Ram Sounding (i.e., MRS) according to the investigation depth and the N value of the ground. In this paper, PDC using SRS was conducted near the site using MRS, and the depth distribution of Nd value and water pressure of both were compared. As a result, regardless of the penetrating device, the depth distribution of Nd value and pore water pressure were similar. Therefore, it was found that the influence of the difference of the penetration device on the results were small. In addition, we introduce an investigation case used a smaller device than MRS called micro RS .
Noriyuki Fujii
dynamic penetration
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