Modeling of tensile strength on moist granular earth material at low water content   总被引：4，自引：0，他引：4  

Tae-Hyung Kim  Changsoo Hwang 《Engineering Geology》2003,69(3-4):233-244

While most research has mainly focused on the volume change, flow, and shear strength of unsaturated earth materials, investigations of tensile strength of unsaturated earth materials especially granular materials have not received much attention except for cemented and clayey materials. Thus, direct tension experiments were carried out to quantify the actual magnitude of tensile strength induced by water in moist granular soil at especially low water contents (w<4%). The magnitudes of the measured tensile strength are significantly different from zero. A simple experimental tensile strength model is proposed. Practicing engineers can use this model for approximate estimation of the tensile strength of unsaturated granular soils without experiments and for precise design or analysis of most engineered facilities relying on the unsaturated granular soils in the vadose zone. The experimental data are also compared with a theoretical model developed for monosized spheres at low water contents, and its application for a real granular earth material having a variety of particles is discussed. The nonlinear behavior of the tensile strength for moist granular soil is appropriately simulated with a model.  相似文献   

Seismic demand based on damage control model—considering basin effect and source effect     

Chin-Hsiung Loh  Chau-Shen Hwang  Wen-Yu Jean 《Soil Dynamics and Earthquake Engineering》1998,17(5):335-345

The Park and Ang damage model was used as the "Structural Damage Control Model" to study the seismic design parameters. This damage control model included the displacement ductility and hysteretic energy in the analysis of elastic-perfect-plastic single-degree-of-freedom system. Based on this damage control model, the reduction factor and yield base shear coefficient are discussed. Seismic data collected from Taipei basin were used to examine the code-provided yield base shear coefficient which reflects the influence of using a damage control model in the seismic design parameter. Effects of seismic source as well as Taipei basin topography are also considered in examining the variation of yield base shear coefficient.  相似文献   

Inverse Vening Meinesz formula and deflection-geoid formula: applications to the predictions of gravity and geoid over the South China Sea   总被引：12，自引：0，他引：12  

C. Hwang 《Journal of Geodesy》1998,72(5):304-312

Using the spherical harmonic representations of the earth's disturbing potential and its functionals, we derive the inverse Vening Meinesz formula, which converts deflection of the vertical to gravity anomaly using the gradient of the H function. The deflection-geoid formula is also derived that converts deflection to geoidal undulation using the gradient of the C function. The two formulae are implemented by the 1D FFT and the 2D FFT methods. The innermost zone effect is derived. The inverse Vening Meinesz formula is employed to compute gravity anomalies and geoidal undulations over the South China Sea using deflections from Seasat, Geosat, ERS-1 and TOPEX//POSEIDON satellite altimetry. The 1D FFT yields the best result of 9.9-mgal rms difference with the shipborne gravity anomalies. Using the simulated deflections from EGM96, the deflection-geoid formula yields a 4-cm rms difference with the EGM96-generated geoid. The predicted gravity anomalies and geoidal undulations can be used to study the tectonic structure and the ocean circulations of the South China Sea. Received: 7 April 1997 / Accepted: 7 January 1998  相似文献   

A practical reliability-based method for assessing soil liquefaction potential     

J. H. Hwang  C. W. Yang  D. S. Juang 《Soil Dynamics and Earthquake Engineering》2004,24(9-10):761

The current simplified methods for assessing soil liquefaction potential use a deterministic safety factor in order to judge whether liquefaction will occur or not. However, these methods are unable to determine the liquefaction probability related to a safety factor. An answer to this problem can be found by reliability analysis. This paper presents a reliability analysis method based on the popular Seed'85 liquefaction analysis method. This reliability method uses the empirical acceleration attenuation law in the Taiwan area to derive the probability density distribution function (PDF) and the statistics for the earthquake-induced cyclic shear stress ratio (CSR). The PDF and the statistics for the cyclic resistance ratio (CRR) can be deduced from some probabilistic cyclic resistance curves. These curves are produced by the regression of the liquefaction and non-liquefaction data from the Chi-Chi earthquake and others around the world, using, with minor modifications, the logistic model proposed by Liao [J. Geotech. Eng. 114 (1988) 389]. The CSR and CRR statistics are used in conjunction with the first order and second moment method, to calculate the relation between the liquefaction probability, the safety factor and the reliability index. Based on the proposed method, the liquefaction probability related to a safety factor can be easily calculated. The influence of some of the soil parameters on the liquefaction probability can be quantitatively evaluated.  相似文献   

Seismic response of natural gas and water pipelines in the Ji-Ji earthquake   总被引：3，自引：0，他引：3  

Walter W. Chen  Ban-jwu Shih  Yi-Chih Chen  Jui-Huang Hung  Howard H. Hwang 《Soil Dynamics and Earthquake Engineering》2002,22(9-12):1209-1214

In order to study the damage patterns of natural gas and water pipelines in the Ji-Ji earthquake, a GIS database and analysis procedures were established. Repair statistics was obtained from major natural gas companies and the Taiwan Water Supply Corporation (TWSC), and entered into the system. Then, repair rates (RR) were calculated. Previously, damage was analyzed without considering the corresponding pipeline material and diameters. In this study, new attempts were made to collect more data including those related to the composition of pipelines to provide a more detailed analysis of the relationship between earthquake forces and the resulting damage. Statistical analysis was also conducted to understand the correlation between RR and seismic parameters such as the peak ground acceleration, peak ground velocity, and spectrum intensity.  相似文献   

Structural development and tectonic evolution of Gunsan Basin (Cretaceous–Tertiary) in the central Yellow Sea     

Young Jae Shinn  S.K. Chough  In Gul Hwang 《Marine and Petroleum Geology》2010

This study analyzes the structural development of the Gunsan Basin in the central Yellow Sea, based on multi-channel seismic reflection profiles and exploratory well data. The basin comprises three depressions (the western, central, and eastern subbasins) filled with a thick (ca. 6000 m) Cretaceous to Paleogene nonmarine succession. It was initiated in the early Cretaceous due to intracontinental extension caused by oblique subduction of the Izanagi plate under the Eurasian plate and sinistral movement of the Tan-Lu fault. The basin appears to have undergone transtension in the late Cretaceous–Eocene, caused by dextral movement of the Tan-Lu and its branching faults. The transtension was accommodated by oblique intra-basinal normal faults and strike-slip (or oblique-slip) movement of a NE-trending bounding fault in the northern margin of the central subbasin. The entire basin was deformed (NE–SW contraction) in the Oligocene when tectonic inversion occurred, possibly due to the changes in strike-slip motion, from right- to left-lateral, of the Tan-Lu fault. During the early Miocene, extension resumed by reactivation of the pre-existing normal and transpressional faults. A combination of extension, uplift, and erosion resulted in differential preservation of the early Miocene succession. At the end of the early Miocene, extension ceased with mild contraction and then the basin thermally subsided with ensued rise in sea level.  相似文献   

The ultraluminous and hyperluminous infrared galaxies in the Sloan Digital Sky Survey, 2dF Galaxy Redshift Survey and 6dF Galaxy Survey     

Ho Seong Hwang  Stephen Serjeant  Myung Gyoon Lee  Kang Hwan Lee  Glenn J. White 《Monthly notices of the Royal Astronomical Society》2007,375(1):115-127

We present a result of cross-correlating the Infrared Astronomical Satellite Faint Source Catalogue with the spectroscopic catalogues of galaxies in the Fourth Data Release of the Sloan Digital Sky Survey, the Final Data Release of the 2dF Galaxy Redshift Survey (2dFGRS) and the Second Data Release of the 6dF Galaxy Survey. We have identified 324 ultraluminous infrared galaxies (ULIRGs) including 190 newly discovered ULIRGs, and two hyperluminous infrared galaxies. Adding these new ULIRGs, we increase the number of known ULIRGs by about 30 per cent. The reliability of the cross-correlation is estimated using the likelihood ratio method. The incompleteness of our sample introduced by the identification procedure in this study is estimated to be about 5 per cent. Our sample covers the redshift range of   z = 0.037–0.517  with a median redshift of     , which is larger than that     of the sample of previously known ULIRGs.  相似文献   

Torsion design implications from shake‐table responses of an RC low‐rise building model having irregularities at the ground story          下载免费PDF全文

Han Seon Lee  Kyung Ran Hwang 《地震工程与结构动力学》2015,44(6):907-927

A 1:5 scale five‐story RC building model having the irregularities of a soft/weak story and torsion at the ground story was subjected to a series of earthquake simulation tests. The test results reveal the following: The eccentricity varied from zero to infinity with the values of base shear and torque bounded by some limits. As the intensity of table excitations increased, representing earthquakes with return periods from 50 to 2500 years in Korea, the range of eccentricities at the peak values in the time histories of drift and base shear decreased from approximately ±30% to within ±10% of the transverse dimension of the model. The inertial torque was resisted by both longitudinal and transverse frames, in proportion to their instantaneous rigidity. Yielding of the longitudinal frames under severe table excitations caused a substantial loss in their instantaneous torsional resistance and thereby transferred most of the large torque to the transverse frames, resulting in a significantly degraded torsional stiffness with an enlarged torsional deformation despite almost zero eccentricity. From these observations, it is clear that the eccentricity in itself cannot represent the critical torsional behaviors. To overcome this problem, the demand in torque shall be determined in a direct relationship with the base or story shear, given as an ellipse constructed with the maximum points in its principal axes located by the two adjacent torsion‐dominant modal spectral values. This approach provides a simple but transparent design tool by enabling comparison between demand and supply in shear force–torque diagrams. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Retrofit of reinforced concrete frames with buckling‐restrained braces          下载免费PDF全文

Christoph Mahrenholtz  Pao‐Chun Lin  An‐Chien Wu  Keh‐Chyuan Tsai  Shyh‐Jiann Hwang  Ruei‐Yan Lin  Muhammad Y. Bhayusukma 《地震工程与结构动力学》2015,44(1):59-78

Damage to buildings observed in recent earthquakes suggests that many old reinforced concrete structures may be vulnerable to the effects of severe earthquakes. One suitable seismic retrofit solution is the installation of steel braces to increase the strength and ductility of a building. Steel bracings have some compelling advantages such as their comparatively low weight, their suitability for prefabrication, and the possibility of openings for utilities, access, and light. The braces are typically connected to steel frames that are fixed to the concrete structure using post‐installed concrete anchors along the perimeter. However, these framed steel braces are not without some disadvantages such as heavier steel usage and greater difficulties during the installation. Therefore, braces without steel frames appear to be an attractive alternative. In this study, braces were connected to gussets furnished with anchor brackets, which were fixed by means of a few post‐installed concrete anchors. The clear structural system and the increased utilization of the anchors allowed the anchorage to be designed precisely and economically. The use of buckling‐restrained braces (BRBs) provides additional benefits in comparison with conventional braces. BRBs improve the energy dissipation efficiency and allow the limitation of the brace force to be taken up by the highly stressed anchorage. Cyclic loading tests were conducted to investigate the seismic performance of BRBs connected with post‐installed anchors used to retrofit reinforced concrete frames. The tests showed that the proposed design method is feasible and increases strength as well as ductility to an adequate seismic performance level. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

A Method for Analyzing the Self-Supported Earth-Retaining Structure Using Stabilizing Piles     

Changyoung Kim  Jeonggeun Kwon  Sungpil Hwang 《Marine Georesources & Geotechnology》2013,31(4):313-332

The self-supported earth-retaining structure using stabilizing piles (SSR is used from here) has the advantages of less deformation and less internal force compared with conventional cantilever retaining structure. It is easier to conduct the excavation when SSR is used for an excavation instead of using braced excavation with struts. The SSR is better than other methods to the 10 m shallow excavation depth in terms of economical and constructional efficiency when the ground is not very soft. However, this SSR method lacks a theoretical basis in terms of geotechnical engineering. The objective of this study is to develop a method of analysis by laboratory model tests. A variety of model tests were performed in order to analyze the behavior of SSR and the ground, and to measure the stress acting on stabilizing piles relative to excavation steps and earth pressures on the wall. The analysis reveals the failure mechanism of a wedge and then suggests a method for calculating a virtual supported point. These findings were incorporated into a method for analyzing retaining wall, stabilizing piles, and beams connecting two structures. Future research is geared toward developing a design program that uses the analytical methodology for this SSR.  相似文献