A comparative study of seismic provisions between International Building Code 2003 and Uniform Building Code 1997

This study focuses on the comparison of the Uniform Building Code （UBC） 1997 and International Building Code （IBC） 2003 in relation to the seismic design and analysis of special steel moment resisting frame buildings （SMRF）. This paper formulates a numerical study of a steel SMRF building, studied in four different situations, namely： as an office building in San Francisco; as an office building in Sacramento; as an essential facility in San Francisco, and as an essential facility in Sacramento. The analytical results of the model buildings are then compared and analyzed taking note of any significant differences. This case study explores variations in the results obtained using the two codes, particularly the design base shear and drift ratios as they relate to different locations and occupancy use. This study also proves that IBC 2003 is more stringent for the redundancy factor under design category E for the SMRF building, and drift limits for essential facilities.

DEM simulation of liquefaction for cohesionless media at grain scale

Simulations of undrained tests were performed in a periodic cell using three dimensional(3D) discrete element method(DEM) program TRUBAL.The effective undrained stress paths are shown to be qualitatively similar to published physical experimental results of cohesionless media such as sand.Liquefaction and temporary liquefaction are observed for very loose samples and medium loose samples,respectively.A new micromechanical parameter is proposed to identify whether liquefaction or temporary liquefaction occurs in terms of a redundancy factor.The relationship of redundancy factor and average coordination number is derived theoretically.It is demonstrated that the phase transition dividing the solid-like behaviour and liquid-like behaviour is associated with a redundancy factor of 1,which corresponds to an average coordination number slightly above 4.

Attenuation of arsenic in a karst subterranean stream and correlation with geochemical factors: A case study at Lihu,South China

Arsenic （As） pollutants generated by human activities in karst areas flow into subterranean streams and contaminate groundwater easily because of the unique hydrogeological characteristics of karst areas. To elucidate the reaction mechanisms of arsenic in karst subterranean streams, physical-chemical analysis was conducted by an inductively coupled plasma mass spectrometer and an X-ray fluorescence spectrometer. The results show that inorganic species account for most of the total arsenic, whereas organic arsenic is not detected or occurs in infinitesimal amounts. As（III） accounts for 51.0% ± 9.9% of the total inorganic arsenic. Arsenic attenuation occurs and the attenuation rates of total As, As（III） and As（V） in the Lihu subterranean stream are 51%, 36% and 59%, respectively. To fully explain the main geochemical factors influencing arsenic attenuation, SPSS 13.0 and CANOCO 4.5 bundled with CanoDraw for Windows were used for simple statistical analysis and redundancy analysis （RDA）. Eight main factors, i.e., sediment iron （SFe）, sediment aluminum （SAI）, sediment calcium （SCa）, sediment organic matter （SOM）, sediment manganese （SMn）, water calcium （WCa^2＋）, water magnesium （WMg^2＋）, and water bicarbonate ion （WILCOX） were extracted from thirteen indicators. Their impacts on arsenic content rank as： SFe〉SCa〉WCa^2＋〉SAl〉wHCO3^-〉SMn〉SOM〉WMg^2＋. Of these factors, SFe, SAl, SCa, SOM, SMn, WMg^2＋ and WCa＆2＋ promote arsenic attenuation, whereas WHCO3^- inhibits it. Further investigation revealed that the redox potential （Eh） and pH are adverse to arsenic removal. The dramatic distinction between karst and non-karst terrain is that calcium and bicarbonate are the primary factors influencing arsenic migration in karst areas due to the high calcium concentration and alkalinity of karst water.

Impact of environmental factors on water quality at multiple spatial scales and its spatial variation in Huai River Basin, China

Quantitative assessment of water quality and its spatial variation identification, as well as the discernment of primary factors affecting water quality are in its urgent in water environment management. In this study, four key water quality indicators,namely, ammonia nitrogen(NH_4^+-N), permanganate index(COD_(Mn)), total phosphorus(TP) and total nitrogen(TN) at 71 sampling sites were selected to evaluate water quality and its spatial variation identification. More concerns were emphasized on the anthropogenic factors(land use pattern) and natural factors(river density, elevation and precipitation) to quantify the overall water quality variations at different spatial scales. Results showed that the Yi-Shu-Si River sub-basin had a better water quality status than the Huai River sub-basin. The moderate polluted area nearly distributed in the upper and middle reaches of the Shaying River and Guo River. The high cluster centers which were surrounded with COD_(Mn), NH_4^+-N, TN and TP mainly also distributed in the upper and middle reaches of the Shaying River and Guo River. Redundancy analysis showed that the 200 m buffer area acted as the most sensitive area, which was easily subjected to pollution. The precipitation was identified as the most important variables among all the studied hydrological units, followed by farmland, urban land or elevation. The point source pollution was still existed although the non-point source pollution was also identified. The urban surface runoff pollution was severer than farmland fertilizer loss at the sub-basin scale in flood season, while the farmland showed "small-scale" effects for explaining overall water quality variations. This research is helpful for identifying the overall water quality variations from the scale-process interactions and providing a scientific basis for pollution control and decision making for the Huai River Basin.

DEM SIMULATION OF LIQUEFACTION FOR GRANULAR MEDIA UNDER UNDRAINED AXISYMMETRIC COMPRESSION AND PLANE STRAIN CONDITIONS

Based on three dimensional （3D） Discrete Element Method （DEM）, the paper presents simulation results of undrained tests on loose assemblies of polydisperse spheres under axisymmet- ric compression and plane strain conditions using a periodic cell. In the present work, undrained tests were modelled by deforming the samples under constant volume conditions. The undrained （effective） stress paths are shown to be qualitatively similar to experimental results in literature. A microscopic parameter in terms of redundancy factor （RF） is used to identify the onset of lique- faction （or temporary liquefaction）, with the condition of RF equal to unity defining the transition from ＇solid-like＇ to ＇liquid-like＇ behaviour. It is found that the undrained behaviour is governed by the evolution of redundancy factor under both undrained axisymmetric compression and plane strain conditions, and a reversal of deviatoric stress in stress path for medium loose systems oc- curs due to the fact that the system becomes a structural mechanism （RF 〈 1） transiently at the microscopic level during the evolution.