Pseudo-dynamic testing using conventional testing devices

This paper presents the development of a new type of pseudo-dynamic test system, in which a conventional static jack is utilized for loading. Two of the new hardware devices developed for the system are detailed: a hydraulic pump system that can adjust the rate of oil flow using an inverter motor, and a controller that controls the jack's motion with a displacement feedback signal transmitted from a digital displacement transducer. The unique advantages of the system are summarized as: larger force capacity achieved by the static jack, maximum use of hardware devices available in many existing structural testing laboratories, and flexibility for program development accomplished by separating tasks into multiple PCs. The reliability of the system is calibrated first by a pseudo-dynamic test for an SDOF system and then by a pseudo-dynamic test for a ten-storey building model having hysteretic dampers. For the latter test, substructuring techniques have been incorporated. The accuracy of the results obtained is discussed based upon the capacity of the system to control displacement and comparison with numerical results.     

Spectrophotometric Determination of Zirconium in Thirty-one Geochemical Reference Samples with Xylenol Orange

The zirconium content of 31 geochemical reference samples has been determined by a spectrophotometric method with Xylenol orange after sample decomposition by acid digestion and alkali fusion. The agreement between the present results and published data is generally good.     

Interactions between andesitic magma and poorly consolidated sediments: Examples in the neogene shirahama group, South Izu, Japan

The Upper Miocene-Lower Pliocene Shirahama Group of south Izu, Japan, is a sequence of volcanielastic shallow-sea sediments and subaqueous lava flows. It is gently warped with indistinct preferred orientation and is cross-cut by many andesitic intrusive bodies which range in size from less than a meter to several hundred meters. The intrusive bodies exhibit various shapes and weak preferred orientation, and often have hyaloclastic and peperitic textures along their peripheries. Hydrothermally altered and chaotically disturbed zones of host rocks also occur along the contacts. The areas where the intrusive bodies are abundant are almost coincident with the areas where the more inclined beds and synsedimentary faults are developed. The intrusive bodies dragged the surrounding beds with or without synsedimentary faults. Some intrusions occurred along the faults. Conjugate sets of the faults indicate that they were produced under unstable stress conditions. These relationships between the beds and the intrusive bodies are assumed to have originated mostly by interaction between hot magma and poorly consolidated wet sediments at a shallow depth beneath the sea floor. When the intrusions took place, the stress conditions in the beds were irregular and unstable, judging from the shapes and orientation of the intrusive bodies, and also from the deformation characteristics of the enclosing beds. Some of the intrusive bodies are probably feeder dikes which supplied lave to the Shirahama Group.     

Tree ring information and rainfall characteristic for landslide in the Kobe District,Japan

Heavy rainfall on the south side of the Rokko Mountains has often caused severe landslides and debris flows. Analysis of the annual summation of rainfall in excess of 100 mm/day shows that the rainfall in this area has dominant periodicities of about 25–30, 10–13, and 5–7 years. The period of about 25–30 years corresponds to that of occurrence of the natural disasters produced by heavy rainfall; years when the maximum rainfall correspond to years when there have been severe landslides and debris flows in the area. Temporal change in this rainfall may provide a first approximation for erosional force. Analyses of tree ring width from these mountains indicate that the sequences have a dominant periodicity of about 25–30 years. Cross-spectral analyses for rainfall and ring width in this area show high coherency for the periods of about 25–30 years; evidence that variations in the ring width may be used as proxy data for erosional force.     

Along-arc lateral variation of Rb−Sr and K−Ar ages of Cretaceous granitic rocks in Southwest Japan

Cretaceous granitic rocks were emplaced over a distance of 700 km along arc in Southwest Japan. Rb–Sr and K–Ar ages of a major group of these granitic rocks, with ilmenite series ore mineralogy, were examined. Rb–Sr whole rock ages of 92.8±4.0 Ma and Rb–Sr and K–Ar biotite ages of 80–88 Ma were obtained on one group of these granitic rocks from Kamo-Sera area of central Hiroshima Prefecture. The K–Ar ages of various minerals, combined with the Rb–Sr whole-rock age, give a smooth cooling curve, which suggests a 5 to 10 Ma time-lag between intrusion and cooling at 300° C for the Cretaceous granitic rocks. The Rb–Sr whole-rock and Rb–Sr/K–Ar biotite ages of these granitic rocks become younger eastward along the Southwest Japan arc, and the time-lag between the two systems remains constant at 5 to 10 Ma over the entire area. The along-arc age variation does not support the genetical relationship of the Cretaceous granitoids with steady-state subduction. The Cretaceous granitic province at the eastern margin of Eurasian continent was, at least partly, formed by an episodic event such as ridge subduction.     

Anthropogenic influence on sedimentation during the last 100 years inferred from magnetic properties in the Changjiang Estuary, China

A 100-year sedimentary record in the Changjiang Estuary was examined to elucidate natural and anthropogenic influences on the morphodynamic evolution of the estuary. Two gravity cores were acquired and their magnetic properties, sediment size, chemical elements and ²¹⁰Pb geochronology were analyzed to infer the sedimentation. The results indicate that these sedimentological indexes, especially magnetic properties and trace elements, changed significantly during the last 100 years, with an abrupt change occurring at around 1960. This abrupt change is likely the result of a reduction in hydrodynamic energy caused by the narrowing of an upstream estuary reach due to reclamation. An increase of terrigenous input, due to soil erosion in the upper and middle reaches of the Changjiang, and increases in steel production may have also had a significant influence, as indicated by studies of other locations in the Changjiang drainage basin.     

High-rate precise point positioning (PPP) to measure seismic wave motions: an experimental comparison of GPS PPP with inertial measurement units

High-rate GPS has been widely used to construct displacement waveforms and to invert for source parameters of earthquakes. Almost all works on internal and external evaluation of high-rate GPS accuracy are based on GPS relative positioning. We build an experimental platform to externally evaluate the accuracy of 50-Hz PPP displacement waveforms. Since the shake table allows motion in any of six degrees of freedom, we install an inertial measurement unit (IMU) to measure the attitude of the platform and transform the IMU displacements into the GPS coordinate system. The experimental results have shown that high-rate PPP can produce absolute horizontal displacement waveforms at the accuracy of 2–4 mm and absolute vertical displacement waveforms at the sub-centimeter level of accuracy within a short period of time. The significance of the experiments indicates that high-rate PPP is capable of detecting absolute seismic displacement waveforms at the same high accuracy as GPS relative positioning techniques, but requires no fixed datum station. We have also found a small scaling error of IMU and a small time offset of misalignment between high-rate PPP and IMU displacement waveforms by comparing the amplitudes of and cross-correlating both the displacement waveforms.