20-m Length Research Articles

Numerical Analysis of Single Stepped Axially Loaded Pile

Abstract: This study investigates the behavior of a single pile under axial loading in granular soil layers. The study aims to determine the impact of stepping on load settlement behavior and load transformation along the pile, as it relates to depth. The pile has a diameter (D) of 1m and a length (L) of 20m. For the stepped pile, the upper portion is half the length of the pile and the lower portion is the remaining half. The total length and volume of the pile are kept constant for both the single conventional pile and single stepped pile. In the analysis, the diameter of the upper portion of the stepped pile is reduced (stepped pile) by 0.1D to 0.3D, and the diameter of the lower portion is calculated accordingly. Also the load transformation with respect to depth of pile is studied. Based on numerical analysis, the single stepped pile outperforms the single conventional pile in load settlement behavior.

Thermal-structural analysis of a square solar sail

The aim of this work is to improve an efficient methodology, recently developed to study the structural response of a classical square solar sails in free flight, under the action of the solar radiation pressure. The new approach models the effect of thermal loads acting on the sail's reflective surface. In particular, a square solar sail with a side length of 20m at 1au distance from the Sun is analyzed for different values of incidence and clock angles. The thermal-structural analyses are carried out under the assumption that the stress-displacement solution depends on the temperature field, but there is no inverse dependency. The thermal loads, for some attitude conditions, are shown to have remarkable effects on the sail deformation.

Experimental study on influence of vegetation coverage on runoff in wind-water erosion crisscross region

Using artificial rainfall simulation method, 23 simulation experiments were carried out in water-wind erosion crisscross region in order to analyze the influence of vegetation coverage on runoff and sediment yield. The experimental plots are standard plots with a length of 20m, width of 5m and slope of 15 degrees. The simulation experiments were conducted in different vegetation coverage experimental plots based on three different rainfall intensities. According to the experimental observation data, the influence of vegetation coverage on runoff and infiltration was analyzed. Vegetation coverage has a significant impact on runoff, and the higher the vegetation coverage is, the smaller the runoff is. Under the condition of 0.6mm/min rainfall intensity, the runoff volume from the experimental plot with 18% vegetation coverage was 1.2 times of the runoff from the experimental with 30% vegetation coverage. What’s more, the difference of runoff is more obvious in higher rainfall intensity. If the rainfall intensity reaches 1.32mm/min, the runoff from the experimental plot with 11% vegetation coverage is about 2 times as large as the runoff from the experimental plot with 53%vegetation coverage. Under the condition of small rainfall intensity, the starting time of runoff in the experimental plot with higher vegetation coverage is later than that in the experimental plot with low vegetation coverage. However, under the condition of heavy rainfall intensity, there is no obvious difference in the beginning time of runoff. In addition, the higher the vegetation coverage is, the deeper the rainfall infiltration depth is.The results can provide reference for ecological construction carried out in wind erosion crisscross region with serious soil erosion.

Flame thickness and propagation characteristics of premixed methane-air explosion with a small filling ratio in an open-ended steel pipe

Through establishing a non-adiabatic open-ended steel pipe with a length of 20m and a cross-sectional area of 0.08m×0.08m, the changing rules of flame propagation and flame thickness of premixed methane/air explosion with a 10% fuel concentration and a 20% filling ratio were revealed. The experimental results show that the flame arrival time increased gradually with the increase of the distance from the ignition source, the maximum flame signal value initially increased along the pipe but then dropped. The flame thickness at a certain point could be measured by the time differences between vanishing moment and initial rising moment of flame signal at this point. With the increase of the distance from the ignition source, the flame thickness gradually decreased, the flame propagation speed presented a changing trend of increasing and decreasing, while the maximum overpressure followed a trend of decreasing, increasing and decreasing. The research results provide the scientific experimental basis for the reasonable setting mine explosion-resistant device, it is of great significance to effectively restrain the spread of explosion flame surface and avoid accident enlarging of gas explosion in coal mine.

Performance Analysis of Earth-air Heat Exchangers in Hot Summer and Cold Winter Areas

As one of the energy-efficient heating technologies, earth air heat exchangers (EAHE) use renewable energy (i.e. geo-thermal energy) to first heat outdoor air, and then supply it to indoors for space heating in winter. The aim of this paper is to study the thermal performance of EAHE in winter in hot summer and cold winter areas. An experimental setup of EAHE was established in Changsha, China. Different variables, including soil temperature, supply air temperature and outdoor air temperature were measured for one week. The thermal performance was evaluated based on the data analysis. Results show that the supply air temperature reached the soil temperature around the pipe at the same length of 20m for different inlet air temperature. The COP and Q decreased along with the increase of inlet air temperature but increased along with the pipe length. Moreover, the thermal saturation of soil occurred in the fifth day of the week, and thermal interference between pipes can be ignored under the 1m distance between pipes. Our future work includes developing a numerical model to analyze and optimize the thermal performance of EAHE, thereby providing a reference for its design and application in hot summer and cold winter areas in China.

高層建築物の外装材に作用する風力に対する外圧および内圧の影響

The purpose of this study is to understand the effects of the external pressures and internal pressures on the wind loads to use in wind-resistant design for the cladding of high-rise buildings. In order to measure the external pressures acting on the assumed high-rise building, a wind tunnel experiment using the reduced scale model of 1/250 was conducted. This assumed building is a high-rise building with an eaves-height of 45m having a rectangular plane width of 40m and a depth of 25m. The wind tunnel facility used in the experiment was the closed-circuit type boundary-layer wind tunnel having a testing section length of 20m, height of 2.5m and width of 3.6m. The characteristics of the boundary-layer flow used in the experiment were to match the nominal flow of the flat terrain of neutral stability conditions. The external pressures on the scale model of the assumed high-rise building were measured using the multi channel simultaneous measuring system (MCSMS). Details of the wind tunnel experiment are discussed in Chapter 2. The numerical simulation used both a leakage flow model and the external pressure was conducted to estimate the internal pressures in the assumed building induced by the wind. The leakage flow model has been constructed by applying Poiseuille's law. Details of the numerical simulation are discussed in Chapter 3. The net pressure was evaluated by subtracting the internal pressure from the external pressure. In Chapter 4 the properties of the net pressure coefficient, the external pressure coefficient, the internal pressure coefficient, and the power spectrum density distribution and probability density distribution are discussed. In Chapter 5 the correlation properties of between the external pressures and the internal pressures are discussed. In Chapter 6 the properties of the peak values (maximum and minimum) of the essential net pressure coefficients to the wind-resistant design of the cladding are discussed. Both of the largest peak net pressure coefficients and the largest peak external pressure coefficients (worst value in any wind direction) are compared with the recommendations values (2015) of AIJ in this Chapter. In Chapter 7 the method of approximating the peak net pressure using the mean internal pressure and the peak external pressure is discussed. Furthermore, in this Chapter the method approximating the peak net pressure using the peak external pressure and the peak internal pressure is also discussed. From the above results, the following findings were obtained. 1) The effects on the net pressure fluctuations of the external pressure fluctuations are more dominant than the internal pressure fluctuations. 2) The effects on the net pressures of the partitions are remarkable in case of a low airtight. 3) The probability distribution of the net pressure can be approximated by a Gamma distribution or Gauss distribution based on the skewness, the same as external and internal pressure. 4) The correlation coefficients between the external pressures and internal pressures on the cladding are almost positive values. 5) The largest (worst) maximum net pressure coefficient for any wind direction on the cladding of the assumed high-rise building of a high airtight almost agreed with the recommendation values (2015) of AIJ. 6) The tightness effects on the largest minimum net pressure coefficient are small. 7) In case of the building with a high airtight, the peak net pressure on the cladding can be approximated using the mean internal pressure and the peak external pressure. 8) The peak net pressure on the cladding obtained from the peak value of the external pressure and internal pressure is evaluated on the safety side, in case of independent.

BALU: Largest autoclave research facility in the world

Among the large-scale facilities operated at the Center for Lightweight-Production-Technology of the German Aerospace Center in Stade BALU is the world's largest research autoclave. With a loading length of 20m and a loading diameter of 5.8 m the main objective of the facility is the optimization of the curing process operated by components made of carbon fiber on an industrial scale. For this reason, a novel dynamic autoclaving control has been developed that is characterized by peripheral devices to expend the performance of the facility for differential applications, by sensing systems to detect the component state throughout the curing process and by a feedback system, which is capable to intervene into the running autoclave process.

Gain clamped L-band EDFA with forward–backward pumping scheme using fiber Bragg grating

The paper proposes a novel two stage L-band erbium doped fiber amplifier with forward–backward pumping scheme for transmission of 32 wavelength division multiplexed (WDM) channels. It is gain clamped with an in-line fiber Bragg grating (FBG) to provide flat gain over 45nm by restricting and reutilizing amplified spontaneous emission (ASE). We demonstrate that it provides an efficient small signal gain with minimum noise figure of over 20dB and 5.5dB, respectively, in the L-band region (1565–1610nm) by comparing with its forward and backward pumped counterparts with fixed Er3+ fiber length of 20m for −30dBm/channel input power. We also obtain the gain and noise figure dependence as a function of each of the Er3+ fiber lengths, pump power (both 1480 and 980nm), and temperature. Hence a 10nm region (1580–1590nm) has been acknowledged where temperature variations become constricted for 30°C variations (15–45°C).

KL-510 하중에 의한 강판형교의 동적응답

본 연구에서는 교량의 노면조도 및 교량과 차량 사이의 상호작용을 고려한 수치해석방법을 사용하여 도로교설계기준에 규정된 표준트럭 하중인 KL-510에 의한 강판형교의 동적응답을 연구하였다. 대상교량은 건설부에서 제정한 "도로교 상부구조 표준도"에 수록되어 있는 지간이 20m, 30m와 40m인 단순 강판형교를 사용하고. "보통의 도로"에 대하여 생성시킨 10개의 노면조도를 사용하였다. 차량은 5축 트랙터-트레일러인 표준트럭하중 KL-510을 3차원 차량으로 모델링하고, 교량은 주형을 보요소로, 콘크리트 바닥판은 쉘요소로, 주형과 콘크리트 바닥판 사이는 Rigid Link를 사용하여 3차원으로 모델링하였다. 이와 같은 노면조도 및 차량을 사용하여 강판형교의 충격계수와 DLA를 구하고 각국의 설계기준과 비교 검토하였다. Dynamic response of steel plate girder bridges by KL-510 design truck in KHBDC considering the road surface roughness of bridges and bridge-vehicle interaction is investigated. Simply supported steel plate girder bridges with span length of 20m, 30m, and 40m from "Standard Highway Bridge Superstructure" published by the Korean Ministry of Construction are used for a bridge model, and ten sets of the road surface roughness of bridge deck are generated from power spectral density (PSD) function by assuming the roadway as "Average Road". A three dimensionally modeled 5-axle tractor-trailer with its gross weight, which is the same as that of KL-510 design truck, is used for dynamic analysis. For the finite element modeling of superstructure, beam element for the main girder, shell element for the concrete deck, and rigid link between main girder and concrete deck are used. Impact factor and DLA of steel plate girder bridges for different span are calculated by the proposed numerical analysis model and compared with those specified by several bridge codes.

熱収支法による広域路面温度予測モデル―乾燥路面の路線温度分布予測―

SAFF model proposed in this study allows to forecast the road surface temperature along a road network using the DSM and heat balance method. The accuracy of the SAFF model was identified by comparing observed thermal mapping data and forecast results at 631 selected stretches (each with a length of 20m) of KASUGA-WADAYAMA road (12.6km) in Hyogo prefecture. The SAFF model had 58% and 86% of spatial accuracy rate for the calculation of Ts with an error of less than 1°C and 2°C based on all road stretches, respectively. The mean absolute error of Ts over the entire route and calculation term of 45 hours was 1.5°C and the error was smaller during the nighttime than the daytime. CPU time with an algorithm to combine mountain elements and to remove invisible mountain elements from calculation routine was reduced to 1/23 of that without the algorithm. Consequently, the SAFF model made it possible for one hour forecast of the spatial variation in dry road surface temperature over the entire KASUGA-WADAYAMA road.

Investigações geofísicas na borda da bacia sedimentar de São Paulo

Este artigo mostra resultados parciais de investigações geofísicas realizadas na borda da Bacia Sedimentar de São Paulo, dentro do campus da Universidade de São Paulo. O principal objetivo desta pesquisa é a caracterização dos sedimentos e do topo das rochas do embasamento da bacia, utilizando os métodos GPR-Ground Penetrating Radar e Resistividade Elétrica. Os perfis geofísicos foram realizados ao longo de uma mesma linha, visando comparar os resultados com as duas metodologias. Um perfil de 216m foi adquirido com as antenas de 50 MHz e um perfil de resistividade com dipólos de 20m. Além disso, duas Sondagens Elétricas Verticais - SEV's foram feitas sobre a mesma linha. A análise do perfil GPR permitiu identificar o limite entre a base do solo e uma camada de areia. Os resultados estão de acordo com as informações de poços. O perfil elétrico identificou uma zona anômala de condutividade entre 80 e 110 m, relacionada provavelmente com uma zona de cizalhamento.

Comparison between Data from Test Train Running on Track Irregularities Artificially Set and Results of Vehicle Dynamics Simulation (Influence of Track Gauge Variation on Rail Vehicle Dynamics)

Responses of test train running on track irregularities artificially set on SHINKANSEN and results of vehicle dynamics simulation were compared at a speed up to 2l0km/h. In comparison between the measurements and simulation using basic parameters, the response to alignment irregularity of the measurements and simulation for the wave length longer than 40m is nearly identical, although that of simulation becomes apparently larger than that of measurements for wave length of 20m. Then the state of track irregularity artificially set was precisely investigated and an enlargement of gauge in the section of 20m wave length was found. And simulation of the response assuming the gauge enlargement was nearly identical with that of measurements. In this report, the influence of wave length and gauge variation on the response to track irregularity mentioned above is analyzed by comparing between measurements and simulation. Besides, using the same simulation program, the influence of gauge variation on carbody hunting motion of a new high speed SHINKANSEN train which has soft suspension between carbody and bogie due to bolsterless bogie is studied.

Comparison between Data from Test Train Running on Track Irregularities Artificially Set and Results of Vehicle Dynamics Simulation (Influence of Track Gauge Variation on Rail Vehicle Dynamics)

Abstract Responses of test train running on track irregularities artificially set on SHINKANSEN and results of vehicle dynamics simulation were compared at a speed up to 2l0km/h. In comparison between the measurements and simulation using basic parameters, the response to alignment irregularity of the measurements and simulation for the wave length longer than 40m is nearly identical, although that of simulation becomes apparently larger than that of measurements for wave length of 20m. Then the state of track irregularity artificially set was precisely investigated and an enlargement of gauge in the section of 20m wave length was found. And simulation of the response assuming the gauge enlargement was nearly identical with that of measurements. In this report, the influence of wave length and gauge variation on the response to track irregularity mentioned above is analyzed by comparing between measurements and simulation. Besides, using the same simulation program, the influence of gauge variation on carbody hunting motion of a new high speed SHINKANSEN train which has soft suspension between carbody and bogie due to bolsterless bogie is studied.

Study of triggering lightning by using TEA CO2 laser.

A possibility of triggering lightning using laser is investigated. A long plasma channel is produced in atmospheric air when pulsed CO2 laser radiation is focused by a mirror. Length of plasma channels are measured for focal length of 10m, 20m, 30m, 45m and 60m respectively. A length of 30m plasma channel is produced when a energy. of 50 J unstable mode is focused by the mirror having 60m focal length. The propagated unstable mode patterns and intensities are calculated using the Fresnel diffraction integral, and compared with experimental results.The plasma channel produced by the mirror of 10m focal length is applied for triggering electrical discharge. The arc which has the length of 1.8m is triggered and guided by the plasma channel, and some characteristics are obtained.

Thermal Cracking of Kerosene and Heavier Petroleum Fractions by Pneumatic Transport Reactor

A bench scale unit of pneumatic transport reactor was tested for thermal cracking of kerosene and heavier petroleum fractions. The reactor consisted of a stainless steel tubing, inside diameter of 16mm and length of 20m, which was housed in a furnace as 20 turnings spiral of 32cm in diameter. Sand was used as the suspending solid. Cracking was carried out at temperatures ranging from 650 to 770°C, sand to oil mass flow ratio ranging from 0 to 0.5, and feed rate ranging from 5 to 12kg/hr. Normal functioning of the transport cracking unit was ensured by a continuous operation for over 30hrs without steam dilution. Inner wall of the reactor tube remained clean from carbonaceous materials, which were carried away out of the system with the suspending solid.Overall gasification as well as the composition of gaseous products from both kerosene and heavier fractions were found to be similar with those reported on naphtha cracking process. Analyses also revealed that, under elevated cracking temperatures, liquid products were composed purely of aromatic hydrocarbons: mainly methyl derivatives of benzene and naphthalene. It was thus concluded that the pneumatic transport reactor deserved further developments as a cracking unit for heavier petroleum fractions.

鋼ぐいの腐食防食試験

Numerous steel pilings have been used as load-bearing foundations in soils, but there have been few studies on corrosion and corrosion prevention for such pilings. Therefore, tests have been carried out to study on these aspects of problems with special reference to a reclaimed land since a few years ago.This report includes data relating to the corrosion rate and the effect of cathodic protection of driven test piles, each having a diameter of 165.2mm and a length of 20m.The results of one-year tests indicated that the corrosion rate was about 0.1mm/yr, the protective current density required was about 15-20mA/m2 and the vertical potential distribution of the piles was almost uniform.The Norwegian Geonor's corrosion sounding apparatus was employed to measure the soil corrosivity. The result of the corrosion sounding was approximately equal to the corrosion rate of the test piles.Further tests are in progress.