Model Test and Back Analysis of Shield Tunnel Load Distribution in Soft Clay

Each year many prestressed-concrete (P/C) girder bridges are damaged by overheight vehicles or vehicles transporting overheight loads. The effects of this type of loading on P/C bridge behavior was investigated for various types and locations of intermediate diaphragms. The research included a comprehensive literature review; a survey of design agencies; the testing of a full-scale, simple-span, P/C girder-bridge model with eight intermediate diaphragm configurations, as well as a model without diaphragms; and the finite-element analyses of the bridge model assuming both pinned- and fixed-end conditions. The vertical load distribution was determined to be essentially independent of the type and location of the intermediate diaphragms, while the horizontal load distribution was a function of the intermediate diaphragm type and location. Construction details at the girder supports produced significant rotational-end restraint for both vertical and horizontal loading. Both the vertical and horizontal load distributions were found to be affected by the girder-end restraint. A fabricated intermediate structural steel diaphragm was determined to provide essentially the same type of response to lateral and vertical loads that was provided by the reinforced-concrete intermediate diaphragms presently used by the Iowa Department of Transportation.

Optimizing ploughing performance: The role of traction-control cylinder pressure on tractor wheel load

Using instrumented small-scale models to study structural load paths in wood-framed buildings

Effects of external trunk loads on lumbar spine stability

The study of earth pressure distribution on buried structures has a great practical importance in constructing highway embankments above pipes and culverts. Based on Spangler’s research, the supporting strength of a conduit depends primarily on three factors: 1) the inherent strength of the conduit; 2) the distribution of the vertical load and bottom reaction; and 3) the magnitude and distribution of lateral earth pressures which act against the sides of the structure. Rigid culverts are frequently used in Kentucky for routing streams beneath highway embankments because of rolling and mountainous terrain, numerous streams, shallow depths to bedrock, which creates unyielding foundations, and the necessity of using high fills which create large vertical stresses acting on culverts. As a means of exploring ways of reducing large vertical earth pressures acting on a buried structure, ultra-lightweight geofoam was placed in a trench above a reinforced rigid box culvert in Russell County, KY. This study provides strong evidences from both numerical model analysis and in-situ test data to indicate that geofoam is an ideal elasto-plastic material to reduce vertical load on top of a rigid culvert resting on a rigid foundation. The load on the top of a culvert can be reduced to 20% of traditional design load after 2-ft-thick geofoam is placed on top of it. Results from numerical model are more conservative when compared to actual test data. As much as 57% of settlement from geofoam has been recorded. Stresses on the top of a culvert where geofoam was placed have reached a relatively stable level which is expected at the yield point of the geofoam. This technology can be used in applications which require controlled pressure on rigid underground structure. Whether geogoam is used or not used, the model analysis and test data show that the earth pressure acting on the sidewall does not change significantly. Although the pressure acting on the sidewall is slightly higher when geofoam is used on top of the culvert only, the value is still below the design value used by the Kentucky Transportation Cabinet. Use of geofoam placed in an imperfect trench significantly reduces the vertical stresses acting on the top of the culvert.

Petroleum platforms in the U.S. Gulf of Mexico (GOM) are important habitats for fishes and support regional fisheries. However, drivers of the horizontal (i.e., latitudinal and longitudinal) and vertical (i.e., position in the water column) distribution patterns of fishes associated with these artificial habitats are not fully understood on a GOM-wide scale. To build upon previous studies on a large spatial scale and focus on species-specific drivers, we conducted 114 submersible rotating drop-camera and water quality sonde surveys at 54 platforms throughout the GOM. We then fitted two sets of binomial generalized additive mixed models integrating environmental and structural (i.e., characteristics of platforms) predictors to encounter/nonencounter data for 17 fish species so as to understand their horizontal and vertical distribution patterns throughout the GOM in platform habitat. Significant predictors for horizontal distribution included distance from shore (for Bermuda Chub Kyphosus saltatrix, Greater Amberjack Seriola dumerili, Vermilion Snapper Rhomboplites aurorubens), salinity (Bermuda Chub, Red Snapper Lutjanus campechanus), the number of platforms within 5 km (Blue Runner Caranx crysos, Crevalle Jack Caranx hippos), and dissolved oxygen concentration (Red Snapper). Significant predictors for vertical distribution included temperature (for Atlantic Spadefish Chaetodipterus faber, Bermuda Chub, Blue Runner, Greater Amberjack, Red Snapper), salinity (Greater Amberjack, Red Snapper), dissolved oxygen concentration (Red Snapper), and seafloor depth (Red Snapper). However, the majority of the study species were not influenced by the predictors included in the horizontal (11 of 17 species) and vertical distribution (12 of 17 species) generalized additive mixed models. Thus, many GOM fishes were found to associate with platforms over a relatively wide range of environmental conditions and platform characteristics. This suggests specific environmental conditions and distinct platform characteristics may not be as important as the simple number of available platforms for determining the distributions of many platform-associated fishes in the GOM.

In engineering practice, longitudinal brace systems for column-braced systems are designed to resist both horizontal and vertical loads. In previous experimental research on horizontal brace forces for column-braced systems of intermediate height, only vertical loads were considered. Hence, this paper presents a numerical simulation of numerous column-braced systems subjected to horizontal and vertical loads. In the numerical simulation, second-order analysis was adopted, and the Monte Carlo method was used to incorporate the randomness of initial imperfections in the horizontal brace and column. From the finite element (FE) analyses and probability model statistics, the normal probability density equation for intermediate-height horizontal brace forces under horizontal and vertical loads was obtained, and the corresponding design intermediate-height horizontal brace forces were determined and compared with those under vertical loads only. The results indicate that the design intermediate-height horizontal brace forces under horizontal and vertical loads are significantly greater than those under only vertical loads, and that the design intermediate-height horizontal brace forces under horizontal and vertical loads are also greater than the simple superposition results of horizontal loads and intermediate-height horizontal brace forces under only vertical loads.

Sequential resuspension of biofilm components (viruses, prokaryotes and protists) as measured by erodimetry experiments in the Brouage mudflat (French Atlantic coast)

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 404:227-240 (2010) - DOI: https://doi.org/10.3354/meps08431 Horizontal and vertical distribution of larvae of Pacific bluefin tuna Thunnus orientalis in patches entrained in mesoscale eddies Keisuke Satoh* National Research Institute of Far Seas Fisheries, 5-7-1 Orido, Shimizu-ku, Shizuoka City, Shizuoka 424-8633, Japan *Email: kstu21@fra.affrc.go.jp ABSTRACT: Nine high density larval populations (patches) of Pacific bluefin tuna Thunnus orientalis were detected and 7 patches were tracked with reference buoys for 28 to 171 h in the northwestern Pacific Ocean in May–June 2004 to 2008. Buoy trajectories and surface current velocities and directions measured by acoustic Doppler current profiler data showed close agreement. Growth rates for the sampled larvae (3.0 to 9.9 mm standard length [SL], 4 to 17 d after hatch), estimated by the daily modes of SL, correspond to growth rates estimated from otolith daily ring analysis. These results indicate that the same populations were sampled by tracking the buoy on almost all the sampling days. At fine- (100s of m to km) and mid-scale observations (~15 to 30 km range), patches consisted of a number of cohorts which had different distributions within the patch. The larval spatial structure was studied using variograms. At the fine scale, age-specific sills, ranges and spatial dependence of patches were similar; at the mid scale, these indexes showed stability during the trackings. Horizontally, larvae formed patches within an approximate 10 km range and advected together during the larval stage. Larvae were only distributed in the mixed layer and diel vertical movement was not clearly observed. Patches were entrained in mesoscale eddies (~100 to 500 km diameter) which propagated westward. Such mesoscale eddies are known to coalesce with the Kuroshio current. The spawning area and the recruitment fishing grounds are thereby linked by the Kuroshio. Results suggest that cohorts have a stable spatial structure after fertilization (i.e. during advection, while entrained in mesoscale eddies). Therefore, the positional relationship between spawning events and mesoscale eddies is concluded to be important for the recruitment process. KEY WORDS: Stability of spatial structure · Horizontal distribution · Vertical distribution · Mesoscale eddy · Kuroshio · Larval patch · Thunnus orientalis · Northwestern Pacific Ocean Full text in pdf format Supplementary material PreviousNextCite this article as: Satoh K (2010) Horizontal and vertical distribution of larvae of Pacific bluefin tuna Thunnus orientalis in patches entrained in mesoscale eddies. Mar Ecol Prog Ser 404:227-240. https://doi.org/10.3354/meps08431Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 404. Online publication date: April 08, 2010 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2010 Inter-Research.

Larger-diameter open-ended pipe piles are widely used as foundation for offshore structures. The lack of high-quality inner wall axial stress measurement results in difficulties in loading analysis of open-ended pipe piles during penetration and service period due to the effect of soil plugging. In this paper, two groups of model tests to assess the feasibility of bare fiber Bragg grating (FBG) sensing technology in monitoring the inner wall axial stress profile of open-ended aluminous pipe piles during penetration and horizontal loading are presented. One open-ended aluminous pipe pile was instrumented with bare FBG sensors and then penetrated into the sand bed with the rate of 20 and 30 mm/min, respectively. Two horizontal static loading tests were also conducted after 24-h penetration. The installation process of bare FBG sensors along open-ended aluminous pipe pile is introduced. The distribution profiles of axial stress and unit shaft resistance on inner wall and outer wall along model pile is discussed in detail. Model test results indicated that the bare FBG sensing technology was feasible to measure the axial stress of inner wall along open-ended pipe piles during penetration and horizontal loading in sand. During horizontal loading, the average values of qso/qsi are 0.717 and 0.727, respectively, for model pile with penetration rate of 20 and 30 mm/min. The axial stress difference of inner wall and outer wall along model pile in penetration and horizontal loading is the result of a combination of the inside and outside soil friction as well as of the pipe in-wall shear stiffness.

Limit load space of rigid strip footing on sand slope subjected to combined eccentric and inclined loading

Swiss needle cast (SNC) causes premature loss of foliage and subsequent growth decline in Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco). Although the mechanisms leading to this growth decline include loss of photosynthetic surface area and physiological disruption of surviving foliage, estimating the relative contribution of these two primary sources requires precise quantification of SNC effects on total foliage mass, foliage age-class structure, and vertical foliage distribution. The effect of SNC severity on these crown structural attributes was tested across a range of stand densities and site qualities in 10- to 60-year-old plantations in north coastal Oregon. Foliage mass in each age-class was sampled at the branch level, and the resulting equations were applied to all live branches on intensively measured sample trees. Vertical distribution of each foliage age-class was described by a beta distribution fitted to each sample tree, and sources of variation in vertical distribution were tested by regressing beta parameter estimates on SNC intensity and other covariates representing tree, stand, and site attributes. Distribution of foliage mass by age-class and by relative height in the crown was significantly affected by SNC severity, in addition to other covariates such as crown size and tree social position. SNC caused a reduction in the amount of foliage in each age-class and greater relative representation of younger needles. SNC also shifted the mode of relative vertical distribution toward the top of the tree for the three youngest foliage age-classes, but toward the base of the crown for 4- and 5-year-old foliage. Quantification of foliage age-class structure and vertical distribution across a range of SNC severity has helped to establish diagnostic criteria for assessing changes in crown structure that precede declines in growth and vigor. The induced changes in crown structure will also help to identify the relative contribution of several mechanisms causing growth losses in diseased trees.

To study the bearing characteristics of rock-socketed single piles on the southeast coast of Fujian Province, we conducted similar material ratio tests and single pile model tests. Initially, based on the mechanical parameters of strongly weathered granite, 10 groups of similar material samples were prepared using iron concentrate powder, barite powder, and quartz sand as aggregates, with rosin and alcohol as the cementing agents and gypsum as the modulating agent. Through triaxial testing and range and variance analysis, it was determined that the binder concentration has the most significant impact on the material properties. Consequently, Specimen 1 was selected as the simulation material. In the model test, the strongly weathered granite stratum was simulated using the ratio of Specimen 1. A horizontal load was applied using a pulley weight system, and the displacement at the top of the pile was measured with a laser displacement meter, resulting in a horizontal load-displacement curve. The results indicated that the pile foundation remained in an elastic state until a displacement of 2.5 mm. Measurements of the horizontal displacement and bending moment of the pile revealed that the model pile behaves as a flexible pile; the bending moment initially increases along the pile length and then decreases, approaching zero at the pile's bottom. The vertical load test analyzed the relationship between vertical load and settlement of the single pile, as well as its variation patterns. This study provides an experimental basis for the design of single pile foundations in weathered granite formations on the southeast coast of Fujian Province and aids in optimizing offshore wind power engineering practices.

Measurements of vertical and horizontal distributions of ozone over Beijing from 2007 to 2010

Comparative analysis of moisture-dependent physical and mechanical properties of two varieties of African star apple (Chrysophyllum albidum) seeds relevant in engineering design