Assessment of AASHTO Load-Spreading Method for Buried Culverts and Proposed Improvement

2021 ◽  
pp. 036119812110215
Author(s):  
Michael G. Katona
Keyword(s):  
Ad Hoc ◽  
Soil Depth ◽  
Free Field ◽  
Peak Stress ◽  
Element Model ◽  
Surface Load ◽  
Accuracy Evaluation ◽  
Simple Modification ◽  
Homogeneous Half Space ◽  
Order Of Magnitude

AASHTO’s ad hoc method (AAM) for predicting free-field soil stress under a rectangular loading area is a simple and very useful tool for the analysis of buried culverts subject to vehicular wheel loads. AAM assumes the surface load spreads with soil depth into an ever-increasing rectangular area whose dimensions are controlled by a constant spread angle θ usually taken as 30°, denoted as AAM-30°. Both simplified and comprehensive culvert analysis procedures utilize AAM predictions for adjusting pressure distributions acting on the culvert periphery. Also, AAM-30° is routinely used to determine the two-wheel soil interaction depth, in which the combined effect of both axial wheels need to be considered. To date, a thorough accuracy analysis of AAM-30° has not been published in the open literature. This paper provides a unique and rigorous evaluation of AAM-30° using an exact solution from an elasticity-based model (EBM) of a homogeneous half-space with rectangular surface load. One key discovery is the depth parameter called y*, which is the soil depth at which AAM-30° peak-stress prediction exactly matches the exact EBM solution. Moreover, it is shown that y* may be determined by a simple, yet accurate formula that only depends on the square root of the load area. However, the investigation reveals that AAM-30° significantly underestimates peak stress in the shallow-depth zone 0 <  y < ½ y* by as much as 31.3% of the applied surface pressure. As this is a large nonconservative error it cannot be ignored. Accordingly, a very simple modification is introduced called AAM-θ*, in which θ* is a spread angle that linearly increases to 30° at soil depth ½ y* and thereafter θ* remains constant at 30°. An accuracy evaluation of AAM-θ* reveals an order of magnitude increase in accuracy in which the small residual error is conservative, not nonconservative. The paper concludes with discussions on applying AAM-θ* to the analysis of buried culverts when using either simple or finite element model solution procedures.

MODELING OF THE STRESS-STRAIN STATE OF A TRANSPORT TUNNEL UNDER LOAD AS A MEASURE TO REDUCE OPERATIONAL RISKS TO TRANSPORTATION FACILITIES

2020 ◽  
Vol 3 (8) ◽  
pp. 28-34
Author(s):  
N. V. IVANITSKAYA ◽  
◽  
A. K. BAYBULOV ◽  
M. V. SAFRONCHUK ◽  
◽  
...  
Keyword(s):  
Strain State ◽  
Moving Load ◽  
Element Model ◽  
Transport Infrastructure ◽  
Design Stage ◽  
Surface Load ◽  
Stress Strain ◽  
Stress Strain State ◽  
Operational Risks ◽  
Von Mises

In many countries economic policy has been paying increasing attention to the modernization and development of transport infrastructure as a measure of macroeconomic stimulation. Tunnels as an important component of transport infrastructure save a lot of logistical costs. It stimulates increasing freight and passenger traffic as well as the risks of the consequences of unforeseen overloads. The objective of the paper is to suggest the way to reduce operational risks of unforeseen moving load by modeling of the stress-strain state of a transport tunnel under growing load for different conditions and geophysical parameters. The article presents the results of a study of the stress-strain state (SSS) of a transport tunnel exposed to a mobile surface load. Numerical experiments carried out in the ANSYS software package made it possible to obtain diagrams showing the distribution of equivalent stresses (von Mises – stresses) according to the finite element model of the tunnel. The research results give grounds to assert that from external factors the stress state of the tunnel is mainly influenced by the distance to the moving load. The results obtained make it possible to predict in advance the parameters of the stress-strain state in the near-contour area of the tunnel and use the results in the subsequent design of underground facilities, as well as to increase their reliability and operational safety. This investigation gives an opportunity not only to reduce operational risks at the design stage, but to choose an optimal balance between investigation costs and benefits of safety usage period prolongation.

Research of the Connecting Form about the Spherical Shell and the Nozzle

2011 ◽  
Vol 413 ◽  
pp. 520-523
Author(s):  
Cai Xia Luo
Keyword(s):  
Finite Element ◽  
Stress Distribution ◽  
Finite Element Model ◽  
Spherical Shell ◽  
Maximum Stress ◽  
Peak Stress ◽  
Element Model ◽  
Small Opening ◽  
Large Opening ◽  
Reducing Stress

The Stress Distribution in the Connection of the Spherical Shell and the Opening Nozzle Is Very Complex. Sharp-Angled Transition and Round Transition Are Used Respectively in the Connection in the Light of the Spherical Shell with the Small Opening and the Large One. the Influence of the Two Connecting Forms on Stress Distribution Is Analyzed by Establishing Finite Element Model and Solving it. the Result Shows there Is Obvious Stress Concentration in the Connection. Round Transition Can Reduce the Maximum Stress in Comparison with Sharp-Angled Transition in both Cases of the Small Opening and the Large Opening, Mainly Reducing the Bending Stress and the Peak Stress, but Not the Membrane Stress. the Effect of Round Transition on Reducing Stress Was Not Significant. so Sharp-Angled Transition Should Be Adopted in the Connection when a Finite Element Model Is Built for Simplification in the Future.

scholarly journals Effects of vegetation and soil on evapotranspiration, flow regime, and basin storage in three nearby catchments in northeast Japan

2016 ◽  
Author(s):  
Shoji Noguchi ◽  
Tomonori Kaneko ◽  
Shin'ichi Iida ◽  
Wataru Murakami ◽  
Takanori Shimizu
Keyword(s):  
Flow Regime ◽  
Cryptomeria Japonica ◽  
Soil Depth ◽  
Forested Catchments ◽  
Sapwood Area ◽  
Stand Volume ◽  
Breast Height ◽  
Soil Storage ◽  
Order Of Magnitude ◽  
Soil Measurements

Abstract. Vegetation and soil determine evapotranspiration, flow regime, and basin storage in forested catchments. We conducted hydrological observations at three nearby catchments (catchments nos. 1, 2, and 3) in the Nagasaka experimental watershed located on the green tuff region in northeast Japan. Diameter-at-breast height (DBH) of all trees > 3 cm DBH was recorded. In addition, we measured soil depth at 170 locations and investigated 45 soil pits. Based on these detailed vegetation and soil measurements, we examined evapotranspiration, flow regime, and basin storage during the no-snow-cover period (May–November). More than 80.9 % of stands in the catchment were comprised of Cryptomeria japonica. Stand volume (122.0 m3 ha−1) and sapwood area (10.7 m2 ha−1) in catchment no. 3 were smaller than those in the other two catchments (no. 1: 255.7 m3 ha−1; 16.0 m2 ha−1, no. 2: 216.5 m3 ha−1; 14.2 m2 ha−1). Consequently, evapotranspiration was lower in catchment no. 3 than that in catchments nos. 1 and no. 2. In addition, low and scanty runoffs in catchment no. 3 were larger than those in nos. 1 and 2. The order of magnitude for soil storage was catchments no. 1 (104.2 mm) 

Study on Mechanical Behavior of Plastic Pipe Reinforced Cross-Winding Steel Wire Subjected to Non-Axis Line Symmetric Surface Load on Soil

2015 ◽  
Vol 750 ◽  
pp. 251-260
Author(s):  
Xiang Li ◽  
Wei Feng Li ◽  
Liu Yun Xu
Keyword(s):  
Mechanical Behavior ◽  
Steel Wire ◽  
Element Model ◽  
Surface Load ◽  
Plastic Pipe ◽  
Steel Composite ◽  
Plastic Matrix ◽  
Symmetric Surface ◽  
Symmetric Load ◽  
Good Agreement

Plastic pipe reinforced by cross helically wound steel wires (PSP) is a new plastic-matrix steel composite pipe developed in China recently. To deeply understand the mechanical properties of buried PSPs, a finite element model of PSP subjected to non-axis symmetric load is proposed. The model is verified by replacing the parameters of PSP by those of steel pipe. A good agreement shows that the model can be used to analyze mechanical behavior of buried PSP. Finally, the influences of internal pressure, properties of soil, geometry parameters of PSP and magnitude of load, etc. are discussed.

SEISMIC DECOUPLING FOR EXPLOSIONS IN SPHERICAL UNDERGROUND CAVITIES

Geophysics ◽  
1961 ◽  
Vol 26 (6) ◽  
pp. 772-799 ◽  
Author(s):  
William M. Adams ◽  
DeWitt C. Allen
Keyword(s):  
Spherical Cavity ◽  
Seismic Waves ◽  
Free Field ◽  
Salt Mine ◽  
Cavity Pressure ◽  
Frequency Range ◽  
Overburden Pressure ◽  
Underground Cavities ◽  
Order Of Magnitude ◽  
Surface Measurements

A series of paired explosions in a salt mine near Winnfield, Louisiana, has been conducted to test a theory by A. L. Latter concerning seismic decoupling by underground cavities. The theory predicted a decoupling of 130. Free‐field and surface measurements from an explosion in either a 6‐ft‐ or a 15‐ft‐radius spherical cavity were compared with similar measurements from a completely tamped explosion of equal size. Shot sizes were from 20 pounds to a ton. Surface measurements were made out to 100 km and covered the frequency range from 0.05 to 100 cps. The experiment confirmed that decoupling does occur. For explosions that produce an average cavity pressure up to one‐fifth and possibly more of the lithostatic overburden pressure, seismic waves were decoupled by more than 100, i.e., two orders of magnitude. Even for explosions producing an average cavity pressure of six times the lithostatic overburden pressure, the seismic waves were decoupled by 20—more than a full order of magnitude. Minimum decoupling factors as a function of frequency are presented.

Application of Extenics Theory to Accuracy Evaluation of Machining Center

2013 ◽  
Vol 397-400 ◽  
pp. 135-139
Author(s):  
Chen Liu ◽  
Xiang Li Bu
Keyword(s):  
Set Theory ◽  
Element Model ◽  
Accuracy Evaluation ◽  
Practical Application ◽  
Analytic Hierarchy ◽  
Evaluation Indexes ◽  
Machining Center ◽  
Relational Degree ◽  
Matter Element Model ◽  
Hierarchy Process

The matter-element model for the accuracy evaluation of the machining center is established based on extenics theory, the accuracy evaluation indexes of machining cente are made of multiple elements. The relational degree is calculated by introducing the relational function in the extension set theory, and the weights of evaluation indexes are defined with AHP (the analytic hierarchy process), so the awaiting evaluation machining center is determined though the accuracy grade. A type of machining center as an example is studied the practical application of the proposed method, the result is reasonable and shows that the method possesses a certain practicability.

SENSITIVITY OF DYNAMIC BEHAVIOUR OF THE FE MODEL: CASE STUDY FOR THE IGNALINA NPP REACTOR BUILDING

2008 ◽  
Vol 14 (2) ◽  
pp. 121-129 ◽  
Author(s):  
Romualdas Baušys ◽  
Gintautas Dundulis ◽  
Rimantas Kačianauskas ◽  
Darius Markauskas ◽  
Sigitas Rimkevičius ◽  
...  
Keyword(s):  
Dynamic Behaviour ◽  
Free Field ◽  
Response Spectra ◽  
Element Model ◽  
Sensitivity Study ◽  
Fe Model ◽  
Model Case ◽  
Global Dynamic ◽  
Wall Stiffness ◽  
Reactor Building

The 3D thin‐walled finite element model of Ignalina NPP Unit 2 reactor building was developed aimed at the evaluation of the global dynamic behaviour with a focus on the seismic response. The model comprises description of the monolithic structures, while prefabricated frame structures are ignored and replaced by external masses. Sensitivity study of the selected dynamic characteristics of the model with respect to data uncertainties is considered. Uncertainty of the model is considered in terms of masses of removed structures and wall stiffness. Seismic input is represented by the site specific free‐field ground response acceleration spectra. The sensitivity study concerns variations of frequencies and acceleration of in‐structure horizontal response spectra at specified points. Maximal bending moments are also considered. It was obtained that the reactor level is not sensitive to the uncertainties considered, while discernable sensitivity was detected at the top level of the structure. Santrauka Pateikta Ignalinos atominės elektrinės pastato erdvinio baigtinių elementų dinaminio modelio kūrimo koncepcija, išnagrinėtas šio modelio jautrumas keičiamoms masėms ir sienų standumui. Parodyta, kaip šie keičiami dydžiai turi įtaką dažniams, horizontaliems tam tikrų nagrinėjamų taškų atsako spektrams, lenkimo momentų persiskirstymui ir jų didžiui.

A Study on Motions and Connector Loads for a New Type of Two-Module Semi-Submersible

2019 ◽  
Author(s):  
Jun Ding ◽  
Chao Tian ◽  
Yuji Miao ◽  
Zhengwei Zhang ◽  
Zhanhua Zhao ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Element Model ◽  
Short Term ◽  
Term Forecast ◽  
Dimensional Finite Element ◽  
Order Of Magnitude ◽  
New Type ◽  
The Subject ◽  
Three Dimensional Finite Element ◽  
Marine Platform

Abstract The hydrodynamic model and three-dimensional finite element model of a new type of two-module marine platform were built for the subject of research. The motions and connector loads were predicted based on the COMPASS THAFTS software and the results were in agreement with the model tests. It shows that the new type platform has a good sea keeping performance. On the other hand, the short-term forecast results indicate that the connector loads, Fz, is larger than other two directions, approaching 200t. The connector loads, Fx and Fy, are usually in the order of magnitude of tens tons. Some useful conclusions obtained in this paper can provide an important reference for the optimal design and construction of the new type platform and its connector system.

Feasibility of segmented concrete in wind turbine tower: Numerical studies on its mechanical performance

2020 ◽  
pp. 105678952095489
Author(s):  
Yanchao Yue ◽  
Jingjing Tian ◽  
Qingyi Mu ◽  
Tangbing Chen ◽  
Lin Peng ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Mechanical Performance ◽  
Cost Savings ◽  
Peak Stress ◽  
Element Model ◽  
Numerical Studies ◽  
Wind Turbine Tower ◽  
Low Elastic Modulus ◽  
Tower Structure

Segmented concrete slices have been widely used in the construction of wind turbine tower due to easy transportation and cost savings. Factors such as the size and form of the concrete slice and the connector may affect the stiffness and reliability of the structure. The objective of this study is to investigate the influence of the above factors on mechanical performance of a wind turbine tower. A finite element model of 40 m segmented concrete tower was developed for the modal analysis, and a local refinement model was established for the static analysis. Results show that the slice form and connectors have impact on the rigidity of the tower structure. Dividing the tower into two pieces per layer, increasing the height of the tower segment, using the grout connection of the longitudinal and staggering longitudinal seams can increase the stiffness of segmented concrete tower. In addition, this study analyzes the role of rubber pads in improving the mechanical performance of the tower, results show that the peak stress at the joints can be reduced by setting rubber pads with low elastic modulus at the longitudinal seams.

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