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Bearing Capacity Investigation of Silty Sandy Soil Layer Using Kunzelstab Test

Abstract

This study presents the effect of the 3 apex angles of cone and water levels on the bearing capacity of silty sandy soil (SM) layer by interpreting results from Kunzelstab test. The SM soil layer was prepared in the testing tank and it was used as the representative of sandy soil for some area in Thailand. As the results, the cone angle increase, a number of blows increase and the adjusted factors of the blows from the apex angles of 60° and 180 º to be that of the apex angle of 90º (control) were 1.118 and 0.878, respectively. The obtained correlation between the blows and the internal friction angles of SM soil can be used for calculating the soil bearing capacity which lowers the ground surface of 0.6 m. The soil bearing capacity of SM soil below ground water level decreases 70 to 75 percent (average values from testing results) comparing to that of dry soil. Moreover, the bearing capacity of SM soil above the water level up to 0.6 m decreases 25 to 30 percent (average values from testing results) comparing to that of dry soil at the same depth. Silty sandy soil layer was found determined to have lower bearing capacity due to higher ground water level. Therefore, the calculation of the soil bearing capacity in silty sandy soil layer should be considered the effect of ground water level.

Open access
Behavior of Beam-to-Column Connections with Angles. Part 2-Numerical Analysis

Abstract

Based on the results of experimental tests, presented in the first part of this paper, Part 1-Experimental Investigations (Ghindea M., Catarig A., Ballok R.) advanced numerical simulations were performed using FEM based software Abaqus. The recently arise of high speed computers and advanced FEM software packages allow to create and solve extensively detailed 3D models. The aim of this second part of the paper is to develop accurate FEM models for better approach of the studied beam-to-column connections. The paper presents the designed numerical models and the results for four bolted beam-to-column connections using top-and-seat and/or web angle cleats, in different configurations. The objective of this paper is to achieve functional numerical models which, by faithfully running, reproduce the experimental results. Thus, calibrating the numerical results with the experimental ones it can be perform then parametric studies, achieving reliable results for similar configurations of joints. The results obtained after numerical simulations were compared with experimental data. The behavior moment-rotation curve and the deformation process of the experimental captured specimens were virtually reproduced with minimum deviation.

Open access
Finite Element Analysis of Hollow-Core Slabs

Abstract

The use of high resistance materials in nowadays structures has led to an increase in the span of the floors. Despite meeting the resistance and deformation criteria, floors might vibrate excessively due to increased slenderness. Based on a real-scale model experimental program, a parametric study has been developed in order to asses the vibration performance of prestressed hollow-core slab system on spans larger than the ones on which tests have been conducted, and the interaction between the concrete that have been poured in different stages. The measurements have been performed using Brüel and Kjӕr equipment, whereas the study has been carried out using Abaqus 6.11. finite element software. The simulations have been made by increasing the span of the slab, in order to observe the variation of the fundamental frequency. Also, the simulations have been conducted with different types of concrete topping thickness. The minimum acceptable value of the fundamental frequency has been considered 8Hz, according to existing literature.

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Geometric Non-Linear Approach to Stiffness State of Semi–Rigid Structures

Abstract

Present contribution intends to emphasize the contribution of geometric non-linearity to the stiffness state of semi-rigid multi–storey steel structures. Though semi-rigidity of beam – column connections involves a nonlinearity at constitutive bending momentrelative rotation level, the geometric nonlinearity associated to deformed conFigure uration at element level is less referred to. The main objective of the study is to express the stiffness state of geometric non-linear elements semi-rigidly connected at its ends. Stiffness state is, in its term, expressed by element level stiffness matrix considering the six degrees of freedom of the planar element. Regarding the reference system, both local and global systems are employed allowing a simple and direct transition from element level vectorial relations to their structural level forms. The three fundamental vectorial relations (static equilibrium, kinematic compatibility, material constitutivity) emphasize that the principle of virtual work holds in the case of semi-rigidly connected skeletal structures as well.

Open access
Importance of Results Obtained from Geotechnical Monitoring for Evaluation of Reinforced Soil Structure – Case Study

Abstract

In the case of realized geotechnical monitoring (GTM) of reinforced retaining wall in difficult geological conditions is demonstrated the important role at realisation of transport infrastructures, which are often realized in insufficient quality due to inappropriate geotechnical parameters from survey works or not fitted well design of structure at certain conditions. This can result in large deformations of structure, or losing stability or structure life-time is very limited and remediation work is complicated and expensive. There was built on the modernized railway line Bratislava – Trenčín, closed to Zlatovce, overpass and connected road embankments on the route of first class I/61. Structure was designed as a bridge over the railway track before the northern portal of the railway tunnel Turecký vrch was open. A part of the embankment and overpass was a retaining wall reinforced by geosynthetics. The results of the geotechnical monitoring of this wall were afterwards simulated using finite element method (FEM) and results of this comparison are the scope of this article.

Open access
Influence of end Contsrains on the Global Behaviour of a Box Girder

Abstract

This study aims to presents the importance of end constrains, boundary conditions and position of the applied forces regarding the design of precast/prestressed concrete box girders. The study is based on a destructive test which was performed on a 37.1 m span single-cell prestressed concrete box girder. The scope of the test was to certify the usage of such girders for the new Transylvania motorway bridges. The test is numerically reproduced through a full 3D FEM model implemented in SAP2000. The influence of the end diaphragms is considered by analysing the beam’s behaviour to six loading conditions: one of which is replicating the loadings during the test, while the others are conceived as real vertical and horizontally loading scenarios. The results obtained for the girders with and without end constrains are compared. The performances of both design solutions in the presence of prestressing are highlighted where applicable. It is considered that the results of this study may provide very important data if considering that Romania has an urgent need to realize a modern and an adequate transport infrastructure.

Open access
The Influence of Zenith Tropospheric Delay on PPP-RTK

Abstract

The PPP technique is more and more used in different GPS precise application. The PPP precision is related to many factors and the most important are: the number of satellites, the ambiguity resolution, the ability to model the ionospheric and tropospheric delays, solid earth and ocean tides, relativistic effects and antenna phase-center offsets and variations. The article is studying the effect of the zenith tropospheric delay (ZTD) using the GPT2 model and then computing in static mode the ZTD, which is than applied on PPP-RTK method. An analysis on dual frequency ionospheric–free phase combination (LC) and dual frequency ionospheric–free range combination (PC) was made in the first stage and then comparing the two solutions relative to the nominal position. The results revealed the fact that by using the ZTD determined in static mode in the detriment of ZTD from GPT2 model, the results are improving on North, East and Up position components. Also lower RMS was obtain when we used the ZTD from static mode comparative to the GPT2 model.

Open access
Mitigating Ventilation Air Methane Cost-Effectively from a Colliery in Australia

Abstract

Methane has been controlled in collieries in the past only for safety and statutory compliance reasons; however concerns over greenhouse gas emissions mean that this is now changing. About 65% of greenhouse emissions associated with underground coal mining come from ventilation air methane (VAM). The machinery to mitigate these fugitive emissions once the VAM exits the mine fans is expensive, has safety concerns and is not widely used at present. Consider these factors; more collieries are mining lower seams, methane content increases with depth, VAM mitigation plants are not widely used, most mine emissions are VAM, and widespread concern over greenhouse gases mean that it is desirable to lower VAM emissions now. One solution would be a method to prevent more methane from entering the mine airstream and becoming VAM in the first place. Recently, in a colliery in the Hunter Valley, this mitigation method underwent a 12-month trial, and involved six different measures. Measurements were taken to assess the emissions mitigation which was achieved, and the cost of the works; all the results are detailed herein. A reduction in fugitive emissions of 80,307 t/CO2-e below that which was projected for the next 12-month period was quantified, at an average cost of A$1.28c t/CO2-e. The mitigation measure outlined here represent a first attempt to the author’s knowledge, in an operating mine, to lower a collieries’ environmental footprint by preventing methane from entering the mine airstream and becoming VAM gas by the deliberate use of mitigation measures.

Open access
Steady-State Three - Dimensional Numerical Simulation of Heat Transfer for Thermal Bridges Assessment

Abstract

This paper presents a study on using the steady-state three-dimensional heat transfer software HEAT3 for evaluating the heat flow of heat transfer through different elements of the building envelope in order to establish the linear thermal transmittance of the linear thermal bridge. The linear thermal transmittance is obtained according to the one-dimensional steady-state heat transfer calculation formula for the plane walls using the heat flow values obtained through the method specified above. The results presented in this paper are part of a wider study on evaluating the heat transfer through building’s envelope elements by evaluating as accurate as possible the thermal bridges effect of the most common building structures. As a case study, it was considered the steady-state heat transfer through an opaque outer wall of a building considering the thermal bridges for the following elements: outer walls intersection, inner and outer wall intersection and outer wall with intermediate floor intersection.

Open access
Use Effects on the Reflection of Macro Textured Surfaces

Abstract

The emergence of led luminaries in street lighting has modified traditional design guidelines. The highest led energy efficiency allows keeping suitable lighting levels with less installed power. Thus, the present design line of a street lighting installation is closely related to the technological change: kind of led to be used, suitable lens, efficacy relationship regarding high pressure sodium, light colour temperature, spectrum. The “impact” associated to with led conversion relegates main aspects of street designs: effect of road reflective properties and installation depreciation. The wear produced by traffic, as well as the environmental conditions gradually modifies the road reflection matrix. In a street lighting installation, this change alters the luminance arrangement on the road together with the perception conditions. This phenomenon is a determining factor within the global concept of depreciation affecting lighting systems in general and also street lighting installations designed by the Luminance Technique. In the present work changes, due to use, in the shape of street reflection matrices of Argentinean highways are analyzed. The analyzed r-tables were obtained through “in-situ” measurements, with road reflectometer. A first group corresponds to the initial conditions of macro textured roads which were measured in the period 2001/2003. The second studied set contains r-tables of the same type, and according to its use the surfaces can be considered in steady state, assessed between 2005 and 2009. The study provides information about the shape of matrixes and its alteration, specularity and scale factor, relating such parameters with the possible effects on the resulting lighting.

Open access