| 51. |
- Al-Gburi, Majid
(författare)
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Restraint Effects in Early Age Concrete Structures
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- One of the widespread issues in concrete structures is cracks occurring at early age. Cracks that appear in the young concrete may cause early start of corrosion of rebars or early penetration of harmful liquids or gases into the concrete body. These situations could result in reduced service life and in significantly increased maintenance cost of structures. Therefore it is important for construction companies to avoid these cracks.Volumetric deformations in early age concrete are caused by changes in temperature and/or the moisture state. If such movements are restrained, stresses will occur. If the tensile stresses are high enough, there will be a damage failure in tension and visible cracks arise. These stresses are always resulting from a self-balancing of forces, either within the young concrete bodyalone, i.e. without structural joints to other structures, or from the young concrete in combination with adjacent structures through structural joints.The decisive situation within a young concrete body alone is typically high stresses at the surface when the temperature is near the peak temperature within the body. This situation occur rather early for ordinary structures, say within a few days after casting for structures up to about some meters thickness, but for very massive structures like large concrete dams, it might take months and even years to reach the maximum tensile stresses at the surface. Usually this type of cracks is denoted "surface cracks", and in some cases only a temperature calculation may give a good perception to make decisions of the risk of surface cracking.On the other hand, the decisive situation within a young concrete body connected to adjacent structures, might include both risk of surface cracking at some distance away from the structural joint and risk of through cracking starting in the neighborhood of the structural joint. If the young concrete body is small in accordance to the adjacent structure, or, in other words, if thereis an overall high restraint situation in the young concrete, the risk of early surface cracking might be out of question. So, restraint from adjacent structures represents one of the main sources of thermal and shrinkage stresses in a young concrete body.This study is mainly concentrated on establishing the restraint inside the young concrete body counteracted by adjacent structures, and how to estimate the risk of through cracking based on such restraint distributions. The restraint values in the young concrete are calculated with use of the finite element method, FEM. Any spatial structure may be analyzed with respect to the level of restraint. Calculations of risk of cracking are demonstrated with use of existing compensation plane methods, and a novel method denoted equivalent restraint method, ERM, is developed for the use of restraint curves. ERM enables the use of both heating ofthe adjacent structure and/or cooling of the young concrete, which are the most common measures used on site to reduce the risk of early cracking.In a design situation many parameters are to be considered, like type of cement, different concrete mixes, temperature in the fresh concrete, surrounding temperatures, temperature in the adjacent structure, measures on site (heating/cooling/insulation), sequence order of casting.Therefore, in general a lot of estimations concerning risks of cracking are to be performed. The main objective with the present study is to develop methods speeding up and shorten the design process.Furthermore, established restraint curves have been applied to the method of artificial neural networks (ANN) to model restraint in the slab, wall, and roof for the typical structure Tunnel. It has been shown that ANN is capable of modeling the restraint with good accuracy. The usage of the neural network has been demonstrated to give a clear picture of the relative importance of the input parameters. Further, results from the neural network can be represented by a series of basic weight and response functions, which enables that the restraint curves easily can be made available to any engineer without use of complicated software.A new casting technique is proposed to reduce restraint in the newly cast concrete with a new arrangement of the structural joint to the existing old concrete. The proposed technique is valid for the typical structure wall-on-slab using one structural joint. This casting method means that the lower part of the wall is cast together with the slab, and that part is called a kicker. It hasbeen proven by the beam theory and demonstrated by numerical calculations that there is a clear reduction in the restraint from the slab to the wall using kickers.Restraint is affected by casting sequence as well as boundary conditions and joint position between old and new concrete elements. This study discusses the influence of different possible casting sequences for the typical structure wall-on-slab and slab-on-ground. The aim is to identify the sequence with the lowest restraint to reduce the risk of cracking.
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| 52. |
- Al-Gburi, Majid, et al.
(författare)
-
Using Artificial Neural Network to Predict the Restraint in Concrete Culvert at Early Age
- 2015
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Ingår i: Structural Engineering International. - 1016-8664 .- 1683-0350. ; 25:3, s. 258-265
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Tidskriftsartikel (refereegranskat)abstract
- Estimation of restraint is very important for accurate prediction of the risk of concrete cracking at early age. The present study predicts the restraint in 324 walls and 972 roofs for a concrete culvert. A parametric study included the thickness and width of the roofs, thickness and height of the walls, thickness and width of the slab, and length of the structures. Each parameter increased or decreased the restraint in the walls and the roofs. The calculation of the restraint was done elastically by the finite-element method (FE). The results were used by an artificial neural network (ANN) tool, where firstly an influential percentage was investigated as input parameters on the restraint prediction. Equations have been derived by the ANN model to calculate the restraint in the walls and the roofs. It was then used in an Excel sheet to calculate the restraint and compare the result with the result from the finite-element calculations giving high accuracy between the ANN model and the FE calculations
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| 53. |
- Al-Rubaei, Ahmed, et al.
(författare)
-
Long-term hydraulic performance of stormwater infiltration systems
- 2015
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Ingår i: Urban Water Journal. - 1573-062X. ; 12:8, s. 660-671
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Tidskriftsartikel (refereegranskat)abstract
- Despite the common use of stormwater infiltration systems, there is still only limited data available evaluating the long-term hydraulic function of such systems. The hydraulic performance of twelve stormwater infiltration systems (vegetated and unvegetated concrete grid pavers, unvegetated interlocking concrete pavers and grassed swales) was therefore investigated in field and laboratory environments in Växjö, Sweden. The systems investigated had not been subjected to regular maintenance to sustain infiltration capacity. Due to this, and the fact that, for most systems, an inappropriate joint filling material was used and (at the swales) there was severe compaction, most systems showed a reduced infiltration capacity. Despite this, especially the older vegetated systems, were still capable of infiltrating intense design rainfalls. This study showed the influence of some factors (type and age of the system, the type of joint filling material (grass and macadam) and the distance from the edge of the pavement) on the long-term behaviour of the infiltration capacity. In conclusion, there is a significant risk that existing stormwater infiltration systems are not working adequately in praxis. Proper implementation of construction and regular control by the inspecting authority has to be ensured.
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| 54. |
- Alanbari, Mohammad, et al.
(författare)
-
Application of SimaPro7 on Al-Hilla City Sewerage Network, Iraq
- 2015
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Ingår i: Engineering. - : Scientific Research Publishing, Inc.. - 1947-3931 .- 1947-394X. ; 7:5, s. 224-229
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Tidskriftsartikel (refereegranskat)abstract
- SimaPro is a software package designed to make a valuable contribution for analyzing the environmental impact on products during their whole life cycle. A huge amount of knowledge about the environment is built into the program and database, enabling to analyze a product with a minimum of specialized knowledge. In this study, SimaPro was used to analyze and evaluate the impacts that resulted from sewerage network in Al-Hilla city, Iraq. The results of Life Cycle Assessment (LCA) showed that sewerage network had an impact and damage on the environment by 291 points for every cubic meter of collect wastewater. The most potential environmental impacts were global warming, respiratory inorganics and non-renewable energy, contributing to the sewerage network. The study also showed that most of the effects were as a result of energy consumption in the pumping of wastewater, pipes used and diesel using for network operation.
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| 55. |
- Alanbari, Mohammad, et al.
(författare)
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Environmental Assessment of Al-Hilla City Wastewater Treatment Plants
- 2015
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Ingår i: Journal of Civil Engineering and Architecture. - : David Publishing Company. - 1934-7359 .- 1934-7367. ; 9:6, s. 749-755
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Tidskriftsartikel (refereegranskat)abstract
- Iraq is one of the countries that is suffering from water shortage problems and, for this reason, wastewater treatment plantsbecome a necessity to minimize this problem. In this study, the impact of Al-Hilla WWTP (wastewater treatment plant) on theenvironment has been studied. This was achieved using SimaPro software package. This software is a powerful tool for analyzing theenvironmental impact on products during their whole life cycle. A huge amount of knowledge about the environment is built into theprogram and database, enabling to analyze a product with a minimum of specialized knowledge. The results of LCA (life cycleassessment) showed that the impact and damage on the environment by Al-Hilla WWTP was 41 bad points for each 1 m3 of treatedwastewater. The most environmental impacts potentially were global warming, respiratory inorganics and non-renewable energy. Thestudy also showed that most of the effects were the result of the use of cement, steel and electricity consumption
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| 56. |
- Alanbari, Mohammad, et al.
(författare)
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Selecting sustainability indicators of urban water systems: Case study of al-Hilla city, Iraq
- 2015
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Ingår i: Journal of Environmental Hydrology. - 1058-3912 .- 1996-7918. ; 23
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Tidskriftsartikel (refereegranskat)abstract
- The present study used environmental criteria to appraise the sustainability of the urban water system(UWS) of Al-Hilla city, Iraq. The study focused on the assessment of the environmental impact anddamage to the urban water system. Environmental criteria of sustainability included a number ofindicators. These indicators were selected using tools of sustainability analysis, where life cycleassessment (LCA) was used to select and analyze the environmental indicators by applyingSimaPro7.1.8. LCA. The results for urban water system in Al-Hilla city showed that water treatmentplants (WTPs) and distribution network were most sustainable compared with sewerage network andwaste water treatment plants (WWTP). WTPs impact and damage on the environment and distributionnetwork was 4 and 11.5 points respectively, while Al-Hilla WWTP and sewerage network was 41 and291 points respectively, for delivery of one cubic meter of potable water at the point of consumption ortreatment of one cubic meter of wastewater. In addition, the study showed that most of the effects weredue to electricity consumption, pumping raw water and clean water, chemical use (such as chlorine),pipes used in water distribution and sewage collection networks, and diesel used for plant operation.
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| 57. |
- Alerby, Eva
(författare)
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A Picture Tells More than a Thousand Words
- 2015
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Ingår i: Children’s Images of Identity. - Rotterdam : Encyclopedia of Global Archaeology/Springer Verlag. - 9789463001243 ; , s. 15-25
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Bokkapitel (refereegranskat)abstract
- ‘A picture tells more than a thousand words’, is a common saying. Given that a picture tells more than a thousand words – how can we understand and use this expression? How can a picture, or an image, be analysed and used as part of educational research? In this chapter the use of images, and more specifically drawings, will be explored.
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| 58. |
- Alerby, Eva, et al.
(författare)
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Delaktighet för lärande
- 2015
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- De demokratiska värdena, elevernas delaktighet och inflytande, ska vara lika centralt i utbildningen som kunskaper i olika skolämnen. Det framgår tydligt i skollagen och läroplanerna.Denna kunskapsöversikt lyfter fram forskning som handlar om vad delaktighet och inflytande innebär och hur man kan arbeta med elevers inflytande över beslutsprocesser och elevaktiv undervisning.Kunskapsöversikten riktar sig i första hand till personal i grund- och gymnasieskolan och mot-svarande skolformer eller till dig som vill veta mer om elevdelaktighet och inflytande.
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| 59. |
- Alerby, Eva
(författare)
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Det pedagogiska rummet : Om erfarenheter, känslor och den rumsliga gestaltningen
- 2015
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Ingår i: Thule. - Umeå : Kungl. Skytteanska samfundet. - 9789186438562 ; , s. 69-78
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- A university is among other things a building with its own spatial formations. These spatial formations can create expectations and be experienced as inspiring; they can create opportunities but also limitations. What then conveys the experience of these places? Based on the research study Places of a University, but also on previous studies about places of education, the overall aim of this article is to problematize and discuss the educational room. More specifically, I discuss how earlier experiences influence present experiences of educational rooms, but also the intertwined relationship between emotions and the spatial formations of a university. Student reflections exemplify the reasoning in the article.
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| 60. |
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