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    Integrating Reused Steel Elements in Structural Design
    (2023) Karlsson, Maria; Gabrielsson , Linnéa; Chalmers tekniska högskola / Institutionen för arkitektur och samhällsbyggnadsteknik (ACE); Chalmers tekniska högskola / Institutionen för arkitektur och samhällsbyggnadsteknik (ACE); Fernandez, Ignasi; Sehlström, Alexander; Steinert, Axel
    The building industry is one of the world’s largest CO2 emitters, the need to transition into a circular economy is becoming increasingly pressing. Steel is a long-lasting and dimensionally stable material and therefore suitable for reuse. However, reuse of steel is not yet implemented on a large scale in the building industry and inventories of available elements are still limited. This thesis showcase how structural engineers can work with reused steel, by the mapping of workflows and suggesting of an semi-automated design process. The thesis is divided into four parts. In Part 1, a mapping of possible workflows is done through literature studies and informal interviews. In Part II, a digital workflow for integrating an inventory of reused elements into a structure is developed. This includes a parametric 3D model in Rhino/Grasshopper, structural analysis using FEM-Design, and a self-scripted tool in C# that performs Eurocode verification and matches reused elements to a structure using an A* optimization algorithm. The optimization objective is to minimise the embedded CO2 equivalents (CO2e) in the structure. In Part III, an iterative design process is carried out to test the digital workflow. Finally, Part IV presents reflections and discussions concerning the project. For the design process, a fictitious office building is designed and matched with two different inventories of reused elements using the developed workflow. One inventory is based on the available elements from the steel supplier Stena Stål, the other is based on a building to be dismantled. For the design process, an iterative approach is implemented. Initially, several rough sketches are created followed by continuous evaluation, selection and developments leading to an increasingly refined design. The developments include defining and applying design principles to reduce the vulnerability to changes of the inventory. They also include smaller design changes, guided by the tool, to further decrease the environmental impact. The result is a design proposal that exemplifies the potential of reused steel elements. The conclusion from the study is that structural engineers benefit from using automated workflows when designing with reused steel because the process is repetitive. Also, allowing reuse to influence design decisions can significantly increase the carbon savings of a project, as small design modifications can increase the reuse rate.
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    Imperfection Sensitivity of the Shear Behaviour of Corrugated Web Beams
    (2023) Khalili, Shahriar; Chalmers tekniska högskola / Institutionen för arkitektur och samhällsbyggnadsteknik (ACE); Chalmers tekniska högskola / Institutionen för arkitektur och samhällsbyggnadsteknik (ACE); Amani, Mozhdeh; Thrin, Christer
    This thesis investigates the imperfection sensitivity of the shear behavior of stainless steel beams with corrugated webs, with the main objective of verifying the shear resistance design equations in EN 1993-1-5. Firstly, a comprehensive literature study was conducted to acquire deeper knowledge on the subject and generate a database to verify the calculated reduction factor by the Eurocode equations. Afterward Finite Element Modeling analysis using ABAQUS was done to consider the imperfection sensitivity of the shear behavior of beams with different geometric parameters. 17 different parametric models of stainless steel corrugated web beams were considered to cover various slenderness ratios and simulations by using Python code were run. Nonlinear analysis for the mentioned models was performed while considering 20 buckling modes as patterns of the initial imperfection with different amplitudes of 𝑎𝑚𝑎𝑥/200 (𝑎𝑚𝑎𝑥 is the larger length between inclined and horizontal fold), 𝑡𝑤 (web thickness), and ℎ𝑤/200 (ℎ𝑤 is web height). Lastly, a discussion is conducted to evaluate the use of the Eurocode’s design equations for stainless steel beams.
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    Sustainability and thermal comfort of bamboo building technologies in the hot humid tropics: Linking mitigation and adaptation
    (2023) Ayala Laverde, David; Chalmers tekniska högskola / Institutionen för arkitektur och samhällsbyggnadsteknik (ACE); Chalmers tekniska högskola / Institutionen för arkitektur och samhällsbyggnadsteknik (ACE); Wallbaum, Holger; Goto, Yutaka
    The challenge of doubling the global building stock by 2070 has spurred interest in new building materials and technologies due to the critical environmental burdens associated with this growth. Affordable bamboo building technologies, potentially available in emerging and developing economies where most of the floor area growth is expected, emerge as an alternative. There is growing evidence that bamboo buildings outperform traditional materials in terms of global warming potential impacts. However, climate change's impact on thermal stress and the need for climate-adapted buildings require consideration of thermal comfort and energy needs. Bamboo buildings’ lightweight nature prompts exploration into whether it can offer thermal comfort while eliminating or reducing cooling energy requirements in hot tropical climates. This thesis addresses the link between building technology, thermal comfort, energy demands, and overall environmental impacts in the context of bamboo structures and non-residential buildings. The aim of the study is to test whether bamboo buildings can substantially mitigate environmental impact, offer thermal comfort while minimizing cooling energy needs, and continue to mitigate impacts when energy requirements for comfort are also considered. A case study building in the Philippines implementing bamboo trusses and composite-bamboo shear walls for a 149 m2 weaving centre is compared with a cradle-to-gate Life Cycle Assessment (LCA) to an equivalent building of widespread concrete and steel technologies. Adaptive comfort models are applied to on-site measurements and interviews at the case-study building to assess its thermal comfort performance. Building upon the adaptive thermal comfort statistical inference and regional climate models from different global emission pathway scenarios, an energy cooling load calculation is forecasted. The calculated potential energy needs are finally used to extend the LCA to include possible energy requirements for the case study buildings. The study concludes that bamboo buildings in this context have a potential to mitigate 271.3 kgCO2eq/m2 of cradle-to-gate GWP(100a) impacts when replacing widespread conventional technologies. A building-specific adaptive comfort temperature of TC =28.0°C is calculated for the case study building. And an adaptive thermal comfort performance indicator is defined to evaluate that the case study building does not deliver sufficient thermal comfort during 27.8% of its operating hours in a 16-week assessment period. The study concludes that the possible climate-adaptation of the light-weight structure might not be sufficient to guarantee thermal comfort without air conditioning. Environmental impacts from cooling energy requirement forecasts, especially under increased global emission scenarios, are shown to drive the cradle-touse impacts of the bamboo buildings; accounting for 86% of the GWP(100a) impacts of the case study building. However, the overall performance of the bamboo buildings is shown to sustain a mitigation potential (7.7 kgCO2eq/m2yr GWP(100a) impacts for the case study building), even when energy requirements for comfort are accounted.
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    Optimization of Galtneset Reverse Osmosis plant - Optimization of the RO process for a reduced permeate flow and testing the performance using computational program WAVE
    (2023) Kakoti, Sumanna; Chalmers tekniska högskola / Institutionen för arkitektur och samhällsbyggnadsteknik (ACE); Chalmers tekniska högskola / Institutionen för arkitektur och samhällsbyggnadsteknik (ACE); Persson, Frank
    Desalination using Reverse osmosis process at Galtneset water treatment plant situated in Træna municipality located in the Nordland County on the coast of Helgeland, Norway has been facing operational challenges. One reason is due to its overdesigned process configuration with a greater production than required and secondly due to its old and outdated design, currently the plant has been shut down. It is required for the plant to start working and producing drinking water to meet the water demand for in periods of high consumption in the winter and in the summer months when the surface water reservoir is not being able to meet the required water demand. Two scenarios are investigated and modelled using computational software WAVE (Water Application Value Engine), where in first case the number of membrane elements are reduced, and the effect of Trans membrane pressure (TMP) and flux are evaluated for two cases of permeate flow of 23 and 11.5 m3/h at different temperature ranges. Similarly, in the second case the effect of feed flow on the TMP and flux is investigated. Using these two scenarios, the best possible operating conditions for a normal permeate production as well as reduced permeate production are evaluated, and suggestions are made for improvements accordingly. Additionally, to check the change of TMP at different seawater concentration the TMP changes are detected by modelling the process for three different salinity range 32000<35000<40000 mg/L. This controlled system helps to back up the suggestions for selecting the best possible operating conditions. Additionally, normalization of the reverse osmosis data is done to help troubleshoot any potential problems in the process.
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    Numerical Analysis of a PVD-improved Embankment on soft clay - Class A and class C prediction of the Ballina test embankments
    (2023) Sundström, Salomon; Chalmers tekniska högskola / Institutionen för arkitektur och samhällsbyggnadsteknik (ACE); Chalmers tekniska högskola / Institutionen för arkitektur och samhällsbyggnadsteknik (ACE); Karstunen, Minna
    The construction of embankments on soft soil is challenging to engineers due to difficulties associated with their short and long-term stability. This thesis aims to utilize numerical modelling to analyse the behaviour of embankments on soft clay, with special focus on the Ballina test embankments. Two distinct predictions are made: one considering the presence of prefabricated vertical drains (PVDs) installed in the soil and another completely without PVDs. The constitutive model used is the Creep- SCLAY1S model in PLAXIS 2D. The obtained results are compared with on-site measurements to evaluate the effectiveness and reliability of the modelling approach. The thesis involves analysing available soil data and creating a representative soil profile, deriving input parameters for the constitutive model. Furthermore, a simple homogenisation technique is implemented to model the global effect of the PVDs, through changing the vertical hydraulic conductivity in the soil. A comprehensive sensitivity analysis is conducted to identify factors with a significant influence on the simulation results. The results for the PVD-improved embankment demonstrate satisfactory predictions with vertical and horizontal deformations aligning reasonably well when compared with measurement data over a 3-year period. Moreover, the implemented averaging technique effectively captures the enhanced consolidation settlements introduced by the PVDs over the time period. Comparisons with the unimproved embankment indicate little actual improvements in stability for the improved case in the first 3 years. However, spanning over a 40-year period, the vertical settlements approach the same order of magnitude for the two cases, and the horizontal displacements are significantly less for the improved embankment. Indicating a time-dependent nature of stability improvement using PVDs. Ultimately, the parameter derivation process and high-quality laboratory data are vital for accurate simulations. As revealed by the sensitivity analysis, there is significant variations in the results depending on which laboratory test is used to derive the preconsolidation pressure. The discrepancy can likely be attributed to the unusually high strain-rates used for the CRS laboratory tests, in combination with the unusually low strain rates adopted for the IL-tests – emphasizing the experience and skill required of the engineer in order to arrive at accurate predictions.