Examensarbeten för masterexamen

Länka till denna samling:

https://odr.chalmers.se/handle/20.500.12380/4

Browse

Visar 1 - 5 av 3505

Evaluation of the Shear Punching Test - A comparative analysis with fall-cone and direct simple shear test
(2024) Hall, Evelina; Lindeby, Ellen; Chalmers tekniska högskola / Institutionen för arkitektur och samhällsbyggnadsteknik (ACE); Chalmers tekniska högskola / Institutionen för arkitektur och samhällsbyggnadsteknik (ACE); Karlsson, Mats; Karlsson, Mats
Between the years 2019 and 2023, SGI developed a new method to assess the undrained shear strength in cohesive soils. The new test, named the shear punching test, is developed to possibly replace or compliment existing test methods, particularly the fall-cone test. The fall-cone test, which is an index test for evaluating the shear strength of soil, is based on empirical analyses. This makes it challenging to derive mathematically and often underestimates the results. A method similar to the shear punching test was devised by Bror Fellenius 1935. Although the results were considered promising at the time, the method came to nothing. This thesis aims to investigate the potential of the shear punching test to become a standardized test in geotechnical investigations by analyzing the correlation between the shear punching test, fall-cone test and direct simple shear test (DSS). This is achieved by conducting a literature review and analyzing results from soil samples where all relevant methods have been performed. Furthermore a numerical model of the shear punching apparatus is developed using Plaxis 2D, and an in depth stability analysis is conducted on a section from Gamleby Harbor in Västervik using Geostudio SLOPE/W. The results show that the shear strength that is calibrated to the DSS test aligns reasonably well with empiricism and naturally in relation to the shear strength obtained from DSS tests. The normalized shear strength however, shows a wide spreading within 2 standard deviations as well as a few outliers. Numerical modeling in Plaxis can to some extent recreate results from the laboratory tests. During evaluation of the shear strength trend for the use in stability analysis, the shear punching test leads to an increase in cases where the DSS test is excluded. In conclusion, the shear punching test cannot be considered a complete replacement for the fall-cone test as an index test, as the sensitivity of the soil cannot be determined. However, it can be used as a complement to other tests for the evaluation of the undrained shear strength in cohesive soils. Due to the scatter in the normalized shear strength, no specific range for certain parameters can be observed where shear punching is relevant or not. It can be concluded that it is possible to recreate the shear punching numerically and obtain results that reasonably align with laboratory results. Including results from the shear punching test in the evaluation of the shear strength trend will only have an effect if more reliable test methods are not included.
Exploring the Viability of Using WtE Incineration Ash as a Cement Replacement in Concrete
Eriksson, Joel; Chalmers tekniska högskola / Institutionen för arkitektur och samhällsbyggnadsteknik (ACE); Chalmers tekniska högskola / Institutionen för arkitektur och samhällsbyggnadsteknik (ACE); Baba Ahmadi, Arezou; Karlfeldt Fedje, Karin
The increasing importance of reducing greenhouse gas emissions demands new environmentally sustainable building materials. In the concrete industry most of the emissions comes from the production of cement. Research on materials that can be used as replacements for cement (SCMs) could help reduce the climate impact of the concrete industry. One of the possible SCMs that could be used are ash from WtE incineration. In this report the viability of the use of three different ash fractions from WtE incineration as cement replacement are be evaluated. These are a fly ash sample, an incinerator bottom ash sample and a mineral fraction incinerator bottom ash sample. Chemical and mechanical properties was evaluated using different techniques including a modified R3 method, compressive strength tests, PXRD and leaching tests with ICP-MS. It was found that all three of the ash fractions had chemical reactivity and the mechanical strength tests suggested that two of the ash fractions fly ash and MIBA had effect on the mechanical strength while the slag did not have ant effect. The results from the leaching tests were compared to thresholds on allowed limits of leaching from monolithic concrete samples and found to be below these thresholds. However, the limited knowledge and regulations on monolithic samples made the interpretation of these results difficult. The result from this thesis suggests that the use of WtE incineration ash a SCM is a possibility but that more research is needed. It is also concluded that the need for more and less complicated to understand regulations regarding leaching from monolithic concrete is needed in Sweden and that the current lack of regulations might be hindering the adoption of new sustainable building materials.
Potential Circular Strategies for Load-Bearing Building Elements at the End-of-Life
(2024) Slunitschek, Joel André; Maharjan, Chandani; Chalmers tekniska högskola / Institutionen för arkitektur och samhällsbyggnadsteknik (ACE); Chalmers tekniska högskola / Institutionen för arkitektur och samhällsbyggnadsteknik (ACE); Wallbaum, Holger; Wöhler, Anna
The growing pressure on planetary boundaries, highlighted by the 2023 Stockholm Resilience Centre report shows that six out of nine boundaries have been exceeded. The construction sector, responsible for 39% of global CO2 emissions, plays a pivotal role in this context. This study examines the potential of circular economy strategies to mitigate the environmental impact of multi-residential buildings, focusing on the end-of-life phase and material recovery during demolition. Circular strategies for structural building elements in multi-residential buildings are investigated through a hotspot analysis of life cycle assessments of Swedish multi-residential buildings and a comprehensive literature review. The analysis identifies that structural elements such as floor slabs and load-bearing walls are the major contributors to the buildings' carbon footprints. The work focuses on the circular economy strategies, element reuse and material reuse by evaluating their applicability to different building elements and by identifying practical approaches to enhance circularity within the construction industry, addressing key technical hurdles and proposing viable solutions for sustainable building practices. Element reuse, although requiring repair and reinforcement due to previous life cycle damage, is deemed highly effective. Material reuse is highlighted as a viable alternative for elements like cross-laminated timber and glulam, especially when element reuse is not feasible. Recycling, while common, often results in downcycling, underscoring the need for prioritizing reuse strategies. The analysis indicated varying strategies are appropriate for different elements. The research identifies significant challenges, including the durability of aged elements, the lack of standardized guidelines, and the complexity of implementing CE strategies for structural elements. Prefabricated elements, such as hollow-core slabs, CLT and Glulam, demonstrate high potential for reuse due to their modular design and ease of recovery. However, in-situ cast elements present greater challenges due to individualized reinforcement layouts and connection areas. The study concludes that a successful transition to a circular economy in the building sector requires collaborative efforts, detailed technical information, and the development of standards to facilitate the reuse and recycling of structural elements.
Predicting the environmental impact of structural systems with parameterization: Development of a design tool for the early design stages
(2024) Flyman, Robin; Chalmers tekniska högskola / Institutionen för arkitektur och samhällsbyggnadsteknik (ACE); Chalmers tekniska högskola / Institutionen för arkitektur och samhällsbyggnadsteknik (ACE); Ander, Mats; Jonsson (VBK) , Daniel; Söderqvist (VBK) , Jonathan; Säwén (Chalmers), Toivo
With the increasingly alarming threat from global warming, there is an urgent need to reduce the CO2 emissions across all sectors. With 38% of the emissions globally and 21% in Sweden, there is a great potential to reduce the carbon footprint of the construction sector. The emissions from a building are split into embodied and operational carbon, where new laws and regulations in Sweden will start targeting the embodied carbon in buildings. In Sweden, the structural system accounts for half of the embodied carbon in a building on average. The current procedure of conducting a life cycle assessment is often time-consuming and not suitable for early design stages, where there are many uncertainties. Designers need to have a holistic view when considering the emissions of a structural system, as optimising one part can increase the emissions from other parts of the system. In this thesis, a parametric tool was developed to address these points; uncertainties in the early stages, time constraints and limited knowledge regarding how the interplay is between the environmental impact and the parameters that controls the design of the structural system. The parametric tool has an emphasis on structural design, where the aim is to generate structural systems and predict the environmental impact at early stages, where the most impact can be achieved to the lowest cost. This tool models a framed structural system with columns, beams, and slabs, then performs a load takedown. The modular design of the tool allows it to be modified or expanded in the future. The parametric tool uses pre-calculated elements to design the structural system, after which it calculates and display the environmental impact to the user in a comprehensive way. Optimisation algorithms can be used to find some of the most optimised design alternatives for the given objectives. A case study has been performed to verify the performance and accuracy of the tool. The results from the case study showed that the tool will select similar cross sections as a structural engineer in the preliminary design stages, resulting in comparable carbon emissions. It was challenging to compare the emissions for the structural system between the reference building and the system generated by the tool, as the reference building included load bearing walls, which is not included in the tool at this stage. The tool could be further developed by including load-bearing walls, foundation, and horizontal stabilisation.
Multi-Criteria Decision Analysis as a Supporting Tool for Decision-Making in Construction Projects
(2024) Hjort, Jesper; De Souza Nazareth Giorgi, Rodrigo; Chalmers tekniska högskola / Institutionen för arkitektur och samhällsbyggnadsteknik (ACE); Chalmers tekniska högskola / Institutionen för arkitektur och samhällsbyggnadsteknik (ACE); Wallbaum, Holger; Goto, Yutaka; Claeson-Jonsson, Christina
The construction industry faces significant environmental and financial challenges, driven by high greenhouse gas emissions, intensive energy consumption, and rising resource costs. This thesis explores the role of Multi-Criteria Decision Analysis (MCDA) in managing project complexity and improving decision-making processes. MCDA integrates multiple criteria and stakeholder perspectives, facilitating structured and rational decision-making crucial for the dynamic construction environment. The research employs both qualitative and quantitative methods, including 8 interviews and questionnaires with key stakeholders, with the purpose to develop an MCDA prototype using Analytic Hierarchy Process (AHP) and Simple Additive Weighting (SAW) methods. The findings demonstrate that MCDA aids project teams in structuring, analysing, and deciding on complex issues, leading to informed decisions aligned with project goals. Specifically, MCDA facilitates clear prioritization of sustainability targets, as evidenced by the consistent recommendation for timber cladding. It also showed how utilizing MCDA as a tool minimizes stakeholder conflicts through transparency and traceability of decisions, enhances the ability to address unforeseen challenges, and supports robust planning for future uncertainties. Consequently, MCDA leads to a streamlined decision-making process, improved stakeholder consensus, and effective handling of complex construction project dynamics. The case study shows that clear project goals and effective stakeholder management lead to consistent decision recommendations. MCDA in this sense improves decision-making quality but can also be a demanding tool in terms of time and cognitive efforts for participants. This suggests a need to explore other MCDA methods for varying scenarios to better understand the effectiveness of MCDA.

Browse

Senast publicerade