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Senast publicerade

Elastic Rotational Stiffness of an Embedded Steel Plate-Timber Connection A Simplified Solution, Based on an Analytical Study Verified by Numerical Modeling
(2026) Gustafsson, Viktor; Katergi, Karam
Connections are among the most complex elements to analyze and design within struc tural engineering. They consist of multiple interacting components, involve intricate load-transfer mechanisms, and exhibit nonlinear behavior that is difficult to capture us ing simple assumptions. Although numerical modeling can be employed to evaluate connection behavior and stiffness, it is often computationally demanding and requires careful verification and interpretation. Consequently, connections are frequently idealized in the design phase as either perfectly pinned or fully fixed, and in some cases, assigned an intermediate stiffness. While such simplifications may be acceptable for simple structural systems, they offer limited insight into the governing parameters that influence connection stiff ness. These assumptions restrict the ability to optimize connection design and may be insufficient for structures with demanding performance requirements, such as high-rise hybrid buildings. The objective of this Master’s thesis is to develop a realistic analytical model for the internal parts of a steel-timber connection and the total rotational stiffness in the elastic state. The study considers an embedded steel plate connection, which is widely used due to its aesthetic appeal and ease of on-site installation. To achieve this objective, load paths and structural models are identified for internal parts in connection. By summing the resulting elastic deformations of each part, the total deformation and rotational response are obtained. The analytical results are sub sequently validated and calibrated against numerical simulations, including a 3D solid model and a 2D beammodel. Basedonthisprocess, asimplifiedandverifiedexpression for estimating the rotational stiffness of the embedded steel plate connection is derived. Keywords: embedded steel plate connections, slotted in steel plate-timber connection, elastic rotational stiffness, timber-concrete connection, connection rigidity.
Structural Modeling for Preliminary Design of Steel-Concrete Composite Bridges
(2026) Elmelid, Hugo; Bergh, Albin
The preliminary design of steel-concrete composite bridges must be completed in a limited time frame, often representing a small fraction of the time allocated to the final design. This requires fast and accurate methods for estimating load effects, member di mensions, and material quantities. At the same time, preliminary estimates must remain consistent with the final design while being competitive in bidding. This study evaluates modeling approaches for determining load effects using Brigade/ Plus and investigates methods for preliminary cross-section design. A literature study was conducted to identify relevant modeling approaches, followed by a case study of a steel-concrete composite bridge in Akalla. Three main modeling approaches were examined: a shell model, a grillage model, and three-beam-element-based models. The approaches were assessed with respect to accuracy, computational efficiency, and suit ability for preliminary design. The results show that a transverse beam model with vertical springs in combination with a longitudinal beam model is the most suitable modeling approach for preliminary design. Although conservative, the model provides a favorable balance between accu racy, simplicity, and computational efficiency. The study further demonstrates that the model could be improved by considering the spread of the load through the concrete slab using distribution angles. By updating the model by incorporating the resulting effective widths, material consumption was reduced by up to 17% compared to the original model. Furthermore, adjusting the slab strip width proved more effective than modifying the spring stiffness alone. The greatest improvements were observed in cases where fatigue governed the design. The proposed modeling approach provides a practical workflow for preliminary design, enabling more accurate estimations of material quantities during the limited time frame. Keywords: Steel-concrete composite bridges, preliminary design, load distribution fac tors, transverse beam model, structural modeling
Reverse Transcriptase Characterization and Engineering for Genome Editing
(2026) Emy, Saetre
Abstract Templated editing, consisting of a Cas9 enzyme coupled to a reverse transcriptase (RT) directed by a programmable guide RNA to install edits in the genome, offers unprecedented potential for treating genetic diseases. Yet, translation to clinical applications is hindered by unpredictable editing efficiency and limited understanding of how RT properties influence outcomes. This thesis systematically characterized a panel of established and novel RTs, including engineered Moloney Murine Leukemia Virus (MMLV) derivatives, compact bacterial RTs, and AstraZeneca-proprietary candidates, through complementary cellular and in vitro assays to establish rational engineering principles. A HiBiT reporter system enabled high-throughput quantification of templated editing (TE) efficiency in cellulo, while biochemical assays were used to measure polymerization activity, DNA/RNA binding affinity, thermostability, and aggregation propensity. Results suggested that successful templated editing requires optimization of three critical properties: thermostability, protein solubility, and DNA/RNA substrate affinity. Two iterative rational engineering cycles based on this hypothesis highlighted a synergistic relationship between the three properties. Engineered variants that combine solubility, stability and substrate affinity enhancements achieved up to 2.4 times higher editing efficiency compared to the established state-of-the-art benchmarks. By systematically defining the biochemical and biophysical property thresholds required for TE efficiency, this work establishes an evidence-based design framework that transform RT development from empirical screening toward rational, predictive engineering, diminishing optimization timelines and accelerating therapeutic development.
Evolution Strategies as an Alternative to Reinforcement Learning in De Novo Molecular Generation - Evaluating Distribution Based Gaussian Evolution Strategies in REINVENT vs. Policy Based Reinforcement Learning on the Practical Molecular Optimization Benchmark
(2026) Eklöv, Malva
De novo molecular generation examines how computational methods can propose novel drug candidates by scoring generated molecules against desired properties and updating generation toward higher scoring regions. One approach trains a SMILES based language model and fine tunes it toward such regions. Fine tuning is commonly performed with policy gradient reinforcement learning (RL), as in AstraZenecas highly optimized REINVENT platform. An alternative is evolutionary strategies (ES), where a population of models is created and their parameters are updated to bias generation toward higher scores. This thesis investigates how distribution based ES compares with RL when implemented in REINVENT and evaluated on the Practical Molecular Optimization benchmark. OpenAI-ES shows near competitive performance on scoring and diversity metrics, whereas variance estimating Natural ES methods perform poorly. Variations of fixed variance ES are explored, and a novel sampling technique that biases generation toward high diversity shows promising performance across multiple metrics.
Data-Driven Requirement Development - From Field Data to Reliability Requirements: Identifying and Analyzing High-Performing Automotive ECUs
(2026) Wang, Yimin
This thesis investigates a data-driven methodology for reliability-oriented requirement development in automotive electronics. Traditional automotive reliability engineering is primarily failure-focused, relying on warranty analysis and reactive investigation of defective components. However, such approaches provide limited understanding of why certain Electronic Control Units (ECUs) consistently demonstrate strong field reliability performance. The research initially aimed to analyze relationships between ECU operational conditions and field reliability behavior through classical data-driven analysis. However, the required centralized operational-condition dataset was not available within the industrial data environment. Consequently, the study evolved toward a practical industrial screening methodology based on available enterprise engineering and field-quality data resources. The proposed framework integrates multiple industrial datasets, including the KDP Engineering Database (KDP), Quality Follow-Up (QFU) warranty repair records, the Early Warning System (EWS), and procurement-related production volume data. By combining field repair occurrence with market exposure normalization, ECU populations with exceptionally low repair occurrence relative to deployment volume were identified. Selected ECUs subsequently underwent hardware-oriented engineering investigation, including open-lid assessment, Printed Circuit Board (PCB)-level visual inspection, and review of available Design Verification (DV) and Product Validation (PV) documentation. The investigation focused on identifying recurring robustness-related engineering characteristics rather than performing direct failure analysis. Observed features included reinforced PCB mechanical support structures, controlled PCB cleanliness, environmental protection strategies, and evidence of robustness-oriented validation practices. The work demonstrates how multiple industrial engineering and field-quality data sources can be systematically combined to support evidence-based reliability investigation and practical reliability requirement development in automotive electronics.