Year: 2025
Author(s): Jonatan Isaksson, Jelke Dijkstra
Publication Type: Journal article
The pile cycle of an axially loaded displacement pile in a sensitive natural clay has been modeled using a coupled finite-element code for large deformations. The originality lies in the effective stress-based analysis with a consistent set of model parameters that considers all necessary soft soil features, i.e., anisotropy, destructuration, and rate dependency. Furthermore, the modeling approach is successfully benchmarked at all stages of the pile cycle (initialization, installation, equalization, loading). The benchmarking consisted of model calibration at element level, model selection using simulated and measured cone penetration test (CPTu) data, comparisons of measured and computed radial and shear stress during pile installation, and pile load testing. The results indicate that, with the exception of the absolute magnitude of the excess pore-water pressures generated during installation, the trends observed in the experimental data were captured well at all stages. Furthermore, several aspects of large deformation modeling of CPTu penetration, and pile installation were discussed. Most importantly, the difficulty in modeling the postpeak softening behavior and the balancing effects of the viscoplastic response (rate dependence) and strain-softening (destructuration) was highlighted. Finally, the empirical relation between the CPTu response and the bearing capacity of pile could be numerically confirmed. In conclusion, a first step is provided for the inclusion of the spatiotemporal response of sensitive natural clay over the full pile cycle in system-level geotechnical finite-element analysis.
Year: 2024
Author(s): Radostin Mitkov, Mariya Pantusheva, Dessislava Petrova-Antonova, Vasilis Naserentin, Anders Logg
Publication Type: Paper in proceeding
The rapid urbanization trend has led to complex challenges in managing urban environments, ranging from energy consumption to environmental quality and public health. In response, the concept of city digital twins has emerged, offering a promising approach to understanding and managing urban complexity. City digital twins utilize real-time data and simulations to create virtual replicas of urban environments, enabling stakeholders to analyze, optimize, and make informed decisions about various aspects of city life. Computational Fluid Dynamics (CFD) plays a crucial role within city digital twins, offering capabilities to simulate wind flow dynamics, air quality, and pollutant dispersion within urban environments. This paper explores the opportunities and challenges of integrating CFD within city digital twins. Opportunities include optimizing urban planning and design processes, enhancing environmental quality, and improving public health outcomes. However, challenges such as data integration and quality, implementation constraints, computational complexity, and communication of results must be addressed to realize the full application potential of CFD in urban environments. Despite these challenges, the integration of CFD within city digital twins holds promise for creating more livable, sustainable, and resilient cities in the face of urbanization and climate change.
Year: 2024
Author(s): Anita Ullrich, Franziska Hunger, Ioanna Stavroulaki, Adam Bilock, Klas Jareteg, Yury Tarakanov, Alexander Gösta, Meta Berghauser Pont, Fredrik Edelvik
Publication Type: Journal article
Pedestrian movement has always been a main concern for urban planning and design, but has become more important within the sustainable development agenda, as walking is crucial to reduce urban emissions and foster livable cities. Therefore, urban planners need to be able to take pedestrian movement into consideration as part of the workflow of planning and designing cities. This study outlines a comprehensive workflow tailored for urban planners. It proposes a hybrid model that integrates an agent-based model, which simulates the micro-scale movement of pedestrians in outdoor urban environments, with a network model, which predicts the aggregated pedestrian flows on a macro-scale. The hybrid model has been applied to a pedestrian precinct in the city centre of Gothenburg, Sweden and has been compared to real-world measurements. The reasonable agreement between the simulation results and the real-world data supports the reliability of the proposed workflow, underscoring the model’s capability of predicting pedestrian movement statistically on a large scale and individually on a local scale. Furthermore, the model enables the analysis of flow distributions and movement restrictions and facilitates the analysis of different design scenarios as well as specific pedestrian behavior. This functionality is valuable for urban design and planning practice, contributing to the optimization of pedestrian flow dynamics.
Year: 2024
Author(s): Emil Adiels, Mats Ander, Christopher John Kenneth Williams
Publication Type: Journal article
Surface geometry plays a central role in the design of bridges, vaults and shells, using various techniques for generating a geometry which aims to balance structural, spatial, aesthetic and construction requirements.
In this paper we propose the use of surfaces defined such that given closed curves subtend a constant solid angle at all points on the surface and form its boundary. Constant solid angle surfaces enable one to control the boundary slope and hence achieve an approximately constant span-to-height ratio as the span varies, making them structurally viable for shell structures. In addition, when the entire surface boundary is in the same plane, the slope of the surface around the boundary is constant and thus follows a principal curvature direction. Such surfaces are suitable for surface grids where planar quadrilaterals meet the surface boundaries. They can also be used as the Airy stress function in the form finding of shells having forces concentrated at the corners.
Our technique employs the Gauss-Bonnet theorem to calculate the solid angle of a point in space and Newton's method to move the point onto the constant solid angle surface. We use the Biot-Savart law to find the gradient of the solid angle. The technique can be applied in parallel to each surface point without an initial mesh, opening up for future studies and other applications when boundary curves are known but the initial topology is unknown.
We show the geometrical properties, possibilities and limitations of surfaces of constant solid angle using examples in three dimensions.
Year: 2023
Author(s): Vasilis Naserentin, Anders Logg, Dag Wästberg
Publication Type: Journal article
Digital Twin Cities Centre (DTCC) Builder is a mesh generator for automatic, efficient, and robust mesh generation for large-scale city modeling and simulation. Using standard and widely available raw data sources in the form of point clouds and cadastral data, DTCC Builder generates high-quality 3D surface and volume meshes, suitable for both visualization and simulation. In particular, DTCC Builder is capable of generating large-scale, conforming tetrahedral volume meshes of cities suitable for finite element (FEM) simulation.
Year: 2023
Author(s): Mattia Mangia, Carla Di Biccari, Mattias Roupé
Publication Type: Paper in proceeding
Complex infrastructures such as railway networks face increasing challenges related to resource allocation, external events, constraints, and demands. Therefore, it is crucial to optimize the Asset Management (AM) phase to ensure the value and functionality of the assets. The integration of Building Information Modelling (BIM) and Geographic Information Systems (GIS) can support this phase, but it can only yield benefits with a comprehensive approach that considers and addresses the specific needs and resources of the assets and their AM organization. The main benefits include improved data management, manipulation, information visualization and optimized resource allocation. This study describes an intermediate step towards developing a BIM/GIS integration framework for AM that can guide both researchers and practitioners. The framework aims to bridge theory and practice by incorporating insights from literature reviews and case studies. Its main objectives are to provide a comprehensive multi-stakeholder view and methods for effectively integrating BIM and GIS in this context. To develop the framework, the study employed focus groups, interviews, and practical BIM/GIS tests, which provided insights reported in this article. Furthermore, the study provides research directions for effective BIM/GIS integration in infrastructure AM.
Year: 2023
Author(s): Vasilis Naserentin, Georgios Spaias, Anestis Kaimakamidis, Nikos Pitsianis, Anders Logg
Publication Type: Paper in proceeding
The growing interest in creating digital twins of cities has sparked a surge in the development of detailed 3D models. In this paper we examine the current state-of-the-art in generating high-resolution 3D models of cities using neural network techniques. Additionally, we showcase the outcomes of two case studies that demonstrate the practical applications of these techniques in 3D city model generation. The first case study focuses on rooftop segmentation using publicly available Swedish cadastral data, while the second case study explores façade feature extraction using Google Street View data.
Year: 2022
Author(s): Stoyan Boyukliyski, Dessislava Petrova-Antonova, Sanjay Somanath
Publication Type: Paper in proceeding
In order to aid the decision making process related to the provision of public services as to maximize the benefits for society, it is crucial to evaluate the current social facilities demand in terms of spatial distribution and access. The paper aims to solve this problem by proposing a method for automated assessment of the coverage of public services within an urban region using a capacitated graph. The methodology abstracts residential buildings into demand nodes and public service buildings into supply nodes within a graph and then uses shortest distance calculations in order to balance the two, while prioritizing residential buildings based on distance. The paper is focused on creating a general pipeline that can be used on any type of public services, as long as a certain geospatial and demographic data are available. The method is described without referencing specific tools, but focusing on the general procedure. The procedure is then applied to the whole city of Sofa, focusing on assessing the coverage of kindergartens using the 15 minutes walking distance, followed by a brief discussion of results.
Year: 2020
Author(s): Viktoria Sundquist, Alessio Domenico Leto, Mathias Petter Gustafsson, Mikael Johansson, Mattias Roupé
Publication Type: Paper in proceeding
The construction industry strives to implement digitalization and Building Information Modelling (BIM). Studies of BIM in construction claim that a pronounced BIM strategy, knowledge of the subject and a willingness to change are important factors to succeed, but even when such conditions are in place, BIM implementation in construction production is scant and has limited impact. So how should the construction industry go from grand digital visions to practical application in reality? By identifying gains, obstacles and success factors on company, project and sector levels the paper aims to set out a road map for successful BIM implementation in construction production. Data sets, both qualitative and quantitative from eleven studies of using BIM in construction production, show that although the industry is making progresses in implementing BIM and digitalization, the full potential is far from realised. Specifically, the research presents an analysis of factors in relation to (1) strategy and innovation, (2) technology, (3) organizing, and (4) ecosystem. Conclusively, all these levels are strongly interdependent and need to be considered by adopting a holistic approach to reach an enhanced implementation.
Year: 2020
Author(s): Alexander Gösta, André Agi, Jacob Flårback, Jesper Karlsson, Ellen Simonsson
Publication Type: Journal article
This article aims to map how different digital tools can be useful for architects and how they might affect their work processes. Researchers and professionals were interviewed to investigate what they found valuable to measure, which methods they used within their analyses, as well
as the opportunities and risks they see for the future of the field with regards to digital tools. As part of the survey, a workshop was held with architects and project managers examining the possibilities of connecting existing methods and tools to the sustainability certification system,
City Lab Action Guide, and through that, to achieve a more ambitious set of sustainability goals for the projects. Findings from the study indicate that there are risks associated with giving data an increasingly important role in the design work. A working model never provides the full truth
but is inherently limited by its constraints. It is important to acknowledge that all angles and aspects of a problem can never be represented in a model. Another possible risk identified lies in the quality of, and access to, data. In a scenario where data plays an increasingly important
role, it is not only the quality of the datasets that is of utmost importance, but it is equally important that the urban planners who request the analyses ask the questions first, and then collect the necessary data, instead of vice versa.
