Selecting the optimal stability framework for high-rise steel buildings is a critical decision that impact both economic efficiency and sustainability. This decision is not easy since there are many stability frameworks to choose from, such as tube, concrete shear-wall, and outrigger system. Designers and clients aspire to compare multiple structural designs, considering both different frameworks and variations in geometry. Unfortunately, the current process of evaluating multiple designs is time-consuming and relies on the designer's experience and rules of thumb, rather than being driven by data. To address this challenge, predictive models can be used to estimate performance in terms of structural and environmental costs based on the given geometry and framework. However, traditional curve fitting methods often fall short in accurately predicting a complex relationship. In response, this study explores the potential of artificial neural networks to accelerate the decision-making process by predicting the most efficient framework during the early design phase while maintaining sufficient accuracy.

To determine this potential, two parametric models were developed using Rhinoceros software to represent buildings with braced framed tubes and outrigger systems. These models automatically optimised beam and column dimensions by FEM of Karamba, aiming to minimise the mass of these structural elements, across a range of building widths (15 to 60 meters) and heights (48 to 300 meters). The resulting data sets of both braced framed tube and outrigger system reflected the structural and environmental costs for the different designs. Separate neural networks were modelled for each framework. These networks were trained on the different data sets. By comparing predicted structural and environmental costs, the models assisted in the selection between braced framed tubes and outrigger systems.

The artificial neural networks accurately approximated structural and environmental costs for both stability frameworks. The Mean Absolute Percentage Error (MAPE) for the braced framed tube was 14%, while the most accurate alternative curve fit, a third-order polynomial, had a MAPE of 25%. For the outrigger system, the neural network achieved an even lower MAPE of 7%, where the most accurate alternative curve fit, also a third-order polynomial, had a significantly higher error with a MAPE of 31%. The neural networks outperformed traditional curve fitting methods. Additionally, the neural network generated instant results, taking only a second compared to the parametric model’s 5 to 30 minutes. However, achieving overall time efficiency with the neural models will require approximately three months when considering both setup time and output generation time. Optimal stability varied based on specific width and height combinations: when looking at environmental costs, the braced framed tube excelled for lower (50-80m) and higher heights (200-300m), while the outrigger system was more efficient for middle heights (80-200m). As the structure’s slenderness increased, the braced framed tube regained efficiency for the middle heights.

Impact of the stability framework is defined as the relative contribution of embodied carbon of the stability framework to the total embodied carbon of the structure (including superstructure and floors). The impact of the stability framework ranged from 25% to 57% for the braced framed tube and 33% to 66% for the outrigger system, with the impact increasing with the building's height... ... Read more

The Netherlands is grappling with a substantial housing crisis, marked by an estimated shortage of 380,000 houses. To address this issue, an annual creation of 100,000 new housing units is deemed necessary. However, the current construction rate stands at only 70,000 houses per year, indicating a considerable gap in resolving the housing crisis. Recognizing the potential of urban densification, especially through vertical extension using Cross-Laminated Timber (CLT), presents a sustainable solution. Nevertheless, challenges arise, such as the unique approach to vertical extension and the structural constraints posed by CLT's lower strength compared to materials like concrete.

This research aims to identify the vertical extension potential of CLT in existing buildings by developing a parametric tool that considers various structural constraints. The ultimate goal is to contribute to informed decision-making practices for sustainable and effective structural design in vertical extensions.

The methodology comprises four phases: analysis, synthesis, simulation, and evaluation. The analysis phase examines existing vertical extensions, structural context, and spare capacity concepts, forming the basis for synthesis. A parametric tool is then created using Grasshopper and Karamba, employed in the simulation phase to conduct a parameter study based on the analysis phase findings. This study assesses the effects of the original structure's base geometry on spare capacity and evaluates the design of the extension itself.

The results of the parameter study reveal that the presence and placement of a stability core have the most significant impact on spare capacity in the existing building. The original construction grid and building height also influence spare capacity, though to a lesser extent. Additionally, wall layouts in the extension, such as core alignment, functional design, and façade-aligned layouts, significantly affect spare capacity utilization in both the original structure and the extension.

Variations in extension grid show differences in spare capacity utilization, with effects smaller in magnitude compared to wall layout variations and displaying less dependence on the original structure's geometry. In the vertical extension itself, failure tends to concentrate on connections between CLT panels and floors, particularly with wall layouts emphasizing functional design.

In conclusion, the research, coupled with the development of a parametric tool, successfully achieves its main goal. The tool's accuracy is validated through extensive assessments of horizontal load transfer from the extension to the original structure. The parameter study highlights the significant effects of various parameters on extension design and the original structure, emphasizing the tool's utility in exploratory design stages for vertical extensions. ... Read more

The construction sector plays a significant role in the environment, and concrete structures constitute a substantial portion of this sector. The government is actively seeking ways to reduce the environmental impact of construction activities by promoting a more sustainable approach. In the Netherlands, a considerable number of repetitive cellular residential buildings are constructed using the tunnel formwork building method. Although this method can be enhanced in terms of sustainability by utilizing environmentally friendly cement mixtures, it poses challenges, such as an increase in execution time. This research aims to explore a more sustainable approach to the tunnel formwork building method while devising strategies to maintain the same execution time as before.

The tunnel formwork building method operates with a 24-hour daily execution cycle. During the initial 8 hours, the formwork, reinforcement, and installations are set up, followed by pouring concrete at the end of the day. After 16 hours, the concrete attains sufficient strength for the formwork to be dismantled, allowing it to be placed on the next grid. This approach results in rapid construction, high-quality output, and cost-effectiveness. However, a significant drawback is the reliance on CEM I mixtures, which consist of approximately 100\% Portland cement, contributing to substantial greenhouse gas emissions and environmental impact. Blended cement mixtures, such as CEM II and CEM III, offer more environmentally friendly alternatives by incorporating lower percentages of Portland cement blended with fly ash or blast furnace slag. Despite their environmental benefits, these mixtures exhibit a slower strength development, making it challenging to achieve a hardening time of 16 hours.

In pursuit of a dependable and sustainable approach to the tunnel formwork building method that preserves the 24-hour daily cycle, the research question is articulated as follows: "What concrete mixtures and execution strategies can be applied in the Netherlands to diminish the environmental impact of the traditional tunnel formwork building method, utilizing sustainable cement mixtures, while upholding existing advantages in time, cost, and quality?" This research question will guide the exploration of optimal concrete mixtures and execution measures for implementing sustainable cement mixtures within the tunnel formwork building method, while ensuring the continuity of the daily execution cycle.

In addressing this research question, an Excel calculation sheet has been developed. This sheet serves to compute the material costs, shadow costs, and formwork removal time associated with specific modifications in the design, concrete mixture, and additional execution measures for the tunnel formwork building method. The calculation sheet offers flexibility with three grid sizes: 4.5m, 6.0m, and 7.2m. It incorporates various concrete properties, such as the cement mixture (CEM I, CEM II, or CEM III), w/c ratio (0.45 or 0.55), aggregate types (fine and coarse), Blaine value (300 or 400$m^2/kg$), and admixtures (basic and additional). Additionally, the calculation sheet allows for adjustments in seasonal conditions, with options for summer (20°C) or winter (10°C)... ... Read more

Numerous structural failure incidents have occurred in the past years. It was found that current methods, such as NEN 2767, fall short in guaranteeing the structural safety of existing buildings. Although structural failure incidents infrequently result in casualties, there are also social and economic consequences that impact both building user as owner. Interviewed asset managers have noted that the current lack of insight into a building’s structural condition often leads to preventable maintenance and repair costs, and safety risks. When coupled with changes in the outdoor and built environment, such as a focus of continuity in use, these risks become increasingly challenging for owners to manage.
To ensure structural safety of significant public buildings within CC3, mandatory assessment via NTA 8790 must be performed. However, this method is exclusively tailored to CC3 buildings and only considers potential casualties as risk consequences. This strategy neglects CC2 buildings and other potential consequences, exposing them to elevated risks due to a lack of insight into their structural conditions. All the asset managers interviewed for this study, all managing CC2 buildings, reported these issues.
The goal of this thesis is to develop an efficient and effective assessment method to evaluate existing consequence class two buildings on structural safety to prevent incidents with structural failures. As a start (CC2) building typologies within the Netherlands were examined to determine the typologies for which the method should be optimised. Subsequently, structural failure incidents were analysed, resulting in a list of common causes that should be considered during the assessment. However, due to limited data availability, expert interviews and general literature this list is not exhaustive but rather an initial attempt. It can serve as a focus during the assessment but should not be solely relied upon. Finally, existing assessment methods were evaluated based on trustworthiness, effectiveness and efficiency. The findings from this evaluation have been incorporated into the development of an efficient and effective assessment process, which is described in the document.
The assessment process developed in this study was validated by applying it to two existing buildings, leading to the following conclusions. The assessment process developed in this study has proven effective in evaluating the structural safety of CC2 buildings, thereby preventing incidents relating to structural failures. While the necessity for comprehensive risk analyses does impact the time required for the assessment, these analyses have been optimised to concentrate on the most critical aspects. Along with other efficiency-enhancing aspects, it presents an efficient method within the parameters of effectivity and trustworthiness.
However, as revealed during validation, not all deficiencies can be detected using this method. There will always be hidden deficiencies that remain undetected and assessors are made aware of this limitation. Despite this constraint, the method provides an efficient and effective evaluation of the structural safety of existing buildings.
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Innovative solutions for safety and risk management on construction sites are required to reduce the amount of accidents that occur globally, as too many occupational accidents still happen in the Architecture, Engineering and Construction industry. A particular problem is the fall from height (FFH) accidents on construction sites, due to failing barriers with the underlying cause of insufficient planning. In previous research it has been suggested to develop dedicated BIM plug-ins to automate and visualise risk identification and evaluation of construction sites as a means to assist the safety management process. To explore the impact of BIM on FFH accident reduction through automation and visualisation, a digital tool prototype is developed. This prototype focusses on fall from height (FFH) identification on construction sites during early project phases of civil engineering projects. It is programmed in Autodesk Dynamo for Revit, based on technical and functional requirements derived from literature and industry professionals. A simulation of the FFH tool prototype has been conducted through a pilot project. The result of this product development is a working fall from height detection prototype that is to be used as a supporting tool during the safety analysis of construction site design in Dutch civil engineering projects. The developed tool is added to the body of products that can be used for digitalisation and innovation within the construction process, where it digitalises part of the safety management process that is otherwise performed manually. The added value of the tool prototype is the addition of automated risk detection, creating support in the design and planning process and providing added information to group discussion on safety matters in risk identification and evaluation meetings. Recommendation for future use of the tool is to implement the FFH tool prototype during the design phase to provide the designer with insights in the safety of the constructability. Additionally, the FFH tool prototype can be implemented by safety managers to use the results during safety meetings for better discussion and evaluation of the construction site. For the implementation, improvement of the level of detail in the 3D models for the projects and including temporary construction site works is essential. For further development it is recommended to focus on improving the import of linked models into the script and developing alternative operations to determine the height differences. More developments and improvements can be made to the script to increase the applicability on more complex projects. Concluding, the FFH tool prototype is considered to bring added value in digitalising an otherwise manual process regarding safety management. It is suggested to incorporate use of the FFH tool prototype in the design and planning process to proactively engage in digitalising and innovating engineering processes. ... Read more