A structure subjected to extreme load due to explosion or human error may lead to progressive collapse. One of the direct methods specified by design guidelines for assessing progressive collapse is the Alternate Load Path method which involves removal of a structural member and analysing the structure to assess its potential of bridging over the removed member without collapse. The use of this method in assessing progressive collapse therefore requires that the vertical load resistance function of the bridging beam assembly, which for a typical laterally restrained reinforced concrete (RC) beams include flexural, compressive arching action and catenary action, be accurately predicted. In this thesis, a comprehensive study on a reliable prediction of the resistance function for the bridging RC beam assemblies is conducted, with a particular focus on a) the arching effect, and b) the catenary effect considering strength degradations. A critical analysis of the effect of axial restraint, flexural reinforcement ratio and span-depth ratio on compressive arching action are evaluated in quantitative terms. A more detailed theoretical model for the prediction of load-displacement behaviour of RC beam assemblies within the compressive arching response regime is presented. The proposed model takes into account the compounding effect of bending and arching from both the deformation and force points of view. Comparisons with experimental results show good agreement. Following the compressive arching action, catenary action can develop at a much larger displacement regime, and this action could help address collapse. A complete resistance function should adequately account for the catenary action as well as the arching effect. To this end, a generic catenary model which takes into consideration the strength degradation due to local failure events (e.g. rupture of bottom rebar or fracture of a steel weld) and the eventual failure limit is proposed. The application of the model in predicting the resistance function in beam assemblies with strength degradations is discussed. The validity of the proposed model is checked against predictions from finite element model and experimental tests. The result indicate that strength degradation can be accurately captured by the model. Finally, the above developed model framework is employed in investigative studies to demonstrate the application of the resistance functions in a dynamic analysis procedure, as well as the significance of the compressive arching effect and the catenary action in the progressive collapse resistance in different designs. The importance of an accurate prediction of the arching effect and the limiting displacement for the catenary action is highlighted.

Today, 3D modelling and structural analysis of buildings are performed in various software. Collaboration between various software is common today but breaks the flow in the construction design phase. To achieve an uninterrupted flow in the construction design phase, a constellation of modelling and structural analysis is needed in a single software. To enable a constellation, there are today many developed digital methods for this.Parametric design is a digital method that is mostly used to handle complex shapes. In recent years, the parametric design has evolved even more and the algorithmic thinking in parametric design provides opportunities for performing structural analyses. The development includes various plug-in programs that have structural analysis capabilities. However, this degree project emphasizes that this can be achieved without a plug-in program that has structural analysis capabilities. With only one visualization program and a plug-in that handles visual programming, the ability to produce what is to be visualized with a script arises.The structural analysis in this thesis includes robustness analysis that is important in the context of progressive collapse, and only the alternative load path method is considered. Progressive collapse is an important analysis for buildings that arise due to known or unknown accident loads. To increase the redundancy of the bearing structure, the alternative load path method can be used, which is a branch under unknown accident loads.Robustness analysis is a time-consuming process and automation can make this more efficient. With parameter-driven modelling and robustness analysis, the constructor can indicate at an early stage possible structure failure before the building is completed. Early action also leads to a reduction in waste of material resources.The alternative load path method provides the possibility to analyze whether the building receives alternate load path in the event of loss of load-bearing elements. This research report analyses column loss. Automated visualization of alternate load path enables to be able to analyze the load redistribution after the loss of column.Today some buildings are at risk against the progressive collapse, people's lives and health are therefore at risk when all or part of the building collapses. That is why efficiency is needed. The research report showed that the script automated the modelling and robustness analysis of buildings. Two different loss scenarios were analyzed and the authors found different updated loading areas and load redistribution.