Origins and probabilities of MEP and structural design clashes within a federated BIM model

'Design clashes' encountered during the development of a large multi-storey educational building, awarded under a Joint Contracts Tribunal (JCT) Design and Build contract, are reported upon. The building was developed in Birmingham, UK and the contract value was circa £36 million (UK Sterling, 2015). Members of the project management team (PMT) produced designs that were subsequently integrated by the main contractor into a federated building information modelling (BIM) model; at this stage 404 error clashes were evident between the positions of the mechanical, electrical and plumbing (MEP) designer's and structural designer's building compartments. The contractor deemed that these particular clashes were 'mission critical' as previous experience suggested that project costs could spiral uncontrollably if left unabated. Participatory action research was employed to acquire a deeper understanding and knowledge of the clash incidents. Clash data accrued (in mm) was subsequently quantitatively modelled using the probability density function (PDF) and the cumulative distribution function (CDF). Two models produced were the Log Logistic Three Parameter (3P) (using all data including outliers) and Generalized Gamma distribution (excluding outliers). Both models satisfied Anderson-Darling and Kolmogorov-Smirnov goodness of fit tests at α 0.01 and 0.02 levels of significance. Model parameters could be used to forecast similar clashes occurring on future projects and will prove invaluable to PMT members when accurately estimating the time and resource needed to integrate BIM designs. The predictive modelling revealed that 92.98% of clashes reside within the 30-299 mm range while the most probable occurrence of a clash overlap resides in a discrete category of 100-199 mm. Further qualitative investigation is also conducted to understand why these clashes occurred and propagate ideas about how such may be mitigated. The research concludes on two important points, namely: i) BIM is not a panacea to design related construction project rework and that innovative 21st century digital technologies are hampered by 20th century management practices; and ii) improvements in clash and error mitigation reside in a better understanding of tolerances specified to alleviate the erroneous task of resolving unnecessary clashes. Future research is proposed that seeks to: automate the clash detection management, analysis and resolution process; conduct further investigative analysis of the organizational and human resource management influences impacting upon design clash propagation; and devise and validate new procedural methods to mitigate clash occurrence using a real-life project.