Clash Detection DR FAROOK HAMZEH ASSISTANT PROFESSOR CIVIL

Clash Detection DR. FAROOK HAMZEH ASSISTANT PROFESSOR, CIVIL & ENVIRONMENTAL ENGINEERING AMERICAN UNIVERSITY OF BEIRUT

What is a Clash? In design terms, a clash occurs when components that make up a built asset are not spatially coordinated and conflict. In a BIM process these clashes can be spotted more easily during the design phase of a project ahead of work starting on site. (Mc. Partland, 2016) 2

Most clash detection is performed manually by overlaying individual system drawings on a light table to identify potential conflicts. Traditional Clash Detection Contractors use traditional 2 D - CAD tools to overlay CAD layers to visually and manually identify potential conflicts. If the 3 D geometries are not solids. the clash detection tool cannot detect clashes between objects within other objects. It can only detect clashes between surfaces. Qualification of clashes into meaningful categories for the contractor is greatly inhibited due to lack of semantic information embedded in the 3 D geometry models. A clash between surfaces could be a wall abutting a wall or a pipe running through a wall. The contractor has to verify and review each of these potential clashes. These manual approaches are slow, costly, prone to error, and depend on the use of up - to - date drawings. (Eastman et al. , 2011) 3

BIM Clash Detection BIM - based clash detection tools allow automatic geometry based clash detection to be combined with semantic and rule - based clash analysis for identifying qualified and structured clashes. BIM - based clash detection tools allow contractors to selectively check clashes between specified systems, such as checking for clashes between mechanical and structural systems, because each component in the model is associated with a specific type of system. Consequently, the clash detection process can be performed at any level of detail and across any number of building systems and trades. (Eastman et al. , 2011) 4

Types of Clashes Hard Clash One building component physically yet unintentionally penetrating another building component; that is, two or more components compete for the same physical space. (Tommelein and Gholami, 2012) Soft Clash Time Clash Components (subsystems) that are closer than a certain distance (a minimum clearance) from one another (e. g. , distance in-between outer cylindrical surfaces of two pipes). Spatial challenges (components potentially occupying the same space) anticipated when considering constructability or operability of the facility. A time clash may be modelled as a kind of clearance requirement, but one that has a temporal component to it. 5

The possibility to identify most design conflicts prior to construction. Benefits of BIM Based Clash Detection Improved productivity during construction. Less rework. Increased opportunity for pre-fabrication. Fewer requests for information. Fewer change orders. The possibility to identify design errors prior to construction. The ability to build systems with a less skilled labor force. Improved safety performance. Better cost control. (Hartmann, 2010) 6

Clash Detection process – Design Phase (Seo et al. , 2012) 7

Clash Detection process – Construction Phase (Seo et al. , 2012) 8

Causes of Hard Clashes Design uncertainty. Failing of design rules. Design complexity. Balancing effort in resolving the dilemma between model accuracy vs. meeting a deadline. Design error. (Tommelein and Gholami, 2012) 9

Causes of Soft & Time Clashes Soft Clashes arise when blocked out spaces of objects overlap with each other. Block-outs are used to save time on modeling, define construction or operation concerns and construction tolerances or clearances. Time Clashes happens from errors in deriving the construction and operation sequencing. (Tommelein and Gholami, 2012) 10

Process for the Establishment of a Collaborative System Improvement plan for the current clash detection Participation of general contractor in the design phase Expansion of participants and participation in an early phase Specification of working process and addition of an activity Setting up a BPMN-based collaboration system for clash detection (Seo et al. , 2012) 11

Clash detection process BPMN diagram (Seo et al. , 2012) 12

Systemic framework for error containment and reduction (Love et al. , 2011) 13