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Where Does CPM And 2D Fit In The Digital Construction Age?

April 2019

Construction companies began adopting CPM in the late 1950s and early 1960s. Critical Path Method (CPM) is project modelling technique developed in the late 1950s. By the late 1970’s and early 1980s, the personal computer made CPM affordable and accessible to the masses; so how has construction performance fared since CPM became the standard for construction planning and scheduling? For years, we have all seen the numbers and charts put up for debate showing no evidence that the original hopes and excitement of CPM is living up to its original expectation.

In construction, the CPM model is based on the input of individuals who use personal experience and historic project performance to inform their work. People must read 2D design documents showing what the project looks like first at the start (existing conditions) and what the finished project will be on completion.

To be clear, the construction delivery approach, the field operations plan, is created from the imagination of a person(s) who is required to envision the activities, duration, and dependencies of the specific project from seeing the existing conditions at the start and the construction design for the completed project at the end. Once created, they can review the delivery approach with others using the Gantt chart or network diagram.

It will never going to be enough to improve construction performance if CPM alone. Project today are more likely to end in a dispute or claim rather than be completed on time or on budget, lawyers love the baseline versus actual CPM artefacts to help sort out the mess. CPM should remain part of the foundation for planning, scheduling and the controls systems required for managing construction operations and it will continue to be required for the foreseeable future.

How can we improve performance?

Start by recognizing that 3D design changes everything and drives complexity, and for at least 60 years all engineering lead industries have known it. BIM is organised and structured by 3D spatial model. Today, many construction projects utilize 3D models for the final integrated product design’s spatial coordination to avoid fabricating and installing any component in the wrong location before production operations begin.

When it comes to 4D, the industry falsely led to believe that creating a schedule by reading 2D drawings and keyboarding into the legacy CPM software and then linking the CPM to the 3D model is right. SYNCHRO Software is doing 4D. Creating construction operations directly from 3D model at any level of 3D model detail is where 4D is the best. The critical path network and 2D documents are the derivative, they are outputs of 4D. 4D leads construction companies’s workflow and has envolved their construction management processes into the modern digital age.