- Watch out
- What it costs
- Experienced readers
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- In BIMpedia
A 4D model links the programme to the model: play it and you watch the building go up. Most teams use it to check logic and progress. It's just as good for safety, because the same model shows who is working where, and what is above them, week by week.
The programme has the zone B roof slab starting four days before the zone B frame below it is finished. Nobody plays the 4D model with safety in mind. On the day, the slab crew is placing decking above steel erectors who are still bolting beams. A dropped tool injures a worker.
In the weekly look-ahead, the safety advisor plays the next two weeks zone by zone. The 4D Simulator already flags the roof slab as "planned before what carries it". The planner moves the slab back a week; the site manager adds an exclusion zone under the decking crew for the overlap that remains.
What to look for, week by week
- 1Agree the breakdownLevels, zones, pours and work packages
- 2Code the programmeEach activity gets a code: L03-Z1-FRAME
- 3Code the modelElements carry level, zone and package properties
- 4Link by rulesActivity ↔ elements with matching codes
- 5Play and checkLogic, workspaces, logistics, every update
| Look for | Why it matters | Typical fix |
|---|---|---|
| Work stacked over other work | Falling objects onto the lower crew | Re-sequence, or protection and an exclusion zone |
| Loads lifted over people or entrances | Dropped loads | Change the lift path or the timing |
| Open edges and openings | Falls | Edge protection before the next trade arrives |
| Several trades in one small zone | Congestion, plant moving near people | Stagger the work |
A 4D model links model elements to programme activities, so the model can show what exists on any date. On BIMpedia, the 4D Simulator plays the programme on the model and checks the sequence (elements planned before the structure under them is finished).
Open the 4D Simulator on the sample and press Play.
- Find the sequence problem the Problems panel reports. Who would be at risk, and how?
- Pick a date between 8 and 12 May. Which zone has work under way on two levels at once?
- Propose one change to the programme and one control on site.
Key takeaways
- Look at each week of the 4D model for people, not just elements: who works where, and what is above them.
- Stacked trades, lifts over occupied areas and open edges show up clearly when you play the programme.
- Each problem found becomes a change to the sequence, a temporary work, or an exclusion zone in the logistics model.
- Review the 4D model with the site manager and the safety advisor before each look-ahead.
Your notes
Related tool
Play the programme on the IFC model: see it built day by day, find late work and sequence errors.
Open 4D Simulator →