Phase Planning (4D)
Mô phỏng tiến độ (4D)
Link the 3D model with schedule data (WBS) to visually simulate the construction sequence, detect schedule conflicts, and optimize construction methodology.
Common tools
Revit, Navisworks TimeLiner, Forma Data Management
Value delivered
Common at major Vietnamese contractors; required in many international tenders
Adoption in Vietnam
Gained traction in Vietnam from 2018–2020 driven by FDI projects and industrial zone requirements.
Level of Information Need (LOIN)
G = Geometry · A = Alphanumeric · D = Documentation (ISO 7817-1:2024 method). A blank cell means this use sets no specific requirement for that discipline/stage.
| Discipline | Concept | Schematic | Developed | Technical | As-built / Operation |
|---|---|---|---|---|---|
| Architecture | — | G2·A1·D0 | G3·A1·D0 | G3·A2·D1 | — |
| Structure | — | G2·A1·D0 | G3·A1·D0 | G3·A2·D1 | — |
| Mechanical | — | — | — | G3·A1·D0 | — |
| Electrical | — | — | — | G3·A1·D0 | — |
| Plumbing | — | — | — | G3·A1·D0 | — |
Critical stages: Schematic · Developed · Technical
Rationale: 4D = geometry + time. Primary structural/arch elements drive sequence visualisation; G2→G3 as the WBS firms up. A1 carries phase/status/zone attributes (Existing / Demolition / New / Temporary). A2 + D1 at ST4 link schedule and progress data. MEP enters at ST4 only for construction-phase sequencing.
What it really is
4D links 3D model objects to schedule tasks to visually simulate the construction sequence over time. Each task is mapped to a set of objects; running the simulation shows the building rising along the programme and allows planned to be compared with actual. Unlike a Gantt chart divorced from the model — where the reader must imagine the space — 4D bridges programme and model visually, exposing space–time conflicts before they reach site: two crews in the same zone, a crane path crossing an active work area. The value is not the polished video but the times the sequence had to be changed after watching it.
When to use
Worthwhile for Grade II and above works, multi-phase or congested-site projects such as high-rises, infrastructure and large FDI projects, and projects with high delay risk. Maintain the 4D model from preconstruction through to completion — built once and abandoned, it retains only presentational value.
Prerequisites
- •A coordinated model completed and through basic clash coordination
- •A construction schedule with consistent task identifiers
- •Model objects carrying identifiers or properties sufficient to build search sets linking to tasks
- •A planner skilled in both scheduling and model linking — lacking either, the 4D model will not reflect the real construction method
- •A BEP or contract defining the LOIN and 4D scope (Art. 8(2))
Inputs
Task team · .rvt / IFC / .nwc
Lead appointed party · .mpp / .xer / .csv
Lead appointed party · .xlsx
Appointing party · .pdf
Lead appointed party · .pdf / .dwg
Lead appointed party · .pdf
Outputs
4D model linked to the schedule
.nwd → Appointing party · lead appointed party
Accepted when: Every task linked to the right objects, the simulation runs the full project lifecycle, no orphaned objects remain
Sequence simulation video
.avi / .mp4 → Appointing party
Accepted when: Reflects the approved phase sequence
Space–time conflict report
.pdf → Lead appointed party
Accepted when: Lists each conflict with its resolution, not just screenshots
Planned versus actual comparison
.nwd / .pdf → Lead appointed party
Accepted when: Updated against site progress at the agreed frequency
General workflow
Federate the coordinated model
Append discipline models into one federated model, verify the shared origin, and create cache files so the simulation runs smoothly on a large model.
Task team · lead appointed party · Navisworks Manage → Federated model
Build or import the schedule
Build the schedule with consistent task identifiers. The industry-standard planning tools are Primavera P6 and Microsoft Project; where neither is used, TimeLiner can create and edit tasks directly.
Lead appointed party · Navisworks TimeLiner · Primavera P6 or Microsoft Project → Construction schedule
Import the schedule into TimeLiner
Add the schedule data source, map columns to the corresponding fields, then rebuild the task hierarchy to verify the import before attaching objects.
Lead appointed party · Navisworks TimeLiner → Imported tasks
Build search sets and attach tasks
Use dynamic search sets based on object properties rather than static selection sets — dynamic sets update when the model changes, static ones do not, which is the most common reason a 4D model goes stale within weeks.
Lead appointed party · Navisworks TimeLiner → Task-to-object links
Run the simulation and review the sequence
Run the simulation to find space–time conflicts. TimeLiner can be linked to the clash tool to detect time-based clashes rather than relying on visual review alone.
Lead appointed party · Navisworks TimeLiner · Navisworks Clash Detective → Space–time conflict report
Optimise the sequence and export the simulation
Adjust the sequence and method based on what the simulation revealed, then export a video to communicate the plan to parties who cannot read a programme.
Lead appointed party · Navisworks TimeLiner → 4D simulation video
Share and track actual progress
Store the 4D model on the CDE and update actual against planned as site progresses, so the model stays useful through construction rather than ending at the approval submission.
Appointing party · lead appointed party · Forma Data Management (CDE) · Forma Build → Updated 4D model
Diagram
↺ Site actuals feed back into the simulation to compare planned with actual
Common pitfalls
Tasks cannot be linked to any objects
Cause: Task identifiers and object properties do not follow a common convention
Fix: Standardise the coding rules and use dynamic search sets rather than static selection sets
The simulation does not reflect the real construction method
Cause: The schedule was built in isolation, without breakdown by phase and work zone
Fix: The planner works directly with the BIM team to break tasks down by zone and phase
The 4D model goes stale within weeks
Cause: Not updated when design or schedule changes, compounded by static selection sets
Fix: Manage versions on the CDE and use dynamic search sets so model changes are picked up automatically
Space–time conflicts are missed
Cause: Review relies on watching the simulation by eye
Fix: Link TimeLiner to the clash tool to detect time-based clashes
Stakeholders still do not understand the construction plan
Cause: Only a bar-chart programme was presented
Fix: Export a 4D simulation video to communicate visually with non-technical parties
Measuring effectiveness
Compare delay on projects with and without 4D
Benchmark: Studies report a very wide range, from 7% to 67%. Read it as a range, not a figure: measurement methods differ substantially between studies
Compare delivery time across case studies with and without BIM
Benchmark: About 20% on average in a multi-case synthesis. Note this is the effect of BIM overall, not 4D's isolated contribution
Count conflicts found during preconstruction through time-based clash checks
Benchmark: no independent benchmark — set an internal target
Legal basis
There is NO specific requirement for BIM-based scheduling or 4D simulation in Decree 217/2026/NĐ-CP — 4D falls under Article 8 generally. Art. 8(1)(a) makes BIM mandatory from Grade II; Art. 8(2) assigns scope, content and information requirements to the contract, the basis for bringing 4D into scope and setting the LOIN; Art. 8(4) requires a CDE to be established and operated for Grade I+ public-investment works, where the 4D model is stored and shared; Art. 8(5) allows the authority to use BIM data to support appraisal, including checking technical conflicts. Progress-tracking provisions in Decree 210/2026/NĐ-CP only encourage digital platforms rather than mandating 4D. The practical consequence: like 5D, 4D is a CONTRACTUAL obligation — if you want it, write it into the EIR and BEP.
Sources
Only official sources (legislation, standards) and peer-reviewed academic work are cited. No vendor marketing figures or press sources. Reference only — does not replace legal advice.