Gantt Charts, Resources, and Earned Value

Gantt Charts

A Gantt chart is a time-scaled horizontal bar chart in which each activity is shown against its planned start, finish, and often its actual progress.

Illustrative Gantt chart for five activities over six weeks

Illustrative Gantt chart for five activities over six weeks

Advantages	Limitations
Easy for stakeholders to read	Dense projects can become visually complex
Communicates planned dates and overlap	Dependencies may be hidden unless explicit links are added
Supports progress and milestone tracking	A basic chart does not calculate the critical path
Useful for coordination and reporting	Resource conflicts are not automatically resolved
Can show baseline versus actual position	Frequent change requires disciplined updating and version control

Strengths and limitations of a Gantt chart

Feature	Gantt chart	CPM/PERT network
Visual basis	Time-scaled bars	Nodes and precedence arrows
Dependencies	Optional or less prominent	Explicit and central
Critical path	May be highlighted after calculation	Derived from the network
Best use	Communication and time tracking	Logical and quantitative analysis

Gantt and network views are complementary

Scheduling and Resource Adjustment

Project scheduling requires activity identification, duration estimation, precedence logic, resource assignment, calendar constraints, milestone setting, and a time-scaled baseline. A mathematically feasible network may still be impossible if two simultaneous activities demand the same unavailable resource.

Resource leveling adjusts activity timing to remove resource over-allocation. It can move activities beyond available float and therefore may extend the critical path and project completion date.

Resource smoothing shifts activities only within existing float so that a fixed project completion date is preserved. It improves the resource profile but may not remove every overload.

Method	Action	Likely effect
Delay non-critical work	Move an activity into unused float	Completion may remain unchanged
Activity splitting	Interrupt and resume work where technically feasible	More coordination and setup cost
Resource smoothing	Shift only within float	Deadline unchanged; overload may remain
Resource leveling	Reschedule according to constrained resource availability	Deadline may move
Add or substitute resources	Increase capacity, overtime, subcontract, or alter method	Higher cost or quality/risk implications

Methods for resolving resource conflicts

If activities B and C both require one crane in week 3, first compare their float and priority. Move the activity with usable float; if both are critical, add capacity, change sequence or method, or accept a later finish through formal change control.

Earned Value Management

Earned Value Management (EVM) integrates scope, schedule, and cost by expressing planned work, completed work, and actual expenditure in the same monetary units at a defined status date.

Measure	Formula	Interpretation
Planned value (PV)	Budgeted cost of scheduled work	Budgeted value of work planned by the status date
Earned value (EV)	Budgeted cost of work performed	Budgeted value of work actually completed
Actual cost (AC)	Actual cost of work performed	Cost actually incurred for completed work
Cost variance (CV)	$EV-AC$	Negative means over budget
Schedule variance (SV)	$EV-PV$	Negative means less work than planned
Cost performance index (CPI)	$EV/AC$	Below 1 means cost inefficiency
Schedule performance index (SPI)	$EV/PV$	Below 1 means behind the planned work rate

Core earned-value quantities and indicators

Example — Interpreting EVM indicators

At the status date, $PV=\text{Rs. }50{,}000$ , $EV=\text{Rs. }45{,}000$ , and $AC=\text{Rs. }55{,}000$ . Then

CV=45{,}000-55{,}000=-\text{Rs. }10{,}000, \qquad SV=45{,}000-50{,}000=-\text{Rs. }5{,}000,

CPI=\frac{45{,}000}{55{,}000}=0.818, \qquad SPI=\frac{45{,}000}{50{,}000}=0.90.

The project is over budget and behind the planned amount of work. A CPI of $0.818$ means each rupee spent has earned about Rs. 0.82 of budgeted value; it does not mean that 82% of the project is complete.

[!NOTE]

Key Point — EVM schedule caution

SV and SPI are value-based schedule indicators, not direct measures of days. Near completion, $SV$ tends toward zero even after earlier delay. Use the network schedule and critical-path forecast alongside EVM.