👉DIFFERENCE BETWEEN PERT AND CPM

➡PERT and CPM are most commonly used methods for project management.

➡️In this article, we will discuss the differences between PERT and CPM.

🚧WHAT IS PERT?

➡️PERT or Programme Evaluation and Review
Technique is an event oriented method of network planning. In it, the emphasis is focused on start and completion events rather than on activities.

➡️The activities taking place between events are not specified.

➡️In PERT network, the events fall in logical
sequence But the logic of events may be different
for different planners. Hence PERT network may
vary from planner to planner depending upon their decision as which event to precede or occur
concurrently.

➡️In PERT network the start circle is omitted and only the completed event is recorded.

➡️PERT helps in identifying critical area which threatens the completion of the work.

➡️It provides the means to
determine how resources can be transferred from
one job to another job.

🚧WHAT IS CPM?

➡️CPM is also network comprising events and
activities.

➡️This network is activity based.

➡️The activities are represented by arrowed lines and events by circles.

➡️The activities are connected in logical sequence.

➡️The time allotted to each activity is related to cost.

🚧DIFFERENCE BETWEEN PERT AND CPM

🏷1. PERT is event oriented whereas CPM is activity oriented.
▶️In simple words, in PERT network interest is focused upon start or completion of events and
not on activities themselves.

🏷2. In CPM network no allowance is made for
uncertainties in the duration of time involved
whereas in PERT network uncertainty is considered.

🏷3. In PERT, time is not related to cost whereas in
CPM the object is to develop an optimum time
cost relationship. However, PERT has since been
extended in this direction and the line dividing
PERT/CPM is gradually fading out.

🏷4. In CPM duration of activity is estimated with a
fair degree of accuracy. In PERT duration of
activities are not so accurate and definite.

🏷5. In CPM both time and cost can be controlled
during planning. Pert is basically a tool for
planning

🏷6. PERT is used in research and development
project, basically for non-repetitive type projects.
CPM is widely used in construction projects.

#PERT

#CPM

#ConstructionPlanning

@etconp

👉PERT (Project/Programme Evaluation and Review Technique)

➡️Event oriented
➡️Probabilistic approach
➡️3 time estimates
(optimistic, pessimistic and most likely)
➡️Follows Beta distribution curve
➡️Time is only controlling factor
➡️Critical events may be +ve, -ve or zero
➡️Recommended for research, development and new projects.

👉CPM (Critical Path Method)

🚧Activity oriented
🚧Deterministic approach
🚧Only 1 time estimate
🚧Normal distribution
🚧Time and cost both are controlling factors
🚧Critical events must have zero slack
🚧Recommended for repetitive nature of work.

👉Errors in Network
(2 Types)

▶️Constructional Error
▶️Conceptual Error

🏷Constructional Error
(2 Types)
⏺Looping error ( Diagram form a loop )
⏺Dangling Error ( One or more activities have no effect on project time)

🏷Conceptual Error
(1 Type)
*⃣Wagon Wheel Error ( Logical error is present )

#PERT

#CPM

#ConstructionPlanning

@etconp

👉PROJECT SCHEDULING IN A NUTSHELL

🕓 PERT (Program Evaluation & Review Technique)
Used when activity durations are uncertain.

⭐️It uses three time estimates:

• ⚡ Optimistic (O)
• ⚙️ Most Likely (M)
• 🐢 Pessimistic (P)
Formula → Te = (O + 4M + P) / 6

🎲Helps predict project duration and risk of delay.

🧭 CPM (Critical Path Method)
Used when durations are known.
It finds the longest path in the project network — called the Critical Path.
Any delay on this path = delay in the entire project!

📅 Scheduling Steps

1️⃣ List all activities.
2️⃣ Estimate duration & sequence.
3️⃣ Draw a network (PERT/CPM chart).
4️⃣ Identify the critical path.
5️⃣ Track progress using Gantt Chart, Primavera, or MS Project.

💡 Critical Path = Project Lifeline
💡 PERT = Handle Uncertainty

#ProjectManagement #CivilEngineering #PERT #CPM #ConstructionPlanning

@etconp

👉Understanding Ribbed Slab Load Transfer Why Beams Look "Oversized"

💫Ever been on-site and noticed this?

✨ Girders wider than the columns, or
✨ Beams that look too wide compared to their depth...
Especially in ribbed slab systems?

🚧It’s not poor design it’s a structural necessity. Here’s why 👇

🔄 Load Transfer in Ribbed Slabs Unlike solid slabs, ribbed slabs (also called waffle or voided slabs) follow this path:

📍Topping Slab ➡️ Ribs ➡️ Beams ➡️ Girders ➡️ Columns

📌 Unlike solid slab systems that transfer loads more uniformly in both directions, ribbed slabs concentrate loads along the ribs.

⏺These ribs act like joists, channeling loads directly to secondary beams, which then deliver the concentrated forces to the main girders.

💡 So why do girders appear wider?

📜Because they’re receiving multiple concentrated point loads from the ribs.

✅To spread these loads and avoid punching shear or localized failures, the girder's width will be increased, sometimes even wider than the supporting columns.

🚧Also, these wider beams may appear shallow compared to typical T-beams under solid slabs, but their width ensures:

✅ Better load distribution
✅ Reduced deflection
✅ Efficient rib anchorage

🔰Why Use Ribbed Slabs?

✅ Lighter dead load
✅ Material savings (less concrete)
✅ Longer span capability
✅ Easier MEP integration
✅ Better thermal & sound insulation
✅ Cost-effective for repetitive layouts

#SiteEngineering #StructuralClarity #RibbedSlab #ConstructionPlanning #LoadTransferLogic #ConstructionBasics  #BuildSmart #CivilEngineering #MasonryWorks #OnSiteLearning #EthiopianConstruction #Ethioconstruction

@etconp

👉Topographic Surveying

📍 Purpose

- Accurate land maps – essential for planning and documentation.
- Determine elevations – helps in slope analysis and drainage design.
- Support design & construction – ensures structures fit the terrain.
- Land development planning – guides zoning and infrastructure layout.
- Resource management – aids in sustainable use of land and water.

⚙️ Equipment

- Total Station – measures angles and distances.
- GPS Receiver – provides precise coordinates.
- Level – determines height differences.
- Tripod – stabilizes instruments.
- Data Collector – stores field measurements.

🛠️ Process

1. Plan the survey – define objectives and scope.
2. Establish control points – reference markers for accuracy.
3. Collect field data – record terrain features.
4. Process the data – convert raw data into usable form.
5. Create the topographic map – visualize contours and elevations.
6. Deliver final results – provide maps, models, and reports.

📊 Data Collection

- Control Points – fixed references.
- Elevation Data – height information.
- Natural & Man-Made Features – rivers, roads, buildings.

🗺️ Output

- Contour Maps – show terrain slopes.
- Spot Elevations – specific height points.
- 3D Terrain Models – digital visualization.
- Site Plans – detailed layouts for construction.

📝 Notes

Accurate surveys are critical for safe design, cost estimation, and successful construction projects.

#TopographicSurveying #CivilEngineering #LandDevelopment #ConstructionPlanning #SurveyEquipment #ContourMapping #3DTerrain #SitePlans #EngineeringEducation #CivilTechTime

@etconp

👉Block Quantity Calculations

- Block size: Standard block is 400 × 200 × 200 mm, but with 10 mm mortar joint, nominal size becomes 410 × 210 × 210 mm.
- 1 m² blockwork: A wall of 1.0 m × 1.0 m requires ≈ 12.5 blocks (for 200 mm thick wall).
- 1 m³ blockwork: A cube of 1.0 m × 1.0 m × 1.0 m requires ≈ 55 blocks.
- Mortar joint consideration: Always include 10 mm mortar joint in nominal size calculations.
- Variation in quantity: Block requirement may differ slightly depending on site conditions and workmanship.
- Extra allowance: Add 5–10% extra blocks to cover cutting, breakage, and wastage.
- Practical application: For a 10 m² wall, ≈ 125 blocks are needed, plus wastage allowance (≈ 135–140 blocks).
- Construction planning: These calculations help in budgeting, procurement, and avoiding shortages during masonry work.

#BlockWork
#ConstructionPlanning #MasonryDesign #QuantityEstimation #BuildingMaterials #SiteManagement #StructuralDetails

@etconp