Module 3: Handling, Transportation & Erection
3.1 Logistics Planning
Efficient logistics are critical for transporting and erecting precast concrete elements safely and cost-effectively. Poor planning can lead to delays, damage, or structural failures.
Lifting Analysis:
Pick Points:
Designed during fabrication with embedded lifting inserts or loops.
Must align with the element’s center of gravity to prevent tilting.
Rigging Configurations:
Single-Point Lifts: Used for balanced elements (e.g., wall panels).
Multi-Point Lifts: For asymmetrical pieces (e.g., L-shaped stairs).
Spreaders: Prevent sling damage and ensure even load distribution.
Lifting Force Calculations:
Dynamic load factors (typically 1.5–2.0× dead load) account for acceleration/deceleration.
Transport Regulations:
Oversized Load Permits: Required for elements exceeding standard trailer dimensions (width > 3.5m, height > 4.3m).
Route Surveys: Check for low bridges, sharp turns, or weak roads.
Securement Standards:
EN 12195-1 (Europe) / FMCSA (USA): Chains, straps, and blocking prevent shifting.
Abrasion Protection: Rubber padding at contact points.
3.2 On-Site Installation
Proper installation ensures structural integrity and alignment while minimizing on-site risks.
Crane Selection & Stability:
Load Charts: Determine crane capacity based on boom length, radius, and counterweights.
Ground Bearing Pressure: Mats or cribbing distribute loads on soft soils.
Wind Speed Limits: Operations halt at > 32 km/h (20 mph) to prevent swinging.
Temporary Bracing & Alignment:
Adjustable Props & Braces: Hold walls/columns plumb until permanent connections are made.
Shims & Leveling Grout: Fine-tune alignment before grouting.
Laser Surveying: Verifies position within ±3 mm tolerance.
Connection Sequencing:
Shear Walls: Erected before beams/slabs to stabilize the frame.
Progressive Anchoring: Bolts tightened in stages to avoid distortion.
3.3 Safety & Risk Assessment
Precast erection is high-risk; fatalities occur from falls, collapses, or equipment failures.
Common Hazards & Mitigation:
Falling Elements:
Cause: Slipped rigging or sudden wind gusts.
Prevention: Taglines to guide loads, exclusion zones below lifts.
Structural Collapse:
Cause: Inadequate bracing or premature removal of supports.
Prevention: Engineer-signed bracing plans, "hold points" in inspections.
Worker Falls:
Cause: Unprotected edges during decking installation.
Prevention: Guardrails, safety nets, or personal fall arrest systems (PFAS).
Case Studies & Lessons:
2008 Dubai Crane Collapse:
Cause: Overloading in high winds.
Lesson: Stricter wind protocols and real-time load monitoring.
2016 Melbourne Wall Panel Failure:
Cause: Insufficient temporary bracing.
Lesson: Mandatory peer reviews of erection plans.
Toolbox Talks: Daily briefings on lift plans, emergency procedures, and PPE checks.
Key Takeaways
Logistics: Pick points and transport permits are as vital as design.
Installation: Crane stability and bracing dictate success.
Safety: Most accidents stem from procedural lapses—rigorous planning saves lives.
Best Practice Example: A UK contractor reduced erection time by 30% using RFID tags on precast units for real-time tracking.
.svg)
