Enter support works data
Use metric values. Confirm final designs with project drawings and supplier tables.
Formula used
Tributary area: A = length × width.
Self weight: W = A × thickness × material density.
Dead load: D = self weight + added dead load + equipment line load × loaded length.
Live load: L = tributary live load + point load allowance.
Factored vertical demand: V = ((D × dead factor × levels) + (L × live factor)) × dynamic factor × condition factor ÷ load sharing.
Per support demand: P = factored vertical demand ÷ number of supports.
Axial demand: Pa = P ÷ cos(angle from vertical).
Bearing pressure: q = P ÷ base plate area.
Available safety factor: smaller support or bearing capacity ÷ factored demand per support.
How to use this calculator
- Enter the tributary length and width supported by the temporary system.
- Add slab thickness, density, dead load, live load, line load, and point load.
- Enter the number of props, shores, tower legs, or frame supports.
- Set load factors, dynamic factor, condition factor, and sharing efficiency.
- Add capacity, brace angle, eccentricity, plate size, and bearing pressure.
- Press the calculate button. Review the status, minimum support count, and warnings.
- Download the CSV or PDF report for checking notes and field records.
Example data table
| Input | Example value | Purpose |
|---|---|---|
| Tributary area | 6.00 m × 4.00 m | Defines supported plan area. |
| Slab thickness | 150 mm | Calculates self weight. |
| Construction live load | 2.50 kN/m² | Allows workers, tools, and movement. |
| Support count | 12 supports | Divides the factored vertical demand. |
| Rated capacity | 35 kN per support | Checks capacity against demand. |
| Base plate | 300 mm × 300 mm | Checks bearing pressure below each support. |
Support Works Load Planning
Support works carry temporary loads before the permanent structure works alone. The load path must be clear. Each prop, shore, frame, or tower takes a share from the slab, beam, wall, platform, or formwork. This calculator starts with a tributary area. It adds self weight, dead load, live load, equipment load, and point load. The result helps planners compare demand against rated support capacity.
Why Load Checks Matter
Temporary failures can happen during pouring, storage, repair, demolition, or staged construction. Loads may change quickly. Wet concrete is heavy. Workers and tools add movement. Pumps, carts, and stored materials can create local pressure. A safe check should include realistic factors, not only ideal service loads. The tool lets you change dead load factor, live load factor, dynamic factor, and condition factor. These controls help cover poor alignment, reused equipment, impact, and uneven sharing.
Understanding Support Demand
The calculated vertical load is divided by the number of supports. A brace angle increases axial demand because the support no longer acts perfectly vertical. Eccentricity creates a moment at the head or base. Bearing pressure checks whether the base plate can spread load into timber, concrete, soil, or platform decking. Lateral load is estimated as a percentage of factored vertical load. This helps plan ties and braces.
Using Results On Site
Use the output as a planning guide. Compare it with supplier tables and project drawings. Confirm prop height, extension, pin position, head plate, base plate, and bracing rules. Rated capacity often reduces when extensions increase. Weak ground can control the design before the prop reaches its strength. Add more supports when the factor of safety is low. Increase plate size when bearing pressure is high.
Professional Review
Support works are temporary, but they are critical. Site conditions can change after rain, vibration, excavation, or extra storage. The calculator cannot replace engineered drawings. It helps estimate early loads and find weak points. Final support layouts should be checked by a qualified person before work begins. Keep calculations with inspection records and update them when loads change.
Design Records
Record each assumption, drawing note, load case, and selected capacity. Clear records make review faster. They also help crews understand why a support, brace, or base plate was chosen during each shift.
Frequently asked questions
What is a support works load?
It is the temporary load carried by props, shores, towers, frames, jacks, or braces during construction. It may include wet concrete, formwork, workers, tools, equipment, stored materials, and local point loads.
Is this calculator for permanent structural design?
No. It supports temporary planning checks. Permanent beams, columns, slabs, and foundations need code design, full load combinations, material checks, and approval by a qualified professional.
What does tributary area mean?
Tributary area is the portion of slab, deck, platform, or formwork assigned to the support group. Multiply the supported length by supported width to estimate area load.
Why does brace angle matter?
A support that is not vertical carries higher axial force for the same vertical load. The calculator divides per support load by cosine of the entered angle.
How is bearing pressure checked?
The factored load per support is divided by base plate area. The result is compared with the allowable bearing pressure entered for soil, timber mats, decking, or concrete.
What is load sharing efficiency?
Load sharing efficiency allows for uneven settlement, height differences, plate gaps, and imperfect installation. A lower value increases calculated demand and creates a more conservative check.
Should I include equipment loads?
Yes. Pumps, carts, hoists, stacked materials, and temporary platforms can produce major local loads. Include line loads and point loads when they act inside the supported area.
What factor of safety should I use?
Use the value required by your project documents, local rules, equipment supplier, or engineer. Temporary works often need conservative margins because site conditions change quickly.
Why can bearing control the result?
A strong prop can still fail the layout if the base plate is too small. Weak ground, soft timber, or thin decking can limit safe support load.
Can this handle stacked supported levels?
Yes. Enter the number of stacked levels. The calculator multiplies dead load by that value. Review actual load paths when multiple floors are reshored or backpropped.
Do I still need a field inspection?
Yes. Inspect plumbness, pins, collars, bracing, base support, settlement, damaged members, and changed loads. Calculations only help when the installed system matches assumptions.