Calculator Inputs
Formula Used
Design lifted load: P = (rated load + hoist weight) × (1 + impact %) × load factor
Vertical reaction: V = P + crane self weight
Side reaction: H = P × side load %
Vertical moment: Mv = P × boom reach + self weight × eccentricity
Horizontal moment: Mh = H × boom reach
Resultant moment: M = √(Mv² + Mh²)
Anchor couple reaction: R = M ÷ vertical anchor spacing
Tension per anchor: T = R ÷ anchors active in tension
Resultant shear per anchor: S = √((V ÷ n)² + (H ÷ n)²)
Anchor tensile stress: ft = T ÷ net anchor area
Anchor shear stress: fv = S ÷ net anchor area
Plate bearing stress: fb = S ÷ (anchor diameter × plate thickness)
Base pressure: q = V ÷ A ± M ÷ Z
How to Use This Calculator
Enter the crane load, hoist weight, impact allowance, boom reach, and side load. Then enter the anchor group spacing, anchor count, anchor diameter, net area factor, plate thickness, and allowable stresses. Add base dimensions and concrete pressure limits. Press Calculate to show the result above the form.
Use CSV for spreadsheet review. Use PDF for a quick project record. Adjust one input at a time when comparing anchors, spacing, base size, or load limits.
Example Data Table
| Case | Load kN | Reach m | Spacing m | Anchors | Anchor Diameter mm |
|---|---|---|---|---|---|
| Light wall jib | 5 | 2 | 0.75 | 6 | 16 |
| Workshop jib | 10 | 3 | 1 | 8 | 20 |
| Heavy service jib | 20 | 4 | 1.25 | 12 | 24 |
About this Calculator
Anchorage Review
A jib crane anchor group must resist vertical load, side load, and overturning moment. This calculator gives a structured check for early design review. It estimates the load at the hook, adds impact, and converts that force into bracket reactions. The tool then divides tension and shear across the entered anchors. It also checks plate bearing and concrete base pressure.
Why Anchorage Reactions Matter
Anchorage failure can tilt the mast, crack concrete, or overload bolts. The largest force often comes from the moment created by load times reach. A small increase in boom length can raise anchor tension sharply. That is why the reach, bracket spacing, and anchor count are important. Wider spacing lowers the tension couple. More tension anchors reduce stress per anchor.
What the Results Show
The result table shows design hook load, vertical shear, horizontal side force, overturning moment, group tension, force per anchor, stress values, interaction ratio, and base pressure. A ratio below one means the entered stress limit is not exceeded. A ratio above one means the input set needs review. The calculator does not replace a stamped design. It helps compare options before final checking.
Practical Design Notes
Use service data from the crane supplier. Include hoist weight, trolley weight, and any required impact allowance. Enter realistic side load if the crane can pull or slew under load. Use net anchor area when threads reduce the section. Check embedment, edge distance, welds, grout, concrete breakout, fatigue, and local wall strength separately. For outdoor cranes, include wind where it controls.
Better Input Practice
Keep units consistent. Use kilonewtons, metres, millimetres, and megapascals. Do not mix pounds or inches unless converted first. If the concrete pressure minimum is negative, uplift is present. That may require hold-down design or a larger base. Save the CSV or PDF report with project notes.
Reading the Warning Line
The final status uses the limits entered in the form. It is a screening guide, not a code ruling. Change one input at a time to see the effect. Increase spacing, anchor size, or base size when ratios are high. Reduce reach or load when the crane layout allows it. Always document assumptions before procurement and site installation review.
FAQs
What is jib crane anchorage reaction?
It is the force transferred from the crane support into anchors, plates, concrete, or a wall. It includes vertical load, side load, shear, and moment effects from the lifted load and boom reach.
Why does boom reach affect anchor stress?
Boom reach creates overturning moment. A longer reach increases moment even when the lifted load stays the same. Higher moment raises the tension and compression couple in the anchor group.
What is the anchor couple reaction?
It is the moment divided by the vertical spacing between reaction levels. This value estimates the tension group and compression group force needed to resist overturning.
What does a stress ratio above one mean?
A ratio above one means the calculated stress exceeds the allowable limit entered in the form. Increase anchor size, anchor count, spacing, plate thickness, or reduce the design load.
Why is net anchor area used?
Threads and reductions can lower the effective steel area. The net area factor lets you reduce the gross round area for a more careful tensile and shear stress estimate.
What does negative base pressure mean?
Negative minimum pressure means uplift is predicted at one side of the base. The anchorage may need hold-down resistance, a larger base, or a different support arrangement.
Can this calculator design anchor embedment?
No. It estimates reactions and basic stresses. Embedment, pullout, concrete breakout, edge distance, pry action, welds, and fatigue need separate code-based checks.
Should final crane anchorage be engineered?
Yes. Crane anchorage is safety critical. Use this calculator for planning, comparison, and documentation. Final design should be reviewed by a qualified structural engineer.