Impact and machinery loads

The live load with impact of one source, by ASCE/SEI 7-22 4.6 and 4.9. The sources are:

• Elevators: the ASME A17.1 pointer of 4.6.2.
• Machinery: 20 % or 50 % impact (4.6.3).
• Hoists for facade access and building maintenance: 2.5 times the rated load or the stall load (4.6.4).
• Crane runways: vertical impact by crane type and service class (4.9.3), and the lateral and longitudinal forces (4.9.4, 4.9.5).

The calculation gives the loads as live loads L with their factored values. It is an analysis: the result reads Calculated. Fall-arrest anchorages (4.6.5) are their own type, Fall-protection anchorage.

Inputs of the impact loads #

• Source:
  • Elevator.
  • Light machinery, shaft- or motor-driven.
  • Reciprocating machinery or power-driven units.
  • Hoist.
  • Powered monorail crane.
  • Bridge crane of service class D to F, or of A to C.
  • Hand-geared crane.

  Assign the bridge crane service class from the actual service (4.9.3.1).

• Static load P: depends on the source:
  • elevator: the supplier's static reaction;
  • machinery: the weight of the machinery and moving loads;
  • hoist: the rated load;
  • crane: the maximum wheel load of 4.9.2.
• Elevator: whether the reactions already include the A17.1 impact. If they do not, they are doubled (C4.6: A17.1 includes the 100 % impact factor).
• Larger impact allowance:
  • Machinery: the manufacturer's percentage where it exceeds the code's (4.6.3).
  • Cranes: a larger value you choose.

  A value below the code's is never used.

• Hoist: the stall load.
• Crane:
  • The rated capacity and the hoist and trolley weight.
  • Whether the trolley is electrically powered (4.9.4).
  • The number of wheels.
  • The share of the lateral force taken by the runway considered (4.9.4: by the runways' lateral stiffness, 50 % for equal runways).
  • Whether the bridge is hand-geared (no longitudinal force, 4.9.5).

Checks performed #

The drawing shows a schematic supporting member with the load and, for cranes, the lateral force.

Limitations #

• Elevators. ASME A17.1 is not on disk. The buffer, safety and rail load cases and the deflection limits are the supplier's and A17.1's, entered as reactions (to confirm against the code text).
• One source per calculation. The supporting member, its connections and its deflection are not designed here. The crane runway beam has its own type.
• Load cases. The crane forces are given separately. Combining the vertical impact, lateral and longitudinal forces in load cases (AISC Design Guide 7) is the engineer's work.
• No auto-design. Nothing is sized.

Verification examples #

Verification status: 16 values compared in 9 examples (1 published, 8 hand calculations from the cited equations): 16 within tolerance, 0 recorded deviations. Thin: only 1 published example. Code basis: the provisions it uses were read in the target edition.

Hand calculations check:

• The same crane under ASCE 7-22 class B (10 %), with its longitudinal forces.
• Monorail and hand-geared cranes.
• Machinery at 20 %, at 50 % and with a manufacturer's 60 %.
• A hoist governed by its stall load.
• An elevator reaction with 100 % impact.