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Please feel free to call to discuss a project or to find out more about RCB Elevator Consulting, LLC

phone:
415.350-0402

email:
rich AT blaska DOT com


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Elevator Structural Engineering

There are numerous instances in the elevator industry when structural engineering may be called for.  RCB Elevator Consulting, LLC (RCB), in concert with Eddington Engineering, provide elevator structural engineering services nationwide. 

Listed below are a number of ASME A17.1, 8.7 Alterations code sections where structural engineering may be beneficial or required:

  8.7.1.5  Design.  Design shall be verified by a licensed professional engineer for welding, repair, cutting, or splicing of members upon which the support of the car, counterweight, escalator, or moving walks, trusses, girders, and tracks depends.

This alteration code section is fairly broad in scope.  Any modifications to an elevator's machine beams or an escalators truss would trigger this section. 

  8.7.2.9  Machinery and Sheave Beams, Supports, and Foundations.  Where new machinery and sheave beams, supports, foundations, or supporting floors are installed, relocated, or where alterations increase the original building design reactions by more than 5%, they shall conform to 2.9, and the adequacy of the affected building structure to support the loads shall be verified by a licensed professional engineer.  (also see 8.7.3.9)

Note this section can be triggered in two different ways:  A change to the structure or an increase in loading.  Also note that engineering is required not just for the elevator equipment but also for the "affected building structure..."  We have found cases where the existing building structure supporting the machine beams was deficient.  Some authorities having jurisdiction (AHJ) cite this section whenever a traction drive machine is replaced and especially so when a winding drum is converted to a traction elevator. 

  8.7.2.15.1  Alterations to Car Frames and Platforms.  (also see 8.7.3.14)  This section doesn't specifically require professional engineering but, depending on the alteration, proper engineering may be imperative.  We have seen cases where the client added extensions to existing car stiles, to obtain a taller car, that didn't structurally work. 

  8.7.2.15.2  Increase or Decrease in Deadweight of Car.  (references 8.7.2.9)  This is the other "5% Rule."  This section does require professional engineering to re-certify the elevator and the specific components affected.  Often the building owner would like to replace the car interior finishes but the new design is limited by the 5% rule.  By performing the engineering, and any elevator upgrades the engineering requires, the deadweight of the car can be increased beyond 5% the meet the owner's needs.

  8.7.2.16.1  Change in Type of Service.  (also see 8.7.3.17)  The most common application of this section is the conversation of a Freight elevator to a Passenger elevator.  Though technically professional engineering isn't required by this section, what is retained of the original elevator should be properly certified for the new loads applied.  Also, often the original freight platform is replaced with a smaller passenger platform.  This requires new passenger entrances to be set some distance inside the hoistway to the proper clearance with the new platform.  New landing extensions are required between the original entrances and the new entrances, which must be properly engineered.

  8.7.2.16.4  Increase in Rated Load.  (references 8.7.2.9)This section, similar to 8.7.2.15.2, does require professional engineering to re-certify the elevator and the specific components affected.  Something often misunderstood, the code prescribes the minimum load rating based on the inside car area.  Cars of the same area can have a greater load rating if desired - you can over-rate but you can't under-rate an elevator's rated load (capacity).  We've encountered situations when the owner wanted an elevator with a higher load rating than the minimum the code required.

  8.7.2.17.1  Increase or Decrease in Travel.  On a traction elevator in particular, changing the travel often means relocating the drive machine in an overhead arrangement or the overhead sheaves in a basement arrangement.  This would likely trigger sections 8.7.1.5 and 8.7.2.9, which require professional engineering.

  8.7.2.17.2  Increase in Rated Speed.  In most cases increasing the rated speed of a traction elevator requires replacing the drive machine.  If the new machine is heavier, the machine beams must be re-certified.  The new machine will likely require a change in its connection to the machine beams, new blocking beams, anchorage, etc., which should be engineered.  If sections 8.7.1.5 and 8.7.2.9 are triggered, professional engineering would be required.

  8.7.2.20  Ascending Car Overspeed and Unintended Car Movement Protection.  (references 2.19)  In an alteration, this section typically means installing either a Hollister-Whitney Rope Gripper or a BODE Rope Brake.  California DOSH-ERT has indicated that professional engineering is not required in all cases, however, they may require it if the installation appears not to be structurally sound.  We've designed dozens of rope brake installations and many require creative solutions (see Rope Grippers & Brakes).

  8.7.2.21.1  Change in Rope.  This section relates to changing the "material, grade, number, or diameter of ropes" while retaining the original sheaves.  It calls for certification of the rope change by either "the original elevator manufacturer or a licensed professional engineer..."  We've never encountered such a situation and would generally recommend replacing the sheaves.  We have engineered drive machine replacements and retained the deflector sheaves, but only when the same quantity, grade and diameter ropes are used.  A change from standard to high strength ropes should be certified by the machine manufacturer.

  8.7.2.24  Guide Rails, Supports, and Fastenings.  (also see 8.7.3.28)  The code doesn't specifically call for professional engineering when altering the guide rails and supports.  However, engineering should be performed to correctly determine the maximum bracket spans, the bracket design, fastenings, etc.  This is especially important in seismic zones where compliance with section 8.4 is required.  If the alteration involves an elevator installed prior to the adoption of the seismic codes, very often the existing guide rails and brackets - especially for the counterweight - do not comply with the current standards.

  8.7.2.25.1  Alteration to Driving Machines and Sheaves.  This section includes the replacement of traction drive machines.  As stated above, the section does not necessarily require professional engineering but there are many reasons that the installation should be properly engineered.  However, if sections 8.7.1.5 and 8.7.2.9 are triggered, professional engineering is required.

  8.7.2.25.2  Change in Location of Driving Machine.  Changing the drive machine location necessarily means changing the machine's building support, whether it includes new machine beams or structural slab in an overhead installation or a new anchorage means in a basement or offset installation.  This would trigger sections 8.7.1.5 and 8.7.2.9, which require professional engineering.

The proper approach is to prepare the engineering prior to performing the work.  If the code or AHJ require it, the engineering should be submitted for approval prior to performing the work.  When performing an inspection, an AHJ inspector may request professional (structural) engineering if something does not appear to them to be structurally sound.  We have seen this occur for items as varied as the mounting of a new AC motor on a geared machine to car frame stile extensions to access work platforms. 

Some alterations, in our belief, should not be attempted without full engineering, including structural engineering.  These include winding drum elevator conversions to traction (see Winding Drum Elevators), freight to passenger elevator conversions, seismic upgrade and certification, major car frame modifications, some drive machine replacements where the supports are to be modified, etc.

Sometimes structural engineering can be as simple as a preparing a sketch of the equipment and a few sheets of structural calculations.  On a large alteration, such the examples above, the project should include detailed shop drawings as well as the structural engineering (see Projects).  These shop drawings can serve many purposes including approval submittals for the client and the AHJ, planning, coordination, fabrication, installation, inspection and record sets. 

Our elevator structural engineering service is especially suited to the alteration (modernization) market in that we perform our own field surveys as required for most existing conditions.  Most often when modifying existing equipment there is no original engineering to draw from.  When shop drawings of the old equipment do exist, seldom are they sufficiently detailed to show the information needed.  Having the client sketch the condition can often leave out important information.  So, especially on the more complex issues, performing our own field survey assures the most accurate and efficient outcome.

If you are an elevator contractor with a project in need of professional structural engineering, please give us a call.

 

 

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