PARTS AND COMPONENTS OF ESCALATOR BASICS AND TUTORIALS

Escalators, or powered stairs, are used when it is necessary to move large numbers of people from floor to floor. They provide continuous movement of persons and can thus remedy traffic conditions that are not readily addressed by elevators.

Escalators should be viewed as preferred transportation systems whenever heavy traffic volumes are expected between relatively few floors. Escalators are used to connect airport terminals, parking garages, sports facilities, shopping malls, and numerous mixed-use facilities.

Although escalators generally are used in straight sections, spiral escalators also are available. Although expensive due to manufacturing complexities, they offer distinct advantages to both the designer and user because of their unique semicircular plan form.


An escalator resembles a powered ramp in construction. The major difference is that a powered ramp has a continuous treadway for carrying passengers, whereas the treadway of an escalator consists of a series of moving steps.

As for a powered ramp, the installation of powered stairs should conform with the requirements of the ‘‘American National Standard Safety Code for Elevators, Dumbwaiters, Escalators and Moving Walks,’’ ANSI A17.1.

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An escalator consists of articulated, grooved treads and risers attached to a continuous chain moved by a driving machine and supported by a steel truss framework.

The installation also includes a handrail on each side of the steps that moves at the same speed as the steps; balustrades, or guards, that enclose the steps on each side and support the handrails; brakes; control devices; and threshold plates at the entrance to and the exit from the treadway.

The purpose of the threshold plates is to facilitate smooth passage of passengers between the treadway and landing.

The plates are equipped with a comb, or teeth, that mesh with and are set into grooves in the treadway in the direction of travel, so as to provide firm footing and to minimize the chance that items become trapped between treadway and the landing.

Each step is formed by a grooved tread portion connected to a curved and grooved riser. The tread and riser assembly is either a single die-cast piece or is assembled to a frame.

Both are suspended on resilient rollers whose axles are connected to the step chain that moves the steps. The step rollers ride on a set of tracks attached to the trussed framework. The tracks are shaped to allow the step tread to remain horizontal throughout its exposed travel.

REVIEWING ESTIMATES OF CIVIL ENGINEERING PROJECTS

All estimates should be reviewed by all responsible parties at every stage. An estimate review should begin with a survey of the verbal description of the work, including all or most of the following: scope statement, assumptions, clarifications, qualifications, and exclusions.

As an example, the estimate is to be reviewed for a warehouse to be built in an urban area as part of a redevelopment project. The scope statement should specify the location, refer to design drawings and specifications, and list applicable building codes.

The assumptions might include such data as the number of persons who will work in the warehouse. This is an indication of the number of restrooms and fixtures needed, which can be listed as a clarification. If the price quotes are valid for 90 days, this should be stated as a qualification.

Handling and disposing of any existing hazardous material found on the site might be listed as an exclusion. This warehouse description may be reasonably complete from the viewpoint of designer and contractor and may be accurately priced.

But because of the assumption regarding the number of occupants, it may not be suitable from the viewpoint of the intended users. The exclusion regarding hazardous materials may result in unacceptable financial exposure for the client.

Issues such as these need to be addressed. The client may decide that the prospective tenants, or users, may employ more persons than the number assumed. Hence, either the estimate will have to allocate more money for rest rooms or the client will have to give the tenants an allowance to enable them to build the rest rooms they desire.

The client may also decide that an analysis of soil samples may be necessary before any construction is done to determine the extent of contamination, if any, and cost of cleanup.

Bearing these issues in mind, the parties should now review the quantitative part of the estimate. This review should comprise the following:

A summary of the key quantities involved; for example, floor area, tons of steel, cubic yards of concrete.

As a cross check, a list the key quantities—by discipline if the estimate has been prepared with the industry approach or by industry if the estimate has been prepared by the discipline approach.

A summary of the project, by industry or discipline.

At each step of the review, changes may be made, as required. After all parties agree to all parts of the estimate, it can be considered final.

At this stage, the designer should be satisfied that enough money has been allocated to carry out the project. The client should have a clear idea as to what the project will entail and how much it will cost.