CHICAGO BOOM DERRICK BASICS AND TUTORIALS

CHICAGO BOOM DERRICK BASIC INFORMATION
What Is A Chicago Boom Derrick?

Chicago Boom Derrick

A Chicago boom can be mounted on a building frame during or after construction, on a tower, or on any frame. Indeed, Figure 1.19 shows one installed on a power plant stack.

When a boom or strut is assembled in the form of a Chicago boom, it can range from as little as 10 ft (3 m) to as much as 125 ft (38 m) in length, and capacities can range from a low of, say, ¼ ton (225 kg) to a practical upper limit of perhaps 35 tons (32 t).

In the not too distant past, booms were made of wooden poles. Short lightweight booms are easily and inexpensively made of single steel pipes fitted with the necessary attachments, but most booms are trussed, or latticed, structures of angle irons or tubing or a combination of the two. Aluminum and synthetic composite booms are plausible, too, where site conditions favors such unconventional materials.

The topping lift usually employs ordinary hoisting blocks; one is fitted at the boom tip held off with steel straps while the opposite end is mounted at the pivot fitting on the support structure also with straps.

The upper load block may consist of sheaves built into the boom head, or it may be a common block suspended on straps.  The purpose of straps is to allow clearance between the rope suspension system and adjoining boom elements through the full range of luffing motion.

A Chicago boom is able to hoist materials to a height above the boom foot, with the horizontal reach limited by the length of the boom and the swing arc by the host structure. Swing guys often are fitted to the boom tip and are run laterally on each side to a point of anchorage.

Wind, friction at the pivots, and the resistance of the opposing guy must be overcome when pulling on the line to swing. With a manual arrangement, the guys are fiber ropes arranged with several parts of line. Hand pulling through several parts can take several minutes to swing the boom through 90°. Where production economics justifies the expense to attain greater speed, mechanical swing systems are used.

In the typical installation, a two-drum winch is used to power the hoisting and topping motions, but when the work involves only lifting and swinging, the topping motion will not be needed. A fixedrope guy line can then be installed, or to make adjustment easier and to provide flexibility.

Visual control can be established when the winch is located at the floor level of the boom foot, particularly when the loads are to be hoisted to this floor, but the winch can be located at any level. When the winch is too large or too heavy to be lifted in the job-site material hoist or in the elevator of an existing building, it may be necessary to use a small temporary winch to operate the derrick in order to hoist the working winch.

Alternatively the winch can be positioned on the ground. When the winch is on the ground, the operator has direct communication with the ground crew and can have the boom and load in view at all times.

When the winch is on the same floor as the boom foot and the loads are to be hoisted to that floor, the operator has direct communication with the swing and load-landing crew and has the boom but not the load in view at all times.

FOUNDATION ENGINEERING BASICS AND TUTORIALS

FOUNDATION ENGINEERING BASIC INFORMATION
What Is Foundation Engineering?

The title foundation engineer is given to that person who by reason of training and experience is sufficiently versed in scientific principles and engineering judgment (often termed "art") to design a foundation. We might say engineering judgment is the creative part of this design process.

The necessary scientific principles are acquired through formal educational courses in geotechnical (soil mechanics, geology, foundation engineering) and structural (analysis, design in reinforced concrete and steel, etc.) engineering and continued self-study via short courses, professional conferences, journal reading, and the like.

Because of the heterogeneous nature of soil and rock masses, two foundations—even on adjacent construction sites—will seldom be the same except by coincidence. Since every foundation represents at least partly a venture into the unknown, it is of great value to have access to others' solutions obtained from conference presentations, journal papers, and textbook condensations of appropriate literature.

The amalgamation of experience, study of what others have done in somewhat similar situations, and the site-specific geotechnical information to produce an economical, practical, and safe substructure design is application of engineering judgment.

The following steps are the minimum required for designing a foundation:

1. Locate the site and the position of load. A rough estimate of the foundation load(s) is usually provided by the client or made in-house. Depending on the site or load system complexity, a literature survey may be started to see how others have approached similar problems.

2. Physically inspect the site for any geological or other evidence that may indicate a potential design problem that will have to be taken into account when making the design or giving a design recommendation. Supplement this inspection with any previously obtained soil data.

3. Establish the field exploration program and, on the basis of discovery (or what is found in the initial phase), set up the necessary supplemental field testing and any laboratory test program.

4. Determine the necessary soil design parameters based on integration of test data, scientific principles, and engineering judgment. Simple or complex computer analyses may be involved.

For complex problems, compare the recommended data with published literature or engage another geotechnical consultant to give an outside perspective to the results.

5. Design the foundation using the soil parameters from step 4. The foundation should be economical and be able to be built by the available construction personnel.

Take into account practical construction tolerances and local construction practices. Interact closely with all concerned (client, engineers, architect, contractor) so that the substructure system is not excessively overdesigned and risk is kept within acceptable levels. A computer may be used extensively (or not at all) in this step.