SITE OBSERVATION - ROLE OF ARCHITECT OR ENGINEER DURING CONSTRUCTION BASICS AND TUTORIALS

SITE OBSERVATION - ROLE OF ARCHITECT OR ENGINEER DURING CONSTRUCTION BASIC
Site Observation Role Of Architect Or Civil Engineer During Civil Projects


Site Observation
As part of their ongoing services during construction, and depending on the scale and complexity of the project, architects and engineers may make periodic site visits or maintain full-time representation on site during a portion or all of the construction period.

The professional’s role is to expedite day-to-day communication and decision making by having on-site personnel available to respond to required drawing and specification clarifications.

Site-observation requirements for the project should be discussed with the client at the onset of the project and be outlined in the architect-client agreement. Many clients prefer periodic or regularly scheduled site visits by the design professional.

A provision for additional or full-time on-site representation, however, can be addressed in the agreement, and compensation for this additional service can be outlined in the agreement for discussion with the client later in the development process or during the construction phase.

The client and the architect and engineer should agree on the appropriate amount of site visitation provided in the architect’s basic services to allow adequate site-observation services based on specific project conditions.

If periodic site observations are made, the architect should report such observations to the client in written form. This should call attention to items observed that do not meet the intent of the construction documents.

It is normally left to the client to reject or replace work unless such defective work involves life safety, health, or welfare of the building occupants or is a defect involving structural integrity.

If the architect provides full-time site observation services, daily or weekly reports should be issued to the client outlining items observed that are not in accordance with the construction documents or design intent.

STEEL MAKING METHODS BASICS AND TUTORIALS

STEEL MAKING METHODS BASIC INFORMATION
What Are The Basic Steel Making Techniques And Methods?


Structural steel is usually produced today by one of two production processes. In the traditional process, iron or ‘‘hot metal’’ is produced in a blast furnace and then further processed in a basic oxygen furnace to make the steel for the desired products.

Alternatively, steel can be made in an electric arc furnace that is charged mainly with steel scrap instead of hot metal. In either case, the steel must be produced so that undesirable elements are reduced to levels allowed by pertinent specifications to minimize adverse effects on properties.

In a blast furnace, iron ore, coke, and flux (limestone and dolomite) are charged into the top of a large refractory-lined furnace. Heated air is blown in at the bottom and passed up through the bed of raw materials.

A supplemental fuel such as gas, oil, or powdered coal is also usually charged. The iron is reduced to metallic iron and melted; then it is drawn off periodically through tap holes into transfer ladles.

At this point, the molten iron includes several other elements (manganese, sulfur, phosphorus, and silicon) in amounts greater than permitted for steel, and thus further processing is required.

In a basic oxygen furnace, the charge consists of hot metal from the blast furnace and steel scrap. Oxygen, introduced by a jet blown into the molten metal, reacts with the impurities present to facilitate the removal or reduction in level of unwanted elements, which are trapped in the slag or in the gases produced.

Also, various fluxes are added to reduce the sulfur and phosphorus contents to desired levels. In this batch process, large heats of steel may be produced in less than an hour.

An electric-arc furnace does not require a hot metal charge but relies mainly on steel scrap. The metal is heated by an electric arc between large carbon electrodes that project through the furnace roof into the charge.

Oxygen is injected to speed the process. This is a versatile batch process that can be adapted to producing small heats where various steel grades are required, but it also can be used to produce large heats.

Ladle treatment is an integral part of most steelmaking processes. The ladle receives the product of the steel making furnace so that it can be moved and poured into either ingot molds or a continuous casting machine.

While in the ladle, the chemical composition of the steel is checked, and alloying elements are added as required. Also, deoxidizers are added to remove dissolved oxygen. Processing can be done at this stage to reduce further sulfur content, remove undesirable nonmetallics, and change the shape of remaining inclusions.

Thus significant improvements can be made in the toughness, transverse properties, and through-thickness ductility of the finished product. Vacuum degassing, argon bubbling, induction stirring, and the injection of rare earth metals are some of the many procedures that may be employed.

Killed steels usually are deoxidized by additions to both furnace and ladle. Generally, silicon compounds are added to the furnace to lower the oxygen content of the liquid metal and stop oxidation of carbon (block the heat).

This also permits addition of alloying elements that are susceptible to oxidation. Silicon or other deoxidizers, such as aluminum, vanadium, and titanium, may be added to the ladle to complete deoxidation.

Aluminum, vanadium, and titanium have the additional beneficial effect of inhibiting grain growth when the steel is normalized. (In the hot-rolled conditions, such steels have about the same ferrite grain size as semikilled steels.)

Killed steels deoxidized with aluminum and silicon (made to finegrain practice) often are used for structural applications because of better notch toughness and lower transition temperatures than semikilled steels of the same composition.

(W. T. Lankford, Jr., ed., The Making, Shaping and Treating of Steel, Association of Iron and Steel Engineers, Pittsburgh, Pa.)