Typical control gaps should initially be about 20mm wide, clear of mortar dags or bridges, tied at appropriate intervals with flexible ties and sealed with a polyethylene rod or suitable compressible filler. The filler material should be positioned well back from the masonry surface to avoid the filler material becoming visible if the joint contracts. Common Problems The typical problems arising with expansion gaps include: Inadequate sealing Failure to ensure that the gaps are clean and that no hard materials such as mortar droppings are left before sealing The use of joint fillers that are too rigid, which have compressive strengths high enough to transfer forces across the joint. However, these problems can be avoided by good workmanship during construction. Further information on expansion gaps is available in our Design Considerations section. Brick Properties Brick Technical Manual 10 1.6 Efflorescence Efflorescence is defined by salts left on the surface of Chlorides are almost non-existent, but in some units after evaporation of water. The surface deposits instances carbonates of calcium, sodium and can be either loose crystalline salts or amorphous films potassium may appear. which can be a result of small amounts of soluble salts.

it is important in ordering hinges to specify the type of hinge needed to satisfy mounting conditions. If hinge leaves are to be mortised into both the edge of the door and the jamb, a full-mortise hinge is required (Fig. 11.76a, c, and h). If leaves are to be surface-applied to both the side of the door and the face of the jamb, a full-surface hinge is needed (Fig. 11.76d). If one leaf is to be surface-applied and the other mortised, the hinge is a half-surface hinge or a half-mortise hinge, depending on how the leaf for the door is to be appliedhalf-surface if applied to door surface (Fig. 11.76b, e, and ) and half-mortise if mortised in the door end (Fig. 11.76g). Exterior doors should have butts of nonferrous metal. Although chromium plating does not tarnish, it is not considered to be satisfactory on steel for exterior use. Interior doors in rooms where dampness and steam may occur should be of nonferrous metal and should also have butts of nonferrous metal. Butts for other interior work may be of ferrous metal. Ferrous-metal butts should be of hardened cold-rolled steel. Where doors and door frames are to be painted at the job site, butts should be supplied with a primecoat finish. For doors and trim that are to be stained and varnished, butts are usually

16.9.9 Elevator Group Supervision The supervisory control system for group automatic operation of elevators should be capable of making adjustments for varying traffic conditions. It should control car motion so that cars in the best location for answering calls do so. In the past, group control systems employed an elaborate relay network to program elevator motion. The advent of microprocessors, however, has dramatically changed elevator control systems. The state-of-the-art group control system employs limited artificial intelligence features, which control the dispatching of high-speed elevator groups more efficiently. One such supervisory control system contains a database based on practical knowledge, traffic data, and experience of elevator group-control experts. The system is able to maximize every elevator operation by application of the database and through knowledge it has obtained from ongoing traffic monitoring functions, such as call quantity and car loading. Decisions also involve use of fuzzy logic, which allows the elevator group control to make decisions based on fragmentary and fuzzy intelligence concepts. For example, use of the incorporated intelligence and common sense in the decision-making process maximizes the effectiveness of the system and assists in determining whether or not potential car assignments will result in shorter waiting times or cause congestion in elevator lobbies. In another approach, the system is designed to alleviate lobby congestion during heavy up-peak traffic periods. Elevators make fewer stops per round trip, with the result that cars return to the lobby faster. The floors about the lobby served by the group are divided into sectors of contiguous floors. The number of sectors is normally one less than the number of elevators in the group. As an elevator returns to the lobby during an up-peak period, it is assigned to service one of the sectors. Passengers can easily determine which floors each car is serving by checking the Information Display System screens located next to or above each elevator entrance. The same car will not necessarily serve the same sector on successive trips. Care is taken to ensure that each sector will receive equal service by the assignment of sectors in a round-robin manner. In still another approach, unlike any other control system presently in use, the system is arranged to know the passenger quantity and destination before the call is answered by the elevator. This is achieved through the use of a keypad call-entry system installed at each landing. The prospective passenger enters the destination into the keypad, and the elevator control system immediately assigns an elevator to that call. The passenger is notified graphically which elevator will respond to the call. Since the efficiency of elevator movement is greatly improved, this system offers the opportunity to reduce the quantity of elevators used to meet specific traffic