It is a horizontally reinforced element in a masonry wall that provides resistance to help distribute lateral loads throughout the wall section and also shear loads. Reinforcement is placed in special bond-beam units that have grouted solid and reduced-height cross webs. Bond beams are usually seen at the tops of walls, top of foundation walls, and at each floor diaphragm connection. bond beams Intermediate are often required in higher seismic design categories.
Bond beams are sometimes arbitrarily placed in walls as a tie element or stiffening, floor connections, recommended at tops of walls, and top of foundation walls. Intermediate bond beams are normally not necessary unless to fulfill minimum seismic reinforcement requirements or required to resist shear stresses.
The middle of a bond beam with vertically reinforced cells can be very congested, with multiple bars in each direction. Minimize the amount of bond beam steel to improve permit proper grout consolidation and grout flow.
lapped with the bond beam steel, Use L-shaped corner bars, to provide continuity around building corners.
EXPANSION AND CONTROL JOINTS
It is best to cut bond beam reinforcement at control joints and expansion joints. The exception to this rule is at floor diaphragms, where the bond beam may be acting must be continuous down the wall and diaphragm chord. lateral continuity across movement joints is not required for structural performance. but normally It is possible to detail a slip connection around bond beam reinforcement.
purpose of bond beams in concrete masonry walls
Concrete masonry units are used to integrate the horizontal reinforcement with vertical reinforcement bars in a reinforced masonry wall. It is often placed at regular intervals in the wall to permit placement of more reinforcement than would be possible using bed joint reinforcement. Bond beams can be used in masonry bearing walls– tying the walls together, to serve as horizontal members along the top of the walls.
Bond beams can be used below a line of bar joists, so that joist anchors can be embedded into the grout of the bond beam. Bond beams often are used as lintels over windows and doors. It can also be used for crack control. In this application, there must be the control joints in a wall break between bond beams. Moisture from the grout causes the CMU to expand during construction. The Concrete masonry units will shrink as this moisture dissipates over time.
Dimension and Shape of Bond Beam Block
Bond beam block face dimensions of 20.3 cm by 40.6 cm, available in nominal thicknesses of 10.2, 15.2, 20.3, 25.4, 30.5, 35.6, and 40.6 cm. Specified dimensions of CMU are 0.95 cm less than nominal dimensions so that 10.2 or 20.3 cm module is maintained with 0.95 cm mortar joints. ASTM C90 provides minimum face shell and web thicknesses for the different sizes of CMU as in Table.
Nominal Width of Blocks, cm
Face Shell Thickness, minimum in cm
Web Thickness, minimum, cm
Equivalent Web Thickness, minimum, cm/linear m
7.62 and 10.2
30.5 and greater
Bond beam block height, length, and width are allowed to vary by 0.32 cm from the specified dimensions.
Web thickness and Face shell need to be in agreement with the values provided in Table.
Bond beam blocks free of cracks and shall be sound or other defects that interfere with the proper placement of the unit or significantly impair the permanence or strength of the construction.
incidental to the usual method of minor chipping or manufacture resulting from customary methods of handling in delivery or shipment, Minor cracks are not grounds for rejection. ApplicationsThis block is used in the construction of bond beams in the masonry wall of a structure. They are courses of a block constructed with specially manufactured masonry units which are designed to receive grout or horizontal reinforcement. The beam bond can be used in masonry bearing walls. tying the walls together. Beam bonds can be used below a line of bar joists.