BONDEK II COMPOSITE SLABSGeneral
BONDEK II profiled steel sheet is capable of withstanding temporary construction loads including the mass of workmen, equipment and materials all in accordance with AS 3610 (refer to Lysaght publication BDII-1). However, it is good construction practice to ensure protection form concentrated loads, such as barrows, by use of some means such as planks and/or boards.
BONDEK II sheeting acts as longitudinal tensile reinforcement and should be treated as such. The condition of the sheeting should be inspected before the concrete is poured.
Reinforcement in slabs is required to carry and distribute the design loads and to control cracking. Reinforcement is generally detailed as transverse and longitudinal in relation to span, but other reinforcement required for trimming may be positioned in other orientations. Refer to Figure 20 for a typical cross-section of a BONDEK II composite slab and terms associated with the placement of reinforcement.
Reinforcement must be properly positioned, lapped where necessary to ensure continuity, and tied to prevent displacement during construction. Fixing of reinforcement is to be in accordance with Clause 19.2.5 "Fixing" of AS 3600.
The uppermost layer of reinforcement must be positioned and tied to prevent displacement during construction to obtain the specified minimum concrete cover (refer to Lysaght publication BDII-2 for guide to the recommended concrete cover).
Splicing shall comply with Clause 13.2 "Splicing of Reinforcement" of AS 3600. For movement joints, the reinforcement is stopped short on either side of the joint to permit movement of the adjoining slabs.
Where fabric is to be used in thin slabs or where fabric is used to act as both longitudinal and transverse reinforcement, particular attention should be taken to ensure the specified minimum concrete cover and the required design reinforcement depth are maintained at the splices. To assist in this matter, it is prudent to use splice bars.
Fixing of reinforcement using chairs and spacers must be such that the chairs and spacers are placed upon the pan area. Depending upon the chair type used and the load they carry, it may be necessary to use plates underneath the chairs to alleviate depressions in the BONDEK II sheeting, particularly where the soffit will be exposed. Transverse reinforcement may be utilised as spacers or supports for longitudinal reinforcement.
Transverse reinforcement is positioned across the ribs of the BONDEK II profiled steel sheeting. Transverse reinforcement may be detailed as deformed bar or fabric reinforcement. In most applications the transverse reinforcement is for the crack control due to shrinkage and temperature effects. Transverse reinforcement for large holes is used to distribute loads into adjacent strips of composite slabs.
To control flexural cracking in the top face of the slab, transverse reinforcement in the top-face may be detailed over walls or beams, which run in the same direction as the BONDEK II sheets.
For ease of construction, reinforcement for control of cracking due to shrinkage and temperature effects is generally fabric reinforcement. Refer to Lysaght publication BDII-2 Part A for a guide to fabric selection.
Unless otherwise specified, the bottom-face transverse reinforcement for control of cracking due to shrinkage and temperature effects should be placed directly on top of the ribs of BONDEK II profiled steel sheeting for unexposed slabs not exceeding 250mm in depth, otherwise direction from the design engineer will be required.
Longitudinal reinforcement is positioned in the same direction as the ribs of the BONDEK II profiled steel sheeting. Longitudinal reinforcement may be detailed as deformed bars or fabric reinforcement.
Longitudinal reinforcement is positioned to carry design loads and is located in the top and bottom faces of the slab.
Top-face longitudinal reinforcement is located over interior supports of the slab and extends into approximately a third of the adjoining spans, or as detailed by the structural engineer. For design information refer to Lysaght publication BDII-2 Part A. For single spans, top-face longitudinal reinforcement is not normally detailed.
Bottom-face longitudinal reinforcement is located between supports of the slab but depending upon the detailing over the interior supports, it may be continuous, lapped or discontinuous. Bottom-face longitudinal reinforcement may be placed on top or below transverse reinforcement.
Location of bottom-face longitudinal reinforcement in elevated temperature conditions requires special detailing. Generally, this will require the bottom-face longitudinal reinforcement to be kept a minimum distance away from the ribs and soffit of the BONDEK II sheeting. Refer to Lysaght publication BDII-2 Part B for design information.
Trimmers are used to distribute the design loads to the structural portion of the slab and/or to control cracking of the concrete at penetrations, fittings and re-entrant corners.
Trimmers may be either deformed bars or fabric reinforcement and in straight lengths or shaped. The trimmers may be detailed or specified to be laid at angles. The trimmer reinforcement is generally detailed between the top and bottom layers of transverse and longitudinal reinforcement.
Fixing of trimmers is generally with ties from the top and bottom layers of reinforcement.