Concrete structures are vital in construction, and ensuring their durability involves careful consideration of potential congestion issues in reinforced concrete members. Designers play a crucial role in preventing congestion, and adherence to building codes is essential. Here are practical tips to avoid reinforcement and embedment congestion in concrete members:
Adequate Space Planning : Ensure sufficient space between steel bars to facilitate concrete pouring, aligning with building code requirements.
Optimal Member Size : Increase the size of concrete members when feasible to create ample space for efficient concrete placement.
Strategic Access Points : In heavily reinforced concrete, create access points through placed steel bars to allow smooth concrete pouring.
Maintain Concrete Cover : Uphold an adequate concrete cover to enable aggregate passage between formwork and steel bars.
Accurate Scale Consideration : Recognize that a nominal 25 mm bar on a drawing may measure nearly 30 mm in diameter in practice due to deformations and tying wires.
Vertical Alignment Caution : Be aware that vertically aligned bars may deflect downward, potentially reducing the designed distance between rows of steel bars.
Joint Dimension Verification : In beam-beam and beam-column joints expecting steel congestion, draw the joint to scale and verify the passage of poker vibrators through reinforcements.
Mechanical Splicing : Utilize mechanical splicing to prevent steel congestions when bar splicing is anticipated.
Welded Connections : Employ welded connections for steel bar splicing to reduce steel congestion.
Consider Splicing Impacts : Be mindful that both mechanical and welded splicing methods lead to a localized increase in bar diameter, requiring careful detailing clearances.
Formwork design plays a crucial role in preventing congestion. Consider the following tips:
Proper Formwork Design : Formwork designer should consider form height, location of boxouts and embedment, concrete hose location, and number, location, and size of tie rods.
External Tie Rods : Use external tie rods for narrow walls to alleviate congestion issues.
Optimal Spacing : Increase spacing in load-bearing members and employ higher capacity ties and sheathing for effective congestion management.
Consider concrete mix proportion, nominal maximum aggregate size, and detailing of reinforcement steel bars when arranging embedment and boxouts:
Void Forms for Prevention : Use void forms to prevent form penetration. Install concrete placement and vibration pipes for forms measuring 0.6 m or more in each direction.
Placement and Vibration Tubes : Install concrete placement and vibration tubes through boxouts greater than 0.6 m x 0.6 m and those intended for removal later.
Adaptable Boxout Tolerances : For stay-in-place boxouts like metal window frames, use tolerances that permit shifting. Create access holes at the bottom spanning from one form face to another.
By implementing these straightforward yet effective strategies, designers can contribute to the longevity and structural integrity of concrete members while avoiding congestion-related challenges.
