Emirate Towers
Dubai (United Arab Emirates)

Routine for the BBR Network of Experts

Designers, builders, owners and users of buildings require more efficiencies today than ever before. The BBR slab post-tensioning systems offer all the stakeholders in a building project many benifits, including:

• Reduced structure depth
• Greater clear spans
• Design flexibility
• Formwork versatility
• Reduced construction costs
• Enhanced construction speed
• Improved durability
• Minimum maintenance costs

Two unique types of BBR post-tensioning systems are typically used for slab post-tensioning. The unbonded CONA CMM post-tensioning system, consist of 1, 2 or 4 seven-wire prestressing mono strands, where each strand is factory provided with a flexible corrosion inhibitor and an individual HDPE sheathing, and the bonded CONA CMF
post-tensioning system with 1 to 6 strands inside a post-grouted flat
steel or flat plastic duct. For transfer beams or areas with high loads
the CONA CMI multi-strand system is often times used as a
complimentary system.

After the concrete has reached a suitable strength, the individual strands have specified loads applied by means of a hydraulic jack and are locked in the propriety CONA CMM or CONA CMF anchorages. Stressing might be applied in stages to control creep and shrinkage of the concrete. After the stressing has been completed the excess tendon strands are cut and for the CONA CMF systems, the duct is filled with a high performance grout mixture to provide bond and corrosion protection. Differently to the CONA CMF system, the CONA CMM system remains unbonded and does not required grouting because the tendons are individually factory provided with a multi layer corrosion protection system.

Applications for the BBR Slab Post Tensioning System include:

• Residential and commercial buildings
• Industrial floor slabs on the ground
• Transfer floor structures
• Parking structures
• Water tank bases and walls
• Transverse stressing of bridge decks

Shopping Centre
Salzburg (Austria)

Post tensioning of suspended slabs provides many benefits to a wide range of structures. These benefits include:

• Faster construction
• Water resistant properties
• Early formwork stripping
• Floor to floor height reduction
• Reduced foundation load
• Improved deflection control
• Greater column free areas
• Architectural freedom

Many types of suspended slab structures typically realize the benefits of post tensioning, such as:

• Parking Structures
• Apartment buildings
• Commercial office space
• Retail centers
• Hospitals
• Storage facilities
• Stadiums
• Exhibitions centers
• Schools
• Institutional facilities

Design of Suspended Slabs

The design of post-tensioned suspended slabs requires sound engineering consideration in order to maximize the benefits for all the stakeholders in a project. The BBR Network can offer design input from initial advice to fully detailed design for construction drawings.

Structural detailing is an art that engineers develop with experience and sound understanding of post-tensioned structures, but it is the essential part of a cost effective and reliable structure.

Multifunctional Residental Building
(Slovenia)

Construction of Suspended Slabs

The BBR Network has worked closely over many years with builders and construction personnel resulting in a well understood system that enhances the construction process. An appreciation of the construction process will enable all parties involved in the on-site works to benefit from the system. The typical construction sequence is as follows:

1. Erect formwork
2. Install bottom reinforcement
3. Install post-tensioning
4. Install top reinforcement
5. Pour concrete
6. Strip edge forms
7. Initial/partial stressing of tendons
8. Final stress/cut off excess tendon strand
9. Strip formwork
10. Grout tendon (if required)

Slabs on Ground
The post tensioning of slabs on ground is providing many developers and builders with a cost effective pavement solution. Benefits realized with post tensioned slabs on ground include: Large joint free slab area (no saw cuts) Reduced construction costs Less sub base preparation and/or excavation Enhanced performance on weak ground Faster construction time Reduced on going maintenance costs Water resistant properties Potential for increased loading for future use Facilities that have adopted a post tensioned slab on ground system include: Distribution warehouses Freezer stores Large retail stores Container terminal facilities Heavy duty apron slabs Industrial manufacturing and storage buildings Aircraft hangers Water retaining structures Sporting venues Raft slabs Design of Slabs on Ground The design of post tensioned slabs on ground involves the careful analysis of the loads applied to the slab, the interaction between the slab and the ground that supports it, restraint forces and temperature effects. The BBR Network has refined the design process and achieves outstanding results on a routine basis. The techniques can be extended to deal with weak ground where the ground acts as the permanent formwork and the slab bridges between piles and/or ground beams. This avoids expensive ground improvement work. Our design and construction expertise for preliminary design advice through to final design and construction activities is available to assist builders, engineers and developers in achieving optimum solutions for slab on ground applications.   Construction of Slabs on Ground Prepare subgrade to required compaction Place two layers of polythene slip layer Lay out ducts Install strand and end anchorages Place supplementary anchorage reinforcing Install end forms and dowels as required Place and finish concrete Initial / partial stressing of tendons Final tensioning at full design concrete strength Crop tendon and grout	Slabs on Ground   Fruit Juice Warehouse Floor Leczeszyce (Poland) Storehouse Floor Hamilton (New Zealand)
The BBR Network works very closely with architects, designers, builders, concrete supplier and rack/equipment suppliers to ensure that the design and floor configuration meets the specified performance requirements. The interaction and close team work is very important to ensure that a premium floor is delivered. Stringent quality control measures are implemented and detailed pre-pour meetings are undertaken to ensure that all people associated with the floor placement are aware of the process and necessary inputs. The final quality of the floor is often a function of the environment at the time the concrete is placed. In the majority of cases, the building frame, walls and roof are installed prior to the pour so that the floor can be placed, finished and cured in a controlled environment. When planned carefully, this enhances the overall building programme and allows finishing trades to complete work without any disruptions from weather or segmented floor pours. Very large floor plates can be placed in short time frames reducing the overall programme and enabling clients to commence business operations at the earliest possible time.