Peikko Frame: The Best Alternative to Post-Tensioned Structures

Post-tensioned concrete structures offer many benefits in multi-story buildings such as long spans, thin floor depths and of course fire resistance. Although this type of structure can be labor intensive and require specialized labor, it remains an excellent design choice. However, when this workforce is  unavailable in a certain area or if a project is over budget, the Peikko Frame is the best alternative to post-tensioned concrete.

Peikko Frame / Source: Peikko

Peikko Frame Video / Source: Peikko

The Traditional Alternatives:

Reinforced concrete or Cast-in-place Structures

A cast-in-place concrete structure is in some regards similar to a post-tensioned structure, yet in order to achieve the same spans, the reinforced concrete slabs need to be thicker and therefore heavier. Not only does this additional thickness add to the cost of the concrete but it also increases the weight of the entire structure which will lead to bigger and more expensive foundations.

Just like a post-tensioned structure, cast-in-place is inherently non-combustible.

Cast-in-place structure / Source: Peikko

Steel Structures

Since it is to a large extent prefabricated, a steel structures has the ability to be erected quickly with a comparatively small crew of installers. Nevertheless, the thickness of the traditional assembly of the beams supporting the joists and deck will inevitably increase the floor-to-floor height when compared to a post-tensioned structure. With steel structures, to maintain the same number of floors the building height will have to be increased. If the overall height cannot be increased than there is a possible lost of one or more floor levels. 

Conventional steel decking / Source:weldersuniverse.com

Additionally this increased floor-to-floor height will have a direct impact on the cost especially on the more expensive vertical components such as exterior cladding.

Since unprotected steel members do not resist fire, the fireproofing of steel structures adds another trade that will lead to additional costs.

Fireproofing a steel structure / Source: Wikipedia

Precast Structures

Precast structures composed of hollowcore slabs, precast columns and precast beams are not very common in the United States. Even though hollowcore slabs are a very competitive product, making precast columns and beams at low cost remains a challenge in most regions.

The prestressed hollowcore slabs offer an unmatched span to depth ratio, but the bottom flange of the precast beams protruding under the hollowcore slabs will inevitably increase the floor to floor height.

Precast beam supporting hollowcore slabs / Source:Peikko

Precast beam supporting hollowcore slabs / Source:Peikko

Just like post-tensioned and cast-in-place, precast structures are non-combustible

The Peikko Frame:

The Peikko Frame was developed to encompass all the major benefits of the traditional types of structures in one simple system.

Speed of construction with minimal workforce

By utilizing long span prefabricated components such as 36 feet hollowcore slabs combined to 25 feet Deltabeam®, Peikko frames allow for exceptionally fast construction without an extended workforce. 

Peikko Frame Time LapseVideo / Source: Peikko

Another great advantage is that precast slabs do not require shoring allowing for sub-trades to access the job site faster.

Shoring of a conventional concrete slab  / Source:Peikko

Shoring of Deltabeam®  / Source:Peikko

The Peikko Frames are typically shored only for torsion when loading the precast slabs on one side of the beam. The few shoring posts are typically removed only a few days after the hollowcore slabs have been installed.

Superior span to depth ratio without protruding beams

It is well known that hollowcore slabs offer an excellent span to depth ratio since they are prestressed and light weight due to their longitudinal voids. However, when combined with traditional beams, the overall floor assembly can sometimes be increased by the full height of the beam profile.

Hollowcore slabs on wide flange steel beams / Source:Peikko

Additional floor depth when using wide flange beam vs. Deltabeam® / Source:Peikko

Deltabeam® is designed to only have its bottom flange protruding under the hollowcore slabs. Typically the flange will be less than 1” thick and will not interfere with HVAC or other systems.

Deltabeam® bottom flange supporting hollowcore slabs / Source:Peikko

Non-combustible structures

Peikko frames will result in exposed steel columns and Deltabeam (bottom flange) that do not require any fireproofing material applied on site.

Deltabeam® has been tested by Underwriters laboratories (UL) and is now listed for 1, 2, 3 & 4 hours without requiring any kind of fireproofing material. The reinforcement inside the concreted beam will assure the beam capacity remains sufficient in case of fire.

Interior of Deltabeam®  / Source:Peikko

Click to play the video:

Deltabeam® Fire test at UL  / Source:Peikko

The composite columns act in a similar fashion by relying on its reinforced concrete core to ensure the load bearing capacity in under fire.

Cost effective solution

Direct Costs

By using big prefabricated components major savings can be made. Less components means less time to erect a floor and large floor-plates can be installed with a handful of installers.  

Hollowcore slab installed on a Deltabeam® / Source:Peikko

One of the major components of the Peikko Frame is the hollowcore slab. Hollowcore slabs have been used in millions of square feet of buildings in America and have a proven record of being economical and highly capable.

Indirect Costs

In addition to having a competitive direct cost, the Peikko Frame leads to other significant savings.

When compared to post-tensioned structures, Peikko Frames allow for immediate access to the lower floors to other sub-trades (partition walls, plumbing, HVAC, etc.) since it requires minimal shoring.

The reduced weight of the hollowcore slabs also leads to savings for the foundations.

Having very minimal formwork reduces the cost of waste collection.

Compared to steel structures, the Peikko Frame will greatly reduce the floor-to-floor height. Also, hollowcore slabs are usually faster to install than traditional metal deck and requires less steps to be completed.

Extra Costs

Perhaps the most important cost reduction factor with the Peikko Frame is the most intangible: Predictability. Since the entire frame is prefabricated and modeled in 3D and it leaves limited probabilities for errors and omissions. Also, large prefabricated component are less impacted by weather during construction and erection can proceed even with relatively high winds, rain or snowfall.

Peikko Frames are also very easily enclosed during construction which leads to saving on heating when the construction site runs during winter time.

The Alternative to Post-Tensioned Structures
When a multi-story building requires long spans, a non-combustible structure and low floor-to-floor height, the Peikko Frame should be a system to consider. With it's prefabricated components, the Peikko frame will likely reduce the construction time and budget when compared to a conventional post-tensioned building. 

For more information:
www.peikkousa.com
1-888-PEIKKO-1 
1-888-734-5567

DELTABEAM FAQ

Deltabeam General Information

Why use Deltabeam?

Click on question to see the answer

DELTABEAM® is a superior composite beam enabling slim-floors for multi-story buildings of any type. Its composite action between steel and concrete allows for creative structures with large open spaces. Underwriter laboratories (UL) fire tests have proven DELTABEAM® has excellent fire resistance without any additional protection for up to 4 hours. Its shallow design decreases a building’s floor-to-floor height while eliminating conflicts with HVAC and MEP systems.

What are the savings that can be made with Deltabeam?

Compared to standard construction methods, erection time and required labor is often greatly reduced. With Deltabeam slim floor design, the number of stories can be maximized for a same building height. Therefore, the price per square foot is greatly reduced. Additionally, the slab spans can be increased, hence the number of column are reduced. Deltabeam's integrated fire resistance will often completely eliminate the need for fire proofing.

How many projects have used Deltabeam?

So far, over 12 000 projects around the world have used Deltabeam. Over 100 projects have been completed in North America since 2007. For more information on Deltabeam projects please visit: http://references.peikkousa.com/

When was Deltabeam first used?

The first project that used Deltabeam was built in 1989 in Finland

Who is responsible for the design of Deltabeam?

All Deltabeam are designed by Peikko’s engineers and Peikko is fully responsible for the design of its beams. Stamped and sealed shop drawings are part of Peikko’s offering. The EOR will be responsible for other elements of the building such as vertical elements (columns and walls), lateral stability (bracing, shear walls, diaphragm etc.) and foundations.

Who is responsible for the fabrication of Deltabeam?

Peikko has established a network of designated fabricators to produce Deltabeam. Peikko is responsible for the quality assurance of all its products. The selected fabricators are AWS and AISC certified.

Who is responsible for the Deltabeam detailing?

Peikko provides its own shop drawing for every part manufactured. Here is a sample of a standard shop drawing produced by Peikko.

How does Deltabeam compare in cost with a steel wide flange or precast concrete beam?

Deltabeam costs approximately the same as a precast beam but is significantly shallower and lighter. Although the price for a steel wide flange beam may be lower than a Deltabeam per linear foot, Deltabeam will often lead to significant savings in the overall cost of the project. For instance, lower floor to floor height will reduce cladding and HVAC Equipment costs. Also, reducing floor to floor height may allow for an additional floor for a given building height. Furthermore, Deltabeam's integrated fire resistance can eliminate the need for fireproofing.

In which type of project is Deltabeam the most cost effective?

Deltabeam can be utilized in any multi-story building, however it is most cost effective when utilized in a mixed-used application. For example, a residential building with indoor parking at the lower levels. Deltabeam is the most cost effective structural system when used in a rectangular grid layout. This way, hollow core slab spans can be maximized and will lead to a reduced number of columns and beams on a given floor layout.

Deltabeam design and features

How far can the Deltabeam span?

Deltabeam has the best depth to span ratio in the industry. The following table gives an overview of typical spans. Longer spans than those presented in the table shown below can be reached given that the beam can be deeper than the slab itself. Most of the time, Deltabeam's maximum span is limited to the hollow core slab span.

What is the optimal Deltabeam span and layout?

A rectangular grid layout is the optimal way to use Deltabeam, where Deltabeam spans vary between 20 and 26 feet with hollow-core slabs spanning between 27 and 42 feet.

How does Deltabeam achieve its fire resistance?

Deltabeam is UL listed for 1, 2, 3 & 4 hours without requiring any fireproofing material applied on the underside of the beam. The rebars inside the profile ensure that the beam has sufficient capacity under fire. The concrete inside the beam acts as a heat sink and slows significantly the rate at which the steel profile will rise in temperature. Fire rebar shop installed inside the beam

Heat distribution inside the Deltabeam profile under fire condition

Whatch this video

Has Deltabeam ever been used in high seismic area?

Yes, Deltabeam has been used in projects located in high seismic areas such as Honolulu(HI), Quebec City(QC) and Vancouver(BC).

Does Peikko provide design assistance?

Yes we do, from preliminary budget and layouts to construction site assistance, our engineering department will assist you through the entire design process.

Can Deltabeam support steel deck (metal deck)?

Yes, Deltabeam can be used with metal decks, hollow-core planks or wooden slabs.

Can Deltabeam be designed as an edge / spandrel beam?

Absolutely, Deltabeam can be designed as an interior beam as well as an edge beam.

Can Deltabeam be designed with a cantilever?

Yes, Deltabeam already been designed for cantilever up to 6ft.

Is Deltabeam produced with camber?

Yes, Deltabeams are manufactured with camber in order to accommodate the deflection limits specified by the building codes and to eliminate the need for shoring at mid span.

Should we design Deltabeam with multi-story or single-story columns?

Deltabeam can be designed with both multi-story and single-story columns. Single story columns allow usage of the negative bending moment of the beam. Therefore, overall beam weight and price may reduce by up to 20% .

However, since the entire load of the columns must be transferred through the beams, this type of construction is generally limited to 10 floors. Over 10 floors, continuous columns should be used.

Can Deltabeam be used with concrete columns or walls?

Yes, Deltabeam can be bearing either with a concrete column or wall. Peikko's PCs Corbel connection may be used to connect Deltabeam with vertical concrete elements.

Can Deltabeam be designed for point loads or non-uniform loading?

Absolutely, Peikko’s engineering department will gladly assist you with your specific loading requirements.

What types of plates are used to produce the Deltabeam?

All plates used to manufacture Deltabeam meet the requirement specified in ASTM A572.

Can holes be made in the Deltabeam for conduits?

Yes, however these holes must be coordinated with Peikko’s engineering department.

How are curves handled with hollow core slabs and Deltabeam?

Deltabeam can accommodate virtually any shape. Deltabeam edge beams can be produced with an integrated formwork that can be straight, skewed or curved.

How much height can I save with Deltabeam?

Total height gain depends on floors load, number of stories and depth of the beams and hollow core slabs. Height gain is typically 16" for 8" hollow core slab and up to 27" for a 12"mm deep hollow core slab.

How are cantilever balconies accommodated with Deltabeam?

There are two possibilities:
Cantilevering solid prestressed and precast slab:

Cantilevering the Deltabeam on the perimeter:

Connections

What are the possible connections with Deltabeam?

PCs Corbel welded to a steel column or casted in a concrete column can be used to connect Deltabeam to a column.

End plates can be added to a Deltabeam to weld it or bolt it to a steel column

Bearing surface such as top of a column or a wall can also be used as a connection Deltabeam can even be connected to another Deltabeam by a side connection designed by Peikko.

Can Deltabeam to column connections be designed as pin connections?

Yes, Deltabeam when connected with a PCs Corbel is consider as a pin connections since only shear stress will be transferred by the corbel to the column.

Can Deltabeam be designed as a moment connection?

Yes, Deltabeam when connected by a welded of bolted end plate will act as a stiff connection which can transfer bending moment from the beam to the column. Continuous Deltabeam will also provide moment connections between the column and the beam.

Shoring

Why do we need to shore Deltabeam?

Since Deltabeam is cambered, it doesn’t need to be shored for deflection. The reason why we need to shore the Deltabeam is to prevent torsion on the side of the beam where hollowcore is loaded first:

Where do we need to shore Deltabeam?

The shoring posts need to be placed at both ends of the beam under the web. Shoring must be placed on the side of the beam where the hollowcore slab is loaded first.

What is the capacity of the shoring posts that are required?

The posts must be able to support the full weight of the hollowcore slab bay. Typically the shoring post used must have a capacity of 20,000lbs.

Why do we not place any shoring posts in the middle of the span?

Since the beam is cambered, it is important to let the beam deflect during erection. If the Deltabeam is shored mid-span, cracking of the hollow-core could occur when removing the shoring posts.

Is there a way to completely avoid shoring?

Yes. Deltabeam has a very high torsion resistance due to its closed trapezoidal shape so given that the columns and the connections can accommodate this high torsion during the erection the shoring posts are not required.

How can I assure the structure is stable during erection? How is it braced?

Multiple systems can be used to temporarily brace the columns. We recommend using push and pull adjustable braces at least in the four corners of the building under construction as show below:

The braces can be secured in threaded holes at the top of the columns.

Grouting

When do I need to grout the erected floor?

Each floor must be grouted immediately after it is erected. A non-grouted floor provides no lateral stability and could collapse if multiple floors are erected without grouting.

In which order should I grout the components?

Composite columns should be grouted first, then the Deltabeam and finally the hollow-core keyways.

The hollowcore keyways can be grouted at the same time as the columns and beams when using a grouting bucket.

This method can also avoid requiring a concrete pump truck

How deep does the grout need to go at the end of the hollowcore slabs?

The grout will only go inside the hollowcore slabs a few inches. The hollowcore slabs are provided with plugs at the end of the cores to prevent grout from flowing inside.

How do I block the underside of the beam before grouting?

The formwork needed to block the openings under the slab is very minimal as shown in the pictures below:
Formwork prior to grouting

Once formwork is removed