Why is the Hybrid composite steel floor joist system better than a concrete floor or a structural steel beam/metal deck system?

• The system is faster, stronger and easier to install.  Hybrid composite joist/girders offer solid reliable elevated slabs supported by proven floor joist.
• A Hybrid composite steel floor joist system is also significantly lighter than a concrete slab suspended floor;  this is safer in extreme stress situations such as an earthquake.  During an earthquake a Hybrid composite steel joist floor provides strength with flexibility, but also has less weight to collapse, crushing the floor below.

 System Description:

•  The Hybrid composite steel joist system uses a set of rollbars to provide internal stability to the joist when the concrete deck is being poured and also to provide support for the reusable plywood forms for the concrete deck.
• The deck is 3 inches of concrete with wire mesh reinforcement After the concrete is poured, the rollbars are removed and the plywood is stripped as soon as it meets the specified psi strength, and work begins on the next level.
• Mechanical and electrical systems fit easily through the open web on the individual floors, eliminating bulk-heads and increasing overall floor space.  It is also easy to place tubing for radiant heating in the slab and do it with a single pour.

The Hybrid composite steel joist system features a steel joist top chord embedded in concrete; the system of top and bottom chords of bent rods connected together reduces the vertical shear common in a standard truss.

The system provides an extremely rigid floor, and features UL and ULC ratings with PVC plumbing and mechanical duct openings without fire dampers.

True composite system

• The Hybrid composite steel joist system uses an open web steel joist with an S-shaped attachment on the upper chord that is embedded in the concrete deck, developing a composite action that results in greater strength and less weight.
• The Hybrid composite steel joist/girder system essentially consists of a hybrid concrete/steel T-beam in one direction and integrated continuous one-way slab in the other direction.  
• The concrete slab is reinforced with welded wire mesh
• The top chord functions as a “high chair”, developing negative moment capacity in the concrete slab causing it to behave as a continuous, one-way reinforced slab.

The top chord of the Hybrid composite steel joist/ girder system is embedded in the concrete and acts as a continuous shear connector.

• Another major feature is the use of the top chord of the joist in a multi-purpose function.
• First, it supports the secondary framing members of joist
• Secondly, it acts as a conventional top chord to support construction loads
• Thirdly, it is a continuous or substantially continuous, shear connector in the composite stage.
• Because of the composite or multi-purpose design, the joist depth can be considerably less than it would be in the non-composite stage and thus, decreases the weight of primary framing members.
• Because floor stiffness is increased by composite action, vibration and deflection are reduced substantially since there is a higher moment of inertia in the composite stage. A composite truss will have considerable greater stiffness than a non-composite truss of equal depths, loads, and span length. 
• Additionally, deflection of composite trusses will usually be one half to two thirds of the deflection of non-composite trusses.

 Metal deck is not required

• The Hybrid composite steel joist system is a forming system.  It is a poured in place forming system using plywood forming and then the plywood is removed.

Eliminate shoring requirements

• Eliminate the need for shoring or re-shoring, the system offers easy installation
• Different trades can be working simultaneously
• Eliminates costly scheduling problems
• Save weeks in erection time
• Less expensive erection cost

Concrete slab penetration issues

• The Hybrid composite steel joist system eliminates core drilling in order to penetrate through the concrete slab
• With the Hybrid composite steel joist system the plywood is installed and then the installation of the wire mesh. Prior to the concrete pouring, the other trades such as the electrician, plumber, etc. can easily attach an inexpensive standard sleeve to the plywood.  This sleeve could be plastic, Styrofoam, etc., commonly used by the various trades. 
• Their utility items go up through the sleeve.  After the concrete pour, the plywood is removed and the sleeve is pulled out with the plywood.  You now have the proper holes into the concrete slab to run pipes or other utilities through the concrete slab.
• With other systems, that use a metal deck, they have to core drill and they have to be extremely careful not to penetrate and damage the joist.  This can be an expensive process.
• In most other floor systems, the air conditioning supply grills require fire dampers.  The Hybrid composite steel joist does not require this fire proofing

Rigidity

• Live-load deflections are significantly reduced due to the composite action
• Shallower concrete thickness can be used because of the increased rigidity of the system resulting from the composite action.  In addition, the interlocking of concrete with steel provides excellent lateral diaphragm action with the composite joist acting as stiffners for the entire system.

 No primary bridging required

• Less materials and faster erection

 Plenum space

• UL approval
• The Hybrid composite steel joist UL test specifies all of the items and properties that have already been approved to be in the plenum space.  If a specific item is not in the test then it cannot be UL approved.
• Typical items in the plenum would be wood blocking, PVC plumbing, HVAC flex duct, etc.
• Extra usable space
• With the joist at four feet on center and no required bridging more usable space is available

Material reduction

• By selecting composite steel joist/ girders instead of beams, it is possible to reduce the number of columns and foundations by allowing for longer spans.

 Long spans

• Composite steel joist span-to-depth ratio permits the use of shallower joist for any given span
• Larger spans result in larger column spacing, increasing usable floor space
• Less concrete and reinforcing steel required, more economical

 Acoustical properties

• STC:   Sound transmission class of STC 57
• IIC- Impact Insulation Class – IIC 30
• Vibration issues :
• The Hybrid composite steel joist floor system is one of the leading concrete floor systems in addressing airborne noise and provides unparalleled sound reduction capabilities.  Airborne noise is caused by unwanted vibration.
• The Hybrid composite steel joist assembly has an IIC rating of 30 on bear concrete, similar to a solid 6 inch slab   
• Less expensive to achieve the desired STC and IIC rating assembly

Fire protection

• A major advantage of the Hybrid composite steel joist system is its fire ratings.  It has been tested at both UL and ULC.  Because the top chord is embedded in concrete, the deck works as a heat sink so it keeps the joist much cooler than the standard joist or beam would be.  The system gets a one, -two-or three-hour fire rating with only a half-inch of drywall.
• Non-combustible
• One hour and two hour fire rated assemblies available
• Less expensive to achieve the desired fire rating assembly
• Mechanical duct openings without fire dampers

Sound and fire rating assembly

• Hybrid composite steel joist/girder systems
• 0.5 inch drywall ceiling
• 3 inch concrete slab

 Lighter weight system

• The composite joist floor system uses less concrete compared to conventional flat plate slabs
  • Less concrete results in less weight and subsequent reductions in size and the cost of elements used in primary structure and the foundations
  • Weight reduction also has a positive influence in the design of lateral bracing systems controlled by seismic activity
  • This results in lower structural framing cost as compared to other systems
• The Hybrid composite steel joist/girders are very efficient, allowing a reduction in the joist weight for any given joist depth
• Because it is a composite system using a concrete deck with steel support, the Hybrid composite joist system is very light
  • The use of joist girders as opposed to wide flange beams over the same distance between the columns represents weight savings of up to 25%.
  • The high-strength-to-weight ratio of the joist permits the use of smaller and lighter beams, columns, footings, and foundations.  It is not uncommon for joist girders to be 40% lighter than the beams which they replace.
  • Weight savings from the joist design reduces building cost
  • Less foundation impact and cost reduction

Provides more open usable space

• Large column-free areas offer maximum flexibility on floor layouts

Lower Floor-to-Floor Heights

• The more efficient and stiffer composite joist and girders make it possible to support a given load with a shallower joist
• Ability to route the new mechanical heating, ventilation ducts, plumbing, and electrical lines through the joist open webs as well as providing support for them. By threading these items through the joist, instead of under them, floor-to-floor height can be reduced to the minimum allowed by code.  Customized web openings and configurations can be provided for large ducts.
• This means fewer mechanical joints, and easy chasing of plumbing and electrical services
• The volume of air needed for heating in winter and air conditioning in summer is therefore reduced
• Ease of relocating and/or moving future HVAC during the life of the building.
• Better plenum space utilization
• Composite steel joist and joist girders allow artificial and natural light to pass through their open webs

Large utility openings

• Round 8 inches
• Square 6 inches
• Rectangular 9 inches by 5 inches

Extremely fast and easy erection

Multiple processes can take place simultaneously during construction on one floor.  Faster floor-to-floor installation allows other trades to perform their task sooner.

• Aggressive construction schedules can be achieved
• Less expensive to erect than stand alone steel or concrete systems
• The Hybrid composite steel joist floor system provides a rigid working platform.  Masonry walls or tie beams may be filled, when required, using the Hybrid composite steel joist floor as a working deck.  The composite steel floor joist supports itself during installation, so extra support jacks are not necessary.
• The entire building envelope is erected by the same erection team
• Steel structural insulated exterior and partition wall panels
• Composite steel floor joist systems
• Composite steel transfer slab systems
• Wider composite steel joist spacing reduces the number of joist to be erected and, when required, the number that has to be fire proofed
• Simplified erection
• Fewer and simpler connections
• All weather construction
• Faster revenue generation

Efficient system

• The roll-bars and forming sheets are reusable.  There is very little waste material.  Everything is either used in the floor or can be re-used on another floor.

Composite Transfer Slab Systems

• The Hybrid composite transfer slab system consists of composite joist, composite girders and a composite slab.  Optional composite steel-concrete columns are also available.
• In most applications, the composite transfer slab will carry the gravity loads for the upper floors and transfer the loads to the columns and the foundation footers.  This allows the first level slab to support a more manageable one story of lateral loads.

Composite Columns

• Composite columns can be an economical solution for cases where additional load capacity is desired over that available with steel or concrete columns alone.  The Hybrid concrete columns can either be encased or filled.
• Encased composite columns (steel shapes embedded in concrete) and filled composite columns (hollow structural sections (HSS) filled with concrete)
• The performance of the various Hybrid composite column systems is better than the sum of responses of the parts taken separately.  For example, in a concrete-filled steel tube caisson the steel tubing resists flexural tension efficiently while confining the concrete core as the core resists axial compression, whereas it also stabilizes the steel casing.
• Concrete encasement of structural steel shapes can provide lateral stability to the steel shape, restraining local buckling as well as reducing the slenderness ratio below that of the steel shape alone.

Advantages of Composite Columns

• Smaller than cast-in-place or precast concrete
• Fire resistant without the need for additional fire proofing materials
• Stronger than stand alone steel or concrete columns
• Superior compression and bending characteristics
• Excellent blast loading characteristics
• Easier and less expensive to install
• Composite columns are also excellent for lower levels of multi-story buildings to carry the vertical loads at the high floor-to-floor heights often used at these levels

Customized Hybrid composite steel joist and girder designs can be created for any given loading and serviceability requirements.

Send us your completed or preliminary plans for a free but thorough value engineering analysis.

For additional information and system pricing, please contact us