Hollowcore planks are extruded at typical 4′-0″ wide planks.  When larger blockouts in the floor framing are placed within the span, hollowcore hangers will be used to eliminate full sections of hollowcore.  The hollowcore hanger assembly is designed specifically per the project requirements and installed on the end of the hollowcore at the plant after the plank is extruded.  The hanger allow for bearing on the adjacent planks, which may require a certain portion of the hollowcore void to be filled solid at the bearing location.  Hangers can have bearing on both the adjacent plank or CIP walls if needed.

It is common for hollowcore to have bearing directly on top of either precast or CIP walls.  Top of wall elevations are coordinated and bearing surface should be level and smooth.  Reinforcing that is embedded in supporting wall should be installed vertical and then field bent over after hollowcore is erected.  Once topping slab is poured, blockouts in the end of hollowcore voids allow for topping concrete to fill voids up to a specific distance.  Void dams pushed into voids onsite allow for voids to be only filled at hollowcore ends.

Hollowcore shear keys need to be grouted after planks are erected into final position.  This is completed prior to the 2.5″-3″ topping pour.  The grout mix should consist of a 1:3 cement/sand ratio or a pre-packaged grout that will yield a minimum compressive strength of 3,000 psi.  Backer rods are recommended to be installed at the lowest point of the shear key so grout does not leak through any gaps.

Often either precast or CIP walls that support hollowcore extend up past the hollowcore bearing elevation.  In this scenario, hollowcore ledgers are used to support planks.   Embeds are installed in supporting walls during fabrication that allow tolerance for specific ledger elevation installation. Ledgers are installed onsite and some shimming can be expected to fill any gaps between embeds and ledger.  Bearing pads are placed on ledger and hollowcore is erected.  Once topping slab is poured, blockouts in the end of hollowcore voids allow for topping concrete to fill voids up to a specific distance.  Void dams pushed into voids onsite allow for voids to be only filled at hollowcore ends.

Wires or mechanical anchors can be designed for use suspended from the hollowcore plank to support suspended ceilings, electrical conduits, plumbing or mechanical equipment.   Coring of the hollowcore planks if required should occur in the middle 1/3″ of void.  Void locations and quantity differ depending on the hollowcore depth cross section.

Column to column connections are typically used on taller structures where multiple columns lengths are required to frame structure or situations where hoisting weight is restricted and shorter columns are spliced together.  NMB splice sleeves are a common type 2 coupler used for column connections.  Rebar is constructed protruding from top of lower column and then cut to a specific distance above the foundation as required by size of NMB splice sleeve.  Female slice sleeve is embedded in precast and placed over protruding foundation rebar.  Once connection is complete at desired elevation, high strength mortar (that is provided solely by NMB manufacturer) is ejected into the sleeve via grouting tubes to complete connection.

Precast Inverted Tee beams frame into columns and have bearing on column corbels.  Steel angle is mounted across the inverted tee ledge where they intersect with columns to allow precast Double Tee, Hollowcore or Solid Slabs to have bearing area at column.

Precast beams can have bearing on top of columns when required.  Splice couplers that extend a dowel up past top of column are typically used.  Inverted Tee beams that bear directly on column have corrugated grout tubes embedded to allow extended dowel to overlap.  Grout tubes are filled once beam (resting on bearing pads) is at correct elevation.

NMB splice sleeves can be used in a variety of precast products that require a type 2 coupler. Rebar is constructed protruding from foundation and then cut to a specific distance above the foundation as required by size of NMB splice sleeve.  Female slice sleeve is embedded in precast and placed over protruding foundation rebar.  Once connection is complete at desired elevation, high strength mortar (that is provided solely by NMB manufacturer) is ejected into the sleeve via grouting tubes to complete connection.

V-Pocket base connections are typically used when design connection performance does not allow for a grout tube connection.  V-pocket connection require a CIP embed to be installed in the foundation prior to precast installation.  Once panel is shimmed to correct elevation, steel tabs are welded between CIP embed and V-shaped precast embed to complete connection.  Access needs to be considered when using connection near columns or other site obstructions.