Office/Retail

Precast exterior cladding can be solid or insulated panels, orientated horizontal or vertical and have bearing on CIP or total precast framing systems.  Typically cladding is panelized horizontal to fit between the floors with “punched” windows blockouts (blockouts that do not extend to edge of panel).  Gravity and tie connections designed with tolerance allow for proper positioning of panel into final position.  Interior finishes can be furred out to include desired appearance or precast face can be conditioned to be painted.  With proper panel layout and coordination, glazing option installed at precast plant are available.

Gravity loads and the transfer of these loads to the supporting structure. Vertical (gravity) loads are parallel to the plane of the wall at an eccentricity influenced by the geometry of the wall, location of load, and manufacturing and erection tolerances.  Tolerance and adjustable are important when design gravity load connections as these connections will set the final position of precast.  Jacking bolts are often used to set precast height while welding tabs between embedded angle and CIP embeds allows for adjustment in position before welding into final location.

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.

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.

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.

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.

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.

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.

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.