FAQ
GENERAL
Chapter 4 of the "PCI Manual for the Design of Hollow Core Slabs", Second Edition is a standard reference that engineers use to calculate horizontal shear transfer elements, i.e. collectors, chords, and drag struts. When considering the connection at the D-BEAM®, typically, the hollow core shear strength is less than the grouted beam's shear strength.
Since all section properties are available, the EOR is able to calculate stresses for all loading conditions.
Yes. Please call for further information. Additionally, all standard details are provided on our website.
For designing the GIRDER-SLAB® system in RAM engineers will let RAM select a standard WF shape but ignore the output. The engineer will then size the D-BEAM® girders from the D-BEAM® girder Design Tool located on our website. Since the D-BEAM®s are not normally used in a braced frame this procedure works well. If the D-BEAM® girders were located in a braced frame, engineers would again model it as a WF beam to obtain the axial load in the beam due to the lateral load.
D-BEAM®girder
Some Engineers have found that with camber and the heavier D-BEAM® girder, a span up to 25' with no tree columns can be achieved. The EOR is the sole determinant of the D-BEAM® girder span.
Yes, but consider that the bolts may interfere with the precast slabs.
As high as any other steel building. The D-BEAM® girder and the hollowcore plank carry the gravity loads. The height of the building is a function of lateral resisting system.
The design guide and details are graphic illustrations; the web openings in the D-BEAM® girder are not always going to line up with the openings in the hollow core slabs. When the web openings do not line up the rebar is placed on an angle or hooked to find its way into the openings of the hollow core. Note: Design Guide dimension tables show the web opening sizes for various D-BEAM® girder sections.
A572 gr 50 or A529 gr 50 flat bar are commonly rolled, you may also substitute rolled plate of equal or greater strength, if required splice welds must develop the full capacity of the cross section.
Our system does not anticipate spliced bars just as any engineer's design would not anticipate spliced wide flanges. When a fabricator deviates from the norm, his procedure is controlled by AISC requirements and all of his deviations must be submitted to the SER for review.
Although cutting lengths may fall at an opening in the web, there should be enough remaining web to transfer the shear to the end plate connection but this must be checked by the EOR. When the EOR specifies the "Tree Column Elevation S16" he can adjust the length of the "tree" so that the connecting D-BEAM® girders have at least 2" of solid web for the connections at each end. This should result in most of the project's D- Beams being of identical lengths. When checking these connections the EOR may determine the need for reiniforcement. The fabricator can fill in the missing web with plate or a doubler plate can be used.
The GIRDER-SLAB® system utilizes precast concrete slabs and steel components joined compositely by grout and steel reinforcing. Both precast and steel components have been used in seismic areas. The use of standard details allows the GIRDER-SLAB® system to adapt to the high seismic environment. (Concrete topping and reinforcing is usually required.)
This is intended to be an end plate shear connection, as shown in AISC Code on end plate shear connections. In order to preclude Fixity, employ one or more of the following; Use only enough bolts to transfer end reaction. Use a relatively thin plate. Limit the amount of welding between the top and bottom flanges and the end plate. Consider using 2 bolts in the web and 2 bolts below the bottom flange, vertically spread about 6" apart.
Hollowcore
Shimming the plank as required. Threaded Rods and Plates are also used to clamp the plank prior to grouting. A lightweight gypsum floor underlayment is often applied to the top of the plank to eliminate plank surface irregularities. All camber issues and concerns should be discussed with the plank supplier and erector.
Yes, plank has been used on hundreds of high end properties. A high strength gypsum underlayment topping product is recommended. Thickness can vary depending on plank span length. A 2" concrete topping can be used for structural reasons or when there are large expanses of a brittle floor finish (i.e.: ceramic tile).
Rebar is suggested to be #4 x 2'-0" long spaced at 24" 0/C max, and these reinforced cells require block outs. As for intermediate cells, grout has to be able to flow to create a monolithic system. EOR is the sole determiner of how much reinforcing is required and how often.
It depends upon the diaphragm loads and if they are needed for erection (see Girder-Slab typical details). Consult with your local hollow core supplier for availability of weld plates, alternative details may be suggested that will meet the engineer's requirements.
One method is that the hollow core supplier provides these cut outs in the plant and then provides a core plug to stop the grout from flowing more than required into the cell. Another method is the saw cutting of the top of the hollow core in the field and then removing the cut outs and placing them in the hollow core of the slab.
A concrete topping is not required for the 2 hour unrestrained rating. A 1-1/8" concrete topping is required for the 3 hour restrained rating.
This is a decision for the EOR and the erector. Each building is different. It involves stability; the amount of permanent bracing which is installed and the use of temporary bracing such as tie beams, cables, and or angles temporarily fastened to the columns and floor slabs. Some engineers and contractors will call for weld plates in the bottom of the plank, and field tack weld to the D-BEAM® girder. This technique is used so that in the event of freezing weather erection can continue while the grouting is postponed until weather conditions are more favorable.
Consult with your local plank supplier about his tolerances. Plank should be carefully detailed around steel columns to assure proper bearing and avoid interference. Clip angles are often added to columns for plank bearing. NOTE: Some engineers will stop steel bracing short of the "work point" to simplify plank & grout installation. A Plank detailer familiar with steel and plank projects is recommended.
If you have a choice, grout first then weld.
This is more a question for your precast supplier and we would advise you to check with them.
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