ACI 533.1R-02 Design Responsibility for Architectural Precast-Concrete Projects.
2.2—Engineer of record The EOR has responsibility for describing loading on precast element inserts and loading criteria (combinations, wind, seismic) for the structural design of the complete structure and the effects of the precast erection sequences on individual structural members, for example, steel spandrel beams when numerous concentrated panel loads are placed on them. The EOR should anticipate these loadings and provide means to support them. Responsibility for the precast-concrete design can be delegated to someone else, such as the precaster or precast engineer. The EOR should consider the consequences of the weight and eccentricity of the panels when designing the supporting structure. The EOR should also determine where, when, and what type of loading is to be assigned to the panels and the structure. The EOR has the responsibility of reviewing the delegated design work for compatibility with the overall structural design. This does not, however, relieve the preparer of the design work of the responsibility for doing it correctly.
Panels typically span column to column and are supported on or near the column. The EOR should determine and show on the contract documents the locations for supporting the gravity and lateral loads, including midpoint lateral (tie-back) connections, if necessary. The panel loads are routinely provided by the precaster to the EOR. The EOR determines during assembly (erection) drawing review whether or not the structure is adequate, within defined deflection limitations, to resist the loads and forces. The EOR should also provide sufficient information on seismic detailing. It is important that preliminary meeting(s) with the architect, EOR, and precasters be held before structural members are ordered, fabricated, or both, so that panel sizes, shapes, and basic connections, as well as their locations can be established (refer to the Appendix).
The EOR will know whether or not a spandrel panel is designed to transfer load to the columns, but the exact location of the load transfer can vary from precaster to precaster. For example, spandrel panel loads can be transferred from near the panel bottom or from near the top. The gravity supports of precast-concrete panels are almost always eccentric to the centerline of the supporting steel or concrete member. A concrete member is generally stiff and strong enough in torsion so that this is not a problem. Because the precaster does not design the columns or beams, the EOR should design to prevent excessive deflection and rotation of the supporting structure during and after erection of the precast concrete, as well as determine the need for diagonal bracing or web stiffening (CASE National Guidelines Committee 1994; CASE Task Group on Specialty Engineering 1996). The contract documents should address the issue of reimburse- ments to the EOR for engineering the bracing or reinforcement of the structure if the precaster’s panelization changes the EOR’s designed connection locations. In some areas, the precaster is responsible for designing the bracing and may also supply the secondary steel. These responsibilities should be clearly addressed in the contract documents and discussed in a prebid meeting.ACI 533.1R pdf download.