This paper presents a newly developed interior framing system for precast prestressed concrete multistory office buildings. The new system is optimized for gravity loads; however, it is also shown to have some features that would assist the structure in lateral load resistance. The system is composed of hollow-core slabs or double tees supported on 8 ft (2.40 m) wide inverted tee beams. The beams are voided to improve structural and erection efficiency and to allow for possible use as utility housing. A beam thickness of 16 in. (400 mm) is shown to be adequate for a 40 x 36 ft (12.0 m x 11.0 m) bay. The corresponding conventional system would require a much thicker 2ft (0.6 m) wide beam, thus increasing the structure height. The beams of the proposed system are made continuous in the field by means of a cast-in-place top flange and continuity reinforcement. Thus, the seismic resistance, positive moment reinforcement, and deflection are considerably improved. The proposed system does not require column corbels which are expensive to produce, nor does it require field shoring which complicates construction. A numerical design example of a typical interior span, including details of the beam as well as its connection with the column, is given. It is shown that the system meets all nonseismic design criteria of the ACI 318-89 Building Code; seismic design (Chapter 21) was not performed. An economic analysis is conducted on a two-story 163 x 183 ft (49. 7 x 55.8 m) office building. Costs are based on current prices in the Midwest region of the United States. Results of the analysis show a 13 percent savings over the conventional framing system. A spreadsheet computer program for structural design of the beam is available from the PC/ for Apple Macintosh microcomputers. The paper concludes with a brief description of an "all-dry" variation of the proposed system. It does not require cast-inplace concrete for structural integrity during erection, whilemaintaining the advantages of the proposed system.
