This paper compares the constructability, cost and schedule of a new shallow flat soffit precast floor system with a typical precast floor system. The new system consists of continuous precast columns without corbels, partially continuous rectangular beams without ledges, partially continuous hollow-core planks (HC), and cast-in-place composite topping. The main criteria in the design of the new system includes: span-to-depth ratio of 30, flat soffit floor system, economy, and consistency with prevailing erection techniques. The new shallow flat soffit precast floor system has a depth and flat soffit comparable to cast in place systems. It has no constructability issues and costs $23.60/ square foot as compared to $21.90/square foot for a typical precast system. Although the new system takes 20% longer erection duration than typical precast system, the flat soffit and shallowness of the proposed system outweighs the cost and duration disadvantages. The continuous beam connections also have the added benefit of eliminating shear walls in moderate wind load conditions. This investigation uses a typical six story hotel or office building with 16 bays 30 ft (9.14 m) x 30 ft (9.14 m) for construction costs and schedule comparisons.

Precast concrete floor systems represent a major component of the cost and weight of precast concrete buildings. Hollow-core (HC) planking is considered the most common precast concrete floor system for residential and commercial buildings because of their economy, light weight, structural capacity, and ease of production and erection. However, the high thermal conductivity of HC planks hinders their use in radiant heated floor and roof applications where thermal insulation is needed. This paper presents the development of a precast/prestressed concrete sandwich floor panel that consists of an internal wythe of insulation and two external wythes of concrete similar to those used in sandwich wall panels. The main difference between the sandwich floor and wall panels is the design of shear connectors between concrete wythes to achieve full composite action under ultimate loads while simultaneously having an adequate creep resistance under ustained loads and acceptable deflection under live loads. Truss-shaped glass fiber-reinforced polymer ties, known as NU ties, were used as shear connectors because of their structural and thermal efficiency. The proposed floor panels have comparable weight and capacity to HC planks while being more thermally efficient and can easily be fabricated in standard casting beds with typical equipment, thus eliminating the high initial investment required for HC production. This paper presents the design, detailing, production, and testing of three 7.9-m-long (26-ft-long), 1.22-m-wide (4-ft-wide), and 200-mm-thick (8-in.-thick) specimens with 50-mm-thick (2-in.-thick) composite topping. The three specimens represent two different panel designs. One specimen has solid concrete ends and was designed for a total superimposed service load of 9.6 kPa (200 psf), whereas two specimens are fully insulated and designed for a total superimposed service load of 4.8 kPa (100 psf). The performance of the three specimens under flexure and shear loadings indicated that the proposed sandwich floor panels can achieve full composite action and have satisfactory structural performance and acceptable deflection characteristics. DOI: 10.1061/(ASCE)SC.1943-5576.0000213. © 2014 American Society of Civil Engineers.

A key economic value for multi-story office buildings, hotels, and similar structures is to have a shallow floor system that reduces the total building height and, consequently, reduces overall building cost. Additionally, minimizing the need for shear walls results in additional economy and flexibility in remodelling. This paper presents the development of a new precast prestressed concrete framing system that achieves both goals for buildings up to six-story tall built in areas of low seismicity. The proposed system consists of precast hollow core slabs, shallow inverted tee beams, multi-story columns, and cast-in-place topping, which are the common components in conventional precast construction. The proposed system eliminates the need for permanent concrete column corbels, and achieves continuity in the inverted tee beam through column block-outs to improve the system’s resistance to lateral and gravity loads. Hollowcore slabs are also made continuous to minimize the need for shear walls in the hollow core direction. An experimental investigation was carried out to verify the theoretical capacities of the system components and to ensure that demand was met for the conditions being considered. Testing was performed using a full-scale specimen representing the area around an interior column. Test results indicated that the system is simple to construct and connection capacities can be adequately predicted using strain compatibility and shear friction theories. The design and construction of an office building in Lincoln, NE was presented as a successful implementation of the new system.

Over the last few decades, the use of precast concrete components have been significantly increasing in building and bridge construction due to their quality, durability, and speed of construction. Precast components need to be fully connected to ensure the integrity, serviceability, and durability of the completed structure. Several proprietary grout-filled sleeves are currently being used to splice reinforcing bars of the adjacent precast components. These sleeves require very tight tolerances in precast production to ensure the alignment of the spliced bars, which usually results in using larger and more costly sleeves than needed. The objective of this paper is to introduce a non-proprietary bar splice sleeve that accommodates current production tolerances in addition to being economical and easy to produce. The design method of the proposed splice sleeve and the analytical investigation conducted using FE analysis are discussed. The experimental investigation conducted using two alternatives of the proposed bar splice sleeve is presented. Eighteen specimens for splicing #8 and #9 bars were tested using different sleeve lengths. Test results indicated that the proposed bar splice sleeve have adequate capacity to fully develop reinforcing bars while being simpler to use and more economical than current proprietary splice sleeve.