International Concrete Abstracts Portal

Reinforced concrete tilt-up panels provide a variety of functions in modern buildings. One of these is to resist in-plane shear forces due to wind or seismic loads. With architectural trends requiring increasingly larger openings, the panels will sometimes behave more like frames than shear walls. The mode of failure for frame panels subjected to large in-plane lateral loads is expected to be flexural hinging of the frame members. The research reported in this paper investigated the effect of hinge zone tie spacing on the ductility of concrete tilt-up frame panels. The results of tests carried out on six quarter frame panels with three different tie spacings are presented. It was found that hinge zone tie spacing can affect the mode of failure and have a significant influence on panel ductility. The hinge zone tie spacings tested were 100, 200, and 300 mm (4, 8, and 12 in.). The mode of failure for the 200 mm and 300 mm (8 and 12 in.) tie spacing specimens was buckling of the longitudinal steel reinforcement in compression after the cover concrete had spalled. The 100 mm (4 in.) tie spacing was observed to be adequate to prevent buckling of the longitudinal reinforcement after loss of the cover concrete. The100 mm tie spacing specimens failed via either local out of plane buckling of the entire hinge zone reinforcement cage, or by pullout of the longitudinal beam reinforcement resulting from bond loss within the hinge zone. The full frame displacement ductilities achieved for the 100 and 200 mm (4 and 8 in.) tie spacings were 5.7 and 3.9, respectively. The 300 mm (12 in.) tie spacing specimens failed to maintain the full design flexural strength beyond the yield displacement.

The strength and ductility of several tilt-up concrete wall panel connections are investigated analytically and experimentally in a series of monotonic and cyclic tests. For the connectors loaded in tension, experimental results do not support the capacity predictions based on the analysis, due to cone failure in the thin concrete sections. The tension tests showed good agreement in load-deflection behavior between monotonic and cyclic loading, indicating that simple monotonic testing would be adequate for further investigation of the strength and ductility of these connector types. The shear results demonstrated significant differences in load-deflection behavior between monotonic and cyclic loading. Most of the connector types tested did not show sufficient ductility to be used where ductility was a requirement. Further development is needed to produce economical connectors that demonstrate adequate ductility where required

Tilt-up concrete construction is commonly used in low-rise building construction. This report discusses many of the items that should considered in planning, designing, and constructing a quality tilt-up structure. Major topics discussed include design, construction planning, construction, erection, and finishing.

When slenderness ratios of load-bearing reinforced concrete walls resting on either continious or isolated footings exceed the limits of ACI 318-71 (klu/r 100), a detailed evaluation of slenderness is needed. Using numerical analysis procedures, a systematic accounting of the various factors affecting the behavior of wall panels is presented here, based on a column model of the panel. Also presented in this paper is a typical design aid of a slender wall having a thickness of 5 1/2 in. (14 cm) and resting on continious footings. A rational means of evaulating the effects of isolated footings on the ultimate capacity of the slenderness walls is also indicated along with a design example.

This state-of-the-art report outlines the historic background of the development of expansive cement concretes abroad and in this country, presents the relevant nomenclature, and summarizes the current status of expansive cements in the United States. The hydration chemistry of expansive cements is described, with em hasis o n the components necessary for the formation of ettringite. The important in factors the choice of proportioning of materials are discussed, as well as the products of reaction, and heat of hydration. Various factors are discussed, which influence the rate and amount of expansion of all three types of expansive cement concretes. These include the chemical composition, fineness and age of cement, water-cement ratio, mixing time, admixtures, aggregates, curing, temperature, restraint, and size and shape of specimens. Th e properties of expansive cement concretes are reported separately for shrinkage-compensating and self-stressing concretes. The properties considered include workability, bleeding, time of setting, unit weight and yield, expansion, creep, shrinkage, compressive and bond strengths, modulus of elasticity, Poisson’s ratio, coefficient of thermal expansion, and the resistance to various actions (deicer scaling, sulfate attack, cracking, and abrasion). Properties are also indicated on which no data are available at present. Field performance of shrinkage-compensating concrete is summarized. The in-fluences of restraint, aggregates, additives, ambient temperatures, forms, consistency, finishing, and curing are discussed. Examples of structural installations are presented, which include flat slabs, one-way pan joists, and two-way waffle slabs for parking garages, a folded plate roof for a bank, topping on a prestressed single tee parking deck structure, grade slabs and tilt-up panel walls for a department store, and an industrial floor. Five highway installations are described, including various spacings of contraction joints, continuously reinforced pavement as well as an unreinforced one, an application of self-stressing concrete, and the use of two bridge decks. The results of 17 tests on laboratory made structural elements of self-stressing concrete are summarized. These include tests on pipes, slabs, beams, frames, columns, and hyperbolic paraboloid. A brief review is given of some overseas experience. Needed areas of research and development are discussed with respect to expansive cements, material properties and behavior, and applications. An extensive bibliography is presented.