International Concrete Abstracts Portal

Results from the test of a large-scale coupled-wall specimen consisting of two T-shaped reinforced concrete structural walls joined at four levels by precast coupling beams are presented. Each coupling beam had a span length-depth ratio (ln/h) of 1.7, and was designed to carry a shear stress of 7vfc' [psi], (0.59vfc' [MPa]). One reinforced concrete coupling beam was included along with three strain-hardening, high-performance fiber-reinforced concrete (HPFRC) coupling beams to allow a comparison of their behavior. When subjected to reversing lateral displacements, the system behaved in a highly ductile manner characterized by excellent strength retention to drifts of 3% without appreciable pinching of the lateral load versus drift hysteresis loops. The reinforced concrete structural walls showed an excellent damage tolerance in response to peak average base shear stresses of 4.4vfc' [psi], (0.34vfc' [MPa]). This paper presents the observed damage patterns in the coupling beams and the structural walls. The restraining effect provided by the structural walls to damage-induced lengthening of the coupling beams is discussed and compared with that observed in component tests. Finally, the end rotations measured in the coupling beams relative to the drift of the coupled-wall system are also presented.

Several studies showed that the eccentricity between beam and column connections has a detrimental effect on the joint shear strength. With regard to this issue, ACI 318-08 restricts the average shear stress on a horizontal plane within the joint, which equals to the effective joint width times column depth. The formula of effective joint width given in ACI 318-08 may be too conservative for eccentric beam-column joints. This paper suggested a more rational formula of effective joint width associated with the softened strut-and-tie (SST) model for eccentric beam-column joints. Using the proposed effective joint width, the shear strength predictions of SST model agreed well with the results of 18 eccentric joint specimens failed in shear. Furthermore, together with the proposed effective joint width, several available definitions for effective joint width are also used as comparisons to estimate joint shear strength of collected database for eccentric and concentric joints using ACI 318-08 code design equation. The proposed effective joint width was successfully verified with available database of beam-column joints with or without eccentricity in literature.

This CD-ROM consists of 29 papers that were presented at technical sessions sponsored by Joint ACI Committees 343, 445, and 447, at the ACI Fall 2009 Convention in New Orleans, LA, in November 2009. The papers represent state-of-the-art advances in knowledge on shear and torsion. Note: The individual papers are also available. Please click on the following link to view the papers available, or call 248.848.3800 to order. SP-265

This paper describes the structural behavior of precast, prestressed concrete sandwich wall panels reinforced with carbon fiber-reinforced polymer (CFRP) shear grid to achieve composite action. The study included testing of six full-scale sandwich wall panels, each measuring 20 x 12 ft (6.1 x 3.7 m). The panels consisted of two outer prestressed concrete wythes and an inner foam core. The study included two types of foams and several shear transfer mechanisms with different CFRP reinforcement ratios to examine the degree of composite action developed between the two concrete wythes. All wall panels were simultaneously subjected to applied gravity and lateral loads. The paper also presents a general methodology to determine the behavior of fully and partially composite wall panels. The effects of imperfect connection between the two concrete wythes are considered by varying the total shear force transmitted through the shear connectors at the interface. The shear flow capacity of the insulating materials as well as the CFRP shear grid is determined using the proposed approach. The influence of the degree of the composite interaction on the induced curvature and slip-strain behavior is presented. A simple design chart for estimating the flexural capacity of the wall panels with different shear reinforcement ratios is proposed.

Recent calibration of ACI 318-08 for concrete structures was focused on the flexural capacity. The objective of this paper is to develop the statistical parameters for shear capacity of reinforced concrete beams. The capacity of shear reinforcement is a function of steel cross section area, yield strength, and spacing of stirrups. In this paper, the capacity of concrete is considered using ACI formulas and other shear capacity models available in literature. The analysis is performed for various reinforcement ratios, longitudinal and transverse, including beams without web reinforcement. The statistical parameters of resistance are determined from the test results. The reliability analysis is performed, and it serves as a basis for the selection of resistance factors. The selection criterion is closeness to the target reliability index. Recommended values of resistance factors are provided for each of the considered shear capacity methods.