International Concrete Abstracts Portal

This paper presents an overview of shear analysis and design based on the ACI 318-19 Building Code Requirements for Structural Concrete as it relates to an introductory reinforced concrete course. The important content related to this topic is summarized and several effective active learning strategies and pedagogical resources are presented to augment and enhance student learning for this challenging topic. The description of each active learning activity also includes a discussion of the underlying pedagogical theory, an estimate of preparation and implementation time, and recommendations for implementation. The paper also highlights lessons learned from the authors based on observations from several years of instruction.

Current European seismic regulations do not cover the seismic design of flat plate structures (denominated flat slabs in Europe and in the following) The results of full scale testing on a two-story flat-slab frame are intended to contribute to future code developments are reported in the paper. The design of the specimen complied to the general specifications in the European seismic code for secondary elements i.e. non-seismic resistant. An extension of the approach proposed by ACI318 was used to predict the ultimate drift capacity of the connections. A first testing phase subjected the structure to seismic actions simulated by the pseudo-dynamic technique, including numerical models of shear walls. In a second phase, the frame was tested for cyclic loading up to 2.5% global drift ratio firstly, followed by the addition of strengthening, and a second cyclic test was done up to 6% global drift ratio. The results are compared to the state of the art tests regarding reduced and full-scale tests carried out in North America. The research developments aim to further the preparation of new European seismic regulations for flat slabs, by including analytical models to predict the ultimate rotation capacity of the connections as a function of the gravity shear.

A bridge pier cap beam supporting girders of two unequal spans was designed per AASTHTO LRFD Bridge Design Specifications (AASHTO LRFD BDS-17) and the ACI 318 Building Code Requirements for Structural Concrete (ACI 318-19) with consideration of torsional effect. Envelopes of bending moment, shear, and torsional moment are given in the problem statement as the result of a comprehensive structural analysis on the bridge. Flexural design is presented firstly based on the bending moment envelope to determine the required area of longitudinal reinforcement. Then shear and torsion design is presented to determine the required area of transverse reinforcement and additional longitudinal reinforcement. Based on the design calculations, the arrangement of reinforcement is illustrated in a cross-section view for the cap beam. Comparison between the two approaches is also included in terms of the equations used and areas of shear and torsion reinforcement determined.

The effect of discontinued, randomly distributed steel fibers on the effective moment of inertia (𝐼!) of lightly reinforced flexural members is evaluated through the testing of three pairs of specimens under four-point bending. The specimens consisted of a simply supported, 3660 mm long, 254 mm deep, and 610 mm wide one-way slab strip. All slab specimens contained minimum flexural reinforcement according to the ACI 318-14 Building Code. The first pair featured regular concrete (no fibers), while the second and third pairs included steel fibers in a volume fraction (𝑉") of 0.26% and 0.38%, respectively. Beyond cracking, a substantial drop in the flexural stiffness was noticed in all specimens. The slabs with fibers, however, exhibited stiffer post-cracking response compared to their regular concrete counterparts. At yielding, a well-distributed cracking pattern was noticed in all test slabs, with maximum cracks widths of approximately 0.5 mm. It was found that the equation proposed by Bischoff (2005) to estimate the effective moment of inertia for concrete beams fits well the experimental data of the fiberreinforced concrete slabs, given that the stiffening factor is set equal to one.

This paper provides a practical example of the torsion design of an inverted tee bent cap of a three-span bridge. A full torsional design following the guidelines of the ACI 318-19 building code is carried out and the results are compared with the outcomes from CSA-A23.3-04, AASHTO-LRFD-17, and EN 1992-1-1:2004 codes. Then, a summary of the detailing of the cross-section considering the reinforcement requirements is presented. The objective of this paper is to illustrate the application of ACI 318-19 when designing a structural element subjected to large torsional moments.