A new semi-empirical concrete shrinkage and creep model called the CPRH Model is proposed and calibrated. The new model proposes a coupling between autogenous and drying shrinkage using a volume-average pore relative humidity and treats drying creep as an additional stress-dependent shrinkage, linking together all these phenomena. The proposed expressions are designed to facilitate traditional integral-type analysis, but also uniquely support ratetype calculations that can be leveraged by analysis software. Model calibration uses the Northwestern University (NU) database of creep and shrinkage tests to determine new model parameters. The proposed model uses minimal inputs that are often known or may be assumed by the design engineer. Comparison of the proposed model to historical time-dependent models indicates that the new model provides a superior fit over a wider range of inputs.

One of the critical aspects of masonry failure is the shear capacity of the composite brick-mortar assemblage. In the last four decades, an increasing effort has been devoted to study the shear behavior of masonry structures. Different test approaches have been used to determine the shear strength of masonry, including laboratory tests and in-place measurements. In this paper, a close view of the test method used for the in-place measurement of masonry shear strength is taken, using an innovative approach based on image correlation techniques. A series of in-place shear tests were conducted at one of the masonry infilled reinforced concrete (RC) frames tested at the University of Colorado Boulder, Boulder, CO, within the framework of a comprehensive NSF-NEESR-SG project at the University of California San Diego, San Diego, CA. Initial cohesion and friction angles were determined for the infill wall, and the lack of uniformity along the shear failure planes was investigated with the aid of finite elements and digital image correlations.

This study was part of a large-scale experimental program on the Brite-Euram research project: “Rational Production and Improved Working Environment through Using Self-Consolidating Concrete (SCC).” The University of Paisley was responsible for a major part of Task 4 on the investigation of in-place properties and their variations in practical structural elements cast with SCC. Structural performance of full-scale beams (200 x 300 x 3800 mm) cast using ordinary concrete and SCC with two configurations of reinforcement bars were investigated. A fiber beam cast with SCC containing steel fibers was also tested. SCC and ordinary concretes having standard compressive cube strengths of 35 MPa (Class C35) and 60 MPa (Class C60) for housing and civil engineering applications, respectively, were used to cast a total of eight beams. One beam of each pair of beams was tested in flexure to determine the load-deflection capacity; the second one provided core samples to determine the uniformity of the distribution of compressive strength along the length of beams. The core test results were expressed as estimated in-place cube strength in accordance with British standard practice and were compared with strengths obtained from standard cubes cured. In general, the in-place compressive strengths of SCC were closer to standard cube strength than those of ordinary concrete. The distribution of in-place properties along the beams was found to be uniform for both SCC and ordinary concrete, and the maximum strength difference was less than 7%. At service load, there were more and wider cracks with greater penetration with the reference mixture than with the SCC of Class C60. The mode of failure and load deflection response of the beams cast with SCC and ordinary concrete were similar. For concrete Class C60, it was observed that the ultimate moment capacity of the SCC beam was comparable with the reference beam and the maximum deflection of the SCC beam was slightly higher than that of the reference beam.

Although concrete is known to deteriorate both in strength and stiffness when subjected to large numbers of load applications, especially when stress reversals are involved, relatively little is known about its fatigue behavior and specifically damage accumulation in the low-cycle fatigue range. Herein, the results of an experimental investigation are reported, which had the objective of measuring the energy-dissipation capacity of concrete with and without fiber reinforcement under uniaxial stress cycles. This test program is the first phase of a major investigation currently underway at Columbia University to establish a data base that can be used to develop damage prediction tools and facilitate low-cycle fatigue analysis of concrete and concrete members subjected to arbitrary load histories. A new energy-based damage index is proposed, which is well suited for quantifying the concrete's residual strength and predicting its remaining life.

Fracture and impact resistance are among the improved attributes of fiber reinforced concrete (FRC). Toughness, which is a measure of the energy-absorption capacity, is used to characterize FRC's ability to resist fracture when subjected to static, dynamic, and impact loads. There is still debate on how toughness should be measured, interpreted, and used. Results from the first phase of a six-university study funded by the Concrete Materials Research Council-American Concrete Institute and the National Science Foundation are presented in this article. The first phase includes specimen size, fiber volume content, fiber type, and the effect of a notch as the primary parameters of investigation. Results from the tests including toughness and other important properties such as stress at first crack, ultimate strength, and the elastic modulus as influenced by the preceding parameters are presented and discussed. The importance of making accurate deflection measurements and the influence of these measurements on the toughness and other flexural characteristics are discussed. Conclusions are made with regard to lessons learned from the inter-university testing program, drawbacks of some currently used measures of toughness, observed material property trends, and a possible alternate measure of toughness.