Finite element modelling of concrete-filled steel stub columns under axial compression

Engineering properties of inorganic polymer concretes (IPCs)

At present, the cement industry generates approximately 5% of the world’s anthropogenic CO2 emissions. This share is expected to increase since demand for cement based products is forecast to multiply by a factor of 2.5 within the next 40 years and the traditional strategies to mitigate emissions, focused on the production of cement, will not be capable of compensating such growth. Therefore, additional mitigation strategies are needed, including an increase in the efficiency of cement use. This paper proposes indicators for measuring cement use efficiency, presents a benchmark based on literature data and discusses potential gains in efficiency. The binder intensity (bi) index measures the amount of binder (kg m−3) necessary to deliver 1 MPa of mechanical strength, and consequently express the efficiency of using binder materials. The CO2 intensity index (ci) allows estimating the global warming potential of concrete formulations. Research benchmarks show that bi ∼5 kg m−3 MPa−1 are feasible and have already been achieved for concretes >50 MPa. However, concretes with lower compressive strengths have binder intensities varying between 10 and 20 kg m−3 MPa−1. These values can be a result of the minimum cement content established in many standards and reveal a significant potential for performance gains. In addition, combinations of low bi and ci are shown to be feasible.

Measuring the eco-efficiency of cement use

Time-dependent reliability of deteriorating reinforced concrete bridge decks

In this paper several design methods have been developed that can be used to conservatively estimate the strength of circular thin-walled concrete filled steel tubes under different loading conditions. The loading conditions examined include axial loading of the steel only, axial loading of the concrete only, and simultaneous loading of the concrete and steel both axially and at small eccentricities. Recent tests on circular concrete filled steel tubes have been used to calibrate and validate the proposed design methods. The test specimens were short with a length-to-diameter ratio of 3.5 and a diameter thickness ratio between 60 and 220. The internal concrete had nominal unconfined cylinder strengths of 50, 80, and 120 MPa. The bond (or lack of) between the steel and internal concrete was critical in determining the formation of a local buckle.

Design of circular thin-walled concrete filled steel tubes

Stress-strain relationship of confined and unconfined concrete

A stress–strain model for uniaxial and confined concrete under compression

Modeling of unreinforced masonry walls under shear and compression

Hyperelastic constitutive modeling under finite strain

Reported in this paper are the test results for 68 eccentrically loaded conventional and high-strength concrete columns. The columns were 150 x 150 mm (5.91 x 5.91 in) at the mid-section and haunched at the ends to apply the eccentric loading and prevent boundary effects. Concrete strengths used were 40, 55, 75, and 90 M.B.A. (5800, 8000, 10,900, and 13,100 psi) with load eccentricities of 8, 20, and 50 mm (0.32, 0.79, and 1.97 in). The columns had either 2 or 4 percent longitudinal reinforcement and tie spacings of 30, 60, or 120 mm (1.81, 2.36, or 4. 72 in). The ultimate strength of the columns is compared to the strength predictions based on the ACI 318-89 rectangular stress block parameters. The predictions compare reasonably well, although lower strengths than predicted occurred for some high-strength concrete specimens. Ductilities are calculated based on the area under the load versus average strain plus curvature times eccentricity relationship. This measure showed a weak correlation with the confinement parameter adopted. Strains in the tie reinforcement were measured at the side face for some of the medium and high- strength concrete columns. The measured strains were not at yield when the peak load was reached.

Mario M. Attard

Papers

Stress-strain relationship of confined and unconfined concrete

A stress–strain model for uniaxial and confined concrete under compression

Modeling of unreinforced masonry walls under shear and compression

Hyperelastic constitutive modeling under finite strain

Experimental tests on eccentrically loaded high-strength concrete columns