Based on the equilibrium, continuity, and energy principles of multiphase porous media, a thermal-hydro-mechanical coupling model was developed for concrete upon freezing. To solve the governing differential equations, a three-dimensional finite-element analysis is performed based on the software program Comsol Multiphysics. Finally, temperature distributions, frozen water contents, and strains as a function of freezing time are predicted. A comparison of the analytical results with available experimental data for concrete mortars illustrates the validity of the proposed model. This numerical model can be used to assess the effect of cooling rate, the role of pore-size distribution, the role of permeability, the effect of cross section size and shape, the effect of superimposed stresses attributable to applied loads, and other factors that cannot easily be evaluated by current tests.

The orientation of steel fibers in magnetically driven concrete and magnetically driven mortar was experimentally studied in this paper using a magnetic method. In the magnetically driven concrete, a steel slag was used to replace the coarse aggregate. In the magnetically driven mortar, steel slag and iron sand were used to replace the fine aggregate. A device was established to provide the magnetic force. The magnetic force was used to rotate the steel fibers. In addition, the magnetic force was also used to vibrate the concrete and mortar. The effect of magnetic force on the orientation of steel fibers was examined by comparing the direction of fibers before and after vibration. The effect of magnetically driven concrete and mortar on the orientation of steel fibers was also examined by comparing specimens to normal concrete and mortar. It is shown that the fibers could rotate about 90° in magnetically driven concrete. It is also shown that the number of fibers rotated in magnetically driven mortar was much more than in mortar vibrated using a shaking table. A splitting test was performed on concrete specimens to investigate the effect of fiber orientation. In addition, a flexural test was also performed on mortar test specimens. It is shown that the orientation of the steel fibers in magnetically driven concrete and mortar affects the strength of the concrete and mortar specimens.

The compressive response of hollow section, centrifugal concrete-filled GFRP tube (HS-CFGT) members is examined experimentally and reported analytically in this paper. A total of 17 specimens separated into two groups were tested; the specimens in each group were of four different lengths and included thirteen straight columns and four tapered columns. The details of the test rigs, procedures as well as key test observations composed of ultimate-moment capacities, load-displacement curves, and failure modes were truthfully reported. The test results were analyzed to evaluate the influence of initial eccentricity on the structural performance. Therefore, the aim of this paper is: (1) to propose a proper coefficient, φ_e, reflecting the effect of initial eccentricity based on the Chinese design code; and (2) to determine a new confinement coefficient, k_cc = 1.10, for centrifugal concrete confined by GFRP tubes. Comparisons of the present design codes and specifications of confined concrete members with test results on 17 full-scale tube columns are also presented. Accordingly, new design equations, whose predictions generally agree well with the test results, are recommended to estimate the compressive capacity of the proposed HS-CFGT columns.

An experimental investigation on corroded composite push-out specimens was performed to investigate the behavior of stud shear connectors subjected to fatigue loading. A total of 14 standard push-out specimens were tested under static and fatigue loading. A static push-out test was performed to obtain the ultimate strengths for reference. The expected corrosion rate of test specimens ranged from 0 to 50%. The main purpose of these tests was to determine the fatigue life and the reduction effect of the fatigue life caused by the corrosion. The effect of corrosion on the fatigue crack, load-slip curves, and failure modes were also studied. The test results were also compared with current Eurocode design predictions, which are only for a specimen without corrosion. The suitability of the Eurocode design equation for fatigue life of corroded composite push-out specimens was evaluated.

In this study, the effect of corrosion on the static behavior of stud shear connectors was investigated. An innovative test setup for single stud shear connectors was designed and established. Two series of specimens having different stud diameters were fabricated and tested. The test specimens were firstly corroded to different corrosion rates by the electronic accelerating method. Static loading tests were then performed to obtain the load-slip curves and ultimate strengths of the corroded test specimens. The actual corrosion rates were measured from the studs obtained from the tested specimens. The test results were compared with the push out test specimens having similar corrosion rates. It is shown that the test results obtained from the single stud shear connectors are conservative compared with the corroded push test specimens, which prove the validation of the single stud shear connector test method. The effect of corrosion on the behavior of stud shear connectors was also presented.

The corrosion development of the reinforcement and shear stud connectors in the cracked steel–concrete composite beams under the salt-fog wet–dry cycles is presented in this investigation. Seven identical composite beams with load-induced concrete cracks were exposed to an aggressive chloride environment. The reinforcement and shear connectors were retrieved after specimens underwent a specified number of wet–dry cycles to obtain the corrosion pattern and the cross-section loss at different exposure times and their evolutions. The crack map, the corrosion pattern and the cross-section loss were measured and presented. Based on the experimental results, the influence of crack characteristics, including crack widths, orientations and positions on the corrosion rate and distribution, were accessed. Moreover, the effects of the connecting weldments on the corrosion initiations and patterns were analyzed. It was shown that the corrosion rate would increase with the number of wet–dry cycles. The characteristics of load-induced cracks could have different influences on the steel grids and shear stud connectors. The corrosion tended to initiate from the connecting weldments, due to the potential difference with the parent steel and the aggressive exposure environment, leading to a preferential weldment attack.