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Analytical models which can reliably predict the load–deformation behaviors and the ultimate strength of columns are indispensable tools for the practical design. In this paper, an analytical model is developed to predict the compressive load–deformation behavior and the ultimate capacity of engineered cementitious composite confined concrete encased steel (ECC‐CES) composite columns. The proposed analytical model employs the effective material stress and strain compatibility approaches for the predictions of compressive load–deformation response of ECC‐CES columns. The material constitutive models for ECC, concrete, and steel are first established, and then used in the analytical model. The effect of ECC and steel confinement on the concrete core and the softening behavior of steel column due to compression buckling are also considered. Based on the experimental results, appropriate strength reduction factors are proposed so that the effective material stresses can be calculated. The strength predictions from the proposed analytical methods and different design codes are compared with the experimental and numerical results. It was found that the proposed analytical models using effective material stresses gave better predictions than many commonly used design codes. [ABSTRACT FROM AUTHOR]

Accurate estimation of the in situ strength of concrete at early age is very important as it provides the necessary information required to start subsequent construction operations. Overestimation of the strength may cause serious safety hazards and underestimation may lead to unnecessary costly delays. This study investigates the performance of the maturity method in estimating the strength of in situ concrete subjected to cold weather at early age. Instrumented concrete slabs were subjected to cold weather conditions at early ages and their strengths were measured using drilled core samples from the slab. Sensors embedded in the slabs measured the temperature in the concrete which was used to estimate the strength using the maturity method. The measured core strengths at 24 and 72 h after casting are then compared with the estimated strengths using the maturity method and its performance is evaluated. The core strengths are also compared with the strength of standard cylinders cured at the same condition as the slabs. More than 250 cylinders from two slab thicknesses and four batches of concrete were used in the experiments to obtain statistically significant experimental data. The results show that the maturity method performed much better than the standard cylinder strength. On average the standard cylinder strength underestimated the core strength by more than 40% while the maturity method overestimated the strength by less than 10% with a lower variation. [ABSTRACT FROM AUTHOR]

Due to its high compressive strain of at least 0.5%, which is higher than both the yield strain (0.35%) of high strength steel (HSS) and the compressive strain (0.23%) of normal strength concrete (NSC), Engineered Cementitious Composites (ECC) is a material with high potential to replace NSC in HSS composite beam construction. This study reports an experimental investigation on the flexural behaviour of HSS‐ECC composite beam fabricated by using HSS I‐section in conjunction with hybrid polyethylene‐steel fibers (PE‐ST) ECC slab. Shear connection between the HSS I‐section and the top PE‐ST ECC slab was constructed by using normal profiled steel sheeting and headed shear studs. A HSS‐ECC composite beam and a HSS‐NSC composite beam were cast and tested under four‐point bending. The test results revealed that a large area of HSS I‐section in HSS‐ECC composite beam yielded compared to only a small yielded area of which in the HSS‐NSC counterpart despite the fact that both composite beams have identical configuration and silimar mechanical properties. The HSS‐NSC beam underwent longitudinal shear failure while in contrast, the HSS‐ECC beam failed by flexure and exhibited great ductility. [ABSTRACT FROM AUTHOR]