A Numerical Comparison between Spiral Transverse RC and CFST Columns under Loads of Varying Eccentricities

This paper is the first to present the results of a numerical comparison between the performances of two newly developed concrete columns namely: multi-tied spiral transverse reinforced (MTSTR) column and concrete-filled steel tube (CFST) column under eccentric compressive loads. The behavior of MTSTR columns under eccentric loads has not been studied until today and also this behavior is not compared to that of the CFST columns. The numerical models of these columns were constructed using the nonlinear finite element method and validated against the previously published experimental data in the literature. Concrete damage plasticity model and elastic-perfect plastic model were used to simulate the behavior of concrete core and steel of the columns, respectively. This provides the capability of modeling of the nonlinear large deformations of the columns. The obtained results show that the MTSTR columns can provide greater load carrying capacity, ductility, and energy absorption with slightly lower initial stiffness than the CFST columns under the same eccentricities. For instance, the load-carrying capacity of MTSTR column is 18 percent greater than that of the CFST column when the load eccentricity is 100 mm. In case of 100 mm eccentricity, the ductility of the improved version of the MTSTR column proposed in this study is 30 percent greater than CFST one

Structural Lightweight Concrete Containing Basalt Stone Powder

In spite of the demonstrated efficacy of basalt stone powder as a cost-effective and readily available additive in enhancing the mechanical properties and durability of ordinary-weight concrete, its application in Structural Lightweight Concrete (SLWC) remains unexplored. This study introduced a mixing design for SLWC incorporating Light Expanded Clay Aggregates (LECAs) and basalt stone powder with a subsequent evaluation of its strength and durability characteristics. The experimental procedure involved creating various samples, considering differing proportions of cement, water, basalt stone powder, sand, LECA, superplasticizer, and aerating agent. The compressive strength and density of the 28-day-cured concrete specimens were determined. An optimal SLWC with a compressive strength of 42 MPa and a density of 1715 kg/m3 was identified. The flexural and tensile strength of the optimal SLWC exceeded those of ordinary-weight concrete by 6% and 3%, respectively. Further evaluation revealed that the optimal SLWC exhibited 1.46% water absorption and an electrical resistivity of 139.8 Ohm.m. Notably, the high porosity of LECA contributed to the low durability of SLWC. To address this, cost-effective external coatings of emulsion and fiberglass were applied to enhance the durability of the SLWC. Four coating scenarios, including one-layer bitumen, two-layer bitumen, three-layer bitumen, and three-layer bitumen with fiberglass, were investigated. The measurements of electrical resistance and compressive strength revealed that the use of three layers of emulsion bitumen and fiberglass improved the durability of the concrete by over 90% when the SLWC was exposed to severe chloride attack. Consequently, the durability of the SLWC with an external coating surpassed that of ordinary-weight concrete