The response of reinforced concrete (RC) shear wall as a lateral resisting member has been studied extensively, but it still demands a general practical model that identifies the envelope within which load-drift paths occur during cyclic loading. Such a broad model is vital to ensure adequate lateral strength to resist reversal loadings imposed on these walls during earthquake events and ductility to measure inelastic deformation capabilities. A new model to define the backbone curve is developed in this paper for squat, intermediate, and slender flanged and nonflanged RC walls. The most common failure modes observed in the field and laboratory experiments are investigated and incorporated in the proposed model to estimate the response of these walls from elastic range until ultimate failure. The main parameters controlling the estimation of drifts that features the backbone curve thresholds are presented in this paper. The results of proposed model are compared with the outcomes of 117 specimens experimentally tested by other researchers. Also, the results are compared with Federal Emergency Management Agency (FEMA) 356, the updated American Society of Civil Engineers (ASCE)/Structural Engineering Institute (SEI) 41, and Eurocode (EC8 and EC2) provisions which reveal that only one general model, proposed in this paper, can capture the response of RC structural walls with an aspect ratio ranging from 0.35 to 2.5 and an axial load ratio from 0 to 0.4 with good agreement with experimental outcomes. K E Y W O R D S cyclic loadings, flexural failure, nonlinear dynamic modeling, shear failure, sliding shear, web crushing

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Rapid impact compaction (RIC) has been used effectively as a ground improvement at medium depth technique for granular soils. RIC is normally used to increase bearing capacity, reduce potential settlements and mitigate liquefaction. This paper presents a calibrated three-dimensional cap-plasticity finite-element model (FEM) to simulate ground improvement using RIC. The results of 107 RIC field compaction points were used to calibrate and validate the FEM. Numerical outcomes of the FEM showed good agreement with the field compaction results. The FEM was further used to propose a relationship between the soil bearing capacity and the number of hammer blows for engineering practice. This is attained by performing pushover analysis of a spread footing resting on RIC improved soils with different numbers of RIC blows. The RIC, circular 1·5 m anvil was used as the spread footing. The applied stresses that produced 25 mm settlement are considered the improved soil bearing capacity. Also, the paper presents a recommendation for the optimum number of blows after which more blows will have no significance.

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Recycled aggregates are one of the options that can be used to form the concrete because they can be considered as environmental-friendly. Using of high replacement ratio of recycled aggregates decreases the compressive strength of the concrete and weakens the rest mechanical properties. This study intended to investigate the effect of the confinement on Reinforced concrete (RC) columns that are made with recycled aggregates since it raises the compressive strength of concrete and improves the behavior of RC columns. This study is analytical and conducted based on the available data in literature of 34 columns that were tested experimentally under axial load only by other researchers, containing various ratios of recycled aggregates. The collected data of axial load capacity are compared with ACI318-19 provisions. It can be used to estimate axial load capacity. Confinement factors are calculated and compared with Mander's formula. It is concluded that Mander's equation can be used after being multiplied by the modification factors derived in this study to better reflect the confinement state. Also, a new formula is derived to estimate the unconfined compressive strength of the concrete based on the used replacement ratio of recycled aggregates.

PurposeConcrete-filled double-skin tubular (CFDST) columns have been gaining significant attention since these columns proved to be more efficient compared to concrete-filled steel-tubular (CFST) columns. This paper presents a tool to design slender CFDST columns with/without inclination.Design/methodology/approachFirst, 3D nonlinear finite element (FE) models of twenty-two straight CFDST columns are calibrated and it is found that FE results are in good agreement with the experimental outcomes. This is validated based on available experimental data. Subsequently, a parametric study is conducted by adjusting each calibrated FE model to account for three different angles of inclination. These models are used to quantify the effective length factor of these inclined columns.FindingsIt is found that FE results are in good agreement with the experimental outcomes. An equation is developed in this paper to calculate the characteristic concrete compressive strength for the design of straight CFDST columns. In addition, an equation is presented for engineering practice to calculate the effective length factor at different inclination angles and slenderness ratios to design CFDST columns. The predicted load capacity compares well with the experimental results of straight columns and FE results of inclined columns.Originality/valueAdvancement in the structural design procedure is required as a response to the continuous innovations in architectural design. Designers might introduce an inclination in columns in buildings or bridges, and there are no available guidelines to design them.

Composite concrete–steel sections are widely used in flooring and decking systems in buildings and bridges. Concrete decks form cracks at negative moment regions and remain uncracked at the positive ones. Finite-element (FE) analyses of beams composed of concrete–steel sections must take the change in the composite section properties into consideration on the basis of the level of cracks in the concrete deck. Commercial FE software packages use linear elastic analysis for calculating the moment and shear force distributions in beams loaded with gravitational loads, with no consideration of the level of cracking in the concrete slab at the negative moment regions. A FE modelling technique for beams with concrete–steel sections was developed by using FE software packages to estimate the internal loadings necessary for the design process. The results from the proposed FE technique were compared with experimental data on continuous and simply supported beams reported by other researchers. It was found that consideration of the concrete deck longitudinal reinforcement in the modelling of a composite section over negative moment regions is necessary for identifying flexural properties, resulting in better accuracy of the structural analysis outcomes. The proposed modelling technique estimated deflection in the tested beams with only 7% error with respect to the experimentally measured deflection.