In this paper, a formulation based on the moment–curvature diagrams was proposed to calculate the effective flexural stiffness (EFS) of fiber-reinforced polymer (FRP) reinforced concrete (RC) beam members. A parametric study was carried out to encompass the effect of different factors, such as tensile reinforcement ratio, concrete compressive strength, modulus of elasticity, and aspect ratio. The proposed formulation was verified with numerous experimental data reported by various researchers. To extend the validation of the formulation into the beams of RC frames, the EFS (EI_e) of cracked GFRP (glass FRP) and CFRP (carbon FRP) RC beam sections for four types of frames were calculated. Based on the analytical study, experimental approach, and frame analysis approach, the EFS of FRP RC beams is less than 0.184 times the gross flexural stiffness (E_cI_g). According to the results obtained from various approaches, the range between 0.05 and 0.18 for the EFS ratio (EI_e/E_cI_g) of FRP RC beams is proposed.

The present research evaluates the technoeconomic performance of alkali-activated slag (AAS) concrete in comparison with ordinary portland cement (OPC) concrete. Seventy-five AAS mixtures with a wide range of mixture proportions are produced, moist-cured, and tested for their workability (slump or slump flow) and compressive strength. The relative ${\mathrm{CO}}_2$ emission and material cost of the mixtures are also analyzed in comparison with OPC concrete. Regression analyses are carried out to model the mixtures’ consistency and compressive strength and relate them to the governing factors [i.e., $(\mathrm{Na}+\mathrm{K})/\mathrm{Si}$ , $\mathrm{Ca}/\mathrm{Si}$ , and ${({\mathrm{H}}_2\mathrm{O}/\mathrm{Solids})}_{\mathrm{vol.}}$ ]. The extent of the effects and the interactions of such factors on the strength and slump of AAS concrete is quantitatively determined. A multiresponse optimization method with the aim of maximizing the strength for a targeted slump range while minimizing the relative cost and ${\mathrm{CO}}_2$ emission is introduced, and the mixture proportions yielding such conditions are identified. The results suggest that at molar ratios $(\mathrm{Na}+\mathrm{K})/\mathrm{Si}=0.55$ , $\mathrm{Ca}/\mathrm{Si}=1.01$ , and volume ratio ${({\mathrm{H}}_2\mathrm{O}/\mathrm{Solids})}_{\mathrm{vol.}}=1.0$ , workable AAS mixtures ($\mathrm{slump}=90\mathrm{mm}$ ) could be produced with strength values exceeding twice the amount and ${\mathrm{CO}}_2$ emissions half that of OPC concrete while maintaining the material cost increase below 40%.

The effect of non-persistent joints on sliding direction of rock slopes planar non-persistent discontinuity;rock bridge;effective joint coefficient;tensile and shear cracks; In this paper an approach was described for determination of direction of sliding block in rock slopes containing planar non-persistent open joints. For this study, several gypsum blocks containing planar non-persistent open joints with dimensions of $15{\times}15{\times}15cm$ were build. The rock bridges occupy 45, 90 and $135cm^2$ of total shear surface ($225cm^2$), and their configuration in shear plane were different. From each model, two similar blocks were prepared and were subjected to shearing under normal stresses of 3.33 and $7.77kg/cm^{-2}$. Based on the change in the configuration of rock-bridges, a factor called the Effective Joint Coefficient (EJC) was formulated, that is the ratio of the effective joint surface that is in front of the rock-bridge and the total shear surface. In general, the failure pattern is influenced by the EJC while shear strength is closely related to the failure pattern. It is observed that the propagation of wing tensile cracks or shear cracks depends on the EJC and the coalescence of wing cracks or shear cracks dominates the eventual failure pattern and determines the peak shear load of the rock specimens. So the EJC is a key factor to determine the sliding direction in rock slopes containing planar non-persistent open joints.