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Self-centering rocking walls offer the possibility of minimizing repair costs and downtimes, and also nullify the residual drift after seismic events, thanks to their self-centering properties. In this paper, the effect of axial stress ratio on the behavior of monolithic self-centering rocking walls is investigated by utilizing a developed finite element model. To verify the validity of the finite element model, results and observed damage in the model are compared with those of a full-scale wall test. The axial stress ratio is varied from 0.024 to 0.30 while keeping the other structural parameters constant. For qualitative damage evaluation, the observed damage in the model compared with expected damage states of desired performance levels. In order to evaluate the incurred damage quantitatively, the amount of crushing and damage in the wall is calculated by utilizing several ratios (crushing ratio and damage ratio). Furthermore, seismic response factors (i.e., μ, R and C) are calculated for different axial stress ratio values. The obtained results showed that, in order to satisfy the requirements of desired performance levels, the maximum axial stress ratio should be approximately within the range of 0.10-0.15. In addition, the maximum overall damage ratio and crushing ratio are suggested to be less than 5%. For axial stress ratio higher than 0.15, the flag-shaped pattern of hysteresis curves completely disappeared and the variation of displacement ductility is less sensitive to axial stress ratio. Considering the maximum axial stress ratio limited to 0.150, values of 4 and 3.5 are conservatively proposed as a period-independent response modification factor and displacement modification factor of the investigated structural wall, respectively. [ABSTRACT FROM AUTHOR]

To investigate the serviceability performance of High-Strength Concrete (HSC) beams, 12 beams (L=2 m, b=0.2 m, h=0.3 m and shear span to depth ratio of 1.8) with different ratios of ρ and ρ′ (percentage of tensile and compressive steel) were cast and tested under bending. During the test, concrete and steel strains, deflections, and crack widths were measured at different locations along each beam. Based on the experimental readings and observations, the cracked moment of inertia (Icr) of HSC beams was determined and the results were compared with some selective theoretical methods. Also, the flexural crack width of the beams was measured and the applicability of ACI, BS, and CSA code for normal strength concrete (NSC) was verified for HSC beams tested. The experimental (Icr)exp values of HSC beams were lower than the theoretical (Icr)th values from different codes. It was concluded that, the serviceability and post serviceability performance of reinforced concrete structures can be improved using high strength concrete. In general, for almost all HSC tested beams at three crack width (0.1, 0.2, 0.3 mm); the use of AC! equation led to predict 50% of the crack width conservatively (the ratio of ((ωcr)th/(ωcr)exp) is greater than unity) but the results of the BS equation are conservative while compare to the ACI equation. The use of the CSA equation for the beams of higher and lower reinforcement ratio, caused a more conservative, and a closer value respectively, to limiting values of CSA. The deflection at initial steel horizontal yield plateau, is less than 9 mm, which is a sign of excellent deflection performance of HSC beams. [ABSTRACT FROM AUTHOR]

The growing concern about global climate change and its adverse impacts on societies is putting severe pressure on the construction industry as one of the largest producers of greenhouse gases. Given the environmental issues associated with cement production, Geopolymer Concrete (GPC) has emerged as a sustainable construction material. This research experimentally studied the effect of partially substituting ground granulated blast-furnace slag (GGBS) with silica fume (SF) and natural zeolite (NZ) (by 0–30% with 5% increments) in the GPC activated by sodium hydroxide (NaOH) solution with different concentrations (4, 6 and 8 M) and sodium silicate (water glass) solution on the compressive strength. Obtained results revealed that increasing the NaOH concentration reduced the concrete strength, while adding SF and NZ to the concrete yielded an improvement in the compressive strength. Moreover, this study proposed an Artificial Neural Network (ANN) to predict the compressive strength of pozzolanic GPC based on GGBS (i.e., at the ages of 7, 28, and 90 days). The compressive strength of GGBS-based GPC (i.e., 117 concrete specimens manufactured out of 39 various mixtures) obtained by experimental tests was used to develop the model. The specimen age, NaOH concentration, contents of NZ, SF, and GGBS were considered as inputs variables for developing the ANN model. The predicted results establish the accuracy and high prediction ability of the proposed model. The findings of this study can bring significant benefits for the range of organizations involved. Image 1 • Application of SF and NZ increased the compressive strength of geopolymer concrete. • SF had a considerable effect on the slump reduction of fresh concrete. • NZ had a considerable effect on the compressive strength in long term. • SF had a considerable influence on the compressive strength of concrete. • Proper correlation exists between experimental values and those generated by ANN. [ABSTRACT FROM AUTHOR]