Structural behavior of digitally fabricated thin-walled timber columns

This paper aims to investigate the structural behavior of digitally fabricated thin-walled timber sections with edge connectivity provided by integral mechanical press-fit joints. Experimental, numerical, and analytical investigations have been developed to accurately characterize the press-fit section behavior and their failure modes. Plywood fiber orientation, material thickness, and connection tightness are considered as potential factors that may affect the performance of the press-fit jointing system. Experimental testing of square hollow sections (SHSs) under uniaxial compressive loading showed failure of sections through both conventional crushing and novel pop-off bifurcation failures. Pop-off buckling behaviors were shown to be governed by the integral joint transverse stiffness and its magnitude relative to a critical edge stiffness value. Columns with joint transverse stiffness value less than the critical edge stiffness value exhibited pop-off failures. These joint stiffness values were obtained from testing of unloaded joints and were used to obtain accurate predictions of column failure modes. Joint stiffness values for loaded joints were then predicted with an interpolation model mapping axial strain to a tighter connection tolerance and these were used to obtain accurate estimations for column failure load in most of the tested column types. Comparative investigations showed thin-walled sections with integral joints only to be capable of matching the compressive capacities of glued sections, for instances where crushing governed. Similarly, the weight-specific compressive capacity of timber sections was found to be comparable to thin-walled steel sections when crushing governs

The Impact of Covid-19 on Parents of Children with Disability: Educational Needs and Challenges

During the Corona pandemic, parents of children with disabilities experienced unprecedented situations. The aim of this study was to identify the educational needs and challenges which prevented parents from providing adequate support to their children during the outbreak. An online survey was launched on June 4, 2020, to gather information from 638 parents of children with disabilities. The findings revealed that 60% of parents need assistance in implementing Individual Education Program activities. Similarly, 71.7% of parents reported that the centers had only spent less than one-hour on-line per day educating the children. Significant challenges emerge as a result of parents’ inability to cope with the load and their loss of hope in helping children, which varies depending on the severity of the condition, with severe disabilities posing the greatest challenge. According to the study, special education centers should follow defined protocols that focus on parents' educational needs, as well as establish proactive approaches for providing support to parents of children who require special care

Ultra-high-performance concrete with Iron ore tailings and non-metallic and hybrid fibers-A comprehensive experimental study

This research discusses the behavior of ultra-high-performance concrete (UHPC) specimens made with dumped waste iron ore tailing (IOT) as a fine aggregate in the mix by 30% and 40% in volume fraction along with mono and hybrid fiber incorporation. Basalt fibers of 1%, 2%, and 3%, polypropylene fibers of 0.18%, 0.20%, and 0.22%, and glass fibers of 1%, 1.5%, and 2% of volume fractions were the non-metallic fibers used. Steel fibers as a metallic factor were kept 1% constant throughout the study. The water-to-binder ratio was maintained between 0.15 and 0.17 after sufficient trials. A high-range water reducer was utilized to improve the flowability of the mix. The experimental investigations confirmed that the SG2 mix with 1% steel and 1.5% glass fiber, and 30% IOT, exhibited improved tensile and impact strength compared to standard conventional concrete. This combination exposed an impact energy of 4.05 × 105 kJ for the first crack and 2.7 × 106 kJ for collapse. The energy taken by the specimen between the first crack and the collapse was about 2.3 × 106 kJ. The microstructure was analyzed using Scanning Electron Microscopy. The non–metallic fibers with dominant mechanical properties were thermogravimetrically analyzed

Utilization of waste marble powder as partial replacement of cement in engineered cementitious composite

AbstractThe current study focuses on the utilization of Marble Waste Powder (MWP) as a partial substitution of cement along with local sand instead of microsilica sand in Engineered Cementitious Composite (ECC). The aim was to reduce the environmental concerns of ECC by reducing the cement content without adversely affecting the desired properties. Four mixes were evaluated; the control mix which has no MWP and three test mixes having cement replacement with MWP by 10%, 15%, and 20% were used, respectively. The properties of ECC mixes were found in terms of compressive, tensile, and flexural characteristics. The trend of change in the basic properties of ECC with an increased percentage of MWP as partial substitution of cement was found along with the hypothesis test on the experimental data. From this study, it was concluded that the increased percentage of MWP reduces on the compressive strength of ECC. The maximum reduction in compressive strength of ECC was recorded as 49% with 20% replacement of cement with MWP, as compared to the control sample at 91 days of test age. The tensile strain of ECC increases with the increase in MWP content, while the tensile stress increases only with the increase of MWP content up to a specified limit. The ultimate load in the force–deflection curve first increases with the increase in MWP content up to a certain percentage, while upon further increase in MWP content from 15% to 20%, the ultimate load decreases. The study suggests that the properties do not vary significantly for the modified ECC samples containing MWP, especially the 10% and 15% MWP samples, and can be utilized instead of normal ECC, thus mitigating environmental concerns without compromising the ECC’s performance