A new test method for investigating punching shear strength in Ultra High Performance Fibre Reinforced Concrete (UHPFRC) slabs

Punching shear capacity of Ultra High Performance Fibre Reinforced Concrete (UHPFRC) slabs has been the subject of a number of studies. There is, however, only limited information available on this parameter of UHPFRC without conventional reinforcement. This is due to the complexity of punching shear behaviour within concrete and is also limited by the lack of suitable test methods currently available. Therefore, in this study, attempts to design a novel testing method to measure the punching shear capacity of the concrete was carried out. The designed test arrangement was employed to carry out an extensive experimental study on UHPFRC slabs subjected to punching shear failure. From the results obtained, the relationship between the punching shear load and the angle of the shear plane, the critical value of the basic control perimeter and failure mode were studied. The experimental study undertaken here provides significant insight into the punching shear capacity of UHPFRC slabs. The results illustrate and highlight many of the advantages of using UHPFRC compared to normal concrete in structural designs. The novel punching shear test presented here has established itself as a suitable procedure for testing UHPFRC and potentially, other fibre reinforced composites

Metamodel techniques to estimate the compressive strength of UHPFRC using various mix proportions and a high range of curing temperatures

In order to predict the compressive strength (σc) of Ultra-high performance fiber reinforced concrete (UHPFRC), developing a reliable and precise technique based on all main concrete components is a cost-effective and time-consuming process. To predict the UHPFRC compressive strength, four different soft computing techniques were developed, including the nonlinear- relationship (NLR), pure quadratic, M5P-tree (M5P), and artificial neural network (ANN) models. Thus, 274 data were collected from previous studies and analyzed to evaluate the effect of 11 variables that impact the compressive strength, including curing temperature. The performance of the predicted models was evaluated using several statistical assessment tools. According to the findings, ANN results performed more suitable than other models with the lowest root mean square error (RMSE) and highest coefficient of determination (R2) value. According to the sensitivity analysis, the most variables that affect the compressive strength prediction of UHPFRC are a curing temperature with a percentage of 17.36%, the fiber content of 17.13%, and curing time of 15.13%

Saharan exploitation of plants 8,000 years BP

Sorghum and millets are among the world's most important food crops and, for the inhabitants of the semi-arid tropics, they are the main sources of protein and energy. Little is known about the history of these crops; their domestication is thought to have occurred in the African savannah, but the date and precise location are unknown1,2. Excavations at an early Holocene archaeological site in southernmost Egypt, 100 km west of Abu Simbel, have yielded hundreds of carbonized seeds of sorghum and millets, with consistent radiocarbon dates of 8,000 years before present (BP), thus providing the earliest evidence for the use of these plants. They are morphologically wild, but the lipid fraction of the sorghum grains shows a closer relationship to domesticated than to wild varieties. Whatever their domestic status, the use of these plants 8,000 years ago suggests that the African plant-food complex developed independently of the Levantine wheat and barley complex