Refined Three-Dimensional Strut-and-Tie Model for Analysis and Design of Four-Pile Caps

[EN] Pile caps used in foundations are commonly designed for simple cases of loading and geometry using the strut-and-tie method. This approach is known to provide safe designs and rather conservative predictions of the ultimate failure load of tests. This level of conservatism is due mainly to the large simplifications made in the geometry assumed, which in many cases ignore relevant parameters such as the size of the column. A three-dimensional (3-D) strut-and-tie model is presented for four-pile caps in which the geometry adopted is optimized. The inclination of the direct strut from the column to the pile is obtained analytically through the maximization process of the resisting load carried by the truss assuming different modes of failure (flexural and shear). This approach is shown to provide more accurate predictions of the strength of existing deep pile cap tests with lower scatter compared to design approaches in the literature and the ACI 318 Code.The authors wish to thank the Spanish Ministry of Education for the FPU fellowship FPU12-01459 received by the first author and the funding provided for his research stay at the University of Surrey. The authors also wish to thank the Spanish Ministry of Economy and Competitiveness for funding Project BIA 2012-32300.Meléndez-Gimeno, C.; Sagaseta, J.; Miguel Sosa, P.; Pallarés Rubio, L. (2019). Refined Three-Dimensional Strut-and-Tie Model for Analysis and Design of Four-Pile Caps. ACI Structural Journal. 116(4):15-29. https://doi.org/10.14359/51714485S1529116

Overcoming Work-Up Limitations of Biphasic Biocatalytic Reaction Mixtures Through Liquid-Liquid Segmented Flow Processes

Adebar N, Choi J-E, Schober L, et al. Overcoming Work-Up Limitations of Biphasic Biocatalytic Reaction Mixtures Through Liquid-Liquid Segmented Flow Processes. ChemCatChem. 2019;11(23):5788-5793.Biphasic biocatalytic reactions have gained much attention in the field of enzyme-catalysed synthesis. As most components being of relevance for the pharmaceutical industry are hydrophobic, often biphasic reaction media turned out to be the solvent system of choice. However, in spite of successful reaction courses practical difficulties in the downstream-processing, in particular extremely difficult phase separations due to emulsification and precipitation, represent a challenge to overcome in process development. In this work, we report our studies on the benefits of a simple flow set-up being capable to minimise such work-up limitations. In detail, a segmented flow system based on a biphasic MTBE/buffer mixture was successfully applied for two types of enzymatic reductions of a hydrophobic ketone in the presence of an alcohol dehydrogenase (ADH) as an enzyme class being known for their excellent enantioselectivity and successful utilization in the synthesis of a range of active pharmaceutical ingredients. The applicability of this flow system was demonstrated with two different enzymes as well as different substrates. Besides an ADH from Lactobacillus brevis, an ADH from Ogatea minuta was utilized for the reduction of acetophenone and 2,2,2-trifluoroacetophenone, respectively

Continuous-Flow Dynamic Kinetic Resolution of Racemic Alcohols by Lipase-Oxovanadium Cocatalysis

Higashio K, Katsuragi S, Kundu D, et al. Continuous-Flow Dynamic Kinetic Resolution of Racemic Alcohols by Lipase-Oxovanadium Cocatalysis. European journal of organic chemistry. 2020;2020(13):1961-1967.A continuous-flow dynamic kinetic resolution of racemic secondary alcohols was carried out using a single column reactor packed with a mixture of immobilized lipase and an immobilized oxovanadium species, VMPS4. As a result, optically pure esters were produced in 88-92 % yields. Problems encountered in this study were overcome by using fillers that efficiently maintained the initial distribution of the catalysts in the reactor and by using a packing method in which the mixing ratio of the two catalysts was varied in a stepwise fashion. The flow process led to an increased turnover number of each catalyst compared to those of batch reactions

A computationally efficient method for hand–eye calibration

Purpose: Surgical robots with cooperative control and semiautonomous features have shown increasing clinical potential, particularly for repetitive tasks under imaging and vision guidance. Effective performance of an autonomous task requires accurate hand–eye calibration so that the transformation between the robot coordinate frame and the camera coordinates is well defined. In practice, due to changes in surgical instruments, online hand–eye calibration must be performed regularly. In order to ensure seamless execution of the surgical procedure without affecting the normal surgical workflow, it is important to derive fast and efficient hand–eye calibration methods. Methods: We present a computationally efficient iterative method for hand–eye calibration. In this method, dual quaternion is introduced to represent the rigid transformation, and a two-step iterative method is proposed to recover the real and dual parts of the dual quaternion simultaneously, and thus the estimation of rotation and translation of the transformation. Results: The proposed method was applied to determine the rigid transformation between the stereo laparoscope and the robot manipulator. Promising experimental and simulation results have shown significant convergence speed improvement to 3 iterations from larger than 30 with regard to standard optimization method, which illustrates the effectiveness and efficiency of the proposed method

Shear behavior of prestressed precast beams made of self-compacting fiber reinforced concrete

Even after many years of in-depth research the shear behavior of concrete structures is still a subject for debate. Current Design Codes need to be adapted to new materials and production methods. This paper discusses some still unresolved doubts, based on an experimental program consisting of nine prestressed l-beams of different flange dimensions. Shear evaluation is analyzed in accordance with the Codes under different conditions: a combination of fibers with stirrups, the possible influence of flange width on shear strength and the interaction of fibers with other important parameters such as flange width and longitudinal reinforcement. The results obtained show that fibers act as additional reinforcement to stirrups and also that the Codes are within the safety limits as regards shear ultimate limit state (ULS). (C) 2013 Elsevier Ltd. All rights reserved.The authors of this work wish to thank the Research Bureau of the Spanish Ministry of Science and Innovation and Plan-E, for funding of Project BIA 2009-12722. We are also grateful for the collaboration of the precast manufacturer PREVALESA S.L.Cuenca Asensio, E.; Serna Ros, P. (2013). Shear behavior of prestressed precast beams made of self-compacting fiber reinforced concrete. Construction and Building Materials. 45:145-156. https://doi.org/10.1016/j.conbuildmat.2013.03.096S1451564

Appraisal of MC2010 shear resistance approaches coupled with a residual flexural strength prediction model

In the present work the predictive performance of the two approaches proposed by Model Code 2010 for the evaluation of the shear capacity of fiber reinforced concrete (FRC) elements flexurally reinforced with conventional steel bars is assessed considering a database (DBs) constituted by 80 FRC beams do not including conventional transverse reinforcements. The accuracy of these shear models is evaluated by statistical analysis of the prediction ratio between the experimental and estimated shear capacity of the beams of the DBs, and applying the Demerit Points Classification approach for further information about the reliability of the two approaches in design context. Due to the absence of the post-cracking experimental characterization of the FRC used in several beams considered in the DBs, an approach was developed for estimating the residual flexural strength parameters from the most relevant known variables of steel fiber reinforcement mechanisms for concrete, namely the fiber volume and aspect ratio, and the concrete compressive and tensile strength. The residual flexural strength prediction model is assessed and its influence on the performance of the shear resistance models is evaluatedSFRH/BDE/96381/2013 co-funded by CiviTest - Pesquisa de Novos Materiais para a Engenharia Civil, Lda. and by FCT - Portuguese Foundation for Science and Technology. The authors also acknowledge the support provided by the FCT project PTDC/ECM-EST/2635/201

Root, Bulb, and Acorn : Sowing seeds of care, connection, and community

Quercus garryana, or Garry oak, is western Canada’s only native oak tree. It grows within a complex web of associated ecosystems, including the Garry oak meadow. The ecological legacy of thousands of years of Indigenous landscape management, less than 5% of Garry oak ecosystems are still standing. However, due to climate change, their suitable range is forecasted to increase. While many Pacific Northwest tree species are expected to struggle under shifting heat and drought regimes, Garry oak is well-adapted to flourish. Root, Bulb, and Acorn aims to increase the diversity and resilience of Vancouver’s urban forest by creating plots of Garry oak meadows within three parks in Vancouver: Tatlow Park, Oak Meadows Park, and Queen Elizabeth Park. The acts of planting, tending and maintaining these plots will foster the well-being of the meadows, as well as a renewed appreciation for Garry oak. Performing small-scale interventions with largescale impacts, this project aims to plant seeds of care, connection, and community to grow alongside the ecology of this unique and vital ecosystem.Applied Science, Faculty ofArchitecture and Landscape Architecture (SALA), School ofUnreviewedGraduat

Towards Automation of Continuous Chemoenzymatic Syntheses of Plasticizers, Nitriles, and Chiral Esters from Renewable Resources

Adebar N. Towards Automation of Continuous Chemoenzymatic Syntheses of Plasticizers, Nitriles, and Chiral Esters from Renewable Resources. Bielefeld: Universität Bielefeld; 2022