Composite action in connection regions of concrete-filled steel tube columns

Mathias Johansson 국제구조공학회 2003 Steel and Composite Structures, An International J Vol.3 No.1

In a nonlinear finite element study on the mechanical behavior of simple beam connections to continuous concrete-filled steel tube columns, two principally different connection types were analyzed: one with plates attached to the outside of the tube wall, relying on shear transfer, and one with an extended plate inserted through the steel section to ensure bearing on the concrete core. The load was applied partly at the connection within the column length and partly at the top, representing the load from upper stories of a multistory building. The primary focus was on the increased demand for load transfer to ensure composite action when concrete with higher compressive strength is used. The results obtained from the analyses showed that the design bond strength derived from push tests is very conservative, mainly due to the high frictional shear resistance offered by pinching and contraction effects caused by connection rotation. However, with higher concrete strength the demand for load transfer increases, and is hard to fulfill for higher loads when connections are attached only to the steel section. Instead, the connection should penetrate into the concrete core to distribute load to the concrete by direct bearing.

Has Consumption Risk Sharing Increased in Asia (and Elsewhere)?

Mathias Hoffmann 서울대학교 경제연구소 2011 Seoul journal of economics Vol.24 No.4

What impact has financial globalization had on risk sharing? In theory, financial globalization should improve international consumption risk sharing. While the answer to this question is of utmost policymaking concern, results in the empirical literature are inconclusive. The paper surveys the extant literature and tries to identify which factors influence the answer: i) consumption risk sharing seems to have increased among industrialized countries but much less in the emerging world. ii) The increase in risk sharing is generally found to be stronger in studies that focus on the trends rather than purely cyclical variation in the data. iii) globalization has not only affected consumption responses to output shocks but also the structure of these shocks themselves. This, in turn, has affected the measurement of risk sharing. The paper examines the relevance of these points on a sample of East Asian Economies. My results indicate that risk sharing in East Asia has started to increase once the region had recovered from the Asian crisis.

Composite Behaviour of Textile Reinforced Reactive Powder Concrete Sandwich Façade Elements

Mathias Flansbjer,Natalie Williams Portal,Daniel Vennetti,Urs Mueller 한국콘크리트학회 2018 International Journal of Concrete Structures and M Vol.12 No.7

Within the EC funded project smart elements for sustainable building envelopes, carbon textile reinforcement was incorporated into reactive powder concrete, namely textile reinforced reactive powder concrete (TRRPC), to additionally improve the post-cracking behaviour of the cementitious matrix. This high-performance composite material was included as outer and inner façade panels in prefabricated and non-load bearing sandwich elements along with low density foamed concrete (FC) and glass fibre reinforced polymer continuous connecting devices. Experiments and finite element analysis (FEA) were applied to characterize the structural performance of the developed sandwich elements. The mechanical behaviour of the individual materials, components and large-scale elements were quantified. Four-point bending tests were performed on large-scale TRRPC-FC sandwich element beams to quantify the flexural capacity, level of composite action, resulting deformation, crack propagation and failure mechanisms. Optical measurements based on digital image correlation were taken simultaneously to enable a detailed analysis of the underlying composite action. The structural behaviour of the developed elements was found to be highly dependent on the stiffness and strength of the connectors to ensure composite action between the two TRRPC panels. As for the FEA, the applied modelling approach was found to accurately describe the stiffness of the sandwich elements at lower load levels, while describing the stiffness in a conservative manner after the occurrence of connector failure mechanisms.

Tribological conditions using CO2 as volatile lubricant in dry metal forming

Mathias Liewald,Günter E. M. Tovar,Christoph Woerz,Georg Umlauf 한국정밀공학회 2020 International Journal of Precision Engineering and Vol.7 No.5

Deep drawing is the most important manufacturing process in order to produce sheet metal parts in mass production. In this study, volatile carbon dioxide (CO 2) is used as lubricant in order to replace mineral oil-based lubricants. CO 2 is injected into the void between the forming tool and the metal part through laser drilled microholes in the forming tool and acts there as a highly efficient lubricant. In order to investigate the tribological conditions during the drawing process, a new test bench having optical access to the CO 2 lubricant is designed, built and used in this study. Additionally, the CO 2 fl ow through the microholes is modeled using CFD simulation. Both the experimental and the theoretical study reveal a critical influence of the geometry of the microholes on the phase of the CO 2 in the forming tool and on the friction during the drawing process. Thereby, these investigations confirm that the CO 2 is in solid and/or gaseous state dependent on the surface pressure and the geometry of the microholes. Consequently, these results support the concept of microstructure-designed forming tools allowing dry metal forming for locally adjusted and environmentally friendly friction conditions.

Interplay of Structural Distortions, Dielectric Effects and Magnetic Order in Multiferroic GdMnO3

Mathias Doerr,Michael Loewenhaupt,Aditya A. Wagh,P. S. Anil Kumar,Suja Elizabeth,Sahana Roessler,Martin Rotter,Steffen Wirth 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.62 No.10

Multiferroic materials are characterized by simultaneous magnetic and ferroelectric ordering making them good candidates for magneto-electrical applications. We conducted thermal expansion and magnetostriction measurements in magnetic fields up to 14 T on perovskitic GdMnO3 by highresolution capacitive dilatometry in an effort to determine all longitudinal and transversal components of the magnetostriction tensor. Below the ordering temperature TN = 42 K, i.e., within the different complex (incommensurate or complex) antiferromagnetic phases, lattice distortions of up to 100 ppm have been found. Although no change of the lattice symmetry occurs, the measurements reveal strong magneto-structural phenomena, especially in the incommensurate sinusoidal antiferromagnetic phase. A strong anisotropy of the magnetoelastic properties was found, in good agreement with the type and propagation vector of the magnetic structure. We demonstrate that our capacitive dilatometry can detect lattice expansion effects and changes of the dielectric permittivity simultaneously because the sample is housed inside the capacitor. A separation of both effects is possible by shielding the sample. Dielectric transitions could be detected by this method and compared to the critical values of H and T in the magnetic phase diagram. Dielectric changes measured at 1 kHz excitation frequency are detected in GdMnO3 at about 180 K,and between 10 K and 25 K in the canted antiferromagnetic structure which is characterized by a complex magnetic order on both the Gd- and Mn-sites.

The efficiency of passive confinement in CFT columns

Mathias Johansson 국제구조공학회 2002 Steel and Composite Structures, An International J Vol.2 No.5

The paper describes the mechanical behavior of short concrete-filled steel tube (CFT) columns with circular section. The efficiency of the steel tube in confining the concrete core depending on concrete strength and the steel tube thickness was examined. Fifteen columns were tested to failure under concentric axial loading. Furthermore, a mechanical model based on the interaction between the concrete core and the steel tube was developed. The model employs a volumetric strain history for the concrete, characterized by the level of applied confining stress. The situation of passive confinement is accounted for by an incremental procedure, which continuously updates the confining stress. The post-yield behavior of the columns is greatly influenced by the confinement level and is related to the efficiency of the steel tube in confining the concrete core. It is possible to classify the post-yield behavior into three categories: strain softening, perfectly plastic and strain hardening behavior. The softening behavior, which is due to a shear plane failure in the concrete core, was found for some of the CFT columns with high-strength concrete. Nevertheless, with a CFT column, it is possible to use high-strength concrete to obtain higher load resistance and still achieve a good ductile behavior.

Progressive Multifocal Leukoencephalopathy after Ibrutinib Therapy for Chronic Lymphocytic Leukemia

Mathias Lutz,Arik B. Schulze,Elisabeth Rebber,Stefanie Wiebe,Tarek Zoubi,Oliver M. Grauer,Torsten Keßler,Andrea Kerkhoff,Georg Lenz,Wolfgang E. Berdel 대한암학회 2017 Cancer Research and Treatment Vol.49 No.2

Progressive multifocal leukoencephalopathy (PML) is a devastating neurological disease observed nearly exclusively in immunocompromised patients. Recently, the introduction of monoclonal antibodies significantly inhibiting the immune system such as rituximab has led to an increase in PML cases. Although rituximab-based immunochemotherapy remains the standard of treatment for chronic lymphocytic leukemia (CLL), the importance of Bruton’s tyrosine kinase inhibitors such as ibrutinib is steadily increasing. However, long-term experiences regarding possible side effects of these new substances are rare. Here, we report the development of eventually fatal PML possibly associated with ibrutinib therapy for CLL after multiple prior treatment lines, including rituximab. To the best of our knowledge, this is the first study to report such findings. Since the last course of rituximab was applied over 3 years ago, it is conceivable that the strong B cell inhibition by ibrutinib led to PML. With increased awareness of this potential side effect, further clinical studies are certainly warranted to evaluate this possible association.

Iterative approach for anchor configuration of positioning systems

Mathias Pelka,Grigori Goronzy,Horst Hellbr¨uck 한국통신학회 2016 ICT Express Vol.2 No.1

With anchor positions and measurements of distances between an object and anchors, positioning algorithms calculate the position of an object, e.g. via lateration. Positioning systems require calibration and configuration prior to operation. In the past, approaches employed reference nodes with GPS or other reference location systems to determine anchor positions. In this article, we propose an approach to determine anchor positions without prior knowledge. We evaluate our approach with simulations and real data based on the Decawave DW1000 radio and show that the error is proportional to the mean error of the distance estimation.

Towards Automated 3D reconstruction in SME factories and Digital Twin Model generation

Mathias Minos-Stensrud,Ole Henrik Haakstad,Olav Sakseid,Baard Westby,Alex Alcocer 제어로봇시스템학회 2018 제어로봇시스템학회 국제학술대회 논문집 Vol.2018 No.10

This paper presents preliminary results towards the development of digital twin models for Small to Medium Enterprise (SME) factories in a partially automated and cost-effective manner. In many cases it is desirable to obtain a 3D model of a factory floor and machinery, that can be used for visualization of Digital Twin models. Current commercial 3D reconstruction solutions involve the use of high-end LiDAR sensors which increase the cost of the 3D scanning process and suppose a barrier for SME factories on their path towards Industry 4.0. The paper presents a comparison of 3D reconstruction results using low-cost sensors including a Zenfone AR mobile phone, an Intel RealSense ZR300 and a Kinect v2. The small size and weight of the sensors make it possible to be mounted on small unmanned aerial vehicles and enable future 3D reconstruction in an autonomous manner. The data was processed using an open source Simultaneous Localization and Mapping (SLAM) library RTAB-Map. The results were compared with a professional 3D scan using a GeoSLAM LiDAR. Experimental results from a scanning of a university research lab with a small simulated production line and two UR3 industrial manipulators is presented. The obtained 3D model was used to generate a simple Digital Twin model that can be visualized using a VR headset.

Improving the Precision of Specifications by Evaluating the Influence of Test Parameters on Tribological Results

Mathias Woydt,Hartwig Weber 한국트라이볼로지학회 2003 한국트라이볼로지학회 학술대회 Vol.37 No.-

A series of cooperative interlaboratory tests (round robins) was conducted in 1997, 1998, 1999, 2000, 2001, 2002 and 2003 by the DIN 51834 Working Group on Tribological Tests in Translatory Oscillation Apparatus. The statistical analysis of these test results shows the influence of cleaning solvent, machine model and evaluation criteria on the tribological properties of the lubricants tested. Coefficients of friction and wear results are ranked according to the effects of ten different cleaning solvents, where isopropanol gave the lowest values and isoparaffin solvents the highest. The effect of machine model on coefficients of friction varied from about 0.2 % to 0.9 % of the mean. Wear results were not affected. The tests also showed that the seizure criteria and methods of measuring wear required for in the test procedure do not provide a suitable measure of the tribological properties of some lubricants. The precision was improved by introducing a grease apply caliper as well as an increased stroke to 1,5 mm and running-in. The temperature does not affect the precision of the oil test procedure.