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Integration of Peridynamic Theory and OpenSees for Solving Problems in Civil Engineering
Get PDFPeridynamics (PD) is a powerful method to simulate the discontinuous problems in civil engineering. However, it may take a lot of effort to implement the material constitutive models into PD program for solving a broad range of problems. OpenSees is an open source software which includes a versatile material library and has been widely used by researchers and engineers in civil engineering. In this context, the paper presents a simple but effective approach to integrate PD with OpenSees by using a Client-Server (CS) software integration technique, such that the existing material constitutive models in OpenSees can be directly used by PD. Two applications are presented to verify the new PD-OpenSees platform. The first one is a plate with a pre-crack subject to horizontal load simulated using a three-dimension (3D) multi-yield-surfaces plasticity model, and the second one is a concrete block with a rectangular hole subject to a uniaxial loading condition simulated using a 3D Cap plasticity model. It shows that the generation/propagation of cracks of the elastoplastic materials (e.g., concrete and soil) can be analyzed by combing PD and three-dimensional plasticity constitutive models without compiling/linking these complex material models into PD program. Thus, the integrated PD-OpenSees platform presented herein is potentially capable to solve a wide range of complex problems in civil engineering
Coupling of Peridynamics and Numerical Substructure Method for Modeling Structures with Local Discontinuities
Get PDFPeridynamics (PD) is a widely used theory to simulate discontinuities, but its application in real-world structural problems is somewhat limited due to the relatively low-efficiency. The numerical substructure method (NSM) presented by the authors and co-workers provides an efficient approach for modeling structures with local nonlinearities, which is usually restricted in problems of continuum mechanics. In this paper, an approach is presented to couple the PD theory with the NSM for modeling structures with local discontinuities, taking advantage of the powerful capability of the PD for discontinuities simulation and high computational efficiency of the NSM. The structure is simulated using liner elastic finite element (FE) model while the local cracking regions are isolated and simulated using a PD substructure model. A force corrector calculated from the PD model is applied on the FE model to consider the effect of discontinuities. The PD is integrated in the substructure model using interface elements with embedded PD nodes. The equations of motions of both the NSM system and the PD substructure are solved using the central difference method. Three examples of two-dimensional (2D) concrete cantilever beams under the concentrated force are investigated to verify the proposed coupling approach
Fragility Assessment of Pre-Northridge Steel Moment Frames Using Finite-Length Plastic Hinge Elements and Concentrated Plasticity Fracture Elements
Get PDFAlthough pre-Northridge earthquake steel moment resisting frame buildings have been shown to be susceptible to brittle connection failures, they still represent a large fraction of the existing steel buildings in the United States of America. In this study, the performance of the 3- and 9-story Los Angeles pre-Northridge SAC buildings are analyzed considering ductile and brittle beam-column connection failures, and their uncertainty. This paper contributes to understanding the influence of uncertainty associated with connections brittle fracture on building interstory deformation capacity and its impact on bias and variability of fragility functions and loss assessment. The results show that considering brittle connections leads to significantly larger drift demands and to higher repair costs, particularly under intense ground shaking. New fragility curve parameters are derived that account for the effect of the uncertainty of the strength and deformation capacity of brittle connections
Knowledge Composition and Its Influence on New Product Development Performance in the Big Data Environment
Get PDFProduct innovation is regarded as a primary means for enterprises to maintain their competitive advantage. Knowledge transfer is a major way that enterprises access knowledge from the external environment for new product innovation. Knowledge transfer may face the risk of infringement of the intellectual property rights of other enterprises and the termination of licensing agreements by the knowledge source. Enterprises must develop independent innovation knowledge at the same time they profit from knowledge transfers. Therefore, new product development by an enterprise usually consists of three types of new knowledge: big data knowledge transferred from big data knowledge providers, private knowledge transferred from other enterprises, and new knowledge developed independently by an enterprise in the big data environment. To find what the influences of different types of knowledge are on new product development (NPD) performance, a model is presented that maximizes the expected NPD performance. The results show that the greater the weight of independent innovation knowledge, the greater the performance of NPD. Enterprises tend to transfer knowledge from the external environment when the research and development (R&D) investment is much higher, and enterprises will speed up independent innovation when independent innovation knowledge is expected to bring a larger market share. The model can help enterprises to determine knowledge composition, the scale of R&D investment and predict the performance of NPD
Characterization and Influence of Nanofiber Flours of Wood Modified on Fresh State Properties of Cement Based Mortars
No full textNanofibrillated wood fiber was used as fillers in the partial cement matrix replacing the cement to a content of up to 2% by weight of cement. The nanofibrillated effect of wood fibers on porosity, thermal properties and compressive strength was studied. The results obtained showed an improvement in compressive strength of more than 40% with 1% by weight of wood fiber nanofibrillate. The addition of nanofibrillated wood fiber shows a good pore reduction, and the best result was obtained with emulsion of a mixture incorporating 1% by weight of wood fiber nanofibrillate in the presence of an anionic surfactant (SDBS). Thermal conductivity measurements and thermal expansion coefficient, compared to nanofibrillated wood fiber reinforced cement pastes, showed the reinforcing efficiency of cellulose fiber nanofibrillate. The degree of hydration of the cement increased with nanofibrillated wood fibers. This property has been confirmed by Fourier transform infrared spectroscopy. These analyzes revealed that the presence of nanofibrillated wood fibers generates and promotes the hydration of the cement, producing more portlandite and calcium silicate gel, which influences the compressive strength which gives a strong improvement
Physicochemical and Mechanical Performances of Technical Flax Fibers and Biobased Composite Material: Effects of Flax Transformation Process
No full textIn France, the use of flax fibers as reinforcement in composite materials is growing exponentially in the automotive sector, thanks to their good physicochemical properties, environmental reasons, health neutrality and due to the European Council Directives on the reuse, recycling and valorization of car components and materials. The aim of our study is to investigate biochemical, physicochemical, and mechanical properties of technical flax fibers to evaluate the impact of transformation processes (scutching, hackling, and homogenization) on final properties of associated composite materials. Different chemical analysis such as Van Soest (biochemical fraction measurement), FTIR (Fourier Transform InfraRed spectroscopy), and XRD (X-ray diffraction) were carried out on different process modalities and show that there is no significant difference in terms of biochemical fraction and crystallinity index. By the same token, mechanical behavior shows that Young’s modulus is not affected by the transformation process. This result is also observed for thermal behavior. The results highlight the fact that the transformation processes of technical fibers do not really affect their physicochemical and mechanical performances
Constrained Groove Pressing (CGP): Die Design, Material Processing and Mechanical Characterization
No full textConstrained groove pressing (CGP) is a severe plastic deformation (SPD) technique used as a strengthening method for sheet metal. In the current work, an optimal/cost-saving design for CGP dies was attained using the stress analysis tool in SolidWorks Simulation Xpress wizard. This study examined low-cost and widely industrially applied aluminium materials, i.e., pure 1050 Al and 5052 Al alloy. Each material was subjected to three passes of the CGP process using a 150 tons capacity press. For both materials, inter-pass annealing treatment was undertaken before the third pass. The effect of the number of CGP passes on the microstructure and tensile properties was studied after each pass. For CGPed pure 1050 Al with respect to the as-received material, the ultimate tensile strength (UTS), yield strength (YS) and YS/UTS ratio increased with an increasing number of CGP passes until the second pass, while elongation decreased with the number of passes. For CGPed 5052 Al alloy, the UTS and YS increased after the first pass and then decreased after the second pass. Variations in the elongation and YS/UTS ratio of 5052 Al alloy after the CGP process were insignificant. After inter-pass annealing and applying the third CGP pass, the strength of pure 1050 Al decreased, and that of 5052 Al alloy increased, which was attributed to the influence of composition on their structures. The strength-ductility balance decreased with an increasing number of CGP passes in both materials
Influences of ascorbic acid and gibberellic acid in alleviating effects of salinity in Petunia under in vitro
No full textSalinity is one of the abiotic stresses that limits the
growth and productivity of many crops. A possible survival strategy
for plant under saline conditions is to use compounds that could
minimize the harmful effects of salt stress on the plant development.
The objective of the presented study was to investigate the effect
of exogenous ascorbic acid (ASA) with or without gibberellic acid
(GA3) on key growth and biochemical parameters in two petunia
cultivars ‘Prism Rose’ and ‘Prism White’ under saline (150 mM
NaCl) and non-saline in vitro condition. Nodal cutting with an
axillary buds were used as explants. Application of 1 mM ascorbic
acid with or without 0.05 mM gibberellic acid into the MS medium
stimulated the length of shoots and the number of new shoots of
‘Prism Rose’; whereas, it decreased the root length and the number
of roots of both ‘Prism Rose’ and ‘Prism White’ under non-saline
condition. The addition of ascorbic acid with or without gibberellic
acid into the MS medium under saline condition, increased the
length of plants and the number of new shoots, but did not affect
their root number and length. NaCl treatments increased the
proline content and lipid peroxidation which was indicated by the
accumulation of malondialdehyde (MDA). The study revealed
a correlation between chlorophylls a and b content and the leaf
pigmentation intensity – parameter a*. Addition of 1 mM ascorbic
acid with 0.05 mM gibberellic acid into the MS medium plays
a protective role in salinity tolerance by improving the shoot
growth and the development as well as increasing the activities
of the antioxidant enzymes and other antioxidant substances
Hyaluronic acid inhibited the upregulation of heat shock protein 70 in human chondrocytes from osteoarthritis and Kashin-Beck disease
No full textThis study aimed to investigate the effect of hyaluronic acid (HA) on the expression of heat shock protein
70 (HSP70) in chondrocytes isolated from patients with osteoarthritis (OA) and Kashin-Beck disease (KBD). The
chondrocytes were collected from OA and KBD patients, and chondrocytes isolated from patients of accident injuries
were used as the control. The chondrocytes were treated with HA at different doses. HSP70 expression in chondrocytes
at both mRNA and protein levels was tested by PCR and Western blot analysis. Compared with control, both mRNA
and protein levels of HSP70 were higher in chondrocytes from KBD and OA. However, HA at the dose of 500 μg/
mL significantly inhibited HSP70 expression levels in both KBD and OA groups (P < 0.05). In conclusion, HSP70 is
highly expressed in chondrocytes of patients of OA and KBD. HA intervention inhibits the upregulation of HSP70 in
chondrocytes of OA and KBD patients and could be a promising agent for treatment of OA and KBD
Deterioration of Antioxidant Competence in Barley Lesion Mimic Mutant 194
No full textA barley mutant, 194, was observed to exhibit a leaf spot phenotype over the whole course of its growing period. In this study, the phenotype and antioxidant competence were studied in the lesion mimic mutant 194. Plant height was slightly higher in mutant 194 than in the wild type (WT). In addition, leaf spot per plant in mutant 194 was significantly higher than in WT. Antioxidant competence, as indicated by reactive oxygen species (ROS) accumulation, antioxidant enzyme activity, and the expression of antioxidant enzyme-encoding genes was also assessed in mutant 194. Compared to the WT, mutant 194 displayed a relatively higher accumulation of ROS, accompanied by lower activities of some antioxidant enzymes and downregulation of antioxidant enzyme-encoding genes. This demonstrated reduced antioxidant competence in mutant 194. The results suggested that this lower antioxidant competence of mutant 194 could lead to the accumulation of excessive ROS. This excess of ROS could induce programmed cell death and has the potential to promote disease resistance in mutant 194