Reinforced Concrete Box Beam Strengthened By Carbon-Fiber-Reinforced Polymer Subjected To Combined Shear And Torsion

Box beams, with high torsional stiffness, light weight, and great structural resistance, are popularly used in the bridge structures. However, these box beams may fail suddenly due to increased traffic volumes and loads and diminished capacity from deterioration. Fiber-reinforced polymer (FRP) strengthening technique has been studied and used in structures to improve the flexural and shear capacity of beams. However, very few strengthening studies have paid much attention to reinforced concrete (RC) box beams subjected to shear, torsion, and combined shear and torsion. Therefore, in this research, three sets of experiments on RC box beams strengthened with the carbon-fiber-reinforced polymer (CFRP) in shear, pure torsion, and combined shear and torsion were conducted. Based on experiments, the main aims are to: (a) predict the shear contribution of CFRP; (b) evaluate the strengthening effectiveness and predict the CFRP contribution to torsion; (c) investigate the behavior of strengthened box beams subjected combined shear and torsion and develop mathematical equations to predict strength. The fib Bulletin 14 model with the reduction coefficient proposed in effective strain of fiber could reliably predict the shear CFRP contribution to shear in strengthened RC box beam. In addition, it was found that the configuration of U-jacketing with longitudinal strips had a better performance in the torsional strengthening of RC box beam. One combined model had been revealed to be reliable and conservative in calculating the torsional strength of retrofitted RC beams. Further on, strengthening effectiveness of CFRP in combined shear and torsion to RC box beams was inversely proportional to torque-to-shear ratio. The derived equations with modified model of effective strain in fiber could give the desirable results of torsional strength to the strengthened or unstrengthened RC box beams subjected combined action

Evaluation of Ultimate Strength of Reinforced Concrete Beams Strengthened with FRP Sheets under Torsion

The ultimate torque of reinforced concrete (RC) members strengthened with fiber reinforced polymer (FRP) sheets does not only depend on the torque of RC members, but also on the FRP contribution to the torque. For structural design, predicting the accurate torsional capacity of the strengthened beams is considerably important. Three existing models for calculating the ultimate torsional moment of RC beams and two existing models for computing the FRP contribution to the ultimate torque are described and combined. Based on an experimental database collected from existing literature, six combinations were discussed and evaluated from the calculative values compared with the experimental results. The comparison shows that the combination of ACI 318 and fib Bulletin 14 models (Group 2), as well as Chinese and Ghobarah models (Group 6), can reasonably and accurately predict the ultimate torque of beams strengthened with FRP sheet. Furthermore, the ultimate torque of six boxsection beams strengthened with fully wrapping or U-wrap calculated by the Group 6 shows closely to the experimental results

Dynamical Models of Biology and Medicine

Mathematical and computational modeling approaches in biological and medical research are experiencing rapid growth globally. This Special Issue Book intends to scratch the surface of this exciting phenomenon. The subject areas covered involve general mathematical methods and their applications in biology and medicine, with an emphasis on work related to mathematical and computational modeling of the complex dynamics observed in biological and medical research. Fourteen rigorously reviewed papers were included in this Special Issue. These papers cover several timely topics relating to classical population biology, fundamental biology, and modern medicine. While the authors of these papers dealt with very different modeling questions, they were all motivated by specific applications in biology and medicine and employed innovative mathematical and computational methods to study the complex dynamics of their models. We hope that these papers detail case studies that will inspire many additional mathematical modeling efforts in biology and medicin

Behavior of Reinforced Concrete Box Beam Strengthened with CFRP U-Wrap Strips Under Torsion

The present study focuses on the torsional strengthening behavior of reinforced concrete (RC) box section beams that are widely used in bridges. Four RC box beams were fabricated, and three of them were wrapped by carbon fiber-reinforced polymer (CFRP) U-wrap strips with or without longitudinal strips. The different wrapping configuration, cracking angle, failure pattern, and tensile strain of fibers were investigated and discussed accordingly. The experimental results addressed that U-wrap strips strengthening also can upgrade the ultimate torque of beams moderately. In particular, using U-wrap and longitudinal strips to bond the box beams increased the torsional stiffness slightly. The same equation from different codes for calculating RC specimens can accurately predict the ultimate strength of the control beam, but the calculation of the fib model overestimated the torsional strengthening improvement of the wrapped specimens. However, Ghobarah et al. assumed approximately 3000με of the average ultimate fiber strain in calculating the ultimate strength of the wrapped box beams which shows in relatively appropriate agreement with testing results

Accelerated Cavitation Damage of Steels in Liquid Metal Environments

Cavitation can be described as a hydrodynamic phenomenon which involves in the formation and collapse of vapor bubbles in a liquid medium. It always accelerates the cavitation damage and brings about multi-scale interactions of cavitation erosion between materials and fluids. For example, corrosion by dissolution/reaction can accelerate cavitation erosion under different liquid temperatures and velocities to alter interface films, and multiphase interface structure can also in turn affect the interfacial flow regime to induce cavitation in various fluids. In this chapter, interfacial characteristics and erosion-corrosion mechanism of directionally solidified (DS) Fe-B alloy with various Fe2B lamellar spacing in flowing zinc were investigated. The results indicate that the formation of adhesive interfacial film not only depends on erosion time and Fe2B lamellar spacing, but also relies on epitaxial ζ accumulation determined by zinc flow effect. Meanwhile, microturbulence of flowing zinc can result in the formation of slip bands and erosion pits on the ζ-FeZn13 surface. The flow-induced localized corrosion appears to accelerate the erosion-corrosion damage of interfacial adhesive film structure and morphology, which reveals underlying erosion mechanism of liquid metal

The GUA-Speech System Description for CNVSRC Challenge 2023

This study describes our system for Task 1 Single-speaker Visual Speech Recognition (VSR) fixed track in the Chinese Continuous Visual Speech Recognition Challenge (CNVSRC) 2023. Specifically, we use intermediate connectionist temporal classification (Inter CTC) residual modules to relax the conditional independence assumption of CTC in our model. Then we use a bi-transformer decoder to enable the model to capture both past and future contextual information. In addition, we use Chinese characters as the modeling units to improve the recognition accuracy of our model. Finally, we use a recurrent neural network language model (RNNLM) for shallow fusion in the inference stage. Experiments show that our system achieves a character error rate (CER) of 38.09% on the Eval set which reaches a relative CER reduction of 21.63% over the official baseline, and obtains a second place in the challenge.Comment: CNVSRC 2023 Challeng

Control of the Hydroquinone/Benzoquinone Redox State in High-Mobility Semiconducting Conjugated Coordination Polymers

Conjugated coordination polymers (c-CPs) are unique organic–inorganic hybrid semiconductors with intrinsically high electrical conductivity and excellent charge carrier mobility. However, it remains a challenge in tailoring electronic structures, due to the lack of clear guidelines. Here, we develop a strategy wherein controlling the redox state of hydroquinone/benzoquinone (HQ/BQ) ligands allows for the modulation of the electronic structure of c-CPs while maintaining the structural topology. The redox-state control is achieved by reacting the ligand TTHQ (TTHQ=1,2,4,5-tetrathiolhydroquinone) with silver acetate and silver nitrate, yielding Ag4TTHQ and Ag4TTBQ (TTBQ=1,2,4,5-tetrathiolbenzoquinone), respectively. In spite of sharing the same topology consisting of a two-dimensional Ag−S network and HQ/BQ layer, they exhibit different band gaps (1.5 eV for Ag4TTHQ and 0.5 eV for Ag4TTBQ) and conductivities (0.4 S/cm for Ag4TTHQ and 10 S/cm for Ag4TTBQ). DFT calculations reveal that these differences arise from the ligand oxidation state inhibiting energy band formation near the Fermi level in Ag4TTHQ. Consequently, Ag4TTHQ displays a high Seebeck coefficient of 330 μV/K and a power factor of 10 μW/m ⋅ K2, surpassing Ag4TTBQ and the other reported silver-based c-CPs. Furthermore, terahertz spectroscopy demonstrates high charge mobilities exceeding 130 cm2/V ⋅ s in both Ag4TTHQ and Ag4TTBQ