Increased Energy Dissipation Research Articles

Analysis of bolt bonding surfaces by the finite element method based on the equivalent Iwan model

This study establishes a finite element model based on the Iwan model to accurately characterize the force–displacement relationship and energy dissipation in bolted joints under small-amplitude tangential displacement. The force–displacement behavior of the Iwan model is transformed into a stress–strain relationship using a hybrid hardened intrinsic model. A subroutine developed with UMAT and UHARD is used to simulate the elastic–plastic behavior of the Iwan model during surface contact in the finite element model. Three-dimensional modeling and joint simulation are conducted using ABAQUS software. Experimental data verify the model's validity, and the effects of multiple factors on the bolted bonding surface are analyzed. The influence of friction coefficient, cyclic displacement amplitude, and preload on the force–displacement relationship of the bolted bonding surface is explored. Polynomial interpolation of the loading and unloading curves is applied to investigate the energy dissipation phenomenon. Results show that the finite element method can effectively reflect the hysteresis and energy dissipation behavior of the bonding surface. Increased friction coefficient and preload improve residual stiffness and energy dissipation capacity, while larger cyclic displacement amplitudes increase energy dissipation but have a minimal effect on residual stiffness.

Ultraviolet radiation inhibits mitochondrial bioenergetics activity.

Mitochondria play an important role in cellular function, not only as a major site of adenosine triphosphate (ATP) production but also by regulating energy expenditure, apoptosis signaling, control of the cell cycle, cellular growth, cell differentiation, transportation of metabolites, and production of reactive oxygen species. Interaction with electromagnetic waves can lead to dysregulation or alterations in the patterns of energy activities in the mitochondria. Ultraviolet light (UV) can be found in sunlight and artificial sources, such as lamps. UV radiation can cause damage to DNA, proteins, and lipids. Besides that, UV radiation is largely used in microorganism disinfection. To establish possible alterations in mitochondrial bioenergetics, this study proposes to investigate the UV (at two distinct intervals) effects on isolated mitochondria from mice liver to obtain direct responses and selective permeability of the internal membrane information. UVA-371 and UVC-255 nm lamps were used to irradiate, at different doses varying from 22.5 to 756 mJ/cm2, isolated mitochondria samples. Mitochondrial respiration pathways were investigated by high-resolution respirometry, and possible mitochondrial membrane damages were evaluated by mitochondrial swelling by spectrophotometer analysis. UVC irradiation results (in the higher dose) indicate decrease in 75% of mitochondrial bioenergetics capacity, such as limitation of oxidative phosphorylation in 60% and increased energy dissipation in 30%. Mitochondrial swelling experiments (spectrophotometer) indicated inner membrane damage, and consequently a loss of selective permeability. Direct correlation between irradiation and effect responses was observed, mitochondrial bioenergetics is severely affected by UVC radiation, but (UVA) radiation did not present bioenergetic alterations. These alterations can contribute to improving the knowledge behind the cell death mechanism in disinfection UV light and UV therapy such as phototherapy.

Unleashing the elastocaloric cooling potential of 3D-printed NiTi alloy with heterogeneous microstructures and Ni4Ti3 nanoparticles

Toward the development of elastocaloric (eC) refrigeration applications, this study examines how Ni4Ti3 nanoparticles improve the eC properties of laser powder bed-fused (LPBF) NiTi alloys, with a focus on the formation of a NiTi/Ni4Ti3 nanocomposite. The LPBF-produced microstructure offers significant advantages: i) a heterogeneous grain structure that provides complementary benefits—fine grains offer higher deformation resistance while coarse grains initiate phase transformation (PT) earlier, releasing more latent heat; ii) a strong <001>//building direction texture that enhances recoverability. However, these benefits are partially limited by grain boundary slip during PT, leading to lower cooling efficiency and increased energy dissipation in as-built NiTi alloys. To address these issues, Ni4Ti3 nanoparticles are introduced through aging treatment, forming a composite structure that strengthens grain boundaries. Given the challenges of applying severe plastic deformation to 3D-printed components, this approach may offer a more practical solution. The study also reveals that Ni4Ti3 nanoparticles contribute to: 1) reducing Ni content in the matrix, increasing lattice size and enthalpy, which enhances the temperature drop (ΔTad); and 2) promoting R phase formation, which hinders the B2↔B19' PT, reducing energy dissipation and improving the coefficient of performance (COPmat). The balance of these effects depends on nanoparticle size, with smaller particles (∼5–12 nm) amplifying the second effect, while larger particles (∼130 nm) increase the first effect. At 350°C aging, the optimized nanocomposite exhibits a maximum COPmat of 15 and ΔTad of 14K, representing a 163% improvement over the as-built alloy. This work highlights the potential of NiTi composites in 3D-printed eC components.

Microwave Frequency Analysis of Dielectric Properties in Biological Tissues: Insights into Dielectric Constant, Conductivity, and Resistivity at 9.4 GHz

This study investigates the dielectric properties of various biological tissues at microwave frequencies, specifically focusing on their dielectric constant, conductivity, resistivity, and loss tangent. Using methods such as Von Hippel’s and Yadav Gandhi’s techniques, the dielectric characteristics of heart, liver, brain, and muscle of chicken tissues were analysed at 9.4 GHz. It is found that tissues with higher water content exhibit greater dielectric constants and conductivities, while those with higher solid content, like liver, display higher resistivity. It has also been observed that tissues with lower dielectric constants and conductivities are those with greater absorption indices, which are typically associated with increased energy dissipation as heat. An increasing amount of energy dissipation may result from tissues with higher absorption rates being less effective at transferring microwave energy, as suggested by this inverse connection, which also emphasizes the complexity of electromagnetic wave interaction within tissues. This work provides critical insights into the interaction of electromagnetic waves with biological tissues, which is essential for applications in medical diagnostics, therapeutic technologies, and electromagnetic exposure safety standards.

Parametric optimization of SIP connection geometry in CFS-MRF structures: A finite element study

The structural buildings should be designed to resist both static and dynamic loads. There are different types of structural systems that can support seismic loads. Moment-resisting frames (MRFs) are widely used for seismic purposes, relying on the plastic deformations occurring between the beam and column. The main problems of cold-formed steel sections in MRFs during seismic loads are premature local and distortional buckling, which cause severe damage under strong earthquakes, such as early loss of connection strength, low ductility, and low energy dissipation. This paper clarifies the performance of the CFS section with steel interconnected part (SIP) in moment-resisting frames (MRFs) in many aspects using finite element (FE) procedures. The study summarizes the required dimensions of SIP to achieve optimal behavior for the beam-column connection. Additionally, an advanced connection consisting of SIP and four pairs of out-of-plane stiffeners has been examined. The locations of the out-of-plane stiffeners have been carefully selected to stabilize the connection. A cantilever beam connection has been used to represent an MRF in an advanced way. The connection consists of 2 C channel back-to-back beams connected with a through plate with sixteen bolts. Numerical models have been developed and verified with experimental tests under both monotonic and cyclic loading. The characteristics and creation of the numerical model are well illustrated in this paper. Cyclic loading has been applied according to AISC protocol, which is used to test the performance of the steel connections, as well as to classify the connection according to different design codes. The results show that increasing the plastic moment capacity of the CFS section decreases the required SIP dimensions to achieve optimal behavior by the connection. Additionally, it has been found that using out-of-plane stiffeners in particular locations with SIP increases energy dissipation on average by 74 %. Using stiffeners with SIP can upgrade the classification of the connection from an ordinary or intermediate moment connection to a special moment connection without the need to increase the CFS cross-section area or reduce the slenderness ratio, which in turn reduces the overall costs of construction.

Novel fillers for wearable technology: Impact of titanium carbide and thinners on room temperature vulcanized silicone rubber composites

Wearable technology has emerged as a robust pathway to achieve smart functionalities in healthcare, sports, fitness, and beyond. This study investigates the mechanical and electromechanical properties of silicone rubber (SR) composites. The SR was reinforced with titanium carbide (TiC) and modified with varying (room-temperature vulcanized) RTV-thinner (silicone oil) concentrations. RTV-SR was utilized, which cures at room temperature to form a flexible, durable, and moldable rubber widely used for sealing, bonding, and making molds. The addition of TiC enhanced tensile strength from 0.5 MPa (control) to 0.59 MPa (5 phr of TiC), and tensile modulus from 0.41 MPa to 0.51 MPa. However, the thinner inclusion reduced tensile properties. For instance, the T10 sample (10 phr thinner) showed a tensile strength of 0.51 MPa and a tensile modulus of 0.29 MPa making the composites soft. Thinner addition also increased ductility, with fracture strains rising from 151 % (control) to 217 % (T10). Compressive strength followed a similar trend, with the control and 5 phr TiC samples exhibiting compressive strengths of 0.18 MPa and 0.17 MPa, respectively, which decreased to 0.12 MPa for the T20 sample. Under cyclic loading, TiC-filled samples showed consistent load patterns, while thinner addition resulted in increased energy dissipation and reduced stiffness. Electromechanical analysis revealed that TiC 5 phr samples exhibited stable piezoelectric responses, with voltage outputs increasing from ±0.1 mV at 15 % strain to ±1.0 mV at 40 % strain. The T5 samples demonstrated significant voltage improvements, generating ±2.5 mV at 15 % strain and ±5 mV at 40 % strain. Long-term cyclic tests confirmed the stability of T5 samples, maintaining voltage outputs of −1.5 mV to 1.5 mV over 50 minutes. Response time analysis indicated faster response times for TiC 5 phr samples, decreasing from 145 ms at 15 % strain to 102 ms at 40 % strain, while thinner addition led to longer response times. Real-time electromechanical tests under mechanical study showed that T5 samples achieved optimal performance with voltage peaks up to ±2.4 mV under thumb pressing. These findings highlight the trade-off between mechanical strength and flexibility, suggesting that an optimal balance of TiC and thinner enhances the properties of silicone rubber composites for applications in wearable technology and sensors.

Numerical investigation of rip currents near a barred beach induced by irregular waves

Rip currents pose a common natural hazard at coastal tourist beaches, presenting a significant threat to the safety of beachgoers and beach management. To better understand the characteristics of rip currents, particularly those induced by irregular waves on a barred beach, this study utilized a Boussinesq-type, phase-resolving hydrodynamic model for numerical simulations. We investigated various factors, including significant wave height, peak period, incident angle, and bottom friction, to assess their impact on rip currents formation. The results of our research reveal some key insights. Firstly, an increase in significant wave height and peak period fosters the development of rip currents. However, beyond a certain threshold, the intensity of the rip currents decreases. Conversely, a larger incident angle tends to reduce the intensity of rip currents. Additionally, higher bottom friction leads to increased energy dissipation during wave propagation, consequently resulting in decreased rip currents intensity. In an effort to create a more precise representation of real sea conditions, multi-directional waves were employed as incident waves in this study. An analysis of different standard deviations of directional distributions revealed that as the directional spread of incident waves widens, the waves become more susceptible to breaking, ultimately leading to a reduction in the intensity of rip currents.

Multiple Dynamic Hydrogen Bonding Networks Boost the Mechanical Stability of Flexible Perovskite Solar Cells

AbstractFlexible perovskite solar cells often experience constant or cyclic bending during their service life. Catastrophic failure of devices may occur due to the crack of polycrystalline perovskite films and delamination at the perovskite and the substrate interfaces, posing a significant stability concern. Here, a multiple dynamic hydrogen bonding polymer network is developed to enhance the mechanical strength of flexible perovskite solar cells in two ways. The main chain of poly(acrylic acid) decreases the mismatch of the coefficient of thermal expansion between the perovskite and the substrate by 16.7% through its flexibility and spatial occupation. The dopamine branch chains provide multiple dynamic hydrogen bonding sites, which contribute to increased energy dissipation upon stress deformation and reduce Young's modulus of perovskite by 54.3%. The inverted flexible perovskite solar cells achieve a champion power conversion efficiency of 23.02% and retain 81.3% of the initial PCE over 2000 h under continuous 1‐sun equivalent illumination. Moreover, devices show excellent mechanical stability by remaining 90.2% of the original value after 5000 bending cycles.

Structural elucidation, morphological properties, dielectric properties and their physical interpretation of cerium-substituted cobalt and barium-based M-type hexagonal nano ferrites

This research uses the sol–gel method to look into how adding Co2+ and Ce3+ dopant cations changes the structure, shape, and electrical properties of M-type Ba hexagonal ferrites that have been synthesized. x-ray diffraction (XRD) analysis confirms the successful formation of the targeted hexagonal M-type crystal structure. We observed a reduction in unit cell volume and lattice parameters as the dopant concentration increased, indicating the effective incorporation of dopant ions into the crystal lattice. When the doping process happened, needle-like grain shapes appeared, which could be seen with a field emission scanning electron microscope (FESEM). As the concentration of the dopant increased, the dielectric spectroscopic measurements revealed an increase in the loss tangent (tan δ) from 0.05 to 3.68, and a decrease in the dielectric constant (ε′) from 283 to 3.41. This suggests a reduction in polarization and dielectric permittivity, as well as increased energy dissipation within the material. The electric modulus spectra showed relaxation behaviour that was non-Debye-type, which is another sign that there are complex and multifaceted ways for charges to move. The measurements of relaxation time and AC conductivity showed that the relaxation intervals were not regular and that the conductivity dropped from 2.22*10–4 Ω−1m−1 to 1.4*10–7 Ω−1m−1 as the doping concentration increased. Based on these findings, it seems that the processes of conductivity and dielectric relaxation play a big role in how charges move around in the doped ferrites. We validated complex impedance data obtained through electrochemical impedance spectroscopy (EIS) software against calculated impedance values. The derived grain and grain boundary characteristics also agreed with the observed grain distribution and boundaries from the micrographs, further corroborating the analysis.

Analysis of size effect and its influencing factors of brittle red sandstone with different heights

We carried out uniaxial compression tests on brittle red sandstone with different heights. The test results show that the uniaxial compressive strength of rock sample increases first and then tends to be stable with the increase of the size, which is approximately stable between 75 and 81 MPa. Both elastic energy and dissipated energy increase with the increase of rock sample size. In order to further analyze the mechanism behind these phenomena, we combined advanced numerical simulation and theoretical analysis to explain these phenomena, and systematically analyzed the end face effect as one of the key factors affecting the uniaxial compression characteristics of brittle red sandstone for the first time. Small sized rock samples are very sensitive to end effect. The middle of the large sized rock samples is in a uniform compression state, and the effect of end effect is weakend. When there are rigid pads at both ends of the rock sample, there is an obvious elastic vertebral body during the loading process of the rock sample. The bearing capacity of rock samples with rigid pads is greater than that of rock samples without rigid pads, and the energy released during instantaneous failure of rock samples without rigid pads is greater than that of rock samples with rigid pads. The findings of this paper make a valuable contribution to establishing optimal study sample sizes and advancing the utilization of laboratory test mechanics parameters in engineering applications.

Development and experimental validation of a novel double-stage yield steel slit damper-buckling restrained brace

This research is focused on the development and experimental validation of a novel double-stage yield steel slit damper-buckling restrained brace (SSD-DYB) system designed for seismic resistance of steel structures. The SSD-DYB integrates the energy dissipation capability of a steel slit damper (SSD) in its initial segment, enhancing performance in the case of lower seismic intensities levels while employing a larger segment for higher load resistance to maintain structural stability. The results of the study show that the proposed SSD-DYB is capable to reduce the weight of similar all-steel buckling restrained braces (BRBs) successfully addressing critical points through stiffeners and top and bottom plates. Additionally, the U-shaped element exhibits resilience during seismic loads, indicating its potential for replacing cores without failure which would be beneficial for seismic retrofitting of buildings. Experimental tests show that varying the number and shape of SSD strips significantly impacts the hysteresis curve's maximum load and dissipated energy (i.e., adding strips increased energy dissipation by 33.48 % for SSD-DYB-1), which can be used to control the proposed device for a specific performance target. Stopper mechanisms within the SSD-DYB regulate load distribution between segments and can be used to control the device and its transmitting capacities. Finally, an optimized SSD-DYB has been proposed with promising performance to be used by researchers for designing new structures or retrofit old ones.

Failure Analysis and Piezo-resistance Response of Intralaminar Glass/Carbon Hybrid Composites Under Blast Loading Conditions

Abstract In this study, damage mechanisms and the piezo-resistance response of glass/carbon intralaminar hybrid composites are examined under blast loading conditions. Two-ply orientations are considered, namely a repeating ((G45C45)R) and an alternating ((G45C45)A) +/− 45° glass/carbon layers, along with three boundary condition configurations: simply supported, partially fixed, and fully fixed are applied. A shock tube apparatus and the three-dimensional digital image correlation technique are utilized to investigate the interaction of shock waves with the composites and gather a comprehensive deformation field during the loading. A modified four-probe resistivity measurement method is implemented to comprehend the piezo-resistance response associated with damage evolution. The results underscore the substantial influence of boundary conditions on the blast mitigation capacity of the composites. Analysis following the experiments reveals that the damage to the specimens primarily involves the fracture of fibers accompanied by internal delamination. Thermal imaging of the tested composite specimens provides enhanced insight into the precise occurrences of internal fiber breakage and delamination. Composites of (G45C45)A type demonstrate an increased energy dissipation ranging from 18% to 33% compared to (G45C45)R composites, depending on the specific boundary conditions among the three types considered. Furthermore, the findings indicated a strong correlation between changes in piezo-resistance and the fracture of carbon fibers, coupled with the sustained deformation of the composites. Notably, (G45C45)A composites exhibited 100% ∼ 300% higher change in piezo-resistance compared to (G45C45)R composites, indicative of the superior damage-sensing capabilities of the former.

Highly adhesive and impact‐strengthening supramolecular polyurethane derived from facile incorporation of UPy motifs toward energy dissipation binding applications

AbstractThe implementation of hot melt adhesives reaching structural adhesion with both impact resistance and detachability is of prospective industry value but still remains challenging. In this work, 2‐amino‐4‐hydroxy‐6‐methylpyrimidine serving as both chain extender and end‐capping reagent due to its isomerism, was developed to construct a supramolecular polyurethane‐derived hot melt structural adhesive. The as‐synthesized PUM elastomers occurs obvious decrease of molecular weight at 80°C compared to room temperature, revealing the existence of self‐complementary 2‐ureido‐4[1H]‐pyrimidinone (UPy) motifs at chain ends. This unique structure allows to chemically incorporate abundant hierarchical and quadruple hydrogen bonding moieties, which results in remarkable enhancement of shear strength, ranging from 6.4 to 16.6 MPa. More importantly, it also exhibits unique impact‐strengthening and reproducible adhering ability. The Hopkinson‐press‐bar and cyclic tensile tests manifest that quadruple hydrogen bonds play a pivotal role in buffering external forces and increasing energy dissipation when exposed to high velocity impacts. The true stress and strain synchronously increase as the strain rate augments while the shear strength can even roar up to ~18 MPa at high tensile speed. With regard to mild synthetic conditions, atomic economic use of reactants, it is promising that this material has industrial potential to be utilized in applications referred to energy‐absorption and reproducible structural adhesion.

Comparison of hydrodynamics and micromixing quality in a two-stage microreactor with intensely swirled flows and in a T-mixer

The advantages of a two-stage microreactor with intensely swirled flows (MRISF-2) in comparison with a T-mixer are studied. Both numerical simulation and experimental study were used. The best way of solutions feeding was found experimentally, through the tangential inlet pipe and axial nozzle. It was revealed that the maximum values of the specific energy dissipation rate and correspondingly the best quality of micromixing are achieved with this method. The results of numerical simulation demonstrate the predominant energy dissipation in the neck of MRISF-2, which is a key knowledge for the proper use of such type of microreactors for co-precipitation reactions, because the micromixing quality plays crucial role in the synthesis of nanosized particles. The specific energy dissipation rate in the neck is from 10 to 20 times higher than just upstream or downstream the neck. The micromixing quality (index of segregation) in MRISF-2 was one order of magnitude better compared to the T-mixer; besides, the MRISF-2 allows to increase energy dissipation rate in a much wider range.

Numerical and Analytical Study of the Cyclic Behavior of ADAS Damper and the Effect of Axial Force on its Behavior

ABSTRACT The objective of this research was to study ADAS dampers and develop equations to calculate their seismic parameters. A model was used to analyze the dampers with various variables. The study proposed equations for stiffness, energy dissipation, and strength of the dampers. It also identified the variables with the most and least impact on the results. The effect of axial force on damper performance was investigated, including the calculation of critical load and examining its influence on stiffness, strength, and ductility. Reducing the opening area and height and increasing the width of the damper increased energy dissipation and effective stiffness.

Development and characterization of self-centering friction dampers with confined shape memory alloy bars

This study proposes a new self-centering, shape memory alloy bar-based device to address the tension-compression asymmetry and limited energy dissipation capacity of similar SMA bar-based devices. The proposed device, named the Confined Superelastic Friction Damper (CSFD), employs buckling-restrained SMA bars to maintain symmetry in force-displacement responses and enhance effectiveness in both tension and compression. The device also integrates a frictional damping mechanism, contributing to increased energy dissipation capacity. First, an optimal annealing condition is investigated for as-received SMA bars to achieve a satisfactory superelastic response. Then, the working and design principles of the CSFD are outlined. The experimental characterization of CSFD devices in various configurations is conducted under an increasing amplitude loading protocol. The devices are tested with different levels of frictional damping to assess the effects of the added frictional forces on device characteristics. Analysis of test results considers parameters such as hysteresis curves, maximum force, equivalent viscous damping, and self-centering efficiency to provide a comprehensive performance evaluation of each device. Findings reveal that while a single buckling-restrained SMA bar device exhibits up to 90 % higher forces in compression than in tension, a CSFD device with two such bars nearly eliminates this asymmetry. Compared to tension-only SMA devices, capable of symmetric response, the proposed CSFD device demonstrates a 2.6 times higher force-resisting capacity. For all devices, the addition of some frictional damping improves the energy dissipation and equivalent viscous damping capacity, while leading to some reduction in self-centering efficiency.

Numerical Simulation of the Dovetail Tee and Hydraulic Optimization of the Height Difference for Pipeline in a Liquefied Natural Gas Filling Station

Certain configurations of liquefied natural gas refueling stations exhibit a deficiency in managing boil-off gas. Furthermore, the ill-conceived linkage between the submersible pump and the gas storage tank pipeline leads to impeded natural gas transmission. This study employed the computational fluid dynamics (CFD) methodology to scrutinize the hydrodynamic attributes of the T-type tee and dovetail tee configurations implemented in the pipeline design connecting the submersible pump and storage tank in a liquefied natural gas (LNG) filling station across diverse operational scenarios. The T-type tee induces detachment of the primary flow from the inner wall due to inertial forces, which results in vortex formation and heightened resistance, accompanied by increased energy dissipation. The transition of the rounded inner wall of the dovetail tee results in the reduction of eddy current generation and a smaller separation zone, thus minimizing resistance and energy loss. The maximum static differential pressure between the inlet and outlet of the dovetail tee is reduced by 52.52% compared to that of the T-type tee. In practical engineering applications, the use of dovetail tees leads to a reduction in the height difference for the pipeline by 17.58%, resulting in more uniform and stable flow rates and pressures in the flow field. These improvements contribute to engineering efficiency and environmental sustainability and are particularly evident in the design of LNG filling stations.

CFD-PBM coupled modeling of the liquid-liquid dispersion characteristics and structure optimization for Kenics static mixer

Kenics static mixers (KSM) are extensively used in industrial mixing–reaction processes by virtue of high mixing efficiency, low power homogenization and easy continuous production. Resolving liquid droplet size and its distribution and thus revealing the dispersion characteristics are of great significance for structural optimization and process intensification in the KSM. In this work, a computational fluid dynamics–population balance model (CFD–PBM) coupled method is employed to systematically investigate the effects of operating conditions and structural parameters of KSM on droplet size and its distribution, to further reveal the liquid–liquid dispersion characteristics. Results indicate that higher Reynolds numbers or higher dispersed phase volume fractions increase energy dissipation, reducing Sauter mean diameter (SMD) of dispersed phase droplets and with a shift in droplet size distribution (DSD) towards smaller size. Smaller aspect ratios, greater blade twist and assembly angles amplify shear rate, leading to smaller droplet size and a narrower DSD in the smaller range. The degree of impact exerted by the aspect ratio is notably greater. Notably, mixing elements with different spin enhance shear and stretching efficiency. Compared to the same spin, SMD becomes 3.7–5.8 times smaller in the smaller size range with a significantly narrower distribution. Taking into account the pressure drop and efficiency in a comprehensive manner, optimized structural parameters for the mixing element encompass an aspect ratio of 1–1.5, a blade twist angle of 180°, an assembly angle of 90°, and interlaced assembly of adjacent elements with different spin. This work provides vital theoretical underpinning and future reference for enhancing KSM performance.

Joint shear strength prediction for fiber reinforced concrete beam-to-column connections

Beam-to-column joints experience substantial shear forces and deformations, playing a pivotal role in maintaining the overall stability and integrity of moment-resisting frames under earthquake loading. If fiber reinforced concrete is used instead of reinforced concrete, beam flexural failure can be achieved, which leads to a ductile behavior and increased energy dissipation capacity, when compared to joint shear failure. To ensure a ductile failure mode, accurate prediction of the joint shear strength is essential. However, there are only a limited number of analytical studies on predicting the shear strength of fiber reinforced concrete joints, most of which are only applicable to steel fibers. In this study, a comprehensive database of prior experiments conducted on fiber reinforced concrete beam-to-column connection subassemblies is compiled. Based on Pearson Correlation Analyses, the factors influencing the seismic response are determined to be the composite tensile cracking strength, axial load on the column, aspect ratios of member dimensions, and specific fiber properties such as aspect ratio and volume fraction. A joint shear strength prediction equation is then developed utilizing statistical nonlinear regression method. Validation against experimental data confirms that the proposed equation provides conservative estimates of joint shear strength and can be utilized for composites with any fiber type, even hybrid fibers; in contrast to existing equations which often lead to overestimation of strength and restricted to a specific fiber type. Moreover, the proposed equation provides engineers a practical tool to assess the seismic behavior of such connections, which has not been addressed by current structural design codes yet. The improved accuracy of the proposed equation, demonstrated by the lowest mean absolute error and coefficient of variation and the highest coefficient of correlation, positions it as a promising candidate for integration into structural design codes.

Diffusional and Biochemical Limitations to Photosynthesis Under Water Deficit for Field-Grown Cotton.

Water deficit stress limits net photosynthetic rate (AN), but the relative sensitivities of underlying processes such as thylakoid reactions, ATP production, carbon fixation reactions, and carbon loss processes to water deficit stress in field-grown upland cotton require further exploration. Therefore, the objective of the present study was to assess (1) the diffusional and biochemical mechanisms associated with water deficit-induced declines in AN and (2) associations between water deficit-induced variation in oxidative stress and energy dissipation for field-grown cotton. Water deficit stress was imposed for three weeks during the peak bloom stage of cotton development, causing significant reductions in leaf water potential and AN. Among diffusional limitations, mesophyll conductance was the major contributor to the AN decline. Several biochemical processes were adversely impacted by water deficit. Among these, electron transport rate and RuBP regeneration were most sensitive to AN-limiting water deficit. Carbon loss processes (photorespiration and dark respiration) were less sensitive than carbon assimilation, contributing to the water deficit-induced declines in AN. Increased energy dissipation via non-photochemical quenching or maintenance of electron flux to photorespiration prevented oxidative stress. Declines in AN were not associated with water deficit-induced variation in ATP production. It was concluded that diffusional limitations followed by biochemical limitations (ETR and RuBP regeneration) contributed to declines in AN, carbon loss processes partially contributed to the decline in AN, and increased energy dissipation prevented oxidative stress under water deficit in field-grown cotton.