Load Ratio Research Articles

A review on dynamic analysis of membrane based space structures

This paper presents a comprehensive review of the diverse approaches employed to study dynamic responses of gossamer membrane structures for space applications. The primary aim of the current review article is to explore the proposals/attempts made in the literature to understand the vibration, wrinkling, and shape control phenomena of these structures using analytical, experimental, and numerical approaches. This review delves into understanding the impact of various parameters/factors such as membrane thickness, aspect ratio, geometric and material properties, aspect ratio, types of load, load ratio, boundary conditions, air added mass, inflation pressure, type of actuators, and their placements etc. on the behavior of membrane structures.

Applicability evaluation of a temperature humidity index-controlled ventilation system in livestock using a building energy simulation model

In general, for livestock building, a simple system for controlling the HVAC system that is based only on the indoor air temperature is applied. This study evaluated the applicability of temperature humidity index (THI)-based ventilation systems installed in livestock buildings using a building energy simulation model. Based on the monitoring data of an actual pig house, the integrated predictive performance of the indoor temperature and humidity of the building energy simulation model was calibrated. Additionally, the indoor environment of the existing temperature-based control and THI-controlled ventilation systems was compared through simulations. The average THI and the section exceeding the THI threshold were both lower compared to the existing system. This was because the part load ratio of the fans of the THI-controlled ventilation system was higher than that of the existing system, indicating better ventilation. These results suggest that THI-based ventilation systems can overcome the limitations of existing temperature-based systems and effectively improve the thermal stress management of livestock buildings. This study portrays that the indoor environment can be improved by simply changing control variables, while presenting the field applicability and research value of THI-based control systems in the management of livestock environments.

Constitutive model of an additively manufactured combustor material at high-temperature load conditions

ABSTRACT In this paper, the high-temperature constitutive behaviour of an additively manufactured ductile nickel-based superalloy is investigated and modelled, with application to thermomechanical fatigue, low-cycle fatigue and creep conditions at temperatures up to 800 ∘ C. Thermomechanical fatigue tests have been performed on smooth specimens in both in-phase and out-of-phase conditions at a temperature range of 100 − 800 ∘ C, and creep tests at 625 ∘ C, 700 ∘ C, 750 ∘ C and 800 ∘ C. Additionally, low-cycle fatigue tests at different strain ranges and load ratios have been performed at 700 ∘ C, and tensile tests have been performed at 600 ∘ C, 700 ∘ C and 800 ∘ C. A clear anisotropic mechanical response is obtained in the experiments, where the anisotropic effects are larger at high stress levels in creep loadings. To capture this behaviour, a rate-dependent strain based on a double-Norton model has been adopted in the model, by which the creep and mid-life response of the thermomechanical fatigue tests can be simulated with good accuracy.

Cyclic behavior of a shape-optimized dumbbell-type combined slit damper with phased yielding characteristic

This paper proposed a shape-optimized dumbbell-type combined slit damper (SDCSD) that enables phased yielding. In SDCSD, the shape-optimized dumbbell-type energy dissipation element contributes to the elimination of stress concentration, while the phased yielding characteristic reduce the adverse effect of damage accumulation. The calculation method of mechanical properties of dumbbell-type energy dissipation element (EDE) and the working mechanism of SDCSD are introduced. Two different configurations of SDCSD were designed, including double dumbbell-type combined slit damper (DDCD) and stiffened dumbbell-type combined slit damper (SDCD). Quasi-static test on five specimens were carried out to discuss the effect of shape optimization, phased yielding mechanism and the mechanical properties of SDCSD. Additionally, numerical simulations were performed to further investigate the factors affecting the mechanical properties of the SDCD. The factors include the shape parameters (α and β), the thickness of the stiffening ribs (γ), the yield load ratio (Ry) and the height-to-thickness ratio (Rh). Based on the results of numerical simulation, the modified formula for calculating the mechanical properties of SDCD were presented. The results indicate that the dumbbell-type EDE obtains a more uniform stress distribution and higher material utilization. The stiffened dumbbell-type plate outperforms the conventional dumbbell-type plate in terms of hysteretic stability and energy dissipation. Both DDCD and SDCD could achieve the expected phased yielding, and DDCD provides superior loading and energy dissipation capacity. Moreover, the dumbbell-type EDE provides excellent energy dissipation when α is taken as 0.1 or 0.2 and β is taken as 0.3–0.5 or 0.5–0.6. The out-of-plane deformation of the dumbbell-type EDE is minimized when γ is taken as 0.5. It is recommended that the Ry and Rh of SDCD should be taken as 0.5 and 30–44, respectively. Besides, the modified formula reduces the maximum calculation error of mechanical properties from 49.99% to 23.53% and is considered to be applicable to the design of SDCD.

Study on fatigue crack growth property of abrasive waterjet peened aluminum alloy

Abrasive waterjet peening is a favorable surface treatment method for improving the fatigue resistance of metal materials. An insight into the fatigue crack growth properties of AWJ peened specimens is meaningful for obtaining better strengthening performance. In present work, a numerical model of AWJ peening was established and experimentally validated for investigating the fatigue crack growth characteristics of Aluminum specimens. The effect of peening and loading conditions on the fatigue performance was also analyzed. The results indicated that the stress intensity factor at the peened region was enhanced and the crack propagation was significantly inhibited by the compressive residual stress. The influence of compressive residual stress on the effective stress factor range is greater under lower external load and higher loading ratio. The fatigue life for reaching the crack length of 40 mm is increased by 37%, 60% and 98% after peening by using the intensity of 0.6 mmA, 0.8 mmA and 1 mmA, respectively.

Studi eksperimental kinerja mesin TV-1 (engine research test) berbahan bakar campuran diesel-biodiesel

This research is a laboratory experimental research that uses research testing machines. Using biodiesel fuel, a mixture of oil and diesel fuel. The composition of the biodiesel mixture used in this research was B35, B40, and B50 into diesel fuel in millilitres (ml). Tests were carried out by varying the load and compression ratio (CR), namely loads of 3 kg, 5 kg, 8 kg, and compression ratios of 14, 16, and 18. Data collection used observation techniques using tables to record the study results obtained. By using descriptive analysis techniques in the form of graphs and tables to make it easier to find out the study results. The results of the study from the engine performance research tests obtained were that performance increased with increasing loading at low compression ratios with the addition of biodiesel to diesel fuel, while at high compression ratios, the greatest power was obtained from B35 mixed fuel. However, the lowest fuel consumption in the mixture composition is the B35 mixture. Meanwhile, the lowest emission density opacity obtained was in the mixture of B35 and B40 biodiesel.

Experimental and numerical study on seismic behavior of precast shear walls assembled with a socket vertical joint

In the development of precast shear wall structures, reliable and efficient connections of precast units are crucial for their seismic behavior. Meanwhile, the heavy precast units using conventional concrete bring a low lifting efficiency. Considering these issues, the paper proposed a novel type of socket vertical joint for precast shear walls made of steel fiber reinforced lightweight aggregate concrete (SFRLAC). Sixteen socket connection specimens, with four socket depths (100 mm, 150 mm, 200 mm, and 250 mm) and two interface treatments (smooth and exposed aggregate), underwent interface bonding performance tests using uniaxial tensile testing and finite element (FE) numerical models to determine the appropriate socket depth. Three specimens were tested using the low-cyclic loading test, including two reinforced SFRLAC precast shear walls assembled with a socket vertical joint and a cast-in-place reinforced SFRLAC shear wall as a reference. The failure patterns and process of the shear walls were observed, while the load-displacement curves were obtained. Additionally, a parametric analysis of different influencing factors was conducted using finite element (FE) numerical models. This analysis studied the bearing capacity, energy dissipation capability, deformation ability, and stiffness degradation of the shear walls. Results indicate that when the precast shear walls were damaged, the socket vertical joint was integrity and failed in bending-shear. The three specimens exhibited fewer differences in seismic behavior with relatively full hysteretic curves. The seismic mechanisms of the shear wall assembled with a socket vertical joint were elucidated by analyzing the numerical distribution of stress in both SFRLAC and steel bars at different stress levels. Furthermore, an expansion analysis was conducted to assess the impact of axial load ratios and shear to span ratios on the seismic behavior of precast shear walls.

Nonlinear analysis and design of high-strength concrete filled steel tubular columns under nonuniform fires

The main objective of this study is to investigate the behaviour of concrete-filled steel tubular (CFST) columns with ultra-high strength concrete (UHSC) and high strength steel (HSS) under fires through finite element method (FEM). High-strength materials can be used in CFST columns to reduce member dimensions, lowering material consumption and foundation loads. However, their fire behaviour has been insufficiently examined, especially under nonuniform fire exposure. In this study, thermal-structural models of the composite columns are developed using the SAFIR software. The numerical results are compared with published test data on temperature distribution, axial displacement, lateral displacement, failure modes and failure time. Then, parametric analyses are conducted to investigate the influence of various factors such as concrete strength, steel strength, different fire exposures, column length and load ratio on the fire performance of the CFST columns. In addition, the tabular design approach in European code EN1994–1-2 and Australian/New Zealand code AS/NZS 2327:2017 for designing uniformly exposed CFST columns is evaluated. It is observed that the prescribed design values in the table for R30 and R60 fire ratings under load ratio lower than 0.47 appear insufficient for the allowable slenderer columns. The applicability of the tabulated data for a load ratio up to 0.47 is further checked for the columns with UHSC of 120 MPa and HSS of 690 MPa, which is the strength limits recommended in AS/NZS 2327:2017.

Optimizing alkaline solvent regeneration through bipolar membrane electrodialysis for carbon capture

This work demonstrates and characterizes the use of a bipolar membrane electrodialysis for pH-driven CO2 capture and solvent regeneration using potassium hydroxide solutions. The impact of potassium concentration, current density and load ratio on the CO2 desorption efficiency was analyzed and substantiated with an equilibrium model. The system was tested with partially saturated solutions that mimic the expected carbon content of alkaline solvents that have been in contact with flue gas (carbon loading of 0.6 and K+ concentration from 0.5 M to 2 M). Among the tested current densities, 1000 A/m2 demonstrated the highest CO2 desorption efficiency but also the highest energy consumption, whereas 250 A/m2 exhibited the lowest energy consumption (8.8 GJ/ton CO2) but lower CO2 desorption. Efficiency losses were associated with H+ transport across the membranes at high load ratios and decrease of the bipolar membranes water dissociation efficiency at low current densities. This work establishes key performance indicators and describes fundamental characteristics of continuous bipolar membrane electrodialysis systems for regeneration of alkaline solvents used in post-combustion CO2 capture.

ANALISA KENAIKAN BEBAN LISTRIK SEKTOR RUMAH TANGGA TERHADAP BEBAN PUNCAK DI KOTA PALANGKA RAYA

Electricity is an essential need in the life of Palangka Raya City, and it can be utilized across various sectors such as business, social, industrial, governmental, and household. The increase in population growth in Palangka Raya City has led to a rise in the demand for electricity, necessitating its regulation and efficient distribution to customers. Specifically in the electricity sector, particularly in households, the demand tends to fluctuate due to resistive, inductive, and capacitive loads. This study aims to analyze the load factor, which is the ratio of average load to peak load measured over certain periods such as daily, monthly, or yearly. The first step involves data collection in the household sector of Palangka Raya City, including tariff data and monthly consumption data. The second step involves classifying electrical loads followed by an analysis of load factor accumulation. The third step involves summarizing the results of the accumulation data. From the analysis, it is concluded that the highest load factor values are found in the R.1/450 VA category, with an average of 49.30%, and the highest power factor value is 83.16% compared to other load factor categories. However, tariffs for R.3/6,600 VA and above show a gradual decrease in load factor from February to December.

Energy-Saving Impact and Optimized Control Scheme of Vertical Load on Distributed Electric Wheel Loader

During the operation of a wheel loader, the external load acting on the bucket undergoes many changes, resulting in significant changes in the load ratio on the front and rear axles. For this reason, controlling a standard wheel loader is not trivial. In addition, in the case of a distributed electric wheel loader (DEWL), the operating control algorithm is often complex and is, therefore, the subject of optimization studies. This study compared the electric power consumption across different vertical loads, speeds, and travel directions for single-front, single-rear, and dual-motor configurations, both during transporting and pre-shoveling operations. The analysis led to the development of control rules based on energy-saving objectives. Under the shoveling condition, it was observed that vertical loads can lead to an insufficient driving force and skidding, necessitating the proposal of a new optimized control scheme. The results revealed that the optimal solution for transporting is the single-motor drive control scheme without a mechanical connection between the front and rear motor. With the single-motor control scheme, comparing the preferred controlled motor with the unselected motor under different loads, the average electrical power savings for forward, backward, and circling were at least 3.51%, 3.12%, and 0.34%, respectively. Under the pre-shoveling condition, the optimal control scheme was identified as the single rear motor control scheme, effectively reducing electrical power consumption. In response to the issues encountered during the shoveling condition, an economical solution involving the modification of the front axle transmission ratio has been proposed, along with an optimized control scheme based on vertical load variations.

Experimental and numerical investigation of through-diaphragm in H-shaped steel beam to CFST column connections

This research proposes a cruciform through-diaphragm (CTD) for an H-shaped steel beam to concrete-filled steel tubular (CFST) column and investigates its seismic performance experimentally and numerically. The proposed connection consists of through-plates passing through the aligned slots in the panel zone and end plates directly welded to an H-shaped steel beam. This connection eliminates welding inside the steel tube for installation of the diaphragm, while providing a reliable load path from the steel beam to the CFST column. The experimental program examined the connection hysteretic behaviors, including the moment-rotation response, ductility, initial stiffness, and energy dissipation capacity. The proposed connection shows stable hysteric behavior and good energy dissipation up to a story drift up to 4 % and satisfies the AISC seismic provisions criteria for special moment connection. A finite element (FE) model was established and verified against the experimental results. The effects of concrete infill, steel tube column thickness, axial load ratio, and through-plate thickness on the hysteretic behavior of the proposed connection were investigated through parametric analysis of 24 FE models. This study provides the information on the optimized design parameters that ensures the stable seismic performance of the proposed connection that could be used in structural engineering practice.

Research on Topology Optimization Design of Truss Structure

Due to continuous advances in engineering technology and architecture, the use of truss structures is expanding. The design method of ideal truss structure is the main research topic of this paper. The topology optimization method is applied to a bridge design case study. The load and total material utilization ratio of each rod of triangular truss, arch truss and Pratt truss were determined by using structural mechanics solver. By comparing the stress and material consumption of the truss structure, it shows that the truss structure has advantages in stress and can be used in the truss construction of short-distance arch bridge. Truss is the basic unit of the topology optimization method of truss structure proposed in this study. By optimizing the topological shape of the truss, the ideal design of the whole structure is realized. While maintaining structural stiffness and stability, the technology can significantly reduce the weight and cost of the structure.

Experimental investigation on cold-formed steel hollow sections with moderate heat treatment under combined compression and cyclic lateral loads

This paper presents an experimental investigation on cold-formed steel rectangular and square hollow sections (RHSs and SHSs) with subsequent heat-treatment under combined compression and cyclic lateral loads. A total of 25 specimens designed with different parameters, including slenderness ratios (b/t and d/t) and axial load ratio (n) ranging from 0 to 0.5 were tested. Material tests were carried out to confirm the material ductility requirements stated in Eurocode being reached. Failure modes, moment-rotation curves, secant stiffness, energy dissipation and plastic hinge length presented were analysed. In addition, deformation capacity was evaluated in terms of maximum and ultimate rotations. The comparison results between plastic rotation limits proposed by design codes and the test results indicate that AISC 341-16 is more suitable for the design of cold formed hollow sections with moderate heat treatment under this investigation, though the recommended reduction factor of axial load might be conservative.

Feasibility of sulfated BPA and BPS as wastewater-based epidemiology biomarkers: Insights from wastewater and reported human urine analysis

In wastewater-based epidemiology (WBE), the selection of appropriate biomarkers presents a significant challenge. Recently, sulfated bisphenols have garnered attention as potential WBE biomarkers due to their increased stability in wastewater compared to glucuronide conjugates. This study aims to comprehensively assess the feasibility of employing sulfated BPA and BPS as WBE biomarkers by analyzing both WBE and human biomonitoring data. To conduct this research, wastewater samples were collected from six domestic wastewater treatment plants in Guangzhou, China, and urinary concentration of BPA and BPS were obtained from peer-reviewed literature. The results revealed that mean urinary concentrations of BPA and BPS, calculated using Monte Carlo simulations, significantly exceeded those reported in human biomonitoring studies. Furthermore, the per capita mass load ratio of sulfated BPA and BPS in human urine to the mass load in wastewater was found to be below 10 %. This outcome suggests that the excretion of BPA-S and BPS-S in urine does not make a substantial contribution to wastewater, hinting at the existence of other notable sources. Consequently, our study concludes that sulfated BPA-S and BPS-S are not suitable candidates as WBE biomarkers. This work provides a referenceable analytical framework for evaluating the feasibility of WBE biomarkers and emphasizes the necessity for caution when utilizing WBE to assess human exposure to chemicals.

A digital twin approach toward unlocking elasto-plastic fatigue crack growth rates under negative load ratios

This paper introduces a novel digital twin solution for unlocking the elasto-plastic fatigue crack growth within an S550 steel under negative load ratios. The digital twin transforms solely strain data from a strain-interfaced welded plate joint specimen to the load–displacement curve to compute cyclic J-integral values using the η approach, eliminating the need for load and displacement measurements. The accurate computation of the elasto-plastic ΔJ effectively extends the fatigue crack growth relationship derived from standard fracture specimens. The extended fatigue crack growth relationship accurately predicts the fatigue life of specimens under separate step-up and step-down variable amplitude loading regimes.

Resistance Factor Spectra for the Ultimate Limit State of the National Building Code of Canada

Over the years, structural engineering codes and specifications in Canada and elsewhere have moved from an allowable stress design (ASD) approach to a load and resistance factor design (LRFD) philosophy. LRFD methodology takes better account of the inherent variability in both loading and resistance by providing different factors of safety for loads of distinct natures with regard to their probability of overload, frequency of occurrences and changes in point of application. The method also results in safer structures because it considers the behavior at collapse. While resistance factors for traditional construction materials based on LRFD in the National Building Code (NBC) of Canada are available, they cannot be used for non-conventional ones. This is because the resistance of such materials due to various load effects has unique bias factors (λR) and coefficients of variation (VR), which greatly impact their reliability index (β). In this study, relationships between the resistance factor ϕ and critical load effects from the NBC load combinations at ultimate limit states are developed for a wide range of resistance bias factors and coefficients of variation. The relationships are presented in the form of charts that are useful for researchers and code-writing professionals who have expertise in the various fields of structural engineering but lack proper background in reliability theory. The developed spectra showed that for the same ϕ, β increases with an increase in the live-to-dead load (L/D) ratio until it reaches 1; thereafter, the shape of the relationship will depend on the statistics of the resistance as well as on the magnitude of ϕ. For a small ϕ and VR, β will keep increasing with an increase in the L/D ratio from 1 until 3, albeit at a lesser rate. For L/D > 3, the relationship between the critical β and applied load is just about constant. This finding is also true for load combinations involving snow and wind. Application of the method is illustrated by a practical example involving the shear strength of a corrugated web steel beam.

Investigations on the fatigue loading of thin-walled and resource-efficient UHPFRC segmental bridges

Many reinforced concrete and prestressed concrete bridges are defective or can no longer withstand the increased traffic loads for a sufficiently long time. In the long term, they will have to be replaced by new structures. In previous reinforced concrete and prestressed concrete bridges, fatigue loading (e.g. traffic, wind) is rarely a problem with regard to the concrete, especially since the cyclic traffic loads are relatively low compared to the static dead loads due to a solid construction method. However, for reasons of sustainability and compliance with climate targets, future structures and bridges should be built in a resource-efficient and materials-compatible manner, while at the same time fast and durable. A target-oriented approach to this is segmental bridge construction with keyed dry joints made of ultra-high-performance fiber-reinforced concrete (UHPFRC). In these bridge structures the fatigue loads could become more relevant due to the slenderness of the thin-walled UHPFRC bridges superstructure and fatigue problems could occur. In order to investigate this in more detail, FE investigations on segmental box girder bridges under variation of the concrete strength (NSC, HSC and UHPFRC) were carried out, while optimising the cross-section dimensions. It was shown that due to the performance of UHPFRC and the associated cross-section optimisation, an exponential increase in the ratio of cyclic live loads to static dead loads and thus an exponential increase in fatigue loading occurs at thin-walled and resource-efficient UHPFRC segmental bridges compared to NSC and HSC bridges and that this can become relevant for the design of such bridges.

Optimal discharge pressure and performance characteristics of a transcritical CO2 heat pump system with a tri-partite gas cooler for combined space and water heating

The transcritical CO2 heat pump holds promise for achieving carbon neutrality in buildings, primarily due to its high energy efficiency in hot water heating. However, using it for space heating often leads to efficiency losses. A heat pump equipped with a tri-partite gas cooler can address this issue by providing both space heating and hot water while maintaining lower refrigerant temperatures at the gas cooler exit. Nonetheless, there is limited research on the characteristics of a CO2 heat pump system designed for simultaneous space and hot water production. This work fills this gap by analyzing the impacts of operational and system configuration, considering the variation of space heating to hot water production loads. A theoretical model is presented and verified with the experiments. Results show that under the specified conditions, the heat load ratio has minimal influence on the optimal discharge pressure. Increasing the water outlet temperature from 60 °C to 80 °C leads to a nearly 14% decrease in maximum COP, with a corresponding 12.2% increase in the optimal pressure. A 10 K rise in water inlet temperature results in approximately a 21% decline in maximum COP. Evaporation temperature has little impact on the optimal discharge pressure, while maximum COP increases by roughly 63% with a rise in evaporation temperature from -10 °C to 10 °C. Space heating water temperature notably affects the optimal discharge pressure. Integration of an IHX enhances system COP but has marginal impact on the optimal discharge pressure. These findings offer insights for designing and optimizing transcritical CO2 heat pumps for simultaneous space and water heating applications.

Cutting-edge insights: Crack growth rates in 9% Ni steel from room to cryogenic conditions influenced by crack closure and effective stress intensity factors

This study investigates the fatigue crack growth rate of 9% Ni steel at varying stress ratios under both room and cryogenic temperatures, attributing different growth rates to the phenomenon of crack closure. Traditional methods of studying crack closure, including the opening force, compliance ratio, and adjusted compliance ratio techniques, are assessed. Our results are juxtaposed with previous formulae for the opening force technique, leading to the introduction of a new formula that incorporates temperature effects by normalising the stress intensity factor with the yield strength at the respective test temperature. We highlight the adjusted compliance ratio (ACR) technique's limitations at cryogenic temperatures due to challenges in measuring notch open-crack compliance. As a solution, we present an innovative method that determines compliance using the effective elastic modulus. The mechanics behind the ACR technique are elucidated through the lens of the wedging mechanism. Our insights reveal that the ACR technique precisely calculates the effective stress intensity factor range (ΔKeff) under specific conditions. We address existing limitations by introducing a novel method, the triple compliance ratio (TCR) technique. A comparative analysis of effective stress intensity factors from all four techniques reveals the TCR technique's superior ability to correlate crack closure with crack growth. By eliminating the crack closure effect, the TCR technique offers a more accurate prediction of fatigue crack growth rate across diverse load ratios.