Yield Line Research Articles

Experimental study on the seismic behavior of all-steel buckling-restrained brace with constrained coupler

This study proposes a novel all-steel buckling-restrained brace (BRB), in which cross-shaped (or H-shaped) steel members and double steel tubes are employed for the core members and buckling-restraining members, respectively. The core members are equipped with a constrained coupler in the central region. The square outer tube, welded to one end of the bracing system, uses spacers to prevent buckling of the inner tube. The hexagonal inner tube is connected to a constrained coupler by welding, thereby preventing the buckling of the core members. The constraint system provides a quadruple restraint mechanism comprising the inner tube, outer tube, constrained coupler, and spacers. Global and local stability are analyzed based on Eulerian theory, the principle of virtual work, and yield line theory, respectively. Cyclic loading tests were performed on four test specimens of the proposed BRB and four traditional BRBs without constrained couplers. Comparative analysis, through cyclic loading tests, reveals that the proposed BRB exhibits a stable energy dissipation performance post-yielding under compression, outperforming the specimens without constrained couplers in terms of the equivalent viscous damping ratio, cumulative plastic deformation, and the compression-strength adjustment factor. Furthermore, the numerical model was constructed and validated using the test results. The effects of the core width-to-thickness ratio and the gap size between the core member and inner tube on hysteretic behaviors were investigated. The contributions of this study can provide a reference for the application of BRBs in the engineering of more complex high-rise buildings and mega-spatial structures.

Transgene effects vary among maize populations with implications for improving quantitative traits

AbstractThe goal of transgenesis in plant breeding is to make step‐change improvements in traits of interest. However, improving quantitative traits, such as yield in maize (Zea mays L.), with transgenes has been difficult. Traditionally, transgene testing is done on a few isogenic lines, and results are extrapolated to entire breeding populations. Testing on limited germplasm does not provide a robust estimate of a transgene's value. Incorporating transgenes directly into breeding populations could increase genetic variance and the rate of genetic gain. Here, we used a transgene that reduces ethylene as a case study and investigated event, transgene, family, and environment effects and their interactions. We also determined whether introduction of the transgene into a breeding population would result in transgenic lines being preferentially selected over nontransgenic lines for yield. We found significant variation in transgene effects across clustered environments and families for multiple traits including yield. In environmental Cluster 2, the transgenic lines yielded 0.4 Mg ha−1 more than nontransgenic lines in family KC22; yet, in family QY43, transgenic lines yielded 0.3 Mg ha−1 less. Similarly, within Cluster 4, the QY43 family had preferential selection of transgenic over nontransgenic lines, whereas in families YE41 and AY91, nontransgenic lines were selected more frequently. These results show the critical importance of evaluating transgenes across broad germplasm diversity to assess their general value to a program. Integrating transgenes, or using gene editing, directly in a breeding program can expand genetic variation for quantitative traits and potentially accelerate genetic gain.

Punching shear behavior of ultra-high-performance fiber-reinforced concrete and normal strength concrete composite flat slabs

This paper presents the results of tests on flat slabs with partial application of ultra-high-performance fiber-reinforced concrete (UHPFRC) mixtures to improve the punching shear capacity of slab-column connections. One normal strength concrete (NSC) slab and two UHPFRC slabs were tested as a reference for tests on 12 UHPFRC-NSC composite slabs with full depth UHPFRC in the center area of the NSC slab. The main test parameters were the steel fiber volume (0.8 % and 1.6 % volume fractions) and the dimensions of UHPFRC mixtures. The load-column displacement curves, crack patterns, slab rotations at failure, and failure loads are presented and discussed. The failure loads are compared with estimates obtained following the yield line analysis, design codes, and other theoretical models. Test results showed that the use of UHPFRC mixtures led to an increase in initial stiffness, punching shear strength, and deformation capacity, along with a change in the slab failure mode. The shear capacity of the slab improved proportionally to the increase in the dimension of the UHPFRC. These tests confirmed the effectiveness of the UHPFRC mixtures as an alternative to enhance the punching shear capacity for slab-column connections.

Exploitation of heterosis in chilli using genetic male sterile lines for red fruit yield with special reference to high rainfall conditions

High-quality red/dry chilli for spice, pharmaceutical and medicinal purposes is a major goal in chilli breeding. The male sterile lines have greater potential for the exploitation of heterosis in chilli to achieve this objective. Genetic male sterile lines with special traits like destalking and ability to withstand high rainfall were involved in heterosis breeding to identify hybrids for commercial and industrial purposes. Forty F1 hybrids were developed by crossing 4 diverse GMS lines with 10 testers using Line × Tester mating design to estimate heterosis, combing ability and gene action. The experiment involving 14 parents and 40 F1s, along with standard variety ‘CH-27’ was laid out in α-lattice square design in three replications during summer 2020 and 2021. The GMS lines MS 9-2 and MS 26-1 along with testers DPCh 10, VVG, DPCh 40 and Him Palam Mirch-2 showed significant GCA for marketable red/dry fruit yield and majority of their component traits. Ten F1 hybrids were identified with superiority for fruit yield based on mean performance, significant heterosis and SCA effects, providing an opportunity to utilize them in value-added products and dried spice purposes viz., MS 9-2 × HPM-2, MS 11-2 × DPCh 40, MS 9-2 × DPCh 40 and MS 9-2 × DPCh 101 with erect fruiting habit and that of MS 9-2 × DPCh 10, MS 26-1 × DPCh 10, MS 9-2 × PBC 535, MS 26-1 × VVG, MS 29-2 × DPCh 10 and MS 26-1 × DPCh 22- C with pendent fruits. The non-additive gene action was predominant in the expression of fruit yield, total red fruits/plant, oleoresin and capsanthin. A significant positive correlation among SCA, economic heterosis and per se performance is an indicative to identify superior hybrids. Multi-location testing of these hybrids shall pave way to exploit them commercially by making them available to the farmers.

Genetic variability, character association and path coefficient analysis in okra

A study was conducted to investigate the genetic architecture of different lines for fruit yield and its associated traits in okra. Fourteen parents, consisting of twelve lines and two testers, were crossed using a Line × Tester mating design in the spring-summer season of 2019-20 at Vegetable Research Farm, CCSHAU, Hisar. The resulting twenty-four hybrids were cultivated in a randomized block design with three replications during the rainy season of 2020-21. Fruit yield/hectare showed a significant range from 87.86 to 150.18 quintals with an average of 117.73 quintals. The phenotypic coefficient of variation ranged from 3.91% (test weight) to 20.23% (Number of branches per plant), slightly surpassing the genotypic coefficient of variation which ranged from 1.98% (test weight) to 12.15% (fruit yield) with high estimate of PCV for the number of branches per plant (20.23%) and a moderate estimate of both PCV and GCV for fruit yield (14.67%, 12.15%), number of fruits per plant (14.34%, 12.06%), respectively. This suggests that the traits studied were more influenced by genetic factors than environmental factors. High heritability coupled with high genetic advance as percentage of mean for traits such as number of fruits/plant (70.74%, 20.89%) and fruit yield/hectare (68.65%, 20.74%) suggested that additive genes play a major role in determining these traits respectively. This indicates that it is possible to select high-yielding genotypes by selecting parents with desirable traits. Fruit yield/hectare displayed positive and significant associations with most of the traits like number of fruits per plant (0.95) and plant height (0.36) at phenotypic levels. The number of fruits per plant, 1000 seeds test weight, fruit diameter, and number of branches per plant had the most significant positive effect on fruit yield. Ultimately, such analysis has the potential to assist breeders in formulating their selection strategies aimed at enhancing fruit yield.

Effect mechanism of low-velocity impact loading rate on the failure modes transition of steel-UHPC-steel composite plates

This study delved into the transition mechanism of loading rate on the failure mode transition in steel-ultra-high performance concrete-steel (SUHPCS) composite plates under concentrated low-velocity impact loads. A series of drop-weight tests elucidated that, as impact velocity escalated, the composite plate shifts from local punching failure, characterized by circumferential cracks, to overall flexural failure, marked by radial cracks resembling yield lines. Given the constraints in capturing strain data in drop-weight test, a 3D nonlinear structural analysis using Abaqus software was conducted. This numerical simulation method was validated by drop-weight test results in terms of crack patterns and impact force time histories. Moreover, structural dynamic punching and flexural loads at a specific loading rate were obtained with the assistance of the dynamic increase factor (DIF). Failure mode could be judged through comparison between the two critical loads. The discrepancy in strain sensitivity exhibited by steel plates and UHPC accounted for the transition in failure modes of the SUHPCS composite plates. DIFs for UHPC compressive strength and steel plate strength were lower than DIF for UHPC tensile strength, as these factors were around 1.5, 1.7 and 2.6, respectively. Parameter analysis showed that the critical transition impact velocity for a composite plate with a core thickness of 80 mm was 11 m/s, surpassing the 13 m/s threshold for a composite plate with a 100 mm-thick core. Moreover, changes in DIFs of UHPC and steel strengths were less than 2 % with various impact masses and the composite plate maintained the same failure mode.

Combining ability of quality protein maize (Zea mays L.) inbred lines for agronomic, yield and quality traits in temperate hilly regions of Kashmir, India

Combining ability of quality protein maize (Zea mays L.) inbred lines for agronomic, yield and quality traits in temperate hilly regions of Kashmir, India

Vertical diaphragms for moment connection of thin-walled CFT column to steel beam

A vertical diaphragm scheme is proposed to connect the concrete-filled thin-walled steel tube (thin-walled CFT) column and steel beam, as an alternative to horizontal diaphragm connections: dual vertical diaphragms are installed inside the steel tube, considering poor out-of-plane resistance of the thin tube wall. For verification of the moment connection, two experimental programs were carried out. In the first experiment, an ultimate tension test was conducted for flange-to-column connections, to identify the fundamental behavior of the proposed connection (i.e., strength, failure mode, and out-of-plane deformation). The design parameters, such as the thickness, number, and continuity of the vertical diaphragms, were considered. All the test specimens exceeded the design strengths based on a yield line model (i.e., the tensile capacity-to-demand ratios ranged Tu/TYL = 1.11–1.31), without early fracture of welded joints. In particular, at the design strengths, the tube out-of-plane deformations were more limited with the heavier diaphragms. In the second experiment, beam-to-column connections using prototype I-section steel were tested under cyclic flexure, to verify the joint flexural strength and rigidity as well as the seismic performance. The beam-to-column connections failed by the beam flexural mechanism, whereas damage was marginal at the joint wall (i.e., the flexural capacity-to-demand ratios ranged Mu/Mj = 0.87–1.09). Overall, the dual diaphragms were effective in achieving rigid (full-strength) connections with satisfactory plastic rotation of the beam. On the basis of the test results, design considerations were recommended for the vertical diaphragm connections.

Simplified Direct Strength Method for the design of cold-formed steel channels with circular web openings under two-flange loadings

Previous studies have put forward reduction factor equations to determine the web crippling strength of cold-formed steel (CFS) channels with circular web openings. However, these equations overlook vital parameters such as material yield strength, flange width, and fillet radius of CFS channels. Consequently, this paper introduces simplified Direct Strength Method (DSM) equations, which account for plastic loads (Py) and elastic buckling loads (Pcr), integrating the aforementioned crucial parameters. Eight unique yield line models were devised, considering two-flange loadings: interior-two-flange (ITF) and end-two-flange (ETF), as well as the positioning of circular web openings, to compute the yield line length for Py. Similarly, new Pcr equations were also proposed. The reliability of the proposed equations was evaluated using a dataset of 236 test results sourced from the literature. This assessment aims to demonstrate the suitability of the equations for incorporation into future revisions of international design codes.

Experimental investigation on the dynamic response of vent plate under methane-air mixtures explosion load

The dynamic response study of explosion venting components is of great significance for the assessment of explosion disasters and the determination of damage. Based on the self-developed rectangular explosion venting device, a series of experimental investigations on the dynamic response and failure mode of calcium silicate vent plates under the methane explosion loads induced by a detonator were conducted. The results show that the vent plate mainly exhibits brittleness and presents a plastic hinge failure mode under the blasting loads. When the gas concentration is closer to the stoichiometric concentration, P2 (the peak overpressure generated by the vent plate rupture) and its pressure rise rate dP2/dt are higher. Conversely, when the methane concentration is closer to the upper or lower limits of the explosion, the explosion load tends to be static, the yield line of the vent plate is shorter, and there are fewer fragments generated by the failure of the plate. The pressure-displacement curve and the correlation diagram of failure modes proposed provide a reference for predicting the failure mode of light and fragile explosion venting components.

Selection of Tropical Inbred Lines for Yield and Morpho-agronomical Traits in Maize (Zea mays L.)

Selection of Tropical Inbred Lines for Yield and Morpho-agronomical Traits in Maize (Zea mays L.)

Research on finite element simulation and full-scale-vehicle crash test of B750HL bridge barrier

How to raise the bridge barrier with a concrete base height of only 51 cm to SS level of protection is not yet studied. In order to effectively retrofit an existing concrete barrier design to meet new crash testing criteria, the structural dimensions and concrete strength of the existing bridge barrier were investigated, and finite element simulation analysis was carried out, and simulation suggested the existing barrier was insufficient. Based on the structural dimension design principles of bridge barriers, the existing structure of bridge barrier was designed after adding lightweight and high-strength B750HL material crossbeams and posts on top of the concrete base, and the bearing capacity of the bridge barrier was calculated based on the yield line theory. Then, a finite element simulation analysis model was established to study and analyze the blocking, guiding, and cushioning functions of the improved design of bridge barrier. Finally, full-scale-vehicle crash tests were conducted with the SS-level small car, bus, and tractor-van trailer for this bridge barrier design scheme. This paper is the world’s first to use B750HL steel as the material for the crossbeam and post of a bridge barrier with a concrete base height of only 51 cm. According to the research results, the B750HL bridge barrier, which was designed based on the calculation of structural dimension design and yield line theory, effectively reduces the increased constant load on the bridge deck caused by the extra crossbeams and posts. At the same time, it can reduce material costs and save engineering costs. After being verified by finite element simulation crash tests and full-scale-vehicle crash tests, the protective capacity of the B750HL bridge barrier was proven to meet the SS-level evaluation requirements of the Standard for Safety Performance Evaluation of Highway Barriers (JTG B05-01-2013). The research findings of this paper is that the finite element simulation crash tests can effectively simulate full-scale-vehicle crash test, and the finite element simulation crash tests is reliable. If the safety performance of the barrier in the finite element simulation crash tests meets the requirements, the probability of passing the full-scale-vehicle crash test is higher. Therefore, a design scheme is proposed for the B750HL bridge barrier to improve hybrid bridge barriers at a height of 51 cm or more based on various design methods.

Experimental investigation of flexural and punching behavior for plain PE-ECC slabs with different fiber volume fractions and span-depth ratios

Engineered Cementitious Composite (ECC) exhibits superior tensile ductility, shear capacity, and crack-control ability in comparison to traditional concrete and fiber reinforced concrete. These attributes render ECC a suitable candidate for addressing the brittle punching shear behavior commonly observed in reinforced concrete (RC) flat slabs. To verify the feasibility of using ECC for strengthening the punching shear capacity of concrete slabs, an investigation on the punching behavior of plain ECC slabs was conducted to ascertain their crack patterns, failure mode, strength and energy absorption capacity by means of experiments on twenty-seven 400 mm×400 mm square slabs. The plain ECC slabs were simply supported on a bespoke steel framework with eight supports, centrically loaded with a concentrated load. The fiber volume fraction (FVF) and span-depth ratio (SDR) are the two variables to be examined for their effects on the punching behavior of ECC slabs. Test results revealed that the incorporation of fibers significantly improved the load-bearing capacity, ductility and energy absorption capacity, while it altered the failure mechanism from brittle to ductile. The critical punching shear angles of all tested plain ECC slabs ranged from 40° to 50°. The ECC specimens possessing an FVF of 2 % exhibited markedly superior tensile capabilities compared to those with a 1 % FVF, as evidenced by direct tensile tests. Nevertheless, the ECC slabs with an FVF of 2 % did not demonstrate commensurate improvements in load-bearing capacity relative to their counterparts containing 1 % FVF. The span-depth ratio significantly impacted the failure mode of plain ECC slabs, yielding to punching shear failure at an SDR of 1, and to flexural failure at SDRs of 2 and 3. Moreover, an increase in the SDR value led to a reduction in both the initial cracking load and the ultimate load, concurrently increasing the associated deflection. In addition, a preliminary theoretical analysis was conducted to estimate the bearing capacity of plain ECC slabs. Flexural strength was estimated by yield line theory (YLT) and punching shear resistance was estimated by the model based on theory of plasticity in slab-column systems. The experimental and theoretical investigations could provide insights into the punching and flexural behavior of ECC slabs, laying a groundwork for the design and development of flat systems strengthened with ECC.

Yield line-based design of fibre reinforced concrete: assessment of suitability of material models

The present research is intended to address the adequacy of flexural toughness-based material models such as equivalent and residual flexural strength, and the deflection limits at which these parameters are estimated for design of fibre reinforced concrete (FRC), for various applications such as slabs-on-grade/pavements. The work is an experimental study using FRC concrete mixes with individual and hybrid combinations of hooked-end steel (SF) and macro polypropylene fibres (PF). The experimental investigation consisted of toughness testing unnotched and notched prisms and square slabs, prepared with a typical grade of concrete used for FRC pavement applications. To validate the material models, a comparison was made between the theoretical moment/load calculated based on material flexural toughness parameters and the actual moment obtained from slabs using actual yield line formed during testing. From the study it is observed that overall, both equivalent (from unnotched prism test) and residual (from notched prism test) flexural strength, are suitable for designing FRC slabs, however the equivalent strength parameter shows better correlation to the slab response. The results also indicate that the hybrid mixes of PF and SF, with a higher volume fraction of 0.6% Vf, shows a marginal increase in flexural performance, in comparison to the mixes with lower volume fraction but no or minimal synergy due to hybridisation.

Exploring population genetics for mutant mungbean [Vigna radiata (L.) R. Wilczek] lines: Insights from augmented block design

AbstractThe current study was initiated to assess mungbean [Vigna radiata (L.) R. Wilczek] mutant lines for yield and their attributes in the mutation generation third (M3) generation using an augmented block design. Note that 1200 mutated mungbean lines were selected from the γ‐irradiated (400–700 Gy) population and distributed into 21 blocks, along with three popular varieties (checks) replicated in each block. To evaluate mean performance, variance, and population genetics, the observations on days to flowering, days to maturity, plant height (cm), number of clusters per plant, number of pods per plant, pod length (cm), protein percentage, seed index, and seed yield (g) were measured and analyzed. All the lines under consideration showed highly significant variations for all the variables, except for days to flowering. Seventy‐nine mutant lines were found to have significantly better yield attributes than checks and are currently being evaluated under station trial. Skewness and kurtosis analysis unveiled the presence of gene interactions, offering opportunities for targeted improvement and efficacy of γ rays as a mutagen, facilitating the release of variability within the population. Future mungbean breeding programs will benefit from the successful isolation of mutant plants with yield‐enhancing traits, such as up to 20 clusters per plant, 71 pods per plant, 8.55 cm pod length, 26.69% protein content (5% higher than parent), and 29 gram seeds per plant. In early selection cycles without the need for replicated trials, this study demonstrated the effectiveness of the mutagen and augmented design in creating novel variations, evaluating and identifying superior genotypes with improved yield potential.

Punching shear tests and design of UHTCC-enhanced RC slab–column joints with shear reinforcements

Reinforced concrete (RC) flat-slab structures may experience progressive collapse, usually caused by the punching shear failure of slab–column joints. Existing research has shown that the use of shear reinforcements or ultra-high toughness cementitious composites (UHTCCs) in slab–column joints is efficient in improving their punching shear performance. In this study, shear reinforcement was introduced into UHTCC-enhanced RC slab–column joints. Specimens of UHTCC-enhanced slab–column joints were tested considering the effect of shear reinforcements. The cracking development process, bearing capacity and ductility were analysed. Yield line theory and critical shear crack theory were adopted to predict flexural and punching shear capacities, respectively. Finally, the failure patterns of the specimens were distinguished by comparing the predicted punching shear and flexural capacities, taking ductility coefficients into account. The theoretical and test results show the effect of shear reinforcement on the behaviour of UHTCC-enhanced joints. Significant improvements in the bearing capacity and ductility of the joints was achieved by applying shear reinforcement. The failure pattern of the joint varied from premature punching shear failure to flexural-triggered punching shear failure with the application of UHTCC, and this transformation was more pronounced with shear reinforcement applied into the UHTCC-enhanced joint.

Tensile behavior of novel column-to-column connection for modular steel construction using high-strength bolts

As an important aspect of the city upgrade plan, installing the elevators for existing multi-story residential buildings means a lot to the residents of the higher floors, especially for old people. To minimize the site disruption and overcome the space limitation of installation, the modular elevator shafts have been widely adopted. The external wall decoration panels are normally pre-installed on the elevator shaft frame elements in the workshop, which makes it difficult for the connection between upper and lower segments using the high-strength bolts due to very limited space for applying the pre-tension. A novel column-to-column connection is presented in this study, consisting of an end plate, web opening of column web and strengthening plate at each of the column end. The tensile behavior of the proposed connection is first investigated through an experiment. Subsequently, a detailed finite element model is built and verified using the test results, with which a parametric study is conducted with the main parameters considered. Finally, a simple analytical solution for predicting the design load of the proposed connection is developed employing the yield line theory. Comparisons with the finite element results indicate the high accuracy of the proposed solution. The presented connection is believed to be a good solution for the on-site connection between H-columns of highly assembled modular structures, not limited to the elevator shafts.

Yield Line Analysis of Two Way Reinforced Concrete Slab of Three-Sides Supported with Various Loading Conditions

Yield Line Analysis of Two Way Reinforced Concrete Slab of Three-Sides Supported with Various Loading Conditions

Combining ability and genetic distance analysis of mid altitude sub-humid agroecology adapted maize inbred lines for high grain yield

Understanding the combining ability effects, heterosis, and genetic relationships between parental lines would be helpful in the maize breeding program to develop high-yielding and genetically stable maize varieties for various contrasting environments. Hence, the objective of this study was to estimate combining ability effects, heterosis, genetic distance (GD) and associations for grain yield and other agronomic traits. Forty-five F1 diallel crosses, four commercial checks, and ten inbred lines were evaluated at Bako and Jima Agricultural Research Centers, Ethiopia. Significant differences were observed among environments, genotypes and genotype by environment interaction for grain yield and almost all studied agronomic traits. Combining ability analysis showed both additive and non-additive gene effects significantly controlled grain yield and all other studied traits. The preponderance of general combining ability (GCA) effects indicates the importance of additive gene action inheriting most agronomic traits. Lines L2, L7, and L9 were the best combiners for grain yield, whereas lines L3 and L4 had desirable GCA values to improve days to flowering and plant height. Among the top ten crosses, L6 × L9, L6 × L7 and L4 × L9 were good specific combiners and had 18.8 %, 17.2 % and 16.2 % grain yield advantage over the best check, BH546. These hybrids also had high mid and better-parent heterosis compared with other crosses. The associations of GD with mean of F1 and SCA effects were positive and highly significant for grain yield and some other traits. In contrast, correlations of GD with mid and better parent heterosis were non-significant for grain yield and most other traits. The results of this study are particularly useful for breeders who envisage combining conventional and molecular methods.

Mechanical performance of elliptical one-sided bolted joints for T-stub and hollow section members under tension

This paper presents experimental and numerical investigations on the tensile performance of the elliptical one-sided bolted joints in building applications. Two types of joints are examined including the T-stub joints and T-hollow joints, where T-stub joints are formed by two T-stubs connected together through elliptical one-sided bolts at their flanges; and T-hollow joints are formed by two T-stubs connected to a square hollow section (SHS) member with the help of the elliptical one-sided bolts. A group of T-stub joints with ordinary bolts is also comparatively studied. Similar failure modes were observed for either elliptical one-sided or ordinary bolted joints while the yield capacity for elliptical one-sided joints was 9% lower than that of ordinary bolted joints for the T-stub joints. Parametric studies are further carried out on the key parameters such as flange thickness of the T-stubs and wall thickness of the hollow section members in the T-stub and T-hollow joints. It is found that the joint stiffness and strength can be improved with the increase of flange thickness or wall thickness for T-stub and T-hollow joints. Analytical models based on the yield line mechanisms are then presented, providing mechanism-based understanding for such elliptical one-sided joints in structural assembly. Detailed finite element (FE) models were constructed with considerations of bolt pre-tensioning and contact behaviours such as those between T-stub flange and bolt head. The deformed configurations of specimens can be successfully described by the FE modelling and the differences on initial stiffness and yield capacity between experimental and FE results are within about 10%.