Damage Rate Research Articles

Developing an Effective Push–Pull System for Managing Outbreaks of the Invasive Pest Bactrocera dorsalis (Diptera: Tephritidae) in Nephelium lappaceum Orchards

Outbreaks of the oriental fruit fly, Bactrocera dorsalis (Hendel), present significant challenges to global fruit production, necessitating effective control measures that minimize environmental risks and pesticide resistance. This study aimed to develop and evaluate the effectiveness of four distinct push–pull control strategies for managing B. dorsalis outbreaks in a Nephelium lappaceum orchard. These strategies involved the inclusion of low-concentration abamectin, spraying repellent with a drone or manually, using methyl eugenol (ME) or food bait and employing either two types of attractants and repellents or a single type. The findings indicated that incorporating the low-concentration abamectin into the push–pull system, utilizing ME as an attractant instead of food lures and manually applying abamectin and attractants were all effective in reducing the B. dorsalis population size and minimizing fruit damage. While increasing the diversity of repellents and attractants enhanced the long-term effectiveness of the system, it did not result in a significant decrease in B. dorsalis population size or fruit damage rate compared to using a single repellent or attractant. In conclusion, the push–pull strategy emerged as a viable method for managing B. dorsalis outbreaks, offering potential benefits in reducing environmental risks and pesticide resistance. However, the study underscored the importance of the context-specific construction of push–pull strategies to optimize their effectiveness in orchard settings.

Shear failure analysis of slip zone soil with different coarse particle shapes: Visualized shear test and PIV technology

Coarse particle shape in slip zone soil influences the mesoscopic structure of the soil, which in turn affects soil shear strength and failure behavior. In order to investigate the effect of particle shape on the shear characteristics of coarse–fine-grained mixed slip zone soil, three types of coarse particles (spheroidal, rounded, and angular) were selected for mixing and matching, and a total of 10 sets of medium-scale shear tests were designed for this paper. To quantify the shear deformation and failure process of slip zone soils, particle image velocimetry (PIV) technology and the hanging hammer method were used to obtain mesoscopic data of the soil (displacement vector data of soil particles and elevation data of the shear failure surface), which were used to calculate shear band thickness, shear dilatation, and roughness coefficient of the shear failure surface. The results indicate that coarse particle shape can considerably affect the macroscopic mechanical properties (internal friction angle and shear strength) and mesoscopic deformation characteristics (shear band thickness, shear dilatation, and shear surface morphology) of soils. Angular coarse particles have higher interlocking strength than spheroidal and rounded coarse particles, allowing angular coarse-grained slip zone soils to develop large shear band thickness and rough shear failure surfaces. In addition, mesoscopic damage analysis suggests that the damage rate of slip zone soils decreases with increasing coarse particle shape complexity. These findings enhance comprehension of the failure characteristics of soil-rock mixture slopes and serve as a good reference for the stability analysis of similar slopes.

Design and Ansys Finite Element Analysis of a Shaking-type Winter Jujube Harvesting and Collection Device

In order to effectively improve the efficiency of winter jujube picking and collection while ensuring a low damage rate, facilitating the quick collection of winter jujubes, a vibration-type lightweight winter jujube picking and collection device is proposed. It consists of a rope-stretched umbrella collection device, a retractable vibration-assisted picking claw, a toothed locking device, etc. Mainly driven by manpower to stretch the rope and rotate the umbrella rod with a torsion spring to expand the umbrella surface, the toothed locking device locks the inclined block to fix the umbrella surface and the vehicle for collecting winter jujubes. Additionally, a miniature motor is used to drive the picking claw to generate exciting force to assist in manual picking. UG modeling and Ansys dynamic simulation of the collection umbrella surface and winter jujube fruits are conducted, simulating the impact of winter jujubes through simulation software to determine the vibration range when the collection umbrella is working. The rationality of its design and its adaptability during operation are analyzed, obtaining average deformation and average stress.

Economic optimization of fresh logistics pick-up routing problems with time windows based on gray prediction

The rapid development of modern cold chain logistics technology has greatly expanded the sales market of agricultural products in rural areas. However, due to the uncertainty of agricultural product harvesting, relying on the experience values provided by farmers for vehicle scheduling can easily lead to low utilization of vehicle capacity during the pickup process and generate more transportation cost. Therefore, this article adopts a non-linear improved grey prediction method based on data transformation to estimate the pickup demand of fresh agricultural products, and then establishes a mathematical model that considers the fixed vehicle usage cost, the damage cost caused by non-linear fresh fruit and vegetable transportation damage and decay rate, the cooling cost generated by refrigerated transportation, and the time window penalty cost. In order to solve the model, a hybrid simulated annealing algorithm integrating genetic operators was designed to solve this problem. This hybrid algorithm combines local search strategies such as the selection operator without repeated strings and the crossover operator that preserves the best substring to improve the algorithm’s solving performance. Numerical experiments were conducted through a set of benchmark examples, and the results showed that the proposed algorithm can adapt to problem instances of different scales. In 50 customer examples, the difference between the algorithm and the standard value in this paper is 2.30%, which is 7.29% higher than C&S. Finally, the effectiveness of the grey prediction freight path optimization model was verified through a practical case simulation analysis, achieving a logistics cost savings of 9.73%.

Stem Defect Rates and Ice Storm Damage for Families of Pinus taeda from Coastal and Piedmont Provenances Planted on a North Carolina Piedmont Site

Abstract Twenty Pinus taeda L. families from both the Coastal Plain and Piedmont provenances in the southeastern United States were planted on an upper Piedmont site that experienced a severe ice storm at age 3 years. Storm damage and defect rates through age 11 years were compared with the seed transfer distance and the seed parents’ breeding values to develop prediction models for storm damage and rates of forking, stem break, and sawtimber potential. Warmer-source families had higher probability of limb or stem breaks and foliage injury from the storm. Taller trees were more likely to experience breaks and foliage injury, even after accounting for seed transfer distance. Trees with forks or fusiform rust (Cronartium quercuum f. sp. fusiforme) infection had a higher probability of breaks. Trees with limb breaks or foliage injury did not have reduced sawtimber potential, but broken stems reduced sawtimber potential. The storm did not cause immediate mortality, but trees with major limb breaks, stem breaks, or foliage injury were less likely to be alive at age 8 years. At age 11 years, families with the best combination of breeding values for forking, straightness, and rust resistance had a predicted 60% of stems having sawtimber potential, whereas families with the worst combination had 30%. Study Implications: Planting warmer-source Pinus taeda (loblolly pine) families farther north and inland may lead to greater growth but poses a risk of damage from cold temperatures and ice storms. Trees grown for solid-wood products must be relatively defect-free and require a longer rotation, whereas bioenergy and pulpwood can use smaller, defective trees. This analysis presents predictions of defect rates through age 11 years based on the seed source and breeding values using data from a planting in the upper Piedmont of North Carolina. Land managers can use these models to weigh the benefits and risks when choosing families for reforestation.

Apple mechanical damage mechanism and harvesting test platform design

Abstract Apple is easily damaged in the process of the mechanical harvesting, which reduces the fruit’s quality. It is of great significance to study the damage principle of apple in the transport process of picking platform. In this study, the apple compression test was carried out. The compression and drop process of the fruit was analyzed by the finite element analysis (FEA). The experimental platform of apple harvesting was designed, the conveying process of apple was analyzed. The results of compression finite element analysis showed that when the compression force is greater than 15.0 N, both radial compression and axial compression will be damaged. The results of drop finite element analysis showed that when the drop direction is axial, the maximum contact stress of the peel and kernel decreases with the increase of drop angle, the maximum contact stress of the pulp increases first and then decreases. When the drop direction is radial, the maximum contact stress between pulp and kernel decreases with the increase of drop angle, the maximum contact stress of the peel first decreases and then increases. The simulation results of the harvesting platform transportation showed that the damage rate of apples is less than 10 % when the sub-conveyor belt speed is 0.02 m–0.04 m/s. This study can provide theoretical guidance for the design of the harvesting test platform and the reduction of the damage of apples during transportation.

Experimental study of the mechanical properties and microscopic mechanism of carbonate rock subjected to high-temperature acid stimulation

To clarify the effect of acidification on the stress distribution around wells in deep carbonate reservoirs, it is necessary to study the changes in mechanical properties of carbonate rocks under different acid stimulation conditions. In this paper, a novel acid stimulation experiment is designed to investigate the mechanical properties of the carbonate rock through a self-built acid-rock reaction experimental system and triaxial rock mechanics apparatus. The changes in the core mechanical parameters with the acid stimulation time at different acid stimulation temperatures are obtained. Based on stress relaxation, the rheological properties of the core after acid stimulation are explored. The internal structural damage mechanism of the core after high-temperature acid stimulation is as analysed via by SEM. This research finds that the elastic modulus and compressive strength of the core exponentially decrease with increasing of acid stimulation time. The higher the acid stimulation temperature, the faster the core damage rate changes, and the earlier the damage amount tends to stabilize. The core has an obvious rheological mechanical property after acid stimulation. The stress relaxation amplitude exponentially increases with increasing strain during loading. Interestingly, when the acid stimulation temperature reaches 120 °C, a sudden stress drop occurs during stress relaxation. It is also found that the stress relaxation amplitude increases exponentially with increasing acid stimulation time under the same strain level. Moreover, a higher acid stimulation temperature results in greater stress relaxation under a constant acid stimulation time and strain. In addition, the core skeleton is destroyed through acid stimulation, and many complex damaged structures appear inside the core, which leads to a decrease in the core strength, which is the reason for the enhanced rheological characteristics of the rock after acid stimulation. These results can provide insights into the mechanical response mechanism of wellbore acidification.

Experimental and damage model study of layered shale under different moisture contents

To investigate the mechanical properties and damage evolution law of layered shale under varying moisture contents, we conducted triaxial compression experiments on rock samples with different bedding angles and moisture levels. This study analyzed the variations in mechanical properties of layered shale under different conditions, and established a predicted model for elastic modulus based on different bedding angles and moisture content. Additionally, the damage constitutive model of layered shale was improved. The study revealed that shale’s mechanical properties display anisotropy, which is influenced by the bedding angles and moisture contents. The elastic modulus of the rock increases with the rise of bedding angle, exhibiting a ‘U’-shaped change. Conversely, the mechanical properties of rocks deteriorate, and their brittleness weakens with the increase in moisture content. When the confining pressure increased, the overall mechanical properties of shale were enhanced, and the influence of bedding on shale was weakened, but the deteriorating effect of water on rocks was hardly affected. Based on the above experiments, a predicted model of equivalent elastic modulus of shale considering the coupling effect of bedding and different moisture contents was proposed, which could effectively predict the elastic modulus of layered shale with different moisture content under different confining pressures. Furthermore, based on the predicted model of elastic modulus, an improved damage constitutive model of layered shale under triaxial loading was established, and the damage accumulation trend of layered shale was obtained, which showed an “S”-shaped change with strain. Under the coupling effect of bedding and different moisture contents, the damage of shale was advanced, but the accumulation rate of damage slowed down. With the increase of confining pressure, the influence of bedding and moisture content on the damage characteristics of shale decreased, and the damage curves under different conditions gradually tended to isotropy. The developed damage constitutive model for layered shale under different moisture contents provides theoretical support for the study of reservoir fracturing and wellbore stability.

Loss-of-function variants affecting the STAGA complex component SUPT7L cause a developmental disorder with generalized lipodystrophy

Generalized lipodystrophy is a feature of various hereditary disorders, often leading to a progeroid appearance. In the present study we identified a missense and a frameshift variant in a compound heterozygous state in SUPT7L in a boy with intrauterine growth retardation, generalized lipodystrophy, and additional progeroid features. SUPT7L encodes a component of the transcriptional coactivator complex STAGA. By transcriptome sequencing, we showed the predicted missense variant to cause aberrant splicing, leading to exon truncation and thereby to a complete absence of SUPT7L in dermal fibroblasts. In addition, we found altered expression of genes encoding DNA repair pathway components. This pathway was further investigated and an increased rate of DNA damage was detected in proband-derived fibroblasts and genome-edited HeLa cells. Finally, we performed transient overexpression of wildtype SUPT7L in both cellular systems, which normalizes the number of DNA damage events. Our findings suggest SUPT7L as a novel disease gene and underline the link between genome instability and progeroid phenotypes.

Clinical and genetic characteristics of Chinese patients with Shwachman Diamond syndrome: a literature review of Chinese publication.

Shwachman Diamond syndrome (SDS) is a rare autosomal recessive genetic disorder and due to its complex and varied clinical manifestations, diagnosis is often delayed. The purpose of this study was to investigate the clinical manifestations and genetic characteristics of SDS in Chinese patients, in order to increase pediatricians' awareness of SDS and to allow early diagnosis. We conducted a search to identify patients presenting SBDS gene pathogenic variant in two Chinese academic databases. We analyzed and summarized the epidemiology, clinical features, gene pathogenic variants, and key points in the diagnosis and treatment of SDS. We reviewed the clinical data of 39 children with SDS from previously published articles. The interval from the onset of the first symptoms to diagnosis was very long for most of our patients. The age of presentation ranged from 1day to 10years (median: 3months). However, the age of diagnosis was significantly delayed, ranging from 1month to 14years (median: 14months). Hematological abnormalities were the most common presentation, 89.7% (35/39) at the beginning and 94.9% (37/39) at diagnosis of SDS. Diarrhea was the second most common clinical abnormality at the time of diagnosis. 59% (23/39) of patients had a typical history of persistent chronic diarrhea. Furthermore, hepatic enlargement or elevation of transaminase occurred in 15 cases (38.5%). 56.4% patients (22/39) had a short stature, and 17.9% (7/39) patients showed developmental delay. Additionally, twenty patients had compound heterozygous pathogenic variants of c.258 + 2T > C and c.183_ 184TA > CT. Children with SDS in China had high incidence rates of chronic diarrhea, cytopenia, short stature, and liver damage. Furthermore, SBDS c.258 + 2T > C and c.183_ 184TA > CT were the most common pathogenic variants in patients with SDS. The diagnosis of SDS can be delayed if the clinical phenotype is not recognized by the health care provider.

Investigation of the Seismic Performance of Historical Masonry Aqueducts with Eulerian-Lagrangian Coupled Analysis

ABSTRACT Throughout history, aqueducts have been built to exceed obstacles on the waterway while preserving the energy of water. Our priceless cultural heritage, aqueducts must be protected to be passed on to future generations. Filling the channel with water can increase earthquake resistance due to the damping effect of water. Investigating of fluid and structure interaction of aqueducts through numerical analysis is crucial to understand their behavior under seismic forces. The aqueducts, for which 3D finite element models were prepared, were analyzed using the combined Eulerian-Lagrangian approach, taking into account two main scenarios: with and without fluid-structure interaction. With this approach, it’s aimed to observe the damping effect of the fluid, the sloshing on its surface and possible water overflows. Using the CDP material model for masonry units, the analyzes were diversified with various ground motion records at different Peak Ground Acceleration values. The presence of water in the channel significantly reduced displacements, stresses and damage rates. In addition, it was seen that the spectral acceleration value of the earthquake record was more effective in causing damage rather than the PGA value. Graphics and contour diagrams are given to understand and compare the analysis results of aqueduct models under different conditions.

Study on stress–strain curve and damage evolution model of expanded perlite concrete under uniaxial compression

AbstractThis study investigates the influence of expanded perlite (EP) replacement rate and curing methods on the compressive strength of concrete at different ages through the uniaxial compression test. The stress–strain full curve model of concrete considering EP replacement rate is established, and a damage evolution model considering curing conditions, EP replacement rate and load effects is developed based on the damage theory. The results show that: (1) The lack of water in concrete curing will have a huge negative impact on its mechanical properties, and the internal curing effect of pre‐wet EP can effectively alleviate the phenomenon of incomplete hydration. (2) Under dry curing, the addition of EP will reduce the early compressive strength of concrete, while its internal curing effect can improve the compressive strength of concrete in the later stages. (3) The C & C model and the Guozhenhai model are used to construct the segmented model in the rising and falling sections, and the model parameter formula is deduced by the replacement rate. The model can fully describe the stress–strain relationship of expanded perlite concrete (EPC). (4) The damage evolution model of EPC shows an “S” shape growth curve. Dry curing and EP replacement can both reduce the development rate of damage, while the former has a more significant impact.

Evaluation of neutron radiation damage in the VVER-1200 reactor pressure vessel

In nuclear reactors, the structural materials of reactor pressure vessel (RPV) are damaged by the radiation that produced by fission reactions. Neutron irradiation damage is one of the most critical factors for the degradation of the reactor pressure vessel (RPV). A displacement per atom (dpa) is a standard measurement for calculating neutron-and gamma-induced radiation damage in materials. The aim of this paper was to evaluate the neutrons radiation damage in the reactor pressure vessel of VVER-1200. In this paper, neutron damage factors, including fast neutron fluxes above 1 MeV, above 0.5 MeV, above 0.1 MeV, the damage rate (dpa/s), and Integrated damage [DPA for one effective full power year (EFPY)] were investigated for VVER-1200/AES-2006 reactor pressure vessel (RPV). The calculations are performed by using NJOY code together with the MCNP6 code at beginning of Cycle (BOC). The cross section library used in present calculations is based on ENDF/B-VII.1 library (ENDF71x). The NJOY code was used for generating DPA cross sections in an ACE formatted file that suitable for using in the MCNP6 code. The MCNP6 code was used for simulating the VVER-1200 reactor core and to calculate neutron DPA rates. MCNP6 simulation of the VVER-1200 reactor core identified the area where the RPV neutron radiation is maximized. The integrated damage for a full effective year was evaluated to be 2.128E-04 DPA/EFPD for the VVER-1200 RPV.

Response of Ips bark beetles (Coleoptera: Curculionidae: Scolytinae) to prescribed fire in South Carolina

Ips bark beetles (Ips species; Coleoptera: Curculionidae: Scolytinae) play an important role in forest ecosystems by attacking injured, stressed, or dying pine (Pinus) trees. Management of Ips bark beetles has largely focused on prevention by maintaining tree health through silvicultural treatments including thinning to reduce basal area or prescribed fire. However, there is conflicting evidence of whether prescribed fire leads to increased bark beetle populations and, subsequently, increased tree mortality. Recent outbreaks of Ips bark beetles in the southeastern U.S. have caused renewed interest in the interactions between pine management and bark beetle populations. We monitored Ips populations following prescribed fire in intensively managed pine stands and quantified Ips damage. We captured over 361,000 Ips bark beetles with I. avulsus being the most abundant of the three species collected. While we found high variation among Ips populations across study sites and years, there was a significant increase in bark beetle populations after prescribed fire followed by a significant decline the next year. While Ips populations increased up to three-fold after prescribed burns, damage ratings in burned stands were no different than unburned stands which had significantly lower bark beetle populations. Unburned stands had higher basal area and a higher average tree damage rating, but the lowest number of Ips bark beetles. A total of 14,071 facultative (e.g., Monochamus = 9775) and obligate (e.g., Thanasimus dubius = 4296) predators were collected during the study across all sites and the ratio of predators:Ips also significantly increased following prescribed fire. These data suggest that while Ips are ubiquitous and abundant in pine forests being managed with prescribed fire, natural mechanisms such as predator activity mediate their overall damage and impact to southeastern pine stands.

Infrapatellar branch of the saphenous nerve lesion following tibial nailing: it is possible to avoid it?

Iatrogenic injury to the infrapatellar branches of saphenous nerve is a common complication following tibial nailing. This lesion seems to be directly related to the surgical approach adopted for nail insertion. The aim of the present study was to systematically review the current literature in order to assess the eventual superiority of one surgical approach for tibial nailing over the others in limiting the neurological impairment related to infrapatellar branch injury. The available literature was systematically screened searching papers dealing with iatrogenic injury to the infrapatellar branch of saphenous nerve after intramedullary tibial nailing. The terms "Saphenous" and "Infrapatellar branch" were used in combination with "intramedullary nailing" and "tibial fractures", supplying no limits regarding the publication year. Only publications in English were considered. Case reports, technical notes, instructional course, literature reviews, biomechanical and/ or in vitro studies were all excluded. Coleman methodological score was performed in all the retained articles. Four articles matched the inclusion criteria. There were one original article and three retrospective study. Hypoesthesia and a larger extension of the area of sensory-loss were more frequently observed after vertical incision approach in three out of four articles. A trend towards a lower rate of iatrogenic nerve damage using a transverse incision was found in the remaining one, without any statistical significance. In order to avoid infrapatellar nerve lesion, horizontal or oblique incisions or percutaneous approaches should be favored, although in some cases a longitudinal incision is required. Limited-extension incisions could minimize the risk and the incidence of this complication.

Prognostic value of N–terminal pro B–type natriuretic peptide and troponin I in children with dengue shock syndrome

Objective: To investigate the contribution of N-terminal pro B-type natriuretic peptide (NT-pro BNP) and troponin I to mortality in children with dengue shock syndrome. Methods: A longitudinal study was conducted on children with dengue shock syndrome in a hospital in southern Vietnam. Detailed clinical histories, physical examinations, and laboratory parameters, including NT-pro BNP and troponin I, were recorded. A comparison between survival and non-survival was carried out to identify factors influencing mortality. Results: A total of 107 patients with a median age of 9 years were included in the study. Among them, 63.6% (68/107) presented with compensated shock, 36.4% (39/107) had hypotensive shock, 23.4% (25/107) required mechanical ventilation, and 12.1% (13/107) died. The NT-pro BNP levels were 3.9 pmol/L (IQR: 1.9, 10.3) and 15.2 pmol/L (5.8, 46.3), while the median high sensitivity troponin I levels were 20 pg/L (6, 95) and 62 pg/L (12, 325) at the first and second measurements, respectively. The mortality group exhibited higher rates of hypotensive shock, prolonged shock, lactate levels, liver damage, NT-pro BNP, and troponin I levels. Hypotensive shock (OR 12.96, 95% Cl 2.70-62.30, P=0.004), prolonged shock (OR 39.40, 95% CI 6.68-232.70, P<0.001), AST > 1 000 IU/L (OR 9.50, 95% CI 2.63-34.34, P=0.041), and NT-pro BNP > 7 pmol/L (OR 44.40, 95% CI 5.44-362.20, P=0.001) were identified as predictive factors for mortality in dengue shock syndrome. Conclusions: The NT-pro BNP level could serve as a potential biomarker for predicting mortality in children with dengue shock syndrome.

RecurDyn-EDEM 耦合仿真优化：三段式薯土低损分离装置优化试验

Aiming at the potato soil separation device of potato harvester, which generally has the problem of potato high damage in potato-soil separation, a three-stage potato soil low-loss separation device was developed, and orthogonal experiments were designed with the help of RecurDyn-EDEM coupled simulation method. A field bench was built for verification tests. The test proved that: when the lift transport chain speed was 1.40 m/s, travel speed was 0.60 m/s, amplitude was 32.0 mm, the impurity rate was 1.49% and the average force on potato was 1.801 N. The potato damage rate was 2.7%, indicating that the design of the three-stage potato soil low-loss separator device worked well.

Dietary zinc deficiency increases damage rate and copy number of mitochondrial DNA in the mouse liver

Zinc is an essential trace element involved in many physiological processes, ranging from cellular growth and immune functions to enzymatic activity and gene expression. Inadequate dietary zinc levels can disrupt the functioning of numerous organs, including the liver. Given the pivotal role played by the liver, in-depth understanding of the mechanisms driving disorders in this organ caused by zinc deficiency is of great importance. In the present study, the effects of a four-week low-zinc diet on the integrity and copy number of mitochondrial DNA (mtDNA) in the liver was assessed using a mouse model. The research revealed a significantly elevated damage rate and an increased copy number of mtDNA in the livers of mice subjected to a low-zinc diet when compared to control animals. These findings indicate that a zinc deficiency, by promoting DNA damage in mitochondrial genomes, increases a potential risk of harmful mutations that could compromise ATP production in the liver. The rise in the mtDNA copy number suggests an initial compensatory response to the detrimental effects of the zinc deficiency, which is likely to diminish with a chronic insufficiency of this element. The study confirmed the significant role of mitochondria in the processes leading to liver dysfunction induced by a zinc deficiency. It showed additionally that mtDNA is a very sensitive indicator of the liver's condition that is responsive to environmental changes such as a micronutrient deficiency in the diet.

Cracking behaviour of concrete with superabsorbent polymer (SAP) under rolling fatigue load and temperature coupling

ABSTRACT To explore the long-term crack resistance of pavement concrete containing superabsorbent polymer (SAP), a fatigue test was designed with the consideration of rolling fatigue load and temperature coupling. The four-point fracture and acoustic emission tests were combined to evaluate the evolution of crack resistance. Additionally, the enhancement mechanism was revealed through scanning electron microscopy and mercury intrusion porosimetry experiments. The results indicate that the coupling effects of rolling fatigue load and temperature accelerate the deterioration of the fracture performance of concrete, particularly the freeze–thaw conditions. The concrete with SAP had greater fracture toughness, with improvements of 9.3%, 11.9%, and 58.1% under the coupling rolling fatigue loading and high temperatures, low temperatures, and freeze‒thaw cycles, respectively. The fracture process of concrete with SAP includes fluctuation, fatigue accumulation, and fatigue failure periods, and the SAP delays the arrival time of cumulative ring count and energy, significantly reducing the rate of concrete damage. More fibrous C-S-H and ettringite were generated at the interface microcracks in the concrete containing SAP, confirming the greater degree of hydration. Moreover, the SAP reduced the porosity and average pore size, which enabled the concrete to better resist the impact of rolling fatigue loading and adverse environmental temperatures.

Multi-axial computational model for simulating the seismic behavior of concrete columns including axial collapse

This paper describes a coupled multi-axial material model that can capture the interaction between axial/shear/flexure and simulate the lateral cyclic response of non-retrofitted and retrofitted concrete columns under seismic loads up to complete loss of lateral and axial strength. The new material model is intended for use within two-dimensional lumped-plasticity framework and implemented in the open-source simulation software OpenSees as CMACA2D. The material model was calibrated using a newly compiled database of 719 cyclic and monotonic pushover column tests and only requires the input of column geometric and material properties. It includes several capacity models to capture all the salient lateral and axial strength-degradations including flexure, shear, flexure-shear, splice, up to complete axial collapse. These capacity models for each axial/shear/flexure degree-of-freedom (DOF) depend on the boundary conditions and applied demands in its own and other DOFs and constantly change during the analysis so the governing strength-degradation mode is not known a priori of the analysis. The material model employs an energy dissipation term to define the cyclic behavior response and to adjust the strength damage rate observed in test data. Finally, the performance of the proposed computational tools is compared with results from shake table tests.