Repetitive Loading Research Articles

An Acta Orthopaedica educational article: Treatment of pediatric spondylolysis and spondylolisthesis.

Spondylolysis is defined as a defect or elongation in the pars interarticularis of the lumbar spine, either unilateral or bilateral. Growing children with bilateral spondylolysis may develop spondylolisthesis, i.e., forward slipping of the affected vertebra. The etiology of spondylolysis is regarded as a stress fracture due to repetitive loading associated with a genetic predisposition. Lumbar magnetic resonance imaging (MRI) shows an increased signal intensity before an actual fracture line develops. In low grade spondylolisthesis, two-thirds of children with acute pediatric spondylolysis will undergo bony union with early activity restriction. Health-related quality of life is improved in patients achieving bony union as compared with patients having non-union, of which one-fourth will additionally develop spondylolisthesis. In patients with high-grade spondylolisthesis, defined as a more than 50% forward slippage of the affected vertebra, spinal fusion is recommended to prevent further progression.

Concrete Block Paving Tested as Articulated Slabs

This paper describes the experimental evaluation of articulated slabs composed of concrete block paving laid and compacted within a steel frame. By testing the paving in isolation from the bedding sand, basecourse and other elements of a complete block pavement it proved feasible to study the load spreading and other structural characteristics of the pavers themselves. This provided insights into the structural behaviour of concrete block paving under load. Factors studied in the project included the effects of paver shape, laying pattern, joint width, spacer nibs and load repetition. Each of these factors was shown to significantly influence the structural capacity of the paving course. By analysing the paver performance as a quasi-elastic slab it was possible to quantify the behaviour of block paving in a form suitable for inclusion in mechanistic pavement design and analysis. Where appropriate these measures were compared with data obtained both from Accelerated Trafficking Tests and Falling Weight Deflection studies of full scale block pavements.

Characterising geomaterial shakedown and related deformation accumulation from cyclic triaxial tests

Permanent deformation accumulation in soils and unbound granular materials under repetitive loading leads to surface rutting in roads and deterioration of track geometry in railways, eventually requiring costly and disruptive maintenance. Cyclic or repeated load triaxial tests are a convenient test method to characterise the permanent deformation behaviour of different soils under high numbers of load repetitions and a large volume of data is available. Existing empirical functions either take no account of shakedown, leading to an over-prediction of deformations at a high number of load cycles, or those that do take account of shakedown contain a high number of regression parameters that make them difficult to use. A simple empirical function with only one input parameter is proposed to characterise the accumulation of permanent axial strain in cyclic triaxial tests on a wide range of geomaterials undergoing shakedown deformations. It is shown to give predictions of a similar accuracy to existing functions at low numbers of load cycles and increased accuracy at high numbers of load cycles. It is shown to be applicable to soils ranging from a high plasticity clay to a rail ballast, across a range of stress states, stress history and strain levels provided that ratcheting deformations do not occur. The single input parameter has a physical meaning and is related to the permanent deformation required to reach the shakedown condition. Since the proposed function predicts the slowing rate of deformation accumulation towards shakedown not covered by the commonly-used existing functions, it could lead to more economical designs of applications involving high numbers of load repetitions. Its broad application to both coarse granular materials and fine-grained soils should streamline the design of applications involving layers of both these material types without the need to change empirical function.

High-cycle constitutive model for traffic loading induced permanent deformation of coarse granular material incorporating particle breakage

Repetitive traffic loads lead to particle rearrangement and breakage in granular trackbeds and roadbeds, resulting in irreversible deformations that hinder normal operations. Current models for cyclic deformation primarily address rearrangement-induced densification but overlook breakage-induced degradation. Particle breakage disrupts inter-particle interlocking and creates finer debris, promoting volumetric contraction and weakening material stiffness. This study introduces a novel cyclic constitutive model for predicting plastic strain in coarse granular materials, emphasizing the role of particle breakage. The model extended from the existing cyclic densification model within the framework named “Shakedown Surface Model,” integrating breakage effects. In this model, shakedown thresholds, associated with material densification, are influenced by both plastic strain and breakage-induced loosening. Parameters for shearing contraction/dilation decrease with breakage, capturing breakage-induced contraction. Additionally, the model accounts for principal stress rotation from moving loads. Implemented via an implicit Euler-backward algorithm and Newton–Raphson iteration, the model was validated against cyclic triaxial and full-scale tests, demonstrating its accuracy in predicting the permanent deformation of granular materials under traffic loads.

Subregions of the Rotator Cuff Muscles Present Distinct Anatomy, Biomechanics, and Function.

Shoulder and elbow injuries are prevalent among baseball players, particularly pitchers, who experience repetitive eccentric loading of the shoulder, leading to muscle damage and increased injury risk. Nearly 40% of shoulder injuries in baseball occur in pitchers, with many facing low rates of return to sport. The rotator cuff (RC) muscles-supraspinatus (SSP), infraspinatus (ISP), subscapularis (SSC), and teres minor (TMin)-are crucial for shoulder stability, movement, and force generation, particularly in overhead sports. Each RC muscle comprises subregions with distinct biomechanical properties, such as strength, moment arm behavior, and activation patterns. These differences allow for a finely tuned balance between joint stability and mobility. For example, the superior subregion of the ISP significantly contributes to external rotation, a function critical in sports like baseball that require precision and power. During pitching, the SSP, ISP, and SSC stabilize the glenohumeral joint through high activation during explosive phases, such as stride, arm cocking, and arm acceleration. Understanding these functional subregional differences is vital for diagnosing and managing shoulder pathologies like RC tears. Despite advancements, clinicians face challenges in predicting re-injury risks and determining return-to-play readiness for athletes with shoulder injuries. Integrating insights into subregional biomechanics with patient care could enhance outcomes. Tailored interventions-whether surgical or rehabilitative-targeting specific subregions could improve recovery times, reduce re-injury risks, and enable more personalized treatment plans. Such approaches are especially beneficial for athletes, older individuals, and those prone to RC injuries, promoting better long-term shoulder health and performance. The present work aims to highlight some of the research on these subregions and their differences, providing insights to enhance treatment approaches for shoulder injuries.

Seismic performance of CBF’s single steel angle brace under several variable amplitude loadings

Abstract Constructing seismic seismic-resistant structures is essential to be carried out in earthquake-hazard areas. A concentrically Braced Frame System (CBF) is an earthquake-resistant structure that relies on its brace to withstand seismic loading. Seismic loading is a series of loading histories composed of high (HA) and low-amplitude (LA) loading. When this loading hits the CBF system, it will perform various values of displacement. So far, many studies have been conducted to reveal seismic performance in CBF. However, studies on CBF’s response due to the variable displacement amplitude as the representation of the earthquake is still limited. This present study observed the seismic performance, i.e., strength, stiffness, and dissipated energy, of the CBF’s brace due to the variable amplitude loading. Variable amplitude loading is the loading history composed of high and low displacement amplitude levels. The brace was made of a single steel angle, L 40.40.4, and loaded with three different variable amplitude loading. Observing the dissipated energy as the main seismic performance of CBF discloses that the specimen which is loaded by the smaller number of cycles in a block amplitude reached the highest cumulative dissipated energy in the same applied displacement. This tendency is supposed to be presented since the specimen under a smaller number of loading repetitions in a block, leads to experiencing a small effect of fatigue and increases the strength in each cycle. Confirming the failure mode disclosed that all braces presented flexural and torsional buckling.

Structural analysis and fatigue prediction of harrow tines used in Canadian prairies

The Canadian prairies are renowned for their substantial agricultural contributions to the global food market. Harrow tines are indispensable in farming equipment, especially for soil preparation and weed control before planting crops. During operation, these tines are exposed to repetitive cyclic loading, which eventually causes fatigue failure. Commercially available three different harrow tines named 0.562HT, 0.625HT, and 0.500HT undergo an experimental fatigue evaluation and are validated through Finite Element Analysis (FEA). Fatigue life estimation for different deflections under various real-field deflections was carried out where 0.562HT showed groundbreaking life compared with others. The study results showed that the fatigue life is highly dependent on geometry, number of coils, pitch angle, leg length, and coil diameter. The 0.354HT model, developed to investigate the effect of wire diameter, closely resembles the 0.500HT model. The harrowing ability of the four different harrow tine models against identical deflections has been analyzed. Experimental fractured surfaces went through morphological investigation. This research has an impeccable impact on prairies’ agricultural acceleration by saving time and mitigating unpredictable fatigue failure often faced by farmers. Even the observed failure phenomena can serve as motivation to develop more reliable and durable harrow tines, which could increase agricultural efficiency.

From Tissue to System: What Constitutes an Appropriate Response to Loading?

Optimal loading involves the prescription of an exercise stimulus that promotes positive tissue adaptation, restoring function in patients undergoing rehabilitation and improving performance in healthy athletes. Implicit in optimal loading is the need to monitor the response to load, but what constitutes a normal response to loading? And does it differ among tissues (e.g., muscle, tendon, bone, cartilage) and systems? In this paper, we discuss the "normal" tissue response to loading schema and demonstrate the complex interaction among training intensity, volume, and frequency, as well as the impact of these training variables on the recovery of specific tissues and systems. Although the response to training stress follows a predictable time course, the recovery of individual tissues to training load (defined herein as the readiness to receive a similar training stimulus without deleterious local and/or systemic effects) varies markedly, with as little as 30min (e.g., cartilage reformation after walking and running) or 72h or longer (e.g., eccentric exercise-induced muscle damage) required between loading sessions of similar magnitude. Hyperhydrated and reactive tendons that have undergone high stretch-shorten cycle activity benefit from a 48-h refractory period before receiving a similar training dose. In contrast, bone cells desensitize quickly to repetitive loading, with almost all mechanosensitivity lost after as few as 20 loading cycles. To optimize loading, an additional dose (≤ 60 loading cycles) of bone-centric exercise (e.g., plyometrics) can be performed following a 4-8h refractory period. Low-stress (i.e., predominantly aerobic) activity can be repeated following a short (≤ 24h) refractory period, while greater recovery is needed (≥ 72h) between repeated doses of high stress (i.e., predominantly anaerobic) activity. The response of specific tissues and systems to training load is complex; at any time, it is possible that practitioners may be optimally loading one tissue or system while suboptimally loading another. The consideration of recovery timeframes of different tissues and systems allows practitioners to determine the "normal" response to load. Importantly, we encourage practitioners to interpret training within an athlete monitoring framework that considers external and internal load, athlete-reported responses, and objective markers, to contextualize load-response data.

Self-Healing and Mechanical Behaviour of Fibre-Reinforced Ultra-High-Performance Concrete Incorporating Superabsorbent Polymer Under Repeated and Sustained Loadings

This study investigated the mechanical responses and self-healing capability of incorporating superabsorbent polymer (SAP) particles in Fibre-Reinforced Ultra-High-Performance Concrete (UHPC) mixes under repetitive flexural and sustained tensile loadings. UHPC with SAP addition of 0.3% and 0.4% of the binder ratio were studied along with a control UHPC mix. The methodology included investigating the mechanical properties of these mixes under ambient, water, and 100% of relative humidity (RH) curing conditions. In addition, the mechanical performance of ambient-, water-, and 100% RH-cured prismatic specimens (100 mm × 100 mm × 500 mm) under repeated load was studied under the same curing conditions. Prismatic specimens (75 mm × 75 mm × 500 mm) were kept under cure conditions of wet and dry cycles with applied tensile load for 28 days for the sustained tensile load. The results showed that incorporating SAP into UHPC enhances the elastic modulus, flexural strength, and tensile strength. Also, mixes with SAP have exhibited compressive strength above 120 MPa after 90 days. Furthermore, the load recovery of the prisms under repetitive flexural load and prisms under sustained tensile loading demonstrated the self-healing efficiency of SAP incorporated into the UHPC mixes higher than the control mix specimens.

Fatigue performance and failure mechanism of ductile iron pipes with socket joints under traffic loads

Urban water supply pipelines experience repetitive traffic loads during their operational lifespan, potentially leading to fatigue failure. However, existing research focuses primarily on the static or dynamic mechanical responses of pipes, with limited studies on the fatigue performance of pipes. This study investigates the fatigue performance and failure mechanism of DN200 ductile iron (DI) pipes with socket joints under traffic loads and water pressure through bending fatigue tests. First, the mechanical responses of pipe joints under traffic loads derived from statistical data on highway traffic loads, soil pressure, and self-weight are calculated using ABAQUS to give the fatigue test load amplitude. Subsequently, tests are conducted on three DN200 DI pipes under a water pressure of 0.2 MPa: one for a monotonic test and two for fatigue tests under extra car and bus loads, respectively. The fatigue life of pipes under various traffic load combinations is analyzed using cumulative damage theory. Moreover, the relationship between fatigue load amplitude and number of cycles for DN200 DI pipes are obtained on the basis of the test data. Results show that the maximum rotation angle of joint is an important indicator of failure. Finally, a theoretical method for calculating the joint angle is proposed on the basis of geometric dimensions. A good agreement between the test and theoretical results is observed. Thus, the proposed method can obtain the fatigue performance of joints effectively.

Expression of myostatin and folistatin as a response to high-load strength training to counteract the loss of muscle mass in heart failure with preserved ejection fraction

Abstract Background and Purpose Muscle loss is a common complication in patients with heart failure (HF) associated with a significant increase in morbidity and mortality. Myokines (muscle proteins) play a crucial role in the pathophysiology of the disease; in particular, an imbalance in myostatin and follistatin has been reported. Although strength training (ST) within a cardiac rehabilitation (CR) program can modulate the expression of these myokines, its effect in patients with HF with preserved ejection fraction (HFpEF) is unknown. We hypothesize that in this population, ST with high load and low repetitions can mitigate muscle cachexia with better myiokine overexpression in this population. Our objective is to evaluate the impact of a CR program with emphasis on high-load, low-repetition ST on the regulation of these muscle proteins, muscle gain and cardiorespiratory fitness (CRFit) in patients with HFpEF. Methods Quasi-experimental study of a CR program (24 sessions of 90 minutes, 3 times a week, for 8 weeks), with the following structure: warm-up (10 minutes), 30-minute ST of high loads (>85% maximum repetition, 1MR) with low repetitions (3-5) and rest times between sets of 2 minutes; then 30 minutes of aerobic resistance training at moderate intensity (60-80% of maximum heart rate) and finally breathing exercises and cool-down (10 minutes). Myokines were determined by immunoassays. Muscular strength was determined by 1MR in biceps, triceps, lateral deltoid, quadriceps, hamstrings, gastrocnemius and soleus. For CRFit, maximum oxygen consumption (VO2) was measured and six-minute walk test protocol was also performed. Pre and post-intervention comparison was made using paired t test, Pearson's correlation was used in data analysis and a value of p<0.05 was considered significant. Results 59 patients were admitted, of which 8 of them left due to decompensation. Of the remaining 51 (62.7% male), the mean age was 66±8 years, all of them with HFpEF (M:55±2.4% vs W:54±2.1%; p=0.743). The other diagnoses in the study population were myocardial revascularization (52.94%), angioplasty (29.41%), valve replacement (11.6%), arterial hypertension (60%) and obesity (35%). After CR program it was observerd an improvement in VO2 (from 9.95±2.6 to 13.32±1.7; p=0.022) and meters traveled (243±41 to 349±14; p=0.002), and a decrease in myostatin levels (3337.1±69.2 to 2448.0±70.6; p=0.001) and elevation of follistatin (2167.4±96.9 to 3231.6±67.7; p=0.001). We found a strong positive correlation between follistatin levels and muscle percentage (r=0.8947 Pearson, graph1) and a strong negative correlation with myostatin and muscle percentage (r= -0.8034 Pearson, graph2). Conclusion A phase II CR program with a ST component based on high loads and low repetitions improved muscle strength and mass, FitCR and distance traveled in patients with HFpEF, without modify hemodynamic function. Follistatin levels increased by 49.09% and myostatin levels decreased by 26.65%.

Fatigue Behavior of H-Section Piles under Lateral Loads in Cohesive Soil

Most structures supporting solar panels are found on thin-walled metal piles partially driven into the ground, optimizing costs and construction time. These pile foundations are subjected to repetitive lateral loads from various external forces, such as wind, which can compromise the integrity of the pile-soil system. Given that the expected operational lifespan of photovoltaic solar plants is generally 20–30 years, predicting their service life under fatigue loads is crucial. This research analyzes the response of H-section piles to lateral fatigue loads in cohesive rigid soils through four field tests, subjected to load cycles of 55%, 72%, and 77% of the static failure load, corresponding to maximum loads of 25 kN, 32 kN, and 35 kN, respectively. Additionally, the effect of load cycles on the degradation of pile-soil adhesion is studied through two pull-out tests following cyclic tests. This study reveals that soil fatigue does not occur under repetitive loads and that soil stiffness remains constant once the cycles causing soil compaction have been overcome. Nevertheless, the accumulated plastic deflection of the soil increases steadily once soil compaction occurs due to cyclic loading. The implications of these results on the fatigue life of photovoltaic solar panel foundations are discussed.

Stress fracture of bone under physiological multiaxial cyclic loading: Activity-based predictive models

While it is known that excessive accumulation of fatigue damage from daily activities contributes to fracture, a model of bone failure under physiologically relevant multiaxial cyclic loading needs to be developed in order to develop effective management strategies for stress or fatigue fractures. The role of strain-induced damage from repetitive loading is a strong candidate for such a model, as cycles of mechanical loading leading to failure can be measured directly. However, this approach has been limited by the restrictions of uniaxial loading models, which often overestimates the fatigue life of bone and suggests that bone will only break well beyond the realistic limits of exercise. To address this gap and develop a physiologically relevant model, our study leverages the power of four commonly used engineering failure criteria as a model for multiaxial loading using a cohort of human tibiae from cadaveric donors (age range 21–85 years old). Four failure criteria (Von Mises, Tsai-Wu, Findley critical plane, and maximum shear strain) were found to be effective in vitro models of tibial fracture when age groups of donors were combined (r2 > 0.84) and stratified (younger: 21–52-years-old versus older: 57–85-years-old) (r2 > 0.83) (p < 0.001). Each failure criterion displayed distinctly lower fatigue curves for the older age group. The maximum shear strain model was used to determine the efficacy of this approach to predict fatigue fractures in humans using published in vivo data from human volunteers. Consistent with in vivo observations in general population, the model demonstrated failure at 5000 to 200,000 loading cycles depending on activities such as jumping, sprinting, and walking, with a 3-fold reduction of fatigue life in older donors. These findings dramatically improve estimates of fatigue life under repetitive loading and demonstrate how age-related changes in bone significantly increase its propensity for fatigue-induced fractures.

Temperature Effects on Traffic Load-Induced Accumulating Strains in Flexible Pavement Structures

AbstractRutting is a major distress mode in flexible pavements, results from the repetitive loading caused by traffic movement. Pavement deformation consists of both recoverable (elastic) and unrecoverable (plastic) components. The continuous movement of vehicles contributes to the overall deformation in the flexible pavement system, involving all pavement components. In regions with hot climates or in the hot summer season, rutting tends to be more prominent due to the substantial reduction in the viscosity of the asphalt binder. This decrease in viscosity, which is inversely linked to rutting, occurs as temperatures rise, leading to a heightened susceptibility of the Hot Mix Asphalt (HMA) blend to rut formation. However, according to studies, a significant amount of permanent deformation takes place in the unbound layers beneath the asphalt course, it is therefore essential to prioritize attention on these layers. Temperature exerts besides viscosity a substantial impact on asphalt stiffness, leading to the transfer of higher vertical deviatoric stresses to the unbound layers beneath the asphalt course (base, subbase, subgrade). This research presents a study integrating the High Cycle Accumulation (HCA) model into a laminar model to determine permanent deformations in the unbound granular layer of flexible pavements and taking into account the temperature dependent stiffness of asphalt. Rutting depths at the end of the design lifetime were computed, accounting for seasonal stiffness variations. It was shown that the softer asphalt behavior significantly increases the development of ruts in the underlaying soil layers. The findings were compared with results obtained from mean annual temperature and the typical equivalent asphalt stiffness utilized in fatigue tests. Additionally, an analysis was conducted to assess whether the timing of road implementation influences settlements throughout the design lifetime. The results suggest that the sequence of seasons is most relevant during the first year of service, showing a distinct effect at that time. However, with a higher number of axle passes, the initial differences fade away, and the curves start to merge.

Experimental insights into the seismic behaviour of flanged URM walls

Considerable attention has been given to understanding and modelling the seismic response of unreinforced masonry piers with rectangular cross-sections. However, the seismic performance of load-bearing masonry walls with flanges, commonly found in actual building configurations, remains less explored. This study investigates the behaviour of flanged walls through cyclic quasi-static tests on four full-scale C-shaped specimens comprising two primary seismic-resistant walls (webs) interconnected by a single flange. The construction of the specimens varied: two were built using standard solid calcium-silicate bricks with general-purpose mortar, while the other two utilised large-sized calcium-silicate blocks with tongue-and-groove interlocks and a thin layer of cement-based adhesive mortar. All specimens were subjected to cyclic horizontal loading parallel to the webs under consistent overburden load and double-fixed boundary conditions. The primary variable in testing the two walls of each type was the number of cyclic loading repetitions. This paper initially describes the key characteristics of the wall specimens, including geometry, construction details, and mechanical properties. Subsequently, it details the instrumentation plan and test protocol, and summarises the major observations from the tests, illustrating damage evolution and hysteretic force-displacement response. The results highlight the effect of the flange on initial stiffness and lateral force resistance, as well as the influence of block type and loading repetitions on failure mode, displacement capacity, and energy dissipation. Additionally, the study demonstrates the impact of floor slab uplift due to in-plane rocking of the webs on the top boundary conditions and the out-of-plane stability of the flange.

Alterations in magnitude and spatial distribution of erector spinae muscle activity in cyclists with a recent history of low back pain.

While cycling offers several health benefits, repetitive loading and maintenance of static postures for prolonged periods expose cyclists to low back pain (LBP). Despite high LBP prevalence in cyclists, underlying pathomechanics and specific lumbar region muscle activation patterns during cycling are unclear. Here, we compared lumbar erector spinae (ES) muscles activation and spatial distribution activity in cyclists with and without recent LBP history. Ten cyclists with recent LBP history (LBPG; Oswestry Disability Index score ~ 17.8%) and 11 healthy cyclists (CG) were recruited. After assessing the Functional Threshold Power (FTP), participants underwent an incremental cycling test with 4 × 3min steps at 70%, 80%, 90%, and 100% of their FTP. High-density surface electromyography (HDsEMG) signals were recorded from both lumbar ES using two 64-channel grids. Information about ES activation levels (root-mean-square, RMS), degree of homogeneity (entropy), and cranio-caudal displacement of muscle activity (Y-axis coordinate of the barycenter of RMS maps) was extracted from each grid separately and then grand-averaged across both grids. Repeated-measure 2-way ANOVAs showed a significant intensity by group interaction for RMS amplitude (p = 0.003), entropy (p = 0.038), and Y-bar displacement (p = 0.033). LBPG increased RMS amplitude between 70-100% (+ 19%, p = 0.010) and 80-100% FTP (+ 21%, p = 0.004) and decreased entropy between 70-100% FTP (-8.4%, p = 0.003) and 80-100% FTP (-8.5%, p = 0.002). Between-group differences emerged only at 100% FTP (+ 9.6%, p = 0.049) for RMS amplitude. Our findings suggest that cyclists with recent LBP history exhibit higher ES muscles activation and less homogeneous activity compared to healthy controls, suggesting potential inefficient muscle recruitment strategy. HEC-DSB/09-2023.

Effect of internal pressure on the flexural fatigue behaviour of trenchless internal replacement pipe systems

Internal replacement pipe (IRP) systems are a novel trenchless technique that is gaining interest in the rehabilitation of damaged legacy pipelines distributing natural gas. Performance evaluation of IRP systems under repetitive loads transmitted from vehicular traffic is essential to ensure their optimal and safe design. This study conducted numerical simulations to examine the impact of internal pressure on the bending fatigue behaviour of IRP systems that are fully bonded to legacy gas pipes with circumferential discontinuities. Other design parameters include the thickness and modulus of elasticity of IRP and the level of transmitted traffic load. The findings indicate that the operating internal pressure has a greater impact on the longitudinal stresses than the circumferential stresses of IRP when subjected to cyclic bending. The level of internal pressure changes the failure behaviour of IRP under fatigue. Based on the results obtained from extensive parametric simulations, mathematical expressions were formulated to predict the fatigue life of the IRP systems. Contour plots were generated to represent fatigue life response for different combinations of internal pressure levels and transmitted traffic loads.

Enhanced in-situ measurement and evaluation methods for subgrade modulus utilizing falling weight deflectometer

Falling Weight Deflectometer (FWD) tests have gained increasing popularity in evaluating the stiffness modulus of pavement subgrade. This paper presents an enhanced method for in-situ testing and evaluation of subgrade modulus using FWD apparatus. The method comprises three components: 1) guidelines for conducting field FWD tests with appropriate loading magnitudes and repetitions; 2) selection of optimal deflection positions for modulus back-calculation; and 3) determination of the suitable depth of the semi-infinite rigid layer. This method was developed based on measurements and analysis of FWD data from five highway subgrade sites, covering various subgrade soil types and climatic conditions. The enhanced method helps to promote the robustness and accuracy of modulus back-calculation results. Furthermore, to validate the proposed method, the back-calculated modulus was compared with moduli obtained from the other two commonly used tests, named the Portable Seismic Pavement Analyzer (PSPA) modulus test and the triaxial modulus test. Comparison results indicate strong correlations between the modulus values obtained from the proposed method and those from the PSPA and triaxial modulus tests, affirming the practicality of the proposed method in determining subgrade stiffness modulus.

Multiple blast behavior of steel wire mesh reinforced geopolymer based high performance concrete (G‐HPC) slab: Experiment and numerical simulation

AbstractEngineering structures face the potential of encountering repetitive or multiple blast loads stemming from accidental explosions and terrorist attacks. However, current research in this field is still relatively limited, and further investigation is needed to understand the damage mechanisms of structures under multiple explosions. Therefore, this study explores the blast resistance of G‐HPC slabs reinforced with steel wire mesh (SWM) under multiple blast loads. The failure modes of the SWM‐reinforced G‐HPC slab were experimentally studied under two consecutive explosions (with explosive equivalents of 1.6 and 3.2 kg, both at a standoff distance of 0.4 m). The results revealed that, after two consecutive explosions, the slab exhibited bulging with minimal concrete spalling, showcasing overall integrity. Subsequently, a numerical model was established, followed by a comprehensive parameter analysis. The parameter analysis investigated the effects of SWM diameters and grid size, the arrangement of SWM, and the sequence of TNT equivalents on the performance of the slab under three consecutive blast loads. The findings revealed that increasing the SWM diameter or reducing the grid size significantly enhanced the blast resistance of the slab under three consecutive explosive loads. Strategically arranging the SWM in the tensile zone reduced damage and deflection. Furthermore, the sequence of TNT equivalents had a notable impact on the damage and energy absorption of the slab.

Pemanfaatan Limbah Serbuk Kayu dengan Zat Aditif Anti Stripping Agent Terhadap Uji Durabilitas AC-WC (Asphalt Concrete–Wearing Course)

The increasing number of vehicles each year in Indonesia causes excessive repetition of loads that occur on road pavements, as well as extreme weather changes resulting in damage to the pavement layer, especially at the level of durability, especially in the AC-WC layer. The use of sawdust waste in the AC-WC mixture has met the marshall test values/characteristics, but it is necessary to test its durability; a high durability value indicates that the road is more durable and resistant to weather and water. Therefore, it is necessary to improve the quality of road pavement by adding anti-stripping agent additives at levels of 0.3%, 0.4%, and 0.5% to the AC-WC mixture of 25% wood powder waste substitution in order to improve the properties of asphalt in increasing the coating of asphalt with aggregates in a wet state to produce stronger bonds to extend the life of the road. This study aims to determine the effect of adding anti-stripping agent additives in AC-WC mixtures with sawdust waste on durability tests. Experimental tests were conducted using the research method at the Civil Engineering Laboratory of Diponegoro University Vocational School Semarang. The study results obtained a durability value based on the calculation parameters of the Residual Strength Index (IKS) based on the General Specifications of Bina Marga 2018 (Rev 2), which shows the durability of AC-WC asphalt. The results of marshall testing obtained based on averages include VIM 4.11%, VMA 13.15%, VFA 77.33%, Stability 1893.73 Kg, Flow 2.17 mm and MQ 1070.03 kg/mm from 25% wood powder waste variation with anti-stripping agent additives 0.3%; 0.4%; 0.5% in AC-WC wear layer has met the General Specifications of Bina Marga 2018 (Rev 2). The average durability values of IKS with sequential soaking time are 24 hours 92.24%, 48 hours 88.87%, and 72 hours 80.08%.