Loading Rate Research Articles

Rate effect of rocks: Insights from DEM modeling

Rocks are subjected to different loading rates at different construction stages and engineering applications. The strength of rock usually increases with loading rate. This rate dependency is one of the time-dependent behaviors of rock, whereby the micro-mechanisms are believed to be the subcritical crack growth due to stress corrosions. However, no evidence is provided yet. This study investigated rate effects of rocks through a novel implementation of Parallel-Bonded Stress Corrosion (PSC) model in Discrete Element Method (DEM). Long-term microparameters in PSC are first calibrated through creep test. Then, a series of uniaxial compressive strength, direct tensile strength, and triaxial compressive strength tests are performed, with strain rates ranging from 1×10−7/s to 1×10−3/s. Results show that the uniaxial compressive strength is highly dependent on strain rates which quantitatively matches with the experimental data. At lower strain rate, more subcritical cracks propagate due to longer stress-corrosion reaction time, resulting in a lower strength. Besides, strain rate also influences the failure patterns in post-peak, with single failure plane at lower strain rates and multiple failure planes at higher strain rates. Rate effects are also observed in direct tensile strength tests, with similar rate of increase in strength and a transition in cracking pattern, which align with the experimental data, indicating tension-induced subcritical cracking is the unified underlying micro-mechanism of rate effects for both cases. However, in triaxial compressive strength tests, rate effects become less obvious with increasing confining pressure, consistent with experimental findings, as subcritical crack growth is suppressed in shearing processes.

A comparative study of worm-sludge treatment reed bed planted with Phragmites australis and Arundo donax in the Mediterranean region.

Sludge treatment reed bed planted (STRB) with Phragmites australis (P.australis) and Arundo donax (A.donax) was assessed in the presence of Eisenia fetida under control condition during the dry season. Worm-planted units were fed with mixed sewage sludge (dry and volatile solids of 29.44g DS.L-1 and 24.23g VS.L-1). Sludge loading rates (SLR) of 50, 60, and 70kg DS m-2year-1 were examined to assess dewatering efficiency. Surface layers in units with P.australis and A.donax achieved DS of 80 and 81% at a loading rate of 50kg DS m-2year-1, while their subsurface DS were 41 and 25%, respectively. Units with A.donax experienced plant loss when subjected to SLR exceeding 60kg DS m-2year-1. More than 10cm of residual sludge accumulated on the top of units after a 2-month final rest. Evapotranspiration was greater in the unit with P.australis (5.23mmday-1) compared to the unit with A.donax (4.24mmday-1) while both were fed with 70kg DS m-2year-1. Water loss contributions from residual sludge layer, drained water, and evapotranspiration were 3, 46, and 51%, respectively. Units with P.australis indicated 20% higher water loss compared to units with A.donax. Although the drained water quality improved over time, it did not meet standard limits. The residual sludge layer contained macro and micronutrients, and heavy metals with a significant elemental order of N > Ca > P > S > mg > K (N:P:K = 31:8:1), Fe > Na > B > Mn > Mo and Zn > Cr > Cu > Pb > Ni > Cd. Overall, STRB could be a sustainable alternative technology to conventional sewage sludge management techniques.

Application of time-temperature superposition principle for cracking characterization of asphalt mixtures using semi-circular bend test

In recent decades, numerous laboratory tests have been developed to characterize the cracking performance of asphalt mixtures. Among these, the semi-circular bend (SCB)-based Illinois flexibility index test (I-FIT) (AASHTO T 393) has emerged as a favored method due to its straightforward specimen preparation and better sensitivity to mixture variables. However, the cracking susceptibility of asphalt mixtures is significantly influenced by temperature and loading rate, leading to a discrepancy in performance between standard test conditions and real-world scenarios. To address this challenge, this study explores the applicability of the time-temperature superposition principle (TTSP) for the SCB test. The study evaluates four mixtures incorporating reclaimed asphalt pavement (RAP) and/or reclaimed asphalt shingles (RAS) across various loading rates and temperature combinations. Findings suggest that TTSP can be applied to the SCB test without significantly impacting cracking performance indices such as flexibility index and post-peak slope. Furthermore, the study also demonstrates that TTSP can be applied in the crack propagation phase during the post-peak domain of the mixtures. The findings of the study will allow laboratories to develop more flexible testing plans without compromising the accuracy and reliability of performance parameters by adjusting the loading rate corresponding to the test temperature and vice versa. Consequently, this approach can potentially make a balanced mix design (BMD) practice more implementable.

Realization of a single-beam, detachable, cascaded 2D magneto-optical trap based modular cesium source

We present a detachable, cascaded modular cesium loading source based on a 2D magneto-optical trap (MOT). Our design utilizes only a single beam of mixed cooling and repumping light that is split evenly into five discrete trapping regions, each with horizontal and vertical beams. The pre-aligned, single-beam design makes our module suitable for miniaturization. The generated cold atomic beam serves to load a 3D MOT, whose loading rate we use to characterize the efficiency of our design. The effect of individual trapping regions relative to the differential tube and to each other on the loading rate has also been examined. Experimental results were compared with a numerical simulation. We are able to obtain an experimental loading rate of nearly 8×107atoms/s and a vapor density of about 3×1015atoms/m3 in our 2D MOT module.

One‐dimensional consolidation analysis of layered soil with exponential flow under continuous drainage boundary

AbstractTo comprehensively consider the influence of boundary conditions, non‐Darcy flow, load forms, and soil stratification on soil consolidation, a one‐dimensional soil consolidation equation is established. By subdividing the soil layer and employing time discretization, the nonlinear consolidation equation is linearized, resulting in an analytical solution for layered soil foundation at any given time. Subsequently, an iterative approach for time solution is employed to obtain a semi‐analytical solution. The correctness of the solution is verified by comparison with solutions based on Darcy's flow and the semi‐analytical method under traditional drainage boundary conditions. Subsequently, the influence of interface parameters, loading conditions, flow index, and other factors on consolidation characteristics is analyzed. The results indicate that higher interface parameter values for continuous drainage boundaries correspond to faster average consolidation rates for stratified soil foundations, while these parameters have little effect on the time required for complete consolidation of the soil layers. Improved boundary drainage performance amplifies the influence of exponential flow on pore water pressure and average consolidation degree. Conversely, poor boundary drainage performance diminishes the impact of exponential flow on soil consolidation, rendering it negligible. Moreover, faster loading rates accentuate the influence of the flow index on the average consolidation degree defined by pore pressure.

Optimization study of a high-proportion of solar tower aided coal-fired power generation system integrated with thermal energy storage

Solar aided coal-fired power generation technologies have proven to be effective in reducing fossil fuel consumption and greenhouse gas emission. In this research, a high-proportion solar tower aided coal-fired power generation system integrated with thermal energy storage system is proposed. According to the constraint conditions, the integration scheme with the highest solar coupling capacity is obtained, and its thermodynamic, economic and environmental performances are researched. The results indicate that the solar coupling capacity that can be accommodated by the 660 MW coal-fired unit after parameter optimization is 339.532 MWth. As the load rate decreases, the power generated from solar and solar to electricity efficiency gradually decreases while the proportion of power from solar increases. The proportion of power from solar reaches a maximum of 24.28 % at 50 % load rate. The effects of different thermal energy storage hours on the levelized cost of electricity are investigated, and the results show that the lowest levelized cost of electricity is only 41.62 $/MWh in the high-level direct normal irradiance area. The new system can reduce about 272,921 tons of CO2 emissions in a year at 100 % load rate. This study contributes to further promoting the development of a high-proportion solar aided coal-fired power generation system and realizing the low-carbon transition of coal-fired power generation industry.

Strength characteristics of different stress spaces of red sandstone under loading and unloading tests

Red sandstone tests were conducted on the rock mechanics test system to clarify the strength and failure characteristics of red sandstone under triaxial loading and different unloading confining pressure rates. Strength change rules of the red sandstone in various stress spaces were analyzed. Results show that a large initial confining pressure indicates a long yield section and large axial strain. A small unloading confining pressure rate indicates a long yield section and large axial strain at failure under the identical initial confining pressure. The confining pressure reduction increases with the unloading confining pressure rate increasing when the red sandstone fails. The stress path of unloading confining pressure weakens the red sandstone cohesion and strengthens its internal friction angle. The general octahedral shear stress formula for judging whether the red sandstone fails under loading and different unloading rates was acquired on the basis of the octahedral shear stress characteristics of the red sandstone. In addition, a 3D empirical criterion for evaluating the red sandstone strength was constructed through the deviator plane function of Eekelen and the strength envelope curve on the meridian plane. A great initial confining pressure indicates serious internal damage of the red sandstone at failure under the identical unloading rate of confining pressure. A low unloading rate of confining pressure indicates internal serious damage of the red sandstone at failure when the initial confining pressure is the same. The analysis of macroscopic failure characteristics revealed that the stress path significantly influences the failure mechanism of the red sandstone. The results are instructive for determining the stability of underground engineering of the red sandstone.

A robust polyaniline hydrogel electrode enables superior rate capability at ultrahigh mass loadings

Simultaneously achieving high mass loading and superior rate capability in electrodes is challenging due to their often mutually constrained nature, especially for pseudocapacitors for high-power density applications. Here, we report a robust porous polyaniline hydrogel (PPH) prepared using a facile ice-templated in situ polymerization approach. Owing to the conductive, robust, and porous nanostructures suitable for ultrafast electron and ion transport, the self-supporting pure polyaniline hydrogel electrode exhibits superior areal capacitance without sacrificing rate capability and gravimetric capacitance at an ultrahigh mass loading and notable current density. It achieves a high areal capacitance (15.2 F·cm−2 at 500 mA·cm−2) and excellent rate capability (~92.7% retention from 20 to 500 mA·cm−2) with an ultrahigh mass loading of 43.2 mg cm−2. Our polyaniline hydrogel highlights the potential of designing porous nanostructures to boost the performance of electrode materials and inspires the development of other ultrafast pseudocapacitive electrodes with ultrahigh loadings and fast charge/discharge capabilities.

Study on dynamic mechanical properties and microscopic damage mechanisms of granite after dynamic triaxial compression and thermal treatment

As underground mining operations gradually extend deeper, the conditions for orebody occurrence become increasingly complex, and various geological disasters occur frequently. Rock masses are prone to different degrees and types of damage, making it impractical to continue using intact rock as a reference. To study the dynamic mechanical properties of damaged rock under actual conditions, this study subjected granite samples to impact and high-temperature damage. Detailed observations were made of the samples' surface morphology and microstructure before and after damage, and the patterns of damage changes were investigated. Subsequently, uniaxial compression tests at different loading rates were conducted on the damaged samples. By calculating the loading rate effect sensitivity, it was found that as the damage increased, the rate effect gradually diminished. In addition, this study also summarized the influence of damage and loading rate on the macroscopic failure characteristics of the samples. The novelty of this study lies in focusing on damaged rock, which more closely resembles the actual rock conditions encountered in most underground mining operations today. This research can provide a reference for stability assessment and safe construction in deep mining rock engineering and offers important insights into the feasibility of non-explosive extraction of damaged rock.

Reconsidering Museums’ Climate and Seasonal Adjustment for Vulnerable Artifacts

ABSTRACT The paper provides new experimental evidence for vulnerable artifacts on the dependence of failure strain on the loading rate corresponding to typical environmental loads lasting between hours and months. Animal glue-based ground was chosen for this study as an easily available, hygroscopic and brittle material as well as due to its abundance in collections and its relevance when discussing the risk of mechanical damage to objects. Gesso specimens were tested using dynamic mechanical analysis and tensile testing at different frequencies, under a variety of loading rates and temperatures. The time-temperature superposition principle was used to predict the material response to slow deformations (lasting hours to months) that are otherwise inaccessible on laboratory timescales. The results demonstrate that brittle materials such as animal glue-based grounds do not benefit from longer cycles of applied loads as failure strain is not time-dependent within the investigated timescale.

Safety and reactogenicity of a controlled human infection model of sand fly-transmitted cutaneous leishmaniasis.

The leishmaniases are globally important parasitic diseases for which no human vaccines are currently available. To facilitate vaccine development, we conducted an open-label observational study to establish a controlled human infection model (CHIM) of sand fly-transmitted cutaneous leishmaniasis (CL) caused by Leishmania major. Between 24 January and 12 August 2022, we exposed 14 participants to L. major-infected Phlebotomus duboscqi. The primary objective was to demonstrate effectiveness of lesion development (take rate) and safety (absence of CL lesion at 12 months). Secondary and exploratory objectives included rate of lesion development, parasite load and analysis of local immune responses by immunohistology and spatial transcriptomics. Lesion development was terminated by therapeutic biopsy (between days 14 and 42 after bite) in ten participants with clinically compatible lesions, one of which was not confirmed by parasite detection. We estimated an overall take rate for CL development of 64% (9/14). Two of ten participants had one and one of ten participants had two lesion recurrences 4-8 months after biopsy that were treated successfully with cryotherapy. No severe or serious adverse events were recorded, but as expected, scarring due to a combination of CL and the biopsy procedure was evident. All participants were lesion free at >12-month follow-up. We provide the first comprehensive map of immune cell distribution and cytokine/chemokine expression in human CL lesions, revealing discrete immune niches. This CHIM offers opportunities for vaccine candidate selection based on human efficacy data and for a greater understanding of immune-mediated pathology. ClinicalTrials.gov identifier: NCT04512742 .

Synergizing sugarcane waste valorization: Optimization of two-stage anaerobic co-digestion for enhanced methane recovery and organic matter removal

Multiple strategies have been used in anaerobic digestion of effluents aiming to enhance the efficiency of the methane (CH4) recovery process, where co-digestion and the two-stage process emerge as prominent methods. In this context, this study aimed at evaluating the co-digestion of sugarcane vinasse and molasse in a two-stage process using anaerobic fluidized bed reactors (AFBR), verifying the effect of increasing the organic loading rate (OLR) (5–22.5 kg COD.m−3.d−1) and temperature in the second stage methanogenic reactor. Regarding the two-stage process, sugarcane vinasse and molasses fermentation demonstrated the maximum energy potential (E.P) of 57.08 kJ.d−1 (7.5 g COD.L−1). Regarding the methanogenic sequential reactors, organic matter removal reached high values (up to 84.5 % in a thermophilic sequential reactor (TSR); up to 84.5 % in a mesophilic sequential reactor (MSR)). The highest CH4 yield (MY) of 306.77 ± 38.84 mL CH4.g−1 COD rem was observed in MSR (9 kg COD.m−3.d−1). Meanwhile, the maximum value of MPR (3.8 ± 0.5 L CH4.L−1.d−1) was observed in TSR (21 kg COD.m−3.d−1). Regarding the Archaea domain, a predominance of hydrogenotrophic microorganisms could be identified, in which the genera Methanobacterium and Methanothermobacter were the most abundant in MSR and TSR, respectively. This study demonstrates that anaerobic digestion of sugarcane vinasse and molasses enhances anaerobic treatment using two-stage AFBRs. It not only produces CH4 but also generates hydrogen and high-value products through an acidogenic reactor. This research marks a significant advancement in managing sugarcane processing by-products, offering promising approaches to maximize biogas production and improve pollutant removal efficiency.

Biomechanics of step-off drop landings are affected by limb dominance and lead limb in task initiation

ABSTRACT This study examines the effects of limb dominance and lead limb in task initiation on the kinetics and kinematics of step-off drop landings. Nineteen male participants performed drop landings led by the dominant and non-dominant limbs at 45-cm and 60-cm drop heights. Ground reaction force (GRF) and lower body kinematic data were collected. Between-limb time differences at the initial ground contact were calculated to indicate temporal asymmetry. Statistical Parametric Mapping (SPM) was applied for waveform analysis while two-way repeated measures ANOVA was used for discrete parameters. SPM results revealed greater GRF and lesser ankle dorsiflexion in the lead limb compared to the trail limb in 3 out of 4 landing conditions. The dominant limb displayed a greater forefoot loading rate (45 cm: p=.009, η p 2 = 0.438; 60 cm: p=.035, η p 2 = 0.225) and greater ankle joint quasi-stiffness (45 cm: p < .001, η p 2 = 0.360; 60 cm: p < .001, η p 2 = 0.597) than the non-dominant limb. Not all 380 trials were lead-limb first landings, with a smaller between-limb time difference (p=.009, d = 0.60) at 60 cm (4.1 ± 2.3 ms) than 45 cm (5.6 ± 2.7 ms). In conclusion, the step-off drop landing is not an ideal protocol for examining bilateral asymmetry in lower limb biomechanics due to potential biases introduced by limb dominance and the step-off limb.

Electroactive biofilters outperform inert biofilters for treating surfactant-polluted wastewater by means of selecting a low-growth yield microbial community

Electrobioremediation is one of the most innovative disciplines for treating organic pollutants and it is based on the ability of electroactive bacteria to exchange electrons with electroconductive materials. Electroactive biofilters have been demonstrated to be efficient for treating urban wastewater with a low footprint; however, their application can be expanded for treating industrial wastewater containing significant concentrations (2.4 %vol) of commercial surfactants (containing lauryl sulfate, lauryl ether sulfate, cocamydopropyl betaine, and dodecylbenzene sulfonate, among others). Our electroactive biofilter outperformed a conventional inert biofilter made of gravel for all tested conditions, reaching removal rates as high as 4.5 kg COD/m3bed·day and withstood Organic Loading Rates as high as 9 Kg COD/m3·d without significantly affecting removal efficiency. The biomass accumulation reduced available bed volume in the electroactive biofilter just by 39 %, while the gravel biofilter decreased by 80 %. Regarding microbial communities, anaerobic and electroactive bacteria represented a substantial proportion of the total population in the electroactive biofilter. Pseudomonas was the dominant genus, while Cupriavidus, Shewanella, Citrobacter, Desulfovibrio, and Arcobacter were potential electroactive strains found in relevant proportions. The microbial community’s composition might be the key to understanding how high removal rates can coexist with limited biomass production, making electroactive biofilters a promising strategy to overcome classical biofilter limitations.

Intensified partial nitrification and microbiome response in a membrane pulsing-aerated biofilm reactor

Membrane aerated biofilm reactor (MABR) has been developed as an energy-saving process for nitrogen removal in municipal sewage treatment, even in high ammonia wastewater. However, the impact of aeration pattern on biofilm microbiome assemblage and nitrification is not well understood. In this study, MABR and membrane pulsing-aerated biofilm reactor (MpABR) were established for partial nitrification under high ammonium loadings. The MABR and MpABR exhibited a 95 % nitrite accumulation rate (NAR), with over 60 % ammonium removal and nitrite conversion achieved after the start-up phase. The MABR and MpABR gradually adapted to the substantial increase in ammonium loading (350 mg NH4+-N·L-1), resulting in stable and high NAR (96 %), ammonium removal efficiency (70 %), and nitrite conversion efficiency (67 %). Orthogonal experiments revealed that ammonium loading rate (ALR) was the primary factor regulating nitrite conversion and oxygen levels. A moderate ALR was preferable to achieve ideal partial nitrification and energy saving. Furthermore, the integrated MpABR-anaerobic ammonium oxidation (Anammox) maintained high total nitrogen (TN) removal (> 90 %) under high ALR conditions. Microbiome analysis revealed that nitrifiers (Nitrosomonas) and denitrifiers (Stenotrophomonas and Arenimonas) alternately dominated the biofilms at different stages. These findings highlight the potential for achieving efficient partial nitrification effects using a MpABR. The excellent TN removal performance of the MpABR-Anammox suggests its wide applicability in energy-efficient wastewater treatment.

Integration of mixotrophic denitrification and anammox in Thiothrix-hydroxyapatite coupled particles treating municipal wastewater against low temperature and organic load shocks

Sulfur-driven autotrophic denitrification coupled with anammox (SPDA) is a promising process for autotrophic nitrogen removal, but autotrophic microorganisms are challenging to retain in wastewater treatment units. In this study, a single-stage mixotrophic denitrification coupled with anammox (MDA) process was established in an up-flow anaerobic sludge bed reactor with Thiothrix-hydroxyapatite coupled particles. The advancement of the sludge granulation process effectively strengthened the resistance of the MDA system to environmental stresses, and the SPDA-dominated nitrogen removal process achieved a total nitrogen removal efficiency of 88.6 %, a nitrogen removal rate of 0.432 KgN/m3/d at temperatures as low as 12.8 °C and an organic loading rate of 0.63 KgCOD/m3/d. Interestingly, the ecological niche integration of sulfur oxidizing bacteria (SOB), anammox bacteria and heterotrophic denitrifying bacteria in the granular sludge was observed during long-term operation. The FISH-CLSM results revealed the spatial distribution of functional microorganisms in the granular sludge and the potential pollutant transformation mechanism. The aggressive growth of SOB dominated by Thiothrix constructed a biological wall at the periphery of the granules, which ensured their priority for nitrate acquisition, supplied nitrite to the internal anammox bacteria, and acted as an important barrier against the shock of organic loads. Overall, this study presents a novel granulation approach for the biological treatment of sulfur-containing wastewater, highlighting the efficacy of functional integration within Thiothrix-hydroxyapatite coupled particles as an effective strategy to resist environmental stress.

Immobilized Burkholderia cepacia Lipase and lts Application in Selective Enrichment of EPA by Hydrolysis of Fish Oil

Eicosapentaenoic acid (EPA), an orally active Omega-3 long-chain polyunsaturated fatty acid, has attracted much attention for its medical and healthcare value. Due to a large amount of polyunsaturated fatty acids (PUFA) including docosahexanoic acid (DHA) in fish oil, the highly specific enrichment of EPA from fish oil is difficult to achieve. In our study, we conducted immobilization studies on Burkholderia cepacia lipase (BCL) and its application in the selective enrichment of EPA in fish oil. BCL was immobilized on resin LX201A by covalent crosslinking, and immobilization conditions including glutaraldehyde concentration, pH, time were optimized. The optimal immobilization conditions were 0.5% glutaraldehyde, 4 hr, and pH 8.0. The loading rate of BCL reached to 93.5%, and its activity was up to 68263 U/g under the optimal immobilization conditions. After hydrolysis reaction of fish oil for 15h catalyzed by immobilized BCL, EPA content showed a more increase by 33.2%, while a slight increase by 0.78% in DHA content. Moreover, after recycling use for 10 times, the catalytic efficiency of immobilized BCL remained at 93.0%. These indicated that immobilized BCL possessed good selectivity, reusability and stability, providing great application potential in EPA selective enrichment in fish oil industry.

Effects of 16weeks of plyometric training on knee biomechanics during the landing phase in athletes.

This study investigated the effects of plyometric training on lower-limb muscle strength and knee biomechanical characteristics during the landing phase. Twenty-four male subjects were recruited for this study with a randomised controlled design. They were randomly divided into a plyometric training group and a traditional training group and underwent training for 16weeks. Each subject was evaluated every 8weeks for knee and hip isokinetic muscle strength as well as knee kinematics and kinetics during landing. The results indicated significant group and time interaction effects for knee extension strength (F=74.942 and p=0.001), hip extension strength (F=99.763 and p=0.000) and hip flexion strength (F=182.922 and p=0.000). For landing kinematics, there were significant group main effects for knee flexion angle range (F=4.429 and p=0.047), significant time main effects for valgus angle (F=6.502 and p=0.011) and significant group and time interaction effects for internal rotation angle range (F=5.475 and p=0.008). The group main effect for maximum knee flexion angle was significant (F=7.534 and p=0.012), and the group and time interaction effect for maximum internal rotation angle was significant (F=15.737 and p=0.001). For landing kinetics, the group main effect of the loading rate was significant (F=4.576 and p=0.044). Significant group and time interaction effects were observed for knee extension moment at the moment of maximum vertical ground reaction force (F=5.095 and p=0.010) and for abduction moment (F=8.250 and p=0.001). These findings suggest that plyometric training leads to greater improvements in hip and knee muscle strength and beneficial changes in knee biomechanics during landing compared to traditional training.

Understanding the Mechanochemistry of Mechano-Radicals in Self-Growth Materials by Single-Molecule Force Spectroscopy.

Recent research on mechano-radicals has provided valuable insights into self-growth and adaptive responsive materials. Typically, mechanophores must remain inert in the absence of force but respond quickly to external tension before other linkages within the polymer network. Azo compounds exhibit promising combinations of mechanical stability and force-triggered reactivity, making them widely used as mechano-radicals in force-responsive materials. However, the activation conditions and behavior of azo compounds have yet to be quantitatively explored. In this study, we investigated the mechanical strength of three azo compounds using single-molecule force spectroscopy. Our results revealed that these compounds exhibit rupture forces ranging from ~500 to 1000 pN, at a loading rate of 3×104 pN s-1. Importantly, these mechanophores demonstrate distinct kinetic properties. Their unique mechanical attributes enable azo bond scission and free radical generation before causing major polymer backbone damage of entire material during polymer network deformation. This fundamental understanding of mechanophores holds significant promise for the development of self-growth materials and their related applications.

Experimental investigation of the effective parameters on the lead extrusion damper performance

Lead extrusion dampers (LED) are employed for seismic response control of various structures due to their advantages over other energy-dissipative devices. However, a reliable design algorithm and an optimization process are essential to ensure optimal performance within the host structural system. Thus, the influence of device parameters on the damper behavior must be clearly understood. In the first part of this comprehensive study, the effect of different parameters on the LED performance was experimentally investigated. To this end, 23 specimens with different prestressing levels, bulge-to-shaft diameter ratios, shaft-to-bulge transition zone geometries, and device length ratios were cyclically tested under varying displacement amplitudes, i.e., 5 mm, 10 mm, and 20 mm, and loading rates, 0.5 mm/s, 1.0 mm/s, and 2.0 mm/s. Subsequently, they were exposed to a ramp-type loading up to the amplified design displacement. After satisfactorily completing the experimental tests, the behavior of the LEDs was compared in terms of their hysteretic behavior, energy dissipation capacities, temperature change, and stable behavior. It was concluded that the most influential parameters on the LED behavior were the bulge-to-shaft diameter ratio and the prestressing level on the lead. In addition to its effects on improving the hysteretic behavior, having a smooth shaft-to-bulge transition zone geometry was essential to guarantee a stable damper behavior.