Stiffness Enhancement Research Articles

Energy dissipation enhancement of nonlinear viscous damping-integrated negative stiffness amplifying dampers

Energy dissipation enhancement of nonlinear viscous damping-integrated negative stiffness amplifying dampers

Perception and analysis of dynamic stiffness of cable-stayed bridges based on wave analysis

The vertical dynamic stiffness of long-span cable-stayed bridges under vehicle loading is a crucial concern due to their susceptibility to sustained vibrations with notable wave effects. This study investigates the dynamics stiffness perception and enhancement mechanisms of cable-stayed bridges based on fast wave analysis method, proposing wave-associated structural concepts (WSC) for designing stiffer cable-stayed bridges under traffic loading. Initially, the wave function characterizing cable-stayed bridge vibrations is introduced into the representation of the dynamic stiffness of cables and beams, and six WSC for enhancing structural dynamic stiffness are proposed. Subsequently, the fast establishment of the core module for wave function computation is achieved through modular construction of the wave propagation matrix. By employing wave decomposition to clarify the decoupling relationships among the wave components, a distributed algorithm is applied for efficient parallel solving of the wave function. Finally, the reliability and superiority of the proposed method are validated. Using wave analysis method, the stiffness enhancement mechanisms based on WSC and the criteria for implementing WSC in cable-stayed bridges are presented. The case study indicates that the structural dynamic stiffness is related to the wave characteristics which are influenced by both excitations and structural parameters. Enabling the rapid transmission of waves to the structural foundation promote uniform energy distribution and amplitude reduction of wave, thereby enhancing the dynamic stiffness. The beam section stiffness contributes to a dual-effect stiffness enhancement in cable-stayed bridges, effectively increasing the wave velocity. An alternative definition of structural dynamic stiffness is provided based on wave propagation.

Sustainable Multi-Cycle Physical Recycling of Expanded Polystyrene Waste for Direct Ink Write 3D Printing and Casting: Analysis of Mechanical Properties.

This work investigates the sustainable reuse of expanded polystyrene (EPS) waste through a multi-cycle physical recycling process involving dissolution in acetone and subsequent manufacturing via Direct Ink Write (DIW) 3D printing and casting. Morphology and mechanical properties were evaluated as a function of the manufacturing technique and number of dissolution cycles. Morphological analysis revealed that casted specimens better replicated the target geometry, while voids in 3D-printed specimens aligned with the printing direction due to rapid solvent evaporation. These voids contributed to slightly reduced stiffness in 3D-printed specimens compared to casted ones, particularly for transverse printing orientation. The defoaming process during dissolution significantly increased the density of the material, as well as removed low molecular weight additives like plasticizers, leading to a notable enhancement in stiffness. Successive dissolution cycles led to increased removal of plasticizers, enhancing stiffness up to 52 times (cast), 42 times (longitudinally printed), and 35 times (transversely printed) relative to as-received EPS waste. The glass transition temperature remained unchanged, confirming the preservation of polymer integrity. This work highlights the potential of EPS inks for sustainable, multi-cycle recycling, combining enhanced mechanical performance with the flexibility of 3D printing for complex, cost-effective designs, aligning with circular economy principles.

Experimental investigation into the lateral performance of post-tensioned steel-timber hybrid frame with tension-only braces

Low-damage timber structures provide a promising solution to build mass timber structures with both seismic safety and post-earthquake . The main objective of this research was to explore a technical solution of enhancing the lateral stiffness of post-tensioned steel-timber hybrid (PTSTH) frames without significantly compromising their self-centering capabilities. In the PTSTH frames studied, steel fixtures were installed at the beam-to-column joint zones. Each joint consisted of a steel fixture, a steel-timber column connection, and a steel-timber beam connection. The steel fixtures were connected to the timber column via the steel-timber column connection, providing a practical method for installing different types of braces. Post-tensioned steel tendons were used to connect the steel fixture to the timber beam, forming the steel-timber beam connection. Three 2/3 scaled PTSTH frame specimens underwent cyclic loading tests. The impact of tension-only braces on various system properties was studied and compared to an alternative solution involving additional damping and stiffness (ADAS) braces. The results showed that tension-only braces contributed to more than 70 % of the stiffness enhancement in the PTSTH frame compared to a post-tensioned timber frame with the same geometry. However, their contribution to energy dissipation was less than 50 %. Tension-only braces did not significantly hinder the self-centering performance of PTSTH frames, while ADAS braces did. Replacing glued-in rod (GIR) connections with screw connections affected the gap opening process in the steel-timber beam connection. Consequently, this change led to an increase of at least 25 % in residual deformation.

Axial compressive properties of GFRP-reinforced PVC-based glued wood-plastic composites column

Wood-plastic composites (WPCs) are environment-friendly materials, which are always used in decoration engineering and outdoor engineering. However, WPCs cannot be directly used as bearing structural members especially columns for their poor tensile and compressive properties and great creep under long-term loading. This study presented an innovative approach of using glass fiber reinforced polymer (GFRP) to reinforce PVC-based glued WPCs short columns. Three effective reinforcement methods were proposed: embedding GFRP bars, wrapping GFRP sheets around the outer surface, and GFRP bars and sheets compound reinforcement. Axial compression tests were conducted to evaluate the load-bearing capacity and deformability of the columns. The results showed that the outer GFRP sheets effectively inhibited the cracking of adhesive layers, leading to a remarkable enhancement in ductility and stiffness of the WPCs columns. Moreover, the ultimate bearing capacity of GFRP bars/sheets compound reinforced columns increased by over 140%. Finite element (FE) analysis was employed to investigate the influence of GFRP reinforcement methods, aiming to obtain the optimal design solution of WPCs columns. A theoretical formula was established to calculate the axial compressive capacity of GFRP-reinforced WPCs columns, and its accuracy was validated through experimental tests and FE modeling.

Geosynthetic-stabilized aggregate: quantitative modulus evaluation via Bender Element

Geosynthetics, mainly geogrids and geotextiles, are commonly used to mechanically stabilize unbound aggregate layers in paved road applications. They provide lateral restraint to aggregates to initially increase the layer modulus during construction and minimize its time-dependent decrease under vehicular traffic loading. Different types of geosynthetics may provide different improvement mechanisms and stiffness enhancement levels. Quantitative evaluation of various stabilization geosynthetics is presented herein to compare modulus improvement trends and help incorporate geosynthetic benefits into state-of-the-art mechanistic-empirical (M-E) pavement design procedures. Five geogrids (three extruded, one woven, and one welded) and two geotextiles (one woven and one nonwoven) were studied with a dense graded aggregate in laboratory triaxial testing. Geosynthetics were placed at specimen mid-height and three pairs of Bender Element (BE) sensors were placed at various heights above the geosynthetic to collect shear waves and quantify the degree of mechanical stabilization during resilient modulus testing. While resilient moduli did not distinguish effectiveness of different geosynthetics, shear wave measurements could clearly show local stiffness increases achieved with geosynthetic inclusions. Meanwhile, trends observed in shear modulus profiles at various distances from the geosynthetic, when compared to that of control specimen, properly established the modulus enhancement level achieved in mechanical stabilization with geosynthetics.

Real-time in-situ ultrasound monitoring of soft hydrogel 3D printing with subwavelength resolution

3D bioprinting has excellent potential in tissue engineering, regenerative medicine, and drug delivery systems due to the ability to fabricate intricate structures that are challenging to make with conventional manufacturing methods. However, the complexity of parametric combinations and lack of product quality control have restricted soft hydrogel bioprinting from practical applications. Here we show an in-situ ultrasound monitoring system that reveals the alginate-gelatin hydrogel’s additive manufacturing process. We use this technique to understand the parameters that influenced transient printing behaviors and material properties in approximately real-time. This unique monitoring process can facilitate the detection of minor errors/flaws during the printing. By analyzing the ultrasonic reflected signals in both time and frequency domains, transient printing information can be obtained from 3D printed soft hydrogels during the processes with a depth subwavelength resolution approaching 0.78λ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\lambda$$\\end{document}. This in-situ technique monitors the printing behaviors regarding the constructed film, interlayer bonding, transient effective elastic constant, layer-wise surface roughness (elastic or plastic), nozzle indentation/scratching, and gravitational spreading. The simulation-verified experimental methods monitored fully infilled printing and gridded pattern printing conditions. Furthermore, the proposed ultrasound system also experimentally monitored the post-crosslinking process of alginate-gelatin hydrogel in CaCl2 solution. The results can optimize crosslinking time by balancing the hydrogel’s stiffness enhancement and geometrical distortion.

Allowable stress rating compared to load and resistance factor rating for timber bridges with and without steel-beam retrofit

This paper presents the relevancy of the Allowable Stress Rating (ASR) and the Load and Resistance Factor Rating (LRFR) methods for timber bridges. Benchmark bridges constructed in the 1930′s are upgraded with hollow structural steel (HSS) beams and three-dimensional finite element models provide technical information that is necessary for examining their behavior and rating evaluations. Complying with published manuals, a total of 17 rating vehicles are considered across three categories (Design, Legal, and Permit) so as to generate the maximum responses of the bridges. The position of the vehicles dominates the deflection profiles of the unrepaired bridges. After installing the HSS beams, the live loads are redistributed and stiffness enhancement is noticed in the transverse direction of the bridges. The rating factors calculated with ASR exceed those with LRFR for the unrepaired bridges, regardless of vehicle configurations, and the level of disparity between these rating approaches increases when the bridges are repaired owing to differences in load factors. In terms of sensitivity to average daily truck traffic, the LRFR factors of the bridges under the Legal vehicles are more responsive than the factors subjected to other vehicle types. From a probability perspective, the compatibility of these rating methodologies varies contingent upon vehicle categories and the presence of the HSS beams. Practice guidelines are proposed to facilitate the conversion of rating factors between ASR and LRFR as a function of the present condition of constructed timber bridges.

Synthesis of Stearyl Alcohol/Polyethylene Glycol Hybrids as Water-Repellent Finishes for Cotton/Polyester Blended Fabric

Nowadays, developing and innovation of new finishing agents that are cost effective, efficient, durable, and safe for the consumer as well as the environment are greatly required by the textile manufactures. In that concern, new stearyl alcohol/polyethylene glycol (SA/PEG) hybrids were synthesized, characterized, and applied as textile finishes to impart cotton/polyester fabric with water repellency. Such hybrids were synthesized by reaction of SA with PEG of molecular weight 1000 or 4000 Da in the presence of ammonium persulfate (APS) as initiator. The optimum conditions of the synthesis reaction are: APS/PEG, 20%; PEG/SA, 15%; reaction temperature, 80 °C and reaction time, 45 min. The synthesized hybrids are self-water dispersible that form oil-in-water stable emulsions. The results indicated that treating cotton/polyester fabric with easy-care finishing formulation containing 60 g/L of dimethyloldihydroxyethylene urea as a cross-linker, and 60 g/L of any of such hybrids emulsions imparts the treated fabric with water repellency, softness, and stiffness properties. Moreover, increasing the PEG molecular weight from 1000 to 4000 Da leads to a reduction in extents of softness and contact angle along with an enhancement in stiffness of treated fabric. Furthermore, the prepared hybrids emulsions-treated fabric samples are durable up to five washing cycles. The FTIR analysis confirmed the chemical structure of the synthesized SA/PEG1000 hybrid. The transmission electron microscope (TEM) revealed that the particles size of SA/PEG4000 hybrid emulsion is in the range of 34–70 nm and reaches to 185 nm in case of the SA/PEG4000 hybrid emulsion. The surface of SA/PEG1000 hybrid emulsion-treated fabric was characterized via scanning electron microscope (SEM).

Impact of molecular architecture and draw ratio on enhancement of targeted mechanical properties of machine direction oriented polyethylene films produced after blown film extrusion

Conventional multi-material multi-layer flexible packaging offers excellent properties. However, it has recycling challenges, necessitating a shift to mono-material multi-layer flexible packaging for example all-polyethylene (PE) packaging which can be tailored through various synthesis and processing methods for different layers. In this work, we study how the key molecular properties (number-average molecular weight ( Mn), weight-average molecular weight ( M w), molecular weight distribution (MWD), comonomer content (short chain branching)) and machine direction orientation (MDO) process draw ratio (MDX) influence the final morphology and mechanical properties of MDO-PE films which are intended as the outer layer of mono-material all-polyethylene multi-layer flexible packaging. Five PE grades and various blends were extruded and blown into films. Selected blown films were machine direction oriented to obtain the final MDO-PE films. Furthermore, one selected PE blown film was processed at different MDO process draw ratios while keeping other process parameters constant. From the molecular properties point of view, the higher molecular weight fractions provide a higher possibility for uniform stretching whereas lower molecular weight fractions provide a higher natural draw ratio and therefore higher modulus and stiffness enhancement. Further, the results show that increasing MDO process draw ratio leads to more fibrillation and increased crystallinity. Consequently, the tensile modulus and stiffness at the higher draw ratios increase as well and are comparable to conventionally used polymers in outer layers of multilayer flexible packaging. Thus, this work demonstrates that MDO-PE films with enhanced modulus can provide sufficient stiffness for the design of outer layer of mono-material multi-layer all-PE packaging which presents higher potential for mechanical recyclability.

Biomechanical Advantages of Sustained Dynamic Compression Over Static Fixation in Subtalar Arthrodesis

Category: Hindfoot; Basic Sciences/Biologics Introduction/Purpose: Prolonged stresses at the bone/device interface can predispose patients to complications such as loosening or loss of compression in the setting of normal bone resorption during healing. In efforts to address these hardware failures, sustained dynamic compression (SDC) devices were developed, enabling the application of continuous compression in the setting of bone resorption or postoperative joint settling. However, the biomechanical performance of these SDC devices in subtalar arthrodesis constructs has not yet been explored. Thus, this study sought to compare the compression, capacity to adapt to resorption, and torsional stiffness of subtalar arthrodesis constructs utilizing either static or dynamic fixation in three clinically relevant screw trajectories (one device, two devices in parallel trajectories, two devices in diverging trajectories). Methods: Subtalar arthrodesis procedures were simulated on synthetic talus/calcaneus replicates (Sawbones) using two commercially available orthopedic fixation devices (Dynamic = 7.0mm dia. 90mm length, Static = 7.0mm dia; 90mm length, N=6/group) while bones were held in a custom fixture maintaining a gap (to enable simulated resorption). Constructs tested included: 1) single device posteriorly placed, 2) two devices with parallel trajectories, and 3) two devices with diverging trajectories (FigA). After inserting devices according to manufacturer specifications, initial compression and simulated resorption testing were performed (by moving bones into apposition while measuring interfragmentary compression), generating initial load and resorption capacity (resorption distance prior to loss of compression). A second set of simulated arthrodesis procedures were performed on samples that subsequently underwent inversion and eversion torsion testing, generating torsional stiffness values. Data were analyzed using a two-way ANOVA with Tukey post hoc test (α=.05; N=6 replicates/group). Results: Device trajectory (i.e., parallel vs. diverging) did not significantly impact the subtalar construct initial load(p≥0.90), resorption capacity (p≥0.78), or torsional stiffness (p≥0.50, FigB,C,D). The single dynamic device group exhibited significantly increased initial load (p < 0.001, FigB) and resorption capacity (p < 0.001, FigC) as compared to the single and double static device groups. Torsional stiffness was significantly increased in constructs that utilized two static devices as compared to those that used one static (p≤0.023, FigD). Across all constructs conformations (device quantity and trajectory), the dynamic device exhibited significantly increased torsional stiffness as compared to the static device (p=0.006, FigD). Conclusion: These findings demonstrate a notable enhancement in both initial load, resorption capacity, and torsional stiffness with the sustained dynamic compression device (Dynamic) compared to the Static group. Furthermore, the use of a single dynamic device provided significantly increased initial compression, significantly increased resorption capacity, and equivalent (not significantly different) torsional stiffness as compared to the N=2 static device constructs. Notably, device trajectory (diverging vs parallel) did not significantly alter the biomechanical properties of the arthrodesis construct. Thus, surgeons should consider the use of one or more dynamic devices in either trajectory when optimum biomechanical performance is desired. Dynamic Device Provides Increased Subtalar Arthrodesis Construct Compression and Resorption Capacity. A) Representative construct images depicting parallel and diverging device trajectories. B) Initial interfragmentary compression was significantly increased in all dynamic device constructs as compared to static device constructs. C) Resorption capacity was significantly greater in the constructs utilizing dynamic devices as compared to those that used static. D) Across all trajectory/quantity groups, the constructs utilizing dynamic devices displayed significantly increased torsional stiffness as compared to those that used static devices.

Enhancing shear capacity in reinforced concrete deep beams with openings using textile reinforced concrete

This paper showcases shear testing conducted on seven reinforced concrete deep beams featuring square openings, aimed at demonstrating the efficacy of a shear strengthening approach utilizing textile-reinforced concrete (TRC). This experimental program researches two types of openings of 150 × 150 mm and 200 × 200 mm at the centre of the shear spans. The solid beam undergoes testing for comparison with both the unstrengthened and strengthened beams containing openings. The study evaluates the effectiveness of TRC through a comparison of load-displacement curves, cracking patterns, and strains in reinforcements between the strengthened and un-strengthened beams. The experimental results indicate that the TRC strengthening technique effectively boosts the shear-carrying capacity of beams. Examination of the tested beams reveals a significant enhancement in stiffness at the point of maximum force, with improvements ranging from 22% to 86%, depending on the opening size and the number of reinforced textile layers. Rupture in TRC and crushing in the concrete strut are observed in the strengthened beams, whereas the un-strengthened beams show severe crushing in concrete at failure. The test results are compared with calculations based on code provisions, revealing that the prediction model consistently yields values 11 to 44% higher than the experimental results.

Research on the technical improvement of the turbine runner of a power station based on improving stability

AbstractIn view of problems such as the narrow efficiency area, large hydraulic vibration area, pressure pulsation, and serious sediment wear of turbines at the Futang hydropower station, the technical transformation of turbine runners was carried out by modifying the blade shape and increasing the blade thickness, and a combination of numerical simulations based on shear stress transport k–ω turbulence model and tests was adopted to improve the operational stability of power station units. Calculation and testing demonstrate an enlargement of the high‐efficiency zone. Specifically, the optimal efficiency of the runner increases by 0.37%, while the rated efficiency rises by 0.19%. Significant reductions are observed in pressure pulsation within the draft tube and vaneless area decrease of approximately 50%. There is a high‐frequency pressure pulsation in the vaneless zone and the runner under low‐load conditions, and the influence of dynamic and static interference gradually weakens with the increase of opening. The draft tube is prone to eccentric vortex bands under partial working conditions, which causes the unit to be affected by low‐frequency pulsation. This optimization also leads to a notable decrease in runner blade wear, with the maximum sand and water velocity reduced from 45 to 40 m/s, resulting in a 30% reduction in sand wear. Moreover, there is a substantial enhancement in the runner's stiffness, with the thickness of the blade near the high stress area of the upper crown and lower ring increasing by over 50%, and the weight of each individual blade increasing by more than 50%. These research findings validate that modifying the runner blade effectively improves flow patterns, reduces eddy current generation, minimizes pressure pulsation, widens the high‐efficiency zone, decreases wear, and enhances the operational stability of the unit. The technical transformation method and research results of this study have important guiding significance for similar technical transformation of other power stations

Experimental evaluation of bonded/unbonded prestressed precast concrete joints under repetitive loading scenarios: Seismic performance and retrofit intervention

Recently, demands for mitigating structural damage and post-earthquake repair costs have spurred considerable research on prestressed precast frames. In this study, quasi-static tests were conducted on bonded and unbonded prestressed precast beam-column joints (BPPJs and UPPJs) to investigate the influences of bonded/unbonded post-tensioned (PT) strands, evaluate the performance of BPPJs under repeated loading, and verify the effectiveness of post-earthquake retrofitting with external buckling-restrained rods (BRRs). Additionally, the difference between the bonded and unbonded joints was further revealed from the perspective of the tensile forces of the strands at the beamcolumn interface. Test results showed that compared with the UPPJ, the BPPJ exhibited superior performance in terms of lateral stiffness, lateral resistance, and energy dissipating capacity, with a 76.4 % increase in the load-bearing capacity. The compressive zone at the beam end was also deeper in the BPPJ, accompanied by a denser distribution of compressive cracks in the concrete. Furthermore, the bond between the strands and grouting material in the duct accelerated the increase in the tensile forces of the strands at the interface, resulting in considerably more prestress loss in the BPPJ after the tests, which was 120.0 % greater than that in the UPPJ. Under repetitive loading scenarios, although the yielding resistance of the BPPJ decreased by 35.0 % compared with that of the first loading owing to the reduced tensile forces in the strands, relatively minor variations in the load-bearing capacity and energy dissipation were observed. After retrofitting with BRRs, the BPPJ exhibited substantial enhancements in both lateral stiffness and resistance, validating the effectiveness of post-earthquake retrofitting with BRRs.

In and out of plane behaviour of TRM strengthened heritage masonry elements

This paper presents detailed experimental and analytical investigations into the influence of textile-reinforced mortar (TRM) strengthening on the in-plane and out-of-plane response of unreinforced heritage masonry (URM) elements. The URM wall elements consist of hydraulic lime mortar and fired-clay bricks, and the TRM reinforcement employs mortar-embedded layers of alkali age-resistant glass meshes. Apart from the material characterisation tests on mortars, bricks, and TRM coupons, the experimental programme includes axial compression tests on wallettes, diagonal compression tests on square panels, as well as four-point bending tests on rectangular panels. In the latter, the bending loads are applied either parallel or perpendicular to the bed joints in order to assess the joint layout effect on the behaviour. With the aid of digital image correlation, the in-plane and out-of-plane enhancement in stiffness, strength, and ductility of the masonry elements due to the TRM strengthening is quantified, while the TRM influence on the crack patterns and failure modes is also examined. The results show that the number of mesh layers has a significant influence on the behaviour for the out-of-plane bending tests but plays a less pronounced role in the in-plane shear cases. Modified analytical models for the in-plane shear and out-of-plane bending capacities of reinforced masonry elements, of the type examined in this study, are also proposed and assessed alongside existing codified procedures. The application of current code provisions results in overly conservative estimates. In contrast, the proposed analytical approaches for determining the in-plane and out-of-plane strength provide close prediction of the experimental capacities from this study as well as those from a wider collated database of previous tests, and are therefore suitable for implementation in practical assessment and rehabilitation guidelines.

4D printing of magneto-responsive shape memory nano-composite for stents

Abstract This study focuses on the 4D printing simulation technique of magneto-responsive shape memory nanocomposite stents. A nanocomposite material was created by incorporating polycaprolactone, a shape memory material, with Fe3O4 to enhance magnetic responsiveness and stiffness. Tensile tests were conducted, and the material properties were applied to finite element analysis. Shape memory experiments were also performed to measure the temperature at which shape memory progression occurs due to magnetic response. In the 4D printing simulation, different coefficients of thermal expansion and the measured temperatures were reflected in the sections where shape memory is activated to implement shape memory behavior. The specimen simulation confirmed shape memory behavior progressing from 145 degrees to 3 degrees, while the stent simulation demonstrated satisfactory expansion to a radius of 3 mm. This study proposes a controllable method for implementing shape memory considering temperatures induced by magnetic response, showing potential for various medical device applications.

Reinforcement of Polyimine Covalent Adaptable Networks with Mechanically Interlocked Derivatives of SWNTs.

AbstractThere is an urgent need for new approaches to reduce the environmental impact of plastics. One approach is to enhance recyclability. Covalent adaptable networks (CANs), where crosslinks are chemically reversible, offer an attractive alternative to thermoset materials. Another option is to strengthen polymers using nanofillers, to reduce the amount of material needed. In this regard, single‐walled carbon nanotubes (SWNTs) are excellent candidates as fillers due to their extreme strength‐to‐weight ratio and dimensionality. Here, SWNTs functionalized as mechanically‐interlocked derivatives (MINTs) are shown to significantly improve the mechanical properties of polyimine (PI) CANs, with close to optimal efficiency. Enhancements in both stiffness and ultimate strength, approaching 100% load transfer considering the SWNT loading, are observed for PI MINT, while composites made with pristine SWNTs exhibit poor improvement. The PI MINT CANs can be recycled both thermally and chemically without compromising their mechanical properties. Finally, prototype carbon fiber PI MINT laminar composites are also fabricated and characterized, demonstrating a significant increase in their mechanical properties.

Mechanical and, photon transmission properties of rare earth element (REE) doped BaO–B2O3–Li2O–Al2O3–P2O5 glasses for protection applications

This study explores the dual functional capabilities of rare earth (REE) doped BaO–B2O3–Li2O–Al2O3–P2O5 glasses, with an emphasis on the 1.50Dy-Tb-Eu composition, previously recognized for its superior luminescent properties. By employing Monte Carlo simulations and Phy-X/PSD software, we have methodically evaluated the gamma-ray and neutron shielding efficacies of these materials. Our key findings indicate that the 1.50Dy-Tb-Eu sample not only excels in luminescence but also demonstrates superior gamma-ray shielding, characterized by low exposure buildup factors, and other related properties across varying energy spectra. Furthermore, the Tb-Eu3.0 variant, enriched with the highest Europium (Eu) content among the bi-REE doped glasses, exhibited the most effective neutron attenuation. Additionally, our investigation into the mechanical properties of these glasses, through the estimation of their Elastic Moduli using a mixture rule approach, revealed a significant enhancement in stiffness with the incorporation of Dy, Eu, and Tb. The mechanical properties were evaluated using a mixture rule approach to estimate the Elastic Moduli. This highlights the crucial role of these dopants in not only improving the luminescent and radiation shielding capabilities but also in strengthening the mechanical integrity of the glasses. The study substantiates the premise that the integration of specific REE elements significantly enhances the glass materials' shielding properties without compromising their luminescent functionality. The obtained findings would be significant for implications on the development of advanced materials tailored for industries where high optical quality, effective radiation protection, and robust mechanical properties are paramount. It can be concluded that Dy-Tb-Eu incorporation into BaO–B2O3–Li2O–Al2O3–P2O5 glasses can be considered as a monotonic strategy to achieve a harmonious balance between luminescence, radiation shielding, and mechanical performance.

Seismic vulnerability analysis of palace-style timber structures base on lumped mass model considering column rocking effect

To investigate the influence of joint reinforcement on the vulnerability of palace-style ancient timber structures, a spring-rigid rod analysis model was established, considering the mechanical behavior of tenon-mortise joints, column base joints, and bracket set joints. A lumped mass model was proposed using the centroid method and stiffness equivalent method and the accuracy of the simplified model is verified through shake table tests. Additionally, the influence of reinforcement on tenon-mortise joints and bracket set joint on the seismic displacement response was investigated, the optimal reinforcement range for joints was determined. Finally, incremental dynamic analysis was conducted on the model considering joint reinforcement, and the influence of optimal joint reinforcement on the seismic vulnerability of timber structures was researched. The study found that the optimal stiffness enhancement of column frame mortise-tenon joints range from 4 to 6 times and the stiffness of bracket set joints by 2.9 times. The probability of structural collapse of reinforced both mortise-tenon joints and bracket set joints was reduced by 15.56 %. However, individually reinforcing either tenon-mortise joints or bracket set joints only slightly decreases the probability of collapse.

Investigation of the fractionalized polyethylene terephthalate (PET) on the properties of stone mastic asphalt (SMA) mixture as aggregate replacement

Polyethylene terephthalate (PET) is a widely used plastic that accounts for almost 18 % of global polymer production and is non-biodegradable, making it a major cause of environmental pollution. Innovative solutions are needed to address PET waste management and reduce its impact. This study aims to investigate the impact of adding PET, on the engineering characteristics of a Stone Mastic Asphalt (SMA-20) mixture. Laboratory tests were conducted to assess the volumetric and mechanical properties of asphalt mixes containing different proportions of PET as fine and filler (ranging from 0 % to 30 %) by volume of aggregates. The results show that the PET incorporation into the asphalt mixture has significantly improved the performance. The addition of PET (fine and filler) to asphalt mixtures significantly increases their resilient modulus (MR). The mixtures containing 10 % PET as fine and filler are 20 % and 22 % higher in MR than the control mixture. Moreover, the moisture assessment shows that the PET mixture has a higher tensile strength ratio (TSR) value of 85.9 % and 83.90 % for Fine-10 and Filler-20, thus meeting the AASHTO requirement of ≥80 %. The utilization of PET as aggregate replacement significantly improves the permanent deformation characteristics of asphalt mixtures by decreasing permanent strain. The Fine-20 and Filler-20 revealed promising results by reducing the strain to 0.92 % and 0.81 %. Also, the enhancement in the creep stiffness modulus with 216 and 244 MPa. Furthermore, the addition of PET up to a concentration of 20 % had a beneficial effect on the fatigue response of mixtures. For instance, the failure cycles of the Filler-20 and Fine-10 are 23,231 and 17,521 cycles at a load of 2250 N, whereas the control mixture only endures 8581 failure cycles. In conclusion, PET addition significantly improves SMA properties, promoting waste material utilization in the pavement industry.