Displacement Angle Research Articles

Thermo‒mechanical behavior of energy pile group in dry sand subjected to a horizontal load

The energy pile is an innovative structure element designed to utilize geothermal energy while simultaneously supporting building loads by means of integrating heat exchange tubes into the pile foundation. Despite the intricate thermodynamic characteristics of energy pile groups, research on them remains limited. This study investigated the horizontal load transfer mechanism of an energy pile group in dry sand by conducting a model test on a 2 × 2 energy pile group subjected to horizontal loads. Specifically, the impact of heating or cooling a single pile within the energy pile group was examined. The results showed that the bending moment was significantly larger on a single pile subjected to a thermal load than that of the other piles, with the majority of this variation occurring in its upper part. Additionally, the horizontal load had a strong influence on the rotational angle and horizontal displacement of the energy pile group. The rotational angle and horizontal displacement decreased with increasing depth. With rising temperature, the interaction between the pile and the soil intensified, and the soil pressure on the upper part of the pile increased while that in the lower part decreased.

Study on Seismic Behavior and Component Vulnerability of Corroded RC Shear Walls Subjected to Flexural Shear Failure

ABSTRACT The impact of corrosion degree, axial compression ratio, reinforcement ratio of longitudinal bar and horizontal distribution rebar, and stirrup of boundary column on seismic performance of RC shear walls were investigated. The corrosion forms (rust expansion cracks and corroded steel bars), failure process, hysteretic characteristics, bearing capacity, and deformability were compared. Subsequently, a numerical model of corroded RC shear walls was established adopting shell elements. Finally, according to the numerical simulation method, considering the uncertainty of corrosion degree and material parameters, the vulnerability models of RC shear wall components with different corrosion degrees were built. The results show that the mechanical properties of the shear wall were seriously deteriorated due to the corrosion of steel bars, and the ultimate displacement and ductility coefficient of severely corroded specimens were reduced by 28.5% and 12.27% respectively, compared to non-corroded specimens. A proposed numerical modeling method for corroded RC shear walls based on shell element is accurate, and the bearing capacity error and energy dissipation error of the simulation and test results were less than 20%. As the degree of corrosion grew, the probability of shear wall components experiencing more severe failure added significantly. When the displacement angle was 1/120 (This is the limit value of elastic-plastic displacement angle specified in the code), the probability of DS3 and DS4 occurring in the shear wall with a corrosion degree of 0% were 56% and 39.44%, and the probability of DS4 and DS5 occurring in the shear wall with a corrosion degree of 10% were 41.1% and 38.44%.

Seismic Response and Mitigation Analysis of a Subway Station in the Site with Weak Interlayers

Challenges related to seismic performance and seismic mitigation are more pronounced in the presence of weak interlayers compared to typical layered soil conditions. This study focuses on a double-layer double-span rectangular frame subway station structure. A coupled static–dynamic finite element analysis model of the soil-structure system is established by using the finite element software ABAQUS/CAE V 6.14. The research investigates the influence of factors such as interlayer thickness, location, and strength on the seismic response of subway station structures. Furthermore, in order to evaluate the effectiveness of FPB in mitigating seismic effects in the weak interlayer ground, two different schemes are proposed in this paper. One is the structure without FPB and the other is the structure with FPB on the top of the central column. The findings reveal that weak interlayers exert a significant influence on the seismic response of subway station structures, especially when these lower-strength weak interlayers are located within the central portion of the subway station structure and exhibit considerable thickness. The FPB on the top of the central column can reduce the overall lateral stiffness of the subway station structure. This, in turn, results in a slight increase in the deformation of sidewall and inter-story displacement angles, accompanied by a marginal exacerbation of sidewall damage. However, the implementation of FPB effectively reduces the deformation of the central column and substantially mitigates the extent of damage to the central column.

Assessment of the seismic failure of reinforced concrete structures considering the directional effects of ground motions

Seismic intensity measures at different levels significantly impact the seismic damage of building clusters. Reinforced concrete (RC) structures are a type of building widely used in different regions worldwide. A large amount of field seismic damage observation data indicates that within the same seismic intensity zone, the directional effects of varying ground motions lead to significant differences in damage to RC structures on different floors. However, relatively little research has been conducted on estimating the seismic fragility and vulnerability of RC structures considering the directional effects of seismic action. To further study the directional effect of seismic motion on the damage of different floors, this study conducted dynamic time history and spectral analyses on 1472,379 acceleration records in multiple directions obtained from monitoring at nine actual seismic stations during the 2008 Wenchuan earthquake in China. This paper innovatively reports on the actual damage features of RC structures during the Mw6.2 magnitude Jishishan earthquake in Gansu Province, China, on December 18, 2023 (the most severe destructive earthquake in China in 2023) and analyses the influence of earthquake directionality on the damage to different floors of RC structures. A three-dimensional numerical model of a four-story RC frame structure was established using numerical simulation and the finite element method. Different intensity measures were taken to input seismic excitations of different intensities into the RC structure in the 0°, 30°, 60°, and 90° directions, and damage simulation analysis was conducted. The nonlinear dynamic time history curves of structures under multiple directions of seismic excitation in different intensity zones have been developed. Using the interstory stiffness and interstory displacement angle as engineering demand parameters, damage assessment curves and stress clouds for RC structures with 1–4 floors considering different seismic directional effects were generated. The analysis results and major findings indicate that the seismic sequence in the 0° direction has a relatively heavy impact on the first floor of the RC structure in zone IX, which is consistent with the actual field observation results.

Seismic Performance of a Single-Story Timber-Framed Masonry Structure Strengthened with Fiber-Reinforced Cement Mortar.

Timber-framed masonry structures are widely used around the world, and their seismic performance is generally poor. Most of them have not been seismically strengthened. In areas with high seismic fortification intensity, there are great potential safety hazards. And it is urgent to carry out effective seismic reinforcement. However, due to the complicated construction process of the existing reinforcement technology, the poor durability of the reinforcement materials, and the significant disturbance to the life of the original residents, an efficient single-story timber-framed masonry structure reinforcement technology suitable for comprehensive promotion and application has not been explored. In this paper, a fiber-reinforced cement mortar (FRCM) material was proposed. A 1/2 scale model of a single-story timber-framed masonry structure was taken as the research object. The method of strengthening a single-story timber-framed masonry structure with FRCM layer was adopted. And the shaking table test of the model before and after reinforcement was carried out in turn. The dynamic characteristics, failure modes, acceleration response and displacement response of the FRCM layer-strengthened structure were analyzed through comparisons of the two cases. The experimental results showed that the FRCM layer significantly improved the seismic performance of the seismic-damaged single-story timber-framed masonry structures. The X- and Y-direction natural frequencies of the model structure were increased by 31.30% and 30.22%, respectively, after the structure was strengthened with FRCM. During a rare eight-degree earthquake, the inter-story displacement angles in the X- and Y-direction of the unreinforced model reached 1/98 and 1/577, respectively, and the structure was destroyed, while the inter-story displacement angle of the FRCM-reinforced model was only 1/2 of that the unreinforced model. During a rare nine-degree earthquake, the X-direction inter-story displacement angle of the model strengthened with FRCM reached 1/78 and the Y-direction inter-story displacement angle reached 1/178. At this time, the reinforced model structure was destroyed, but there was no collapse of the structural components, which met the seismic design objectives of "operational under the design minor seismic intensity, repairable damage under the design seismic precautionary intensity, and collapse prevention under the design rare seismic intensity", which proved that the FRCM layer was an effective and feasible way to strengthen the existing single-story wood-masonry rural building.

Influence of tactile and verbal guidance on lateral weight-shifting in double-leg standing after total hip arthroplasty

IntroductionAnomalous gait after total hip arthroplasty (THA), marked by increased trunk lateral flexion during weight-bearing, is a noteworthy aspect to consider for enhancing ambulatory capacity. One potential training modality that is feasible in the early post-THA period is lateral weight shifting during double-leg standing. However, the influence of physical therapists’ instructional guidance on trunk lateral flexion and hip abductor muscle activity in this context remains unclear. PurposeTo investigate the influence of physical therapist's guidance directed towards reducing the trunk lateral flexion angle during lateral weight-shifting in double-leg standing post-THA. MethodsTwenty THA patients, assessed at 2 weeks postoperatively, performed lateral weight-shifting under two conditions: the normal condition and the instructed condition, for comparison. The latter involved tactile and verbal guidance guidance to minimize trunk lateral flexion. Patients were categorized based on trunk flexion direction for comparison, exploring the correlations between hip abductor muscle activity and kinematic parameters. ResultsIn the instructed condition, a significant reduction in trunk lateral flexion and increased hip lever arm length were observed compared to those in the normal condition. Patients with trunk flexion towards the operated side exhibited a notable reduction, while those on the non-operated side showed no significant changes. Gluteus medius muscle activity correlated with trunk lateral flexion, and tensor fasciae latae muscle activity correlated with body's center of mass lateral displacement and hip adduction angle. ConclusionsPhysical therapist's guidance influenced lateral weight-shifting in double-leg standing post-THA. Differences in the trunk lateral flexion direction may lead to different effects from the guidance.

Numerical Simulation and Design of a Mechanical Structure of an Ankle Exoskeleton for Elderly People

This article presents the numerical simulation and design of an ankle exoskeleton oriented to elderly users. For the design, anatomical measurements were taken from a user of this age group to obtain an ergonomic, resistant, and exceptionally reliable mechanical structure. In addition, the design was validated to support a “weight range” of users between 50 and 80 kg in order to evaluate the reaction of the mechanism within the range of loads generated in relation to the first principal stress, the safety coefficient, the Von Mises stress, and principal deformations, for which the 3D CAD software Autodesk Inventor and theoretical correlations were used to calculate the displacement and rotation angles of the ankle in the structure. Likewise, two types of materials were evaluated: ABS (acrylonitrile butadiene styrene) and a polymer reinforced with carbon fiber. Finally, the designed pieces were assembled with the guarantee that the mobility of the system had been validated through the numerical simulation environment, highlighting that by being generated through 3D printing, manufacturing costs are reduced, allowing them to be accessible and ensuring that more people can benefit from this ankle exoskeleton.

Experimental investigations on prefabricated interlocking prestressed tendon composite joint and its application to beam-column connection

This study proposes an interlocking prestressed tendon composite joint (I-PTCJ) that can be applied to a beam–column connection of the multi-story structure. First, the main structure and prefabrication process of the I-PTCJ were introduced. Next, three beam–column specimens using local and integral I-PTCJs (named specimens PT1 and PT2) and a traditional interlocking joint (I-J, specimen named TG1) were designed and manufactured. Furthermore, quasi-static experiments were performed on these three specimens to evaluate their seismic performance. In addition, the influence of the prestressed tendons (PTs) and the arrangement mode (local or integral) of the I-PTCJs were investigated in detail. Finally, a preliminary comparative analysis between the experimental and simulated results was carried out. The results showed that the introduction of the PTs reduced the degree of damage within the PT installation area, delayed the cracking of the interlocking interface, and improved the bond performance of the longitudinal rebar. However, it also aggravated the degree of damage outside the PT installation area and reduced the displacement ductility and energy dissipation capacity of the specimen. Compared with TG1 (using the traditional I-J), PT1 (using the local I-PTCJ) had a higher peak load, lower displacement ductility, higher shear deformation, gentler rigidity deterioration, and lower cumulative energy dissipation. Compared with PT1, PT2 (using the integral I-PTCJ) had a higher peak load, lower displacement ductility, lower shear deformation, lower cumulative energy dissipation, and better bond performance of the longitudinal rebar. Both the yield displacement angle and ultimate displacement angle met the deformability requirement of the existing building design codes. Thus, the proposed I-PTCJ can be applied to the beam-column connection of multi-story structures.

Wind and Wave-Induced Vibration Reduction Control for Floating Offshore Wind Turbine Using Delayed Signals

Active vibration control is a critical issue of the wind turbine in the field of marine energy. First, based on a three-degree-of-freedom wind turbine, a state space model subject to wind and wave loads is obtained. Then, a delayed state feedback control scheme is illustrated to reduce the vibration of platform pitch angle and tower top foreaft displacement, where the control channel includes time-delay state signals. The designed controller’s existence conditions are investigated. The simulation results show that the delayed feedback H∞ controller can significantly suppress wind- and wave-induced vibration of the wind turbine. Furthermore, it presents potential advantages over the delay-free feedback H∞ controller and the classic linear quadratic regulator in two aspects: vibration control performance and control cost.

Study on prefabricated composite shear wall cladding anti-shedding connection structure

Fabricated steel structure systems have undergone significant advancements. However, problems associated with exterior wall panel systems have become increasingly prominent, particularly the issue of exterior wall panel shedding. Three full-scale fabricated composite shear wall exterior panel components were designed and tested under quasi-static conditions. The failure sequence and characteristics of the exterior wall panels at different displacement angles, including their out-of-plane displacement and stiffness degradation, were evaluated to assess their seismic and connection performance in different building construction methods. The results indicated that drilling holes near the centre of autoclaved lightweight concrete (ALC) boards improved the seismic performance of wall panels. Long round holes in the ALC boards allowed the dissipation of sliding energy during the initial deformation of wall panels. Furthermore, wall panels with bonded anchorage connections for rockwool boards exhibited better seismic performance than those with pure anchorage connections. To verify the accuracy of the findings, a structural finite element model was established, and the influences of various parameters, such as the position of ALC board connecting bolts, length of ALC board holes, and bonding rate of rockwool boards, on the stress and deformation of the exterior wall panel system were analyzed. Based on the test results and finite element simulation analysis, an anti-shedding connection construction method was proposed.

Assessment of the Relationship between Antero-Posterior Dental Malocclusions, Body Posture Abnormalities and Selected Static Foot Parameters in Adults.

Objectives: This study aimed to find if a relationship exists between antero-posterior malocclusions and the level of musculoskeletal disorders in adults, including body posture and static foot analysis. Methods: In all, 420 participants were recruited through convenience sampling (Kraków University students and patients of a local dentist's practice). Following general medical interviews, dental examinations and consideration of inclusion and exclusion criteria, 90 healthy volunteers (ages 19-35) were enrolled and assigned to three groups (n = 30) based on occlusion type (Angle's molar Class I, II or III). The research procedure involved occlusion and temporomandibular disorder assessment conducted by a dental specialist. Comprehensive morphological measurements of body asymmetry were performed using the Videography 2D package and FreeSTEP software, which calculated the parameters determined from anterior, posterior and lateral projection photos. Foot loading distribution was analyzed using the FreeMED baropodometric platform. Results: Significant differences were demonstrated in the positioning of the head, cervical and lumbar spine in the sagittal plane among individuals with the analyzed occlusal classes (p < 0.05). Individuals with Angle's Class II exhibited significantly greater forward head positions and greater depths of cervical and lumbar lordosis compared with individuals with Class III or Class I. Those with overbites had higher forefoot loading. The Class III individuals exhibited greater L-R displacement, indicating a larger angle of displacement of the centers of the right and left feet relative to the lower edge of the measurement platform, suggesting pelvic rotation. Conclusions: An inclination for concurrent occurrences of malocclusions and posture deviations in the sagittal plane was observed. An interdisciplinary approach involving dentistry and physiotherapy specialists which utilizes tools for comprehensive posture assessment is crucial for diagnosing and treating such conditions.

Assessing Ground Motion Intensity Measures and Structural Damage Measures in Underground Structures: A Finite Element Analysis of the Daikai Subway Station

Research on the characterization of ground motion intensity and damage of underground structures is limited, while reasonable selection of ground motion intensity measures and structural damage measures is a crucial prerequisite for structural seismic performance evaluation. In this study, a two-dimensional finite element model of soil and structures was established based on the Daikai subway station in Japan. Through incremental dynamic analysis, 32 ground motion intensity measures and seven structural damage measures were comprehensively evaluated from seven properties, including efficiency, practicality, proficiency, scaling robustness, relativity, hazard computability, and sufficiency. According to the analysis results, the purpose and significance of each property during measure optimization were hierarchically sorted out. The results show that peak ground acceleration, acceleration spectrum intensity, and sustained maximum acceleration are recommended as ground motion intensity measures, while maximum inter-story drift ratio, column end displacement angle, and two-parameter measures are recommended as the structural damage measures for seismic performance evaluation of the shallow-buried subway station. Furthermore, measure optimization approaches are proposed as follows: the basic selection of IMs should satisfy scaling robustness, hazard computability, and sufficiency to site condition; the optimal selection of IMs is suggested to be evaluated mainly through efficiency, practicality and proficiency, and verified through relativity and relative sufficiency between IMs. The optimal selection of DM is suggested to be evaluated through four properties, including efficiency, practicality, proficiency, and relativity.

Structural optimization design of multi ribbed composite wall of building components under seismic load based on random optimization algorithm and resilience model

The multi ribbed composite wall structure is also known as the multi ribbed wall panel light frame structure. This structure is suitable for housing construction in the residential field. The special structural failure process and mode of multi ribbed composite walls are different from traditional walls. To fully utilize the excellent structural performance in building construction and improve the seismic performance of the building, based on the transformation principle of subset optimization algorithm for optimization problems, a constrained subset simulation optimization algorithm suitable for optimizing the maximum displacement angle of multi ribbed composite wall panels is designed. The Bayesian algorithm is used to construct a restoring force model for multi ribbed composite wall panels. The constrained subset simulation optimization algorithm and resilience model are used to optimize the seismic performance of 4-layer multi ribbed composite wall panels. The results show that the section height and the equivalent slant support width of the continuous column for the 4-story multi ribbed composite wall panel change from discrete distribution to aggregation with the increase of iteration. Finally, the sampling is stable in the 9th floor. At this time, the section height of the continuous column is 230 mm, and the equivalent slant support width is 525. After optimization, the failure probability of both extreme displacement angle states has decreased. When the peak ground acceleration is 1.0 g, the optimized second limit state failure probability is less than 100%. When the peak ground acceleration value is between 0.2 g and 0.6 g, both limit states show a rapid upward trend. The constrained subset simulation optimization algorithm and Bayesian quantitative resilience model proposed in the research can effectively optimize the seismic performance of multi ribbed composite walls.

Biomechanical comparison of a new undercut thread design vs the V-shape thread design for pedicle screws

BACKGROUND CONTEXTThread shape is regarded as an important factor influencing the fixation strength and osseointegration of bone screws. However, commercial pedicle screws with a V-shaped thread are prone to generating stress concentration at the bone-screw interface, thereby increasing the risk of screw loosening. Thus, modification of the pedicle-screw thread is imperative. PURPOSEThis study aimed to investigate the fixation stability of pedicle screws with the new undercut thread design in comparison to pedicle screws with a V-shaped thread. STUDY DESIGNIn vitro cadaveric biomechanical test and finite element analysis (FEA). METHODSPedicle screws with the undercut thread (characterized by a flat crest feature and a tip-facing undercut feature) were custom-manufactured, whereas those with the V-shaped thread were procured from a commercial supplier. Fixation stability was assessed by the cyclic nonpullout compressive biomechanical testing on cadaveric female osteoporotic vertebrae. The vertical displacement and rotation angle of the 2 types of pedicle screws were calculated every 100 cycles to evaluate their resistance to migration and rotation. FEA was conducted to investigate the stress distribution and bone damage at the bone-screw interface for both types of pedicle screws. RESULTSBiomechanical testing revealed that the pedicle screws with the undercut thread exhibited significantly lower vertical displacement and rotation angles than the pedicle screws with the V-shape thread (p<0.05). FEA results demonstrated a more uniform stress distribution in the bone surrounding the thread in the undercut design than in the V-shape design. Additionally, bone damage resulting from the pedicle screw was lower in the undercut design than in the V-shape design. CONCLUSIONSPedicle screws with an undercut thread are less prone to migration and rotation and thus more stable in the bone than those with a V-shape thread. CLINICAL SIGNIFICANCEThe undercut thread design may reduce the incidence of pedicle-screw loosening.

The Seismic Performance of Self-Centering Ribbed Floor Flat-Beam Frame Joints

To achieve rapid post-earthquake repair of self-centering ribbed floor flat-beam frame structures, a ductile hybrid joint consisting of dog-bone-shaped, weakened, energy-dissipating steel bars connected to the upper and lower column sections through high-strength threads is proposed based on the damage control design concept. By moving the ductile energy-dissipating zone out to the locally weakened section of the energy-dissipating steel bars and the locally unbonded prestressed steel bars in the core area, the residual deformation was limited and the seismic performance improved. Based on the working principle of hybrid joints, low cycle loading tests were conducted on two joint specimens to analyze the influence of lateral prestress on the seismic performance of the hybrid joints. Numerical modeling methods were used to compare the position of the energy-dissipating steel bars in the composite layer and the friction performance of the joints. The research results indicated that the hybrid joint had stable load bearing, deformation, and energy dissipation capabilities, with damage being primarily concentrated in the energy-dissipating steel bars. Even at an inter-story displacement angle of 5.5%, the upper and lower column segments remained elastic. After unloading, the connection seam at the joint was closed, and the self-centering performance was good. When the inter-story displacement angle reached 5.5%, the lateral prestress increased from 150 kN to 250 kN, the ultimate bearing capacity of the joint increased by 16.3%, and the cumulative energy consumption increased by 30.0%. The influence of the friction coefficient of the joint surface on the structural performance was set at a threshold of 0.7. When it was less than the threshold, the ultimate bearing capacity and initial stiffness of the joint increased with the increase in the friction coefficient. After reaching the threshold, the increase in the ultimate bearing capacity of the joint slowed down, and the rate of stiffness degradation gradually accelerated. This joint showed excellent seismic performance and can thus achieve post-earthquake repair of structures.

Design and analysis of a lower limb assistive exoskeleton robot.

In recent years, exoskeleton robot technology has developed rapidly. Exoskeleton robots that can be worn on a human body and provide additional strength, speed or other abilities. Exoskeleton robots have a wide range of applications, such as medical rehabilitation, logistics and disaster relief and other fields. The study goal is to propose a lower limb assistive exoskeleton robot to provide extra power for wearers. The mechanical structure of the exoskeleton robot was designed by using bionics principle to imitate human body shape, so as to satisfy the coordination of man-machine movement and the comfort of wearing. Then a gait prediction method based on neural network was designed. In addition, a control strategy according to iterative learning control was designed. The experiment results showed that the proposed exoskeleton robot can produce effective assistance and reduce the wearer's muscle force output. A lower limb assistive exoskeleton robot was introduced in this paper. The kinematics model and dynamic model of the exoskeleton robot were established. Tracking effects of joint angle displacement and velocity were analyzed to verify feasibility of the control strategy. The learning error of joint angle can be improved with increase of the number of iterations. The error of trajectory tracking is acceptable.

Molecular Dynamics Simulation for the Acidic Compounds Retention Mechanism Study on Octyl-Quaternary Ammonium Mixed-Mode Stationary Phase.

With the widespread application of mixed-mode chromatography in separation analysis, it is becoming increasingly important to study its retention mechanism. The retention behavior of acidic compounds on mixed-mode octyl-quaternary ammonium (Sil-C8-QA) columns was investigated by computer simulation. Firstly, the benzoic acid homologues were used as the analytes, and the simulation model was constructed by the Materials Studio. Geometric optimization, annealing and molecular dynamics (MD) simulation of these complexes resulted in optimized conformations. The binding energy, mean square displacement (MSD) and torsion angle distribution generated by MD simulation were then analyzed. The results showed that the more negative binding energy, the greater the MSD and the narrower the torsion angle distribution, indicating that the stationary phase behaves with stronger interaction and retention. The retention behavior of five acidic drugs on the Sil-C8-QA column was then successfully explained by simulation. Acidic drugs are more retentive on the mixed-mode column due to the more substantial interaction brought by the reversed-phase/ion-exchange mixed-mode mechanism compared to other single-mode columns. This simulation method is expected to provide ideas for studying the separation mechanism and predicting the retention behavior of more complex samples.

Enhancing of damping capacity in crumb rubber concrete at various damage levels: Effects of fly ash and ground granulated blast furnace slag

Crumb rubber (CR) incorporated as damping units in concrete, partially replacing natural aggregates, enhances the material's damping capacity. However, the filler type and replacement rate will usually influence the crack development of crumb rubber concrete (CRC) elements under repeated loading, which in turn influences their damping capacity at different damage levels. Thus, the damping characteristics of CRC cantilever beams at different damage levels, influenced by filler type and substitution rate, are investigated in the present paper through low-cycle repeated damage and free vibration tests. The results reveal that partial cement replacement with fly ash (FA) significantly enhances the energy dissipation capacity, especially at a 30 % FA replacement rate. Positive effects on the damping ratio are observed only when the ground granulated blast furnace slag (GGBFS) substitution rate is 30 %. For the CRC cantilever beams both with and without filler, the damping ratio shows an increasing and then decreasing trend with increasing displacement angle. The maximum damping ratio is exhibited when the displacement angle is 0.02. With increasing displacement angle, FA and GGBFS doping accelerated the degradation rate of the bending dynamic stiffness and the damage index rose faster. A model is formulated to describe the correlation between the damping ratio and the damage index in CRC cantilever beams both with and without filler. The effect of filler incorporation on the pores and microcracks may be the main reason for the damping ratio increase as observed by micro-morphology.

Influence of aging on the relation between head control and hip joint kinematics during crossover stepping.

Falls in older individuals are a serious health issue in super-aged societies. The stepping reaction is an important postural strategy for preventing falls. This study aimed to reveal the characteristics of lateral stepping in response to mechanical disturbance by means of an analysis of the hip joint kinematics in the stepping leg and head stability during crossover steps. The participants included 11 healthy older and 13 younger individuals. An electromagnet-controlled disturbance-loading device induced crossover steps due to lateral disturbance. Responses were measured using a motion capture system and force plates. The righting reaction of the head was quantified by lateral displacement (sway), neck joint kinematics (angle displacement, angular velocity), and neck joint moment during crossover stepping. Moreover, the relationship between the neck lateral bending moment and angular velocity of hip flexion/adduction of the stepping leg was examined. The lateral head sway was significantly larger in the older participants (1.13±0.7 m/s2) than in the younger individuals (0.54±0.3 m/s2); whereas, the angle displacement (older -14.1±7.1 degree, young -8.3±4.5 degree) and angular velocity (older 9.9±6.6 degree/s, 41.2±27.7 degree/s) of the head were significantly lower in the older than in the younger participants. In both groups, the moment of neck lateral bending exhibited a significant negative correlation with the hip flexion angular velocity of the stepping leg. Correlation analysis also showed a significant negative correlation between the neck lateral bending moment and hip adduction angular velocity only in the older group (r = 0.71, p<0.01). In conclusion, older individuals increased instability in the lateral direction of the head and decreased righting angle displacement and angular velocity of the head during crossover steps. The correlation between neck moment and hip flexion/adduction angular velocity suggested a decrease in step speed due to increased neck muscle tone, which could be influenced by vestibulospinal reflexes.

Seismic performance investigation of irregular and complex connected structures based on the influence of ground fissure activity

To investigate the dynamic response of irregular and complex connected structure, the comprehensive soil and connected structure model was developed, which is considered the site condition of different foundation soils. This study explored on the deformation law of the connected structure, and analyzing the structural displacement, acceleration, and torsional response under various seismic conditions. The findings revealed that the presence of ground fissures significantly amplifies the dynamic response of connected structures, with a greater influence from the hanging wall. Additionally, the lag effect was observed in the generation of the peak ground acceleration (PGA) in the site model considering ground fissures, but the result surpassed those in ordinary sites. During the elastic-plastic loading stage, the study observed that the maximum inter-story displacement angle remained within the limits prescribed by specifications. Due to the varying distances between column bases of the main area and ground fissures, there is a significant magnification effect in inter-story torsional angle. The incorporation of sliding supports emerged as an effective measure in mitigating the relative displacement of connected structures, consequently reducing the translational-torsional coupling effect during rarely occurred earthquake. The research results provide reference for the seismic performance analysis of connected structures under complex site conditions.