Wall Length Research Articles

Study on seismic performance of green fiber-reinforced concrete shear wall

Reinforced concrete shear walls are widely used in civil engineering and it is necessary to study new environmental protection methods to improve its seismic performance.The green fibers (namely recycled steel fibers, collectively referred to as green fibers in this article) formed by cutting high quality steel wires extracted from waste tires and have good tensile, flexural, and yield strength.So the improvement effect of green fibers on the seismic performance of concrete shear wall is studied in this paper. Cyclic loading experiments are used to explore the seismic performance of plain concrete shear wall specimen, green fiber-reinforced concrete shear wall specimen mixed with green fibers 1.0 L (L is the length of shear wall, the same as below) and 1.5 L height and fiber volume ratio of 1.5%. The results show that with the addition of green fibers and the increases in incorporation height of green fibers, the ultimate bearingcapacity, ductility, and energy dissipation capacity of concrete shear wall specimens gradually increase. As the specimen increases the fiber incorporation height, the ultimate bearing capacity of the shear wall increases, and the ductility and energy dissipation capacity increase, and stiffness degradation of specimens gradually slows down. That is, the seismic performance of shear wall specimens is gradually improved. The error between the experimental values and calculated values obtained by the deduced calculation formula is within the allowable range. The results of Abaqus finite element numerical simulation are in good agreement with the experimental results. And through the numerical simulation of the other two specimens, it can be concluded that the flexural performance of green fiber-reinforced concrete shear wall specimens increases with the increases in fiber volume ratio and the decreases in axial compression ratio. This study can provide a reference for the research on the seismic performance of fiber-reinforced concrete shear wall and the application of steel wires extracted from waste tires in practical engineering.

Numerical investigation of lateral behaviour of steel‐timber hybrid frames

AbstractThis paper examines the response of steel‐timber hybrid (STH) lateral stability systems for medium‐rise buildings. A ten‐storey baseline STH structure was designed to codified procedures and compared with a steel‐concrete composite structure. Detailed numerical models were constructed in which specific constitutive representations were assigned to steel‐timber and timber‐timber connections. Parametric investigations on the STH structure were carried out in which the cross laminated timber panel layups, timber shear wall length, and connection characteristics were modified. The study indicated that the STH structure had larger lateral deformations compared to the steel‐concrete structure, both within code limits. For the same design loads, the reduction in self‐weight from the steel‐concrete structure to the STH structure was 73.1%, whilst the floor depth was reduced by 17.2%, respectively. Parametric studies showed that the lateral response of STHs is generally improved with the effective thickness of the timber infill panel and is influenced by the panel layup. Increasing the shear wall length generally enhances the lateral stiffness, yet the overall performance is reduced with the increase of panel connections. The reduction in self‐weight, member sizes and replacement of the concrete with timber led to a reduction in embodied carbon of more than 32.7% whilst achieving similar structural performance.

Revealing the Sound Transmission Loss Capacities of Sandwich Metamaterials with Re-Entrant Negative Poisson's Ratio Configuration.

Due to the influence of mass law, traditional lightweight sandwich structures have struggled to surpass solid structures in sound insulation performance. To this end, we propose an acoustic metamaterial structure with a sandwich configuration based on the re-entrant negative Poisson's ratio (NPR) structure and systematically investigate its sound transmission loss (STL) performance under incident plane wave conditions. We used the acoustic impedance tube method to experimentally study the sound insulation performance of the re-entrant NPR sandwich structure under free boundary conditions, and then established an acoustic analysis simulation model based on COMSOL Multiphysics software, which verified that the results obtained by the experiment and the numerical simulation were in good agreement. The results show that the sandwich structure exhibits excellent sound transmission loss performance in the studied frequency range (250-4000 Hz), and the overall sound insulation performance exceeds the curve of the mass theorem, basically achieving more than 20 dB when the sandwich thickness is 2 cm. Finally, we conduct parametric studies to establish a correlation between the geometric design of NPR sandwich structures and their sound transmission loss performance. The research shows that the changes of the length of the ribs, the distance from the ribs to the center of the unit, and the length of the upper wall and the lower wall have a significant impact on the sound insulation performance of the re-entrant NPR sandwich structure, while the change of the wall thickness basically will not affect the sound insulation performance of the sandwich structure. This research can provide practical ideas for the engineering application of noise suppression designs of lightweight structures.

Rectification of Sabah Stilt House Using Shear Wall Subjected to Earthquake

A moderate earthquake with 6.0-magnitude hit Sabah in 2015 especially in Ranau, Sabah has been labelled as one of the most powerful earthquakes ever in Malaysia. Numerous buildings in Sabah have become defective with the severity level of damages as absolute (non-repairable) in the RC beam-column joints and soft-storey structures. Seismic design and construction requirements were not considered in most buildings in Sabah. Hence, this research is to investigate how to mitigate the effect of earthquake on the low-rise building using a more practical and economical method. A stilt house model is developed using ABAQUS software to determine the behaviour of the stilt, low-rise building subjected to earthquake by constructing shear wall at the short columns support. There are 4 models constructed namely, frame model without shear wall (W1), with shear wall of 100mm (W2), 300mm (W3) and 500mm (W4). The results of seismic response are evaluated and compared. Different length of shear wall affects the displacement and stress of the frame model. As shear wall length increases, the displacement, stress at columns and stress at walls decreases. Thus, adding a shear wall can be used to retrofit stilt houses and a credible way to mitigate damage due to earthquake load for new houses along hill slopes

Investigation laboratory of the effect of increase of the height of the side wall on the performance of nonlinear weirs

ABSTRACT Nonlinear weirs offer a relatively high discharge capacity under low water loads. Their efficiency, however, is decreased at high water loads due to the submergence of the weir outlet key. In the present study, sloping parapet walls with the heights of 2, 4, and 6 cm and lengths of 60 and 30 cm were added to trapezoidal labyrinth weir and piano-key weirs in order to reduce the submergence at the weir inlet. The experiments were conducted in a test flume with a length of 7 m and a width and height of 0.6 m. Results of this study suggested that addition of the sloping parapet walls could reduce discharge coefficient by at least 10% and 13% in Piano-Key Weirs and labyrinth weirs respectively as compared to the control cases. Also, after addition of the parapet walls, Piano-Key Weir outperformed labyrinth weir by up to 19% in terms of the discharge coefficient. The highest efficiency of parapet wall for Piano-Key Weirs was found to be corresponding to parapet wall length and height of 30 cm and 2 cm respectively which differed from that of labyrinth weir of the same parapet wall dimensions by 14%. In fact, the addition of the parapet walls to the labyrinth and piano-key weirs increases the efficiency at high discharges by up to 40%.

Optimization analysis of variable gradient structures with shape memory characteristics in zero poisson’s ratio metamaterials

Mechanical metamaterials can achieve fantastic properties fabricated using artificial structural design. In this study, shape memory polymers (SMP) were combined to design variable gradient zero Poisson ratio mechanical metamaterials and 3D printing was used to fabricate complex structures. The shape memory performance of these structures was investigated by conducting simulation calculations to analyze the variations of zero Poisson’s ratio structures with different wall thicknesses, cell internal angles, and inclined wall length gradients. Through the analysis of structural dimension factors, it is concluded that the structures with smaller wall thickness and intracellular angle exhibit better shape memory performance. In order to further enhance the shape memory performance, several models with identical wall thickness and internal angles were designed to investigate the influence of inclined wall length gradients on shape memory characteristics, leading to the identification of optimal gradient structures. Finally, thermal cycling experiments were conducted on samples to validate the accuracy of the simulation results. The investigation of shape memory recovery characteristics in variable gradient zero Poisson’s ratio structures provides new insight and method for the optimization design and application of smart materials in mechanical metamaterial structures.

Dynamic response of the hybrid honeycomb sandwich panel with zero Poisson’s ratio under low-speed impact

The dynamic response of the hybrid honeycomb sandwich panel under low-speed impact is studied. According to Hamilton’s principle and first-order shear deformation theory, the motion equation of the hybrid honeycomb sandwich panel is deduced. Then the Navier method and Duhamel’s integral are used to solve the vibration displacement of panels. Besides, the mass-spring (MS) model is used to calculate the contact force between the honeycomb sandwich panel and the impactor. The results of this model are compared with those of Abaqus and published studies, which verifies the feasibility of the theoretical model in this paper. Based on the developed theoretical model, the influences of the unit cell angle, cell wall length, cell wall thickness, core layer height and impact speed on the dynamic response of sandwich panels have been studied. The results show that under the same low-speed impact, the maximum lateral displacement of hybrid sandwich panels was 11.65% smaller than that of conventional sandwich panels when honeycomb parameter θ = 60°, and was 15.45% when honeycomb parameter The energy absorption character of the hybrid honeycomb sandwich panel are better than those of the traditional hexagonal honeycomb sandwich panel and the concave hexagonal honeycomb sandwich panel.

A novel design method of circular sandwich panels with gradient continuous controllable core based on space-filling design and 2D-Voronoi method

In this paper, a novel method based on the space-filling design and 2D Voronoi method was proposed to design the in-plane gradient continuous controllable honeycomb (GCCH) structures. Low-velocity impact tests were carried out using the sandwich panels with GCCH core layers, which were all made of Aluminium alloy material and fabricated with the wire-cut machine. A concise theoretical solution for loading capacity and denting profile was developed and verified. Three-dimensional finite element models were implemented in ABAQUS/Explicit to model sandwich panels.The FE models were validated with experimental results and, subsequently, the simulation results were further extended to study the impact response and energy absorption characteristics. Results show that the method proposed in this work was effective to design multi-cell structures with graded mechanical properties in the radius direction and approximately homogeneous in the circumferential direction by controlling the distribution of the sites. Sandwich panels with GCCH core layers had better energy absorption properties compared with sandwich panels whose core layers were hexagonal honeycomb with similar cell wall lengths.

A novel generalized sandwich-type replacement beam for static analysis of tall buildings: Inclusion of local shear deformation of walls

As the length of the shear walls increases, local shear deformation leads to increased error when using classical continuum models for static structural analysis of tall buildings. In this paper, a novel continuous beam of the generalized sandwich type is proposed for the structural analysis of tall buildings that have shear walls of significant length as lateral bracing systems. The proposed continuous beam includes in its formulation an additional kinematic field of rotation due to the local shear deformation of the walls and results from the series coupling of a classic sandwich beam and a shear beam. The equilibrium equations, the constitutive laws, and the boundary conditions of the continuous model are obtained with a variational approach using the Hamilton principle on the relevant Lagrange function. A system of three coupled differential equations leading to sixth-order differential equation and six boundary conditions are obtained. Two closed-form analytical methods are proposed for uniform-height tall buildings. For the case of buildings with variable properties along their height, a numerical method of the modified transfer matrix type is proposed, which is directly derived from the analytical method and avoids the need to calculate the inverse of the classical zero transfer matrix method. The numerical results show the validation of the continuous model and the proposed solution methods. In addition, a parametric analysis of 352 buildings was performed to demonstrate the superiority of the continuous model and the proposed solution methods.

Study on axial compression behaviors of dense-steel-column sandwich wall

As an innovative structural system, the modular steel structure building has been widely used. This paper presents a new modular structure called dense-steel-column sandwich wall. Eight walls were subjected to axial compression tests to investigate the effects of column section size and diagonal brace on the axial compression behavior of the wall. The results show that the bearing capacity can be improved by setting diagonal brace or increasing the column width, additionally, diagonal brace can improve the deformation ability of the wall. The wall tends to change from global instability failure to local instability failure as the column width increases. Based on the test results, refined finite element analysis models were established and compared with the tests, followed by multi-parameter analysis. The failure mode and peak load of the specimens obtained by numerical simulation closely matched the test results, showing the correctness of the finite element model. Moreover, the results of finite element analysis demonstrate that increasing of wall length to column spacing ratio, column thickness, and decreasing of column slenderness ratio can significantly improve the bearing capacity and axial compressive stiffness of the wall. Finally, the axial compression capacity calculation formulas were put forward, and the research findings can provide a reference for the engineering application of the dense-steel-column sandwich wall.

Experimental study on displacement capacity of reinforced concrete walls with varying cross-sectional slenderness

The utilization of thinner and more slender walls in the design of reinforced concrete shear wall structures has become increasingly popular in Chile and other countries. However, while this approach can lead to increased wall strength if the wall length is increased, it may also result in lateral instability. This study presents experimental results obtained from testing walls with variations in cross-sectional slenderness and their impact on out-of-plane lateral instability, while maintaining wall height, information that in the literature is scarce. Three slender walls were constructed with different cross-sectional dimensions: 160 mm by 900 mm (M1), 100 mm by 900 mm (M2), and 100 mm by 1350 mm (M3). These walls were subjected to a constant axial load and a cyclic lateral load. It was found that the strength of each specimen was consistent with the variation in its cross-sectional dimensions, while maintaining the distribution of steel reinforcement. However, walls with reduced thickness and increased length showed evidence of both local and global lateral instability. Specimen M1 presented concrete crushing, longitudinal bar bucking and fracture, whereas M2 presented a decreased stable confined portion of the wall compared to wall M1, yielding local instability. Wall M3, on the other hand, with a larger wall length, presented larger cracks that favored an unstable out-of-plane behavior of the entire wall section, leading to a sudden strength loss due to its inability to maintain the axial load. As a result, the drift capacity of these walls was found to decrease from 4.2% to 3% with thickness reduction, and to 1.2% with thickness reduction and increased length.

Regional motion of the AV-plane is related to the cardiac anatomy and deformation of the AV-plane. Data from the HUNT Study.

The study examines global and regional systolic shortening of the left (LV) and right ventricle (RV) in 1266 individuals without evidence of heart disease in the third wave of the HUNT study. Regional mitral annular systolic displacement (MAPSE) was 1.5 cm in the septum and anterior walls, 1.6 cm in the lateral wall and 1.7 cm in the inferior wall, global mean 1.6 cm. Peak systolic velocity S' was 8.0, 8.3, 8.8 and 8.6 cm/s in the same walls (global mean 8.7 cm/s). All measures of LV longitudinal shortening correlated, mean MAPSE and S' also correlated with stroke volume (SV) and ejection fraction (EF). Global longitudinal strain by either method correlated with MAPSE, S' and EF, but not with SV, reflecting a systematic difference. S' and MAPSE correlated with early annular diastolic velocity (e'), reflecting that e' is the recoil from systole. Mean displacement was 2.8 (0.5) cm in the tricuspid annulus (TAPSE). Normal values by age and sex are provided. Both TAPSE and S' were lower in women, where body size explained the sex difference. Normalization of MAPSE and S' for wall length reduced intra-individual variation of displacement and velocity by 80 - 90%, showing regional MAPSE to be related to LV wall length, and that longitudinal wall strain was relatively uniform. Displacement and S' were lowest in the septum and highest in the left and right free walls, shows systolic bending of the AV-plane into a U-shape, relating to the total cardiac volume changes during the heart cycle. This article is protected by copyright. All rights reserved.

A study of the effect of curvature and pressure gradient on aerodynamics performance and turbulence structure of S-shaped compressor transition duct

ABSTRACT The overall performance of the high-pressure compressor in a turbofan engine entirely depends on the flow supplied by the upstream transition duct. A robust and efficient design of the transition duct conveys a highly uniform flow with minimum pressure loss. The present study aimed to determine the effect of adverse pressure gradient and curvature on the flow of the compressor duct. The results suggest that the outer wall curvature causes a significant decrease in from +0.19 to −0.6, and as a result, 75% length of the outer wall is suspended in the favourable pressure gradient. On the contrary, it increases from −0.54 to +0.14 along the inner wall. It implies that most of the inner wall lies in the adverse pressure gradient; consequently, the turbulence structure, mean flow behaviour, and Reynolds stresses are considerably modified. The presence of a strong adverse pressure gradient significantly enhances turbulence quantities along the inner wall. Additionally, the boundary layer parameters grow relatively thicker along the inner wall than on the outer wall. As a result, a considerable increase in the shape parameter (H = 2.12) is obtained.

Regenerative endodontic treatment of immature permanent teeth after mechanical instrumentation with XP-Endo Finisher.

The traditional treatment of immature permanent teeth with necrotic pulp involves creating an apical barrier by using calcium hydroxide or an MTA plug for an extended period of time. A novel therapeutic approach called regenerative endodontic procedures (REP) is used to allow root development to continue.

Effect of wave height on harbor wall height in coastal waters using computational fluid dynamics

An essential aspect of the sustainable design of harbor walls is the determination of the design wave condition. It is predicted by utilizing severe wave conditions from the past 10 to 20 years. The tourism harbor in Central Maluku, Indonesia, is located where extreme wave conditions occur. Therefore, this research studies the wave height before and after constructing a harbor wall in the harbor area. The wave height was simulated using numerical modelling. The methodology was performed by using the coastal modelling software of the CFD model. The result shows the highest design wave height values of 0.5 m, 0.75 m, and 1 m in the direction from the southeast to harbor height 1 m. The simulation results show that the wave height is 1.5 m and the harbor height is still safe. Further study is needed to simulate the extension of harbor wall length to meet the criteria for wave height in the harbor basin.

Insights into spermatogenesis in the migratory locust, Locusta migratoria (Linnaeus, 1758) (Orthoptera: Acrididae), following histological and ultrastructural features of the testis

The migratory locust, Locusta migratoria (Linnaeus, 1758), is one of the most destructive agricultural pests globally, and this species is particularly localized in several regions of Egypt. However, so far, very little attention has been paid to the characteristics of the testes. Furthermore, spermatogenesis requires careful analysis to characterize and track developmental episodes. We thus investigated, for the first time, the histological and ultrastructural properties of the testis in L. migratoria employing a light microscope, a scanning electron microscope (SEM), and a transmission electron microscope (TEM). Our results revealed that the testis comprises several follicles, emerging with distinct outer surface wrinkle patterns for each follicle throughout the length of the follicular wall. Furthermore, histological examination of the follicles showed that each has three developmental zones. Each zone has cysts with characteristic spermatogenic elements, beginning with the spermatogonia at the distal end of each follicle and ending with the spermatozoa at the proximal end. Moreover, spermatozoa are arranged in spermatozoa bundles called spermatodesms. Overall, this research provides novel insights into the structure of the testes of L. migratoria, which will significantly contribute to formulating effective pesticides against locusts.

Modeling analysis of non-azeotropic and immiscible binary mixed vapors condensation under natural convection

A calculation model describing the condensation heat and mass transfer process of non-azeotropic immiscible binary mixed vapors on the vertical wall under natural convection conditions was developed in this study. The model includes the two possible condensation modes of mixed vapors on the vertical wall as well as the conversion conditions between them. Cyclohexane and water were used as non-azeotropic immiscible mixtures. The reliability of the model was verified first, then the influence of vapor mass concentration and wall subcooling on the condensation mode and heat and mass transfer of the mixed vapors were analyzed. The results showed that the maximum deviation between the model results and the experimental results was less than 21%, confirming that the model was reliable. When the mixed vapors mass concentration was nearly eutectic or the wall subcooling was large, the condensation Mode B (Co-condensation) was more likely to occur than Mode A (Single condensation) due to the decrease in vapor-liquid interface temperature. The condensation mode may change from B to A as the wall length increased along the gravity direction of the condensation wall, and the condensation heat transfer coefficient and mass flux decreased. The thermal resistance of the vapor and liquid phases during condensation was also calculated. In Mode A, regulation of the thermal resistance of the vapor-liquid two phases can be achieved by adjusting the vertical length of the condensation wall and the vapor mass concentration. Condensation Mode B can only be realized by adjusting the wall subcooling. The results of this work may provide a workable reference for condensation heat transfer and enhancement of non-azeotropic immiscible mixed vapors in industrial environments.

Electrokinetic ion enrichment in asymmetric charged nanochannels

Artificial bionic nanochannels have attracted wide attention and successfully used in various fields. In this work, a novel nanochannel with asymmetric surface charge is proposed to investigate the ion enrichment effect. The results show that the proposed nanochannel has excellent ion enrichment performance and the obtained ion enrichment ratio is up to 1500 when the ion concentration is 0.01 mM, which is much higher than precedent researches typically ranging from tens to hundreds. Besides, we found that the forward voltage bias will produce ions enrichment and the reverse voltage bias will produce ions depletion. The ion enrichment ratio is higher at the larger voltage bias, absolute surface charge density and smaller nanochannel height. In addition, the ion enrichment performance is more sensitive to the change of charged wall length and not sensitive to the change of uncharged wall length. The research report offers important information and instructions for the design and optimum on ion enrichment performance.

A semicircular wall for harvesting wind energy from vortex-induced vibration and galloping

Harvesting energy from ambient air is crucial for sustaining the operation of low-power electronic devices under autonomous conditions. In this study, a specially designed semicircular wall with a thin splitter plate was proposed, behind which the wake exhibited evolution from vortex-induced vibration (VIV) to galloping. Benefiting from this peculiar flow pattern, a piezoelectric energy harvester placed in the cylinder wake can perform well under variable wind speed conditions. The effects of aspect ratio (α) and nondimensional afterbody length (l*) of the semicircular wall on the energy harvester's performance were experimentally examined. The results showed that the aspect ratio was highly correlated with the modes of flow-induced vibrations. When 2/3 ≤ α ≤ 4/3 and l* = 1/2, the harvester experienced VIV, transition from VIV to galloping, and galloping with a continuously increasing wind speed. Frequency analysis further revealed that the resonance force and lift instability caused by vortex shedding of the semicircular wall might arise almost simultaneously, with the latter serving as the driving factor in the evolution from VIV to galloping. It is also found that the harvester operated efficiently at wind speeds of 1.0–12.0 m/s, and an appropriate nondimensional afterbody length was required to achieve high-level power outputs. These findings provide beneficial suggestions for developing the coupled VIV-galloping energy harvesters.

Role of slip in the stability of viscoelastic liquid flow through a channel

For a horizontal channel flow of a weakly viscoelastic liquid that follows the constitutive model of Walters’ liquid B′′, a linear stability analysis is performed when the channel walls are slippery. In this case, the viscoelastic channel flow is driven by the streamwise pressure gradient. We explore the primary instability for a symmetric slip flow with the same slip length of the channel walls, an asymmetric slip flow with different slip lengths of the channel walls, and an analogy to the Poiseuille–Couette flow of a viscoelastic liquid with a slip effect on the lower wall but no slip effect on the upper wall. We observe that the viscoelastic parameter shows a destabilizing impact, but the slip length shows a stabilizing impact on the most unstable shear mode in all three flow configurations. Moreover, the Poiseuille and Poiseuille–Couette flows for the viscoelastic liquid are linearly more unstable to infinitesimal disturbances than those of the Newtonian liquid. As a result, wall velocity needs to be higher than in the Newtonian liquid to stabilize the viscoelastic Poiseuille–Couette flow. Using the asymptotic analysis, we have determined the critical value of the slip length, or equivalently, the critical value of the lower wall velocity, above which the asymmetric slip flow and the Poiseuille–Couette flow of the viscoelastic liquid are permanently stable to infinitesimal disturbances.