Maximum Horizontal Load Research Articles

A novel stick-slip piezoelectric actuator is developed based on a parallelogram flexible drive mechanism to minimize shear force

A piezoelectric actuator utilizing a parallelogram flexible mechanism is proposed. This actuator harnesses the parasitic motion generated by a parallelogram driven by a piezoelectric element. It differs from existing actuation mechanisms based on a similar principle in that the piezoelectric stack is positioned on the outside of the parallelogram flexible mechanism, thus protecting it from shear forces. Finite element simulations and experiments confirm this. The analysis was conducted using theoretical analysis and finite element simulation. The optimal drive angle for the parallelogram flexible mechanism was determined through finite element simulation. Additionally, a prototype actuator and an experimental measurement system were developed to assess the operational performance of the proposed piezoelectric actuator. When the driving frequency is 475 Hz and the locking force is 5 N, the motion of the actuator achieves a maximum speed of 5.65 mm s−1 and a maximum horizontal load of up to 113 g; when the input frequency is 1 Hz and the input minimum starting voltage is 8 V, the minimum displacement resolution is 30 nm. A comparative analysis of experimental results, theoretical calculations, and finite element simulation results demonstrates the feasibility of the structural design.

Study on mechanical properties of the cross arm-insulator system under strong wind load

High-voltage transmission tower-line systems in coastal areas are often affected by strong winds, which leads to structural damage to the towers. Detailed analysis of the damage mechanism of towers is very useful to ensure the safety and stability of the power system. This paper examines the mechanical properties of the cross-insulator structure under horizontal wind load, and then the load-carrying capacity and deformation performance were analyzed based on ABAQUS. The results show that the structure is stable under the load, and the main structure is basically in the elastic working stage with insignificant flexural and torsional effects. On the contrary, the local stress of the combined link rod connected with the insulator is large; the bending deformation characteristics of the combined link rod are obvious under the maximum horizontal load the insulator can withstand. This result can provide a reference for cross-arms structural safety design.

Achieving smooth motion and high-speed for piezoelectric stick-slip actuator based on the two-stage lever principle.

With the development of the precision manufacturing industry, actuators' performance requirements are increasingly demanding. However, stick-slip actuators still have the problems of backward motion and low motion speed at low frequencies. In this paper, to decrease the backward motion and achieve high speed at low frequencies, a linear piezoelectric stick-slip actuator is designed based on the two-stage lever principle. Theoretical and numerical investigations are used to optimize the flexible hinge of the stick-slip actuator. Experimental results indicate that the motion slider can achieve a smooth motion. The backward rate can even drop to 0. The maximum motion speed was 124.83 mm/s at 1600 Hz. The motion speed of the designed actuator was higher than that of previous stick-slip actuators at the same frequency. In addition, the load capacity of the prototype is tested. Based on different loads, the load matching is achieved by an auxiliary piezoelectric-stack, where the maximum horizontal load was 2.3 N. According to the comparison with previous actuators, the designed prototype can achieve high speed at low frequencies. Furthermore, the displacement curves show good smoothness. These characteristics will be helpful for the practical application of stick-slip piezoelectric actuators.

A bionic inertial piezoelectric actuator with improved frequency bandwidth

With features of simple structure and control, the inertial piezoelectric actuator is a promising type to achieve large working stroke and high positioning resolution. However, most of previously developed inertial piezoelectric actuators face the problems of low frequency bandwidth, motion speed, resolution as well as loading capacity, and thus require further improvement in comprehensive performances. For this purpose, inspired by the movement mode of frog’s hind legs during swimming, a bionic inertial piezoelectric actuator was proposed in this study. The bionic motion principle and structure analysis of the designed inertial actuator were discussed in detail, followed by testing its output performances. The experimental results showed that the frequency bandwidth of the designed inertial actuator had been significantly increased to be 275 Hz, and correspondingly, the maximum motion speed reached 1.218 mm/s. In addition, the positioning resolution was 0.217 µm and the maximum horizontal load and vertical load were 0.6 N and 17 N, respectively. Comparative analysis indicated that compared to many previously reported inertial actuators, the comprehensive performances of the proposed actuator were significantly improved, being beneficial to its practical applications.

The Structural Performance of Reinforced Concrete Members with Monolithic Non-Structural Walls under Static and Dynamic Loads

The required base shear and drift limit for post-disaster management buildings have increased in the Japanese Building Code following major seismic events. One method to satisfy these requirements for reinforced concrete frame buildings is to cast exterior non-structural concrete wall elements to be monolithic with frame elements, but without anchoring the longitudinal wall reinforcing. This provides additional stiffness and strength while limiting significant damage in the non-structural wall. In this study, the structural performances of such elements were evaluated using static and dynamic experimental tests. The result indicates that non-structural walls that were neither isolated by seismic slits nor anchored to the adjacent walls with longitudinal reinforcements experienced less damage and higher deformability compared with walls having seismic slits. The confinement reinforcing impact was not observed on the strength and drift capacity of the beam member, owing to the large number of transverse reinforcements. However, the confinements limited the damage and nearly prevented concrete crushing. The maximum horizontal load of the specimen could be predicted using cross-sectional analysis, and the authors propose a simple equation to predict it with sufficient accuracy.

Horizontal Loading Performance of Offshore Wind Turbine Pile Foundation Based on DPP-BOTDA

Offshore wind power is becoming attractive in the wind-power field. With the rapid development of wind-power technology, high-power wind turbines have been implemented in practice. However, the increase in the length of the wind turbine blade causes the pile foundation to withstand a prone overturning moment. For overcoming the problems of traditional sensing technology and meeting the monitoring requirements of pile foundations, a 20 cm spatial resolution differential pulse pair Brillouin optical time-domain analysis (DPP-BOTDA) technique is used to measure a 69 m long offshore wind turbine pile under horizontal loading. From the distributed strain data collected in the test, the maximum stress location of the long pile under the horizontal load can be obtained. By analyzing the load and maximum strain (F-εmax) curve, the horizontal bearing capacity of the pile foundation can exceed 900 kN, which is the maximum horizontal load of the design. The distributed displacement calculation method based on distributed strain data is proposed, according to the force characteristics of steel pipe piles. By comparing the calculated displacement data with the measured data by the dial indicators, the mean absolute percentage error (MAPE) value is only 0.03548. Results show that the 20 cm spatial resolution DPP-BOTDA technology is very suitable for the bearing capacity test of offshore wind turbine steel pipe pile foundations.

Actively controlling the contact force of a stick-slip piezoelectric linear actuator by a composite flexible hinge

Stick-slip piezoelectric actuators have been widely employed in those fields where both large working stroke and high positioning accuracy are required. However, the problems of backward motion and relatively low load capability limit their applications, and these two problems are usually contradictory. Attempted to solve these two problems at the same time, in this study, a composite flexible hinge was designed to actively control the contact force between the driving foot and the slider of a stick-slip piezo-driven linear actuator. To confirm the validity, a prototype actuator was designed and fabricated. The dimensions of the actuator in X, Y and Z directions are about 80 mm, 60 mm and 20 mm, respectively. The output characteristics of the actuator were evaluated by experiments. The results showed that without the active control of the contact force, the maximum speed being free of external load were 1.39 and 2.18 mm/s when the driving frequencies were 100 and 200 Hz, respectively. Correspondingly, the maximum horizontal loads of the actuator were 25 g and 50 g, respectively. However, with the active control of the contact force, the maximum speed were 1.74 and 4.1 mm/s under the driving frequency of 100 and 370 Hz, respectively. Moreover, the maximum horizontal loads under 100 Hz and 200 Hz were improved to be 40 g and 70 g, respectively.

Solitary wave impacts on vertical and overhanging near-coast structures

ABSTRACTIn this paper, we investigate short-duration solitary wave impacts on overhanging near-coast structures, which are represented here as rectangular blocks protruding out from a vertical wall. Wave transformation is computed for a variety of scenarios using the OpenFOAM variant IHFOAM. In agreement with previous studies, the largest pressures and loads occur when there is a violent impact with near-breaking or just-broken waves on the wall, causing a strong vertical jet. This condition most easily occurs with steep near-shore slopes. Maximum vertical loads on overhangs occur at significantly higher block elevations than are found for maximum horizontal loads. Overhang lengths have small effects on magnitudes of horizontal forces, but strongly increase positive uplift vertical loads. Although maximum instantaneous vertical loads can significantly exceed instantaneous horizontal loads, time-averaged vertical loads decrease rapidly with increasing averaging period while horizontal loads show more modest decreases; horizontal loads significantly exceed vertical loads for large averaging periods. This indicates that the pressure-impulse in the wall-generated vertical jets is much less than that arising from the horizontal solitary wave impacts.

In-plane behaviour of rammed earth under cyclic loading: Experimental testing and finite element modelling

The purpose of this paper is to numerically simulate the in-plane behaviour of rammed earth walls under cyclic shear-compression tests. The experimental testing allowed obtaining the maximum horizontal loads, the displacement capacity and the level of non-linear behaviour of the respective load-displacement relationships as well as the failure modes. The calibration of the numerical model (finite element method) was carried out based on the experimental results. Within this framework, a micro-modelling approach was considered. The behaviour of the rammed earth material was simulated using a total strain rotating crack model. A Mohr-Coulomb failure criterion was used to reproduce the behaviour of the interfaces between the layers.Although the numerical results achieved a satisfactory agreement with the experimental results a sensitivity analysis of the parameters involved was performed. The sensitivity analysis aimed at determining which parameters of the model have a significant impact in the model’s results.As expected the sensitivity analysis pointed out that the sliding failure occurrence is mainly influenced by two parameters of the interface elements: the interface tensile strength fit and the friction angle φ. Moreover the cohesion c and the layers thickness showed a limited effect on the shear behaviour. It should be noted that the results mentioned above are related to the cases where a significant level of vertical compressive stress σ is employed.

Fracture resistance of immature teeth filled with mineral trioxide aggregate, bioaggregate, and biodentine

Objective:The purpose of this study was to evaluate fracture resistance of teeth with immature apices treated with coronal placement of mineral trioxide aggregate (MTA), bioaggregate (BA), and Biodentine.Materials and Methods:Forty-one freshly extracted, single-rooted human premolar teeth were used for the study. At first, the root length was standardized to 9 mm. The crown-down technique was used for the preparation of the root canals using the rotary ProTaper system (Dentsply Maillefer, Ballaigues, Switzerland) of F3 (30). Peeso reamer no. 6 was stepped out from the apex to simulate an incompletely formed root. The prepared roots were randomly assigned to one control (n = 5) and three experimental (n = 12) groups, as described below. Group 1: White MTA (Angelus, Londrina, Brazil) was prepared as per the manufacturer's instructions and compacted into the root canal using MAP system (Dentsply Maillefer, Ballaigues, Switzerland) and condensed by pluggers (Angelus, Londrina, Brazil). Group 2: The canals were filled with DiaRoot-BA (DiaDent Group International, Canada). Group 3: Biodentine (Septodont, Saint Maur des Fosses, France) solution was mixed with the capsule powder and condensed using pluggers. Instron was used to determine the maximum horizontal load to fracture the tooth, placing the tip 3 mm incisal to the cementoenamel junction. Mean values of the fracture strength were compared by ANOVA followed by a post hoc test. P < 0.05 was considered statistically significant.Results:No significant difference was observed among the MTA, BA, and biodentine experimental groups.Conclusion:All the three materials tested, may be used as effective strengthening agents for immature teeth.

Estimation of Cascadia Local Tsunami Loads on Pacific Northwest Bridge Superstructures

Abstract The time histories of Cascadia Subduction Zone (CSZ) local tsunami horizontal and vertical loads and the overturning moment on four selected Oregon coastal bridges are computed for different load scenarios. These scenarios, containing the tsunami-free surface elevation and flow horizontal velocity components, are developed using various CSZ rupture models. One of the bridges is selected to evaluate the effect of various bridge geometry characteristics on the resultant tsunami loads. Maximum tsunami horizontal and downward vertical loads are found to occur approximately simultaneously when the tsunami flow reaches the landward side of the bridge cross section and overtops the barrier. A comparison between tsunami loads on a deck-girder bridge and a box-girder bridge under identical tsunami flow condition reveals that on box-girder bridges, (1) maximum horizontal loads are slightly larger, (2) downward vertical loads are smaller, and (3) uplift loads are significantly larger. It is shown that bridg...

Use of coffee (Coffea arabica) pulp for the production of briquettes and pellets for heat generation

Coffee bean (Coffea arabica) processing generates high amount of residues that are sources of environmental pollution. Therefore, an appropriate solution is needed. The objective of this study was to determine the potential of coffee pulp to produce briquettes and pellets. The study included pulp drying (using air, solar and hot air methods); the production of briquettes and pellets; the evaluation of their energy, physical and mechanical properties; and the evaluation of pellet quality using X-ray densitometry. The results showed that the pulp presented an initial moisture content of 90%, resulting in drying times of 699, 308 and 55 hours for air, solar and hot air drying, respectively, and the calorific values of the pellets and briquettes were 12,501 kJ kg-1 and 11,591 kJ kg-1, respectively. The ash content was 8.68% for the briquettes and 6.74% for the pellets. The density of the briquettes was 1,110 kg m-3, compared with 1,300 kg m-3 for the pellets. The apparent densities were 1,000 kg m-3 and 600 kg m-3 for the briquettes and pellets, respectively, and the water absorptions by the briquettes were 7.90% and 8.10% by the pellets. The maximum horizontal compression effort was 26.86 kg cm-2, measured in the pellets, compared with 4.52 kg cm-2 in the briquettes. The maximum horizontal load was 93.24 kg, measured in the briquettes, compared with 33.50 kg in the pellets. The value of the pellet durability test was 75.54%. X-ray densitometry showed that the pellet was uniform and a few cracks were observed on the pellet surface.

Results of pseudo-static tests with cyclic horizontal load on cast in situ sandwich squat concrete walls

In recent years, the seismic behaviour of structural systems composed of squat concrete walls has been the object of a renewed interest. This paper presents the results obtained in a large experimental campaign carried out as a joint effort between the University of Bologna and the Eucentre labs in Pavia. This effort aims at the assessment of the seismic performances of cellular structures composed of cast in situ sandwich squat concrete walls. In order to shed light upon the seismic behaviour (stiffness, strength, ductility, energy-dissipation) of such structures, a number of tests were performed upon two dimensional (3.0m by 3.0m) cast in situ sandwich squat concrete walls (with and without openings). In the experimental tests a number of horizontal in-plane loading cycles were imposed to the specimens, while the vertical load was kept constant. The results obtained have shown that the tested elements are characterized by: (i) high values of the maximum horizontal load applied to the structural systems (higher than the applied vertical load); (ii) residual bearing capacity with respect to the vertical loads, also when large lateral deformations are imposed; and (iii) high ductility.

体操競技における着地動作および着地荷重の解析

For the purpose of studying evaluation methods of shock absorption and stability of gymnastics landing mats, we did experiments of jumps and landings in men's gymnastic vault with five toy-level male gymnasts. The landing performances and landing loads on four common skills were examined by 3-D high-speed video analysis and measurement of landing load with force plate. Consequently, we clarified the ranges of and the correlations between the parameters, namely, velocity and angle of the center of gravity, angular velocity of spin and twist, and maximum vertical and, horizontal load, etc. in the landing. The results were as follows: 1) The verticla velocity of the center of gravity on landing averaged from -5.2 to -6.0m/s in each vaulting skill. The horizontal velocity (longitudinal direction) averaged from 3.4 to 3.9m/s. 2) The angular velocity of spin on landing averaged 310, 620, 550, 500deg/s in 'Handspring forward and salto forward tucked', 'Cuervo stretched', 'Kasamatsu stretched' and 'Kasamatsu stretched with 1 / 1 twist', respectively. The angular velocity of twist averaged 20, 90, 215, 265deg/s. 3) The landing angles were different according to the landing direction. Namely, the landing angle of' Cuervo stretched', 'Kasamatsu stretched' and 'Kasamatsu stretched with 1 / 1 twist' averaged from 50 to 55 deg, and that of' Handspring forward and salto forward tucked' averaged 70 deg. 4) The extents of maximum vertical load, in the four skills ranged from 5.0kN to 9.5kN and their weight-ratios ranged from 8 r to 15. The maximum horizontal load extents ranged from 0.8kN to 3.8kN and their weight-ratios ranged from 1.5 to 6.5.

軸力と交番曲げを受ける円形鋼管柱の弾塑性挙動

In order to study the effect of radius-thickness ratio (R/t) and axial force subjected to the top of column on the ultimate loading capacity and deformability of steel-pipe columns, monotonic and cyclic loading tests were conducted under a constant compressive axial load by using sixteen steel-pipe column models. In this study, two types of cyclic loading tests were adopted: 1) of increased amplitude at every new cycle, 2) of constant amplitude. Results obtained from this experiment are as follows: 1) under cyclic loading with increased amplitude, two types of local buckling: elephant foot bulge mode and diamond shaped mode, are generated near the base depending upon the radius-thickness ratio; 2) the effects of radius-thickness ratio and compressive axial load on the maximum horizontal load are small; and 3) the maximum horizontal load may not be affected by the loading types.

Analyses of horizontal loading tests on Franki piles : Delapierre, J; Dufour, C Ground Engng, V13, N2, March 1980, P32–37

The behaviour of single piles, subject to horizontal loading at the top, can be predicted by a method which uses A hyperbolic relationship between soil pressure and pile deflection. The method is applied to full-scale tests on two franki piles tested up to a maximum horizontal load of 25 t. Pile stiffness as measured in the laboratory was found to decrease rapidly with increasing bending moment. Two calculations were carried out to predict the pile performance, one with the real ei obtained from laboratory tests and another with a constant ei over the whole length. The calculations show that exact values of pile stress must be considered when horizontal loads become significant. (TRRL)

鉄骨ラーメンの弾塑性安定に関する実験的研究 : (その 1) 矩形断面部材より成る門形ラーメン

An experimental study are made of the effects of vertical loads on the behavior of steel portal frames subjected to horizontal loads. A specimen is composed of two similarly made miniature rigid portal frames, both being connected to each other in order to prevent lateral buckling of the frame. A frame is cut out by a machine from a mild steel plate stockwith 10mm thickness. The span and column height are chosen to be 200mm. The elastic flexural rigidity of the beam is either equal to or half that of the columns. 100, 50 and 30 are adopted as the ratios of the column height to its radius of gyration. Constant vertical loads are applied by hydraulic jacks at the tops of the columns symmetrically ; the loads are 0%, 10%, 20% and 40% of the elastic or the tangent modulus buckling load of a frame due to vertical loads only. A varying horizontal load is applied slowly by a testing machine to one direction of beam axis. It is observed that the shape of the horizontal load-displacement curve greaty depends on the magnitude of the vertical loads. The slope of the curve decreses as the horizontal load increases ; when the vertical loads are large the slope becomes negative after a certain displacement is reached. As the vertical loads increase, the maximum horizontal load decreases and the stability lilmit displacement also decreases. Experimental behavior is fairly well predicted by elastic-plastic analysis based on the true stress-strain relations of materials.