• Title/Summary/Keyword: External load

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Evaluating performance of the post-tensioned tapered steel beams with shape memory alloy tendons

  • Hosseinnejad, Hossein;Lotfollahi-Yaghin, Mohammad Ali;Hosseinzadeh, Yousef;Maleki, Ahmad
    • Earthquakes and Structures
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    • v.23 no.3
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    • pp.221-229
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    • 2022
  • The external post-tension technique is one of the best strengthening methods for reinforcement and improvement of the various steel structures and substructure components such as beams. In the present work, the load carrying capacity of the post-tensioned tapered steel beams with external shape memory alloy (SMA) tendons are studied. 3D nonlinear finite element method with ABAQUS software is used to determine the effects of the increase in the flexural strength, and the improvement of the load carrying capacity. The effect of the different parameters, such as geometrical characteristics and the post-tension force applied to the tendons are also studied in this research. The results reveal that the external post-tension with SMA tendons in comparison with the steel tendons causes a significant improvement of the loading capacity. According to this, using SMA tendon for the reinforcement of the tapered beams causes a decrease in weight of these structures and as a consequence causes economic benefits for their application. This method can be used extensively for steel beams due to low executive costs and simplicity of the operation for post-tension.

Fiber method analysis of rc beam retrofitted with turnbuckle external post-tensioning

  • Lejano, Bernardo A.
    • Computers and Concrete
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    • v.17 no.1
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    • pp.67-86
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    • 2016
  • Strengthening as well as correcting unsightly deflections of reinforced concrete (RC) beam may be accomplished by retrofitting. An innovative way to do this retrofitting that is proposed in this study utilizes turnbuckle to apply external post-tensioning. This Turnbuckle External Post-Tensioning (T-EPT) was experimentally proven to improve the serviceability and load carrying capacity of reinforced concrete beams. The T-EPT system comprises a braced steel frame and a turnbuckle mechanism to provide the prestressing force. To further develop the T-EPT, this research aims to develop a numerical scheme to analyze the structural performance of reinforced concrete beams with this kind of retrofitting. The fiber method analysis was used as the numerical scheme. The fiber method is a simplified finite element method that is used in this study to predict the elastic and inelastic behavior of a reinforced concrete beam. With this, parametric study was conducted so that the effective setup of doing the T-EPT retrofitting may be determined. Different T-EPT configurations were investigated and their effectiveness evaluated. Overall, the T-EPT was effective in improving the serviceability condition and load carrying capacity of reinforced concrete beam.

An Analysis of Near-Net Forging of External Spline by an Upper Bound Elemental Technique (상계요소법에 의한 External Spline의 Near-Net 단조해석)

  • 양정호
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1996.04a
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    • pp.206-211
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    • 1996
  • Closed-die forging of external spine is analysed using an upper bound elemental technique. The kinematically admissible velocity field for three-dimensional deformation in forging of the external spine with trapezoidal teeth was obtained. The upper bound to the deforming load necessary and the the deformed configurations are predicted using integration of the formulation of energy expressions which were obtained from B(upset forging method) were considerd in the present analysis and the theoretical results compared with experimental ones Experiments were carried out on plasticine as model material at room temperature where talcum powder was used as a lubricant. The present investigation revealed that the analytical method B predicts a reducet forging load and improved configuration better than method A for the forged products.

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New Statistical Pattern Recognition Technology for Condition Assessment of Cable-stayed Bridge on Earthquake Load (지진하중을 받는 사장교의 상태평가를 위한 새로운 통계적 패턴 인식 기술)

  • Heo, Gwanghee;Kim, Chunggil
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.34 no.3
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    • pp.747-754
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    • 2014
  • In spite of its usefulness for health monitoring of structures on steady external load, the statistical pattern recognition technology (SPRT), based on Mahalanobis distance theory (MDT), is not good enough for the health monitoring of structures on large variability external load like earthquake. Damage is usually determined by the difference between the average measured value of undamaged structure and the measure value of damaged one. So when external variability gets larger, the difference gets bigger along, which is thus easily mistaken for a damage. This paper aims to overcome the problem and develop an improved Mahalanobis distance theory (IMDT), that is, a SPRT with revised MDT in order to decrease external variability so that we will be able to continue to monitor the structure on uncertain external variability. This method is experimentally tested to see if it precisely evaluates the health of a cable-stayed bridge on each general random load and earthquake load. As a result, the IMDT is found to be valid in locating structural damage made by damaged cables by means of data from undamaged cables. So it is proved to be effectively applicable to the health monitoring of bridges on external load of variability.

Analysis of the Protective Distance of Low-Voltage Surge Protective Device(SPD) to Equipment (저압용 서지 보호 장치(SPD)의 보호 거리 해석)

  • Lee, Jung-Woo;Oh, Yong-Taek
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.26 no.4
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    • pp.28-34
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    • 2012
  • Installing surge protection devices for a low-voltage system is important to ensure the survival of electric or electronic devices and systems. If surge protection devices (SPD) are installed without consideration of the concept of lightning protection zones, the equipment to be protected might be damaged despite the correct energy coordination of SPDs. This damage is induced by the reflection phenomena on the cable connecting an external SPD and the load protected. These reflection phenomena depend on the characteristics of the output of the external SPD, the input of the loads, and the cables between the load and the external SPD. Therefore, the SPD has an effective protection distance under the condition of the specific load and the specific voltage protection level of SPD. In this paper, PSCAD/EMTDC software is used to simulate the residual voltage characteristics of SPD Entering the low-voltage device. And by applying a certain voltage level, the effective protection distances of SPD were analyzed according to the each load and length of connecting cable, and the effectiveness of SPD were verified.

Synchronous Control of an Asymmetrical Dual Redundant EHA (비대칭 이중화 EHA의 동기 제어)

  • Lee, Seong Ryeol;Hong, Yeh Sun
    • Journal of Drive and Control
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    • v.13 no.2
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    • pp.1-9
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    • 2016
  • In this paper, an elementary force fighting problem was investigated. The problem is encountered when a double-rod type EHA(electro-hydrostatic actuator) is combined with a single-rod type EHA to build a redundant actuator system with synchronized motion. When the rod-side chambers of the two different types of EHAs have the same effective piston areas and are simultaneously pressurized by an external load, the two EHAs behave identically, sharing the external load equally. However, when the piston head-side chamber of the single rod type EHA, having a larger effective area than the rod-side chamber, is pressurized by the external load, an abnormal force fighting between the two EHAs occurs, unless their pump speeds are properly decoupled. In this study, the output drive forces of each EHA were obtained from the cylinder pressure signals and applied to the position control for each EHA to maintain the balance between their pump speeds. Adding minor force difference feedback loops to the position control, the force fighting phenomena could be eliminated and steady state synchronization errors were reduced. The power consumption of the pumps also could be remarkably reduced, avoiding unnecessarily high load pressures to the pumps.

A Study on the Effects of Wind Load of Membrane Roof Structures according to External Form (외형에 따른 지붕 막구조물의 풍하중 영향 고찰)

  • Ko, Kwang-Woong;Jang, Myung-Ho;Lee, Jang-Bog;Sur, Sam-Yeol
    • Proceeding of KASS Symposium
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    • 2008.05a
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    • pp.15-18
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    • 2008
  • A Spatial structure, having a curvature with a curved surface, is an extremely efficient mechanical creation considering the external load. It is resisted the out-of-plane direction load by in-plane forces using the structure's curvature. Spatial Structures include many types of structures, such as: space frames or grids; cable-and-strut and tensegrity; air-supported or air-inflated; self-erecting and deployable; cable net; tension membrane; lightweight geodesic domes; folded plates; and thin shells. Membrane structures, a kind of lightweight soft structural system, are used for spatial structures. It is very important that effects by wind load than seismic and dead load. And, wind load is different by surrounding and shape of building In this study, we analyze the results of design wind load and wind tunnel tests about the 2 stadiums which are constructed on sensitive sites by effect of wind loads.

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Elastic solutions due to a time-harmonic point load in isotropic multi-layered media

  • Lin, Gao;Zhang, Pengchong;Liu, Jun;Wang, Wenyuan
    • Structural Engineering and Mechanics
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    • v.57 no.2
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    • pp.327-355
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    • 2016
  • A new analytical derivation of the elastodynamic point load solutions for an isotropic multi-layered half-space is presented by means of the precise integration method (PIM) and the approach of dual vector. The time-harmonic external load is prescribed either on the external boundary or in the interior of the solid medium. Starting with the axisymmetric governing motion equations in a cylindrical coordinate system, a second order ordinary differential matrix equation can be gained by making use of the Hankel integral transform. Employing the technique of dual vector, the second order ordinary differential matrix equation can be simplified into a first-order one. The approach of PIM is implemented to obtain the solutions of the ordinary differential matrix equation in the Hankel integral transform domain. The PIM is a highly accurate algorithm to solve sets of first-order ordinary differential equations and any desired accuracy of the dynamic point load solutions can be achieved. The numerical simulation is based on algebraic matrix operation. As a result, the computational effort is reduced to a great extent and the computation is unconditionally stable. Selected numerical trials are given to validate the accuracy and applicability of the proposed approach. More examples are discussed to portray the dependence of the load-displacement response on the isotropic parameters of the multi-layered media, the depth of external load and the frequency of excitation.

Structural Behavior of Concrete Girder Continuous Bridges Strengthened with External Tendons Considering the Efficiency at Negative Moment Region (부모멘트부의 효율성을 고려한 외부강선으로 보강된 콘크리트 거더 연속교의 거동)

  • Han, Man-Yop;Cho, Byeong-Du;Jeon, Se-Jin
    • Journal of the Korea Concrete Institute
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    • v.25 no.5
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    • pp.555-564
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    • 2013
  • An effective method was proposed in this study which can improve the strengthening effect of continuous girder bridges by external tendons. The improvement of the proposed strengthening method in comparison with conventional methods was analyzed by applying equivalent load concept. In order to verify the strengthening effect, the enhancement of load-carrying capacity achieved by external prestressing was investigated through the test of continuous beams that were or were not strengthened by the external prestressing. The continuous beams were fabricated by making the deck slab continuous according to general construction practice of an actual concrete girder bridge. The test results showed that the deflections and strains of the strengthened beam were significantly reduced when comparing with those of the non-strengthened beam for the same level of external loads, and the stiffness of the member increased by strengthening. In particular, it was verified that the proposed method can effectively reduce the tensile stresses of the deck caused by negative moment at the intermediate supports of a continuous bridge.

A Comparison of Gluteus Maximus Muscle and Biceps Femoris Muscle Thickness According to Weight Load during Prone Hip Extension with Knee Flexion Exercises (엎드려 무릎관절 굽힘 자세에서 엉덩관절 폄 동작 시 무게 부하 변화에 따른 큰볼기근과 넙다리두갈래근의 두께 비교)

  • Eun-Mi Jang;Da-Eun Jung
    • PNF and Movement
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    • v.21 no.3
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    • pp.309-317
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    • 2023
  • Purpose: This study set out to investigate the effects of prone hip extension with knee flexion (PHEKF) exercises according to external load on the thickness of the gluteus maximus (Gmax) and biceps femoris (BF). Methods: Twenty-three healthy men participated in this study. All subjects randomly practiced PHEKF under the burden of external loads created by sandbags (0 kg, 1 kg, and 2 kg). Rehabilitative ultrasound imaging (RUSI) was used to measure the thickness of the Gmax and BF during the PHEKF with different external loads. Results: The thickness of the Gmax was highest during the 2 kg resistance exercise and lowest at 0 kg. The thickness of the Gmax was significantly increased at 1 kg and 2 kg compared to 0 kg and significantly increased at from 1 kg to 2 kg (p < 0.05). The thickness of the biceps femoris was highest at 0 kg and lowest at 2 kg. The thickness of the biceps femoris muscle was significantly reduced at 1 kg and 2 kg compared to 0 kg (p < 0.05), but there was no significant difference between 1 kg and 2 kg (p > 0.05). Conclusion: The thickness of the Gmax was increased by applying PHEKF with a higher external load, whereas the muscle thickness of the biceps femoris decreased. These results suggest that the application of external loads during PHEKF exercises may be an effective method for selective strengthening of the Gmax.