2009
41
1
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An AdaptiveRobust Control Approach for Trajectory Tracking of two 5 DOF Cooperating Robot Manipulators Moving a Rigid Payload
An AdaptiveRobust Control Approach for Trajectory Tracking of two 5 DOF Cooperating Robot Manipulators Moving a Rigid Payload
2
2
In this paper, a dual system consisting of two 5 DOF (RRRRR) robot manipulators is considered as a cooperative robotic system used to manipulate a rigid payload on a desired trajectory between two desired initial and end positions/orientations. The forward and inverse kinematic problems are first solved for the dual arm system. Then, dynamics of the system and the relations between forces/moments acting on the object by the robots, using different Jacobian matrices, are derived. The proposed control method is a position control approach; therefore, it does not need the complexity of measurement of forces and moments at the contact points. Simulation results are provided to illustrate the performance of the control algorithm. The robustness of the proposed control scheme is verified in the presence of disturbance and uncertainty.
1
In this paper, a dual system consisting of two 5 DOF (RRRRR) robot manipulators is considered as a cooperative robotic system used to manipulate a rigid payload on a desired trajectory between two desired initial and end positions/orientations. The forward and inverse kinematic problems are first solved for the dual arm system. Then, dynamics of the system and the relations between forces/moments acting on the object by the robots, using different Jacobian matrices, are derived. The proposed control method is a position control approach; therefore, it does not need the complexity of measurement of forces and moments at the contact points. Simulation results are provided to illustrate the performance of the control algorithm. The robustness of the proposed control scheme is verified in the presence of disturbance and uncertainty.
1
9


M.
Azadii
Iran


M.
Eghtesadii
Iran
Cooperative Robots –AdaptiveRobust Control Scheme –5 DOF robot manipulators– Trajectory Tracking
[[1] S. Hayati, "Hybrid positionforce control of multi arm cooperating robots", Proc. IEEE International conference on robotics and automation, pp. 8289, 1986. ##[2] M. H. Raibert, and J. J. Craig, "Hybrid position force control of manipulators", ASME Journal of dynamic system measurement, and control, vol. 108, No. 3, pp.126133, 1981. ##[3] O. Khatib, “Object manipulation in a multieffector robot system”, Robotics Research: the Fourth International Symposium, pp. 137144, 1988. ##[4] Y. Nakamura, K. Nagai and T. Yoshikawa, “Dynamic and stability in coordination of multiple robotic mechanism”, International Journal of Robotics Research, Vol. 8, No. 2, pp. 4461, 1989. ##[5] P. Hsu, “Control of multimanipulator systems – trajectory tracking, load distribution, internal force control, and decentralized architecture”, Proc. IEEE Int. Conference on Robotics and Automation, pp. 12341239, 1989. ##[6] M. Uchiyama and P. Dauchez, “A symmetric hybrid position/force control scheme for the coordination of two robots”, Proc. IEEE International Conference on Robotics and Automation, Vol. 1, pp. 350356, 1988. ##[7] K. Kreutz and A. Lokshin, “Load balancing and closed chain multiple arm control”, Proc. American Control Conference, pp. 21482155, 1988. ##[8] M. Itoh, T. Murakami and K. Ohnisni, “Decentralized control of cooperative manipulators based on virtual force transmission algorithm”, Proceedings of 1999 IEEE conference, pp. 874–889, USA: Kohala CoastIsland of Havai, 1999.##]
Proposing a 2D Dynamical Model for Investigating the parameters Affecting Whiplash Injuries
Proposing a 2D Dynamical Model for Investigating the parameters Affecting Whiplash Injuries
2
2
This paper proposes a 2D dynamical model for evaluating parameters affecting whiplash. In fact a four segment dynamical model is developed in the sagittal plane for the analysis. The model response is validated using the existing experimental data and is shown to simulate the "SShape" and "initial upward ramping" kinematics of the cervical spine and the resulting dynamics observed in human and cadaver experiments. The model is then used to evaluate the effects of parameters such as velocity change between rear vehicle and the target vehicle (), head/head restraint separation (backset) and the awareness of occupant on the whiplash injuries. It is shown that the proposed model can simulate whiplash phenomena very well; therefore it is a suitable alternative for other existing models.
1
This paper proposes a 2D dynamical model for evaluating parameters affecting whiplash. In fact a four segment dynamical model is developed in the sagittal plane for the analysis. The model response is validated using the existing experimental data and is shown to simulate the "SShape" and "initial upward ramping" kinematics of the cervical spine and the resulting dynamics observed in human and cadaver experiments. The model is then used to evaluate the effects of parameters such as velocity change between rear vehicle and the target vehicle (), head/head restraint separation (backset) and the awareness of occupant on the whiplash injuries. It is shown that the proposed model can simulate whiplash phenomena very well; therefore it is a suitable alternative for other existing models.
11
16


Seyed Mohammad
Rajaai
Iran


Mohammad H
Farahani
Iran
Whiplash injuries
Dynamic model
Adams
Backset
Velocity change
Awareness
[[1] Lawrence, S., Nordhoff, Jr., Motor Vehicle Collision Injuries, Biomechanics, Diagnosis and Management. Pleasanton California, Second edition, Jones and Bartlett publishers, 2005. ##[2] Kettler, A., Fruth, K., Claes, L., Wike, H.J., Influence of the crash pulse shape on the peak loading and the injury tolerance levels of the neck in invitro low speed side collisions. Journal of biomechanics 2005, pp. 5158 ##[3] Koch V., Nygern, M., Tingvall, C., Impairement Pattern in Passengers in crashes. A follow up of injuries resulting in long term consequences, Proceedings of the 14th International Technical Conference on the Enhanced Safety of Vehicles, Munich, Germany, 1994, pp. 779781 ##[4] Temming, K., Zobel, R., Frequency and Risk of Cervical Spine Distortion Injuries in Passenger car Accidents: Significance of Human Factors Data. Proceeding of the International IRCOBI Conference on the Biomechanics of Impact, IRCOBI Secretariat, Bron, France, 1998, pp. 219233 ##[5] Siegmund, G.P., Heinrichs, B.E., Chimich, D.D, Demarco, A.L., Brault, J., The Effect of Collision Pulse Properties on Seven Proposed Whiplash Injury Criteria. Accident analysis & Prevention 2003, Vol. 37 pp. 275285 ##[6] Kraft, M., When do AIS 1 Neck Injuries Result in Long Term Consequences? Vehicle and Human Factors, Traffic Injuries Prevention 2002, Vol. 3, pp. 8997 ##[7] Martinez, J. L. and Garcia, D. J., A Model for Whiplash. Journal of biomechanics 1968, Vol. 1 pp. 2332 ##[8] McKenzie, J. A., and Williams, J. F., The Dynamic Behavior of Head and Cervical Spine During Whiplash. Journal of biomechanics 1971, Vol. 4 pp. 477490 ##[9] Severy, D. M., Mathewson, J. H., and Bechtol, C. O. "Controlled Automobile RearEnd Collisions, an Investigation of Related Engineering and Medical Phenomena", Medical Aspect of Traffic Accidents, Proceedings Montreal Conference, pp. 152184 (1955) ##[10] Linder, A., A New Mathematical Model for a LowVelocity RearEnd Impact Dummy: Evaluation of Components Influencing Head Kinematics. Accident Analysis and Prevention 2000, Vol. 32, pp. 261269. ##[11] Deng YC, Goldsmith W. Response of a human head/neck/uppertorso replica to dynamic loadingII: Analytical/numerical model. Journal of biomechanics 1987, 20(5): 48797. ##[12] McConnell, W. Howard, P.R., Guzman, H. M., Analysis of Human Test Subjects Kinematic Responses to Low Velocity Rear End Impact. SAE Technical Paper, Paper Number 930899. ##[13] Luan, F., Yang, K.H., Deng, B., Begeman, P.C., Tashman, S., King, A. I., Qualitative Analysis of Neck Kinematics during Low Speed RearEnd Impact. Clinical Biomechanics 2000, Vol.15, pp. 649657. ##[14] Ravani, B., Garcia, T., A Biomechanical Evaluation of Whiplash Using a Multibody Dynamic Model, Journal of ASME 2003 Vol. 125, pp. 254265. ##[15] Mertz, H.J., Patrick, L. M., Strength and Response of the Human Neck. Proceedings of the 15th Stapp Car Crash Conference, SAE Inc., New York, LC 6722372, pp. 207255.##]
Development and Application of an ALE Large Deformation Formulation
Development and Application of an ALE Large Deformation Formulation
2
2
This paper presents a complete derivation and implementation of the Arbitrary Lagrangian Eulerian (ALE) formulation for the simulation of nonlinear static and dynamic problems in solid mechanics. While most of the previous work done on ALE for dynamic applications was mainly based on operator split and explicit calculations, this work derives the quasistatic and dynamic ALE equations in its simple and correct form, using a fully coupled implicit approach. Full expression for the ALE virtual work equations is given. Time integration relations for the dynamic equations are also derived. Examples of quasistatic and dynamic large deformation applications are presented.
1
This paper presents a complete derivation and implementation of the Arbitrary Lagrangian Eulerian (ALE) formulation for the simulation of nonlinear static and dynamic problems in solid mechanics. While most of the previous work done on ALE for dynamic applications was mainly based on operator split and explicit calculations, this work derives the quasistatic and dynamic ALE equations in its simple and correct form, using a fully coupled implicit approach. Full expression for the ALE virtual work equations is given. Time integration relations for the dynamic equations are also derived. Examples of quasistatic and dynamic large deformation applications are presented.
17
24


Y.
Tadi benii
Iran


M. R.
Movahhedy
Iran


G.H.
Farrahi
Iran
FEM
ALE
large deformation
Coupled formulations
implicit dynamic analysis
[[1] M.S. Gadala, "Recent trends in ALE formulation and its applications in solid mechanics," Appl. Mech. Engrg. vol. 193, pp. 42474275, 2004. ##[2] Benson DJ., "An efficient, accurate, simple ALE method for nonlinear finite element programs," Comput. Meth. Appl.Mech. Eng. Vol. 72, pp. 305–350, 1989. ##[3] Haber RB., "A mixed EulerianLagrangian displacement model for largedeformation analysis in solid mechanics," Comput. Meth. Appl. Mech. Eng. Vol. 43, pp. 277–292, 1984. ##[4] Hue´tink J, Vreede PT, van der Lugt J, "Progress in mixed EulerianLagrangian finite element simulation of forming processes", Int. J. Numer. Meth. Eng. Vol. 30, pp. 1441–1457, 1990. ##[5] Kennedy JM, Belytschko TB, "Theory and application of a finite element method for arbitrary LagrangianEulerian fluids and structures, " Nuc. Eng. Des. Vol. 68, pp. 129–146, 1981. ##[6] Schreurs PJG, Veldpaus FE, Brekelmans WAM, "Simulation of forming processes using the arbitrary Eulerian Lagrangian formulation," Comput. Meth. Appl. Mech. Eng. Vol. 58, pp. 19–36, 1986. ##[7] T.J.R. Hughes, W.K. Liu, T.K. Zimmermann, "LagrangianEulerian finite element formulation for incompressible viscous flows," Comput. Methods Appl. Mech. Engrg. Vol. 29, pp. 329349, 1981. ##[8] J. Wang, M.S. Gadala, "formulation and survey of ALE method in nonlinear solid mechanics," Finite Element Anal. Des. Vol. 24, pp. 253269 , 1997. ##[9] Gadala, M.S. and Wang, J., "Apractical procedure for mesh motion in ALE method," Eng. With Computers, Vol. 14, pp. 223234 , 1998. ##[10] M.S. Gadala, M.R. Movahhedy, J. Wang, "On the mesh motion for ALE modeling of metal forming processes," Finite Elements in Analysis and Design, Vol. 38, pp. 435459, 2002. ##[11] R. Haber, M.S. Shepard, J.F. Abel, R.H. Gallagher, D.P. Greenberg, "A general twodimentional, graphical finite element preprocessor utilizing discrete transfinite mapping," Int. J. Numer. Methods Engrg. Vol. 17, pp. 10151044, 1981. ##[12] A. Huerta, F. Casadei, "New ALE applications in nonlinear fasttransient solid dynamics, " Engineering Computations, Vol. 11, pp. 317345, 1994. ##[13] H.N. Bayoumi, M.S. Gadala, "A complete finite element treatment for the fully coupled implicit ALE formulation, " Computational Mechanics, Vol. 33, pp. 435452, 2004..##]
Extension of Higher Order Derivatives of Lyapunov Functions in Stability Analysis of Nonlinear Systems
Extension of Higher Order Derivatives of Lyapunov Functions in Stability Analysis of Nonlinear Systems
2
2
The Lyapunov stability method is the most popular and applicable stability analysis tool of nonlinear dynamic systems. However, there are some bottlenecks in the Lyapunov method, such as need for negative definiteness of the Lyapunov function derivative in the direction of the system’s solutions. In this paper, we develop a new theorem to dispense the need for negative definiteness of Lyapunov function derivative. We introduce new sufficient conditions for asymptotic stability of equilibrium states of nonlinear systems considering some inequalities for the higher order time derivatives of Lyapunov function. If the abovementioned inequalities are found, then the stability analysis of an equilibrium state is reduced to check the characteristic equation for a controllable canonical form LTI cosystem. The poles of cosystem are required to be negative real ones. Some examples are presented to demonstrate the approach.
1
The Lyapunov stability method is the most popular and applicable stability analysis tool of nonlinear dynamic systems. However, there are some bottlenecks in the Lyapunov method, such as need for negative definiteness of the Lyapunov function derivative in the direction of the system’s solutions. In this paper, we develop a new theorem to dispense the need for negative definiteness of Lyapunov function derivative. We introduce new sufficient conditions for asymptotic stability of equilibrium states of nonlinear systems considering some inequalities for the higher order time derivatives of Lyapunov function. If the abovementioned inequalities are found, then the stability analysis of an equilibrium state is reduced to check the characteristic equation for a controllable canonical form LTI cosystem. The poles of cosystem are required to be negative real ones. Some examples are presented to demonstrate the approach.
25
33
Nonlinear dynamic systems
Lyapunov methods
Stability Analysis
[[1] M. Vidyasagar, “Nonlinear Systems Analysis”, Prentice Hall, 2’nd Ed, 1993. ##[2] H. K. Khalil, “Nonlinear systems”, Prentice Hall, Englewood Cliffs, NJ, Third ed., 2002. ##[3] K.S Narendra, and A.M. Annaswamy, “Persistent excitation in adaptive systems”, Internat. J. Control, vol. 45, pp. 127160, 1987. ##[4] D. Aeyels and J. Peuteman, “A new asymptotic stability criterion for nonlinear timevariant differential equations”, IEEE Trans. Automat. Control, vol. 43, pp. 968971, 1998. ##[5] R. Bellman, “Vector Lyapunov functions,” SIAM J. Control, vol. 1, pp. 32–34, 1962. ##[6] V. M. Matrosov, “Method of vector Liapunov functions of interconnected systems with distributed parameters (survey)” (in Russian), Avtomatika i Telemekhanika, vol. 33, pp. 63–75, 1972. ##[7] A.A. Martynyuk, “Stability analysis by comparison technique”, Nonlinear Analysis 62 (2005) 629641. ##[8] S. G. Nersesov, W.M. Haddad, “On the stability and control of nonlinear dynamical systems via vector Lyapunov functions”, IEEE Transaction on Automatic Control, vol. 51, no. 2, 2006. ##[9] M. B. Kudaev, “A study of the behavior of the trajectories of systems of differential equations by means of Lyapunov functions”, Dokl. Akad. Nauk. SSSR 147, pp. 12851287, 1962. ##J. A. Yorke, “A theorem on Liapunov functions using ϋ”, Theory of Computing Systems, Springer, vol. 4, no 1, p##]
DelayDependent Robust Asymptotically Stable for Linear Time Variant Systems
DelayDependent Robust Asymptotically Stable for Linear Time Variant Systems
2
2
In this paper, the problem of delay dependent robust asymptotically stable for uncertain linear timevariant system with multiple delays is investigated. A new delaydependent stability sufficient condition is given by using the Lyapunov method, linear matrix inequality (LMI), parameterized firstorder model transformation technique and transformation of the interval uncertainty in to the norm bounded uncertainty. A numerical example is presented to illustrate our present stability criterion allows an upper bound which is bigger on the size of the delay in comparison with those in the literature.
1
In this paper, the problem of delay dependent robust asymptotically stable for uncertain linear timevariant system with multiple delays is investigated. A new delaydependent stability sufficient condition is given by using the Lyapunov method, linear matrix inequality (LMI), parameterized firstorder model transformation technique and transformation of the interval uncertainty in to the norm bounded uncertainty. A numerical example is presented to illustrate our present stability criterion allows an upper bound which is bigger on the size of the delay in comparison with those in the literature.
35
40


D.
Behmardii
Iran


Y.
Ordokhaniii
Iran


S.
Sedaghatiii
Iran
LyapunovKrasovskii Functional
Linear matrix inequality
Parameterized firstorder model transformation
Timedelay systems
[ Campbell,S. A. and Belair, J., 1992, “Multipledelayed differential equations as model for biological control systems.” In Proceeding World Congress of Nonlinear Analysts’ 92, 31103117 ,Tampa. ##[2] Kim, J.H., 2001, “Delay and TimeDerivative Dependent Robust Stability of TimeDelay Linear Systems with Uncertainty.” IEEE Trans. Autom. contr., 46,(5), 789792. ##[3] Kuang, Y., 1993, Delay Differential Equations with Applications in Population Dynamics. Academic Press, Boston. 9 ##[4] Li, C. D. and Liao, X. f., 2006, “A global exponential robust stability criterion for NN with variable delays.” Neurocomputating 69, 8089. ##[5] Li, X. and de Souza, C. E., 1995 “LMI approach to delay dependent robust stability of uncertain linear systems.” in Proc. of the 34th CDC, New Orleans, 36143619. ##[6] Li, X. and de Souza, C. E., 1997, “Delay dependent robust ## stability and stabilization of uncertain linear delay system: A linear Matrix Inequality Approach.” IEEE Trans. on Automatic ## Control, 42, 11441148. ##[7] Macdoonald, N., 1989, Biological Delay Systems: Linear Stability Theory, CambridgeUniversity Press, Cambridge. ##[8] Niculescu, S.I., Doin, J.M., Dugard, L., and Li, H., 1997, “Stability of linear systems with several delays: An L.M.I. approach.” JESA, special issue on ‘Analysis and control of timedelay systems’ 31, 955970. ##[9] Niculescu, S.I., 2001, Delay effects on stability: A robust ## approach. Springer, Berlin. ##[10] Stepan, G., 1998, “Retarded dynamical system stability and characteristic function.” Research Notes in Mathematics Series, John Wiley, New York, P:210. ##[11] Su, J .H., 1994, “Further results on the robust stability of linear systems with a single delay.” Systems and Control Letters, 23, 375379. ##[12] Zhang, Z., Liao, and Ch. Li, X., 2006, “Delaydependent robust stability analysis for interval linear timevariant system with delays and application to delayed neural networks.” Neurocomputating, doi:10.1016/j.neucom.2006.09.010, .##]
Biomechanical Investigation of Empirical Optimal Trajectories Introduced for Snatch Weightlifting
Biomechanical Investigation of Empirical Optimal Trajectories Introduced for Snatch Weightlifting
2
2
The optimal barbell trajectory for snatch weightlifting has been achieved empirically by several researchers. They have studied the differences between the elite weightlifters’ movement patterns and suggested three optimal barbell trajectories (type A, B, and C). But they didn’t agree for introducing the best trajectory. One of the reasons is this idea that the selected criterion by researchers might not be appropriate. Therefore we build a biomechanical model based on inverse dynamic approach to evaluate each trajectory while considering a specific mechanical criterion. We calculate the optimal motion of each trajectory that minimizes the actuating torques by using dynamic programming approach. We solve an example problem for a specific weightlifter that lifts a 100 (kg) barbell. According to our criterion, we recommend the pattern type C as the best trajectory. The most important result of this simulation is the cost assigned to each trajectory which gives us the ability to evaluate the trajectories clearly. This method is an appropriate tool for coaches to examine each trajectory for any specific weightlifter and make a good decision for selecting the best trajectory.
1
The optimal barbell trajectory for snatch weightlifting has been achieved empirically by several researchers. They have studied the differences between the elite weightlifters’ movement patterns and suggested three optimal barbell trajectories (type A, B, and C). But they didn’t agree for introducing the best trajectory. One of the reasons is this idea that the selected criterion by researchers might not be appropriate. Therefore we build a biomechanical model based on inverse dynamic approach to evaluate each trajectory while considering a specific mechanical criterion. We calculate the optimal motion of each trajectory that minimizes the actuating torques by using dynamic programming approach. We solve an example problem for a specific weightlifter that lifts a 100 (kg) barbell. According to our criterion, we recommend the pattern type C as the best trajectory. The most important result of this simulation is the cost assigned to each trajectory which gives us the ability to evaluate the trajectories clearly. This method is an appropriate tool for coaches to examine each trajectory for any specific weightlifter and make a good decision for selecting the best trajectory.
41
47


Shahram
Lenjan Nejadian
Iran


Mostafa
Rostami
Iran


Ahmad Reza
Arshi
Iran


Abolghasem
Naghash
Iran
naghash@aut.ac.ir
Sport Biomechanics
Simulation
Dynamic programming
optimization
[[1] W. Baumann, V. Gross, K. Quade, P. Galbirez, and A. Schwirtz, “The snatch technique of world class weightlifters at the 1985 world championship,” International Journal of Sport Biomechanics, vol. 4, pp. 6889, 1988. ##[2] R. Byrd, “Barbell trajectories: three case study,” Strength and Health, vol. 3, pp. 4042, 2001. ##[3] J. Garhammer, “Biomechanical profiles of Olympic weightlifters,” International Journal of Sport Biomechanics, vol. 1, pp. 122130, 1985. ##[4] J. Garhammer, “Weightlifting performance and techniques of men and women,” in Proc. 1998 First International Conference on Weightlifting and Strength Training, pp. 8994. ##[5] J. Garhammer, “Barbell trajectory, velocity, and power changes: six attempts and four world records,” Weightlifting USA, vol. 19 (3), pp. 2730, 2001. ##[6] V. Gourgoulis, N. Aggelousis, G. Mavromatis, and A. Garas, “Threedimensional kinematic analysis of the snatch of elite Greek weightlifters,” Journal of Sports Sciences, vol. 18 (8), pp. 643652, 2000. ##[7] G. Hiskia, “Biomechanical analysis of world and Olympic champion weightlifters performance,” in Proc. 1997 IWF Weightlifting Symposium, pp. 137158. ##[8] T. Isaka, J. Okada, and K. Funato, “Kinematics analysis of the barbell during the snatch movement of elite Asian weightlifters,” Journal of Applied Biomechanics, vol. 12, pp. 508516, 1996. ##[9] B. Schilling, M. Stone, H. S. O'Brayant, A. C. Fry, R. H. Cogllanese, and K. C. Pierce, “Snatch technique of college national level weightlifters,” Journal of Strength and Conditioning Research, vol. 16 (2), pp. 551555, 2002. ##[10] A. N. Vorobyev, A Textbook on Weightlifting, Budapest: International Weightlifting Federation, 1978. ##[11] C. Chang, D. R. Brown, D. S. Bloswick, and S. M. Hsiang, “Biomechanical simulation of manual lifting using spacetime optimization,” Journal of Biomechanics, vol. 34, pp. 527532, 2001. ##[12] C. J. Lin, M. M. Ayoub, and T. M. Bernard, “Computer motion simulation for sagittal plane activities,” International Journal of Industrial Ergonomics, vol. 24, pp. 141155, 1999. ##[13] W. Park, B. J. Martin, S. Choe, D. B. Chaffin, and M. P. Reed, “Representing and identifying alternative movement technique for goaldirected manual tasks,” Journal of Biomechanics, vol. 38, pp. 519527, 2005. ##[14] S. L. Nejadian, M. Rostami, and F. Towhidkhah, “Optimization of barbell trajectory during the snatch lift technique by using optimal control theory,” American Journal of Applied Sciences, vol. 5 (5), pp. 524531, 2008. ##[15] M. Rostami, and G. Bessonnet, “Sagittal gait of a biped robot during the single support phase, Part 2: Optimal motion,” Robotica, vol. 19, pp. 241253, 2001. ##[16] S. L. Nejadian, and M. Rostami, “Optimization of barbell trajectory during the snatch lift technique by using genetic algorithm,” in Proc. 2007 Fifth IASTED International Conference in Biomechanics, pp. 3439. ##[17] D. B. Chaffin, and G. B. Anderson, Occupational Biomechanics, Wiley, 1991. ##[18] L. L. Menegaldo, A. D. Fleury, and H. I. Weber, “Biomechanical modeling and optimal control of human posture,” Journal of Biomechanics, vol. 36, pp. 17011712, 2003. ##[19] B. P. Derwin, “The snatch: Technical description & periodization program,” National Strength & Conditioning Journal, vol. 12, pp. 8081, 1990.##]
Identification Effect of Nanoclay on Engineering Properties of Asphalt Mixtures
Identification Effect of Nanoclay on Engineering Properties of Asphalt Mixtures
2
2
Nanoclays are new generation of processed clays of interest in a wide range of high performance composites. In other words, nanoclay is defined as a clay that can be modified to make the clay complexes compatible with organic monomers and polymers. Here, it can be said that the polymeric nanocomposites are among the most exciting and promising classes of materials discovered recently. A number of physical properties are enhanced successfully when a polymer is modified with small amount of nanoclay on condition that the clay is dispersed at nanoscopic level. This research has accomplished a comparative rheological test on binders as well as a mechanical test on asphalt mixtures containing unmodified and nanoclay modified bitumen. For that matter, two types of nanoclay were used: Nanofil15 and Cloisite15A. While, the rheological test on binder were penetration, softening point, ductility and aging effect, mechanical test on asphalt mixture were marshal stability, indirect tensile strength, resilient modulus, diametric fatigue and dynamic creep test. Test results show that, nanoclay can improve properties like stability, resilient modulus and indirect tensile strength and possess better behavior compared with unmodified bitumen under dynamic creep although it does not seem to have beneficial effect on fatigue behavior in low temperature. Optimum binder content and void in total mixture (VTM) increase by adding nanoclay to bitumen
1
Nanoclays are new generation of processed clays of interest in a wide range of high performance composites. In other words, nanoclay is defined as a clay that can be modified to make the clay complexes compatible with organic monomers and polymers. Here, it can be said that the polymeric nanocomposites are among the most exciting and promising classes of materials discovered recently. A number of physical properties are enhanced successfully when a polymer is modified with small amount of nanoclay on condition that the clay is dispersed at nanoscopic level. This research has accomplished a comparative rheological test on binders as well as a mechanical test on asphalt mixtures containing unmodified and nanoclay modified bitumen. For that matter, two types of nanoclay were used: Nanofil15 and Cloisite15A. While, the rheological test on binder were penetration, softening point, ductility and aging effect, mechanical test on asphalt mixture were marshal stability, indirect tensile strength, resilient modulus, diametric fatigue and dynamic creep test. Test results show that, nanoclay can improve properties like stability, resilient modulus and indirect tensile strength and possess better behavior compared with unmodified bitumen under dynamic creep although it does not seem to have beneficial effect on fatigue behavior in low temperature. Optimum binder content and void in total mixture (VTM) increase by adding nanoclay to bitumen
49
57


Saeed
Ghaffarpour Jahromi
Iran


Ali
Khodaii
Iran
Asphalt Mixture
Bitumen Modifies
Nanoclay
Mechanical Properties
[[1] Pinnavaia T.J. and G.W.Beall, (2000) "Polymer–Clay Nanocomposites", John Wiley and Sons Ltd, England. ##[2] Grim, R. E. (1959). "PhysicaoChemical Properties of Soils: Clay Minerals", Journal of the Soil Mechanics and Foundations Division, ASCE, Vol. 85, No. SM2, 117. ##[3] Lan T, Kaviratna PD, Pinnavaia TJ. (1995), "Mechanism of clay tactoid exfoliation in epoxy–clay nanocomposites", Chem Mater ;7, 2144–50. ##[4] Theng B. (2006), "Formation and properties of claypolymer complexes", Elsevier; 1979. ##[5] "Southern Clay Products" (2006), Inc. <Website, http://www.nanoclay.com/faqs.asp>. ## Nguyen QT, Baird DG. (2007), "Process for increasing the exfoliation and dispersion of nanoclay particles into polymer ##]
Torsion Analysis of HighRise Buildings using Quadrilateral Panel Elements with Drilling D.O.F.s
Torsion Analysis of HighRise Buildings using Quadrilateral Panel Elements with Drilling D.O.F.s
2
2
Generally, the finite element method is a powerful procedure for analysis of tall buildings. Yet, it should be noted that there are some problems in the application of many finite elements to the analysis of tall building structures. The presence of artificial flexure and parasitic shear effects in many lower order plane stress and membrane elements, cause the numerical procedure to converge in a low rate. Nevertheless, very large hardware memory storage is needed because of using fine meshes. Hence, it should be better to develop and use elements which can model the structural system of tall buildings in coarse finite element meshes and converge fast. The panel type finite elements presented in this study, have vertical and horizontal degrees of freedom similar to those of wide column analogy in the frame method. There are two rotational degrees of freedom to be defined at the two end of the panel element, which denote the rotational freedom equal to the first derivative of lateral displacement. The proposed elements can simply be used in tall building analysis. The application of the proposed elements can be performed without using a fine mesh. Examples are given to denote the accuracy and efficiency of the presented panel elements.
1
Generally, the finite element method is a powerful procedure for analysis of tall buildings. Yet, it should be noted that there are some problems in the application of many finite elements to the analysis of tall building structures. The presence of artificial flexure and parasitic shear effects in many lower order plane stress and membrane elements, cause the numerical procedure to converge in a low rate. Nevertheless, very large hardware memory storage is needed because of using fine meshes. Hence, it should be better to develop and use elements which can model the structural system of tall buildings in coarse finite element meshes and converge fast. The panel type finite elements presented in this study, have vertical and horizontal degrees of freedom similar to those of wide column analogy in the frame method. There are two rotational degrees of freedom to be defined at the two end of the panel element, which denote the rotational freedom equal to the first derivative of lateral displacement. The proposed elements can simply be used in tall building analysis. The application of the proposed elements can be performed without using a fine mesh. Examples are given to denote the accuracy and efficiency of the presented panel elements.
59
67


Afshin
MeshkatDinii
Iran


Mohsen
Tehranizadehii
Iran
Tall Building
Quadrilateral Element
In Plane Rotation Degree of Freedom
Strain Based Panel Element
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