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CONTENTS
Volume 49, Number 6, March 25 2014
 

Abstract
The topic of this study is to strengthen cracked beams with prefabricated RC U cross-sectional plates. The damaged beams were repaired by epoxy based glue. The repaired beams were strengthened using prefabricated plates. The strengthening plates were bonded to the bottom and side faces of the beams by anchorage rods and epoxy. The strengthened beams were incrementally loaded up to maximum load capacities. The experimental results were satisfactory since the load carrying capacities of damaged beams were increased approximately 76% due to strengthening. It was observed that strengthening plates had a dominant effect on the performance of beams in terms of both the post-elastic strength enhancement and the ductility. The experimental program was supported by a three-dimensional nonlinear finite element analysis. The experimental results were compared with the results obtained from the beam modeled with ANSYS finite element program.

Key Words
prefabricated RC plate; strengthening; load carrying capacity; ductility; epoxy; anchorage rod; ANSYS

Address
Ali Demir, Muhammed Tekin, Tezcan Turali and Muhiddin Bagci : Department of Civil Engineering, Celal Bayar University, Manisa, Turkey

Abstract
This paper develops a new nonlinear model for active control of three-dimensional (3D) irregular building structures. Both geometrical and material nonlinearities with a neuro-controller training algorithm are applied to a multi-degree-of-freedom 3D system. Two dynamic assembling motions are considered simultaneously in the control model such as coupling between torsional and lateral responses of the structure and interaction between the structural system and the actuators. The proposed control system and training algorithm of the structural system are evaluated by simulating the responses of the structure under the El- Centro 1940 earthquake excitation. In the numerical example, the 3D three-story structure with linear and nonlinear stiffness is controlled by a trained neural network. The actuator dynamics, control time delay and incident angle of earthquake are also considered in the simulation. Results show that the proposed control algorithm for 3D buildings is effective in structural control.

Key Words
neural network; nonlinear control; active control; regular and irregular building

Address
Yasser Bigdeli, Dookie Kim : Department of Civil Engineering, Kunsan National University, Jeonbuk, Korea
Seongkyu Chang : TE Solution Co., Ltd, Gongdo-Eup, Anseong-Si, Gyunggi-Do, Korea

Abstract
In general, cylindrically curved plates are used in ships and offshore structures such as wind towers, spa structures, fore and aft side shell plating, and bilge circle parts in merchant vessels. In a number of studies, it has been shown that curvature increases the buckling strength of a plate under compressive loading, and the ultimate load-carrying capacity is also expected to increase. In the present paper, a series of elastic and elastoplastic large deflection analyses were performed using the commercial finite element analysis program (MSC.NASTRAN/PATRAN) in order to clarify and examine the fundamental buckling and collapse behaviors of curved plates subjected to combined axial compression and lateral pressure. On the basis of the numerical results, the effects of curvature, the magnitude of the initial deflection, the slenderness ratio, and the aspect ratio on the characteristics of the buckling and collapse behavior of the curved plates are discussed. On the basis of the calculated results, the design formula was developed to predict the buckling and ultimate strengths of curved plates subjected to combined loads in an analytical manner. The buckling strength behaviors were simulated by performing elastic large deflection analyses. The newly developed formulations were applied in order to perform verification analyses for the curved plates by comparing the numerical results, and then, the usefulness of the proposed method was demonstrated.

Key Words
curved plate; nonlinear buckling; critical buckling; design formula; flank angle (curvature); MSC.NASTRAN/PATRAN

Address
Joo-Hyun Kim, Jeong-Hyeon Kim, Myung-Hyun Kim and Jae-Myung Lee : Department of Naval Architecture & Ocean Engineering, Pusan National University, Busan 609-735, South Korea
Joo-Shin Park : Samsung Heavy Industries Co., Ltd., Geoje 656-710, South Korea
Kyung-Hun Lee : Sungdong Shipbuilding & Marine Engineering Co., Ltd., Tongyeong 650-827, South Korea

Abstract
Geometrically nonlinear analysis of planar beam and frame structures made of functionally graded material (FGM) by using the finite element method is presented. The material property of the structures is assumed to be graded in the thickness direction by a power law distribution. A nonlinear beam element based on Bernoulli beam theory, taking the shift of the neutral axis position into account, is formulated in the context of the co-rotational formulation. The nonlinear equilibrium equations are solved by using the incremental/iterative procedure in a combination with the arc-length control method. Numerical examples show that the formulated element is capable to give accurate results by using just several elements. the influence of the material inhomogeneity in the geometrically nonlinear behavior of the FGM beam and frame structures is examined and highlighted.

Key Words
functionally graded material; beam element; geometrical nonlinearity; finite element method

Address
Dinh-Kien Nguyen, Thanh-Huong Trinh : Department of Solid Mechanics, Institute of Mechanics, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Hanoi, Vietnam
Buntara S. Gan : Department of Architecture, College of Engineering, Nihon University, Koriyama, Fukushima-ken, 963-8642 Japan

Abstract
As an important part, the connections generally are important for the overall behavior of the structure and the strength and serviceability of the connection should be ensured. This paper presents the mechanical properties of membrane connections in tensioned membrane structure. First, the details of common connections used in the membrane structure are introduced. Then, the common connections including membrane seam, membrane-flexible edge connection and membrane-rigid edge connection are tested and the corresponding failure mechanisms are discussed. Finally, the effects of connection parameters on the connection strength are investigated and proper connection parameters are proposed. The strength reduction factors corresponding to different connection types are proposed, which can be references for the design and analysis of membrane structures.

Key Words
membrane connection; connection strength; orthogonal test; strength reduction factor

Address
Yingying Zhang : Jiangsu Key Laboratory of Environmental Impact and Structural Safety in Engineering,
China University of Mining and Technology, Jiangsu Xuzhou, China
Qilin Zhang : College of Civil Engineering, Tongji University, Shanghai, China
Yang Li : Shanghai Urban Construction and Communications Commission, Shanghai, China
Lu Chen : Shanghai Tongji Construction Quality Inspection Station, Shanghai, China


Abstract
The recently developed Ultra High Performance Concrete (UHPC) displays outstanding compressive strength and ductility but is also subjected to very large autogenous shrinkage. In addition, the use of forms and reinforcement to confine this autogenous shrinkage increases the risk of shrinkage cracking. Accordingly, this study adopts a combination of shrinkage reducing admixture and expansive admixture as a solution to reduce the shrinkage of UHPC and estimates its appropriateness by evaluating the compressive and flexural strengths as well as the autogenous shrinkage according to the age. Moreover, the coefficient of thermal expansion known to experience sudden variations at early age is measured in order to evaluate exactly the autogenous shrinkage and the thermal expansion is compensated considering these measurements. The experimental results show that the compressive and flexural strengths decreased slightly at early age when mixing 7.5% of expansive admixture and 1% of shrinkage reducing admixture but that this decrease becomes insignificant after 7 days. The use of expansive admixture tended to premature the setting of UHPC and the start of sudden increase of autogenous shrinkage. Finally, the combined use of shrinkage reducing admixture and expansive admixture appeared to reduce effectively the autogenous shrinkage by about 47% at 15 days.

Key Words
ultra high performance concrete; coefficient of thermal expansion; autogenous shrinkage; setting properties; shrinkage reducing admixture; expansive admixture

Address
Jung-Jun Park, Sung-Wook Kim : Structural Engineering Research Division, Korea Institute of Construction Technology, Korea
Doo-Yeol Yoo, Young-Soo Yoon : School of Civil, Environmental and Architectural Engineering, Korea University, Korea

Abstract
Static loading tests were carried out in this study to investigate the effect of bar cutoff on the resistance of RC beam-column sub-assemblages under column loss. Two specimens were designed with continuous main reinforcement. Four others were designed with different types of bar cutoff in the mid-span and/or the beam-end regions. Compressive arch and tensile catenary responses of the specimens under gravitational loading were compared. Test results indicated that those specimens with approximately equal moment strength at the beam ends had similar peak loading resistance in the compressive arch phase but varied resistance degradation in the transition phase because of bar cutoff. The compressive bars terminated at one-third span could help to mitigate the degradation although they had minor contribution to the catenary action. Among those cutoff patterns, the K-type cutoff presented the best strength enhancement. It revealed that it is better to extend the steel bars beyond the mid-span before cutoff for the two-span beams bridging over a column vulnerable to sudden failure. For general cutoff patterns dominated by gravitational and seismic designs, they may be appropriately modified to minimize the influence of bar cutoff on the progressive collapse resistance.

Key Words
static loading test; column loss; bar cutoff; RC sub-assemblage; arch action; catenary action

Address
Meng-Hao Tsai, Jun-Kai Lu and Bo-Hong Huang : Department of Civil Engineering, National Pingtung University of Science and Technology, No.1 Hseuh-Fu Rd., Neipu, Pingtung County, 912, Taiwan

Abstract
This research work deals with the development of a new Triangular finite element for the linear analysis of plate bending with transverse shear effect. It is developed in perspective to building shell elements. The displacements field of the element has been developed by the use of the strain-based approach and it is based on the assumed independent functions for the various components of strain insofar as it is allowed by the compatibility equations. Its formulation uses also concepts related to the fourth fictitious node, the static condensation and analytic integration. It is based on the assumptions of tick plate‟s theory (Reissner-Mindlin theory). The element possesses three essential external degrees of freedom at each of the four nodes and satisfies the exact representation of the rigid body modes of displacements. As a result of this approach, a new bending plate finite element (Pep43) which is competitive, robust and efficient.

Key Words
finite elements; strain approach; static condensation; plate theory; Reissner-Mindlin

Address
Mohammed Himeur : Department of Civil Engineering, Mentouri University, Constantine 25000, Algeria
Abdelaziz Benmarce : Department of Civil Engineering and Hydraulic, May 8, 1945 University, Guelma, 24000, Algeria
Mohamed Guenfoud : Civil Engineering and Hydraulic Laboratory, Guelma University, 24000, Algeria


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