1、PDF外文：http:/ 外文翻译原文 Improvement of Concrete Shear Wall Structures by Smart Materials Mehdi Ghassemieh1*, Mohammad Reza Bahaari1, Seyed Mohyeddin Ghodratian1, Seyed Ali Nojoumi2 1School of Civil Engineering, University of Tehran, Tehran, Iran 2Civil & Environmental E
2、ngineering Department, University of California, Los Angeles, USA Email: *mghassemut.ac.ir Received May 7, 2012； revised June 10, 2012； accepted June 20, 2012 ABSTRACT Smart materials have found numerous applications in many areas in civil engineering recently. One class of t
3、hese mate-rials is shape memory alloy (SMA) which exhibits several unique characteristics such as superelasticity and shape memory effect. Due to these characteristics, research efforts have been extended to use SMA in controlling civil struc-tures. This paper investigates the effectiveness of SMA r
4、einforcements in enhancing the behavior of shear walls, espe-cially when subjected to seismic excitations. Two ordinary and coupled shear walls were introduced as reference struc-tures and were modeled by ABAQUS software. For improving the seismic response of the shear walls, vertical SMA reinforcin
5、g bars were proposed to be implemented like conventional steel reinforcements, throughout the height of the structures and in every connecting beam in the coupled shear wall system. The one dimensional superelastic model of SMA material was implemented in the computer software using FORTRAN code. Th
6、e dynamic response of the shear walls subjected to seismic loading was investigated through time history analyses under El-centro and Koyna records. The results showed that using superelastic SMA material instead of steel bars caused remarkable reduction in residual displacement for both ordinary an
7、d coupled shear walls. In addition, SMA reinforcements could significantly decrease the maximum deflection of the coupled shear wall system. Keywords: Smart Material； Shape Memory Alloy； Shear Wall； Superelasticity； Seismic Behavior Introduction Many multi-storey buildings contain
8、 shear walls around the elevator shafts and stairwells as lateral resisting sys-tems. For the concrete shear wall systems, it is difficult to satisfy the very ductile behavior conditions. Therefore, such structures have often suffered damages caused by earthquake events. Shearing damage, bending dam
9、age, sliding and overturning damage are usually four kind of damage occur in concrete shear wall during earthquake. If concrete shear wall can attain their initial shape after an earthquake, then problems associated with permanent damage can be addressed. Sometimes, there are several openings in the
10、se shear walls and if two such openings are on opposite sides, deep coupling beams are supposed to interconnect the walls. These coupling beams are gen-erally used as a means of dissipating energy during earthquakes through experiencing inelastic yielding. Due to their small span to depth ratio, the
11、y require highly congested reinforcement in order to achieve ductile be-havior. Although dissipating energy through plastic hinging is a common practice in the design of multi-storey buildings, this practice usually results in significant residual displacements and the need to repair the struc-tural
12、 elements after the earthquake. To address the shortcomings of current practices, a new design approach using smart materials such as shape memory alloy (SMA) is proposed. SMA is one example of smart materials that exhibit several unique characteristics such as shape memory ef-fect, superelast
13、icity, and energy dissipation features. Due to these characteristics, Shape Memory Alloys have widely attracted attentions in passive control of structures in recent years. Dolce, et al. in a series of publications studied the effectiveness of SMA materials for use in seismic applications 1. They al
14、so studied the imple-mentation of various states of SMA materials for the use of special dampers in structures. They proposed different recentering or dissipating devices based on experimental results. Wilde et al. performed an analytical study of SMA-based seismic isolation system consist of lamina
15、ted rubber bearing and superelastic SMA bars 2. They conducted time history analysis with different excitation to compare the SMA-based bearing with conventional bearing with lead core. Dolce and Cardone experimenttally investigated the proper choice of alloy, the effect of temperature, SMA size and
16、 loading rate and number of cycles 3. Bruno and Valente showed the effectiveness of the use of SMA materials by analytical measures using simple pseudoelastic constitutive model for SMAs using damage index approach 4. Baratta and Corbi analyzed the dynamics of a structural elastic-plastic frame, en-
17、dowed with pseudoelastic SMA tendons 5. DesRoches and Delemont evaluated the efficiency of using SMA restrainers to reduce the response of decks in a multi span simply supported bridge 6. Masuda and Noori investigated the optimization of hysteretic characteristics of damping devices based on pseudoe
18、lastic SMAs 7. DesRoches et al. experimentally evaluated the properties of superelastic Ni-Ti shape memory alloys under cyclic loading to assess their potential for applications in seis-mic resistant design and retrofit 8. Abolmaali et al. compared the energy dissipative characteristics of bolted t-
19、stub connections using steel and shape memory alloy (SMA) fasteners 9. Choi et al. proposed a new SMA- rubber bearing which is composed of a conventional elastomeric bearing and SMA wires wrapping the bear-ing in longitudinal direction 10. A multilinear constitu-tive model developed by Motahari and
20、Ghassemieh was adopted to capture the most common behaviors of SMA 11. Czaderski et al. tested a reinforced concrete (RC) beam equipped with SMA material and compared it with conventional RC beam 12. The results proved that by using shape memory alloys it is possible to produce a RC beam which has v
21、ariable stiffness and strength. Saiidi and Wang presented the application of SMA bars instead of steel bars in plastic hinge zone of reinforced concrete bridge piers 13. Motahari et al. also introduced a spe-cial SMA damper to have both re-centering and energy dissipating characteristics simultaneou
22、sly 14. Li et al. experimentally studied the behavior of smart concrete beams with embedded shape memory alloy bundles 15. They used SMA bundles as actuators to achieve recovery force. Andrawes and DesRoches compared the efficiency of SMA restrainers with three other retrofit devices including conve
23、ntional steel restrainers, metallic dampers and viscoelastic dampers 16. Johnson et al. conducted a large scale testing program to evaluate the effect of SMA restrainer cable on the seismic performance of in-span hinges of multiple-frame concrete box girder bridge sub-jected to strong ground motion
24、17. Rahman et al. in-vestigated the effect of cross section geometry on the bending of a beam and also buckling of a column made of SMA through a numerical study 18. Sharabash and Andrawes studied the application of SMAs as seismic passive damper devices for vibration mitigation of cable stayed brid
25、ges 19. The feasibility of superelasticity in increasing ductility capacity and decreasing residual dis-placement of concrete bridge column was investigated by Saiidi et al. 20. Ozbulut and Hurlebaus explored the effectiveness of SMA-rubber based isolation systems for seismic protection of bridges a
26、gainst near-field earth-quakes. They also compare the performance of SMA- rubber based isolation systems with SMA-based sliding isolation system 21. Kari et al. evaluated the effective-ness of a new dual bracing system for improving the seismic behavior of steel structures 22. In this study th
27、e behavior of concrete shear walls rein-forced with SMA bars is investigated. Finite element program, ABAQUS, was used in order to assess the re-sponse of the structures subjected to seismic loading. Two ordinary and coupled shear walls were introduced as reference structures and their seismic behav
28、ior with and without SMA reinforcement was evaluated through time history analyses. 2. Shape Memory Alloy Shape Memory Alloys are new class of metallic alloys that display multiple incomparable characteristics, based on martensitic phase transformation. SMAs are able to undergo large strains (8% - 10%) without leaving per-manent deformations in the material. They can recover their initial shape at the end of the deformation process, instinctively (called superelasticity) or by heating (called shape memory effect) as shown in Figure 1.
