1、附录 1 英文文章翻译（原文） State of the art of buckling-restrained braces in Asia Qiang Xie Department of Structural Engineering, Tongji University, Shanghai 200092, China Received 3 September 2004； accepted 19 November 2004 Abstract： This paper presents a summary of buckling-restrained braces (BRBs). BRBs sho
2、w the same loaddeformationbehavior in both compression and tension and higher energy absorption capacity witheasy adjustability of both stiffness and strength. Research and developments of various types of BRBswith different configurations in Asia, especially in Japan, are introduced. Analyses and e
3、xperimentsare illustrated to show the conditions necessary for restraining steel braces from buckling. Somekey issues of BRB configurations, such as gap and debonding processing between core braces andencasing members, contraction allowance in BRBs and necessary clearances between restrainingpanels
4、and surrounding frames, BRB projection stiffening approaches to prevent it from buckling, arealso described. Based on initial deflections of core braces, both stiffness and strength requirementsof encasing member to prevent buckling of core brace are given. Applications for both new high-risesteel b
5、uildings and the seismic retrofit of existing buildings show good prospects of using BRBs. 2004 Elsevier Ltd. All rights reserved. Keywords: Steel frame； Buckling； Buckling-restrained braces； Cyclic loading test； Damper； Hysteretic behavior 1. Introduction Lateral displacements on structural buildin
6、gs have been of great concern for engineers.In order to minimize the effect of earthquake and wind forces braces have been usedsuccessfully. However, when the braces are subjected to large compressive forces theyexhibit buckling deformation and show unsymmetrical hysteretic behavior in tensionand co
7、mpression, and typically exhibit substantial strength deterioration when loadedmonotonically in compression or cyclically, as shown in Fig. 1(a). Ifbuckling of a steelbrace is restrained and the same strength is ensured both in tension and compression, the energy absorption of the brace will be mark
8、edly increased and the hysteretic propertywill be simplified. These requirementsmotivate researchers and engineers to develop a newtype of brace, buckling-restrained brace (BRB). The concept of BRB is simple: restraining buckling of the brace so that the brace exhibits the same behavior both in tens
9、ion and compression, as shown in Fig. 1(b). In the last few decades, buckling-restrained braced frames have become increasingly popular especially in Japan for their good earthquake performance. As shown in Fig. 2, a BRB usually consists of the following four parts: 1. Axial force-carrying unit (bra
10、ce)； 2. Stiffened transition segment (projection) which connects the brace and connection part； 3. Buckling-restraining unit (encasing member), whose function is to prevent the brace from buckling； 4. Separation unit between brace and buckling-restraining units, which ensures the brace can slide fre
11、ely inside the buckling-restraining unit and that transverse expansion of the brace can take place when the brace yields in compression. This typically requires some debonding material to be employed as a separation unit. Otherwise, a gap should be kept between the two units. This paper introduces t
12、he research and developments of various types of BRBs with different configurations in Asia, especially in Japan in the past few decades. Theories and experiments for the conditions to prevent steel braces from buckling are illustrated. Some key issues of BRB configurations and requirements of stiff
13、ness and strength of encasing member are also described. Applications for both new high-rise steel buildings and the seismic retrofit of existing buildings show good prospects of using BRBs. 2. Development of BRBs 2.1. History of BRBs Research on BRBs was first carried out by Yoshino et al. 1. They
14、tested cyclically two specimens that they called “Shear wall with braces”, consisting of a flat steel plateencased by reinforced concrete panels with some debonding materials between them.Onehas a clearance of 15 mm between the panel lateral sides and the surrounding panel whilstthe other was not pr
15、ovided with such spacing. The former exhibits higher deformation andenergy dissipation capacity than the latter. Wakabayashi et al. conducted pioneering thorough research on BRBs 2,3. Theydeveloped a system in which braces made of steel flat plates were encased by reinforcedconcrete panels with an u
16、nbonded layer between them.They found that the process ofachieving debonding on the braces surface was very important to make the bracepanelsystem to satisfy the condition that only the brace resists horizontal loading while theconcrete panel serves only to prevent the brace from buckling.A multi-st
17、ep experimentalplan was carried out, which consisted of (1) testing of debonding materials to exploreunbonded effects； (2) brace tests to examine the effects of reinforcement at boundariesand around the plates and strengthening of PC panels with reinforcing bars； (3) tests onreduced-scale brace syst
18、ems encased by PC panels； and (4) large-scale tests on two-storyframes with the proposed brace systems. For the debonding effect test, epoxy resin, silicon resin, vinyl tapes, etc. were tested,and eleven specimens with different debonding materials were examined using pull-outtests. The debonding me
19、thod of coating a silicon resin layer on top of an epoxy resin wasutilized in the following tests. Various reinforcing details around the plate and details between the exposed andembedded parts (styrol foam, gaps) were chosen as the test variables. Twenty-onespecimenswith many combinations of the va
20、riableswere tested formonotonic compressiveloading. The results showed that in order not to restrain the deformation of the stiffenedends in the precast panel, it is necessary to put small styrol foam into the gap. To verify the hysteretic behavior, fourteen 1/5-scale specimens of X-shape anddiagona
21、l-shape braces encased by PC panels were tested under cyclic loading. Test setupand hysteretic behavior of one of the specimens are shown in Fig. 3. The test results showedthat the load carrying capacity of the unbonded braces was larger than that of the bondedbraces. Maximum lateral drift angle was
22、 about 0.03 rad, almost four times that of thebonded brace. Uniform strain distributions measured along the axis of the brace were thesame as those of a bare brace, which indicates the effectiveness of debonding. In order to check the behavior of the BRB in real steel frames, two 1/2-scale tests (tw
23、o spans) were performed for final demonstration. Fig. 4 shows the X-shapebraced frame model and its hysteretic behavior. Before local buckling occurred in the steelplate at a drift angle of about 0.025 rad, behavior of the frame was stable, showing spindleshapehysteretic loops and good energy absorp
24、tion capacity.The first test on steel braces encased in mortar-infilled steel tubes was conducted byKimura et al. 4.Although there was no debonding material or gap between the mortarand core braces, the mortar-infilled tubes showed some effects on restraining buckling ofcore braces. Longitudinal str
25、ains measured on the outer tubes were approximately 1015%of those on the interior steel plates, and the braces typically exhibited higher resistance incompression than in tension. In their subsequent research 5, four full-scale specimens,two of them having some slits between the braces and the surro
26、unding mortar, were testedcyclically. They concluded from the test results that if the ratios between Eulers limit ofouter tube and yielding strength of brace are larger than 1.9, no buckling would occur inthe core braces and these specimens showed good hysteretic behavior. Mochizuki et al. 68 studi
27、ed the composite BRBs consisting of unbonded bracesencased in reinforced concrete square cross-section members. In their study, a coefficientfactor that represents the stiffness degradation of concrete panel after it cracks was used.Fujimoto et al. 9,10 extended the research by Kimura and Takeda, th
28、e steel core braceswere coated with debonding material and restrained by mortar-infilled square steel tubes.Nagao et al. 1115 did some tests and theoretical analyses on composite BRBs composedof square steel tubes (braces) or H-section steel cores covered by reinforced concretemembers. 2.2. BRB conf
29、igurations As shown in Fig. 5, BRBs can be divided primarily into two wide categories coveringdifferent configurations: one typical BRB consists of a steel brace encased by a reinforcedconcrete member or steel member such as tubes, the other type is a steel plate brace encasedby precast concrete pan
30、els. Fig. 6 shows two photos of these two types of BRBs. Cross-sections of typical BRBs are shown in Fig. 7. Fig. 7(a) shows steel plateor crisscross cross-section plate braces stiffened by mortar-infilled steel tubes 9,10,1618. Fig. 7(b) exhibits H-section steel braces enclosed by reinforced concre
31、te 1115.Fig. 7(c) exhibits crisscross cross-section steel brace enclosed by steel-fiber reinforcedconcrete 19. Fig. 7(d) shows a type of steel plate brace stiffened by two bolt-connectedprecast concrete panels 20. The model by Suzuki et al. 21,22 consists of a wide flangesection restrained against lateral buckling by an exterior steel tube as shown in Fig. 7(e).Cross-section of BRB consisting of two circular steel tubes is shown in Fig. 7(f). Inthis configuration, the inner tube is responsible for providing the
