毕业设计(论文)外文资料翻译.doc

淮 阴 工 学 院毕业设计(论文)外文资料翻译学 院：建筑工程学院专 业：土木工程姓 名：XX学 号：XX外文出处：J CENT SOUTH UNIV T(用外文写)附 件：1.外文资料翻译译文；2.外文原文。指导教师评语： 译文语句通顺，词能达意，具有较好的翻译能力，译文质量较高。年月日签名： （手写签名） 注：请将该封面与附件装订成册。附件2：外文原文J. Cent. South Univ. (2015) 22: 27302738DOI: 10.1007/s11771-015-2803-4Progressive collapse resisting capacity of reinforced concrete load bearing wall structuresAlireza Rahai1, Alireza Shahin1, Farzad Hatami21. Department of Civil Engineering, Amirkabir University of Technology (Tehran Polytechnic) No. 424,Hafez Ave., P. O. Box. 15875-4413, Tehran, Iran;2. Structural & Earthquake Research Center (SERC), Amirkabir University of Technology No.424,Hafez Ave., P. O. Box. 15875-4413, Tehran, Iran Central South University Press and Springer-Verlag Berlin Heidelberg 2015Abstract: Reinforced concrete (RC) load bearing wall is widely used in high-rise and mid-rise buildings. Due to the number of walls in plan and reduction in lateral force portion, this system is not only stronger against earthquakes, but also more economical. The effect of progressive collapse caused by removal of load bearing elements, in various positions in plan and stories of the RC load bearing wall system was evaluated by nonlinear dynamic and static analyses. For this purpose, three-dimensional model of 10-story structure was selected. The analysis results indicated stability, strength and stiffness of the RC load-bearing wall system against progressive collapse. It was observed that the most critical condition for removal of load bearing walls was the instantaneous removal of the surrounding walls located at the corners of the building where the sections of the load bearing elements were changed. In this case, the maximum vertical displacement was limited to 6.3 mm and the structure failed after applying the load of 10 times the axial load bored by removed elements. Comparison between the results of the nonlinear dynamic and static analyses demonstrated that the “load factor” parameter was a reasonable criterion to evaluate the progressive collapse potential of the structure.Key words: reinforced concrete (RC) load bearing wall structure; progressive collapse; fiber sections; nonlinear analysis; load factor method1 IntroductionThe reinforced concrete (RC) load bearing wall system is one of the most appropriate structural systems for mid-rise buildings, which results in the reduction of constructional material in addition to improved strength against earthquakes. Indeed, due to the direct connection of slab to wall and its large connection zone, transmission of forces increases and stress concentration at the joints will be greatly reduced. In addition, intersection of the walls increases structure indeterminacy and provides stability and good seismic performance.Progressive collapse may happen due to explosion, fire, earthquake, vehicle collision, errors in design and construction of buildings with any system type. This can be caused by the failure and instability in a small part of the structure which gradually develops as a chain function and eventually leads to the collapse of an important part of the structure. When the main load bearing elements in buildings are destroyed, the attached elements to the damaged one lose their support and theforce which was bored by the damaged element will be redistributed within the structure. If the structure could not reach a new static equilibrium condition, the initial collapse will lead to instability and destruction in a large part, and the system will lose its expected service and performance level. Therefore, by progressive collapse analysis of the structures, critical elements and weaknesses of the systems against accidental loads can be detected and by strengthening them and making alternative load paths, structures stability and residents safety are insured; while standards and regulations for analysis and design of structures against progressive collapse have been provided by professional organizations around the world. GSA 1 and UFC 2 are the most popular.A large number of researchers have studied the progressive collapse phenomena in reinforced concrete structures. They investigated the validity and applicability of the various analysis methods for accurate prediction of progressive collapse in different structural systems. Sudden load bearing element loss is a common method widely used to evaluate the progressive collapse potential of structures 3. LU et al 4 investigated the potentialReceived date: 20140822; Accepted date: 20150124Corresponding author: Farzad Hatami, Assistant Professor; Tel: +982164545536; E-mail: hatamiaut.ac.irJ. Cent. South Univ. (2015) 22: 273027382731the potential of progressive collapse in RC moment frame structures using pushdown analysis. Following the simultaneous removal of two adjacent exterior columns in the first story of the Hotel San Diego, SASANI 5 evaluated the response of the six-story reinforced concrete infilled-frame structure. KIM and JUNG 6 studied the behavior of tilted building structures and proved their vulnerability to progressive collapse compared to common structures. Sometimes, progressive collapse is triggered by consecutive removal of several load bearing elements. So as to enable common macromodeling programs to model such scenarios, PACHENARI and KERAMATI 7 presented a method for modeling successive removal of columns using a series of subsequent analyses. They stated that the method could be a prerequisite of defining more realistic collapse scenarios in relevant guidelines. By double-designing a frame-wall structure with this assumption that it had high or low design of lateral loads and by removing an external wall in the first story, BAO and KUNNATH 8 concluded that further design of lateral loads leads to more progressive collapse resistance and less vertical displacement of the upper joint of the removed wall. PACHENARI and KERAMATI 9 introduced relevant beamslab collapse modes of the impacted story in the case that column loss scenario causes adjoining panels to fall down in a two-way slab reinforced concrete structure. They concluded that the ratio of beam to slab flexural strength and existing dead and live loads on panels in the vicinity of impacted panels could change the collapse pattern and subsequently control the prevailing collapse mode.However, no research has been conducted yet to investigate the progressive collapse potential of three-dimensional RC load bearing wall structures. Thus, in this work the behavior of the RC load bearing wall system against progressive collapse is examined by using nonlinear dynamic and static analyses.2 ValidationTo ensure the accuracy of modeling by the fiber section method, the analysis results of the PERFORM 3D model were validated by a RC load bearing wall specimen (THOMSEN and WALLACE 10). This testwas performed to evaluate the behavior of slender RC walls under simultaneous gravity and lateral loads.2.1 Details of test specimenThe wall specimen investigated was 1/4 scaled with height of 3660 mm. Figure 1 shows the cross section of the wall and reinforcement details. By two hydraulic jacks that were installed on the top of the wall, an axial load of approximately 0.07Agfc was applied uniformly and constantly throughout the experiment. A hydraulic actuator which was mounted horizontally in the corner of the highest level of the wall was used to apply lateral periodic and incremental drift (Fig. 2).Modeling and comparison of analytical and experimental resultsDue to the two-dimensional analysis, translationsand rotations normal to the wall plain were prevented and all the wall joints were constrained to the diaphragm for in-plain displacements. Wall supports were assumed to be restrained. Nonlinear properties of the wall were defined by fiber sections and assigning nonlinear material stress-strain curves to these fibers. Basic calibrated parameters in defining the material stress strain curve are presented in Table 1. Relations proposed by MANDER et al 11 were used in defining the stressstrain curve of concrete. It should be noted that the stressstrain curve of confined concrete was assigned to concrete fibers of the wall boundary and stressstrain curve of unconfined concrete was assigned to concrete fibers of the wall web.Nonlinear static analysis (Pushover) was performed in two steps:Step 1): The axial load was applied to the wall. Step 2): By holding the axial load constant and withinitial conditions of the previous step, the lateral load was applied incrementally and increased step by step until displacement of the highest level reached the target displacement.To obtain the cyclic behavior and hysteresis loops of the wall, nonlinear dynamic analysis was performed following these procedures:The axial load was applied to the wall.By holding the axial load constant and with initial conditions of the previous step, the lateralFig. 1 Reinforcing details of secimen (THOMSEN and WALLACE 10)2732J. Cent. South Univ. (2015) 22: 27302738Fig. 2 Applied displacement history 10displacement record was applied to the wall by a spring element. This element had to be very stiff versus structure stiffness and only transitional stiffness had to be considered.Figure 3 compares the results of the analytical and experimental models. The analytical model captured the measured response reasonably well. The analysis results clearly reflected actual characteristics of cyclic wall response, including stiffness degradation, shape of theload-displacement hysteresis loops and plastic (residual) displacements at zero loads. The lateral capacity of the wall was predicted very closely for most of the lateral drift levels. It shows that the modeling of load bearing wall sections by the fiber method has a very high precision. The ability to accurately predict the behavior of the wall and its cyclic properties including initial stiffness, yield point, stiffness degradation, strength and ultimate strength reduction, are the features of modeling by the fiber method.The pushover analysis is a relatively simple way to explore the nonlinear behavior of structures. As observed in Fig. 3, the lateral load capacity and the lateral stiffness of the wall were overestimated for lower lateral drift levels (i.e., up to 0.75% drift) and overestimated to a less extent for higher lateral drift levels. The overestimation of the wall capacity and stiffness, especially at lower drifts, can be attributed to the fact that analysis results for monotonic loading were compared with cyclic test results. Monotonic stressstrain relation of reinforcing steel generates higher stresses compared with the hysteretic stress-strain relation. The cyclic degradation associated with the implemented constitutive model for reinforcing steel influences significantly the wall lateralTable 1 Basic calibrated parameters in defining material stressstrain curve (Experimental study of THOMSEN and WALLACE 10)MaterialParameterBoundary (confined)Web (Unconfined)Parameters definitionfc / MPa47.642.8Concrete compressive strengthc0.00330.0021Concrete strain at peak compressive stressConcrete inEc/GPa31.0331.03Concretes modulus of elasticitycompressionr0.00370.0022Critical strain (where envelope curve starts following astraight line)r1.907.00Shape parameter (defining shape of the envelope)ft/MPa2.032.03Concrete tensile strengthConcrete int0.000080.00008Concrete strain at peak tensile stressEc/GPa31.0331.03tensioncrr1.21.2#3 rebar iny/MPa434Yield stressE0/GPa200Steels modulus of elasticitycompressionb0.02strain-hardening ratio#3 rebar iny/MPa395E0/GPa200tensionb0.0185#2 rebar iny/MPa448E0/GPa200compressionb0.02#2 rebar iny/MPa336E0/GPa200tensionb0.0350J. Cent. South Univ. (2015) 22: 27302738Fig. 3 Measured vs predicted load-displacement responsesload capacity and stiffness prediction, especially within the pre-yield and relatively low post-yield drift levels.3 Analytical studies3.1 Characteristics of structural model under studyIn order to assess the performance of the RC load bearing wall system under progressive collapse, three-dimensional model of 10-story structure was examined (Figs. 4 and 5). Overall dimension of plan was 21 m to 22 m. Typical story height was 3 m and the floors were composed of two-way slabs. Structure was located in high seismic risk areas. The seismic design of structure was based on the ASCE 710 12. The seismic response coefficient (Cs) of the RC load bearing wall was computed 0.273. Compressive strength (fc) of 28 MPa was used for the concrete. Concrete and steels moduli of elasticity were 2104 and 2105 MPa, respectively. The design yield strength was 400 MPa for both longitudinal and transverse reinforcements. In addition to the structural elements weight, a dead load of 6 kPa was applied to all of the floors. The service live load was 1.5 kPa for the roof and 2.5 kPa for other floors. Also, a perimeter wall weight of 7.5 kN/m was considered on every floor, except at the roof level. Structural design was based on the ACI 31814 13 concrete building code (ACI committee 318, 2014). After designing the RC load bearing wall structure, the thickness of all walls and slabs were defined as 250 mm and 150 mm, respectively.Fig. 4 Structural plan of RC load bearing wall system2734J. Cent. South Univ. (2015) 22: 27302738Parameters required in calibrating the nonlinear stressstrain curve of confined and unconfined concrete fibers in the compression were obtained from the results of experiments and the model proposed by MANDER et al 15. Constitutive defined models for concrete in compression were in the form of Fig. 6. The stressstrain curve of confined concrete was assigned to the concrete fibers of walls boundary and the stress strain curve of unconfined concrete was assigned to the concrete fibers of walls web. The same behavior of concrete in tension for unconfined and confined concrete was also considered (Fig. 6). To model the nonlinear behavior of rebar fibers, the trilinear stressstrain curve with a strain hardening factor of 0.01 and without strength loss was used. The maximum compression strain of reinforcement was 0.02 and the maximum tension strain was limited to 0.05 (Fig. 7).Fig. 6 Nonlinear stressstrain curves of concrete in compression and tensionFig. 7 Nonlinear stressstrain curve of rebar4 Modeling procedure of progressive collapseAnalysis considerations criteria for removing load bearing elementsFor RC load bearing wall systems in accordance with the terms of GSA and UFC regulations, the effect ofinstantaneous removal of load bearing walls located in the midsection and corners of the building must be considered. In both regulations, the required height to remove the load bearing walls is equal to the total height of the story. For instantaneous removal of (C-shaped) walls located at the corners of the buildings, GSA has recommended to remove load bearing walls in both directions with the length equivalent to the entire length of the perimeter wall or 4.5 m (15 ft) in each direction. However, UFC has defined this length equal to story height. In this research, the most critical condition recommended by the GSA was examined (Fig. 4(a). For instantaneous removal of load bearing walls in the midsection of buildings, GSA has recommended to eliminate 9 m (30 ft) of the wall. However, UFC has defined this length equal to double-story height (2H). According to UFC, simultaneous removal of flange and web of the load bearing walls, located in the middle of the sides is not possible and the specified removal length is only the web or flange length of the wall. In this work, the most critical conditions for instantaneous removal of load bearing walls located in the midsection of the building were evaluated as shown in Fig. 4.4.2 Nonlinear dynamic analysis procedureTo perform nonlinear dynamic analysis based on the GSA regulation, the load combination (DL +0.25 LL) was used. Instantaneous removal of load bearing elements was modeled according to the following procedures:Static analysis under permanent loads was performed and internal forces were determined at the ends of the element, which would be removed.By removing the load bearing element and replacing the internal forces of the removed element along with permanent loads, the model was revised and the structure was statically analyzed under permanent loads again. The results of this analysis were expected be the same as the first step.Using nonlinear dynamic analysis with initial conditions (to maintain stresses created by permanent loads applied to the structure), the equal and opposite forces that had been applied in the second step were imposed to the end of the removed element. These forces reached their maximum in a very short time in order to instantaneously remove the applied forces in the second step. Thus, the impact of instantaneous removal of the load bearing element was examined.Instantaneous removal time of load bearing elements accordi