使用不同的埃及地震规定分析学校现有建筑物的地震反应--文献翻译(共12页).doc

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1、精选优质文档-倾情为你奉上Seismic Analysis of Existing School Buildings UsingDifferent Egyptian Seismic ProvesionsI. Ezz El-Arab1aSeismic Analysis of Existing School Buildings UsingDifferent Egyptian Seismic ProvesionsjProcedia Engineering 14 (2011) 19061912Abstract This paper presents a comparative study for se

2、ismic analysis of a certain class of existing school buildings which are considered as one of the important and wide spread buildings in Egypt. The study focuses on a comparison between all versions of the Egyptian Code of Practice for loading (ECP-201), versions published in 1993, 2003, and the dra

3、ft of final version October, 2008, and the Regulations of the Egyptian Society of Earthquake Engineering (ESEE, 1988). Base shear and base moment values are calculated using all of the above mentioned seismic provisions. The controller straining actions of these provisions are then compared with tho

4、se obtained using response spectrum and time history analyses using real ground excitation of pervious earthquakes (Al-Aqba, 1995, Northridge, 1994, and El-Centro, 1940). All these earthquakes are scaled to be matched with the maximum ground acceleration for the study zone. It has been found that hi

5、gh variation between the base shear and base moment obtained using the ECP versions pecified different analysis methods and in comparison with the ESEE and Earthquake analysis. This high variation make the new ECP-201 (October, 2008) will be need to recontemplate. 2011 Published by Elsevier Ltd.Keyw

6、ords: Egyptian Code, Seismic, Earthquakes Analysis, Schools, Egypt.1. Introduction It is well known that there are three methods for structural earthquake analysis. These methods are the Equivalent Static Load method (ESL), the Response Spectrum Method (RSM), and the Time History Analysis (THA).The

7、(ESL), and the (RSM) methods are generally used for linear analysis of the dynamic response of structures. In various forms, (THA) method has been widely used in the earthquake-resistant design of special structures such as very tall buildings, offshore drilling platforms, dams, and nuclear power pl

8、ants. For a number of years; however, its use is also becoming more common for ordinary structures as well. The (ESL), and (RSM) analysis procedures were simplified from the general case by restricting consideration to lateral motion in a single plane. Only one degree of freedom was required per flo

9、or for this type of analysis. In recent years, with the advent of high-speed, desktop computers, and the proliferation of relatively inexpensive, user-friendly structural analysis software capable of performing three-dimensional modal analyses, such simplifications have become unnecessary. Consequen

10、tly, the new Provisions adopted the more general approach describing a three-dimensional modal analysis of the structure. When modal analysis is specified by the Provisions, a three-dimensional analysis is generally required except in the case of highly regular structures or structures with flexible

11、 diaphragms.2. Majoir changes of seismic provisions The research will present the significant difference points that have been applied to the seismic provisions in different ECP editions released from 1993 to 2008, and the ESEE. Table 1 illustrates the base shear formulas with the related parameters

12、 to present the major changes.Table 1: Major differences between the ESEE, and ECP (1993, 2008). The major difference between the ECP-1993 and the ECP-2003 was remarked by the new adoption of the response spectrum method that presented the pseudo acceleration anchored to Peak Ground Acceleration (PG

13、A). Also, the soil parameter has a big effect on the response spectrum curve. On the other side, the two newest provisions ECP-2003 and ECP-2008 have a similar base shear formulation except the existence of the importance factor I either in response spectrum or in the base shear equation which yield

14、s final identical base shear. It is clear from the initial comparison how the base shear value obtained from ECP-2003 and 2008, is greater than the value obtained of ECP-1993. The value of base shear that was obtained from the ECP-2008 and 2003 when used in the elastic theory it must be reduced by a

15、 factor of the 1.4 or 1.28 for ECP-2008 and ECP-2003, respectively. The ESEE presented the response spectrum method in additional to equivalent static load with many factors not taken into consideration in the ECP-2003 and 2008 like material, risk, and construction quality factors. All of these fact

16、ors are still neglected in all ECP editions till 2008.3. Case Study of School Buildings in Egypt The Egyptian General Authority for Educational Buildings has divided the school buildings to seven models according to two main items. The first is the capacity of class rooms, while the secondly is soil

17、 classification that depends on the school location. In the present paper, the middle of Delta region has been chosen for the studied cases. First school is the preparatory school in a small village called Seheim that contains 36 class rooms; divided on a ground floor plus four typical floors. The g

18、round floor is used for general services. Second type of school is the secondary school in a small village called El-Gaafria that contains 8 class rooms. The school includes a ground floor used as a services area and four typical floors containing the class rooms. Both cases have the same soil chara

19、cteristic that prevails in the middle of the Delta region. Besides, the selected schools have complete data obtained from the Egyptian General Authority for Educational Buildings. Comparison of code fundamental natural period with experimental values using the ampient vibration tests on the studied

20、cases has been presented in (Sobaih and Ezz El-Arab, 2010), where the natural time period of each case study was calculated using different Egyptian codes and compared with USA code (IBC 2006). Also the error percentage of the natural time period compared to the experimental time period was presente

21、d. The big error percentage is one of the major reasons that reflected in the results especially in ESL where the equivalent static force mainly depended on the calculated natural dynamic characteristics for the structure.4. Ground Earthquake Excitations Three different ground excitations are select

22、ed to match the seismicity of the school site. One of them is Al-Aqba earthquake, 1995 which shock Egypt in 1995, and the other two earthquakes are El-Centro, 1940, and Northridge, 1994. Figure 1a shows the acceleration time history of the three earthquakes ground excitation Al-Aqba, 1995, El-Centro

23、, 1940, and Northridge, 1994, respectively. Both the El-Centro, 1940 and Northridge, 1994 earthquakes are scaled to match the seismic requirements for the zone of cases study as it is clear in Figure 1b. This scaling of earthquake ground acceleration will make the results comparison with other dynam

24、ic and equivalent static load methods are more rational. The response spectrum of the above mentioned earthquakes excitations are presented in Figure 2 in the longitudinal and transversal directions, respectively.5. Numerical Results The results of RSM and THA, using the indicated three ground excit

25、ations, are compared with those obtained from the equivalent static loads using all the Egyptian codes editions and the ESEE regulations for considered school buildings. This comparison is illustrated in Figures 3, 4, and 5. The results of the equivalent static method for ESEE, ECP-1993, ECP-2003, a

26、nd ECP-2008 are presented in Figure 3 for the school building case-1. The analysis results are presented in both longitudinal and transversal directions of the school building. To get a clear vision of the response of each technique analysis as compared to the most accurate analysis of the time hist

27、ory analysis for the Egyptian earthquake excitation Al-Aqba, 1995, an error factor E was calculated as following: E= A analysis technique A analysis of THA (Al-Aqba, 1995) x 100/ A analysis of THA (Al-Aqba, 1995) (1) Where: A is the absolute peak response of school building by different earthquake a

28、nalysis techniques, i.e., ESL, RSM, or THA. The values of E the error percentage are listed in Table 2. The maximum base shear force value from the ESEE has good agreement with those from the T.H.A. due to Al-Aqba, 1995 earthquake excitation. Where as the base shear value due to ECP-1993 is very sma

29、ll with unexpected values having an error percentage of -88%. The ECP-2003 and 2008 have results more logical compared to the old version of ECP where the error percentage dose not exceed 28%. It is worthy to note the insignificant difference between the results of base shear and moments in both dir

30、ection of school building when it is compared to the other analysis methods R.S.M. and T.H.A.; this can be explained the weakness of this approximate method that is not effected by the change of building stiffness in both directions like the others methods. ECP-2008 has underestimated base shear and

31、 moment especially the values that is presented in Figures 3,4, and 5 should be divided by 1.4, 1.28 for ECP-2003 and ECP-2008, respectively to has the working values that will be compared to others codes where other codes results are in working state.Table 2: The error percentage (E) due to differe

32、nt analysis techniques compared to T.H.A.Technique using Al-Aqba earthquake The maximum base shear and moment due to response spectrum analysis techniques are presented in Figure 4 in the longitudinal and transversal directions, respectively. The results due to ECP-2003 by (RSM) are more closed to b

33、ase shear with the earthquake analysis due to AlAqba, 1995 compared to (ESL) by the same code ECP-2003. Figure 5 presents the earthquake analysis results of the three different ground excitation earthquakes, Al-Aqba, 1995, El-Centro, 1940, and Northridge, 1994, respectively. Despite of the unified v

34、alue of the three peak ground excitation to match the seismcity zone, there is a big change between the bases shear and moment. The reason for may be attributed to different frequency contents of three different earthquakes. This is clear from the response spectrum curves as shown in Figure 2. Frequ

35、ency content strongly affects the response characteristics of the structure. In structure, the ground motion is amplified the most when the frequency content of the motion and natural frequencies of the structure are close to each other. Also, the difference between the duration of strong motion has

36、 an effect on the results. Duration of strong motion has a pronounced effect on the severity of shacking, as it is clear in Al-Aqba, 1995 compared to El-Centro, 1940. A ground motion with moderate peak acceleration and long duration may cause more damage than a ground motion with a large acceleratio

37、ns and shorter duration. The straining actions that are generated from the Northridge earthquake compared well with Al-Aqba, 1995 earthquake contrary to El-Centro, 1940. This can be explained by the large difference in the response spectrum curve behavior of El-Centro earthquake compared to the othe

38、r earthquakes, as shown in Figure 2.6. Conclusions A comparative numerical analysis based on all available earthquake resistance techniques that used in the Egyptian code provisions started from (201-1993, 2003) and ended by (201-2008), and ESEE-1988 regulations. Earthquake analyses with different g

39、round excitations also are presented using the (T.H.A) method. The results of this numerical investigation are compared with regard to the base shear and moment calculated using the Equivalent Static Load (ESL) and the simplified Response Spectra Method (RSM) to assess and verify the impact of utili

40、zing any of these methods on the response of school buildings in Delta of Egypt. A practical emphasis is aid to discuss the influence of response modification factor introduced in ECP-2008. Relying on the investigations and discussions presented in this study, the following conclusions can be drawn

41、out. Egypt still suffers from the lack of available data of time history records for earthquake eventsregistered in Egyptian land. The basis for the ESL procedure and its limitations were discussed above. It is adequate for mostregular structures; however, the designer may wish to employ a more rigo

42、rous procedure for thoseregular structures where the ESL procedure may be inadequate. Extreme variation in the base shear and moment obtained from ECP-1993 compared to othersECP-2003, 2008, and ESEE-1988 with error percentage exceeding 90%. The simplified ESL and RSM analysis carried out on the midd

43、le of Delta-Egypt, in peak groundacceleration and soil conditions, revealed that the normalized base shear and base moment obtainedusing the ECP editions were less matched with real earthquake time history analysis results with errorpercentage reaching to 90%. The study provides the importance to av

44、oid any ignoring the seismic design on the structures withheight limitations, and the seismic zone in which the structure exists. Earthquake resistance of school buildings in Egypt need to be reevaluated considering the significantresults that presented in the study, and adopt retrofitting for those

45、 schools with insufficient resistance.References使用不同的埃及地震规定分析学校现有建筑物的地震反应摘要 本文提出一种对地震动力响应分析比较研究的某一类学校现有建筑物,被认为是一种重要的和广泛传播的建筑在埃及。着重研究比较各种版本的埃及实务守则（ECP），版本有1993年，2003年，还有2008年10最终版本的草案以及埃及社会规定的地震工程（ESEE）。地基剪力和地基基的时刻值计算使用上述所提到的地震规定。该控制器下坠的行为,比较了本规定使用的可比性进行频谱分析和使用真实的历史地震地面激励透光的时间分析。所有这些地震是依比例决定到最大匹配的地面加

46、速度为研究区。人们已经发现，地基剪力和地基的时刻在获得ECP版本的差异指定不同的分析方法,在比较ESEE和地震分析。这个巨大变化使新的ECP - 201(2008年10月)将需要重新被思考。关键词:埃及代码,地震,地震分析、学校、埃及。1、介绍 众所周知,有三种方法来构造地震分析。这些方法是等效静载法(ESL),反应谱法(RSM),和时程分析(THA) 的（ESL）和（RSM）的方法一般用于非线性分析的动态响应。（THA）的方法，以各种形式，被广泛应用于抗震设计的特殊结构,如非常高的楼房、海上钻井平台、大坝和核能等建筑物。,然而，多年来,它的使用也变得更加普遍。（ESL）和（RSM）分析程序简

47、化是，在一般情况下通过横向运动限制在一个平面上的考虑。每层只有一个自由度是需要这种类型的分析。近年来,随着高速、台式电脑、和相对便宜的，用户评价较好的结构分析软件，能够进行三维模态分析增殖的到来，这样的简化已成为不必要。因此,采用新规定的更普遍的方法描述三维结构的模态分析。模态分析是指定的规定, 一个三维分析的要求通常被要求除了常规结构或结构高度灵活的设置。2、地震中的重要规定这一研究将会反应出已被广泛应用于分的地震在不同版本的规定从1993年到2008年版本的显著差异。表1说明了抗剪公式基础的相关参数呈现大的变化。表1:ESEE与ECP之间的重大变化(1993、2008)。参数 ESEE,1

48、988 ECP ECP-1993 ECP-2008等效静载(ESL) V=Cs Wt V= Z.I.C.K.S.W F b =S d ( T1)W / g Cs=Z.I.S.M.R.Q Sd(T)是设计反应谱,它涉及 ( ag ,S,R,T,I,)地震风险参数Z=(0,0.02,0.04,0.08)g Z=(0.1,0.2,0.3) ag=(0.1,0.125,0.15,0.2,0.25,and0.3)g类别因素重要性 I=1,1.3, and1.5 I= 1 or 1.25 I = 0.8,1,1.2, and 1.4(增加地震安全) 结构抗力系统 0.67 S 3.20 0.67 K 1.33 2R7现场反应因素 F=1.0,1.3, and 1.5(土类) S=1,1.15 OR 1.3 S与土壤类和谱型时期影响 T = (0.09H) / d C =1/15 T S T是有关期间（TI）修正系数