外文翻譯---使用高級分析法的鋼框架創(chuàng)新設計

1、<p>　　使用高級分析法的鋼框架創(chuàng)新設計</p><p><b>　　1．導言</b></p><p>　　在美國，鋼結構設計方法包括允許應力設計法(ASD)，塑性設計法(PD)和荷載阻力系數(shù)設計法(LRFD)。在允許應力設計中，應力計算基于一階彈性分析，而幾何非線性影響則隱含在細部設計方程中。在塑性設計中，結構分析中使用的是一階塑性鉸分析。塑性設計使整個

2、結構體系的彈性力重新分配。盡管幾何非線性和逐步高產(chǎn)效應并不在塑性設計之中，但它們近似細部設計方程。在荷載和阻力系數(shù)設計中，含放大系數(shù)的一階彈性分析或單純的二階彈性分析被用于幾何非線性分析，而梁柱的極限強度隱藏在互動設計方程。所有三個設計方法需要獨立進行檢查，包括系數(shù)K計算。在下面，對荷載抗力系數(shù)設計法的特點進行了簡要介紹。</p><p>　　結構系統(tǒng)內的內力及穩(wěn)定性和它的構件是相關的，但目前美國鋼結構協(xié)會（AI

3、SC）的荷載抗力系數(shù)規(guī)范把這種分開來處理的。在目前的實際應用中，結構體系和它構件的相互影響反映在有效長度這一因素上。這一點在社會科學研究技術備忘錄第五錄摘錄中有描述。</p><p>　　盡管結構最大內力和構件最大內力是相互依存的（但不一定共存），應當承認，嚴格考慮這種相互依存關系，很多結構是不實際的。與此同時，眾所周知當遇到復雜框架設計中試圖在柱設計時自動彌補整個結構的不穩(wěn)定（例如通過調整柱的有效長度）是很困難

4、的。因此，社會科學研究委員會建議在實際設計中，這兩方面應單獨考慮單獨構件的穩(wěn)定性和結構的基礎及結構整體穩(wěn)定性。圖28.1就是這種方法的間接分析和設計方法。</p><p>　　在目前的美國鋼結構協(xié)會荷載抗力系數(shù)規(guī)范中，分析結構體系的方法是一階彈性分析或二階彈性分析。在使用一階彈性分析時，考慮到二階效果，一階力矩都是由B1,B2系數(shù)放大。在規(guī)范中，所有細部都是從結構體系中獨立出來，他們通過細部內力曲線和規(guī)范給出的那

5、些隱含二階效應，非彈性，殘余應力和撓度的相互作用設計的。理論解答和實驗性數(shù)據(jù)的擬合曲線得到了柱曲線和梁曲線，同時Kanchanalai發(fā)現(xiàn)的所謂“精確”塑性區(qū)解決方案的擬合曲線確定了梁柱相互作用方程。</p><p>　　為了證明單個細部內力對整個結構體系的影響，使用了有效長度系數(shù)，如圖28.2所示。有效長度方法為框架結構提供了一個良好的設計。然而，有效長度方法的使用存在著一些困難，如下所述：</p>

6、<p>　　1、有效長度的方法不能準確核算的結構系統(tǒng)及其細部之間的互相影響。這是因為在一個大的結構體系中的相互作用太復雜不能簡單地用有效長度系數(shù)K代表。因此，這種方法不能準確地測算框架單元實際需要的強度。</p><p>　　2、有效長度的方法無法獲取結構體系中內力非彈性再分配，因為帶有B1、B2系數(shù)的一階彈性分析只證明二階影響，但不是非彈性內力再分配。有效長度的方法只是保守的估計了最終承載大型結構

7、體系的能力。</p><p>　　3、有效長度方法無法測算的結構體系受負荷載下的失效模式。這是因為荷載抗力系數(shù)相互作用方程不提供在任何負載下結構體系的失效模式的信息。</p><p>　　4、有效長度的方法與計算機程序不兼容。</p><p>　　5、有效長度的方法在涉及系數(shù)K的單獨構件能力檢測時需要耗費比較長的時間。</p><p>　　隨

8、著電腦技術的發(fā)展，細部結構的穩(wěn)定性和整體結構的穩(wěn)定性這兩個方面，可以通過結構的最大強度測定來被嚴格對待。圖28.1就是這種方法的間接分析和設計方法。直接設計方法的發(fā)展被稱為高級分析，或者更具體地說，二階彈性分析框架設計。用這種直接的方式，無須計算有效長度系數(shù)，因為不需要規(guī)范方程包含的單獨構件能力檢測。憑借目前現(xiàn)有的計算技術，直接使用高級分析法技術框架設計是可行的。這種方法過去在辦公室設計使用時一直被認為是不切實際的。本章的目的是提出一個

9、切實可行的，直接的鋼框架設計方法，使用高級分析法產(chǎn)生跟荷載抗力系數(shù)法的相同的結果。</p><p>　　利用高級設計分析的優(yōu)點概述如下：</p><p>　　1、高級分析法是結構工程師進行鋼結構設計的另一個工具，它的通過不是強制性的，而是為設計人員提供靈活的選擇。</p><p>　　2、高級分析法直接獲取了整個結構體系和細部結構極限狀態(tài)的強度和穩(wěn)定性，這樣就不需要

10、規(guī)范方程包含的單獨構件能力檢測。</p><p>　　3、相比荷載阻力系數(shù)設計法和允許應力設計法，高級分析法通過直接彈性二階分析提供了更多結構性能的信息。</p><p>　　4、高級分析法解決了常規(guī)荷載阻力系數(shù)設計法中由于不兼容彈性全球分析和單元極限狀態(tài)設計的困難。</p><p>　　5、高級分析法與計算機程序兼容性良好，但荷載阻力系數(shù)設計法和允許應力設計法則無

11、法與計算機程序兼容，因為它們在過程中都需要有對系數(shù)K的單獨構件能力檢測的計算。</p><p>　　6、高級分析法可以得到整個結構體系彈性內力再分配的結果，并且節(jié)約高度不確定的鋼框架的材料。</p><p>　　7、過去在設計室使用高級分析法被認為不切實際，而現(xiàn)在則是可行的，因為個人電腦和工程工作站的能力正在迅速提高。</p><p>　　8、通過高級分析法測定的各

12、項數(shù)據(jù)都接近了荷載抗力系數(shù)法測定的那些數(shù)據(jù)，因為高級分析法對荷載抗力系數(shù)法的柱曲線和梁柱的相互作用方程進行了校準。因此，高級分析法替代了荷載抗力系數(shù)法。</p><p>　　9、高級分析法比較高效，因為它完全消除了經(jīng)常引起混淆的冗長的單獨構件能力檢測，包括荷載阻力系數(shù)設計法和允許應力設計法中的系數(shù)K的計算。</p><p>　　在各種高級分析法中，包括塑性區(qū)準塑性鉸法，彈性區(qū)塑性鉸法，名義

13、負荷塑性鉸法和改進塑性鉸法，推薦使用改進塑性鉸法，因為它保留了計算的效率和簡便性及實際應用的準確度。這個方法是對簡單的傳統(tǒng)的彈塑性鉸法的改進。其中包括一個簡單的修改，證明在塑性鉸位置截面剛度的逐步退化和包括細部兩個塑性鉸之間的逐步剛度退化。</p><p>　　表28.1中對常規(guī)荷載抗力系數(shù)法和高級實用性分析方法的關鍵因素做了比較。荷載抗力系數(shù)方法用來證明主要影響隱含在其柱強度和梁柱相互作用方程之中，而高級分析法

14、通過穩(wěn)定性的功能，剛度退化的功能和幾何缺陷方面來證明那些影響，在28.2中有詳細討論。</p><p>　　高級分析法持有許多鋼結構實際問題的答案，同樣地，我們推薦尋找有效地合理地完成框架設計方法提供給工程師，但這要符合荷載抗力系數(shù)規(guī)范。在下面的章節(jié)里，我們將提出符合荷載抗力系數(shù)鋼框架結構設計的高級先進實用分析方法。該方法的有效性將通過比較基于精確塑性區(qū)解決方案和荷載抗力系數(shù)設計分析及設計結果的細部和框架的實際案

15、例研究。大范圍的案例研究和比較可以這種高級方法的有效性。</p><p><b>　　2．高級實用性分析</b></p><p>　　本節(jié)介紹了一種消除規(guī)范單獨構件能力檢測的直接設計鋼框架的高級實用性分析方法。改進后的塑性鉸法是由簡單的傳統(tǒng)的彈塑性鉸法發(fā)展調整而來，實現(xiàn)了簡單和真實的反映了實際情況。下一節(jié)將提供了最終確認該方法的有效性的核查方法。</p>

16、<p>　　高級分析能夠驗證連接的靈活性。常規(guī)分析和鋼結構的設計通常在假設梁柱連接不是完全剛性或理想的固定下進行。然而，在大部分實際的連接是半剛性的并且它們的狀態(tài)介于這兩個極端的例子之間。在允許應力設計-荷載抗力系數(shù)規(guī)范，有兩類特定的建筑：FR（完全受限）結構和PR（部分受限）結構。荷載抗力系數(shù)規(guī)范允許通過“合理途徑”連接靈活性評估。</p><p>　　瞬間旋轉的關系代表了連接的狀態(tài)，已經(jīng)完成多方面

17、的試點連接工作和收集大批的瞬時旋轉數(shù)據(jù)。有了這個數(shù)據(jù)庫，研究人員已經(jīng)開發(fā)了數(shù)個連接模型，包括線性，多項式，B曲線，動力和指數(shù)。鑒于此，Kishi和Chen提出的三參數(shù)冪函數(shù)模型被采用了。</p><p>　　在使用高級分析時，幾何缺陷必須由框架單元加以塑造。幾何缺陷在構造或架設過程中導致不可避免的錯誤。對于建筑結構的結構構件，幾何缺陷的種類屬于非線性和非垂直的。明確建模和等效名義載荷被研究人員用來證明幾何缺陷。在

18、這一章節(jié)中，發(fā)展了基于進一步減小構件切線剛度的新方法。這種方法提供了一種簡易的途徑用來證明沒有輸入名義載荷或明確幾何缺陷的不完善的影響。</p><p>　　本節(jié)中描述的高級實用性分析方法僅限于受靜載的兩維支撐，無支撐，和半剛架。不考慮結構的空間狀態(tài)，并且假定有足夠的側向支撐防止側扭屈曲。假設W節(jié)就是這樣的節(jié)可以在無局部屈曲情況下發(fā)揮全塑性時刻能力。強軸和弱軸彎曲寬凸緣部分的研究都采用高級實用性分析方法。該方法可

19、被視為介于現(xiàn)在廣泛使用的常規(guī)荷載抗力系數(shù)方法和像在未來實際應用中塑性區(qū)的制定方法等的更嚴謹?shù)母呒壏治?設計方法之間的一個臨時的分析設計方法。</p><p>　　An Innovative Design for Steel Frame</p><p>　　Using Advanced Analysis</p><p>　　Introduction </p>

20、;<p>　　The steel design methods used in the U.S. are allowable stress design (ASD), plastic design (PD), and load and resistance factor design (LRFD). In ASD, the stress computation is based on a first-order elast

21、ic analysis, and the geometric nonlinear effects are implicitly accounted for in the member design equations. In PD, a first-order plastic-hinge analysis is used in the structural analysis. PD allows inelastic force redi

22、stribution throughout the structural system. Since geometric nonlinearity </p><p>　　The strength and stability of a structural system and its members are related, but the interaction is treated separately in

23、 the current American Institute of Steel Construction (AISC)-LRFD specification [2]. In current practice, the interaction between the structural system and its members is represented by the effective length factor. This

24、aspect is described in the following excerpt from SSRC Technical Memorandum No. 5 [28]:</p><p>　　Although the maximum strength of frames and the maximum strength of component members are interdependent (but

25、not necessarily coexistent), it is recognized that in many structures it is not practical to take this interdependence into account rigorously. At the same time, it is known that difficulties are encountered in complex f

26、rameworks when attempting to compensate automatically in column design for the instability of the entire frame (for example, by adjustment of column effective length). Th</p><p>　　This design approach is mar

27、ked in Figure 28.1 as the indirect analysis and design method.</p><p>　　In the current AISC-LRFD specification [2], first-order elastic analysis or second-order elastic analysis is used to analyze a structur

28、al system. In using first-order elastic analysis, the first-order moment is amplified by B1 and B2 factors to account for second-order effects. In the specification, the members are isolated from a structural system, and

29、 they are then designed by the member strength curves and interaction equations as given by the specifications, which implicitly account for seco</p><p>　　In order to account for the influence of a structura

30、l system on the strength of individual members, the effective length factor is used, as illustrated in Figure 28.2. The effective length method generally provides a good design of framed structures. However, several diff

31、iculties are associated with the use of the effective length method, as follows:</p><p>　　1. The effective length approach cannot accurately account for the interaction between the structural system and its

32、members. This is because the interaction in a large structural system is too complex to be represented by the simple effective length factor K. As a result, this method cannot accurately predict the actual required stren

33、gths of its framed members.</p><p>　　2. The effective length method cannot capture the inelastic redistributions of internal forces in a structural system, since the first-order elastic analysis with B1 and

34、B2 factors accounts only for second-order effects but not the inelastic redistribution of internal forces. The effective length method provides a conservative estimation of the ultimate load-carrying capacity of a large

35、structural system.</p><p>　　3. The effective length method cannot predict the failure modes of a structural system subject to a given load. This is because the LRFD interaction equation does not provide any

36、information about failure modes of a structural system at the factored loads.</p><p>　　4. The effective length method is not user friendly for a computer-based design.</p><p>　　5. The effective

37、length method requires a time-consuming process of separate member capacity checks involving the calculation of K factors.</p><p>　　With the development of computer technology, two aspects, the stability of

38、separate members and the stability of the structure as a whole, can be treated rigorously for the determination of the maximum strength of the structures. This design approach is marked in Figure 28.1 as the direct analy

39、sis and design method. The development of the direct approach to design is called advanced analysis, or more specifically, second-order inelastic analysis for frame design. In this direct approach, there i</p><

40、;p>　　The advantages of advanced analysis in design use are outlined as follows:</p><p>　　1. Advanced analysis is another tool for structural engineers to use in steel design, and its adoption is not manda

41、tory but will provide a flexibility of options to the designer.</p><p>　　2. Advanced analysis captures the limit state strength and stability of a structural system and its individual members directly, so se

42、parate member capacity checks encompassed by the specification equations are not required.</p><p>　　3. Compared to the LRFD and ASD, advanced analysis provides more information of structural behavior by dire

43、ct inelastic second-order analysis.</p><p>　　4. Advanced analysis overcomes the difficulties due to incompatibility between the elastic global analysis and the limit state member design in the conventional L

44、RFD method.</p><p>　　5. Advanced analysis is user friendly for a computer-based design, but the LRFD and ASD are not, since they require the calculation of K factor on the way from their analysis to separate

45、 member capacity checks.</p><p>　　6. Advanced analysis captures the inelastic redistribution of internal forces throughout a structural system, and allows an economic use of material for highly indeterminate

46、 steel frames.</p><p>　　7. It is now feasible to employ advanced analysis techniques that have been considered impractical for design office use in the past, since the power of personal computers and enginee

47、ring workstations is rapidly increasing.</p><p>　　8. Member sizes determined by advanced analysis are close to those determined by the LRFD method, since the advanced analysis method is calibrated against th

48、e LRFD column curve and beam-column interaction equations. As a result, advanced analysis provides an alternative to the LRFD.</p><p>　　9. Advanced analysis is time effective since it completely eliminates t

49、edious and often confused member capacity checks, including the calculation of K factors in the LRFD and ASD.</p><p>　　Among various advanced analyses, including plastic-zone, quasi-plastic hinge, elastic-pl

50、astic hinge, notional-load plastic-hinge, and refined plastic hinge methods, the refined plastic hinge method is recommended, since it retains the efficiency and simplicity of computation and accuracy for practical use.

51、The method is developed by imposing simple modifications on the conventional elastic-plastic hinge method. These include a simple modification to account for the gradual sectional stiffness de</p><p>　　The k

52、ey considerations of the conventional LRFD method and the practical advanced analysis method are compared in Table 28.1. While the LRFD method does account for key behavioral effects implicitly in its column strength and

53、 beam-column interaction equations, the advanced analysis method accounts for these effects explicitly through stability functions, stiffness degradation functions, and geometric imperfections, to be discussed in detail

54、in Section 28.2.</p><p>　　Advanced analysis holds many answers to real behavior of steel structures and, as such, we recommend the proposed design method to engineers seeking to perform frame design in effic

55、iency and rationality, yet consistent with the present LRFD specification. In the following sections, we will present a practical advanced analysis method for the design of steel frame structures with LRFD. The validity

56、of the approach will be demonstrated by comparing case studies of actual members and frames with th</p><p>　　2．Practical Advanced Analysis </p><p>　　This section presents a practical advanced an

57、alysis method for the direct design of steel frames by eliminating separate member capacity checks by the specification. The refined plastic hinge method was developed and refined by simply modifying the conventional ela

58、stic-plastic hinge method to achieve both simplicity and a realistic representation of actual behavior [15, 25]. Verification of the method will be given in the next section to provide final confirmation of the validity

59、of the method.</p><p>　　Connection flexibility can be accounted for in advanced analysis. Conventional analysis and design of steel structures are usually carried out under the assumption that beam-to-column

60、 connections are either fully rigid or ideally pinned. However, most connections in practice are semi-rigid and their behavior lies between these two extreme cases. In the AISC-LRFD specification [2], two types of constr

61、uction are designated: Type FR (fully restrained) construction and Type PR (partially restrained)</p><p>　　Connection behavior is represented by its moment-rotation relationship. Extensive experimental work

62、on connections has been performed, and a large body of moment-rotation data collected. With this data base, researchers have developed several connection models, including linear, polynomial, B-spline, power, and exponen

63、tial. Herein, the three-parameter power model proposed by Kishi and Chen [21] is adopted.</p><p>　　Geometric imperfections should be modeled in frame members when using advanced analysis. Geometric imperfect

64、ions result from unavoidable error during fabrication or erection. For structural members in building frames, the types of geometric imperfections are out-of-straightness and out-of-plumbness. Explicit modeling and equiv

65、alent notional loads have been used to account for geometric imperfections by previous researchers. In this section, a new method based on further reduction of the tangent </p><p>　　The practical advanced an

66、alysis method described in this section is limited to two-dimensional braced, unbraced, and semi-rigid frames subject to static loads. The spatial behavior of frames is not considered, and lateral torsional buckling is a

67、ssumed to be prevented by adequate lateral bracing. A compact W section is assumed so sections can develop full plastic moment capacity without local buckling. Both strong- and weak-axis bending of wide flange sections h