[雙語(yǔ)翻譯]--港航外文翻譯--碼頭結(jié)構(gòu)的動(dòng)力特性試驗(yàn)研究（英文）

1、Engineering Structures 33 (2011) 344–356Contents lists available at ScienceDirectEngineering Structuresjournal homepage: www.elsevier.com/locate/engstructExperimental evaluation of the dynamic properties of a wharf struc

2、tureRubén Luis Boroschek a,?, Hugo Baesler b, Carlos Vega ca Civil Engineering Department, Universidad de Chile, Blanco Encalada 2002, Santiago, Chileb PM Ingenieros S.A., Cerro Colorado 5030, Of. 703, Las Condes, S

3、antiago, Chilec GHD S.A., Apoquindo 4775, Of. 601, Las Condes, Santiago, Chilea r t i c l e i n f oArticle history: Received 23 January 2008 Received in revised form 9 October 2010 Accepted 11 October 2010 Available onli

4、ne 16 November 2010Keywords: Damping Wharf Health monitoring Pull-Back testa b s t r a c tThis paper presents the results from a series of experimental tests carried out to determine the damping characteristics of a sect

5、ion of a 375 m long pile-supported wharf structure under forced excitation. The test program was designed with two primary objectives: (1) to identify the fundamental damping of the structure by using structural microvib

6、ration signals produced by tides, wind and microtremors, and (2) to evaluate the variation of the dynamic properties as a function of response amplitude by applying initial displacements of varying amplitude to the deck

7、using a pull mechanism. Although the wharf was designed as a series of independent deck sections, the study revealed that the non-structural frames and piping supported on top of the wharf tie adjacent sections together

8、and have a significant influence on the dynamic behaviour, particularly in the longitudinal direction. Care must be taken in to provide sliding connections for wharf supported structures or to include the influence of th

9、ese elements in the original design. From our review of the properties identified under the different excitation levels, it was determined that the wharf has relatively linear behaviour with an equivalent viscous damping

10、 of about 3%. This is a good reference damping value to be used for the analysis of the pile-supported wharf structures under operational loads and low magnitude seismic events © 2010 Elsevier Ltd. All rights reserv

11、ed.1. IntroductionA fundamental aspect in the seismic design process ofstructures is the correct estimation of their dynamic properties as a function of the expected response and level of damage. Information obtained fro

12、m low level vibration testing of the existing structures can be used to improve the structural models and our understanding of their response to gravitational, operational and seismic loads.The verification and validatio

13、n of modelling recommendationsfor many common types of building structures has been very extensive. In contrast, much less has been done in this area regarding marine wharves. Although wharves typically have simple struc

14、tural systems, their dynamic behaviour is complex due to the soil–structure interaction, the interaction between wharf segments, and the interaction between the wharf structure and the supported equipment and systems. As

15、 a result, it is difficult to define unique models for the various load states and performance levels for wharves and even more complex to correctly select the energy dissipation capabilities for the different damage sta

16、tes of these structures.? Corresponding author. Tel.: +56 29784372; fax: +56 26892833.E-mail addresses: rborosch@ing.uchile.cl (R.L. Boroschek),hbaesler@pmingenieros.cl (H. Baesler), cvega@ghd.com (C. Vega).In the case o

17、f limited damage or operating conditions ofwharves with piles, researchers have used energy dissipation values that are based on results obtained in other types of structures such as bridges and buildings, but with very

18、limited experimental information on wharves.For the analysis of wharves subjected to operating loads orseismic loads, where there is little or no damage, different authors and design criteria recommend the use of a refer

19、ence value of about 5% of the critical damping ratio for energy dissipation [1,2]. Benzoni and Priestley [1] used a critical damping ratio between 5% and 7.5% for moderate or medium response levels, which is increased to

20、 10%–20% in cases of extreme demand and high damage levels. Donahue et al. [3] has used a similar value of 10% in cases of extreme demand and energy dissipation levels. However, some authors consider damping values of ab

21、out 5% for damage situations (e.g. [4]) when nonlinear elements are added in the analytical model with intrinsic energy dissipation. In general, it is accepted that for modelling purposes, values higher than 5% should be

22、 used when there is extensive damage [5]. The International Navigation Association recommends equivalent damping values derived from hysteretic damage models and, up to a certain level, discarding the base viscous contri

23、bution [6]. Taking this into account, equivalent values between 10% and 20% of critical damping ratios are considered.Although the values mentioned above are commonly acceptedby professionals, they must be experimentally

24、 validated. Due to0141-0296/$ – see front matter © 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.engstruct.2010.10.014346 R.L. Boroschek et al. / Engineering Structures 33 (2011) 344–356(a) Type ‘‘A’’. (b) T

25、ype ‘‘B’’.Fig. 2. Typical pier arrangement.Fig. 3. General view of top deck systems. Note the pipes and frames running in the longitudinal direction that may provide some degree of restraint between adjacent sections.usa

26、ge, etc.). It is relatively fast and economic, but not always accepted by professional designers because the identification is made with relatively low amplitude vibrations (maximum acceleration amplitudes of about 0.005

27、 g). These amplitudes are not representative for structures that have nonlinearities such as the interaction with non-structural elements or neighbour structures or nonlinearities of materials that are only present at la

28、rger amplitudes. A procedure to generate higher amplitudes is through Pull-Back testing (imposition of initial conditions). A description of these tests and their signal analysis procedures are described below.3.1. Pull-

29、Back testPull-Back testing consists of pulling on the structure to imposeinitial conditions (displacement and velocity) to a structure in order to generate an important response of the system. From the analysis of the re

30、sponse decay it is possible to determine the dynamic properties of the structure. This type of test presents several difficulties when applied to large existing structures in operation [7,8]. The principal difficulty is

31、related to the application of the load, which requires a strong support point and an accurate determination of the load magnitude to prevent damage to the test structure. Additionally, due to safety reasons, the test exe

32、cution typically requires stopping the operations along the structure. This situation necessarily implies the development of detailed studies about the condition of the structure and preparation of predictive computer mo

33、dels. All this requires longer preparation and execution times for the test and therefore, higher costs and risks.3.1.1. Parameter identificationTo identify the modal parameters from the structural responseto initial con

34、ditions, it is normally assumed that the decay cor- responds to a viscoelastic mechanism and therefore the response is the sum of harmonic functions (as in the case of several ex- cited degrees of freedom) with different

35、 frequencies, but whose amplitude decreases exponentially. The most common identi- fication techniques are the logarithmic decrement techniques used in single-degree-of-freedom (SDOF) systems and the Ibrahim Time Domain

36、Method (ITD) for multi-degree-of-freedom (MDOF) systems [9].The SDOF method can be used for SDOF systems, MDOF systemswhere only one mode is excited, or MDOF systems where it is possible to generate signals associated wi

37、th a single mode through filtering of the response record. Damping can be obtained based on the amplitude variation between successive or non-successive maxima or, in a more robust manner, from the slope of a curve corre

38、sponding to the maximum amplitude values(vn) as a function of the sequential numbers of those maxima (n) (i.e. a plot with a vertical logarithmic axis and a linear horizontal axis, ln(vn)vs · n). For the perfectly v

39、iscous case, the curve generated corresponds to a straight line. The slope of this curve is the value of the damping divided by the value of π. In practical cases, and in the presence of instrumental noise and influence

40、of various energy dissipation mechanisms, it is recommended to create a best-fit straight line to determine the slope. Also a segmental analysis can be used to establish the effects of amplitude on energy dissipation as

41、a function of amplitude. Then from the shape of the decay response, it is possible to know if the system presents a classical energy dissipation mechanism, such as friction or viscous behaviour, and whether the response

42、parameters change with the amplitude of the motion.When it is not possible to use the SDOF model, it is necessaryto identify all the frequencies, damping values and participation factors simultaneously. In ITD, an adjust

43、ment to the observed decay response is made through least squares; see the detailed procedure in Ibrahim Time Domain Method (ITD) for multi-degree- of-freedom systems [9].3.1.2. Design of the pull testA special system wa

44、s designed to carry out the Pull-BackTest [10]. This system was located between two sections of the wharf (Fig. 4(a)). The system consists of two bolted base plates, (Fig. 4(b)), located close to the wharf section expans

45、ion joint. During the test, these two plates are pulled towards each other using a connecting element and a hydraulic jack. In the middle of the connector there is a steel plate designed to break and act as a fuse (Figs.