土木工程毕业设计译文

1、指导教师评定成绩(五级制)：指导教师签字：附件C：译文 3.从地震中学习岩土工程方面在地震中涉及的教训, 思考传播路径和地基场地土对地震动的影响。传播路径和场地土对地震的影响决定于地震的类型，板间地震或者板内地震有很大的不同。对于板间地震。传播路径和当地土壤条件，反映地震源头基本信息，就像是带通滤波器一样。1906和1989年圣弗朗西斯科恶劣的土壤条件，1977布加勒斯特和1985墨西哥市场地条件对地震有巨大的影响，掩盖了地震源头特征（见2章）。对于板内地震，它的特征是高频运动，而场地条件对于地震的影响降低了。当发生地面运动显著放大时，值得注意的是浅层土壤沉积物和土壤液化情况的观察。1811新

2、马德里地震期间土壤液化造成严重的地震破坏（8级以上），同时在一片区域没有明显的断层。土壤沉积物液化也在新潟和神户地震的造成非常重要的影响（图3.6）。软土，山谷或者高山会产生强烈的地面运动。墨西哥就是山谷和软土影响最好的实证案例（图3.7）。建筑物和建筑空间的高密度是影响地面运动一个非常重要的因素。特别是在软土条件下，是地面运动的一个重要的放大因素。在神户地震的记录中，这种效应对地面运动的放大有可能起了一个重要的作用，神户地震地面运动在源头处是缓慢的,但地面运动的场地是在人口非常密集的地方。台北101大楼安装后引起了许多争论，由于建筑工地上持续的人员数量的增加趋势和地面运动的幅值变化。工程方面

3、的地震参考课程旨在提供地震观测结果再用于建筑设计实践。震源深度对地震特性有相当大的影响力。地表水源对于减少震中周围地区地震破坏有一定影响（可以从加州和安那托利亚地震看出），而深源影响面积大（例如，米却肯州，弗朗恰地震），在远离震中的位置造成很大破坏（见章1）。破裂区域，其特点是长度和宽度直接影响地震震级和时间。断层附近的地面运动具有方向性，如断层破裂方向的函数（在很多情况下沿断层表面进行位移观测非常重要，图：3.8），注意区别并行和正常的地面运动的特点非常重要。在洛马普列塔北岭,神户,科喀艾里和集集地震这种指向性非常明显。对于近场位置（从震中距离15-20km的区域内）的地震的特点与远场地址是

4、非常不同的。在北岭获得的三个方向加速度、速度和位移，在神户和集集地震证明是非常重要的。近场位置的地表源头,甚至轻微的地震震级就可以产生高水平的峰值加速度和速度。例如1999年雅典，中度地震就可以产生的高加速度。在重现期内，对于一个指定地点的地震特征，板间和板内地震是非常不同的。因为前者沿着确定的线路移动，而后者的特征是在一个地区震中位置是不确定的和不断变化的。板间地震可以使用的统计方法，相反，板内地震由于在同一地点没有足够的数据而不能使用统计方法。总结所有这些方面，结果表明，有三个主要的地震类型：板间地震、板内地震和深度板内地震。地震危险性和地震危险性分析必须在这个地震类型分类的基础上进行。3

5、.3结构缺陷的教训经过过去那些重大的地震，好的和差的建筑性能的差异从不同的角度可以提供许多经验（麦克卢尔1989年，马佐拉尼2002年，景苦2002年和马佐拉尼2003年）。参考这些经验教训的分析结果提升分析方法。根据当地地震运动采用合适的抗震设计必须考虑地震的所有特征：板内,板间,近场和远场位置和场地的影响力,接近震源的场地功能。必须特殊区别特征值(地震结果特征)和可用功率(功能结构的特性)。针对特殊情况下的地震破坏,使用规范条文不能完全保证结构不发生过度的塑性变形，因为这些规范条文仅仅参考的正常地震。因此在有这种特殊地震的场地情况下修建建筑，必须采用改进的设计方法（能够保证结构的整体承载力

6、）。特殊地震可以定义为那些没有考虑规范或以错误的方式考虑但地震时的实际强度比设计的高一些的那些地震。这个定义之后，大多数破坏性地震的可归类成这个类别（Mazzolani，2002）。在特殊情况下，抗震设计规范不防范结构发生过度的塑性变形。必须识别出潜在失效的地方，并且保证发生延性变形的位置有较好的延展性。因此，细节部位良好的延展性和冗余有利于防止结构崩溃提升结构安全性。一些次要结构构件（如楼梯）和非结构构件（如硬的填充墙）的强度和刚度不被认为是抗侧力体系的一部分，可能会强烈地影响建筑物的地震反应，尤其是在这样的元素的分布情况不受控制的情况下。根据经验，连续地震可能使建筑逐步弱化甚至最终崩溃。在

7、1977弗朗恰地震期间布加勒斯特一栋33层高的建筑物倒塌，而在在1940地震期间，该建筑有31处损坏。3.4减小地震风险的经验过去这么多的地震提供的经验表明，地震风险可能与城市以及建筑水平相关。城市地震灾害的经验表明，应该采取大规模的改进措施来减小严重地震下的破坏结果。要避免人口领域的高密度接近标准，特别是在土壤条件较差的情况下。最坏的例子就是圣弗朗西斯科和神户地震，在一个密集的城市是一个地区出现了断层和易液化的场地。必须特别注意供水系统在一个地震多发区重要性。由于地表断层线穿过大坝，同时水闸也被破坏，该康坝在台湾地震中严重破坏（图3.16）。由此产生的结果是储藏水不淹没下游，但中断了一段时间

8、。震后应急的战略中心，例如医院，消防站和电力设施，警察总部等，必须保证受地震影响后损坏较小并且主要道路网络的通畅。墨西哥市，加利福尼亚地震，许多医院都严重受损，以至于这些建筑震后都无法使用（图3.17）。世界上许多国家和城市都有很多建筑属于文化遗产, 他们很容易受到地震灾害。这些建筑绝大多数没有抗震设计，所以他们缺乏基本的抗震功能，没有配备足够应对地震作用的准备。由于这一事实，众多的历史古迹，在过去的强烈地震中损坏（图3.18）。这是一种责任，专家应该采取新的结构措施来保护的纪念性建筑（mazzolani，2005，2009）。地震后的火灾蔓延是一个大问题，这是主要由天然气管道产生的危害。19

9、06圣弗朗西斯科，还有，1995神户地震，都可以被记为不好的例子，震后火灾产生破坏可能比地震本身更严重（图3.19）。每个潜在的可能发生地震的区域，必须有许多连通的符合规范的道路网络。特别是在意大利的地震，由于非常狭窄的街道，造成了巨大的问题（图3.20）。要保证某些工程如桥梁，水坝或其他的安全性，以防止其地震塌陷在应急期间对城市系统的性能的影响。在洛马普里埃塔地震，神户地震和台湾地震，很多最重要的桥梁倒塌，对破坏的地区产生很大的交通困难（图3.21）。为了评估大地震带来的经济后果，将以前的地震灾害中，当地政府和业主损失数据，用于有效的预测相应的措施来减少的经济损失。一场毁灭性的地震是相对罕见

10、的事件，但是在大的建筑使用期间可能发生一次或两次一般的地震，这是可能的，这样的地震不会影响建筑物的使用。因此，在这种情况下，根据设计理念，结构设计已经准备好应对最大可能发生的地震破坏，所以在一般地震情况下不会崩溃，但有一定程度损伤。 以往地震中，上述设计思想在结构设计中可以减少非常多的损失（尤其在北岭和神户地震的情况下）表明，正常地震活动下的建筑重建财务成本太高，即使富裕国家都很难承担。 这种情况迫使专家们开发了一种新的设计理念，基于明确的、可量化的性能标准，考虑地震各方面表现和地震危险水平。一些低竖立建筑物和桥梁倒塌导致部分生活线路障碍和地震后火灾的模拟训练可以让人们对于一个毁灭性的地震期间

11、会发生什么有一个真实的概念。考虑结构构件连接充分性和各构件脆性的建筑经验：钢材板和木材板在细节上表现非常好。混凝土板和石膏护套板很容易发生开裂破坏，尤其是在高柔建筑案例中。预制混凝土填充墙面板的连接必须小心，避免损坏。建筑外表面施工必须足够仔细以防止表面相对滑动。尤其必须特别注意外幕墙的支护，这是非常容易发生位移的的构件。新的结构设计方法，建立在多层次的可能发生地震基础上，偶然的，罕见的，非常罕见，容许后果无损伤的，可修复的损伤的，和不可修复但人员可以生存的损伤。规范规定只考虑对不同级别的地震下最小值的保证，所以地震情况下建筑会产生一些损伤，并且需要修理。如果业主想要避免任何建筑功能中断，他可

12、以请设计师加强结构的强度和延展性，从而减少甚至消除可能由地震产生的损伤。 在可能发生罕见地震或者中度地震的地震区，必须采用特殊的设计方法，在这些地震区一些简化的设计方法就可以保证地震风险的减少。3.5抗震设计经验3.5.1两个重大事件中的抗震设计理念在1906年4月的一个世界上最大的地震之一震惊了加利福尼亚州旧金山市,同时造成很大的破坏，和1000多人死亡。这次地震的结果是马车成为了主要的运输工具,如图3.22所示。这个事件是具有非常重要意义的,因为它代表了人类第一次开始科学的分析加州断层对现代地震的作用。一群具有创造性的工程师,根据观测到的地震损伤开始研究,构思和设计不同地震级数情况下的结构

13、性解决方案来解决问题。这种创造性的工作进行了100年时间,一直延续到今天。在抗震设计历史中，关键的里程碑进展如下（elsessner，2004）：建筑最初的抗震设计是基于静力风荷载的相似性；在20世纪30年代早期建筑的动态响应概念和建设时期的重要性概念，取得了一定的进步；在20世纪50年代由于加速度反应谱法的提出增强了动态响应的概念；从1950到1980由于分析方法的提高结构构件非线性运动的知识增加了； 1980至今，复杂计算机程序的开发和持续发展，促进了对复杂结构的设计，和其非线性行为的研究。1995年1月，几百年来一直安静坐落在日本中部神户附近大海下的一个地质断层,突然开始打破，产生了一个

14、世界历史上著名的毁灭性地震，造成神户和邻近城市房屋倒塌,成千上万的人死亡。思考运输工具的演变,从旧金山的马车，到神户的高速列车,再到阪神高速公路的崩溃的景象,如图3.23所示 如果地震的后果仍然是很几百年前一样，那么抗震设计的进展在哪里?答案是与实际相关，从圣弗朗西斯科地震和北岭神户地震期间，大多数事件发生在远离城市中心地区。因此，专家们不能展示一个人口稠密的城市发生地震的结果。现有的规范规定只考虑地震在正常条件下发生的，因为记录的是远离地震源头的地震运动，在其传播过程中存在很大的衰减，这是在北岭和神户的第一次地震中靠近震中位置记录下来的，观察到远离震源和靠近震源的差别。这些事件是非常重要的，

15、因为从他们开始了特殊地震设计的一个新的阶段。特殊的地震是由mazzolani（2002），gioncu和mazzolani（2003）以下列方式定义的：实际作用比假设更大；设计过程中，所有的实际情况不会被完全考虑进去；在设计过程中已经考虑实际情况，但以一个错误的或不完整的方式；正确考虑实际情况,但是由于以往地震已经产生一些损坏，一段时间后结构部分失效；正确的考虑了地震作用进行结构设计，但施工处理得不好，由此存在的结构缺陷比材料质量不符合设计强度更加严重。从圣弗朗西斯科地震和神户地震九十年过去了，在这期间，耗费了大量人力财力，已经研究了许多可能的合理的疑问，并且编写在了抗震设计领域中。事实上，地

16、震学家已经认识到地震是由断层引起的，他们能够确定，用今天的现代方法可以进行空间监督（如GPS）构造板块的运动。今天的结构工程师分析方法，利用计算机专用程序，可以准确的评估结构响应和结构复杂运动。因此，第二个问题是有道理的：为什么当结构处于地震带时，不能使用一些非常可靠的值在完全安全的条件下进行结构设计？答案是很难确定结构部位的地震危险性并且将其转换为在一些适当的地震作用下的结构响应。3.5.2三道防线减少未来地震损失取决于在国家这一级采取的策略。这里有三道防线。1.对即将发生的地震进行预测，立即指出他们的位置和重要性，指出是短期，中期或者长期。2.在地震活跃地区限制重要的建筑。3.在地震活跃区

17、进行抗震结构设计。并且在抗震设计中采取先进方法，必须在可能发生地震的线路上进行分析。译文原文出处：Earthquake Engineering for Structural Design London and New York ：Spon press，2011：79-972015.5.133.Learning from Earthquakes 79The geotechnical aspects of earthquakes are involved with the lessons considering the influence of travel path and site soil

18、on the ground motions.- The influence of travel path and site soil depends on the earthquake type,being very different for interplate or intraplate earthquakes.- For interplate crustal sources, the travel path and local soil conditions modify the basic characteristics of the source, acting as the ba

19、nd-pass filters. The bad soil conditions of 1906 and 1989 San Francisco, 1977 Bucharest and 1985 Mexico City have a great influence on site ground motions, overshadowing the source characteristics (see Chapter 2).- For intraplate crustal earthquakes, characterized by high-frequency movements, the in

20、fluence of site conditions is more reduced. Notable exceptions have been observed in case of shallow soil deposits and soil liquefaction, when significant amplification of ground motions can occurs.The soil liquefaction during the 1811 New-Madrid earthquake produced a very strong earthquake (with ma

21、gnitude over 8) in a region without evident faults. The soil deposits and liquefaction played also a very important role during the Niigata and Kobe earthquakes (Fig. 3.6).- Soft soil, valley or relief effects can produce important ground motion amplifications. The Mexico-City is the most demonstrat

22、ive case about valley and soft soil effects (Fig. 3.7).- The presence of buildings and the high density of built-space can be a very important factor, producing an important amplification of ground motions,especially in case of soft soil conditions. It is possible that this effect has Figure 3.6 Ove

23、rturning of some buildings during the Niigata earthquake, due to the soil liquefaction (USGS, nd)80 Earthquake Engineering for Structural DesignFigure 3.7 Amplification of ground motions in Mexico City due to soft soil and valley effect (Gioncu and Mazzolani, 2002) given an important contribution on

24、 the very high amplification of records in the Kobe earthquake, where the magnitude of source was moderate, but the recorded ground motions in densely erected areas were very high.Many debates arose after the erection of Taipei 101 Building, due to the increasing trend of the number and the values o

25、f magnitude of ground motions that occurred under the building site.The engineering aspects of earthquakes refer to the lessons intended to present the seismological observations at the level to be used for building design practice.- Focal depth has a considerable influence on the earthquake charact

26、eristics.Surface sources have influence on a reduced area around an epicenter (see Californian and Anatolian earthquakes), while the deep sources affect a large area (for instance Michoacan and Vrancea earthquakes), producing large damage at locations situated far from the epicenter (see Chapter 1).

27、- Rupture areas, characterized by length and width, directly influenceearthquake magnitudes and durations.- Ground motions in near fault zones are characterized by directivity, as a function of the direction of the fault rupture (in many cases very important surface displacements along the fault are

28、 observed, Figure 3.8). It is veryLearning from Earthquakes 81important to note the difference between the characteristics of parallel and normal ground motions. This directivity was very evident during the Loma Prieta, Northridge, Kobe, Kocaeli and Chi-Chi earthquakes.- For the near-field sites (an

29、 area within a distance of 15-20 km from the epicenter) the earthquake characteristics are very different in comparison with the ones recorded at the far-field sites. The three directions recorded of accelerations, velocities and displacements obtained at Northridge,Kobe and Chi-Chi prove this very

30、important aspect.- For surface sources in the near-field sites, even moderate earthquakes in magnitude can produce high levels of peak accelerations and velocities.The 1999 moderate Athens earthquake produced high accelerations.- Recurrence periods, characteristic for a given place, are very differe

31、nt for interplate and intraplate earthquakes, because the former move along a very well determined fault, while the latter are characteristic for an area,where the epicenter positions are undetermined and in continuously changing. For interplate earthquakes it is possible to use statistical methodol

32、ogies, which, in contrast, are useless for the intraplate earthquakes due to the absence of sufficient data on the same site.Examining all these aspects, it results that there are three main earthquake types: crustal interplate and intraplate earthquakes, and deep intraslab earthquakes. Both earthqu

33、ake hazard and seismic hazard analyses must be carried out on the bases of this classification of earthquake types.Figure 3.8 Surface rupture effects during 1906 San Francisco earthquake(USGS, nd)82 Earthquake Engineering for Structural Design3.3 LESSONS FOR CONSTRUCTION VULNERABILITYDuring the last

34、 important earthquakes, the difference between good and poor building performances can deliver many lessons regarded from different points of view (McClure, 1989, Mazzolani, 2002, Gioncu and Mazzolani, 2002, 2003).The analysis aspects refer to the lessons for improving the analysis methodologies.- F

35、or a proper seismic design the estimation of seismic actions must consider all characteristics of earthquakes: interplate, intraplate, intraslab,near-field or far-field position and site influence, in function of site position related to the source.- Incorporating in the analysis the checking of rig

36、idity, strength and ductility is a measure, which mostly affects the code attitude to reduce the damage and to prevent collapse.- Special distinction must be made between required values (resulting from earthquake characteristics) and available capacity (function of the structure features).- Designi

37、ng structures using code provisions does not always safeguard against damage in case of exceptional earthquakes, because they refer to normal earthquakes only. Therefore, an improved robustness (overall load bearing capacity which a structure is able to provide) must be provided to the structure whe

38、n such exceptional earthquakes are foreseeable in the building site.- Exceptional earthquakes can be defined as the ones not considered in the codes, or considered in a wrong way, but also when the actual intensity of the earthquake is higher than the design one. After this definition, the majority

39、of damaging earthquakes can be framed into this category (Mazzolani, 2002).- In case of exceptional earthquakes, the design code does not safeguard the structure against excessive plastic deformations. Potential failure modes must be identified and ductility should be provided at all locations where

40、 plastic deformations occur. Therefore, detailing for ductility and redundancy provide safety against collapse.- Stiffness and strength of some secondary structural elements (e.g.staircases) and non-structural elements (e.g. stiff infilled walls), which are not considered as a part of the lateral fo

41、rce-resisting system, may strongly affect the seismic response of buildings, especially in case of uncontrolled distribution of such elements.- Buildings that experience successive earthquakes may suffer progressive weakening or eventual collapse. From the 33 high buildings collapsed in Bucharest du

42、ring the 1977 Vrancea earthquake, 31 were partial damaged during the 1940 earthquake.- Traditional code provisions consider methodologies based on seismic forces, but in the last period the interest seems to move towards methodologies based on seismic displacements.Learning from Earthquakes 83The st

43、ructural conformation aspects refer to the lessons to improve the global behavior of the structure, using appropriate constructional rules.- Uncertainness on the seismic input and structural response requires a particular emphasis on conceptual design and detailing aspects rather than on the analysi

44、s issue.- Well-conformed, well-detailed and well-constructed buildings have the chance of good performance during large earthquakes, without collapse or excessive damage, even if the analysis does not consider all the behavioral aspects in a correct way.- Well-conformed structure means well-coordina

45、ted architectural and engineering aspects, which requires that the structural engineer should be involved early in the conceptual design.- Poor construction practice and lack of quality control can lead to severe damage or collapse (see 1999 Kocaeli earthquake).- Building horizontal and vertical con

46、formations on seismic performance are recognized to be of primary importance. Buildings having irregular in plane shapes (in L, U or T or corner buildings) and uncontrolled setback elevations or soft levels generally perform in a poor way. These irregularities must be avoided or at least minimized (

47、Fig. 3.9).- Buildings having no uniform distribution of resistant elements in plan have shown a bad performance, by experiencing severe tensional effects.- Special attention must be paid to the horizontal diaphragms (roof and floor systems) in order to uniformly transfer the seismic forces to all ve

48、rtical resistant elements.- Severe pounding damage can result when adjacent buildings do not have adequate separation, giving enough space to move independently without touching. During the Mexico City earthquake a lot of damage was produced due to these poundings (Fig. 3.10).- Weak columns and stro

49、ng beams configuration, resulting for large span multi-story frames, can give rise to column failure and global structural collapse.- Dual structures (moment-resisting frames combined with braced or infilled frames) generally performed very well during the last earthquakes, provided that bracings do

50、 not create some discontinuities. But in some cases, when the infilling is not controlled by the designer, due to the irregularity in distribution, it is preferable to use frames only.84 Earthquake Engineering for Structural Design Figure 3.9. Collapse of corner buildings; (a) Bucharest RC building;

51、 (b) Kobe steel building (courtesy of Fischinger et al, 1998) - Discontinuities of mass, stiffness and strength in elevation give rise to local damages very difficult to avoid. Soft stories create hazardous conditions. During the Kocaeli (Turkey) earthquake many buildings having “pilotis structures”

52、 (free frames at the first level and rigid walls above) collapsed (Fig. 3.11). The conformation of structural element refers to the lessons to improve the local behavior of the structure.- The weakest points in building structures are typically the connectionsamong structural elements. Designing ade

53、quate connections is normally more difficult than providing adequate strength and ductility to structural members. Many structural failures during 1994 Northridge and 1995 Kobe earthquakes have been caused by inadequate detailing of connections (Fig. 3.12).- Overall collapse may occur when local str

54、ength and ductility of structural elements (columns, beams and joints) are insufficient. For steel structures, the most known case is the Pino Suarez building, collapsed during the 1985 Mexico City earthquake, due to lack of ductility of trusses and columns (Fig. 3.13) (Gioncu and Mazzolani, 2002).-

55、 Structural redundancy providing redistribution of forces can prevent collapse when individual members deteriorate during an earthquake. The complete failure of an element can be produced by local buckling or by fracture (in case of steel elements) or by crushing (in case of reinforced Learning from

56、 Earthquakes 85 Figure 3.10 Collapse of Hotel de Carlo due to pounding (NGDC, nd) Figure 3.11 Collapse of first level for pilotis structure during the Kocaeli earthquake (USGS, nd) 86 Earthquake Engineering for Structural DesignFigure 3.12 Failure of some connections during Kobe earthquake(Gioncu an

57、d Mazzolani, 2002)(a)Figure 3. 13 (continues)Learning from Earthquakes 87(b)Figure 3.13 Pino Suarez building: (a) Collapse due to lack of ductility(NGDC, nd); (b) Collapse of column (Gioncu and Mazzolani, 2002)concrete elements). As the post-buckling behavior can preserve some carrying capacity, it

58、is recommended to design the elements against the ultimate local fracture failure mode, especially when fracture or crush produces the overall failure of the element.- Plastic buckling produced in elements operates as a filter against large strains, reducing the danger of brittle fractures.- Unreinforced masonry buildings usually perform very poorly. Examining the failure modes of steel, reinforced concrete and masonry structures, it can be observed that