英文翻译-地基开挖对建筑物存在的潜在危害.doc

河北工程大学毕业设计(论文) 河北工程大学本科毕业设计 英语翻译译文题目：Evaluating Damage Potential in Buildings Affected by Excavations地基开挖对建筑物存在的潜在危害学生姓名： 专 业： 勘查技术与工程 班级学号： 指导老师： 2013年 05 月 15 日 Evaluating Damage Potential in Buildings Affected by ExcavationAbstract:Predicting building damage due to ground movements caused by excavations is an important design consideration when building in a congested urban environment. Current predictive approaches range from empiricalmethods to detailed finite element calculations. Limitations inherent in thesimpler of these models preclude them from accurately predicting damage incases where important assumptions are invalid. A new simple model forrepresenting buildings is presented to allow a designer to make realisticsimplifications to a building system that is consistent with major features of thestructure so that the response to ground movements can be adequately represented. This model assumes that the floors restrain bending deformations and the wall, whether load bearing or in-fill between columns, resist shear deformations. The proposed model is shown to adequately represent the response of a three-story framed structure which was affected by an adjacent deep excavation. The proposed model represents a reasonable compromise between overly simplistic empirical methods and complex, burdensome detailed analyses.Keywords: Excavation; Damage assessment; Soil-structuru; interaction; Building; Stiffness; Ground motion; Urban areas.Introduction Damage to buildings adjacent to excavations can be a major design consideration when facilities in congested urban areas. As new buildings are constructed, the excavations required for basements affect nearby existing buildings, especially those founded on shadow foundations. Often excavation support system design must prevent any damage to adjacent structure or balance the cost of a stiffer system with the cost of repairing damage to the affected structures. In either case, it is necessary to predict the level of ground movements that will induce damage to a structure. Practically speaking, a designer is attempting to limit/prevent damage to the architectural details of a building, which occurs prior to structural damage.A number of methods found in literature relate building damage to associated ground movements. Several of these methods are based on movements caused by settlements of a structure due to its owe weight, and do not consider the deformations that may occur as a result of a nearby excavation. Other methods do attempt to account for the additional modes of deformation,but are limited in their ability to adequately represent the affected structure. The purpose of this paper is to present a laminate beam method of evaluating potential building damage due to excavation-induced ground movements. This method avoids over- simplification common in current empirical methods, yet is not as computationally burdensome as a detailed finite element analysis. Published criteria applicable to excavation-induced building damage arereviewed and compared to the laminate beam method. In addition, assessments of damage potential as determined by both the existing and propose methods are compare to detailed records of damage to a three-story framed structure.Criteria to Evaluate Excavation-induced DamageSelected criteria that are applicable to evaluate excavation-induced damage are summarized in Table 1, where in the relevant parameter and its limiting value is shown. Note that the parameter used to relate structural movements at the foundation level to damage depends on the method. Deep beam methods are more general than empirical methods which were limited to damage of structure based on settlements arising from the weight of the structure.Tensile strain served as the limiting criterion for visible crack development when used with an elastic analysis of the building. They suggested that for sagging type deformations, the neutral axis is located at the middle of beam. For hogging type to deformations, the foundation and soil provide significan restraint to deformation.There are results also show that the limiting deflection ratio that causes cracks varies over wide limits, implying that structural details must be considered when establish criteria. However, it is difficult to provide guidance on the selection of the beam characteristic parameter EIG and the neutral axis location, especially when developing a deep beam model for a multistory structure.Boscardin and Cording (1989) extended this deep beam model to include horizontal extension strains#h, caused by lateral ground movements induced by adjacent excavation and tunneling activities. A chart relating 13ande to levels of damage was developed for building with brick, load-bearing walls, and an L/H ratio of I undergoing a hogging deformation with the neutral axis at the bottom. Direct transfer of horizontal ground strain to the structure is assumed in this approach. However, when the ground displaces laterally, relative slip will occur at the foundation level, and the horizontal displacement in the building will be less than that in the ground. Thus, this approach represents an upper bound of the effects of horizontal ground strain. Many modem buildings are ell-reinforced laterally by stiff floor systems, which essentially eliminate lateral movements at the foundation level in presence of lateral ground movements.Boone presented a more detailed approach to evaluate building damage due to differential ground movements caused by adjacent construction. This method considers structure geometry and design, strain superposition, and critical strains of building materials. Load bearing walls are modeled as uniformly loaded, simple-supported beams. Damage to frame buildings is assumed to occur from differential vertical movements of columns, depending on the columns tilt and degree of fixity. Damage to thrill walls is presumed to occur as a result of the deformed shape of the surrounding beams and columns. If a structure is subjected to horizontal extension, then these strains are superposes on the ones caused by bending and shear. Note that proper application of any of these methods requires an accurate prediction of the magnitude and distribution of ground movements adjacent to an excavation. Hsieh and Ou (1998) developed a semi empirical method to predict the distribution of ground movements in a direction perpendicular to an excavation wall. While finite element methods also can be used to compute thedesired settlements, conventional plane strain analyses with commonly used constitutive models generally underpredict the settlements close to an excavation and overpredict them at larger distances. This results in an unconservative prediction of the proper distribution of ground surface settlements is only possible if a constitutive model that accounts for strain-dependent modulus is incorporated in the analysis. Furthermore, whilethese approaches consider distress perpendicular to a supported excavation,significant distortions may develop parallel to an excavation, and these should be considered as well. Proper evaluation of the expected deformations is an important step in any procedure used to estimate damage, but is beyond the scope of this paper.Proposed MethodFollowing the approach of Burland and (1975), criteria related to visible cracking will be developed herein. They modeled a building as a rectangular beam with unit thickness, implicitly assuming a constant value of I/Ao for the building.Modem buildings are often designed with floor and roof diaphragms to efficiently distribute shear due to lateral loading. These diaphragms are concrete slabs or other type of floor systems that are fairly inextensible in tension, and are often considered rigid for design purposes. The shear from lateral loads passes into the diaphragms, which transfer this shear to wails in different magnitudes depending on their in-plane stiffness. Even in buildings that are not specifically designed with floor and roof diaphragms, the large area of the floors provides a significant degree of restraint to in-plane deformations and thus to bending deformations. This is true for both framed structures and load-bearing wall structures provided there is some mode of shear transfer from the roof and floors to the walls.To account for these observations, a laminate beam is proposed to model the response of a building to imposed deformations. It is assumed here in that the floors offer restraint to bending deformations, and the wall, whether load bearing or infill between columns, offer restraint to shear deformations.Deviations from Simple Supported Beam AssumptionIn cases where the building settles under its own weight, the assumption of a simply supported beam is usually adequate. However, when excavation-induce settlements are considered, different shapes of the settlement profile may develop. In cases where the building is not very long, a simply supported beam is an adequate assumption. There will be a single mode of deformation in the building, the rigid body rotation will be equal to the slope supports can be assumed.Alternatively, if a building undergoes both sagging and hogging modes of deformation, the simply supported beam assumptions are invalid because such a model requires that the rigid body rotation be equal to the slope of each simply supported beam (i.e.,=m for each deformation mode). For this to be true there must be a discontinuity in the beam at the inflection point so that each portion acts independently as a simply supported beam. This generally is not the case, and the discrepancy results in additional shearing strains, add, equal to the slope minus the rigid body rotation (add =m-). The sign of add is important when considering where the additional shear strain is added to the shear strain due to the simply supported beam assumption .The absouolutevalue of add is emplopyed to find the maximum shear strain in the beam when assessing the possibility of cracks.In a case where the deformation affects only a small portion of a building,the building may act like a cantilever beam, especially if it has a diaphragm system. In this case Esq. (12)-(15) are not sufficient to describe the actions of the building. A cantilever load condition must be used in the complementary vertical deflections to cause cracking.Note that when the critical bending strain is exceeded, cracks may not occur in the floor or roof slabs since it was assumed that all bending is resisted by the roof and floor systems. Rather, this cracking may be manifested as vertical cracks at junctions with columns or out-of -plane walls because as the floors are extended, the walls will extend with them. Additional resistance provided by the walls at this stage will be negligible since it is assumed that the floors are much stiffer in the lateral direction than the walls. Also, the critical tensile strain to cause cracking in the floors usually is greater than that for infill walls. Furthermore, the connection of infill wails to the framing has little resistance to tension. When the bending strain reaches the critical value of this connection, gaps will develop between the walls and framing members causing cracks at these joints. Thus, critical tensile strain can be used to evaluate cracking in the floors and separation at the junction of walls and columns if the appropriate critical strain is used. Note that vertical cracks at columns can also be caused by shear deformation, and thus should not be assumed to be caused solely by bending deformations.SummaryThe following procedure to evaluate damage potential in buildings affected by ground movements resulting from deep excavations, applicable to horizontally stiff or other structures wherein lateral ground movements induced by excavations do not induce lateral movements in the building, can be summarized as:1.Predict a distribution of ground movements.2.Locate the affected structure in relation to the expected ground movements. If needed, divide the settlement profile at each wall line to be analyzed into sagging and hogging zones at inflection, tangent and end of structure points.3.Compare the slope for each mode of deformation.4.Estimate the rigid body rotation of the section being analyzed. For many practical cases, one can use slope of the entire building from one extreme end to the other.5.Define the geometry and stmctural properties of the pertinent section of the building. See Notation for a summary of the required parameters.6.Compute the additional shearing strain in each mode of deformation by using add=-.7.Choose appropriate critical strain values for a given material and assumedfailure mode these methods. This procedure can be used in the design stage of supported excavation when the stiffness of the support system is selected to limit the expected ground movements to levels that will either prevent or minimize damage to an adjacent structure.地基开挖对建筑物存在的潜在危害摘要：在拥挤的都市环境中建筑的时候，考虑预测因开挖导致建筑物位移引起的损害的设计，引起工程界广泛关注现在预测性的方法有从经验的方法到详细的有限元素数列计算。限制在这些比较简单模型中，预先排除固有的在工程中正确预测灾害的重要假设是不合理的为表现这种情况建立一个新的建筑物模型，它允许设计者现实地简化建筑物系统，由完全表现感应地面位移的大多数结构特征组成的。这种模型假设地板抑制弯曲毁坏和承重或空间之间墙抵抗剪切破坏。被提议的模型充分地表现三维框架结构被一个毗连的深挖掘影响了的结构回应。这种假定模型表现了单一化的经验方法与复杂详细分析的方法之间的一个合理的妥协。关键词：挖掘；危害评估；土壤-结构的交互作用；建筑物；峰硬；地面运动；都市区 域说明 工程在拥挤的都市区域内，危害毗临建筑物的开挖设计引起关注。拟建建筑物的开挖需以对临近现有建筑物的影响为依据，尤其那些在隐蔽基础上的建筑物。成功的挖掘支持系统设计是尽量避免对毗连的结构任何的伤害或很好协调工程费用与用于修理被影响的结构伤害的费用之问的平衡。在任一将会诱发对结构的危害情况下，预测地面位移的程度是必要的。实际地说，一个设计者应尝试限制或避免对建筑物在结构发生损害之前的建筑细节的伤害。 在文献中发现大量有关建筑破坏与地面位移关系的事例一些方法以因建筑物自重引起结构变形产生的位移为依据，而不考虑一个附近工程开挖结果引发毁坏的可能其他的方法尝试阐明其它毁坏形式，但完全被限制在表述结构影响这一方面这一论文的目的是展现评估潜在的基坑开挖诱发地面位移引起的建筑物破坏的薄板状光线方法。这种方法避免在现在经验方法中过分单一化的情形，然而不像一项详细的有限元素分析计算那样繁琐现行标准适用于总结开挖诱因的建筑物损害和相较薄板状的光线方法。除此之外，潜在危害的评估决定于那些现有的和计划对详细记录的三层框架结构损害方法的比较。评估挖掘导致破坏的标准 选择适用评估挖掘损害的诱因被很多资料概述，并显示有关的参数和它的极限值。记录参数在基础水平相关结构位移的损害依赖这种方法。深的基线方法比被限制在以结构自重引起基础回弹导致结构损害的经验方法通用同建筑物的弹性分析共同应用时，引起可见的发展裂缝的拉应力作为限制标准他们建议下陷类型的毁坏，中轴位于基线的中央。隆起类型的毁坏，基础和土壤提供重要的毁坏抑制。 有结果显示各种超过极限宽的裂缝引起的变形比，暗示当为建立标准时要考虑结构细节。然而r它难以为基线特性参数EG和中轴位置的选择提供指导，尤其为发展的多层结构深基线模型。 搏斯卡丁和鳄丁(1989)拓展了这个深基线模型包括水平拉张应力， h，毗连挖掘和隧道工程导致的地面的水平位移。损害水平上图解和e h的关联被为以砖块负荷的墙壁，和遭受建筑底部中轴线上的隆起毁坏l的LH比所发展这种方法假设直接传送水平地面应力到结构。然而，当地面水平平行移动，相对滑动将会在基础水平发生。建筑水平的移置将低于地面的移置。因此，这方式表现水平地面应力对上边界的效果。许多现代的建筑物是很好地被钢筋地板系统水平加强，在侧面的地面之前本质上在基础水平消除侧面的运动。 呈现了比较详细评估由毗连建筑产生差异的地面位移所引起建筑物损害的方式。这一个方法考虑几何结构、设计、应力分布和建筑材料的标准应力。负荷墙壁当做统一的装载和简单的支撑基线的模型。框架建筑物的破坏假设因垂直体积差异移动产生，依赖体积的倾斜和固定的程度内置墙壁的损害被假定因周围基线和体积形状破坏结果发生如果结构受制于水平线延长，这些应力被施予一个藉由弯曲和剪切形成的整体。 注意合理应用这些方法中任何一种都需要准确预测毗连开挖地面位移的分配Hsieh和Ou(1998)发展了一个半经验的方法预测对挖掘面一侧墙壁在垂直方向上地面运动的分配。有限的元素方法也能用来计算满足要求的移位，不过