土木工程毕业论文工程设计框架结构(十)

第十四章 外文翻译

英文摘要:

Footings

The purpose of the structural portion of every building is to transmit applied loads safely from one part of the structure to another.The loads pass from their point of application into the superstructure,then to the foundation,and then into the underlying supporting material. We have discussed the superstructure and foundation walls to some extent. The foundation is generally considered to be the entire lowermost supporting part of the structure. Nomally,a footing is the last ,or nearly the last,structural element of the foundation through which the loads pass. A footing has as its function the requirement of speading out the superimposed load so as not to exceed the safe capacity of the underlying material, usually soil, to which it delivers the load. Additionally, the design of footings must take into account certain practical and ,at times,legal considerations.

The more common types of footing may be categorized as follows:

1. Individual column footings are often termed isolated spread footings and are generally

square. If space limitations exist ,however , the footing may be rectangular in shape. 2.

3. Wall footing support walls that may be either bearing or nonbearing walls. Combined footings support two or more columns and may be either rectangular or

trapezoidal in shape . If two isolated footings are joined by a strap beam ,the footing is sometimes called a cantilever footing.

4. Mat foundations are large continuous footings that support all columns and walls of a

structure. They are commonly used where undesirable soil conditions prevail.

5. Pile caps or pile footings serve to transmit column loads to a group of piles,which will

in turn transmit the loads to the supporting soil through friction or to underlying rock in bearing.

An individual reinforced concrete footing for a column ,also termed an isolated spread footing ,is probably the most common,simplest,and most economical of the various types of footings used for structures. Individual column footings are generally square in plan , Rectangular shapes are sometimes used where dimensional limitation exist,however.The footing is a slab that directly supports a column . At times, a pedestal is placed between a column and a footing so that the base of the column need not be set below grade.

The footing behavior under concentric load is that of two-way cantilever action extending out from the column or pedestal. The footing is loaded in an upward direction by the soil pressure. Tensile stresses are induced in each direction in the bittom of the footing. Therefore , the footing is reinforced by two layers of steel perpendicular to each other and parallel to the edges. The required footing-soil contact area ia a function of , and determined by ,the allowable soil bearing

pressure and column loads being applied to the footing .

In isolated square footings ,the reinforcement should be uniformly distributed over the width of the footing in each derection . Since the bending monent is the same in each direction , the reinforcing bar size and spacing should be the same in each direction . In reality ,the effective depth is not the same in both derections. It is common practice to use the same average effective depth for design computation for both directions ,however.

Rectangular footings are generally used where space limitation require it. The design of these footings is very similar to that of the square column footing with the one major exception that each direction must be investigated independently. Shear is checked for two-way action, it is checked across the shorter side only. The bending moment must be considered separately for each direction. Each direction will generally require a different area of steel. The reinforcing steel running in the long direction should be placed below the short-direction steel so that it may have the larger effective depth to carry the larger bending moments in that direction.

In rectangular footings, the distribution of the reinforcement is different than for square footings(ACI Code,section 15.4.4). The reinforcement in the long derection should be uniformly distributed over the shorter footing width. A part of the required reinforcement in the short direction is placed in a band equal to the length of the short side of the footing. The portion of the total required steel that should go into this band is 2/(β+1),where is the ratio of the long side of the footing.The remainder of the reinforcement is uniformly distributed in the outer portions of the footing. Other features of the design are similar to those for the square column footing.

Where footings are subject to eccentric vertical loads or to moments transmitted by the supported column, the design varies somewhat from that of the preceding sections.

The soil pressure is no longer uniform across the footing width but may be assumed to vary linearly. The resultant force should be within the middle one-third of the footing base to ensure a positive contact surface between the footing and the soil.

With the soil pressure distribution known, the footing must be designed to resist all moments and shears,as were the concentrically loaded footings.

Combined footings are footing that support more than one colummor wall. The two-column type of combined footing,which is relatively common,generally results out of necessity. Two conditions that may lead to its use are (1) An exterior column that is immediately adjacent to a property line where it is impossible to use an individual column footing and (2) two columns that are closely spaced, causing their individual footings to be closely spaced. In these situlations, a rectangular or trapezoidal combined footing would usually be used. The choise of which shape to use is based on the difference in column loads as well as on physical (dimensinal) limitations. If the footing cannot be rectangular,a trapezoidal shape would then be selected.

The physical dimensions (except thickness) of the combined footing are generally established by the allowable soil pressure. In addion,the centroid of the footing erea should coincide with the line of the resultant of the two column loads.these dimensions are usually determined using service loads in combination with an allowable soil pressure.

外文翻译:

基础工程

对于每一幢建筑物来说，它的任何一部分结构的用途都是将外加荷载安全地从结构的一部分传递到另一部分。荷载施加到上部结构，接着传到基础，最后传递到基础下面的支撑材料。我们已经在某种程度上讨论过了上部结构和条形基础。基础一般被认为是整个结构的最低支撑部分。一般地，基础是荷载通过的最后或接近最后的结构部分。基础的职能是把叠加荷载按要求分散并传递给支撑材料，这样才不至于超过支撑材料（一般是土壤）的安全能力。此外，设计地基，必须考虑一些实际的，有时法律上的考虑.

主要的基础类型概括如下：

1. 独立柱基础经常被叫做孤立扩展基础，一般都是方形的。如果受空间限制的话，可

把它作成矩形。

2.

3. 条形基础支撑承重墙或非承重墙。 联合基础支撑两根或两根以上柱子，可以作成矩形或梯形。如果两个独立基础被一

根基础梁连在一起，这种基础有时会被叫做悬臂基础。

4. 箱形基础是很大的连续基础，它支撑着整个结构的所有柱子和墙体。这种基础一般

用于土壤条件普遍不理想的情况下。

5. 柱基础用于传递柱的荷载给一组桩，这组桩再把荷载传递给支撑它的土壤或岩石。 有些钢筋混凝土柱基础，也叫独立放脚基础，很可能是所有结构基础类型中最普遍、最简单、最经济的。独立柱基础一般设计成方形。矩形的独立柱基础有时用于空间受限情况。基础是一个直接支撑柱的平板。有时底座被置于柱和基础之间，这种柱的底部就不必置于水平以下。

集中荷载下的基础行为类于双向的悬臂梁，从柱脚开始延伸。基础承受土壤向上传来的压力。基础的底部承受来自各个方向的张力。因此，基础被用两层相互正交的钢筋平行直至边缘加强。基础和土壤的最小接触面积由土壤所能承受的最大压力和柱子传递给基础的压力决定。

在独立的方形基础，加强在基础宽度各个方向的分发都应该一致。因为弯曲时刻在各个方向上都是一致的，所以加强筋的型号和间距在各个方向上也应该一致。事实上，在任意两个方向上的有效厚度不是完全一样的。

矩形基础一般用于空间狭小的情况。这类基础的设计和方形基础非常相似，它们的共同点是一个主方向受力除外，其余各方向都必须独立地调查。一般情况下，剪力是从两个方向上进行检验，而不是一个方向，仅从短的一边检查。弯曲时刻必需每个方向都独立考虑。一般地不同的方向需要不同型号的钢筋。长方向浇筑的钢筋应该放置在短方向钢筋的下面，这样它在这个方向承受更大弯曲时刻就有更大的有效厚度。

在矩形基础中，加强筋的分配和方向基础不同。在长方向的加强筋应该同样分配到稍短的基础宽度。在短方向要求的加强筋的一部分被作成箍，箍的长度就是基础小截面的周长。总需求钢筋的一部分应使用公式2/(β+1)计算箍，其中 β是基础长边的比率。

偏少受力基础承受偏心垂直荷载或由所支撑的柱传递过来的荷载，这种设计改变了优先发生的断裂的断面。土壤压力不再完全一致传递到基础宽度，而是假定发生线性改变。由结果

而产生的力应该在1/3基础的中心以确保在基础和土层之间有一个明确的接触面。

在已知土壤压力分配的作用，基础必须设计为抵抗所有时刻和剪力，因为它是中心荷载基础。

联合基础是支持两根以上柱或墙体的基础。联合基础的两根柱子类型是相对的、普遍的、一般的需求的结果。两条件可能导致：（1）它的用途是一根非常邻近边界线的外部柱，不能采用独立基础。（2）两根柱子的距离很近，使用联合基础。在这些情况下，矩形基础和方形基础常常被使用。选择使用矩形基础，还是梯形基础，是根据荷载的大小和空间限制。如果基础不能选用矩形，将只能使用梯形。

联合基础的尺寸（特薄的除外）一般由允许土壤压力确定。额外的，基础面积的形式应该和两个柱子荷载组合的作用线重合。这些尺寸一般应该决定于最大荷载和允许的土压力。 矩形和梯形联合基础的结构设计一般依据的土压力，即使这样荷载组合常常和基础质心产生一些偏心。基础厚度和钢筋的选择必须依据计算荷载和土压力，并和ACI强度计算方法一致。简要描述的假定基础上的受力是一个普遍采用的简化基础设计的方法。

参考文献

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⑼ 《建筑抗震设计规范》GB50011-2001

⑽ 《混凝土结构设计规范》GB50010－2002

⑾ 《建筑地基基础设计规范》GB50007－2002

⑿ 《建筑抗震设防分类标准》GB50223－95

⒀ 《建筑结构荷载规范》GB50009－2001

⒁ 《建筑设计防火规范》GBJ 16－87

⒂ 《民用建筑设计通则》GB50352－2005

⒃ 《钢筋混凝土高层建筑结构设计与施工工程》JGJ 3－91

⒄ 《民用建筑工程结构初步设计深度图样》05G104