1、混凝土结构直接破坏控制设计 摘要：已发展了的混凝土结构设计的基本方法到目前为止不管是在局部地方还是世界水平范围内都还不能直接控制破坏。为了形成一个综合的方案以便在设计期间对直接破损进行控制并且在实际中对其应用性进行研究，一个名为直接破损控制设计的设计观点被提了出来。尽管提出的这个设计观点只是一个概括，但是本文将重点集中于在静载荷作用下梁，它由素混凝土或者其他的准脆性材料，比如砌块，水泥等组成。这个提出的方法适当的结合了基于规范的应立应变关系 .五种特有的数字实例被提出，以次来解说被提出的方法论并且说明对于结构 设计的直接适用性 . CE 数据库主题标题：破坏，混凝土结构，设计，梁柱，有限元方法
2、 介绍 结构的破坏是被定义为一种降级的程度 .这种降级使得结构抵抗进一步荷载的能力的判断可以进行 .它通常被结构 所量化 .这种 代表着实际的破坏 ,并且这种实际的破坏是被结构破坏的数值标准化过了的 .一个破坏参数值为零意味着没有破坏发生 (纯弹性行为 ),与之相反当一个参数值为一则说明结构强度的完全丧失 .严格地说 ,当研究的范围是一个单一的点时破坏指数被定义为局部 ,当研究的范围是某一个片段、某一个构件、某一部分结构或者是整一个结构，那么破 坏指数就被定义为整体 .然而 ,如果局部破坏也可以用来描述在一个片段 ,构件或者结构中的破坏状态时 ,在设计的过程中以上的这些术语应该被清楚的定义 .
3、 为了满足安全的要求 ,出现了三种不同的设计理论 ,从而推倒出了以下的设计方法 . 1. 工作应力方法 (WSM):工作应力法或者是允许应力法是以上这些设计方法中最老的也是最简便的方法 ,在传统上受到许多的结构工程师的青睐 .根据这个方法 ,结构和构件设计出来是用于提供荷载 ,而构件面积的选择是在应力不超过某一特殊的允许应力值的方式下确定的 .这个特殊的允许应力值往往是在弹性范围以内的 .在设计阶段的末尾要对结构耐用性的要求进行复核 . 2. 最终应力法 (USM):在新的钢筋混凝土规范当中采用了 USM理论或者是基于外力基础上的方法 .在概率方法的基础上 ,USM 法最重要的目的就是决定极限
4、状态下的荷载 (即导致结构失效的荷载 ).值得注意的是 USM 法考虑了弹性和非弹性范围内材料的性能以及构件的工作状态 .因此 ,在设计当中力起了决定性的作用 .在临近设计的末尾为了耐用性的要求需要对试件的位移进行检查 . 3. 基于构件挠度的方法 (DBM):DBM 法在结构工程中是一个新的很有发展前景的方法 ,在抗震结构设计当中 ,此 法被许多的研究人员所采用 .这种方法的基本思路是设计一个结构直接来满足关于挠度的某种极限 .例如在地震当中某一个多层的建筑中连续两个楼层间的相对水平位移或者是层间飘移 .由于对于位移有这种限制，使得构件必须要有一定的刚度并且在结构中产生相应的三唯空间的内力值
5、 .因此 ,位移在这里起了决定的作用 .与 USM 法比较 ,后者力的因素起了决定的作用 . 结论 : 以上述的发展作为基础 ,我们能够得出以下的结论 : 1. 直接控制破坏法 (DDCM)这个新的结构设计方法在本文已经被提出 .这个方法较任何一个现存的结构设计方法来说可以更好的以一 种直接的明确的的方式确定和控制破坏的数量 . 2. 这里所介绍的方法是被应用于由混凝土或者石料组成的承受静力荷载的梁结构 .这些静力荷载在构件当中会引起轴力和弯矩等的内力组合 . 3. 应用这个方法 ,在计算机软件和设计图表的辅助之下设计者可以对一个已知截面形状与荷载的构件确定其破坏程度 .或是已知最终的破坏水平
6、以及荷载确定截面的大小 .或是已知构件和最终破坏水平来确定最大荷载值 . Direct Damage-Controlled Design of Concrete Structures George D. Hatzigeorgiou1 and Dimitri E. Beskos, F.ASCE2 Abstract: The basic methods of structural concrete design that have been developed so far cannot directly control damage, either at the local or the glo
7、bal level. In order to develop an integrated scheme for direct damage control during design and study its application in practice, a new design philosophy, named direct damage controlled design, is proposed. In spite of the generality of the presented design philosophy, this paper focuses on the bea
8、m type of structures composed of plain concrete or other quasi-brittle materials, such as masonry or ceramics, and subjected to statically applied loading. The proposed methodology appropriately combines code-based stress-strain relations with a simple expression for damage to determine with the aid
9、 of the fiber model and the finite-element method axial force and bending moments of a beam-column element as functions of deformation and/or damage. Five haracteristic numerical examples are presented to illustrate the proposed methodology and demonstrate its direct applicability to structural desi
10、gn CE Database subject headings: Damage； Concrete structures； Design； Beam columns； Finite element method. Introduction Structural damage is defined as the level of degradation that allows a decision to be reached about the capacity of a structure to resist further loading. It is usually quantified
11、through damage indices that represent actual damage normalized by its value at structural failure. A value of the damage index equal to zero (0)means that there is no damage (pure elastic behavior), while a value of one (1) reflects complete loss of strength. Strictly speaking, a damage index is ter
12、med local when it refers to a single point and global when it refers to a section, a member, a structural part, or an entire structure. However, the above terms must be clearly defined in a design procedure since local damage can also be used to describe the state of damage in a section, member, or
13、structural part. In order to satisfy safety requirements, three different design philosophies have been developed to date leading to the following design methods: 1. The working stress method _WSM_: The WSM or allowable stress method is the oldest and simplest of the above design methods and has tra
14、ditionally enjoyed a great popularity among structural engineers. According to this method, the structure and its elements are designed for service loads and are dimensioned in such a way that stresses do not exceed some specific allowable stress values _strengths_, which are always in the elastic r
15、ange. Serviceability requirements are checked at the end of the design process. 2. The ultimate strength method _USM_: The philosophy of the USM or force-based method has been adopted by all modern steel and concrete codes. The most important goal of the USM is the determination of the limit state l
16、oad, that is, the load that leads to failure, on the basis of a probabilistic approach. It is worth noticing that the USM takes into account both the elastic and inelastic range of the material behavior and member performance. Thus, forces here play the fundamental role in design, and displacements
17、are checked for serviceability near the end of the design process. 3. The displacement-based method _DBM_: The DBM of design is a promising new method in structural engineering that has been adopted by many researchers, mainly in the design of earthquake-resistant structures. The basic idea of this method is to design a structure that satisfies
