为什么日本建筑物有那么强抗震能力

我的看法是，标准重力对偶性和几何跃迁是与QG和暴涨有关的最有前途的理论

这个问题可能有相当多的答案，因为有大量无法验证的、前瞻性的理论存在。我首先声明我的观点:我做过关于量规-重力对偶性的研究。而且，我和我的导师都坚信，只有将弦理论应用于AdS/CFT和膨胀理论，才能更好地理解量子引力(QG)。

让我们先搞清楚几件事。AdS/CFT猜想是量规-重力对偶性的一个例子(事实上它是第一个例子)。简化事情,Gauge-Gravity二元性是一个过程,一个能相关的强耦合指标引力理论(如钢管)弱耦合理论在广告。1998的证明这个猜想是由于Juan Maldacena和打开了一个巨大的研究领域对粒子的理论家和弦理论家。这个对应给我们的一个主要引证结果是夸克-胶子等离子体在RHIC的粘度的下界。

现在对应本身与量子引力没有太多关系，事实上很多粒子理论家的arXiv论文都尽量避免提到弦。然而，许多作者已经将AdS/CFT对应关系和测量-重力对偶性应用于诸如重力为最重要的膨胀等情况。事实证明，在双曲洛伦兹流形(例如AdS)和其他规范理论(包括量子色动力学或QCD)之间可以有其他对偶性。这些其他的对偶现象叫做几何跃迁。他们被称为这样，因为二元性产生于收缩“引力”时空和扩展“规范理论”时空，或者反之。如果你有物理学背景，我建议你阅读以下文章，由Kachru, Baumann和McAllister来理解暴涨如何与QG和AdS/CFT相关联。

CDT大量借用了晶格量子场理论。其基本思想是对所有可能的时空执行费曼路径积分，以生成“量子时空”。由于这条路径的积分通常很难定义，更不用说计算了，我们通过在计算机上随机生成对路径积分贡献最大的时空来计算路径积分的近似值，并希望我们选择的数字足够收敛。

我也很喜欢因果集，这是一种新的生态位理论。我喜欢它，因为它和以前的任何东西都非常不同。因果集完全抛弃了连续时空的概念，并假定宇宙是由许多离散点组成的。在事情的核心，这些点之间唯一的关系是因果关系。换句话说，我们知道点X在点Y的因果过去，但仅此而已。

通过Sing-Ping成员,Seng-Tjhen,中国土木水利工程学刊,第1、2、Chao-Wei Dai3撒谎

文摘:本文针对目前的研究对钢管混凝土抗I-beam钢柱uniplanar管(钢管连接静力荷载作用下的单调。复合材料的连接可以加筋或unstiffened。经验公式推导出基于>数值参数分析结果100。研究的关键参数的数值计算有限元方法,有关影响时刻——物质被俘在国内外的提议配方。检验经验公式和清楚的静态性能的综合连接,8个标本进行设计和测试失败,其中4个标本进行了抗震设计和其他设备连接着不同种类的刚性节点僵硬的细节。对比试验结果表明,预测和经验公式可以用于预测时刻阻力。在试验的基础上,提出了钢筋加劲肋被发现是非常有效的提高了静态性能的综合连接。

介绍

在建筑施工行业、钢管混凝土管(工程)栏目都欢迎世界各地。相比传统的钢材和混凝土西- umns、钢管混凝土柱具有许多优点,如钢管提供监禁和模板具体的核心,刚度和稳定性,改进了钢管混凝土的原因是——填充柱,降低成本,强制欺诈。然而,由于缺乏设计性能和复杂性的guid -连接到这样的栏目(如图),使用。对钢管混凝土柱是有限的。

最近,由于实际教学的要求,一些研究工作,进行了相关的领域——nections欺诈。森野等。(1993)进行三维模拟地震下10加载模块。所有标本的钢管混凝土柱和4平方公里,H-shaped中空截面梁焊接。彩等。(1995)研究对钢管混凝土柱连接I-beam筋与外部的戒指或额外的圆管与锚。施奈德和Alostaz(1998)试验对不同六个大硬- ing的细节。试验结果表明,扩展梁- nection-stub欺诈响彻了整个钢管混凝土柱是足够的发展完整的塑料弯曲强度、塑性连接梁循环性能良好。卢(1997)测试对钢管混凝土柱螺栓连接I-beam与复合地板在一个平面弯曲。得出了相当大的增加混凝土充填在连接强度。然而,测试的结果

K.A.S. Susantha, Hanbin Ge, Tsutomu Usami *

Department of Civil Engineering, Nagoya University, Chikusa-ku, Nagoya 464-8603, Japan

Received 31 May 2000received in revised form 19 December 2000accepted 14 February 2001

Abstract

A method is presented to predict the complete stress–strain curve of concrete subjected to triaxial compressive stresses caused by axial load plus lateral pressure due to the confinement action in circular, box and octagonal shaped concrete-filled steel tubes. Available empirical formulas are adopted to determine the lateral pressure exerted on concrete in circular concrete-filled steel columns. To evaluate the lateral pressure exerted on the concrete in box and octagonal shaped columns, FEM analysis is adopted with the help of a concrete–steel interaction model. Subsequently, an extensive parametric study is conducted to propose an empirical

equation for the maximum average lateral pressure, which depends on the material and geometric properties of the columns. Lateral pressure so calculated is correlated to confined concrete strength through a well known empirical formula. For determination of the post-peak stress–strain relation, available experimental results are used. Based on the test results, approximated expressions to predict the slope of the descending branch and the strain at sustained concrete strength are derived for the confined concrete in columns having each type of sectional shapes. The predicted concrete strength and post-peak behavior are found to exhibit good

agreement with the test results within the accepted limits. The proposed model is intended to be used in fiber analysis involving beam–column elements in order to establish an ultimate state prediction criterion for concrete-filled steel columns designed as earthquake resisting structures. •2001 Elsevier Science Ltd. All rights reserved.

Keywords: Concrete-filled tubesConfinementConcrete strengthDuctilityStress–strain relationFiber analysis

1. Introduction

Concrete-filled steel tubes (CFT) are becoming increasingly popular in recent decades due to their excellent earthquake resisting characteristics such as high ductility and improved strength. As a result, numerous experimental investigations have been carried out in recent years to examine the overall performance of CFT columns [1–11]. Although the behavior of CFT columns has been extensively examined, the concrete core confinement is not yet well understood. Many of the previous research works have been mainly focused on investigating the performance of CFT columns with various limitations. The main variables subjected to such limitations were the concrete strength, plate width-to- thickness (or radius-to-thickness) ratios and shapes of the sections. Steel strength, column slenderness ratio and rate of loading were also additionally considered. It is understandable that examination of the effects of all the above factors on performances of CFTs in a wider range, exclusively on experimental manner, is difficult and costly. This can be overcome by following a suitable numerical theoretical approach which is capable of handling many experimentally unmanageable situations. At present, finite element analysis (FEM) is considered as the most powerful and accurate tool to simulate the actual behavior of structures. The accurate constitutive relationships for materials are essential for reliable results when such analysis procedures are involved. For example, CFT behavior may well be investigated through a suitable FEM analysis procedure, provided that appropriate steel and concrete material models are available. One of the simplest yet powerful techniques for the examination of CFTs is fiber analysis. In this procedure the cross section is discretized into many small regions where a uniaxial constitutive relationship of either concrete or steel is assigned. This type of analysis can be employed to predict the load–displacement relationships of CFT columns designed as earthquake resisting structures. The accuracy involved with the fiber analysis is found to be quite satisfactory with respect to the practical design purposes.

At present, an accurate stress–strain relationship for steel, which is readily applicable in the fiber analysis, is currently available [12]. However, in the case of concrete, only a few models that are suited for such analysis can be found [3,8,9]. Among them, in Tomii and Sakino’s model [3], which is applicable to square shaped columns, the strength improvement due to confinement has been neglected. Tang et al. [8] developed a model for circular tubes by taking into account the effect of geometry and material properties on strength enhancement as well as the post-peak behavior. Watanabe et al. [9] conducted model tests to determine a stress–strain relationship for confined concrete and subsequently proposed a method to analyze the ultimate behavior of concrete-filled box columns considering local buckling of component plates and initial imperfections. Among the other recent investigations, the work done by Schneider [10] investigated the effect of steel tube shape and wall thickness on the ultimate strength of the composite columns. El-Tawil and Deierlein [11] reviewed and evaluated the concrete encased composite design provisions of the American Concrete Institute Code (ACI 318) [13], the AISC-LRFD Specifications [14] and the AISC Seismic Provisions [15], based on fiber section analyses considering the inelastic behavior of steel and concrete.

In this study, an analytical approach based on the existing experimental results is attempted to determine a complete uniaxial stress–strain law for confined concrete in relatively thick-walled CFT columns. The primary objective of the proposed stress–strain model is its application in fiber analysis to investigate the inelastic behavior of CFT columns in compression or combined compression and bending. Such analyses are useful in establishing rational strength and ductility prediction procedures of seismic resisting structures. Three types of sectional shapes such as circular, box and octagonal are considered. A concrete–steel interaction model is employed to estimate the lateral pressure on concrete. Then, the maximum lateral pressure is correlated to the strength of confined concrete through an empirical formula. A method based on the results of fiber analysis using assumed concrete models is adopted to calibrate the post-peak behavior of the proposed model. Finally, the complete axial load–average axial strain curves obtained through the fiber analysis using the newly proposed material model are compared with the test results. It should be noted that a similar type of interaction model as used in this study has been adopted by Nishiyama et al. [16], which has been combined with a so called peak load condition line in order to determine the maximum lateral pressure on reinforced concrete columns.

Meanwhile, previous researches [17,18] indicate that the stress–strain relationship of concrete under compressive load histories produces an envelope curve identical to the stress–strain curve obtained under monotonic loading. Therefore, in further studies, the proposed confined uniaxial stress–strain law can be extended to a cyclic stress–strain relationship of confined concrete by including a suitable unloading/reloading stress–strain rule.

2. Theoretical background

2.1. Characteristic points on confined concrete stress–strain curve

Referring to Fig. 1（General stress–strain curves for confined and unconfined concrete.）, the following characteristic points have been identified to define a complete stress–strain curve when concrete is confined by surrounding steel tubes. The notation in the figure is as follows: f ’c is the strength of unconfined concretef ’cc is the strength of confined concreteεc is the strain at the peak of unconfined concreteεcc is the strain at the peak of confined concreteεu is the ultimate strain of unconfined concretefu is the ultimate strength of unconfined concreteεcu is the ultimate strain of confined concreteand αf ’cc is the residual strength of confined concrete at very high strain levels. The expression for the complete stress–strain curve is defined as suggested by Popovics [19], which was later modified by Mander et al. [20] and given by where fc and ε denote the longitudinal compressive stress and strain, respectivelyEc stands for the tangent modulus of elasticity of concrete. It should be noted that Eq. (1) has been defined even for the post-peak region, in this study, it is utilized only up to the peak point. The post-peak behavior is treated separately by assuming a linearly varied stress–strain relation as will be discussed in Section 4.【1-4 Fig. 1】

2.2. Confinement action in circular CFT columns

In short CFT columns with relatively thick-walled sections designed for seismic purposes, failure is mainly caused due to concrete crushing. The mode of failure is governed by the individual behavior of each component. The behavior of concrete in CFT columns under monotonically increasing axial load can be explained in terms of concrete–steel interaction. The confinement effect does not exist at the early stage of loading owing to the fact that the Poisson ratio of concrete is lower than that of steel at the initial loading stage. At this level of loading, the circumferential steel hoop stresses are in compression and the concrete is under lateral tension provided that no separation between concrete and steel occurs (i.e., the bond between two materials does not break). However, as the axial load increases, the lateral expansion of concrete gradually becomes greater than the steel due to the change of the Poisson ratio of concrete, and therefore a radial pressure develops at the concrete– steel interface. At this stage, confinement of the concrete core is achieved and the steel is in hoop tension.

Load transferring from the steel tube to the concrete occurs at this stage. It is observed that the load at this stage is higher than the sum of loads that can be achieved by steel and concrete acting independently.

In the triaxial stress state the uniaxial compressive concrete strength can be given by 【5】 where frp is the maximum radial pressure on concrete and m is an empirical coefficient. In the past a lot of extensive experimental studies have been carried out to determine a value for coefficient m and it is found that for normal strength concrete, m is in the range of 4–6 [21]. In this study m is assumed to be 4.0. The radial pressure, fr, can be expressed by the relationship given in Eq. (6), which is easily derived by considering the equilibrium of horizontal forces on a circular section: 【6】

Here, fsr, t and D denote the circumference stress in steel, the thickness and the outer diameter of the tube, respectively.

3. Evaluation of confinement in various shaped CFT columns

3.1. Circular section

Determination of the confinement level in circular tubes is found in the method proposed by Tang et al. [8]. In this method, the change of the Poisson ratio of concrete and steel with column loading is investigated. An empirical factor, β, is introduced for this purpose and subsequently the lateral pressure at the peak load is given by 【7】 Factor β is defined as 【8】 where νe and νs are the Poisson ratios of a steel tube with and without filled-in concrete, respectively. Here, νs is taken as equal to 0.50 at the maximum strength point, and νe is given by the following expressions: 【9 10】 Here, t, D and f ’c are the same as previously defined and fy stands for the yield stress of steel. The above equation is applicable for (f ’c/fy) ranging from 0.04 to 0.20 where most of the practically feasible columns are found within. A detailed description of the method can be found in Tang et al. [8]. It is clear that frp given by Eq. (7) depends on both the material properties and the geometry of the column. Subsequently, frp calculated from Eq. (7) is substituted into Eq. (5) to determine the confined concrete strength, f ’cc.

摘要部分的翻译：

各种断面形状钢管混凝土的单轴应力应变关系

K.A.S. Susantha ， Hanbin Ge, Tsutomu Usami*

土木工程学院，名古屋大学, Chikusa-ku ，名古屋 464-8603, 日本

收讫于2000年5月31日 正式校定于2000年12月19日被认可于2001年2月14日

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摘要

一种预测受三轴压应力混凝土的完全应力-应变曲线的方法被提出，这种三轴压应力是由环形、箱形和八角形的钢管混凝土中的限制作用导致的轴向荷载加测向压力所产生的。有效的经验公式被用来确定施加于环形钢管混凝土柱内混凝土的侧向压力。FEM（有限元）分析法和混凝土-钢箍交互作用模型已被用来估计施加于箱形和八角形柱的混凝土侧向压力。接着，进行了广泛的参数研究，旨在提出一个经验公式，确定不同的筒材料和结构特性下的最大平均侧向压力。如此计算出的侧向压力通过一个著名经验公式确定出侧向受限混凝土强度。对于高峰之后的应力-应变关系的确定，使用了有效的试验结果。基于这些测试结果，和近似表达式来推算下降段的斜度和各种断面形状的筒内侧向受限混凝土在确认的混凝土强度下的应变。推算出的混凝土强度和后峰值性能在允许的界限内与测试结果吻合得非常好。所提出的模型可用于包括梁柱构件在内的纤维分析，以确定抗震结构设计中混凝土填充钢柱筒的极限状态的推算标准。 •版权所有2001 Elsevier科学技术有限公司。

关键词: 钢管混凝土；限制；混凝土强度；延性；应力应变关系；纤维分析

这是当年毕业时我的翻译，因为原文有图表等原文也超过10000字，没法在这里发，如需要原文（pdf版及word版）及全部翻译（5000字，中文），请留下邮箱。

字典上的答案是，保角场理论是在保角变换下不变的理论。

你早就知道了。

什么是保角变换？这些是欧几里得空间中的“保角”变换。在伪欧几里得时空中，事情会变得有点混乱，但本质是一样的：正形变换是一种不影响角度和速度(时空角度)的变换。否则，任何事情都可能发生。

在四维时空中，保形变换群的一个特定子集是(洛伦兹-)庞加莱群，它由平移、旋转和加速(速度变化)组成。洛伦兹群是没有翻译的庞加莱群。

或者反过来，你可以从空间旋转开始；如果你加一些刺激，你得到洛伦兹组；如果你添加(时空)翻译，你得到庞加莱组；如果你用扩张来扩展它和所谓的特殊保形变换(一个反转，接着一个平移，接着另一个反转)，你就得到了完全保形群。在3+1维中，空间旋转由3个参数表征；洛伦兹集团，6庞加莱集团，减10完全保形群，15。

相对论的一个基本假设是所有的物理在庞加莱变换下都是不变的。也就是说，无论观察者在哪里(平移)，他面对的方向(旋转)或他移动的速度(加速)都没有关系：物理看起来是一样的。这一理论部分是由实验证实的事实所驱动的，即电磁定律不会因位置、方向或速度而改变。

现在恰好电动力学，至少在没有电荷的情况下，在完全保角变换群下也是不变的。所以真空电动力学(四维空间)是保形场理论的一个例子。

保角理论也是尺度不变的：把某物变大或变小肯定会保留所有角度，这是很明显的。这也告诉你一个理论必须是尺度不变的才能保角。(3+1维保形群的保尺度子集是庞加莱群。)

量子电动力学在电荷存在时不是尺度不变的，因为它的耦合常数在高能时发生变化。所以就我们所知，我们在自然界中发现的量子场并不是用保角场理论来描述的。

尽管如此，保形理论让很多人兴奋的话题(虽然有些人对此表示怀疑),部分原因是著名的广告/钢管对应：这个猜想的预测正形(量子场论)对应于在一个高维引力理论的预测“反德西特空间”(本质上，时空负宇宙常数)。