外文原文出处：

Geotechnical, Geological, and Earthquake Engineering, 1, Volume 10, Seismic Risk Assessment and Retrofitting, Pages 329-342

补充垂直支撑对建筑物抗震加固

摘要：大量的钢筋混凝土建筑物在整个世界地震活跃地区有共同的缺陷。弱柱，在一个或多个事故中，由于横向变形而失去垂直承载力。这篇文章提出一个策略关于补充安装垂直支撑来防止房子的倒塌。这个策略是使用在一个风险的角度上来研究最近实际可行的性能。混凝土柱、动力失稳的影响、多样循环冗余的影响降低了建筑系统和组件的强度。比如用建筑物来说明这个策略的可行性。

1、背景的介绍：

建筑受地震震动，有可能达到一定程度上的动力失稳，因为从理论上说侧面上有无限的位移。许多建筑物，然而，在较低的震动强度下就失去竖向荷载的支撑，这就是横向力不稳定的原因(见图16.1)。提出了这策略的目的是为了确定建筑物很可能马上在竖向荷载作用下而倒塌，通过补充一些垂直支撑来提高建筑物的安全。维护竖向荷载支撑的能力，来改变水平力稳定临界失稳的机理，重视可能出现微小的侧向位移(见图16.2)。

在过去的经验表明，世界各地的地震最容易受到破坏的是一些无筋的混凝土框架结构建筑物。这经常是由于一些无关紧要的漏洞，引起的全部或一大块地方发生破坏，比如整根梁、柱子和板。去填实上表面来抑制框架的内力，易受影响的底层去吸收大部分的内力和冲力。

这有几种过去被用过的方法可供选择来实施:

1、加密上层结构，可以拆卸和更换一些硬度不够强的材料。

2、加密上层结构，可以隔离一些安装接头上的裂缝，从而阻止对框架结构的影响。

3、底楼，或者地板，可以增加结构新墙。这些措施(项目1、2和3)能有效降低自重，这韧性能满足于一层或多层。然而，所有这些都有困难和干扰。在美国，这些不寻常的代价换来的是超过一半更有价值的建筑。

4、在一些容易受到破坏的柱子裹上钢铁、混凝土、玻璃纤维、或碳纤维。

第四个选项可以增加柱子的强度和延性，这足以降低柱子受到破坏的风险在大多数的建筑物中。这个方案虽然成本比前面低，但是整体性能也会降低，对比较弱的地板破坏会更加集中。加强柱子的强度在美国很流行，但它的成本依旧是很高的。在发展中国家，这些先进的技术对某些种类的加料或加强，还不能够做到随心所欲。

这个程序的提出包含了另一个选择，美国已经运用这个选择用来降低房子倒塌的风险。这个方法是增加垂直支撑，来防止建筑在瞬间竖向荷载作用下就倒塌(见图16.3)。这是为支撑转移做准备的，当柱子被剪切破坏和剪切衰弱时。这个补充支撑通常是钢结构、管道支撑或木材支撑。他们通常安装在单独的柱子上，但(图16.3)钢柱也可以被放置在能承担的水平框架上。这种技术能有效的降低自重，从而降低了建筑在瞬间竖向荷载下就遭到破坏。在水平方向的强烈震动，产生的不稳定大概很少被想到。补充的安装垂直技撑相对比较便宜。一些有用的空间可能通过安装支撑被影响，可是这是一些微不足道的比较。在美国为建筑安装一些补充支撑现在非常流行。

Supplemental Vertical Support as a Means for Seismic Retrofit of Buildings

Craig D. Comartin

Geotechnical, Geological, and Earthquake Engineering, 1, Volume 10, Seismic Risk Assessment and Retrofitting, Pages 329-342

Abstract A large number of concrete buildings in seismically active areas throughout the world exhibit a common deficiency. Weak columns, in one or more stories, lose vertical load-carrying capacity as a result of lateral distortion. This chapter presents a conceptual strategy for retrofit comprising the installation of supplemental vertical supports to prevent collapse. This procedure utilizes a risk-based perspective based on recent research on the realistic capacity of concrete columns, dynamic instability, and the effects of in-cycle degradation of strength in building systems and components. An example building is used to illustrate the application of the concept.

1 Introduction and Background

Buildings subject to earthquake shaking have a potential to reach a point of dynamic instability at which they collapse due to theoretically unlimited lateral displacement.

Many buildings, however, lose the ability to support vertical loads and collapse at smaller levels of shaking intensity than that which would otherwise cause lateral dynamic instability (see Fig. 16.1). The procedures proposed here are intended

to identify buildings prone to preemptive vertical load collapse and improve their safety by the installation of supplemental vertical supports. Maintaining the capability to support vertical loads changes the critical collapse mechanism to lateral dynamic stability which occurs at larger and less probable lateral displacements (see Fig. 16.2).

Experience in past earthquakes around the world indicates that concrete frames infilled with unreinforced masonry (URM) have been particularly prone to collapse. This most often is due to a weak first story caused by the omission of all or a substantial portion of the infill to allow for retail, parking, or other uses conducive toopen spaces. The infill in upper stories restrains frame action and forces the flexible lower floor to absorb most of the energy demand and drift.

There are several alternatives for retrofit strategy that have been implemented in the past:

1. The infill on upper floors could be removed and replaced with less stiff and less strong materials.

2. The infill on upper floors could be isolated from the structure by installing joints with gaps to prevent interaction with the frame.

3. The lower floor, or floors, could be strengthened with new structural walls。These Measures (Items 1, 2, and 3) are effective in reducing the ductility demand in the weak story or stories. However, all of them are costly and intrusive. In the US, it is not unusual for the costs of these types of retrofit to exceed half of the replacement value of the building.

4. Wrap the columns in the weak story with jackets of steel, concrete, fiberglass, or carbon fiber.

The fourth option can increase both the strength and ductility of the columns enough to reduce the collapse risk for most buildings. The cost is somewhat less than for the first three alternatives; however the overall performance would also be less with more damage focused in the weak floor. Column jacketing is popular in the US, but the costs can still be high. In developing countries, the advanced technologies for some types of jackets may not be readily available.

The procedure proposed here incorporates another alternative that has been used in the US to reduce collapse risk. This strategy is to provide supplemental vertical supports designed to prevent preemptive vertical load collapse (see Fig. 16.3). These are intended to support loads that are transferred from shear critical columns as they are damaged and begin to fail. The supplemental supports are typically steel shapes, pipe shoring, or timber shores. They are often installed near individual columns, but also can be placed beneath capable horizontal framing. This technique is effective in reducing collapse risk by avoiding the preemptive vertical collapse mode。The intensity of shaking required for lateral dynamic instability is generally higher and less likely to occur. The installation of supplemental vertical supports is relatively inexpensive. The functional use of the spaces may be affected by the installation, but often this is minor compared to other alternatives. Installations in the US have been made for a very small percentage of the replacement costs for the building.

建筑类英文及翻译