The building codes requirements for seismic design have evolved from crude treatment of the subject to sophisticated methodology addressing all factors affecting the behavior of the structure under earthquake excitation.
Each one of these codes treated the seismic provisions and requirement differently. Different states and Municipalities adopted different Codes. In the three organizations that produced and published the three model codes formed the International Code Council ICC. The purpose of the ICC is to develop and maintain a single building code.
Before the publication of the first edition of the International Building Code in , seismic risk and subsequently seismic design criteria in building codes depended only on the level of the earthquake ground motion. The concept of seismic zone was used. Zone 0 was where the earthquake ground motion the weakest and zone 4 the strongest.
The method of analysis, height limits and level of detailing depended on the seismic zone in which a structure was located.
Recognizing that structure performance during an earthquake depends not only on the level of the earthquake ground motion, but also on the nature of the soil on which the structure is founded, the International Building Code IBC established the Seismic Design Categories SDC as a measure for the seismic risk for a certain structure. The SDC is a function of the level of the earthquake ground motion, the soil nature at the site and the use of the structure.
The SDC is used to determine the allowed method of analysis, height limits and level of detailing. It is uneconomical to design a structure to respond in the elastic range to the inertial forces caused by the maximum considered earthquake.
Concrete Buildings in Seismic Regions by George G. Penelis, Gregory G. Penelis - jacnifeccadysp.cf
Accordingly, the design seismic lateral forces prescribed in the IBC and ASCE are less than the elastic response inertial forces caused by the intended design earthquake. The purpose of these detailing and proportioning requirements is to avoid all forms of brittle failure and insures that the structure will have sufficient inelastic deformability.
This is to enable the structure to survive without collapse when subjected to several cycles of loading within the inelastic range. This publication gave earthquake-resistant design of multistory reinforced concrete buildings more of a scientific basis than it ever had before. And today, it still assists engineers and researchers understand the basis of seismic design concepts. The authors wrote in their preface, " It is an art as well as a science This is especially so in earthquake-prone regions, as, even there, seismic design of structures is relatively recent.
In those regions the major part of the seismic threat to human life and property comes from old buildings. Due to the infrastructure's increasing decay, frequently combined with the need for structural upgrading to meet more stringent design requirements especially against seismic loads , structural retrofitting is becoming more and more important and receives today considerable emphasis throughout the world. In response to this need, a major part of the fib Model Code , currently under development, is being devoted to structural conservation and maintenance.
More importantly, in recognition of the importance of the seismic threat arising from existing substandard buildings, the first standards for structural upgrading to be promoted by the international engineering community and by regulatory authorities alike are for seismic rehabilitation of buildings.
Seismic assessment and retrofit of reinforced concrete buildings
It is also the case of the recent ASCE draft standard on Seismic evaluation of existing buildings and of the Law for promotion of seismic strengthening of existing reinforced concrete structures in Japan. As noted in Chapter 1 of this Bulletin, fib - as CEB and FIP did before - has placed considerable emphasis on assessment and rehabilitation of existing structures. The present Bulletin is a culmination of this effort in the special but very important field of seismic assessment and rehabilitation.
It has been elaborated over a period of 4 years by Task Group 7.
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- Concrete Buildings in Seismic Regions - George G. Penelis - Google книги.
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- Concrete Buildings in Seismic Regions.
In October the final draft of the Bulletin was presented to public during the 1st fib Congress in Osaka. It was also there that it was approved by fib Commission 7 Seismic Design. The contents is structured into main chapters as follows: 1 Introduction - 2 Performance objectives and system considerations - 3 Review of seismic assessment procedures - 4 Strength and deformation capacity of non-seismically detailed components - 5 Seismic retrofitting techniques - 6 Probabilistic concepts and methods - 7 Case studies.