Design Criteria for Seismic Resistant Steel Structures
The paper presents the state-of —the art in the design of the steel structures, in the light of the lessons learned from the last great earthquakes: Michoacan (1985), Loma Prieta (1989), Northridge (1994) and Kobe (1995). In the introduction, the very rec
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DESIGN CRITERIA FOR SEISMIC RESISTANT STEEL STRUCTURES
V. Gioncu Politechnica University Timisoara, Timisoara, Romania
Abstract. The paper presents the state-of -the art in the design of the steel structures, in the light of the lessons learned from the last great earthquakes: Michoacan ( 1985), Lorna Prieta ( 1989), Northridge (1994) and Kobe (1995). In the introduction, the very recent progress in the conception and design are presented, showing the challenge for future research works. The design criteria as multi-level design approaches and rigidity, stiffness and ductility demands are detailed, emphasizing the unsolved problems. New aspects for ground motion modeling, as the differences between near-source and far-source earthquakes are examined. The response of the structure to these near-source earthquake is examined, taking into account the influence of superior vibration modes, velocity and strain-rate, vertical components, etc. The final conclusions consider that now is the right moment to introduce some new provisions in the design codes, in order to fill the gap that exists between the accumulated knowledge and design codes.
1. INTRODUCTION 1.1 The nature of the problem The main purpose of structural design is to produce a suitable structure, in which one must consider not only the initial cost, but also the cost of maintenance, damage and failure, together with the benefits derived from the structure function. Thus, the optimum design of structure requires a clear understanding of the role of each of above aspects and therefore, it requires general view on the total process. This objective can be achieved by the engineer, involved in designing of a specific building, without great problems for conventional actions as dead, live wind, and snow loads, but with difficulties for exceptional loads produced by natural disasters as hurricanes, floods, earthquakes, etc. Among these natural disasters, earthquakes were responsible for almost 60 percent of deaths and damage. Every strong earthquake is responsible of large losses of lives and of goods. In the past, during each event, the number of deaths was always very high, but it continues to be also very important at the time being. The analysis of these events shows that not only the ground motion severity is the main responsible of these losses in live. Indeed, the main feature of earthquake is that the most of the human and economic losses are not due to the earthquake mechanism, but to failure of human facilities, buildings, bridges, transport systems, dams, etc, which have been designed and constructed for the comfort of human being. So, in many cases of building collapses, the builders are thyself the producer of killing tools. The more important losses in life are always concentrated in the poor zones with ancient buildings or with very poorly built constructions. In exchange, the important economic losses are F. M. Mazzolani et al. (eds.), Seismic Resistant Steel Structures © Springer-Verlag Wien 2000
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