Implications of Recent Earthquakes on Seismic Risk

The following sections are included:

• Dedication

• Contents

Two earthquakes have recently caused unexpected levels of damage, considering their locations and characteristics. The earthquake of Kocaeli (M_s=7.4) in Turkey caused damage of over $10 billion and a death toll of more than 20,000, whilst that of Mt. Parnes in Greece (M_s=5.9) caused 145 deaths and about $2 billion in direct costs. Whilst the former occurred on a well known fault of historical and recent activity, the latter is in an area categorised as of very low seismic activity until 1995. In this paper, a process of contrasting the hazard features of the two environments coupled with analysis of structural response is presented. It is concluded that in the case of Turkey, the level of damage cannot be explained on the basis of poor construction quality alone. In the case of northern Athens, the message is indeed different. Taking into account the low levels of demand imposed, the extent of damage is likely to have been more affected by construction quality than in the Turkey earthquake case.

The following sections are included:

• Introduction

• Structural Observations

• Elastic and Inelastic Spectra

• Structural Response

• Conclusions

• References

The following sections are included:

• Introduction

• Kocaeli, Turkey Earthquake
  • Fault and Damage of Transportation Facility
  • Collapse of Arifiye Bridge

• Chi Chi, Taiwan Earthquake
  • Collapse of Bei-Fong Bridge
  • Collapse of Wu-Shi Bridge
  • Damage of A Cable Stayed Bridge under Construction

• Conclusions

• Acknowledgements

• References

The following sections are included:

• Introduction

• Objectives and Scope of Temporary Restoration

• Outline of Technical Guide for Temporary Restoration
  • General Flow of Temporary Restoration Strategy
  • Damage Assessment
  • Seismic Capacity Evaluation
  • Instructions for Temporary Restoration

• Concluding Remarks

• References

The following sections are included:

• Introduction

• The research program
  • General
  • The acceleration response spectra
  • Buildings designed according to the 1959 Greek Seismic Code – Inelastic analysis
  • Buildings designed according to the New Greek Seismic Code (EC8) – Inelastic analysis
  • General evaluation of the behaviour of old and new buildings

• Conclusions

The paper reviews some of the current problems associated with the development of loss estimation methods in Europe. It reviews the damage and ground motion data collected in four recent earthquakes in Europe, those of Umbria-Marche, Italy 1997, Azores, Portugal, 1998, Kocaeli, Turkey, 1999 and Athens, Greece 1999 and considers the implications of the availability of this new data for the future development of loss estimation. It is concluded that there are severe methodological difficulties with both ‘traditional’ statistical approaches to loss estimation based on macroseismic intensity and with more recently proposed calculated approaches based on quantitative (instrumental) measures of ground shaking. Some ways forward are suggested.

The following sections are included:

• Introduction

• Overview of Building Damage in Nada Ward

• Re-estimation of Ground Motion Distribution in Nada Ward

• Vulnerability Functions of Buildings

• Conclusions

• Acknowledgement

• References

The following sections are included:

• Introduction

• Testing Procedure

• Modelling of quasi-elastic and plastic strain characteristics

• Comparison between observed and simulated behaviours

• Conclusions

• References

The following sections are included:

• Introduction

• Criteria for the Selection and Scaling of Real Accelerograms
  • Minimum Requirements of Accelerograms as Design Input
  • Scaling Techniques and Strong-Motion Parameters
  • Parameters for the Selection of Real Records

• The Coverage of Search Scenarios in the Current Strong-Motion Databank
  • Compilation of the Strong-Motion Databank
  • Magnitude and Distance Distribution of Databank
  • The Influence of the Site Geology

• Discussion and Conclusions

• Acknowledgements

• References

This paper presents a soil-structure interaction (SSI) macro-element for shallow foundations on cohesive soil. Describing the cyclic behaviour in the near field of the foundation, it reproduces the material non-linearities of the soil under the foundation as well as the geometrical non-linearities (uplift) at the soil-structure interface. The macro-element, expressed in global variables, is based on a non-associated plasticity model with kinematic and isotropic hardening. The uplift of the foundation is explicitly taken into account by coupling the plasticity model with an uplift model. The uplift reduces the elastic rotational stiffness of the global model. The latter is calibrated from numerical results, obtained by the Dynaflow finite element code, specialised in soil behaviour.

The following sections are included:

• Introduction

• Objectives and methods

• Test specimens and setup

• Experimental and numerical results

• Conclusions

• Acknowledgements

• References

The following sections are included:

• Introduction

• Performance of Welded Connections

• Frames with Bolted Angle Connections

• Connection Design Parameters
  • Moment Capacity
  • Initial Stiffness
  • Connection Classification
  • Rotational Ductility

• Overall Frame Considerations
  • Stiffness and Capacity
  • Ductility Demand and Energy Dissipation
  • Behaviour Factors

• Conclusions

• References

A relatively simple and transparent nonlinear method for the seismic performance evaluation of structures (the N2 method) has been developed. The method combines the nonlinear static (pushover) analysis and the response spectrum approach. It yields results of reasonable accuracy if the structure oscillates predominantly in the first mode. In the paper, the most recent version of the method is presented, which is formulated in the acceleration – displacement format. The application of the method is illustrated by an example.

The following sections are included:

• Introduction

• Models and Loading Scheme

• Failure Modes and Capacity

• Evaluation of the Experimental Hysteretic Behaviour

• Conclusions

• Acknowledgements

• References

The following sections are included:

• Introduction

• Tensile experiment of butt-welded joints with defects
  • Outline of experiment and specimens
  • Experimental parameters and procedures
  • Fracture toughness of welded-joint zones
  • Effects of temperature and strain rate on tensile properties
  • Calculation of elongation at design maximum load and maximum load
  • Effects of material fracture roughness and artificial defects

• Cyclic loading experiment of beam-to-column connection with defects
  • Outline of experimental and specimens
  • Estimation of beam flange tensile strength by CDC method
  • Comparison with results of welded-joint tensile experiment

• Conclusions

• Acknowledgements

• References

To formulate the multi-dimensional non-linear restoring force characteristics of structures using the theory of plasticity, the analogy between two-dimensional non-linear behaviours of the very simple model structure and the theory of plasticity is examined. The model structure consists of a rigid plate and two springs. Then, loading criteria in the theory of plasticity are discussed. When the translating yield surface and the fixed yield surface are postulated, a state identification method using the loading criteria is presented. Furthermore, an error correction method is proposed in this paper.

The following sections are included:

• Introduction

• A qualitative model

• Force - transfer mechanisms

• Quasi elastic stage I

• Flexural failure of the wall (stage II^F)

• Web failure (stage II^W)

• Compressive crushing of the diagonal strut (stage II^C)

• Experimental research

• References