A series of earthquakes, the highest of magnitude $$\text{ M }_\mathrm{w}$$
 5.9, hit a portion of the Po Valley in Northern Italy, which was only recently classified as seismic. The paper reports the findings and the lessons learnt from a preliminary field survey which was conducted immediately after the second event. As a result of the economic attitude of the affected area, and possibly of the characteristics of the event, an unprecedented number of industrial precast buildings were affected, resulting into most of the casualties as well as in large economic losses. Whereas most of the damaged and collapsed buildings were designed for gravity loads only, evidence of poor behavior of some precast buildings designed according to seismic provisions were discovered. The paper provides a description of the performance of precast buildings, highlighting the deficiencies that led to their poor behavior as well as some preliminary recommendations.

/pdf/performance-of-industrial-buildings-during-the-emilia-25r7na0lix.pdf

Performance of industrial buildings during the Emilia earthquakes in Northern Italy and recommendations for their strengthening

Shaking-table experiments of relatively large-scale specimens play a fundamental role in deepening our understanding of seismic response of existing structures and verification of numerical models. However, and in apparent contradiction, the preparation of such a dynamic laboratory experiment requires a-priori advanced numerical simulations, necessary to both fine-tune the test specimen properties and calibrate the input motion, as a function of the objectives of the test and capabilities and characteristics of the shaking table. This research thus concerns the development of a fibre-based finite elements model of a halfscale 3D reinforced concrete frame tested under dynamic conditions at the European Centre for Training and Research in Earthquake Engineering (EUCENTRE, Pavia, Italy). Since this reduced-scale specimen is very much based on a full-scale counterpart previously tested under pseudo-dynamic conditions at the European Laboratory for Structural Assessment (ELSA) of the Joint Research Centre (JRC, Ispra, Italy), the first part of the work consisted in verifying that the software tool employed in the numerical simulations was capable of duplicating the pseudo-dynamic real test results. Having successfully met the latter objective, the second part of the work consisted in the attempted numerical simulation of the shaking table tests, with a view to ascertain that the response of the model will be within the envisaged response targets and that the necessary input motion is compatible with the shaking-table characteristics.

/pdf/numerical-model-of-a-reinforced-concrete-building-earthquake-eexjnd7itz.pdf

Numerical Model of a Reinforced Concrete Building: Earthquake Analysis and Experimental Validation

The most common structural system of the precast industrial buildings in Europe consists of an assemblage of cantilever columns tied together with beams. Typical beam-to-column connection in these structures is constructed with steel dowels. Although this system has been used for decades, its seismic response was poorly understood, which reflected in ambiguous code requirements and conservative approach. Therefore, along with innovative precast structural solutions (not discussed in this paper), this system was the main focus of the continuous European research in the past two decades. The key results of this vast research effort (including unprecedented cyclic, PSD and shake table experiments on large-scale structures) led by the associations of the precast producers in Europe and the Politecnico di Milano are presented and discussed in this paper. The details are provided for the work done at the University of Ljubljana. The results of these research projects led to some major modifications and improvements of the relevant chapter in Eurocode 8, when this was evolving from the initial informative annex to the final code provision. Refined FEM models for the complex behaviour of the dowel beam-to-column connections as well as macro models for the post-critical analysis of the complete structures were proposed. Single-storey and multi-storey structures were investigated and the design formulas to estimate high shear and storey-force amplification due to higher-modes effect in multi-storey structures were derived. The design guidelines for connections of precast structures under seismic actions were prepared. Systematic risk studies were done indicating that this structural system can be safe in seismic regions if all Eurocode 8 provisions as well as the recommendations based on the presented research are considered. These include the capacity design of the connections. Behaviour factor for such precast systems was studied and the values initially proposed in preEC8 were modified (increased). However, it was shown that drift limitations typically govern the design and that the nominal value of the behaviour factor is not so decisive. The key factors contributing to the good seismic behaviour of this system (assuming that the connections are properly designed) is the low value of the compressive axial force in the columns confined with adequate hoops and the overstrength caused by drift limitation requirements. Cladding-to-structure interaction has been one of the most poorly understood components of the system, which is now the topic of the on-going research.

https://link.springer.com/content/pdf/10.1007%2F978-3-319-07118-3_4.pdf

Seismic Response of Precast Industrial Buildings

Seismic isolation code developments and significant applications in Turkey

This paper investigates the effectiveness of the use of seismic isolation devices on the overall 3D seismic response of curved highway viaducts with an emphasis on expansion joints. Furthermore, an evaluation of the effectiveness of the use of cable restrainers is presented. For this purpose, the bridge seismic performance has been evaluated on four different radii of curvature, considering two cases: restrained and unrestrained curved viaducts. Depending on the radius of curvature, three-dimensional non-linear dynamic analysis shows the vulnerability of curved viaducts to pounding and deck unseating damage. In this study, the efficiency of using LRB supports combined with cable restrainers on curved viaducts is demonstrated, not only by reducing in all cases the possible damage, but also by providing a similar behavior in the viaducts despite of curvature radius.

/pdf/seismic-performance-of-isolated-curved-steel-viaducts-under-2tlyi50vfm.pdf

Seismic performance of isolated curved steel viaducts under level II earthquakes

This chapter will discuss the damage that can be done to structures from an earthquake. Structural damage does not usually occur until the earthquake approaches 5.0 and is caused by the failure of the surrounding soil or from strong shaking. Damage also results from surface ruptures, the failure of nearby lifelines, or the collapse of more vulnerable structures. Problem soils and structural problems can also be a result of damage. The chapter discusses liquefaction, landslides, weak clay, foundation failure foundation connections, soft story, torsional moments, shear, flexural failure, connection problems, and problem structures.

Mark Yashinsky

Papers

Earthquake Damage to Structures