Significant and widespread liquefaction effects, which caused panic of inhabitants and damage to buildings and infrastructures, were observed in various areas of Emilia-Romagna region, Italy, during the seismic events of May 20 and 29, 2012, with magnitude respectively of Ml 5.9 and Ml. 5.8. In Italian seismic literature these phenomena represent an interesting case study for a number of reasons: for the exceptional impacts, for the size of the area in which liquefaction effects were observed, for the amount of damage produced, for the rarity of soil liquefaction Italian case histories. Immediately after the earthquake of 20 May an extensive field reconnaissance was conducted through the natural and built environment to capture as quickly as possible surface evidences of liquefaction and to document the extent and the severity of damage. The most significant and widespread liquefaction impacts were found in the two settlements of San Carlo and Mirabello. With the aim of a better understanding of the observed scenarios, a detailed investigation program, including geophysical surveys and geotechnical testing (soundings, cone penetration tests, seismic cone penetration tests, cross-hole and down-hole tests as well as many cyclic laboratory tests), was planned. These investigations are now in progress and will be object of forecoming technical notes. This paper summarizes the observation of soil liquefaction effects made during field investigations and presents a first interpretation, based on available information on ground shaking and soil conditions, of the factors that may have contributed to determine the low liquefaction resistance of soils.
earthquake damage
Current U.S. practice of seismic qualification of suspended ceilings by means of shake table tests
Suspended ceilings are among the most widely used nonstructural components. Past earthquakes have demonstrated the susceptibility of suspended ceilings to failure during seismic events. To address this vulner- ability, design codes have incorporated specific design and installation criteria for suspended ceilings. However, ceiling and grid manufacturers continue to innovate and introduce new products that are requested by engineers and architects but are not addressed in the code. Therefore, it is necessary to have the means to evaluate such prod- ucts. Because these units are difficult to analyze numerically, earthquake simulation testing can be used to assess the seismic performance of suspended ceilings. Such technique was used by one of the major manufacturers in the United States to characterize the performance of a standard code-prescribed ceiling and to use that performance as a benchmark for assessing the response of this manufacturer’s alternate installation. Testing and evaluation of data showed that the code-prescribed installation had an acceptable performance. It was also noted that the ceil- ing constructed with the proposed alternate installation performed as well as or better than the specimen installed using the code procedure. Finally, the test data revealed some of the shortcomings of the current experimental and evaluation methodology that require revisions.