Papers by Keyword: Seismic Damage

Abstract: The May 2012 Emilia earthquake has highlighted the important vulnerability of masonry spires at the top of bell towers of churches. Indeed, almost half of those in the epicentral area have shown a typical damage mechanism consisting in the shear sliding and overturning of the top of the spire. Given the recurrence of this phenomenon, the present paper tries to provide a contribution to the comprehension of the seismic behaviour of the spires through the numerical analysis of three case studies. In particular, the work analyses the spires of the churches of San Nicola di Bari in Cortile, near Carpi (MO); Sant'Egidio in Cavezzo (MO), and Sant'Agostino in Sant'Agostino (FE). The numerical models of these masonry structures were made using Abaqus Finite Element software. After the creation of the three-dimensional geometric models, a first nonlinear static analysis of the entire bell tower was performed adopting for masonry the Abaqus “concrete damage plasticity model”. Once the stability of the bell tower was verified for dead loads, the non-linear time-step dynamic analysis was faced. This required the definition of the seismic input at the base of the tower, through the accelerograms recorded by the closest stations. The nonlinear dynamic analysis of the global model of the bell tower provided the floor response spectra at the base and at the top of the spire. Indeed the comparison between spectra at the ground and at the top highlights the filter effect of the stem of the bell tower with a significant increase in accelerations at the top. This effect may explain the widespread damage observed at the top of the spires. Eventually, three different non-invasive intervention techniques were proposed in compliance with the principles of restoration and were modelled to compare their behaviour.

Abstract: The historical masonry buildings are characterised by a great vulnerability regard the seismic action, as the recent events occurred in Central Italy have highlighted. During the seismic emergency the authors, in collaboration with the Civil Protection Department as part of the ReLUIS activities, have carried out usability inspections, analysing also the case study described in this paper. The structure, a school in Teramo, was already affected by previously seismic damages and it has been highly involved by the seismic events abovementioned. In this work the results of first inspection, reported in the AeDES form, and a more accurate visual inspection are presented in terms of detection of the crack patterns and evaluation of the seismic damages index. Moreover the vulnerability index has been calculated according to the GNDT 2° level method. The vulnerability index is finally used to calculate the damage index expected for the seismic intensity registered during the seismic event of October 30, 2016, and compared with the observed post-seismic damage level.

Abstract: This paper deals with research related to repair and strengthening of weak and brittle masonry infills in R.C. or steel frame structures. Masonry infills are commonly used in 20th century architectural heritage residential and office buildings. In case of earthquake damage to the weak and brittle masonry infills the commercial buildings go out of service and residents of residential buildings are prohibited from living in their homes although the main frame structure is not damaged. The new retrofitting method proposed in this paper may be either a preventive seismic improvement or a quick emergency intervention before seismic aftershocks: it is proposed to use a polymer PM to fill new horizontal and vertical joints between infilling masonry and frame or to fill cracks generated by the earthquake. The test results presented in the paper confirmed ability of polymer PM to fulfil requirements of quick repair material for seismic area.

Abstract: People remained optimistic about the safety of the space grid structures, because the seismic damages of space grid structures were quite rare and rather light. However, two space grid structures got damaged in 2013 Lushan Ms 7.0 earthquake. The two structures are the double-layer reticulated shell structure and flatbed grid structure, namely Lushan Gymnasium and Lushan Middle School Gymnasium respectively. This paper briefly reviews the seismic damage phenomena of grid structures in historical earthquakes, and then focuses on the two damaged space grid structures in Lushan earthquake. The reason why the two space grid structures got damaged are derived from the force state analysis of the rods, ball joints and bearings. Finally, we come up with the effective advice for the seismic design and construction of the space grid structure.

Abstract: In North-south earthquake belt, half of more than Ms 8.0 great earthquakes were centralized since the history records were existed in our country. In order to study the typical buildings in this seismic belt, the seismic damages of the typical buildings occurred during 22 earthquakes in North-south earthquake belt, whose earthquake magnitude were more than Ms 6.0, were organized and analyzed. The seismic damage and its matrix of kinds of buildings belonging to the North-south earthquake belt in different intensities were obtained. The statistic results were obtained by comparison and analysis. According to the results of analysis, the seismic capacity of kinds of typical buildings in this region was provided: reinforced concrete frame structure showed fine seismic capability in all previous earthquake whose seismic damage was the slightest in the real statistics results; secondly were those of masonry and mortised timber frame buildings; the seismic damage of buildings, which was combined with timber frame and soil, stone, brick walls was the most serious.

Abstract: Seismic damage was the key reason which resulted in the serviceability degradation or collapse of the bridge. How to quantify the seismic damage and evaluate the seismic performance of the bridge under earthquakes through the damage analysis was the significant research direction in the performance based seismic design. In this paper the Park-Ang model (a well-known dual parameters model) and its modification version used for the damage evaluation of the concrete structure were compared. Furthermore, through the definition of the damage indices of the models based on the modified Park-Ang model and the descending slope of the IDA(incremental dynamic analysis) curve, the seismic damage levels of the typical bridge in the urban rail transit line under the designated earthquakes were analyzed, respectively. It was shown from the results that the calculated results from the two model was essentially consistent. The damage analysis based evaluation method was feasibly used for the seismic performance evaluation of the bridge.

Abstract: The seismic damage of nonstructural system is severely, and has affect escaped from building and rescue. Suspending system is the typical one of the nonstructural system. This paper investigated the seismic damage of suspending system in Lushan earthquake. Suspending system of many buildings are failure, especially for the hospital and gymnasium which is used for disadvantaged group and rescue. Moreover, design of suspending systerm is lack of industrial standards, so much attention should be paid.

Abstract: As an important part of earthquake disaster relief, highway traffic system is the passage for rescue staffs, material transport and evacuation. Hence, people are concerned about destruction condition and safety of highways after earthquakes. However, there are neither systematically scientific methods to classify highway subgrade seismic damage, nor systematic study on its rapid evaluation methods. Therefore, the Paper studies post-seismic highway subgrade damage grade and rapid evaluation methods, to be as a significant reference for improving post-seismic emergency rescue and relief efficiency, as well as for recovering and reconstructing highway traffic system.

Abstract: The curved bridges suffered severe damages or even collapsed during 2008 Wenchuan Earthquake. A field survey of seismic performance of RC curved bridges was examined. Damage patterns and the probable causes of RC curved bridges including Baihua bridge and ramp bridge of Huilan interchange are presented and analyzed in this paper. The main failure was pure shear failure or shear-flexural failure of the pier columns. Bearings and expansion joints damage were another common failure pattern. Lesson learned from the damage of RC curved bridges in this earthquake, the recommendations on the seismic design of RC curved bridges are presented involving ductility of bridge columns, design of curved bridges, design of bearings and devices preventing girders falling down. Suggestions for the future seismic design and retrofitting of RC curved bridges are also presented in moderate to severe earthquake area.

Abstract: Epicentral distance and seismogeonic fault distances as crucial ground motion parameters of attenuation relationship are widely accepted indexes for rapid assessment of seismic scenario. Based on the geographical information of 379 heavily damaged dams in Wenchuan Earthquake, 2008, China, the distribution of damaged dams is analyzed statistically. Specifically, the correlation of damage rate & epicentral distance and that of damage proportion & seismogenic fault distance are compared, and corresponding equations are developed respectively using least square methods. The investigation shows that there exists a closer relationship between seismic damage and seismogenic fault distance than between damage and epicentral distance for Wenchuan earthquake. It is concluded that the index of seismogenic fault distance is more applicable to large earthquake, while Epicentral distance is a more accurate index for small and mid-level earthquakes.