In many cities buildings are constructed very close to each other, sometimes without any separation gap between them, due to the high cost of the land in metropolitan areas. This is also the case for Cyprus and Greece, where the land in the city centers is limited, in combination with the very active construction development, following a similar practice with the rest of the European countries. However, Cyprus, along with Greece and other Eastern European countries, is, unfortunately, located in a high seismicity area. Therefore, poundings of adjacent buildings are very likely to occur in densely-resided areas during strong earthquakes. Already some severe damage from pounding incidences has been reported in Turkey during the Kocaeli Earthquake (1999), as well as lighter damage due to structural poundings on buildings in Greece, during the Kalamata and the Thessaloniki earthquakes.
Consequently, it is important to thoroughly investigate the possibility of poundings of buildings in order to understand their effects on their seismic response and performance. The proposed research project aims at studying the 3D dynamic response of buildings during poundings and interpreting the simulation results in order to derive useful conclusions about the consequences of poundings on the seismic performance of both conventionally fixed-supported and seismically isolated buildings. Based on the performed numerical simulations and parametric analyses, potential impact mitigation measures are also considered, in order to alleviate the detrimental effects of poundings on the seismic performance of buildings. Such impact mitigation measures may help the protection of existing buildings, as well as sensitive equipment that may be housed in them, from potential pounding incidences during strong earthquakes.
This investigation is accomplished through three-dimensional (3D) numerical simulations and parametric analyses of buildings, which are modeled as multi-degree-of-freedom (MDOF) systems with automatic impact capabilities. The simulation in three dimensions enables the consideration of torsional effects and their interactions with structural poundings. Emphasis will also be given to the simulation of the case of slabs pounding against columns, which represents the most common and worst case scenario where the slabs of adjacent buildings are at different levels that do not coincide. In addition, large numbers of 3D numerical simulations and parametric analyses of both fixed-supported and seismically isolated buildings will be performed, in order to investigate the effect of certain factors on the seismic performance of these structures under earthquake-induced poundings.
In order to efficiently and effectively perform the necessary numerical analyses and parametric studies, a flexible and extensible software application is specially designed and being developed, utilizing modern Object-Oriented Design and Programming, Design Patterns and novel computing advances. The specially developed software provides the desired flexibility, maintainability and extensibility in order to fulfill the needs of the proposed, while also facilitating extensions to accomplish future research plans. Specifically, the Java programming language is used for the computational part, while the Java application programming interfaces (API) Java2D/Java3D and Java Swing are employed for the implementation of high quality 2D/3D computer graphics (CG) and an effective graphical user interface (GUI), respectively.
The developed software consists of three main parts. The first part is the 3D analysis solver, which allow the 3D simulation of both fixed-supported and seismically isolated buildings under seismic excitations. The second part of the software is the Graphical User Interface (GUI) and the Computer Graphics modules.The third part of the software is the parametric analysis module, where large numbers of simulations will be executed automatically, while varying certain parameters, within a user-specified range of values, in order to assess their influence on the computed response.
In order to sufficiently well estimate the impact forces that should be applied at detected impact points on each structure in contact, an appropriate 3D impact model is being developed and used. In particular, a “penalty” method is implemented, in which a small interpenetration among two colliding bodies is allowed and used in combination with an impact stiffness coefficient to calculate the elastic impact forces that should be applied on the colliding bodies. Contrary to the corresponding 2D impact models, the 3D impact model is able to calculate not only the normal impact forces, but also the frictional forces that may arise between the colliding structures.
Using the developed software, a large set of numerical simulations and parametric analyses will be performed, in order to thoroughly investigate earthquake-induced poundings of both fixed-supported and seismically isolated buildings. The parametric analyses will be executed by automatically varying a certain parameter, within a user-specified range of values, so as to assess its influence on the seismic response of the buildings, while taking into account pounding incidences. The results of the conducted simulations and parametric studies will provide useful information regarding the consequences of poundings on the seismic response of buildings.