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Efraimiadou S.,Consulting engineer | Hatzigeorgiou G.D.,Democritus University of Thrace | Beskos D.E.,University of Patras | Beskos D.E.,Academy of Athens
Earthquake Engineering and Structural Dynamics | Year: 2013

The effect of collision between adjacent reinforced concrete building frames under multiple earthquakes is investigated in this paper. The four planar frames and the nine different pairs of adjacent reinforced concrete structures of the first companion paper are also examined here, under five real seismic sequences. Such a sequence of earthquakes results in a significant damage accumulation in a structure because any rehabilitation action between any two successive seismic motions cannot be practically materialised because of lack of time. Various parameters are investigated, such as the maximum horizontal displacement of top floor, ductility of columns, permanent displacements and so on. Furthermore, four different separation gaps between the building frames are considered to determine their influence on the behaviour of these frames. It is concluded that in most of the cases, the seismic sequences appear to be detrimental in comparison with the single seismic events. © 2013 John Wiley & Sons, Ltd.

Efraimiadou S.,Consulting engineer | Hatzigeorgiou G.D.,Democritus University of Thrace | Beskos D.E.,University of Patras | Beskos D.E.,Academy of Athens
Earthquake Engineering and Structural Dynamics | Year: 2013

The effect of different structures configurations on the collision between adjacent planar RC building frames subjected to strong earthquakes is examined in this paper. Two 5-storey and two 8-storey frames, regular or with setbacks, are combined together to produce nine different pairs of adjacent RC structures. These pairs of buildings are subjected to six strong ground motions that are absolutely compatible with the design process. Various parameters are investigated such as maximum displacements, permanent displacements, members' ductility and internal forces and interstorey drift ratios. It is concluded that the effect of collision of adjacent frames seems to be unfavourable for most of the cases and, therefore, the structural pounding phenomenon is rather detrimental than beneficial. © 2013 John Wiley & Sons, Ltd.

Hatzigeorgiou G.D.,Democritus University of Thrace | Kanapitsas G.,Consulting engineer
Earthquake Engineering and Structural Dynamics | Year: 2013

SUMMARY: Fundamental period of vibration appears to be one of the most critical parameter for the seismic design of buildings because this period strongly affects the magnitude of seismic forces. In this paper, an empirical formula for estimating the fundamental period of reinforced concrete structures is recommended, on the basis of the vibration analysis of 20 different real building configurations. These structures have already been constructed in Greece, and they are analyzed by using in detail 3-D finite element models and modal eigenvalue analysis. These models take into account the presence of external and internal infill walls, which are usually ignored as nonstructural elements. This neglect leads to unreliable evaluation of period because the infill walls' contribution to the lateral stiffness and therefore to the fundamental period of vibration is also ignored. Furthermore, taking into account that the flexibility of soil elongates the fundamental period, the soil-structure interaction effect is also considered. To achieve a unique, simple, and effective empirical expression for the fundamental period of vibration, a comprehensive nonlinear regression analysis is applied for the datasets of buildings under consideration. This empirical expression is also compared with the similar expressions from the pertinent literature. © 2013 John Wiley & Sons, Ltd.

Warner J.,Consulting engineer
Geotechnical Special Publication | Year: 2012

Faulty concrete in a new 3-meter- (10-foot-) thick, heavily reinforced foundation for a power plant required construction to stop. Pressure grouting was selected as the most effective remedial method as appropriate grout hole testing could supplement the investigation findings and, if systematically performed, both identify the faulty conditions and verify their correction. A regular grid of grout holes was drilled, pressure tested, and categorized for further treatment. Depending upon the water test results, the holes were pressure grouted, vacuum grouted, or simply tremie filled with a pre-blended ultrafine cementitious grout. Secondary and tertiary holes were added to the work where behavior of the primary holes left doubt as to the resulting conditions. The repaired foundation was accepted by the design engineer and owner, after virtual no-take in successive grout holes and further verification core holes indicated all substantial voids had been filled. © 2012 American Society of Civil Engineers.

Thompson M.K.,KAIST | Thompson J.M.,Consulting engineer
Scanning | Year: 2010

This work discusses some of the benefits, techniques, challenges, and considerations associated with the incorporation of measured surfaces in finite element (FE) models including how much surface data to measure and import into the model, the shape of the surface geometry to create, the presence and effect of surface layers and impurities, the required mesh density for rough surfaces, the nature of the element formulations and material properties at small length scales, the differences between measurement and FE coordinate systems, the limitations and idealizations of the FE method, issues associated with boundary conditions and their ability to impose or prevent conformal contact, and issues associated with the size of the pinball region and the contact stiffness relative to the nature of the surface. It also describes some current and future research directions that can be used to validate and expand existing techniques and to improve our understanding of surface phenomena. © 2010 Wiley Periodicals, Inc.

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