scholarly journals Seismic analysis of a highway bridge considering soil-structure interaction effects

1979 ◽  
Vol 12 (4) ◽  
pp. 305-313
Author(s):  
Toshio Iwasaki ◽  
Kazuhiko Kawashima
Keyword(s):  
Seismic Response ◽  
Natural Frequency ◽  
Soil Structure ◽  
Soft Soil ◽  
Ground Surface ◽  
Highway Bridges ◽  
Interaction Effects ◽  
Soil Structure Interaction ◽  
Structure Interaction ◽  
Fundamental Natural Frequency

In analyzing seismic behaviour of highway bridges constructed on soft soil deposits, it is important to take account of soil-structure interaction effects. In this paper, seismic response of a bridge pier-foundation is investigated based on earthquake acceleration records measured simultaneously on the pier crest and on the ground surface near that bridge. Four motions were used in the analysis, i.e., two were induced by two earthquakes with magnitudes of 7.5 and 6.6, respectively; and two by their aftershocks. In the former two earthquakes, the maximum accelerations were 186 and 438 gals on the ground surface, and 310 and 230 gals on the pier top, respectively. Analyses of frequency characteristics of the motions showed that the predominant frequencies of pier-foundation were always approximately identical with the fundamental natural frequency of the subsoil. Analyses of micro-tremors measured at the sites revealed that the natural frequency of the pier-foundation system is higher than the fundamental natural frequency of the subsoil. Analytical models were formulated to calculate the seismic response of the pier-foundation assuming the subsoil and pier-foundation to be a shear column model with an equivalent linear shear modulus and an elastically supported beam on the subsoil, respectively. Bedrock motions were computed from the measured ground surface motions and then applied to the bedrock of the analytical model. The seismic responses of pier-foundation were thus calculated and compared with the measured records giving a good agreement.

scholarly journals Effect of Soil-Structure Interaction on the Seismic Response of Existing Low and Mid-Rise RC Buildings

2020 ◽  
Vol 10 (23) ◽  
pp. 8357
Author(s):  
Ibrahim Oz ◽  
Sevket Murat Senel ◽  
Mehmet Palanci ◽  
Ali Kalkan
Keyword(s):  
Seismic Response ◽  
Seismic Performance ◽  
Soil Structure ◽  
Soft Soil ◽  
Soil Structure Interaction ◽  
Soil Conditions ◽  
Existing Buildings ◽  
Structure Interaction ◽  
Fixed Base ◽  
New Buildings

Reconnaissance studies performed after destructive earthquakes have shown that seismic performance of existing buildings, especially constructed on weak soils, is significantly low. This situation implies the negative effects of soil-structure interaction on the seismic performance of buildings. In order to investigate these effects, 40 existing buildings from Turkey were selected and nonlinear models were constructed by considering fixed-base and stiff, moderate and soft soil conditions. Buildings designed before and after Turkish Earthquake code of 1998 were grouped as old and new buildings, respectively. Different soil conditions classified according to shear wave velocities were reflected by using substructure method. Inelastic deformation demands were obtained by using nonlinear time history analysis and 20 real acceleration records selected from major earthquakes were used. The results have shown that soil-structure interaction, especially in soft soil cases, significantly affects the seismic response of old buildings. The most significant increase in drift demands occurred in first stories and the results corresponding to fixed-base, stiff and moderate cases are closer to each other with respect to soft soil cases. Distribution of results has indicated that effect of soil-structure interaction on the seismic performance of new buildings is limited with respect to old buildings.

Influence of Foundation Type on Seismic Performance of Buildings Considering Soil–Structure Interaction

2016 ◽  
Vol 16 (08) ◽  
pp. 1550043 ◽  
Author(s):  
Aslan S. Hokmabadi ◽  
Behzad Fatahi
Keyword(s):  
Seismic Response ◽  
Pile Foundation ◽  
Soil Structure ◽  
Soft Soil ◽  
Shallow Foundation ◽  
Shaking Table ◽  
Soil Structure Interaction ◽  
Structure Interaction ◽  
Raft Foundation ◽  
Different Types

In selecting the type of foundation best suited for mid-rise buildings in high risk seismic zones, design engineers may consider that a shallow foundation, a pile foundation, or a pile-raft foundation can best carry the static and dynamic loads. However, different types of foundations behave differently during earthquakes, depending on the soil–structure interaction (SSI) where the properties of the in situ soil and type of foundation change the dynamic characteristics (natural frequency and damping) of the soil–foundation–structure system. In order to investigate the different characteristics of SSI and its influence on the seismic response of building frames, a 3D numerical model of a 15-storey full-scale (prototype) structure was simulated with four different types of foundations: (i) A fixed-based structure that excludes the SSI, (ii) a structure supported by a shallow foundation, (iii) a structure supported by a pile-raft foundation in soft soil and (iv) a structure supported by a floating (frictional) pile foundation in soft soil. Finite difference analyzes with FLAC3D were then conducted using real earthquake records that incorporated material (soil and superstructure) and geometric (uplifting, gapping and [Formula: see text] effects) nonlinearities. The 3D numerical modeling procedure had previously been verified against experimental shaking table tests conducted by the authors. The results are then presented and compared in terms of soil amplification, shear force distribution and rocking of the superstructure, including its lateral deformation and drift. The results showed that the type of foundation is a major contributor to the seismic response of buildings with SSI and should therefore be given careful consideration in order to ensure a safe and cost effective design.

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