| 1. |
- Karlsson, Freddie, et al.
(författare)
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Dynamic response of driven end-bearing piles and a pile group in soft clay : an experimental validation study
- 2022
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Ingår i: Engineering structures. - : Elsevier BV. - 0141-0296 .- 1873-7323. ; 267
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents novel measurement data on the dynamic soil-structure interaction of an end-bearing pile foundation. The purpose is to assess the ability to predict the foundation impedances based on the small-strain properties of the soil obtained from site investigations. Measurements were performed in two stages of construction, allowing to assess interaction between the piles through the soil. First, single pile impedances and interaction factors between the piles were experimentally obtained for the four piles when they were free to move at the surface. Second, the impedances of the square pile group were measured after casting a concrete pile cap. The piles were additionally instrumented with accelerometers at depth along the centerline of each pile, allowing to illustrate the global behaviour of the piles within the soil. Numerical predictions based solely on information of the small-strain soil properties obtained from extensive site investigations are compared to the experimental results. The impedances of the individual piles are overestimated compared to the measurements, while the interaction factors show a better agreement. The pile group impedances are better captured than the individual ones, using the same soil model. The pile-soil-pile interaction is clearly manifested in the experimental results by pronounced peaks in the pile group vertical impedance, validating results from previous numerical studies.
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| 2. |
- Theland, Freddie, et al.
(författare)
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Assessment of small-strain characteristics for vibration predictions in a Swedish clay deposit
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Environmental vibrations induced by human activities such as traffic, construction or industrial manufacturing can cause disturbance among residents or to vibration sensitive equipment inbuildings. In Sweden, geological formations of soft clay overlying a stiff bedrock are soil conditions prone to ground vibrations that are encountered both in urban areas and along parts of the national railway network. This paper presents an extensive investigation of the small-strain soil properties for the prediction of environmental ground vibrations in a shallow clay where the bedrock is situated at 7.5 m depth. The small-strain properties are estimated using available empirical correlations, bender elements, seismic cone penetration tests, seismic refraction and inversion of surface wave dispersion and attenuation curves. The results are synthesised into a dynamic layered soil model which is validated by measurements at the soil’s surface at source-receiver distances up to 90 m in the frequency range 1–80 Hz. Analyses of uncertainties in the estimated values of wave speeds and material damping are performed by model investigations, indicating that surface wave tests overestimate the damping compared to bender element tests. The properties of the topmost unsaturated part of the soil is found to have a significant influenceon the response at large distances, caused by critically refracted P-waves resonating in the top layer.
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| 3. |
- Theland, Freddie, et al.
(författare)
-
Assessment of small-strain characteristics for vibration predictions in a Swedish clay deposit
- 2021
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Ingår i: Soil Dynamics and Earthquake Engineering. - : Elsevier BV. - 0267-7261 .- 1879-341X. ; 150
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Tidskriftsartikel (refereegranskat)abstract
- Environmental vibrations induced by human activities such as traffic, construction or industrial manufacturing can cause disturbance among residents or to vibration sensitive equipment in buildings. In Sweden, geological formations of soft clay overlying a stiff bedrock are soil conditions prone to ground vibrations that are encountered both in urban areas and along parts of the national railway network. This paper presents an extensive investigation of the small-strain soil properties for the prediction of environmental ground vibrations in a shallow clay where the bedrock is situated at 7.5 m depth. The small-strain properties are estimated using available empirical correlations, bender elements, seismic cone penetration tests, seismic refraction and inversion of surface wave dispersion and attenuation curves. The results are synthesised into a dynamic layered soil model which is validated by measurements at the soil's surface at source-receiver distances up to 90 m in the frequency range 1-80 Hz. Analyses of uncertainties in the estimated values of wave speeds and material damping are performed by model investigations, indicating that surface wave tests overestimate the damping compared to bender element tests. The properties of the topmost unsaturated part of the soil is found to have a significant influence on the response at large distances, caused by critically refracted P-waves resonating in the top layer.
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| 4. |
- Theland, Freddie, 1989-, et al.
(författare)
-
Dynamic response of driven end-bearing piles and a pile group in soft clay: an experimental validation study
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- This paper presents an extensive measurement campaign of the dynamic response of driven end-bearing piles and a pile group in soft clay. Results from measurements conducted on the free-top piles and and the piles joined in a concrete cap are presented. The measured frequency responses are subsequently used to obtain the impedances, characterising the dynamic stiffness and damping of the piles and the pile foundation. The piles are instrumented with accelerometers at several points along the length of the piles which allows to validate the dynamic motion of the piles atdepth due to pile head and pile cap excitation. Numerical predictions based solely on information of the small-strain soil properties obtained from extensive site investigations are compared to the experimental results. The numerical model captures the pile-soil-pile interactions and the motion of the piles within the soil well, suggesting that reliable predictions can be made for the considered soil conditions if the small-strain soil properties are well known.
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| 5. |
- Zangeneh, Abbas, 1980-, et al.
(författare)
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Modal analysis of coupled soil-structure systems
- 2021
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Ingår i: Soil Dynamics and Earthquake Engineering. - : Elsevier BV. - 0267-7261 .- 1879-341X. ; 144
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents an efficient approach for the modal analysis of coupled soil-structure systems, for which the dynamic response is strongly influenced by the embedment in the soil. The methodology is based on a finite element-perfectly matched layer model that allows for the derivation of frequency-independent system matrices and the computation of the modal properties of the coupled system. This is achieved by solving a nonlinear eigenproblem using a Compact Rational Krylov (CoRK) eigensolver. A procedure is developed to sort the computed eigenpairs, filter out the spurious modes of the system which are related to the near-field and truncated far-field soil subdomains and select the physical structural modes of system. The proposed method can be used in the dynamic assessment and structural identification of strongly coupled soil-structure systems such as fully or partially buried structures and allows for the interpretation of experimentally identified modal properties of these systems, especially in the presence of highly damped or closely spaced coupled modes. The applicability and the scalability of the proposed approach for 2D and 3D problems is demonstrated in two case studies.
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| 6. |
- Zangeneh Kamali, Abbas, 1980-
(författare)
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Dynamic Soil-Structure Interaction Analysis of Railway Bridges : Numerical and Experimental Results
- 2018
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The work reported in this thesis presents a general overview of the dynamic response of short-span railway bridges considering soil-structure interaction. The study aims to identify the effect of the surrounding and underlying soil on the global stiffness and damping of the structural system. This may lead to better assumptions and more efficient numerical models for design.A simple discrete model for calculating the dynamic characteristics of the fundamental bending mode of single span beam bridges on viscoelastic supports was proposed. This model was used to study the effect of the dynamic stiffness of the foundation on the modal parameters (e.g. natural frequency and damping ratio) of railway beam bridges. It was shown that the variation in the underlying soil profiles leads to a different dynamic response of the system. This effect depends on the ratio between the flexural stiffness of the bridge and the dynamic stiffness of the foundation-soil system but also on the ratio between the resonant frequency of the soil layer and the fundamental frequency of the bridge.The effect of the surrounding soil conditions on the vertical dynamic response of portal frame bridges was also investigated both numerically and experimentally. To this end, different numerical models (i.e. full FE models and coupled FE-BE models) have been developed. Controlled vibration tests have been performed on two full-scale portal frame bridges to determine the modal properties of the bridge-soil system and calibrate the numerical models. Both experimental and numerical results identified the substantial contribution of the surrounding soil on the global damping of short-span portal frame bridges. A simplified model for the surrounding soil was also proposed in order to define a less complicated model appropriate for practical design purposes.
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