Search

found 59 results

Images for foundations; more images...

Research papers, The University of Auckland Library

The influence of nonlinear soil-foundation-structure interaction (SFSI) on the performance of multi-storey buildings during earthquake events has become increasingly important in earthquake resistant design. For buildings on shallow foundations, SFSI refers to nonlinear geometric effects associated with uplift of the foundation from the supporting soil as well as nonlinear soil deformation effects. These effects can potentially be beneficial for structural performance, reducing forces transmitted from ground shaking to the structure. However, there is also the potential consequence of residual settlement and rotation of the foundation. This Thesis investigates the influence of SFSI in the performance of multi-storey buildings on shallow foundations through earthquake observations, experimental testing, and development of spring-bed numerical models that can be incorporated into integrated earthquake resistant design procedures. Observations were made following the 22 February 2011 Christchurch Earthquake in New Zealand of a number of multi-storey buildings on shallow foundations that performed satisfactorily. This was predominantly the case in areas where shallow foundations, typically large raft foundations, were founded on competent gravel and where there was no significant manifestation of liquefaction at the ground surface. The properties of these buildings and the soils they are founded on directed experimental work that was conducted to investigate the mechanisms by which SFSI may have influenced the behaviour of these types of structure-foundation systems. Centrifuge experiments were undertaken at the University of Dundee, Scotland using a range of structure-foundation models and a layer of dense cohesionless soil to simulate the situation in Christchurch where multi-storey buildings on shallow foundations performed well. Three equivalent single degree of freedom (SDOF) models representing 3, 5, and 7 storey buildings with identical large raft foundations were subjected to a range of dynamic Ricker wavelet excitations and Christchurch Earthquake records to investigate the influence of SFSI on the response of the equivalent buildings. The experimental results show that nonlinear SFSI has a significant influence on structural response and overall foundation deformations, even though the large raft foundations on competent soil meant that there was a significant reserve of bearing capacity available and nonlinear deformations may have been considered to have had minimal effect. Uplift of the foundation from the supporting soil was observed across a wide range of input motion amplitudes and was particularly significant as the amplitude of motion increased. Permanent soil deformation represented by foundation settlement and residual rotation was also observed but mainly for the larger input motions. However, the absolute extent of uplift and permanent soil deformation was very small compared to the size of the foundation meaning the serviceability of the building would still likely be maintained during large earthquake events. Even so, the small extent of SFSI resulted in attenuation of the response of the structure as the equivalent period of vibration was lengthened and the equivalent damping in the system increased. The experimental work undertaken was used to validate and enhance numerical modelling techniques that are simple yet sophisticated and promote interaction between geotechnical and structural specialists involved in the design of multi-storey buildings. Spring-bed modelling techniques were utilised as they provide a balance between ease of use, and thus ease of interaction with structural specialists who have these techniques readily available in practice, and theoretically rigorous solutions. Fixed base and elastic spring-bed models showed they were unable to capture the behaviour of the structure-foundation models tested in the centrifuge experiments. SFSI spring-bed models were able to more accurately capture the behaviour but recommendations were proposed for the parameters used to define the springs so that the numerical models closely matched experimental results. From the spring-bed modelling and results of centrifuge experiments, an equivalent linear design procedure was proposed along with a procedure and recommendations for the implementation of nonlinear SFSI spring-bed models in practice. The combination of earthquake observations, experimental testing, and simplified numerical analysis has shown how SFSI is influential in the earthquake performance of multi-storey buildings on shallow foundations and should be incorporated into earthquake resistant design of these structures.

Images, UC QuakeStudies

A damaged driveway bridge over a stream has visibly moved, scraping up some of the driveway. The photographer comments, "Our neighbour Pam Shadbolt's house, immediately behind our house, on the bank of Dudley Creek. The bridge has broken free from its foundations".

Images, UC QuakeStudies

A photograph of the earthquake damage to a house on Woodham Road. The house has come off its foundations as the bricks wall have crumbled, spilling onto the footpath in front. Road cones have been placed along the street to warn road users.

Images, UC QuakeStudies

Damage to a house in Richmond. Stucco underneath a window has cracked, and the foundation appears to be on a lean. The photographer comments, "These photos show our old house in River Rd and recovery work around Richmond and St Albans. The bay window of our bedroom has jumped off the foundations, cracking the stucco".

Images, UC QuakeStudies

Damage to the Visitors Centre in Kaiapoi, after the September 4th earthquake. The foundations have lifted at the back of the building, giving it a forward lean. Cables have been attached to the balcony over the walkway and braced to posts cemented into the ground. This is to stop the building from slumping further.

Images, UC QuakeStudies

Damage to the Visitors Centre in Kaiapoi, after the September 4th earthquake. The foundations have lifted at the back of the building, giving it a forward lean. Cables have been attached to the balcony over the walkway and braced to posts cemented into the ground. This is to stop the building from slumping further.

Images, UC QuakeStudies

Damage to a house in Richmond. Bricks have fallen from the walls onto the driveway, and a large gap between the concrete foundation and the wooden framing shows how much the house has moved. The photographer comments, "The foundations and brick cladding moved, but the timber wall remained in position. The gap grew to over 400mm by the time the house was demolished.

Images, UC QuakeStudies

Detail of damage to a house in Richmond. A double-brick wall has collapsed, and a gap is visible between the house and its foundation. The photographer comments, "These photos show our old house in River Rd and recovery work around Richmond and St Albans. The house and the concrete patio are now 15cm apart. The house took half the dining room's remaining bricks with it as it jumped off the foundations. It gives a good visual indication of the displacement".