Investigation into the Effects of Foundation Uplift on Simplified Seismic Design Procedures

Harden, Chad; Hutchinson, Tara C.; Moore, Mark

doi:10.1193/1.2217757

Cited by 45 publications

(15 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Although such a restriction may appear reasonable (the inspection and rehabilitation of foundation damage after a strong earthquake is not easy), it may lead to nonconservative oversimplifications, especially in the case of strong geometric nonlinearities, such as foundation uplifting and sliding (e.g. Harden and Hutchinson 2006). Most importantly, neglecting such phenomena prohibits the exploitation of strongly non-linear energy dissipating mechanisms in defense of the superstructure in case of occurrence of ground motions larger than design.…”

Section: Introduction: the Need For A New Design Philosophymentioning

confidence: 95%

Soil failure can be used for seismic protection of structures

Anastasopoulos

Gazetas

Loli

et al. 2009

Bull Earthquake Eng

205

108

View full text Add to dashboard Cite

A new seismic design philosophy is illuminated, taking advantage of soil "failure" to protect the superstructure. Instead of over-designing the foundation to ensure that the loading stemming from the structural inertia can be "safely" transmitted onto the soil (as with conventional capacity design), and then reinforce the superstructure to avoid collapse, why not do exactly the opposite by intentionally under-designing the foundation to act as a "safety valve" ? The need for this "reversal" stems from the uncertainty in predicting the actual earthquake motion, and the necessity of developing new more rational and economically efficient earthquake protection solutions. A simple but realistic bridge structure is used as an example to illustrate the effectiveness of the new approach. Two alternatives are compared : one complying with conventional capacity design, with over-designed foundation so that plastic "hinging" develops in the superstructure; the other following the new design philosophy, with under-designed foundation, "inviting" the plastic "hinge" into the soil. Static "pushover" analyses reveal that the ductility capacity of the new design concept is an order of magnitude larger than of the conventional design: the advantage of "utilising" progressive soil failure. The seismic performance of the two alternatives is investigated through nonlinear dynamic time history analyses, using an ensemble of 29 real accelerograms. It is shown that the performance of both alternatives is totally acceptable for moderate intensity earthquakes, not exceeding the design limits. For large intensity earthquakes, exceeding the design limits, the performance of the new design scheme is proven advantageous, not only avoiding collapse but hardly suffering any inelastic structural deformation. It may however experience increased residual settlement and rotation: a price to pay that must be properly assessed in design.

show abstract

Section: Introduction: the Need For A New Design Philosophymentioning

confidence: 95%

Soil failure can be used for seismic protection of structures

Anastasopoulos

Gazetas

Loli

et al. 2009

Bull Earthquake Eng

205

108

View full text Add to dashboard Cite

show abstract

“…In fact, the defined displacement ratio in Harden et al . was conceptually a different parameter than the IDR used in seismic codes. Therefore, there is a need to study the effect of partial foundation uplift on the inelastic response of soil–structure systems.…”

Section: Introductionmentioning

confidence: 99%

“…More specifically, the effect of foundation uplift on IDRs is not addressed. To overcome this shortcoming, Harden et al [41] studied the effect of foundation uplift on simplified seismic design procedures. They concluded that provided IDRs in current standards could be highly unconservative when uplifting foundations are anticipated.…”

Section: Introductionmentioning

confidence: 99%

“…However, their study was based on the rocking behavior of rigid blocks on Winkler springs, which did not account for the flexibility and nonlinearity in the structure. In fact, the defined displacement ratio in Harden et al [41] was conceptually a different parameter than the IDR used in seismic codes. Therefore, there is a need to study the effect of partial foundation uplift on the inelastic response of soil-structure systems.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Inelastic displacement ratios for soil–structure systems allowed to uplift

Ghannad

Jafarieh

2014

Earthq Engng Struct Dyn

View full text Add to dashboard Cite

SUMMARYThe simultaneous effects of soil–structure interaction, foundation uplift and inelastic behavior of the superstructure on total displacement response of soil–structure systems are investigated. The superstructure is modeled as an equivalent single‐degree‐of‐freedom system with bilinear behavior mounted on a rigid foundation resting on distributed tensionless Winkler springs and dampers. It is well known that the behavior of soil–structure systems can be well described using a limited number of nondimensional parameters. Here, by introducing two new parameters, the concept is extended to inelastic soil–structure systems in which the foundation is allowed to uplift. An extensive parametric study is conducted for a wide range of the key parameters through nonlinear time history analyses. It is shown that while uplifting soil–structure systems experience excessive displacements, in comparison with systems that are not allowed to uplift, ductility demand in the superstructure generally decreases owing to foundation uplift. A new inelastic displacement ratio (IDR) is proposed in conjunction with a nonlinear static analysis of uplifting soil–structure systems. Simplified expressions are also provided to estimate the proposed IDR. Copyright © 2014 John Wiley & Sons, Ltd.

show abstract

“…Non-linear soil-foundation-structure response is simulated by means of (a) Winkler-based models that capture the settlement-rotation response of the footing Nakaki and Hart, 1987;El Naggar, 2003, 2007;Chen and Lai, 2003;Houlsby et al, 2005;Harden and Hutchinson, 2006;Raychowdhury and Hutchinson, 2009); (b) sophisticated macro-element models, where the entire soil-foundation system is replaced by a single element that describes the generalized force-displacement behavior of the foundation (Nova and Montrasio, 1991;Paolucci, 1997;Pedretti, 1998;Crémer, 2001;Crémer et al, 2001;Le Pape and Sieffert, 2001;Grange et al, 2008;Chatzigogos et al, 2009Chatzigogos et al, , 2011; and (c) finite elements (or finite differences), modeling the superstructure, the foundation, and the soil in detail (Tan, 1990;Butterfield and Gottardi, 1995;Taiebat and Carter, 2000;Gourvenec, 2007;Anastastasopoulos et al, 2010b;Anastasopoulos et al, 2011). Physical modeling has also been applied to experimentally simulate non-linear soil-foundation-structure response, by means of (a) large-scale dynamic and cyclic pushover testing, focusing on non-linear soil-foundation response (Negro et al, 2000;Faccioli et al, 2001;Antonellis et al, 2015); (b) centrifuge model testing, also taking account of non-linear superstructure response (Kutter et al, 2003;Gajan et al, 2005;Kutter, 2008, 2009); and (c) reduced-scale cyclic pushover and shaking table testing Shirato et al, 2008;Drosos et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

Performance of Rocking Systems on Shallow Improved Sand: Shaking Table Testing

Tsatsis

Anastasopoulos

2015

Front. Built Environ.

View full text Add to dashboard Cite

Recent studies have highlighted the potential benefits of inelastic foundation response during seismic shaking. According to an emerging seismic design scheme, termed rocking isolation, the foundation is intentionally under-designed to promote rocking and limit the inertia transmitted to the structure. Such reversal of capacity design may improve the seismic performance, drastically increasing the safety margins. However, the benefit comes at the expense of permanent settlement and rotation, which may threaten postearthquake functionality. Such undesired deformation can be maintained within tolerable limits, provided that the safety factor against vertical loading FS V is adequately large. In such a case, the response is uplifting dominated and the accumulation of settlement can be limited. However, this is not always feasible as the soil properties may not be ideal. Shallow soil improvement may offer a viable solution and is therefore worth investigating. Its efficiency is related to the nature of rocking, which tends to mobilize a shallow stress bulb. To this end, a series of shaking table tests are conducted, using an idealized slender bridge pier as conceptual prototype. Two systems are studied, both lying on a square foundation of width B. The first corresponds to a lightly loaded and the second to a heavily loaded structure. The two systems are first tested on poor and ideal soil conditions to demonstrate the necessity for soil improvement. Then, the efficiency of shallow soil improvement is studied by investigating their performance on soil crusts of depth z/B = 0.5 and 1. It is shown that a z/B = 1 dense sand crust is enough to achieve practically the same performance with the ideal case of dense sand. A shallower z/B = 0.5 improvement layer may also be considered, depending on design requirements. The efficiency of the soil improvement is ameliorated with the increase of rotation amplitude, and with the number of the cycles of the seismic motion.

show abstract

Investigation into the Effects of Foundation Uplift on Simplified Seismic Design Procedures

Cited by 45 publications

References 21 publications

Soil failure can be used for seismic protection of structures

Soil failure can be used for seismic protection of structures

Inelastic displacement ratios for soil–structure systems allowed to uplift

Performance of Rocking Systems on Shallow Improved Sand: Shaking Table Testing

Contact Info

Product

Resources

About