Criteria for Initiation of Slide, Rock, and Slide-Rock Rigid-Body Modes

Shenton, Harry W.

doi:10.1061/(asce)0733-9399(1996)122:7(690)

Cited by 186 publications

(131 citation statements)

References 6 publications

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“…Suggestions were to restrain equipment to reduce their damage (PAHO, 2004), although researchers demonstrated that even anchored equipment get damaged, and suggest that it may be more stable if they are left free standing (Makris and Zhang, 1999). The response of equipment to earthquakes can be sliding, slide-rocking, rocking or flying (Housner, 1963) depending on their geometry, static friction and ground acceleration (Shenton III, 1996), although, some researchers believe that frequency is also another factor that affects equipment stability (Achour, 2007).…”

Section: Equipmentmentioning

confidence: 99%

Earthquake-Induced Structural and Nonstructural Damage in Hospitals

et al. 2011

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The Sichuan (China) and L'Aquila (Italy) earthquakes have again highlighted the question of our preparedness for natural hazards. Within a few seconds, an earthquake can demolish many buildings, destroy infrastructure, and kill and injure thousands of people. In order to reduce the impact of earthquakes on human life and to prepare hospitals to cope with future disasters, this paper discusses earthquake-related damage to healthcare facilities. It investigates the damage to 34 healthcare facilities in seven countries caused by nine earthquakes between 1994 and 2004, in order to determine common and specific issues. The investigation shows that structural and architectural damage tended to be different and specific to the situation, while utility supplies and equipment damage were similar in most cases and some common trends emerged.

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Section: Equipmentmentioning

confidence: 99%

Earthquake-Induced Structural and Nonstructural Damage in Hospitals

et al. 2011

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“…Prior to 1996, the mode of rigid-body motion that prevailed has been determined by comparing the available static friction to the width-to-height ratio of the block, irrespective of the magnitude of the horizontal ground acceleration. At about the same time, Scalia and Sumbatyan (1996) and, independently, Shenton (1996) indicated that, in addition to pure sliding and pure rocking, there is a slide-rock mode and its manifestation depends not only on the width-to-height ratio and the static friction coefficient but also on the magnitude of the base acceleration.…”

Section: Condition For Initiation Of Rocking Motionmentioning

confidence: 99%

“…With the system of axis shown, a positive acceleration will induce an initial negative rotation ( < 0). Adopting the notation introduced by Shenton (1996), let f x > 0 and f z > 0 be the horizontal and vertical reactions at the tip OЈ of the block. Dynamic equilibrium at this instant ( = 0) givesf…”

Section: Condition For Initiation Of Rocking Motionmentioning

confidence: 99%

Rocking Response of Free-Standing Blocks under Cycloidal Pulses

2001

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This paper examines in depth the transient rocking response of free-standing rigid blocks subjected to physically realizable trigonometric pulses. First, the expressions for the dynamic horizontal and vertical reactions at the pivot point of a rocking block are derived and it is shown that the coefficient of friction needed to sustain pure rocking motion is, in general, an increasing function of the acceleration level of the pulse. Subsequently, this paper shows that under cycloidal pulses a free-standing block can overturn with two distinct modes: (1) by exhibiting one or more impacts; and (2) without exhibiting any impact. The existence of the second mode results in a safe region that is located on the acceleration-frequency plane above the minimum overturning acceleration spectrum. The shape of this region depends on the coefficient of restitution and is sensitive to the nonlinear nature of the problem. This paper concludes that the sensitive nonlinear nature of the problem, in association with the presence of the safe region that embraces the minimum overturning acceleration spectrum, complicates further the task of estimating peak ground acceleration by only examining the geometry of free-standing objects that either overturned or survived a ground shaking.

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“…For a constant ground acceleration, the response mode of the rock shifts from pure sliding to sliding coupled with rocking, and then to pure rocking with increase in the coefficient of friction. For a rigid rectangular object placed on a rigid horizontal ground, Shenton (1996) obtained the relation between the constant horizontal ground acceleration and the coefficient of friction required to initiate rocking, sliding, and coupled rocking-sliding of the object. He observed that for a ground excitation amplitude greater than the quasi-static toppling acceleration of the object, it can undergo pure sliding only for friction coefficients below its width-to-height ratio.…”

Section: Effect Of Friction Coefficientmentioning

confidence: 99%

Toppling Analysis of the Echo Cliffs Precariously Balanced Rock

Veeraraghavan¹,

Hudnut²,

Krishnan³

2016

Bulletin of the Seismological Society of America

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Toppling analysis of a precariously balanced rock (PBR) can provide insight into the nature of ground motion that has not occurred at that location in the past and, by extension, can constrain peak ground motions for use in engineering design. Earlier approaches have targeted 2D models of the rock or modeled the rockpedestal contact using spring-damper assemblies that require recalibration for each rock. Here, a method to model PBRs in 3D is presented through a case study of the Echo Cliffs PBR. The 3D model is created from a point cloud of the rock, the pedestal, and their interface, obtained using terrestrial laser scanning. The dynamic response of the model under earthquake excitation is simulated using a rigid-body dynamics algorithm. The veracity of this approach is demonstrated through comparisons against data from shake-table experiments. Fragility maps for toppling probability of the Echo Cliffs PBR as a function of various ground-motion parameters, rock-pedestal interface friction coefficient, and excitation direction are presented. These fragility maps indicate that the toppling probability of this rock is low (less than 0.2) for peak ground acceleration (PGA) and peak ground velocity (PGV) lower than 3 m=s 2 and 0:75 m=s, respectively, suggesting that the ground-motion intensities at this location from earthquakes on nearby faults have most probably not exceeded the above-mentioned PGA and PGV during the age of the PBR. Additionally, the fragility maps generated from this methodology can also be directly coupled with existing probabilistic frameworks to obtain direct constraints on unexceeded ground motion at a PBR's location.Electronic Supplement: Text and figures describing the steps involved in the modeling of precariously balanced rock (PBR)-pedestal geometry, including dense point cloud representation and final 3D model, hazard deaggregation, and toppling probability.

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Criteria for Initiation of Slide, Rock, and Slide-Rock Rigid-Body Modes

Cited by 186 publications

References 6 publications

Earthquake-Induced Structural and Nonstructural Damage in Hospitals

Earthquake-Induced Structural and Nonstructural Damage in Hospitals

Rocking Response of Free-Standing Blocks under Cycloidal Pulses

Toppling Analysis of the Echo Cliffs Precariously Balanced Rock

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