EXPERIMENTAL MULTI-LEVEL SEISMIC PERFORMANCE ASSESSMENT OF 3D RC FRAME DESIGNED FOR DAMAGE AVOIDANCE
Author: Brendon A Bradley1* , Rajesh P Dhakal1 , John B Mander1 , Louman Li1 . 1 Department of Civil Engineering, University of Canterbury, , New Zealand | Size: 591 KB | Format:PDF | Quality:Unspecified | pages: 33
This paper experimentally investigates the application of damage avoidance design (DAD) philosophy to moment resisting frames with particular emphasis on detailing of rocking interfaces. An 80% scale 3-dimensional rocking beam-column joint sub-assembly designed and detailed based on damage avoidance principles is constructed and tested.
Incremental dynamic analysis (IDA) is used to select ground motion records to be applied to the sub-assembly to conduct a multi-level seismic performance assessment (MSPA).
Analyses are conducted to obtain displacement demands due to the selected near and medium
field ground motions that represent different levels of seismic hazard. Thus predicted
displacement time histories are applied to the sub-assembly to conduct quasi-earthquake displacement (QED) tests. The sub-assembly performed well reaching drifts up to 4.7% with only minor spalling occurring at rocking beam interfaces and minor flexural cracks in beams.
Yielding of post-tensioning tendons occurred, but the sub-assembly did not collapse. The externally attached energy dissipaters provided large hysteretic dissipation during large drift
cycles. The sub-assembly satisfied all three seismic performance requirements, thereby verifying the superior performance of the DAD philosophy.
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Effect of floor slabs on the seismic performance of RC frames
Author: S.M Ahmed & U. Gunasekaran Anna University, Chennai, India. | Size: 1.3 MB | Format:PDF | Quality:Unspecified | Year: 2014 | pages: 13
ABSTRACT: In monolithic reinforced concrete structures, portions of the floor slabs act as flanges to the girders, thereby increasing the strength and stiffness of the girders. The question of how much the slab contributes to the lateral strength is very important for the design of structures; therefore this paper describes the effect of slabs at the joints in moment-frame structures subjected to large seismic deformations. A simple method to model a beam-column joint subassembly including the effects of both beam growth/elongation and the floor slab is introduced. The model is developed by establishing the slab crack pattern at the joint and the state of strain in the slab bars. The results of the models excluding and including slab effects are verified with the experiential test results. The joint model is incorporated in the nonlinear dynamic analyses for a five-storey and four-bay moment frame structure. Two different ground motions (El-Centro 1940 and Northridge 1994) are considered for the analyses. The results show that the cyclic inelastic bending causes the beams to increase in length and the floor slabs significantly restrain this phenomenon and cause the columns to displace by different amounts, changing the distribution of shear among the columns, and increasing the base shear of the columns. These additional forces may lead to a failure mechanism different from the anticipated one. The effect of floor slab including beam elongation effect is thus illustrated for a two dimensional moment frame building and this model works well for the lateral load analysis of frames.
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SEISMIC PERFORMANCE OF HIGH-ST RENGTH-CONCRETE HOLLOW BRIDGE PIERS UNDER MULTI-DIRECTIONAL LOADING
Author: R. Burgueño , X. Liu and E. M. Hines | Size: 1.2 MB | Format:PDF | Quality:Unspecified | pages: 11
High-strength-concrete (HSC) offers the potential of transforming the design of structural elements under seismic loads by harnessing the enhanced capacities associated with axial load, flexural compression zone confinement and web shear crushing of wall webs. However, the limits to which such performance features can be reliably taken into account require careful exploration, in particular, when considering multi-directional seismic loads. Of the noted aspects enhanced by HSC, that associated with the inelastic web crushing capacity of hollow rectangular bridge piers is still unresolved in view of the guidance of capacity design philosophy which suppresses possible shear failures. Nonetheless, recent research has demonstrated that structural walls can exhibit dependable ductile behavior before being ultimately limited by web crushing shear failures. And that this inelastic capacity can be further improved with HSC. However, the threedensional demands and damage accumulation of HSC structural walls under multi-directional loading needs to be properly evaluated to establish reliable nlimits that satisfy the noted inelastic performance requirements.
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Seismic Performance of Strength Degraded Structures
Author: Rupali S Bhamare , Bidur Kafle , Nelson Lam , John Wilson , Emad Gad | Size: 423 KB | Format:PDF | Quality:Unspecified | pages: 11
ABSTRACT:
Traditionally, performance assessment of a structure is based on trading off strength demand with
ductility demand. In high seismicity region, the design provisions are based on the concept of conservation
of energy; such guidelines (FEMA 273) recommend a very low drift capacity for strength
degraded structures. Furthermore, the application of these guidelines, results in most of the strength
degraded structures deemed unsafe when subjected to earthquake excitations in low and moderate
seismic regions. This paper presents results of nonlinear time history analyses (THA) for such
strength degraded structures for a range of near-field and far-field earthquake scenarios of different
M-R combinations. Fragility curves defining probability of failure of structures have been developed.
The insensitivity of the probability of failure of the URM wall on its height (i.e. vertical span
length) is an interesting finding in this study. Also, the extent of strength degradation in an unreinforced
masonry wall is not shown to have increased its probability of failure.
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Author: Paul Ndumbaro, Peter Broughton | Size: 12 MB | Format:PDF | Quality:Scanner | Publisher: Thomas Telford Publishing | Year: 1995 | pages: 98 | ISBN: 978-0727720085
This book provides sound practical guidance on cable and catenary structural systems. In a clear and concise manner it deals with the complicated subject of exact formulation in the theoretical treatment of these systems when subjected to large charges in geometry.
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Abstract. The applicability of nonlinear static procedures for estimating seismic demands of typical regular RC moment-resisting frames is evaluated. This work, conducted within the framework of the ATC-76-6 project, shows the degree to which nonlinear static methods can characterize global and
local response demands vis-à-vis those determined by nonlinear dynamic analysis for three RC mo-ment frame buildings. The response quantities (engineering demand parameters) considered are peak story displacements, story drifts, story shears and floor overturning moments. The single-mode push-
over methods evaluated include the N2 and the ASCE-41 coefficient methods. Multi-modal pushover methods such as the Modal Pushover Analysis and the Consecutive Modal Pushover method also were evaluated. The results indicate that the relatively good performance of the single-mode methods observed for low-rise buildings rapidly deteriorates as the number of stories increases. The multi- mode techniques generally extend the range of applicability of pushover methods, but at the cost of additional computation and without ensuring reliability of the results.
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SIMPLIFIED P-y RELATIONSHIPS FOR MODELING EMBANKMENT- ABUTMENT SYSTEMS OF TYPICAL CALIFORNIA BRIDGES
Author: SEXTOS, Anastasios , MACKIE, Kevin , STOJADINOVIC , Bozidar and TASKARI, Olympia | Size: 1.4 MB | Format:PDF | Quality:Unspecified | Publisher: The 14 World Conference on Earthquake Engineering October 12-17, 2008, Beijing, China | Year: 2008 | pages: 08
The flexibility οf the embankment-abutment stiffness has been found to drastically effect the seismic response
of the entire bridge, typically depending on the intensity of earthquake ground motion, but also on the
geometrical and mechanical properties of embankment-abutment system. Consequently, significant effort has
been made to incorporate the nonlinear behavior of the lateral support of the deck primarily through inelastic
static (pushover) analysis. However, the difficulties in modeling the nonlinear behavior of soil as well as the
computationally demanding three-dimensional geometry often lead to the disregard of some sources of
nonlinearity such as those associated with the foundation soil and the boundary conditions at bridge abutments.
Along these lines, the scope of this paper is to model and study the nonlinear response of six typical Californian
abutment-embankment systems to derive specific force-deflection (i.e., P-y) relationships as a function of
foundation soil properties, abutment type, and embankment geometry within the framework of an alternative
simplified method proposed by Kappos et al. (2007). Comparative assessment of the current Caltrans guidelines
is also performed and design recommendations are made.
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513 Seismic damage assessment for six RC bridges in the Veneto region (NE Italy)
Author: P. FRANCHETTI , M. GRENDENE , D. SLEJKO and C. MODENA | Size: 3 MB | Format:PDF | Quality:Unspecified | Publisher: Bollettino di Geofisica Teorica ed Applicata Vol. 49, n. 3-4, pp. 513-531; September-December 2008 | Year: 2008 | pages: 19
Seismic damage on six bridges in the Veneto region (NE Italy) is estimated by means of a probabilistic approach for seismic hazard assessment and by constructing the specific fragility curve for each bridge. Construction of fragility curves is based on
various approaches from literature. With the application of the best-performing approach on the six bridges a comparative preliminary evaluation of the expected damage on the bridges was done. However, as the methodology is general, it could easily be applied to bridges of an extensive number of road networks.
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This book provides senior undergraduate students, master students and structural engineers who do not have a background in the field with core knowledge of structural earthquake engineering that will be invaluable in their professional lives. The basics of seismotectonics, including the causes, magnitude, and intensity of earthquakes, are first explained. Then the book introduces basic elements of seismic hazard analysis and presents the concept of a seismic hazard map for use in seismic design. Subsequent chapters cover key aspects of the response analysis of simple systems and building structures to earthquake ground motions, design spectrum, the adoption of seismic analysis procedures in seismic design codes, seismic design principles and seismic design of reinforced concrete structures. Helpful worked examples on seismic analysis of linear, nonlinear and base isolated buildings, earthquake-resistant design of frame and frame-shear wall systems are included, most of which can be solved using a hand calculator.
Features:
-Covers the seismic hazard, the basics of seismotectonics, and the fundamentals of earthquake engineering
-Meets the future professional needs of senior undergraduate students by explaining the principles of earthquake-resistant design
-Includes useful sample problems on earthquake-resistant design of frame and frame-shear wall systems
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