Flexure-controlled ultimate deformations of members with continuous or lap-spliced bars
TL;DR: In this paper, a databank of cyclic or monotonic tests to flexure-controlled failure is used to develop/calibrate models for the curvature and chord rotation of reinforced concrete members at flexure controlled ultimate conditions.
Abstract: A databank of cyclic or monotonic tests to flexure-controlled failure is used to develop/calibrate models for the curvature and the chord rotation of reinforced concrete members at flexure-controlled ultimate conditions – at a 20% post-ultimate strength drop in lateral force resistance – under monotonic or cyclic loading. Models are developed for beams, rectangular columns or walls and members of T-, H-, U- or hollow rectangular section, with or without detailing for earthquake resistance and with continuous longitudinal bars. The models employ simple, explicit expressions for practical application without moment–curvature analysis and are on the safe side for biaxial loading. They are extended to members with longitudinal bars lap-spliced in the plastic hinge region.
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TL;DR: In this paper, a Bayesian take on the cloud analysis is presented, which manages to take into account both record-to-record variability and other sources of uncertainty related to structural modelling.
Abstract: Cloud Analysis is based on simple regression in the logarithmic space of structural response versus seismic intensity for a set of registered records. A Bayesian take on the Cloud Analysis, presented herein, manages to take into account both record-to-record variability and other sources of uncertainty related to structural modelling. First, the structural response to a suite of ground motions, applied to different realizations of the structural model generated through a standard Monte Carlo, is obtained. The resulting suite of structural response is going to be used as “data” in order to update the joint probability distribution function for the two regression parameters and the conditional logarithmic standard deviation. In the next stage, large-sample MC simulation based on the updated joint probability distribution is used to generate a set of plausible fragility curves. The robust fragility is estimated as the average of the generated fragility curves. The dispersion in the robust fragility is estimated as the variance of the plausible fragility curves generated. The plus/minus one standard deviation confidence interval for the robust fragility depends on the size of the sample of “data” employed. Application of the Bayesian Cloud procedure for an existing RC frame designed only for gravity-loading demonstrates the effect of structural modelling uncertainties, such as the uncertainties in component capacities and those related to construction details. Moreover, a comparison of the resulting robust fragility curves with fragility curves obtained based on the Incremental Dynamic Analysis shows a significant dependence on both the structural performance measure adopted and the selection of the records.
178 citations
TL;DR: In this paper, the authors developed and calibrated models for the moment, the chord rotation and the secant stiffness at flexural yielding of reinforced concrete beams, rectangular columns or walls and members of T-, H-, U- or hollow rectangular section, on the basis of a databank of tests on members with continuous bars.
Abstract: Models are developed and calibrated for the moment, the chord rotation and the secant stiffness at flexural yielding of reinforced concrete beams, rectangular columns or walls and members of T-, H-, U- or hollow rectangular section, on the basis of a databank of tests on members with continuous bars. Criteria are developed for the identification of adverse shear effects on the yield moment. The models apply only to members whose yield moment is not reduced by shear effects. They employ simple, explicit expressions suitable for practical application without moment–curvature analysis. They are extended to members with bars lap-spliced starting at the end section. The effect of biaxial loading on member yielding is examined. Most of the models have been adopted in Eurocode 8, Part 3.
95 citations
TL;DR: In this article, the confinement effect of fiber-reinforced polymer (FRP) jacket on the plastic hinge length of square RC columns is studied through experimental testing and analytical study, and the results show that compared with unconfined RC columns, FRP jacketing increases the hinge length when the confinement level is low, but reduces it when the conflating level is high.
Abstract: The confinement effect of fiber-reinforced polymer (FRP) jacket on the plastic hinge length of square RC columns is studied through experimental testing and analytical study. Seven half-scale RC square columns with different confinement ratios were tested. The strain of longitudinal reinforcement bars and the extent of yielding were measured by strain gauges mounted inside the reinforcement bars. The variation of the strain field of the external column face was recorded continuously by digital image correlation (DIC) during a test. More rational approaches of data analysis are used for identification of plastic hinge length from measured strain fields. The obtained results show that compared with unconfined RC columns, FRP jacketing increases the plastic hinge length when the confinement level is low, but reduces it when the confinement level is high. The analytical study shows that all existing models of plastic hinge length are inadequate in one way or another because no model includes all important factors. The proposed model can correctly capture the trends but it needs to be further improved for accuracy when more data are available.
85 citations
TL;DR: In this article, a new methodology for the development of bridge-specific fragility curves is proposed with a view to improving the reliability of loss assessment in road networks and prioritising retrofit of the bridge stock.
Abstract: A new methodology for the development of bridge-specific fragility curves is proposed with a view to improving the reliability of loss assessment in road networks and prioritising retrofit of the bridge stock. The key features of the proposed methodology are the explicit definition of critical limit state thresholds for individual bridge components, with consideration of the effect of varying geometry, material properties, reinforcement and loading patterns on the component capacity; the methodology also includes the quantification of uncertainty in capacity, demand and damage state definition. Advanced analysis methods and tools (nonlinear static analysis and incremental dynamic response history analysis) are used for bridge component capacity and demand estimation, while reduced sampling techniques are used for uncertainty treatment. Whereas uncertainty in both capacity and demand is estimated from nonlinear analysis of detailed inelastic models, in practical application to bridge stocks, the demand is estimated through a standard response spectrum analysis of a simplified elastic model of the bridge. The simplified methodology can be efficiently applied to a large number of bridges (with different characteristics) within a road network, by means of an ad hoc developed software involving the use of a generic (elastic) bridge model, which derives bridge-specific fragility curves.
79 citations
Cites methods from "Flexure-controlled ultimate deforma..."
...For this case, a MATLAB-based software was developed for the implementation of the previously described methodology using the simplified elastic model and response spectrum analysis for the derivation of bridge-specific fragility curves, summarised in Figure 14....
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...For each pier type (and for both principal axes in non-symmetric cross-sections) from analysis that also considers P-delta effects, the displacement is recorded of the cantilever tip at the instant that the deformation of the plastic hinge exceeds limit state thresholds (φ1, φ2, φ3, φ4 in Table II); this is done using ad hoc software developed in MATLAB [31] for batch analysis....
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...For each pier type (and for both principal axes in non-symmetric cross-sections) from analysis that also considers P-delta effects, the displacement is recorded of the cantilever tip at the instant that the deformation of the plastic hinge exceeds limit state thresholds (ϕ1, ϕ2, ϕ3, ϕ4 in Table II); this is done using ad hoc software developed in MATLAB [31] for batch analysis....
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TL;DR: In this paper, a simplified analytical method for the seismic fragility assessment of reinforced concrete buildings at large scale is presented, based on a simulated design procedure to define the structural model and on non-linear static analysis of a simplified structural model based on Shear-Type assumption to evaluate seismic capacity.
67 citations
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TL;DR: In this paper, the authors developed expressions for the ultimate deformation capacity and for the deformation at yielding of reinforced concrete (RC) members in terms of their geometric and mechanical characteristics, which are essential for the application of displacement-based procedures for earthquake resistant design of new RC structures and for seismic evaluation of old ones.
Abstract: The inelastic deformation capacity of reinforced concrete (RC) members is important for the resistance of RC structures to imposed deformations, and especially so for seismic loads as earthquake-resistant design relies on the ability of RC members to develop (cyclic) deformations well beyond elastic limits without significant loss of load-carrying capacity. This study develops expressions for the ultimate deformation capacity and for the deformation at yielding of RC members in terms of their geometric and mechanical characteristics. Such expressions are essential for the application of displacement-based procedures for earthquake-resistant design of new RC structures and for seismic evaluation of old ones. They are also essential for a realistic estimation of the effective elastic stiffness of cracked RC members and structures, which is important for the calculation of seismic force and deformation demands.
559 citations