Performance-based remaining life assessment of reinforced concrete bridge girders

M. B. Anoop,K. Balaji Rao,B. K. Raghuprasad 사단법인 한국계산역학회 2016 Computers and Concrete, An International Journal Vol.18 No.1

Performance-based remaining life assessment of reinforced concrete bridge girders subject to chloride-induced corrosion of reinforcement, is addressed in this paper. Towards this, a methodology that takes into consideration the human judgmental aspects in expert decision making regarding condition state assessment is proposed. The condition of the bridge girder is specified by the assignment of a condition state from a set of predefined condition states, considering both serviceability- and ultimate- limit states, and, the performance of the bridge girder is described using performability measure. A non-homogeneous Markov chain is used for modelling the stochastic evolution of condition state of the bridge girder with time. The thinking process of the expert in condition state assessment is modelled within a probabilistic framework using Brunswikian theory and probabilistic mental models. The remaining life is determined as the time over which the performance of the girder is above the required performance level. The usefulness of the methodology is illustrated through the remaining life assessment of a reinforced concrete T-beam bridge girder.

Wavelet analysis and enhanced damage indicators

K. Muthumani,N. Gopalakrishnan,D. Basu,B.K. Raghuprasad,N. Lakshmanan 국제구조공학회 2007 Smart Structures and Systems, An International Jou Vol.3 No.1

Wavelet transforms are the emerging signal-processing tools for damage identification and time-frequency localization. A small perturbation in a static or dynamic displacement profile could be captured using multi-resolution technique of wavelet analysis. The paper presents the wavelet analysis of damaged linear structural elements using DB4 or BIOR6.8 family of wavelets. Starting with a localized reduction of EI at the mid-span of a simply supported beam, damage modeling is done for a typical steel and reinforced concrete beam element. Rotation and curvature mode shapes are found to be the improved indicators of damage and when these are coupled with wavelet analysis, a clear picture of damage singularity emerges. In the steel beam, the damage is modeled as a rotational spring and for an RC section, moment curvature relationship is used to compute the effective EI. Wavelet analysis is performed for these damage models for displacement, rotation and curvature mode shapes as well as static deformation profiles. It is shown that all the damage indicators like displacement, slope and curvature are magnified under higher modes. A localization scheme with arbitrary location of curvature nodes within a pseudo span is developed for steady state dynamic loads, such that curvature response and damages are maximized and the scheme is numerically tested and proved.

Damage evaluation through radial basis function network based artificial neural network scheme

Lakshmanan, N.,Raghuprasad, B.K.,Muthumani, K.,Gopalakrishnan, N.,Basu, D. Techno-Press 2008 Smart Structures and Systems, An International Jou Vol.4 No.1

Seismic damage estimation through measurable dynamic characteristics

N. Lakshmanan,B. K. Raghuprasad,K. Muthumani,N. Gopalakrishnan,R. Sreekala 한국계산역학회 2007 Computers and Concrete, An International Journal Vol.4 No.3

Ductility based design of reinforced concrete structures implicitly assumes certain damage under the action of a design basis earthquake. The damage undergone by a structure needs to be quantified, so as to assess the post-seismic reparability and functionality of the structure. The paper presents an analytical method of quantification and location of seismic damage, through system identification methods. It may be noted that soft ground storied buildings are the major casualties in any earthquake and hence the example structure is a soft or weak first storied one, whose seismic response and temporal variation of damage are computed using a non-linear dynamic analysis program (IDARC) and compared with a normal structure. Time period based damage identification model is used and suitably calibrated with classic damage models. Regenerated stiffness of the three degrees of freedom model (for the three storied frame) is used to locate the damage, both on-line as well as after the seismic event. Multi resolution analysis using wavelets is also used for localized damage identification for soft storey columns.

Comparative study on damage identification from Iso-Eigen-Value-Change contours and smeared damage model

Lakshmanan, N.,Raghuprasad, B.K.,Gopalakrishnan, N.,Sreekala, R.,Rama Rao, G.V. Techno-Press 2010 Structural Engineering and Mechanics, An Int'l Jou Vol.35 No.6

The paper proposes two methodologies for damage identification from measured natural frequencies of a contiguously damaged reinforced concrete beam, idealised with distributed damage model. The first method identifies damage from Iso-Eigen-Value-Change contours, plotted between pairs of different frequencies. The performance of the method is checked for a wide variation of damage positions and extents. The method is also extended to a discrete structure in the form of a five-storied shear building and the simplicity of the method is demonstrated. The second method is through smeared damage model, where the damage is assumed constant for different segments of the beam and the lengths and centres of these segments are the known inputs. First-order perturbation method is used to derive the relevant expressions. Both these methods are based on distributed damage models and have been checked with experimental program on simply supported reinforced concrete beams, subjected to different stages of symmetric and un-symmetric damages. The results of the experiments are encouraging and show that both the methods can be adopted together in a damage identification scenario.

Damage evaluation through radial basis function network based artificial neural network scheme

N. Lakshmanan,B. K. Raghuprasad,K. Muthumani,N. Gopalakrishnan,D. Basu 국제구조공학회 2008 Smart Structures and Systems, An International Jou Vol.4 No.1

Identification of reinforced concrete beam-like structures subjected to distributed damage from experimental static measurements

N. Lakshmanan,B. K. Raghuprasad,K. Muthumani,N. Gopalakrishnan,D. Basu 사단법인 한국계산역학회 2008 Computers and Concrete, An International Journal Vol.5 No.1

Structural health monitoring of existing infrastructure is currently an important field of research, where elaborate experimental programs and advanced analytical methods are used in identifying the current state of health of critical and important structures. The paper outlines two methods of system identification of beam-like reinforced concrete structures representing bridges, through static measurements, in a distributed damage scenario. The first one is similar to the stiffness method, re-cast and the second one to flexibility method. A least square error (LSE) based solution method is used for the estimation of flexural rigidities and damages of simply supported, cantilever and propped cantilever beam from the measured deformation values. The performance of both methods in the presence of measurement errors is demonstrated. An experiment on an un-symmetrically damaged simply supported reinforced concrete beam is used to validate the developed method. A method for damage prognosis is demonstrated using a generalized, indeterminate, propped cantilever beam.

Comparative study on damage identification from Iso-Eigen-Value-Change contours and smeared damage model

N. Lakshmanan,B.K. Raghuprasad,N. Gopalakrishnan,R. Sreekala,G.V. Rama Rao 국제구조공학회 2010 Structural Engineering and Mechanics, An Int'l Jou Vol.35 No.6

The paper proposes two methodologies for damage identification from measured natural frequencies of a contiguously damaged reinforced concrete beam, idealised with distributed damage model. The first method identifies damage from Iso-Eigen-Value-Change contours, plotted between pairs of different frequencies. The performance of the method is checked for a wide variation of damage positions and extents. The method is also extended to a discrete structure in the form of a five-storied shear building and the simplicity of the method is demonstrated. The second method is through smeared damage model, where the damage is assumed constant for different segments of the beam and the lengths and centres of these segments are the known inputs. First-order perturbation method is used to derive the relevant expressions. Both these methods are based on distributed damage models and have been checked with experimental program on simply supported reinforced concrete beams, subjected to different stages of symmetric and un-symmetric damages. The results of the experiments are encouraging and show that both the methods can be adopted together in a damage identification scenario.

Wavelet analysis and enhanced damage indicators

Lakshmanan, N.,Raghuprasad, B.K.,Muthumani, K.,Gopalakrishnan, N.,Basu, D. Techno-Press 2007 Smart Structures and Systems, An International Jou Vol.3 No.1

Wavelet transforms are the emerging signal-processing tools for damage identification and time-frequency localization. A small perturbation in a static or dynamic displacement profile could be captured using multi-resolution technique of wavelet analysis. The paper presents the wavelet analysis of damaged linear structural elements using DB4 or BIOR6.8 family of wavelets. Starting with a localized reduction of EI at the mid-span of a simply supported beam, damage modeling is done for a typical steel and reinforced concrete beam element. Rotation and curvature mode shapes are found to be the improved indicators of damage and when these are coupled with wavelet analysis, a clear picture of damage singularity emerges. In the steel beam, the damage is modeled as a rotational spring and for an RC section, moment curvature relationship is used to compute the effective EI. Wavelet analysis is performed for these damage models for displacement, rotation and curvature mode shapes as well as static deformation profiles. It is shown that all the damage indicators like displacement, slope and curvature are magnified under higher modes. A localization scheme with arbitrary location of curvature nodes within a pseudo span is developed for steady state dynamic loads, such that curvature response and damages are maximized and the scheme is numerically tested and proved.