Naveen Kwatra

Damage Detection for Framed RCC Buildings using ANN Modeling

A structure is evaluated, after an earthquake, to find out whether it is usable or requires repair and retrofitting. The natural time period, damping, and mode shape are the primary dynamic characteristics of any structure that is related to seismic forces during an earthquake event. Periodic monitoring using vibration measurements is one of the most effective nondestructive methods to identify the damage level. A significant deviation in natural frequencies or damping ratios from the undamaged states indicates the possible occurrence of damage. In the present study, the dynamic characteristics of a 2D rigid frame of a reinforced concrete building are obtained analytically under different levels of damage. Further, using an artificial neural network (ANN) model the authors have developed a correlation between the damage in the frame of the reinforced concrete building with its known dynamic characteristics. Use of such correlations for evaluating the health status of the buildings has been discussed.

Health monitoring of RCC building model experimentally and its analytical validation

Purpose – The need for structural health monitoring systems is continuously growing to maintain existing civil infrastructure. For the purpose of assuring seismic safety, it is necessary to monitor the damage for its occurrence, its location and the extent of damage. Information on the damage may be utilized to make decisions on maintenance and structural safety of existing buildings, rapid evaluation of condition of damaged structure after future earthquakes, estimation of residual life of structures, feasibility of repair and retrofitting of structures, partial replacement or demolition of structure and financial planning for renovation and rehabilitation. The purpose of this paper is to present a four‐level scheme of damage detection.Design/methodology/approach – In the first stage of the four‐level scheme, finite element model has been developed and dynamic parameters are calculated. In the second stage, change in the dynamic properties of farmed reinforced concrete building model is identified from v...

On the optimization of fiber Bragg grating optical sensor using genetic algorithm to monitor the strain of civil structure with high sensitivity

Abstract. The effect of strain on civil structures is experimentally studied using fiber Bragg grating (FBG). The genetic algorithm is implemented to optimize the multiple parameters (Poisson’s ratio, photoelastic coefficient P11, and photoelastic coefficient P12) of the proposed sensor. The optimized results helped in increasing the sensitivity in terms of wavelength shift. It is observed that the proposed FBG provides maximum wavelength shift of 38.16 nm with Poisson’s ratio of 1.94, photoelastic coefficient P11 of 1.994, and photoelastic coefficient P12 of 1.8103.

Topological disorder of microstructure in fiber-reinforced polymer composites: Diffusion response

Influence of microarchitectural fiber matrix arrangement in representative volume element is studied to assess the effect of mass diffusion in the fiber-reinforced polymer composites. A novel approach has been proposed to illustrate the quantitative definition of the representative volume element heterogeneity using topological descriptor of clustering. Average fiber center distance from the fixed representative volume element center is described to compute the clustering in different representative volume elements, followed by finite element method simulation to model and visualize two-dimensional microstructures of fiber-reinforced matrix composites with moisture boundary conditions. The suggested topology descriptor shows good correlation with diffusion response in relation to saturation time, whereas a fair degree of correlation was observed for mass accumulation and mass flux characteristics. The results indicate that microstructural heterogeneity has a strong influence on typical moisture diffusion characteristics and hence, an overall diffusion-induced damage. The observations should serve as a clue to design the fiber-reinforced polymer composites with the moisture barrier properties.

Behavior of Shallow-Beam Supported Reinforced Concrete Rectangular Slabs: Analytical and Experimental Investigations

A design equation useful for proportioning the rectangular reinforced concrete slab cast monolithic with the equally spaced shallow in-built beams and resting over the simple supports on its outer boundaries is presented herein. The use of these beams becomes mandatory in buildings due to some architectural constraints. Full-scale slabs designed using the proposed design equations are experimentally validated. The actual crack pattern at the collapse load, for the two and three-panel slabs tested in the laboratory, was found to be in good agreement with the analytical results. A non-dimensional parameter, λ (= moment of resistance of beam/moment of resistance of beam required for the simultaneous formation of global and local collapse mechanism) has been proposed to distinguish the nature of shallow beams. Test slabs designed using the λ-value less than unity failed following a global-collapse mechanism with a load factor of more than 1.40. However, these slabs show more deflection at the design load than the permissible values but selecting a highest possible value of the beam depth satisfying both the serviceability criterion as well as the span/depth ratio of the shallow beam can reduce the actual deflection of the slab system under the design load. It is suggested that the actual slab-beam system with shallow beams should never be proportioned with λ-value more than unity as it leads to failure of the slab in a local-collapse mechanism with a reduced load factor.

Use of vibration measurements in health monitoring of reinforced concrete buildings

Purpose – In developing countries such as India, it is common practice to use low‐quality building materials, the strength of such materials reduce with time, which affects the lifespan of buildings. The wind, rain, seepage, and surface runoff are other key factors responsible for building damage and exterior degradation. The increasing industrial growth in and around urban areas is responsible for increasing industrial and anthropogenic emissions that are found to accelerate degradation of the buildings that affects their physical appearance. In an area prone to natural hazards such as earthquakes, volcanoes, subsidence, floods, lightning, tornados, and cyclone/hurricanes, huge amounts of damage throughout the globe has been experienced. For the purpose of assuring safety due to natural hazards, it is necessary to monitor the damage for its existence, its location and extent. Undetected damage may potentially lead to risk of vulnerability caused by natural hazards and eventually to catastrophic failure. ...

Monitoring of RCC structures affected by earthquakes

A large number of civil structures were designed according to old seismic code that do not meet current safety standards. They may also suffer from ageing and deterioration induced by environmental factors such as corrosive agents and earthquakes. A methodology has been developed to assess the current state of existing structures using vibration-based structural health monitoring. This technique has attracted civil engineering community recently. Vibration-based, non-destructive damage identification uses changes in the dynamic characteristics of the structure to identify damage. Full or large-scale dynamic tests of structural specimens provide unique opportunities to evaluate and validate these methods under realistic conditions, i.e. with the same level of measurement noise, estimation uncertainty and modelling errors, which are observed as in situ conditions. In this paper, we have studied the behaviour of existing structures and the models casted in the lab. Experimental determination of the dynamic characteristics of the model of RCC building under different levels of damage has been used to develop correlation between damage in the models of RCC buildings with its known dynamic characteristics using artificial neural network models.

Role of Landscape Elements in Ameliorating Adverse Pedestrian Level Winds in the Vicinity of Tall Buildings

Tall buildings cater to the need for increased workspace with a reduced footprint, enhance the skyline, and image and increase the prestige of a city. Tall buildings also tend to intercept upper level high velocity winds and deflect them down to ground level, giving rise to conditions that could be unpleasant or even dangerous to pedestrians. Such accelerated winds also reduce the appeal of plazas, outdoor cafes, parks and pedestrian access-ways. Vertically accelerated downward wind flows can be mitigated with the help of architectural elements like podia or, canopies. Horizontally accelerated flows are best ameliorated with soft and hard landscape elements such as trees, shrubs and porous fences. This paper reports results of wind tunnel investigations that have been carried with the objective of assessing the role of landscape elements in moderating the pedestrian level wind environment in the vicinity of tall buildings. The tests have been carried out in the de Bray boundary layer wind tunnel at the University of Auckland on a representative model of a tall building suburb in New Delhi using the erosion technique enhanced with an image processing system. The results of the tests have brought out the effectiveness of landscape elements such as trees and porous fences in mitigating adverse horizontal winds in the vicinity of tall buildings.

Development of Pavement Distress Deterioration Prediction Models for Urban Road Network Using Genetic Programming

The objective of the present study is to develop models to predict the deterioration of pavement distress of the urban road network. Genetic programming (GP) has been used to develop five models for the prediction of pavement distress: Model 1 for the cracking progression, Model 2 for the ravelling progression, Model 3 for the pothole progression, Model 4 for the rutting progression, and Model 5 for the roughness progression. The data have been collected from the roads of Patiala City, Punjab, India; during the years 2012–2015, the network of 16 roads have been selected for the data collection purposes. The data have been divided into two sets, that is, training dataset (data collected during the years 2012 and 2013) and validation dataset (data collected during the years 2014 and 2015). The two fitness functions have been used for the evaluation of the models, that is, coefficient of determination (R2) and root mean square error (RMSE), and it is inferred that GP models predict with high accuracy for pavement distress and help the decision makers for adequate and timely fund allocations for preservation of the urban road network.

Application of Genetic Programming for Determination of Wind Loads on Tall Buildings

Tall building can vibrate in both the directions of Along wind and Across wind caused by the flow of wind. Modern Tall buildings designed to satisfy lateral drift requirements, still may oscillate excessively during wind storm. These oscillations can cause some threats to the tall building as buildings with more and more height becomes more vulnerable to oscillate at high speed winds. Sometimes these oscillations may even cause discomfort to the occupants even if it is not in a threatening position for the structural damage. So an accurate assessment of building motion is an essential prerequisite for serviceability. The wind response on tall buildings is generally estimated either through wind tunnel testing or using analytical approach as mentioned in IS8751987, Part-3. However, both these methods are very cumbersome and time consuming. Therefore, in this paper an attempt has been made to estimate the wind response on tall buildings using Genetic Programming in the along wind direction for Long After Body and Short After Body. The database has been developed using the analytical approach as given in IS875-1987, Part-3. The building height, plan dimensions, design wind speed, gust factor and base moment have been used as the parameters for the development of the equations. The Gust Factor and Base Moment thus obtained from Genetic Programming have been thus compared with the analytical values.