Perforations adversely affect the structural response of unreinforced masonry walls (UMW) by reducing the wall’s load bearing capacity, which can cause serious structural damage. In the absence of a reliable procedure to accurately predict the load bearing capacity and stiffness of perforated masonry walls subjected to in-plane loadings, this study presents a novel approach to measure these parameters by developing simple but practical equations. In this regard, the Multi-Pier (MP) method as a numerical approach was employed along with the application of an Artificial Neural Network (ANN). The simulated responses of centrally perforated UMW by the MP method were validated utilizing full-scale experimental walls. The validated MP model was used to generate a simulated database. The simulated database includes results of analyses for 49 different configurations of perforated masonry walls and their corresponding solid masonry walls. The effect of the area and shape of the perforations on the UMW’s behavior was evaluated by the MP method. Following the outcomes of the verified MP method, the ANN is trained to develop empirical equations to accurately predict the reduction in the load bearing capacity and initial stiffness due to the perforation of UMW. The results of this study indicate that the perforations have a significant effect on the structural capacity of the UMW subjected to in-plane loadings.

Application of Artificial Neural Network to Predict Load Bearing Capacity and Stiffness of Perforated Masonry Walls

Study of shear behavior of grouted vertical joints between precast concrete wall panels under direct shear loading

A Multi-Pier MP procedure for the non-linear analysis of in-plane loaded masonry walls

Seismic retrofitting and/or the strengthening of RC columns has been a popular area of research for decades. Currently, reinforced concrete jacketing is considered as the most common technique for repairing and strengthening of deficient and/or damaged RC columns. In general, this technique is a practical solution to recover and improve the load-carrying capacity and stiffness of reinforced concrete columns in earthquake-prone countries. It is a simple method that can be applied to any column cross section for rehabilitating structural elements by encasing the old member in a stiff jacket. The importance of this approach comes from its ability to improve the load-carrying capacity, strength, and stiffness of any column section significantly without the need for experienced labor or complicated installations process. This paper summarizes and compares general conclusions of recent investigations on columns retrofitting using reinforced concrete jacketing. As a part of this study, experimental, analytical, and numerical studies were reviewed and their findings were collected and discussed.

Column repair and strengthening using RC jacketing: a brief state-of-the-art review

Evaluating the behaviour of centrally perforated unreinforced masonry walls: Applications of numerical analysis, machine learning, and stochastic methods

The present paper provides a methodology to analyse the effect of corrosion on the strength and stiffness of the slab-and-girder deck of a road bridge. A linear finite element model of a typical medium span deck of an existing bridge was developed as per the as-built drawings. The vehicular loadings were as per the recommendations of the Indian Roads Congress specifications and the design rating of the bridge. Based on the phenomenon of corrosion, a time-dependent reduction in the area of flexural reinforcement near the soffits of the girders, was considered in the model. The effects of flexural cracking, creep and spalling of concrete were incorporated in the model with non-prismatic section properties and their stage-wise variations. From the analyses of a girder section and the computational model, it was observed that due to corrosion, the allowable moment capacity of a girder falls below the demand under dead load plus the rated live load, within the target service life of the bridge. However, the effect of corrosion on the stiffness of the deck is not substantial to be accurately measured by a conventional sensor. It is recommended that the procedure adopted in the paper can be used by the practicing professionals for numerically assessing longer span decks, to have a’priori estimates of the quantities that can be measured in a field test.

A Methodology to Assess the Degradation in the Structural Response of the Deck of a Reinforced Concrete Road Bridge due to Corrosion of Reinforcing Steel

Precast concrete systems represent an efficient alternative for building construction. The behaviour of a precast system depends on connections and it should be modelled properly in the computational models for analysis and design. This study presents the modelling of connections in a wall type precast building system. A case study on a 23-storeyed building, made up of precast wall panels and slabs, to study the modelling of vertical joints in terms of shear transfer, is presented in the paper. Two computational models were investigated to find the effect of modelling the vertical joints between the wall panels, on the drifts and the generated forces in the walls. It was observed that the model, which was not considering any shear transfer through the vertical joints, tend to provide conservative results in terms of amount of steel requirement. The emulative monolithic wall system seems to be adequate in moderate seismic zones. The provisions of tie reinforcements, reinforced shear keys and dowel bars provide the required structural integrity for the precast system to avoid progressive collapse

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Analysis of precast multistoreyed building a case study

Constitutive models for plain and reinforced concrete - An overview

This paper illustrates the effect of chloride-induced corrosion in the flexural capacity of a pretensioned concrete girder in an existing girder-and-slab deck bridge. The numerical study of the time-wise variation of the flexural capacity is based on a proposed model for the loss of cross-sectional area of the prestressing strands. It was observed that almost 46% of the total area of strands can get affected due to chloride-induced corrosion of the girder, by the end of its service life. The corresponding flexural capacity of the girder gets reduced by 50% of its initial capacity.

An Assessment of the Deterioration of Flexural Capacity of a Pretensioned Concrete Girder Due to Strand Corrosion

The Rashtrapati Bhavan, the official residence of the President of India, is a Grade-I heritage structure. The reinforced concrete cantilever sunshades in this building are at a height of about 20 m above ground and span about two-kilometer along the perimeter of the building. In the late 1990s, some sunshades experienced corrosion and were repaired using polymer modified cementitious mortar. However, these repaired sunshades and others are now exhibiting severe corrosion and concrete spalling- posing a serious falling hazard for visitors and inhabitants. This paper presents a systematic evaluation of the concrete used in the sunshades and the assessment of corrosion and structural conditions of the sunshades. Concrete was found to be made of non-hydraulic lime and carbonated - indicating high probability of corrosion. Hence, about 200 sunshade locations from various parts of the building were visually and non-destructively assessed and distress-maps were developed. For this, an instrumented hammer was used on 15 test points per sunshade panel area (of about 1 × 2 m size). Based on the impulse waveform patterns, estimated strengths and visible damage, the panels were classified into distress levels of negligible, moderate and severe. About 58 to 86% of the sunshades were found to be severely damaged. Also, service level load test was conducted (upto a load of 75 kN) at a representative location, to assess the effect of corrosion on the load-deflection behaviour of the cantilever. The possible repair strategy and challenges associated with adopting conventional methods, are discussed in the paper.

Amlan K. Sengupta

Papers

A Methodology to Assess the Degradation in the Structural Response of the Deck of a Reinforced Concrete Road Bridge due to Corrosion of Reinforcing Steel

Analysis of precast multistoreyed building a case study

Constitutive models for plain and reinforced concrete - An overview

An Assessment of the Deterioration of Flexural Capacity of a Pretensioned Concrete Girder Due to Strand Corrosion

Restoration of Reinforced Lime Concrete Sunshades of a Century Old Heritage Building in New Delhi, India