Papers by Keyword: Retrofitting

Abstract: Masonry existing buildings are subjected to significant structural damages when seismic events occur. Over the last decades, innovative techniques like composite materials based on inorganic mortar (FRCM – Fiber Reinforced Cementitious Matrices) have emerged as attractive solutions for the strengthening of civil structures. FRCM shows better compatibility with masonry substrates with respect to Fiber Reinforced Polymers. The effectiveness of FRCM reinforcement systems relies on the composite-substrate bond behavior which is affected by many parameters, leading to different failure mechanisms. Although numerous studies investigate the FRCM-substrate bond, few attentions have been paid to the study of fiber grid-matrix interface behavior. In this study, the preliminary results of a wider experimental campaign aimed at investigating the interface behavior between fiber and mortar accounting for the contribution of transversal grid wires are presented. Different typologies of fiber and mortar were tested and the results are compared and discussed.

Abstract: This paper presents a study (experimentally) for strengthening reinforced concrete (RC) beams with Near-Surface-Mounted (NSM) technique. The use of this technique with CFRP strips or rebars is an efficient technology for increasing the strength for flexure and shear or for repairing damaged reinforced concrete (RC) members. The objective of this research is to study, experimentally, RC beams either repaired or strengthened with NSM CFRP strips and follow their flexural behavior and failure modes. NSM-CFRP strips were used to strengthen three RC beam specimens, one of them was initially strengthened and tested up to failure. Four beam specimens have been initially subjected to preloading to 50% and 80% of ultimate load. Two of the specimens were either repaired or strengthened with NSM-CFRP strips. All the repaired/strengthened pre-damaged beams have been tested up to failure by using compression-testing machine. An appropriate-scale model was adopted. All the specimens have a cross-sectional dimension of 150 mm with an effective span of 110 mm. Depends on the experimental results, a better performance of the strengthened concrete specimens was obtained in both strength and serviceability. As a comparison with the control beam specimen, all the repaired specimens show a very good increase of about 40% in the load-carrying capacity and a high improvement in resistance to cracking of about 120% in NSM. On the other hand, the test results of NSM CFRP-strengthened concrete specimens with a preloading of 50% and 80% of the ultimate load show an increase of about 9% to 20% in the load-carrying capacity, for 50% and 80% pre-loading, respectively an improvement in deflection of about 2% to 27% in NSM, for 80% and 50% pre-loading, respectively.

Abstract: The mechanical properties of masonry structural members strengthened by FRP (Fiber Reinforced Polymer) are affected by the bond strength of the reinforcement interface, in addition to the strength of the material FRP itself. This project is aimed at the new technology of Sprayed Fiber Reinforced Polymer Composites (SFRP), which is currently attracting attention. The bond strength between SFRP layer and masonry surface under high-humidity condition during strengthening construction and dry-wet cycle conditions after reinforcement were studied by experimental method. Different masonry substrates and different reinforcement methods were set as the test parameters. It is concluded that, compared with the currently used GFRP (Glass Fiber Reinforced Polymer) sheets reinforcement method, the SFRP reinforcement method has an significant improvement in the bond strength and the durability.

Abstract: This paper illustrates the results of the activities of analysis and structural assessment of the Assumption of the Virgin Mary chapel, in Prague. The chapel, an oval-shaped building covered with a dome, was built at the end 16th century and can be considered the last example of renaissance architecture and at the same time the first example of baroque architecture in Prague: it is a significant testimony of the close connection between local artists and their Italian teachers. The building closed to visitors during the last decades for the presence of some structural damages and because severely degraded due to lack of maintenance, was reopened in the 2017 after a notable restoration process. This paper gives attention to the interdisciplinary approach used to diagnosis and structural assessment of the chapel, based on the activities of the “knowledge path,” the subsequent structural analysis and the intervention design. Particular attention was paid to the contribution of the historical review, geometric laser scanner survey and mechanical characterization of the structural materials. All these steps result necessary to identify potential vulnerabilities and to enable the understanding of the effective structural models, also in view of proposing adequate retrofit solutions. A numerical model of the chapel was prepared and calibrated. Finally, the structural assessment for the vertical and seismic loading was performed.

Abstract: The introduction of wide range of novel raw materials and composites are tuning exceptionally the construction industry on its head. The recent research trends majorly intensified on hybrid concept using the varied materials collectively. This study primarily aims at experimentally investigating the response of concrete exterior beam column joint with Hybrid Reinforcement Technique (HRT) for reverse cyclic load conditions. The on-site fabricated, Hand Layup Carbon Fibre Reinforced Polymer (CFRP-HL) stirrups and the conventional steel main reinforcements form a hybrid reinforcement system in this study. The on-site constructed CFRP-HL reinforcement serves as a substitute for pre-fabricated CFRP rebars which has limitations and inflexibility in adapting the construction alterations. In total six types of specimens, a couple of test specimens are strengthened with HRT and another with external bond CFRP fibre wrap. In the remaining three specimens, one with non-conventional steel detailing and a couple of conventional joints that are designed according to IS 456:2000 and IS 13920:1993 respectively. In addition, the influence of varied spacing of stirrups in specimens is studied separately. Further, the test results on overall strength, stiffness, load deflection characteristics, dissipated energy and ductility of test specimens is evaluated and discussed. The use of CFRP-HL with steel as hybrid combination enables to comprehend the benefit from their distinctive characteristics. This proposal strongly improves the greater flexibility of using CFRP-HL in field as needed.

Abstract: In order to prove the possibility to adopt effectively metal shear panels for practical applications and to define specific design methodology, a case study, related to the retrofitting of the hospital building of Scafati in Campania, is presented in this paper. Based on the results of previous full-scale tests on a real r.c. frame reinforced with pure aluminium shear panels, a design procedure has been implemented in order to define the optimal configuration of shear panels to be applied to improve the seismic performance of the building under consideration. Then, a parametrical study by means of dynamic analyses under different historical records has been developed taking into account different hypotheses of modeling for the RC structure. The obtained results allows to confirm the effectiveness of the proposed system, which is able to increase significantly the seismic performance of existing structure. In addition, the outcomes of the study provide interesting indications for design applications.

Abstract: The bridge in Poggio Renatico crossing the Reno river on the railway line between Bologna and Ferrara, consists of steel decks supported by masonry abutments and piers, while foundations and pier caps are made of reinforced concrete. After the 2012 Emilia Earthquake and accounting for the fluvial erosion below the piers foundations, a structural assessment of the bridge was carried out in accordance with to the current Italian rules. Although a sufficient structure capacity against the actual transit loads resulted, the bridge showed some inadequacies with respect to the load models provided by both the national standard for constructions and the guidelines of the Italian railway network company. The retrofitting project consists of an improvement of the structural capacity of all the elements: girders, piers and abutments. An innovative retrofitting solution provides for the strengthening of the existing decks through a suspension system of cables anchored to steel towers standing on both abutments and piers and creating a kind of suspended bridge. The retrofitting is compatible with the normal scheduled interruptions of the rail traffic thereby reducing the maintenance costs of the railway system. The structural solution represents a model easily replicable to solve analogous situations along the railway network.

Abstract: This paper presents some preliminary results from the numerical investigations of different interventions for the seismic upgrading of a masonry bell tower. Masonry bell towers belong to the cultural and historical heritage, are very widespread in Italy and their conservation has been given special attention in recent years. Their high vulnerability is related to the combination of mechanical material properties, geometrical irregularities, presence of inclination, foundation settlements and seismicity of the area. The present tower is located in Emilia Romagna Region, Northern Italy, recently stricken by a strong seismic sequence in May 2012. Analyses results show that the retrofitting of masonry bell towers is highly recommended in order to mitigate their present seismic risk. Four different upgrading techniques, consisting of grouted mortar, FRP sheets, internal steel frame and prestressing vertical rods, are investigated and compared in terms of structural performance improvement. The grouted mortar and internal steel frame techniques are found to be reasonable solutions when compared to the other proposals for the specific seismic intensity level. Furthermore, the other techniques have a relatively high level of invasiveness which is recommended to be avoid where possible. Experience has shown that the most effective interventions are those that not only protect the structure, but also preserve the built heritage.

Abstract: Most of the monumental structures worldwide and residential structures in developing countries are built in masonry. The studies performed by various researchers prove the vulnerability of masonry structures under various circumstances, especially under earthquakes, so as to necessitate detailed contemplation. In this paper, a numerical model for nonlinear static analysis of unreinforced masonry walls is developed based on a macro-modelling approach. A detailed parametric study is also performed to analyse the effect of wall thickness as well as length on the behaviour of the masonry wall. The present numerical model can be utilized for risk assessment and seismic retrofitting of historical masonry structures.

Abstract: Reinforced concrete (RC) is the most popular building material in the construction industry. It is a composite material in which low tensile strength and ductility of concrete are counteracted by the inclusion of reinforcement having higher tensile strength and ductility. The RC based structures are required to be replaced after their life time. Complete replacement will be a huge financial burden and might certainly be a waste of natural resources when upgrading or strengthening is an adoptable alternative. Strengthening can be achieved through retrofitting. The meaning of retrofitting is addition of new technology, components, accessories or features to older systems. Retrofitting may be required when the structure needs to be used for a purpose dealing with more load compared to design loads. It may also be used where old structures are needed to be upgraded. This paper is focused on the retrofitting of simply supported RC beams. Various materials like polymers, cementitious composites, steel sections etc. are used for retrofitting of RC beams. For the addition of these new materials to the existing ones, various techniques are used. This paper is a review of the materials and techniques used in retrofitting process of RC beams in existing buildings. The effectiveness of each material and technique is also reviewed.