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Seismic Safety of Masonry Structures

The IAStructE – IIIT Hyderabad student chapter of the Earthquake Engineering Research Centre (EERC) organised an online one day workshop on 11 November on the occasion of ‘Structural Engineers Day’. The theme of the workshop was Seismic Safety of Masonry Structures and the event was sponsored by SERB (DST, Govt. of India) under the Scientific Social Responsibility (SSR) policy. A total of 4 sessions were organised as a part of this workshop preceded by the inaugural function, which delved into diverse aspects of earthquake safety of masonry buildings, exploring various methodologies and best practices. The distinguished guests and experts shared their knowledge and engaged in insightful discussions throughout the day.

The inaugural event marked the commencement of a knowledge-packed day aimed at fostering learning and significant discussions on earthquake safety of masonry buildings. The event was open to UG students, PG students, research scholars, structural engineers, faculty, industry people and members of the academic and research community. The gathering brought together around 200 participants eager to engage in a day of insightful sessions. Dr. P Pravin Kumar Venkat Rao, faculty advisor, welcomed the guests and addressed the participants. The event began with an inaugural address by the chief guest, Shri. Manoj Mittal, past president, IAStructE, set the tone for the day by highlighting the significance of the workshop and its objectives. The guest address was given by Dr. Er. Ar. S P Anchuri, chief consultant, Anchuri & Anchuri Firm, Hyderabad and Dr. Visalakshi Talakokula, vice president, southern region, IAStructE. Both the guests of honour graced the audience with their inspirational words and emphasised the sheer necessity of knowledge on masonry and its importance in the construction of housing stock being discussed in the one-day workshop.

 

Inaugural Event: https://www.youtube.com/watch?v=EHtmVInMBak&list=PL8m__37oxV1b77jcf1m3VK2GSbLFPQlda&index=9

The First Session was on “Modelling and Seismic Analysis of Existing Masonry Structures: Recent Research Experiments at IIT Madras” by Prof. Arun Menon,  Department of Civil Engineering, IIT Madras. The speaker provided a comprehensive overview of masonry structures’ behaviour in past earthquakes and their local and global damages due to poor design. Additionally, he offered a detailed explanation of seismic detailing of masonry structures with emphasis on flexure mechanism to eliminate diagonal shear failure in masonry walls. He concisely summarized the approach to modelling existing masonry structures, seismic verification, and local mechanism checks. He emphasized the importance of non-linear analysis using time history and pushover methods for analyzing historical and contemporary masonry structures. The lecture included a weak link identification approach methodology for the out-of-plane capacity of unreinforced masonry piers and also the estimation of seismic strengthening methods. The presentation also involved a thorough approach to modelling masonry buildings using the equivalent frame method with rigid offsets to perform a 3D analysis. To conclude the presentation, he discussed the performance-based seismic assessment and verification of masonry structures through experimental and numerical studies.

 

Dr. Arun Menon, IIT Madras: https://www.youtube.com/watch?v=pRKOpCxyx5Y&list=PL8m__37oxV1b77jcf1m3VK2GSbLFPQlda&index=10

The second session was on “Seismic Safety of Masonry Adobes through Caging, Confinement, and Waste Added Engineered Cementitious Composites” by Dr. Sanket Nayak, Associate Professor, Department of Civil Engineering, IIT (ISM) Dhanbad. He started his presentation by giving a brief outline of past earthquakes that struck India and highlighted the seismic vulnerability of non-engineered (masonry) buildings. He explained the need to retrofit existing masonry structures using external and internal strengthening techniques. During his presentation, he gave an overview of the experiments conducted at the material-, component-, and structural level on composites, strengthened masonry panels and retrofitted buildings, respectively. The presentation involved loading undertaken for the flexure tests and diagonal compression tests and their inferences were shared. Additionally, he offered a detailed explanation of the in-plane and out-of-plane behaviour of strengthened specimens using Polypropylene (PP) fibre mesh (external technique) and Polyethylene Terephthalate (PET) short fibres (internal technique). He provided clear insights on the efficacy adjudgment of strengthening technique on building models and their failure patterns were discussed. Additionally, the lecture included flexible and rigid roof diaphragm actions. At last, the discussion moved forward to the necessity of government initiatives and further experimental research required to strengthen the existing masonry structures under seismic loading.

 

Dr. Sanket Nayak,  IIT (ISM) Dhanbad: https://www.youtube.com/watch?v=WxzJlVc4wLk&list=PL8m__37oxV1b77jcf1m3VK2GSbLFPQlda&index=11

The third session was on “Strengthening of Masonry using Externally Bonded Cementitious Matrix Grid” by Dr. Vaibhav Singhal, Associate Professor, Department of Civil Engineering, IIT Patna. He provided a detailed review of externally bonded strengthening techniques for masonry construction. He discussed the advantages of cementitious matrix grid (CMG) composites over epoxy-based composites. He summarized the guidelines for the design and construction of fibre-reinforced cementitious matrix (FRCM) composites for strengthening the existing masonry buildings. Additionally, he offered a comprehensive description of the mechanical properties of such composites obtained from coupon tests and their behaviour under direct tension from the uncracked phase to the crack development phase and the fully cracked phase. The presentation involved the requirement of advanced material characterization tests like shear bond tests and pull-off tests on composites adhered with masonry substrate. The speaker also delved into experimental investigations with thorough discussions on test setups, the preparation of specimens, the application of composites and the failure modes of the specimens. He also highlighted the importance of the anchorage system and the quality of mortar to be used to prevent debonding failure mode. The session also includes the design of strengthening interventions like wall retrofitting for shear and flexure strength enhancements. He also discussed the shake-table tests on URM and FRCM strengthened infills and explained the significance of ductile failure of structural components using such composites to preserve structural integrity.

 

Dr. Vaibhav Singhal, IIT Patna: https://www.youtube.com/watch?v=hudUNcg87hY&list=PL8m__37oxV1b77jcf1m3VK2GSbLFPQlda&index=12

The fourth and last session was on “Influence of textile reinforcement on the performance enhancement of masonry structures” by Dr. R Siva Chidambaram, Senior Scientist, ACSC Division, CSIR-CBRI Roorkee. He started the presentation by categorizing the different failure patterns of masonry structures under the effect of seismic events. He explained the role of horizontal bands and vertical reinforcements in achieving the integral box action. He gave a brief overview of how vegetation growth and dampness affect the performance of masonry structures. He discussed the use of geogrid cementitious composites for external strengthening of masonry. He emphasized the role of geogrid in achieving large deformation and high energy absorption capacity due to the high elongation of geogrid reinforcement up to 15%. He provided clear insights into the key observations made by using plastic water bottles as another alternative retrofitting technique for brick pallet specimens. Additionally, the lecture included the various techniques developed at CBRI for the safety of masonry houses. To conclude the presentation, he discussed the extent of the building lifting technology development for Indian cities and the need for further advancement in this technology.

 

Dr. R. Siva Chidambaram, CSIR-CBRI Roorkee: https://www.youtube.com/watch?v=KDTcd2zoUg8&list=PL8m__37oxV1b77jcf1m3VK2GSbLFPQlda&index=13

The workshop ended with an engaging and insightful conversation, with active involvement from the participants. The discussion in all the sessions enriched the overall exploration of the history of masonry as a material, its behaviour under lateral loads, and most importantly the techniques to be used for safeguarding and strengthening the existing masonry structures is the need of the hour.