--- title: "Conventional strengthening and innovative-material retrofit" subject: "Building Technology" chapter: 11 key: "semester_6/building_technology:retrofit-strengthening-innovative" source: https://www.bctengineer.com/q/semester_6/building_technology/retrofit-strengthening-innovative site: BCT Engineering --- # Conventional strengthening and innovative-material retrofit Building Technology · Chapter 11: Earthquake protection & Retrofitting in building - Asked in: 2073 Magh - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_6/building_technology/retrofit-strengthening-innovative - Whole chapter: https://www.bctengineer.com/md/semester_6/building_technology/chapter-11 ## Question Explain conventional strengthening methods used for seismic retrofitting and retrofit of structures using innovative materials. ## Short answer Conventional retrofitting uses RCC/steel jacketing, shear walls, wire-mesh plastering and epoxy grouting, but adds mass and disrupts occupancy. Innovative materials like FRP wraps, fibre-reinforced shotcrete, polymer meshes, base isolators and textile-reinforced mortar provide high strength with minimal added weight, without major disturbance. ## Answer #### Conventional strengthening methods 1. **RCC jacketing** of columns, beams and walls to enlarge the section and increase confinement. 2. **Steel jacketing/plates/angles** with grout; steel bracing (X or V) in frames. 3. **Adding RC shear walls** or infill walls to give lateral stiffness. 4. **Wire-mesh/ferrocement plastering** on masonry walls. 5. **Strengthening foundations:** enlarging footings, underpinning, adding tie beams, grouting the soil. 6. **Strengthening connections** and anchoring roofs; adding bands and vertical bars to masonry. 7. **Epoxy/cement grouting** of cracks and honeycombs. 8. **Reducing seismic demand:** removing upper storeys, heavy parapets and tanks. Disadvantages: these methods add mass, enlarge sections, are slow, and disturb the occupants. #### Retrofit using innovative materials 1. **FRP (fibre reinforced polymer) wraps/laminates:** carbon (CFRP), glass (GFRP) or aramid sheets bonded with epoxy to columns (confinement), beams (flexure/shear), walls and slabs. They are light, strong, corrosion-free and quick to apply, with no increase in section, but they are costly, weak in fire, and need skilled work. 2. **Fibre reinforced concrete / shotcrete and ECC** (engineered cementitious composites) for jackets and overlays. 3. **Steel fibre or polypropylene mesh, geosynthetics and GFRP grids** in plaster overlays for masonry (e.g. polymer mesh used in Nepal after 2015). 4. **Shape memory alloys and prestressed straps:** give active confinement and close cracks. 5. **Base isolators and dampers** (rubber bearings, viscous dampers): reduce the force reaching the structure; used in important buildings. 6. **Textile-reinforced mortar (TRM)** and high-performance mortar overlays. These materials give high strength with little added weight, so they are suitable for retrofitting without major disturbance. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. What is a disadvantage of conventional strengthening methods? A. They are weightless B. They add mass, enlarge sections, are slow and disturb occupants C. They require no skill D. They reduce stiffness Answer: B. RCC and steel jacketing add weight and section size. (Key point: Conventional drawback) 2. How is FRP used in retrofitting? A. Carbon/glass/aramid sheets bonded with epoxy to columns, beams, walls and slabs B. Poured as concrete C. Bolted as steel plates only D. Used only as paint Answer: A. FRP wraps provide confinement and flexural/shear strength with little added weight. (Key point: FRP use) 3. Which is a limitation of FRP? A. Heavy and corrodes B. Increases section size greatly C. Costly, weak against fire, and needs skilled work D. Very slow to install Answer: C. FRP is light and corrosion-free but expensive and fire-sensitive. (Key point: FRP limitations) 4. What do base isolators and dampers do? A. Increase the seismic force B. Only support gravity loads C. Replace foundations D. Reduce the force reaching the structure Answer: D. They reduce seismic demand and are used in important buildings. (Key point: Base isolators) ## Related in Building Technology - [Why temporary structures are used](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Awhy-temp-structures) — Building Technology, chapter 8 - [Repair versus retrofit; configuration factors](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Aretrofit-vs-repair-config) — Building Technology, chapter 11 - [Retrofitting a brick masonry building](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Aretrofit-brick-masonry) — Building Technology, chapter 11 - [Techniques of retrofitting a building](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Aretrofit-techniques) — Building Technology, chapter 11, asked 3× - [Retrofitting and jacketing](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Aretrofit-jacketing) — Building Technology, chapter 11, asked 2× - [Retrofit versus repair; column jacketing](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Aretrofit-vs-repair-jacketing) — Building Technology, chapter 11 ## Related in other subjects - [Seismic strengthening techniques for masonry buildings](https://www.bctengineer.com/question.md?key=semester_5%2Fdesign_of_timber_and_masonry_structures%3Astrengthening-retrofitting-masonry-buildings) — Design of Timber and Masonry Structures, chapter 7 - [Types of structures based on material](https://www.bctengineer.com/question.md?key=semester_4%2Ftheory_of_structures_i%3Atypes-structures-material) — Theory of Structures I, chapter 1, asked 2× - [Why composite materials are used](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Acomposite-materials-why-used) — Civil Engineering Materials, chapter 10, asked 2× - [Why pozzolanic materials are used](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Awhy-pozzolanic-materials-used) — Civil Engineering Materials, chapter 4, asked 2×