Retrofitting of buildings

Retrofitting of building

1. Retrofitting Of Buildings. Shehr Yaar Abdullah ( 17CE23) CED, Balochistan UET, Khuzdar, PAK. Point in Question: Represented By

2. Content Of Topic: Introduction to r etrofitting. Goals of retrofitting. Need of retrofitting. Why retrofitting is required? To retrofit or not? Stages of retrofitting. Condition assessment of buildings & its Steps. Material used in retrofitting C lassification of retrofit techniques. Existing retrofitted s tructures in Balochistan. Critical remarks. 2

3. INTRODUCTION TO RETROFITTING: 3 Retrofitting  is the process of addition of new features to older buildings , heritage structures , bridges etc . Retrofitting is the process of modification of existing structural members to increase its resistance to load . It  reduces the vulnerability of damage of an existing structure during a near future seismic activity . It  helps to increase the strength , resistivity and overall lifespan of the structure.

4. GOALS OF RETROFITTING: 4 To increase the lateral strength and stiffness of the building. To increase the ductility and aims to avoid the brittle modes of failure . To increase the integral action and continuity of the members in a building . To eliminate or reduce the effects of irregularities . This aims to eliminate the possibility of progressive collapse . To ensure adequate stability against overturning and sliding.

5. NEED OF RETROFITTING: 5 The need for retrofitting can arise due to any of the following reasons: Building not designed to standard code . S ubsequent updating of code and design practice . Subsequent upgrading of seismic zone . Deterioration of strength and aging and Modification of existing structure. In Pakistan , almost 75% of total buildings are non-engineered buildings made up of earthen walls , stone walls , brick masonry walls , etc. These buildings are more vulnerable to seismic activities.

6. Why retrofitting is required? 6 The need for retrofitting due to problem face in concrete structure: Damage to the structural members . Excessive loading. Errors in design or construction . Seismic damage. Structural failure. In Corrosion due to penetration .

7. TO RETROFIT OR NOT? A decision depends on many factors. Lifeline buildings , such as hospitals must necessarily be retrofitted, in view of their extreme importance . But should the aim of retrofit be to raise this capacity to 100% . L ifeline buildings such as fire stations , hospitals , power stations , telephone exchanges , television stations , radio stations, railway stations, air ports. Important service and community buildings such as schools , cinema halls , multiplexes , marriage and other assembly halls , the capacity should be raised to 100% . 7

8. STAGES OF RETROFITTING: A D 7. Verification of retrofit scheme 8. Construction 9. Maintenance & Monitoring

9. 9 CONDITION ASSESSMENT OF BUILDINGS: Condition assessment describes the process of assessing the actual condition of a structure in relation to the requirement . It indicates whether the structure is satisfactory, or, whether repair and rehabilitation are necessary. Condition assessment includes the following steps. Initial inspection and appraisal . Review of documents. Detailed investigation. Reporting and recommendations.

10. 10 Condition assessment of building has two major steps: Visual Inspection Detailed Investigation Visual Inspection: Thoroughly visual inspection of following factors, Misalignment. Deformation. Cracks in welds. Missing bolts / rivets. Concrete cracks Spalling & Staining Disintegration of the surface, Honey-combing. Exposed reinforcement Steel corrosion. Stress concentration. Crippling or buckling. Bowing.

11. 11 Detailed Investigation: It proposes of following steps, Obtaining the properties of the structural materials used in the building . Determining the type and disposition of reinforcement in building . Locating deteriorated material and other defects . Tests for detailed investigation A number of tests are available to study the condition of the material in a structure : Rebound Hammer test Thermal methods Radiography Electromagnetic techniques Stress wave propagation method Intrusive Tests Core test In-Situ Shear test Flat-Jack test In-Situ Permeability

12. MATERIALS USED IN RETROFITTING : Epoxy Mortor

13. CLASSIFICATION OF RETROFIT TECHNIQUES: Retrofitting techniques are basically classified as, Global Retrofit Strategies II. Local Retrofit Strategies Global Retrofit Strategies To provide increased lateral stiffness and strength to the building as a whole. And, to ensure that a total collapse of the building does not occur. Local Retrofit Strategies To avoid failure of the components, and also thereby enhance the overall performance of the structure More than one combination of local and global retrofit strategies is possible 13

14. 14 GLOBAL TECHNIQUES: LOCAL TECHNIQUES: Addition of Infill Walls Addition of Shear walls or wing walls or Buttress Walls Addition of Steel Braces Reduction of Irregularities and Mass Reduction. Concrete Jacketing, Steel Jacketing

15. 15 Infill Walls:

16. 16 Concrete Jacketing: It involves addition of a layer of concrete, longitudinal bars and closely spaced ties. The jacket increases both the flexural strength and shear strength of the column. To increase the flexural strength, the additional longitudinal bars need to be anchored to the foundation. If the jacket is only partially around the existing column, the new bars can be welded to the existing bars. It involves drilling holes in the existing beam. But drilling holes for the stirrups at closing spacing damages the beam.

17. 17 Steel Jacketing: It refers to encasing the column with steel plates and filling the gap with non-shrink grout . If the shear capacity needs to be enhanced, the jacket is provided throughout the height of the column. Circular jackets are more effective than rectangular jackets . The plates are attached to the tension face of a beam to increase the flexural strength, whereas they are attached to the side face of a beam to increase the shear strength.

18. 18 Steel Jacketing:

19. 19 EXISTING RETROFITTED STRUCTURES IN BALOCHISTAN: World’s famous boot house in Quetta, Balochistan. Retrofitting Quaid E Azam Residency, Ziarat , Balochistan . Retrofitting

20. 20 CRITICAL REMARKS: Increase in the capacities( strength, stiffness, ductility, stability and integrity) of concrete structure. The reduction in loss of lives, damage of the essential facilities and functional continuity of life-span of structures. Decrease the working space of concrete structure due to extension in structural elements and affect the appearance. Increase in lateral stiffness with high shear concentration near wall. ■ Increase in overturning moment at foundation.

21. THANK YOU !  Shehr Yaar Abdullah Shahwani Phone [phone] Email shehryarabdullah008@gmail .com