To Analysis the In Situ Structural Assessment and Strengthening of Disaster Affected Structures

INTRODUCTION

In India specifically in Metro Cities the residential and industrial buildings construction rapidly increases. The mass of population and several commercial area are associated in comparatively small area due to land rate and other reasons in metro cities but due to quite a lot of reasons either manmade and natural theses structure affected by disaster. Fire is one of the major source of such kind of disaster. It is also not economical to demolish the buildings and build a new building. Fire is one of the most severe hazards that building structures may experience during their lifetime. If a structure is damaged by fire, it is necessary to investigate the cause of the fire and evaluate the reusability of the damaged structure. In terms of economic efficiency, it may be a better approach to retrofit the damaged components of the structure, instead of demolishing it partially or completely. This decision must be made based on the result of investigations such as the structural audit, visual inspection of the damaged structure, tests on the remaining material, and finite element simulations of the structure or its structural components. To avoid the loss the buildings structural audit is necessary to check its structural stability after fire disaster and the strengthen of building by appropriate method is very much essential.

The Purposes of Structural Audit are:

• To save Life and Property.

 To know the health of your building and to project the expected future life. society to understand the seriousness of the

• Problems and the urgency required to attend the same.

• To comply with Municipal or any other statutory requirements

Significance: Exact details of distress at column,

1) It is useful for loan application to bank, for loan insurance claim. 2) Audit helps to understand the condition of structure or building before purchase or sale flat. 3) The property owner can understand the exact structural condition of the building. 4) After audit is done it is easier to convince, to get co-operation and fund from members. 5) It is necessary to produce report if required by register, or BMC or another government department. 6) It helps contractor to know the exact nature of distress before touching the structure for repair so chances of increasing the cost is minimum

LITERATURE REVIEW

Mazza and Imbrogno (2019) Author states that the thermal analysis of RCC members in framed structure is carried out for two fire conditions, on the assumption that the fire compartment is confined to the ground and first floor levels. There are four fire-damage conditions are checked, considering only the heating phase, at 30 and 45 minutes of fire resistance, and the overall fire cycle, for fast, medium and slow phases of cooling. The building is supposed to be repaired and retrofitted with hysteretic damped braces (HYDBs), in order to achieve the performance levels imposed by current Italian code in a high-risk seismic zone. Nonlinear static and dynamic analysis of the damped braced and unbraced structures is carried out, with reference to the degradation of R.C. frame members for different fire exposure durations in the design procedure of the HYDBs. Jun Zhou and Lu Wang (2019) Author describes here that fire accidents in the buildings have led to a great loss of buildings and damage to property in the past two decades. There is a need to provide different approaches to increase structural safety and stability of structural members after fire accidents. This study reviews on the repair of fire-damaged reinforced concrete (RC) members with axial load. The findings of the effects of loading method, physical dimension and bonding behavior on the residual strength of members are presented. Meantime, the available study on the performance of fire-damaged RC members with axial load repaired with steel jacketing, concrete jacketing and fibre reinforced polymer (FRP) jacketing are summarized. This paper described a review of the repair methods for fire damaged compressed compressed elements. Although the construction is easy, the clearance of the building is reduced, which affects the subsequent use.

Marco Di Ludovico (2018) Author find that there is no appearance of severe damage for reinforced concrete elements, except for spalling of mortar screeding found appeared in certain parts of columns and beams. No crack found on the concrete surface. Strength of concrete beams and columns has been estimated by using Schmidt rebound hammer test. Paper Conclude that strength of concrete is still unaffected by the fire. It shows the finding of the physical inspection on the appearance of the concrete surface, i.e. no indication of degradation of strength of concrete in the building structure. Antonio Brancaccio (2018) in this paper Author highlights on the importance of in-situ assesment of structures also finalized to properly design and calibrate innovative structural strengthening solutions such as FRP (Fibre Reinforced Polymers). This paper Conclude that overview of the current methods of performing structural surveys, in-situ material testing and innovative techniques for full-scale structural evaluation. Further, the paper aims to describe this topic by presenting a remarkable case study of a fire-damaged reinforced concrete (RC) industrial structure, located in Dubai, on which an extensive experimental procedures on materials

OBJECTIVES

• To Analysis the structural damage of fire affected buildings from Structural Audit of building by taking actual case studies (1st case study for Identification of Damages for fire affected buildings and 2nd Case study for Identification of Damages for fire affected buildings as well as identification of strengthening technique.

• To do seismic assessment of the damaged building

• To prepare the detail report of structural audit and give recommendation regarding stability of fire affected buildings

DATA COLLECTION: SITE DETAILS

The management of SP Concave Roha, Tal. Roha Dist: Raigad has planned to carry out Structural health assessment of their mixer plant building after the fire accident on 12/02/2022. The building has two manufacturing area and mixer plant building attached to the plant area. Fire is caused by electric short circuit at ground floor, at 8.20am. Fire is controlled at 12.30pm. The said building is Ground + two stored RCC framed structure constructed in 1977. Architectural and structural drawings were available for the reference.

and bond condition between steel and concrete. All surfaces are checked and inspected for colour change, surface crazing, cracking etc. Visual inspection on ground floor shows that RC members are not affected by the fire. No color change on surface is noticed. Plaster at certain location is cracked and spalled. Slab covers at certain panels are spalled cause of oxidation of steel. All structural steel members supporting the mixer unit are in good condition. Connections are also in good condition. Concrete floor surface is damaged due to wear and tear. On the first floor reclaimed rubber, machine oil, FRP pallets and drums were kept. Rubber is burnt partially and pallets are partially melted. Remains of MS frame of oil drums neither bent nor melted. RC beam and slab in the grid B26-C27, D28-D29 were affected by fire and heat. Spalling of cover concrete is observed. Reinforcement is exposed in certain members. Inspection of mild steel reinforcement in RC members doesn‘t show any de bond condition. No powdered steel existence is observed. Freshly broken concrete shows grey color. Plaster of all members is completely damaged on the first floor. Plaster surface shows crazing and cracking. Carbon powder, whitening powder, silica and power oil stored on second floor. Entire surface area turned black due to smoke. No cracks, color change, cracking, spalling of concrete is observed on second floor. Plaster surface at certain location was cracked. Material store don second floor is not burn

Table 3: Comparison of Results of Ultrasonic pulse velocity Observations

The average strength of core sample as taken in unaffected area is 15.03 MPA while in affected Area 14.75 MPA. The average strength of the building is 14.89 MP

The probable accuracy of prediction of concrete strength in a structure by the Rebound hammer is ± 25 % As per IS code 13311 (Part-I & II)

24.94 MPA.

Table 7: Comparison of Results of all Testing Methods

In visual inspection, there is no appearance of severe damage for reinforced concrete elements, except for spalling of mortar. No cracks are found on the concrete surface. Comparison of color and texture shows that the elements were experiencing less than 3000c temperature. Strength of concrete members has been estimated by using Rebound hammer and core test. From the Rebound hammer test results, it indicates that average strength of concrete is 24.94MPA (Table no- 7.5 & 7.6), while according to drawings the grade of concrete is M15. The increase in strength of concrete in may because of hardening of surface. The core sample taken from affected area gives the average strength of 14.89 MPA (Table no.-7.4) while from unaffected area average strength is 15.03 MPA (Table no- 7.4). The Ultra Sonic Pulse Velocity (USPV) results show average velocity of 2980 m/s in affected area and 3340 m/s in unaffected area. Average USPV is 3160 m/s. According to IS13311 Part 1:1992, the velocity between 3000 to 3400 m/s, gives medium grade rating of concrete quality. The deflection is 5-12mm in X and Y direction for the base shear of 1210 KN. Push over analysis for earthquake stability of the structure shows immediate occupancy. It is summarized from visual inspection and NDT testing those reinforced concrete elements inside the building are not majorly affected externally by the fire. Comparison of color and texture shows that the elements experienced less than 600° C temperature. RC members were affected externally only. There is no appearance of severe damage for RC members except spalling of plaster and cover concrete at certain parts of beam and slab. No estimates appears to be higher than unaffected area. This is due to hardening of surface. But compression test on core cut samples show 2 % drop in strength. Observation on beam said to be directly caught in fire for portion of exposed cover show that even the binding wire was not affected by fire, ruling out possibility of damage to R/F bars. As a overall conclusion it can be stated that strength of concrete is unaffected by the fire. Age of structure being more than 50 years, it is considered that it has served the useful service life. Being located in seismic zone IV, it is necessary to take precautionary measure for strengthening of some of the members, especially those showing NDT results in poor class.

1. Mazza and Imbrogno (2019) ―Effect of Fire duration on Seismic Reinforcement “Jornal of Built Environment,Volm 7,Page 140-147. 2. Jun Zhou and Lu Wang (2019) ―Repair of Fire-Damaged Reinforced Concrete Members with Axial Load: A Review‖ 3. Wenxian Ma, Chunxiang Yin, Jun Zhou and Lu Wang (2019), ―Repair of Fire-Damaged Reinforced Concrete Flexural Members: A Review‖ 4. Marco Di Ludovico (2018),” Advanced materials for seismic retrofit of existing reinforced concrete buildings with poor quality concrete” Journal of Civil & Environmental Engineering | ISSN: 2165-784X | Volume 8 pp 69-74. 5. Antonio Brancaccio (2018) In-Situ Structural assessment and FRP Strengthening of a Fire Damaged RC Structure: A Case Study‖, International Journal of Civil Engineering Research.ISSN 2278-3652 Volume 8, Number 4 pp.21-56. 6. Er. Neha Goyal, Er. Bhavana Arora, Dr. Sanjay Sharma, Dr. Arvind Dewangan (2018),” Performance Evolution and Audit of Structure by NDT Methods” International Journal of Engineering Research And Management (IJERM) ISSN: 2349- 2058, Volume-05, Issue-09 7. Totsawat Daungwilailuk,, Thi Nguyen Cao, Withit Pansuk, and Phoonsak Pheinsusom (2017),”Evaluating Damaged Concrete Depth in Reinforced Concrete Structures under Different Fire Exposure Times by Means of NDT and DT Techniques” Engineering Journal Volume 21 Issue 7, ISSN 0125-8281. 8. M H Osman, N N Sarbini, I S Ibrahim, C K Ma,M Ismail and M F Mohd,‖ A case study on the structural assessment of fire damaged

PG Student, Dept of Civil Engg, PVPIT, Pune