Impact of Masonry Infill Walls on the Seismic Response of G+7 Reinforced Concrete Building

Transcription

1 Impact of Masonry Infill Walls on the Seismic Response of G+7 Reinforced Concrete Building Shubham M. Adkar PG Student, Department of Civil Engineering, G. H. Raisoni College of Engineering and Management, Pune, Maharashtra, India. Pradnya R. Sikachi Structural Consultant, Pune, Maharashtra, India Dr. Satish B. Allampallewar Professor and HOD Civil Engineering, G. H. Raisoni College of Engineering and Management, Pune, Maharashtra, India. Abstract Reinforced concrete [RC] frame structure with infill walls are being widely used for various purposes such as multi-storied residential, commercial, buildings in the earthquake-prone area. For partition and external walls of building infill walls or panels are commonly used to fill the gap between beam and column The present study investigates the influence of the infill walls on the seismic performance of the high rise reinforced concrete building prone to lateral seismic loads. The study for different conditions is carried out with different infill materials like red brick, AAC block and fly ash brick with different structural arrangements like the bare frame [BF], infill frame [IF], and wall panel frame [WF].The study is carried out for earthquake zone III. During an earthquake, infill acts as a compression strut which converts the load carrying mechanism from frame action to truss action. In the present study, infill effect introduced with the help of equivalent diagonal method according to IS1893:2016(Part 1).The analysis is performed with different methods of analysis like equivalent lateral force method and response spectrum method as per I.S1893:2016 using E-tabs software. The parameters considered for comparison are base shear, storey displacement, storey drift and natural period. Keywords Masonry infill, AAC block, Red brick, Fly ash, Equvivalent diagonal strut, Wall panel, Base shear, Storey drift and displacement, time period. I. INTRODUCTION Due to the Earthquake, seismic response of the building often yields to unnecessary and intense lateral displacements and also effect on the seismic performance of the frame structure as well as the non-structural component of the building [3]. The construction of high rise building in the earthquakeprone area requires respectable design and analysis process which assures correct modelling and analysis of the structure which result, reduction in damage at the time of the earthquake [4]. Infill walls are commonly used as a partition in frame structures due to various benefits such as ease of construction, soundproofing property, good aesthetic view, ease of material availability etc. Normally infill walls are treated as a non-structural element in structural analysis, the mass is considered however its structural characteristics such as strength and stiffness are neglected [5]. Even though, it provides lateral stiffness to the bare frame structure up to some extent [6]. The conventional modelling of Reinforced concrete frame structures [BF] in which the effect of infill is not considered which states that the structure is more flexible than they actual. In actual practice, the overall stiffness of the structure is increased which results in the shorter time periods because of the influence of infill walls [7]. The infill walls influence the seismic performance of buildings it depends upon the detailing specifications and mechanical properties like the relative stiffness and strength between the frame and the walls, the form of connection between and connecting frame elements etc. In recent earthquakes, many buildings have been suffered severe effect due to their poor performance related to the influence of infill walls such as soft storey and weak storey effect [8]. In the latest edition of the I.S 1893:2016 some precise information is given regarding the effect of infill walls on the structure during the earthquake [6]. The arrangement of the unreinforced [URM] with moment resisting frame in the RC building, there is variation in the structural properties like storey stiffness and strength along its height when in-plane stiffness and strength of URM infill 901 Shubham M. Adkar, Pradnya R. Sikachi, Dr. Satish B. Allampallewar

2 walls are considered. If those properties are not consider building tends to be irregular. II. INDIAN STANDARD CODE 1893:2016 PROVISIONS I.S 1893:2016 states that URM infill wall can be modeled as an equivalent diagonal strut. The ends of the equivalent strut should be treated as pin jointed which are connected to the RC The calculations of the width of the equivalent diagonal strut are stated under clause no also, the thickness of the URM infill wall should be used as a thickness of the equivalent diagonal strut [1]. URM infill shall be modeled by using equivalent diadonal strut as below: For walls without any openning, width W ds of equivalent diagonal strut shall be taken as: where, (1) III. OBJECTIVES To evaluate the response of the BF, IF and WF subjected to seismic loads as per I.S 1893:2016. To study the influence of different infill materials such as red brick, AAC block, fly ash brick on the seismic performance of the structure. To study the response of different frames with different infill material for earthquake zone III. IV. PROBLEM STATEMENT Following structural details were assumed: No. of stories: G+7 Depth of Foundation: 2m Floor to floor Height: 3.6m Type of Building: Residential Size of Beams: 230 X 600 mm Size of Columns: 600 X 600 mm Thickness of Slab: 150mm Thickness of External and internal wall: 230 mm Height of Parapet wall: 1.2 m (2) E m = Modulus of elasticity of the materials of the URM infill E f = Modulus of elasticity of the materials of the RC MRF I c = moment of inertia of the adjoining column t = thickness of the infill wall θ = angle of the diagonal strut with the horizontal Fig.1 Equvivalent Diadonal Strut Of URM Infill Wall. Fig.2 PLAN a) Loading details Live load on floor: 3 KN/M 2 Live load on roof: 1.5 KN/M 2 Floor finish on floor: 1.5 KN/M 2 Floor finish on roof: 2 KN/M Shubham M. Adkar, Pradnya R. Sikachi, Dr. Satish B. Allampallewar

3 b) Seismic details Type of Frame: RC building with Special moment resisting frame [SMRF] Earthquake zone: Zone III Type of soil: Hard [Type-I as per IS1893:2016] Importance factor: 1.2 [Table no. 8 IS1893:2016] Response reduction factor: 5 Damping of structure: 5% Response spectra: As per IS1893:2016 Time period: 0.075(H) 0.75 [Bare frame] 0.09H/d (1/2) [Infill frame and wall panel frame] TABLE 1. MASONRY MATERIAL PROPERTIES Property name AAC block Red brick Fly ash brick Unit weight (KN/M 3 ) Elastic Modulus(MPa) Fig.4 WALL PANEL FRAME [WF] TABLE 2. DIAGONAL WIDTH OF STRUT Wall span AAC block Red brick Fly ash brick 6m m m Fig.2 BARE FRAME [BF] Fig.3 INFILL STRUT FRAME [IF] V. RESULTS AND DISCUSSION 1. BASE SHEAR: Following are the percentage differences of base shear: a) AAC block : There is an increase in base shear by 96.13% and 88.49% for infill frame and 89.85% and 82.60% for wall panel frame in x and y-direction respectively than base shears for a bare b) Red brick : There is an increase in base shear by % and 95.7% for infill frame and 93.26% and 85.90% for wall panel frame in x and y-direction respectively than base shears for a bare c) Fly ash brick : There is an increase in base shear by % and 94.09% for infill frame, 99.76% and 92.14% for wall panel frame in x and y-direction respectively than base shears for a bare 903 Shubham M. Adkar, Pradnya R. Sikachi, Dr. Satish B. Allampallewar

4 Fig.8 STOREY DRIFT IN Y-DIR Fig.5 BASE SHEAR IN X-DIR b) Red brick : There is a decrease in storey drift by 64.86% and 55.45% for infill frame, 79.55% and 60.75% for wall panel frame in x and y- direction respectively than storey drifts in the bare Fig.6 BASE SHEAR IN Y-DIR 2. STOREY DRIFT: a) AAC block : There is a decrease in storey drift by 48.41% and 36.02% for infill frame, 54.76% and 42.15% for wall panel frame in x and y- direction respectively than storey drifts in the bare Fig.9 STOREY DRIFT IN X-DIR Fig.7 STOREY DRIFT IN X-DIR Fig.10 STOREY DISPLACEMENT IN Y-DIR c) Fly ash brick : There is a decrease in storey drift by 68.81% and 60.26% for infill frame, 73.56% and 64.90% for wall panel frame in x and y- direction respectively than storey drifts in the bare 904 Shubham M. Adkar, Pradnya R. Sikachi, Dr. Satish B. Allampallewar

5 Fig.11 STOREY DRIFT IN X-DIR Fig.13 STOREY DISPLACEMENT IN Y-DIR 2. Red brick : There is a decrease in storey displacements by 53.20% and 45.99% for infill frame, 39.60% and 32.48% for wall panel frame in x and y-direction respectively than storey displacements in the bare Fig.12 STOREY DRIFT IN Y-DIR 3. STOREY DISPLACEMENT Following are the percentage differences of storey displacements for roof level: 1. AAC block : There is a decrease in storey displacements by 33.68% and 25% for infill frame, 22.80% and 14.15% for wall panel frame in x and y-direction respectively than storey displacements in the bare Fig.14 STOREY DISPLACEMENT IN X-DIR Fig.15 STOREY DISPLACEMENT IN Y-DIR Fig.13 STOREY DISPLACEMENT IN X-DIR 3. Fly ash brick mas onry: There is a decrease in storey displacements by 59.05% and 53.33% for infill frame, 42.67% and 35.69% for wall panel 905 Shubham M. Adkar, Pradnya R. Sikachi, Dr. Satish B. Allampallewar

6 frame in x and y-direction respectively than storey displacements in the bare TABLE 3 NATURALTIME PERIOD IN X- DIRECTION BARE FRAME INFILL STRUT FRAME WALL PANEL FRAME AAC RB FA AAC RB FA AAC RB FA IS Et ab s TABLE 4 NATURALTIME PERIOD IN Y- DIRECTION Fig.16 STOREY DISPLACEMENT IN X-DIR BARE FRAME INFILL STRUT FRAME WALL PANEL FRAME AAC RB FA AAC RB FA AAC RB FA IS Et ab s Fig.17 STOREY DISPLACEMENT IN Y-DIR 4. TIME PERIOD Following are the percentage differences of time periods: a) By I.S code- There is a decrease in the time period by 45.92% and 43.78% for all infill frame and wall panel frame for all three masonries in x and y- direction respectively than the time period for a bare b) By analysis- There is a decrease in the time period by 37.79% and 30.84% for aac, 46.53% and 36.3% for red brick, 49.67% and 38.61% for fly ash in x and y-direction respectively for infill frame as well as wall panel frame than the time period for a bare VI. CONCLUSION a) From the above results, we can say that base shear is much greater in case of infill frame than bare frame then followed by wall panel frame and bare frame for all materials in both x and y-direction. We can also say that as time period decreases base shear value increases. b) Time period obtained from the analysis is more than time period calculated by Indian standard code I.S1893:2016 for all materials. c) Storey drift obtained from the analysis is lesser in case of wall panel frame then followed by infill frame and bare frame for all materials in both directions. d) Storey displacement is reduced considerably in infill frame than bare frame then followed by wall panel frame and bare frame for all materials in both directions. e) From the above results, we can say that fly ash brick seems to be better choice as an infill material due to lesser values of storey drift and storey displacement. 906 Shubham M. Adkar, Pradnya R. Sikachi, Dr. Satish B. Allampallewar

7 References 1. I.S 1893[PART1]:2016 Criteria for earthquake resistant design of structure. 2. I.S 13920:2016 Ductile design and detailing of reinforced concrete structure subjected to seismic forces. 3. Prerna Nautiyal, Saurabh Singh, and Geeta Batham A comparative study of the effect of infill walls on seismic performance of reinforced concrete buildings, International Journal of Civil Engineering & Technology (IJCIET), Volume 4, Issue 4, Pg. no , ISSN: Wakchaure M. R, Ped S. P Earthquake analysis of high rise building with and without infilled walls, International Journal of Engineering and Innovative Technologies(IJEIT), Volume 2, Issue 2, Pg. no Manthan Vasani, Satyen Ramani Comparative study of the effect of infill walls on the fixed base and base-isolated reinforced concrete structures, a journal of Engineering Technologies and Innovative Research ( JETIR), Volume 4, Issue 4, Pg. no , ISSN: Haroon Rasheed Tamboli, Umesh Karandi Seismic analysis of RC frame structure with and without infill walls, Indian Journal of Natural Sciences (IJONS), Volume 3, Issue 14, Pg. no , ISSN: Narendra Kaple, V. D. Gajbhiye, S. D Malkhede Seismic Analysis of RC frame structure with and without infill walls, International Conference on Electrical, Electronics and Optimization ( ICEEOT), Pg. no , ISSN : Nusfa Karuvatti, Priyanka D P Linear Static Analysis of infilled soft story RC buildings with and without opening for earthquake resistant design, International Journal of Scientific Research in Science, Engineering & Technology (IJSREET), Volume 2, Issue 5, Pg. no , ISSN: Ms Rajashri A. Deshmukh, Dr. P. S. Pajgade A study of the effect of infill material on seismic performance of RC buildings, International Journal of Engineering Science & Research Technology (IJESRT), Volume 1, Issue 4, Pg. no , ISSN: Bhanupratap R Mehadia, Dr U.P. Waghe et.al Comparatives studies in analysis and design of RCC structures with and without infill wall under seismic effect, International Journal of Science Technology & Engineering ( IJSTE), Volume 2, Issue 10,Pg. no , ISSN: Akash M Patel, Karuna S A comparative study of the seismic response of bare, infilled and braced RC framed tall structures considering the effect of the soft story, International Journal of Advanced Engineering &Research Development (IJAERD), Volume 4, Issue 6, Pg. no , ISSN: Monika N, Chaitra D. M., Kirankumar K. L. Comparative study of seismic behavior of RCC building frames with and without infill wall, international Research journal of Engineering Technology ( IRJET), Volume 4, Issue 5,Pg. no , ISSN : Nesiya Yoosaf, Remya Raju, Hashim K Abdul Azeez Comparative study of multi-storied RC building with open ground storey having different Type Infill walls,, international journal of Engineering Trends and Technology (IJETT), Volume 28, Issue 7,Pg. no , ISSN : Diana Samoila, Andrei Faur The influence of the seismic action on the RC infilled frames, International organization of Scientific Technology, volume 4, Issue 12,Pg. no ISSN:2278: Nikhil Bandwal, Rahul Jichkar, Nitesh Thikare Influence of opening in the brick infilled wall on the stiffness of RCC frame,international journal of Science, Engineering and Technology (IJSETR), Volume 4, Issue 11,Pg. no , ISSN : Shubham M. Adkar, Pradnya R. Sikachi, Dr. Satish B. Allampallewar