EXPERIMENTAL STUDY ON THE EFFECT OF LINTEL ON INFILLED FRAMES UNDER CYCLIC LOADING

Power of the Materials Laboratory” for their friendly attitude and helpful mindset during the experimental work. In our country, in most cases, solid clay bricks are used for masonry walls.

LIST OF TABLES

INTRODUCTION

General
Core Parameters of the study
Objective of the Study
Scope of the Investigation
Methodology of the Study
Outline of the Thesis

One of the most commonly used structural systems in Bangladesh is reinforced concrete (RC) frames with unreinforced masonry (URM) infill walls. An experimental setup was set up to investigate the behavior of the samples under cyclic loading.

LITERATURE REVIEW

Introduction

Behavior of Masonry Infilled RC Frame Structure under Cyclic Loading

Furthermore, he showed that the masonry infill is very beneficial in increasing the stiffness and reducing the deformation of the whole system. Murty and Jain (2000) stated that infills generate interference with the lateral deformations of the RC frame, resulting in the segregation of the frame and the infill along one diagonal and the creation of a compression strut along the other diagonal.

Figure 2.1: Equivalent truss mechanisms for infill frame (Polyakov, 1960).

Different Failure Modes of Masonry Infilled RC Frame Structures

Second, an adjacent column shear failure was caused by a diagonal crack that initiated in the fill near the top windward corner. According to Asteris et al. 2011), the failure of the infilled frame occurs as a combination of distinct modes.

Figure 2.12: (a) Mode of infill failures (b) mode of frame failures (Smith and Coull, 1991)

Disasters and Cyclic Loads on Masonry infilled RC frame Structures

Bangladesh is one of the most prone to natural disasters in the world and is hit by numerous natural disasters almost every year. Among them, earthquakes represent one of the most damaging and deadly natural disasters for humans (Rodrigues et al., 2018).

Figure 2.24: Crustal plate boundaries (burro.case.edu., 2002).

Solid Clay Brick and Perforated Clay Brick

Energy conservation
Cost-effective and low maintenance
Time-saving
Environment-friendly construction
Easy electrical installation

The use of perforated bricks will minimize the dead load of buildings, thereby reducing the cost of building structures. Furthermore, perforated bricks reduce the total weight of structures leading to more seismically efficient infrastructures.

Lintel

Resisting deflection
Transferring loads
Structural Contribution

When an opening is set on a wall, the masonry units above the opening tend to collapse. Lintel is profoundly beneficial in this case, which performs the task of taking care of the load over the opening.

Previous Investigation of MIRCF Structures under Cyclic Loading

The failure dynamics of the infilled frames is also properly understood due to the finite element model. These tests provided the specifications of the frame and infill elements used in the numerical simulations. The mortar compressive strength and the height-to-length ratio of the brick infill wall were core experimental parameters.

The test findings showed that the failure mechanism of AB frames filled with masonry was influenced by the type of masonry. In contrast, column and masonry infill shear failure was the primary mode of failure of AB frames with solid clay brick masonry infills. The strength of the surrounding reinforced concrete (AB) columns, the strength of the AB beams, and the strength of the masonry infill mortar were the three key factors evaluated.

Soulis (2019) stated that the influence of the peripheral mortar joint, which created the contact boundary between the masonry infill and the surrounding frame, was generally neglected.

Codes

Most codes limit the use of seismic design force generated from dynamic analysis to a minimum value based on an empirical estimate of the natural period. Consequently, a masonry-infilled reinforced concrete frame (MIRCF) structure's natural period is often shorter than that of the corresponding bare frame. 2.2) Where Ta is the natural period of MIRCF, h is the height of the building (metres) and d is the base dimension of the building (metres) at the plinth level along the considered direction of the lateral force.

The positive moment strength on the face of the joint must not be less than one third of the negative moment strength on this face (Figure 2.30). Neither the negative nor the positive moment strength at any section along the length of the member shall be less than one-fifth of the maximum moment strength provided at the face of any joint. Stirrups shall be provided at both ends of the girder at lengths equal to twice the depth of the member, measured from the front of the girder towards mid-span (Figure 2.31).

The first stirrup must not be located more than 50 mm from the front of the supporting member.

Figure 2.30: Flexural requirements for beams (IMF) (BNBC, 2020)

Introduction

Material Properties

Cement
Fine aggregate
Coarse aggregate
Clay brick
Water
Mortar
Concrete
Prism Test

In this investigation, two types of rebar were used as 8 mm diameter B420DWR rebar and 12 mm diameter B420DWR rebar. A full-scale perforated clay brick contained 10 holes (each hole was 23 mm in diameter). The results of brick compressive strength tests are presented in Table 3.2 (in accordance with ASTM C67, 2020).

The results of the brick absorption capacity tests are presented in Table 3.3 (in accordance with ASTM C67, 2020). In a set of solid masonry prism and perforated masonry prism, ten solid bricks and perforated bricks were used. The results of the compressive strength test of brick prisms are presented in Table 3.4 (in accordance with ASTM C1314, 2020).

Details of Specimens

Firm base
Anchor bolt and steel plate
Tripod stands
Dial gauges
Hydraulic jack

Then the previously built reinforced structure was placed in the wooden formwork, as shown in Figure 3.10. Figure 3.13 shows eight half-scale perforated bricks made from a single full-scale perforated brick. In the final step, all samples were whitewashed as shown in Figure 3.15 to properly identify the cracks during testing.

Four pairs of anchor bolts were used to fix the base to the ground as shown in Figure 3.18. To hold the dial gauges in predetermined locations, two tripod stands were used as shown in Figure 3.19 (b). Three dial gauges were used to measure the displacement of the samples during the cyclic excitation.

The deformation of the sample due to the applied load of the hydraulic jack 1 is assumed as positive direction.

Figure 3.5: Schematic drawing of SB (Every unit is in mm) [Note: Section A-A, B-B and C-C are the midsection of base, column and beam respectively]

Test Procedure

RESULTS AND DISCUSSION

Introduction

Summary of The Experimental Results of The Specimens

Damage Assessment and Failure Mode of the Specimens

SB (Solid Brick Infill)
PB (Perforated Brick Infill)

At cycle 2, the load was applied to a maximum of 80 KN from each side of the specimen. At cycle 3, the load was applied to a maximum of 120 KN from each side of the specimen. At 120 KN (toward negative direction) load, diagonal shear cracks were visible along the secondary diagonal of the wall.

In cycle 1, the load was applied up to a maximum of 40 KN on each side of the specimen. In cycle 2, the load was applied up to a maximum of 80 KN from each direction of the specimen. In cycle 3, the load was applied up to a maximum of 120 KN from each direction of the specimen.

In cycle 4, the load was applied to a maximum of 160 KN from each direction of the specimen.

Figure 4.1: Hysteretic load-displacement curve for SB.

Comparative Study

Comparison between SB and SBL
Comparison between PB and PBL
Comparison between SB and PB
Comparison between SBL and PBL

On the other hand, at the first cracking of the frame, SBL showed about 3 times more displacement and 49% less stiffness than SB. Maximum stiffness and stiffness at maximum displacement at each cycle of SB and SBL are presented in Figures 4.25 and 4.26. On the other hand, at the first cracking of the frame, PBL showed 39% less displacement and 9% more stiffness than PB.

The maximum stiffness and stiffness at maximum displacement per cycle of PB and PBL are presented in Figures 4.30 and 4.31. The maximum stiffness and stiffness at maximum displacement per cycle SB and PB are presented in Figures 4.35 and 4.36. On the other hand, PBL showed 60% less displacement but 66% more stiffness than SBL at the first crack of the frame.

Maximum stiffness and stiffness at maximum displacement per each cycle of SBL and PBL is shown in Figures 4.40 and 4.41.

Figure 4.22: Relation between lateral load and story drift.

Overall Comparison of All Specimens

An example calculation of storey drift, stiffness and cumulative energy dissipation for a sample (sample SB is taken as an example) is shown in Appendix I.

Figure 4.42: Relation between lateral load and story drift.

CONCLUSIONS AND RECOMMENDATIONS

Introduction

Conclusions from the Experiments

SBL showed 81% more displacement before failure than SB and PBL showed 52% more displacement before failure than PB. For example, PB showed 33% less stiffness before failure than SB and PBL showed 9% less stiffness before failure than SBL. Similarly, SBL showed 41% less stiffness before failure than SB and PBL showed 19% less stiffness before failure than PB.

Both the perforated clay brick and the lintel are effective in improving the energy dissipation performance of the specimens. For example, PB dissipated 8% more cumulative energy than SB and PBL dissipated about 4 times more cumulative energy than SBL. Similarly, SBL dissipated 46% more cumulative energy than SB and PBL dissipated about 5 times more cumulative energy than PB.

The pattern that has perforated clay brick and lintel is the most efficient structure in terms of ductility and energy dissipation.

Recommendations for Future Study

The sample containing solid mud bricks and no lintels is the most effective structure in terms of stiffness. Perforated clay bricks were used in this experiment, but their hole was not used to increase structural integrity. In the future, there is great scope to utilize these holes by inserting reinforcement along them along with partial or full joints.

Considering this incident, high strength mortar or rich mix mortar can be used in the future study. In this study, it was observed that the infill masonry wall tended to separate from the frame under cyclic loading due to the weak mortar joint. In the future study, this joint can be reinforced in many ways, such as using dowel rods.

But in the future, special concrete such as ultra high performance concrete is used.

M., (2002) ‘Finite Element Analysis of Infilled Frames’, The American Society of Civil Engineers (ASCE), Journal of Structural Engineering, Vol. Summary of a Large- and Small-Scale Unreinforced Masonry Infill Test Program”, The American Society of Civil Engineers (ASCE), Journal of Structural Engineering, Vol.129, No. 12, pp. A., (2018) ―The Geo-Genetic Status of Earthquake-Related Hazards and the Role of Human and Policy Dimensions in Mitigating Impacts', Environmental Hazards, Vol.17, No.4, pp.

N., (1996) ―Experimental Evaluation of Masonry Filled AB Frames‖, American Society of Civil Engineers (ASCE), Journal of Structural Engineering, Vol. B., (1997) ―Finite Element Modeling of Masonry Filled AB Frames‖, American Society of Civil Engineers (ASCE), Journal of Structural Engineering, Vol. C., (2014) ―Design of Reinforced Concrete Filled Frames‖, The American Society of Civil Engineers (ASCE), Journal of Structural Engineering, Vol.

Smith, B.S., (1966) ―Behavior of the Square Infilled Frames‖, The American Society of Civil Engineers (ASCE), Journal of the Structural Division, Vol. 1991) ―Analise en ontwerp van hoë geboustrukture‖, John Wiley & Sons, inc., A Infilled-Frame Structures, hoofstuk.

Appendix-A

YIELD STRENGTH AND ULTIMATE STRENGTH OF REINFORCEMENT

Appendix-B

COMPRESSIVE STRENGTH OF SOLID AND PERFORATED CLAY BRICK

Appendix-C

ABSORPTION CAPACITY OF SOLID AND PERFORATED CLAY BRICK

Appendix-D

COMPRESSIVE STRENGTH OF MORTAR CUBE

Appendix-E

COMPRESSIVE STRENGTH OF CONCRETE CYLINDER

Appendix-F

COMPRESSIVE STRENGTH OF SOLID AND PERFORATED BRICK PRISM