Health Monitoring of Flat Slab Using NI Labview

Abstract

Structural health monitoring techniques are widely used for detection of risky zone or faults or defects on the body whether it may be Building, bridges, steel structure like truss and towers, and also in the machines and in equipments like plane, trains etc. Wired techniques are mostly useful for the bodies which are small and in which the structure is physically in touch with the sensors whereas in wireless technique, the sensors are not in physically in touch with the structure. Sensors are then to be fixed at appropriate location of the designed flat slab. For monitoring the considered flat slab program is done using NI LabVIEW. The sensors are connected to the computer via My DAQ. The slab is then monitored for the working loads and the data is obtained in the form of graphs.

Introduction

I. INTRODUCTION

Civil infrastructures, which include bridges, buildings, pipeline, furnace and transition lines, begin to deteriorate once they are built and operated. Maintaining safe and non-viable civil infrastructures for daily use is important to the well-being of all of us. Knowing the integrity of the structure in terms of its age and operation, and its level of safety to withstand infrequent but high forces such as overweight trucks, earthquakes, tsunami, and hurricanes is important and necessary. The process of determining and  tracking structural integrity and identifying the nature of damage in a structure is often referred to as health monitoring

II. MATERIALS USED

The various material used in the preparation of concrete specimen are collected and studied for various parameters. The following materials are used for making the flat slab specimen. Ordinary Portland Cement: conforming to IS456:200-53 grade

1. Graded Fine Aggregate
2. Graded Coarse Aggregate
3. Water
4. HYSD Bars
5. Super plasticizer

a. Ordinary Portland Cement

The cement is the binding material. It consist of grinding the raw materials.

b. Fine Aggregate

The material smaller than 4.75 mm size is called fine aggregates. River sand conforming to grading zone of IS 383-1970 was used as fine aggregate

c. Coarse Aggregate

Locally available well graded granite aggregates of size passing through 16mm.the maximum size of the well graded coarse aggregate is 20mm.

d.. Water

Portable water has been used for casting the specimen. The water is free from oil, acids, alkalis and has a water soluble chloride content of 140 mg/lit. as per IS456:2000, the permissible limit for chloride is 500 mg/lit for reinforced concrete.

e. Steel

High Yield Strength Deformed bars of Fe 415 conforming to IS 1786 has used.

f. Super Plasticizer

Super plasticizer Bostic 2 in 1 has been use in our concrete mix to increase the workability of the mixture as well as to decrease the water requirement. This in turn decreases the water cement ratio increasing the compressive strength of the concrete. The admixture is added at the rate of 200ml/50kg of cement.

g. Sensors

The following parameters are analyzed in the considered flat slab.

• Temperature – LM35 (Continuous Monitoring)
• Strain - Electrical Strain Gauge (Continuous Monitoring)
• Corrosion – Determined by open circuit potential using Half-cell and calomel reference electrode. (Non Continuous Monitoring)

Conclusion

The considered flat slab model has been successfully monitored continuously under various working loads and it seems that the slab is safe as per the Indian Standard norms. The slab is designed to withstand only 5kN/M of load. When 5kN/M load is applied to the flat slab (ie. Maximum load is provided,500kg) the deformation is very little. The strain value obtained was under the tolerable limit. So the load has been doubled to 10 kN/M (1000kg / 1 ton), in this case the strain value obtained is 0.0028, which is lesser than the acceptable 0.0035 range. The equivalent deflection value obtained by using sensor to that of 10kN/M load is 0.014mm, which when compared by the deflectometer gave a value of 0.01mm thus by using electrical strain gauge much accurate results could be obtained to the ranges upto 10-3 decimal points. The corrosion monitoring of the flat slab specimen also holds to be quiet normal as per ASTM C876-91 (Reapproved 1999) codal provision. Thus structural health monitoring proves to be an effective method to analyze the life of the structure without any destructive tests and it proves well to be an effective alternate for non-destructive testing methodologies. Indeed SHM systems are gaining more important day by day especially on public structures like Bridge, Towers, Transportation means for the human safety and environmental sustainability approach too.

References

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Copyright

Copyright © 2023 M. Nithya, S. Narmadha, R. Vanitha. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.