Performance and Comparing RCC beam with Post Tension beam using Dynamic Load Condition of Larger Span Structure

Performance and Comparing RCC beam with Post Tension beam using Dynamic Load Condition of Larger Span Structure

Vijay K More

PG Student

Dept. of Civil Engineering, SDMCET, Dharwad, India

Basavaraj Gudadappanavar

Asst. Professor, Dept. of Civil Engineering, SDMCET, Dharwad, India

Abstract:- In ordinary Reinforced cement concrete beam, compressive stresses are taken up by concrete and tensile stresses by steel alone. The concrete below the neutral axis is ignored since it is weak in tension. Although steel takes up the tensile stresses, the concrete in the tensile zone develops minute cracks. The load carrying capacity of such concrete sections can be increased if steel and concrete both are stressed before the applications of external loads. This is the concept of prestressed concrete. Internal prestressing can be done by two methods Pre- tensioning and Post-tensioning. In Pre-tensioning system, the tendons are first tensioned between rigid anchor blocks cast on ground or in a column or unit-mould type pre-tensioning bed, prior to the casting of concrete in the moulds. In Post- tensioning, the concrete units are first cast by incorporating ducts or grooves to house the tendons. When the concrete attains sufficient strength, the high-tensile wires are tensioned by means of jack bearing on the end face of the member and anchored by wedges or nuts. The space between the tendons and the duct is generally grouted after the tensioning operation. Referring particularly to post tensioning applications, it is generally recognized how it opens the possibility to improve economy, structural behaviour and aesthetic aspects in concrete solutions. As in modern days post tensioning has been most economical method when compared to the RCC works. The study is subjected to evaluation of performance of RCC deep beam and PT beam slab with multi-storey building system with seismic loading performance using analysis tool ETABS.

Keywords RCC Beam, ETABS, PT Beam, Storey displacement, Storey Shear, Storey Drift.

1. INTRODUCTION

   RCC Structures are commonly utilized for residential and industrial buildings in Asian countries. For small span buildings, PT beams are rarely used. There was a huge disadvantage of expert staff for Pre-Stressing job two decades ago. However, there are currently a significant number of agencies for the execution of a comparable work. Due to deflection limitations in RCC Beams, the depth of the beam increases as the span increases. The depth of the beam is reduced in pre-stressed sections, therefore pre-stressed beams are less expensive for long spans.

   PSC is the most recent main type of structural engineering construction introduced. Because the technology is currently available on the market in both developed and developing countries, it has become a well-established construction technique. Today, prestressing is employed in buildings, subterranean structures, communication towers,

   floating storage and offshore structures, power plants, apparatus boats, and a variety of bridge systems.

   The primary style goals for structural engineers are safety, practicability, economy, and current lawfulness of style. Engineers and designers must comprehend the proper use of posttensioned concrete as well as the effects that will result when choosing a structural construction system. If properly evaluated and constructed, concrete buildings composed of high-quality components will offer a superior combination of durability, sound management, and fireplace safety in today's construction market. Given the current market aspects of value options, material availability, and lower floor-to-floor heights, as well as market developer finance, Concrete is generally regarded as a more cost- effective material than steel. Concrete that generates internal stresses of sufficient magnitude and distribution to significantly offset the stresses caused by a given external force.

2. OBJECTIVES

   • To analyze the dynamic performance of RCC beam and PT beam of multistorey building system.

   • To compare the results of Base Shear, Storey Displacement, Storey drift of RCC beam with PT beam of the multistorey building system.

3. METHODOLOGY

   This chapter describes the standard step-by-step method for modelling the two different regular structure with RCC Beam and PT Beam

   • Model Type 1- RCC Structure

   • Model Type 2- Post-Tension Structure

   Architectural Drawings

   Creating grid Lines

   Defining Material Properties

   Flow Chart

   Defining Section Properties

   Slab Details

   Assigning Properties

   Definition and assigning Loads

   Assigning Supports

   Defining Response Spectrum

   Analyzing the building

   STEP-BY-STEP METHOD FOR MODELLING OF THE STRUCTURE

   Number of Stories	G+10
   Plan Dimension	16*15
   FL to GL	1.5m
   F to F height	3m
   Materials	M40 grade concrete and Fe500 Steel
   Size of Column	300mm X 800mm
   Size of Beam	500mm X 500mm
   Slab Thickness	150mm
   Seismic Zone	Zone IV

   Step1: Collection of data related to RCC and PT structure considering software implementation

   Step2: Modeling Both RCC and PT Structures in ETABS

   Fig-1: Plan of RCC Building

   Fig-2: Plan of PT Building

   Fig-3: Storey Data

   Step 3: Generating Material Properties (M40 & HYSD500)

   Fig-4: M-40 Concrete

   Fig-5: HYSD500

   Step 4: Creating beam and column section of the structure

   Fig-6: Section Properties of a Frame

   Step 5: Drawing Tendons to the beams for PT Structure

   Fig-7: Tendon Vertical Profile

   Fig-8: Tendon Load

   Fig-9: Tendon Losses

   Step 7: Defining Seismic Load

   The loading due to earthquake is assessed based on the provisions of IS: 1893-2016

   Seismic zone = IV

   Zone Factor = 24

   Response reduction factor = 5

   Importance facto = 1.2

   Method of analysis = Response Spectrum Analysis

   Step 8: Load Combinations:

   Fig-10: Load Cases

   Fig-11: Details of Load combinations for RCC structure

   Fig-12: Details of Load combination for PT structure

   STEP 9: Defining Response Spectrum Function I.S. 1893: I:2002

   A designer is rarely concerned with the building's reaction at all times; maximal response is enough information to design a suitably strong structure. This approach graphs the relationship between maximum spectral acceleration and A construction of many historical periods is created for some ground. Every occurrence of acceleration and structural response Time is not taken into account. It is the response spectrum approach. Method of linear dynamic analysis This procedure entails the only the greatest displacement values are calculated and member forces in each vibrational mode This technique utilizes the average of many smooth design spectra earthquake movements Different earthquakes will have different results. response spectrum, but for the convenience of the structural engineer IS 1893:2002 specifies a general-purpose response spectrum which is deduced from considering few big earthquakes from past.

   Fig-13: Response spectrum as per I.S. 1893: I:2002

4. RESULTS AND DISCUSSION

   In the present study, RC Structure and PT structure of same structural properties are modelled and analyzed using ETABS

   2019. Structures are analyzed for Response Spectrum analysis methods as per IS 1893 2002. Core results are extracted and presented in the present chapter 4 as below and conclusions are made in chapter 5 based on the brief discussion of results.

   Following Graphs demonstrates the max Storey displacement, Storey Drift, Time Period, Base Shear of PT Structure and RC Structure carried out by Response Spectrum Analysis (RSA)

   1. STOREY DISPLACEMENTS

      Chart-1: Storey vs Displacement

      Storey displacement results are presented in the form of graphs in Chart 1. From the results, it can be seen that structures with PT beams have fewer displacements than structures with RCC beams. A RCC structure has a maximum displacement of 26.517mm at roof whereas a PT structure has a maximum displacement of 19.058mm, which is 28.13% less than the RC structure.

   2. STOREY DRIFT

      Chart -2: Storey vs Drift

      Storey drift results are presented in the form of graphs in Chart 2. From the results, it can be seen that structures with PT beams have less storey drift than structures with RCC beams. The max drift that occurs in the RC structure is

      0.001178mm, where as in the PT structure it is 0.000837, i.e., a 29% decrease.

   3. BASE SHEAR (KN)

   	PT Structure	RC Structure
   Base Shear (KN)	668.3024	954.477

   TABLE 1 BASE SHEAR

   Base Shear values are shown in Table -1, From the results it can be seen that Base Shear value decreased by 30% in PT structure.

   STOREY SHEAR

   Chart-3: Storey shear

   Storey Shear is shown in chart-3, from the results it can be seen that, maximum storey shear occurs at storey 10. The PT structure has a Soc 21.67% lower storey shear than the RCC structure at storey10.

5. CONCLUSIONS

The following conclusions are drawn from the present study:

• As shown in Chart-1, PT structures have lower storey displacements when compared to RCC structures.

• As shown in Chart-2, PT structures have lower storey drift when compared to RCC structures.

• When the RCC beam is replaced with a PT beam, the base shear decreases as shown in Table 1.

REFERENCES

[1] Ankit Sahu, Prof. Anubhav Rai, Prof. Y. K. Bajpai Cost & Constructional Comparison Between Rcc & Prestressed Beams Spanning 16m. International Journal of Scientific & Engineering Research, Volume 5, Issue 6, June-2014 436 ISSN 2229-5518..

[2] Vaibhav G Tejani, Hitesh K Dhameliya, Jasmin Gadhiya Review for Study of Prestressing Systems for all Structural Element in IJSRSET | Volume 1 | Issue 6 | Print ISSN: 2395-1990 | Online ISSN: 2394- 4099K. Elissa, Title of paper if known, unpublished.

[3] IS – 456 Code of practice for plain and reinforced concrete [4] IS 1343 1980: Code of Practice for Prestressed Concrete

[5] IS: 1893 (Part-1) 2016, Indian Standard for Earthquake Resistant Design of Structures (6th revision), Bureau of Indian Standards, New Delhi, India.

[6] IS 875 (Part-5) 2016, Design Loads (other Than Earthquake) For Buildings and Structures Bureau of Indian standard, New Delhi, India.

[7] IS 875-Part 1 2016: Design Loads (other Than Earthquake) For Buildings and Structures Bureau of Indian standard, New Delhi, (2016).

[8] IS 875-Part 2 2016: Design Loads (other Than Earthquake) For Buildings and Structures Bureau of Indian standard, New Delhi, (2015).