245 COMPARATIVE STUDY ON STRUCTURAL ANALYSIS AND DESIGNING OF A RCC AND
STEEL BUILDING FRAME Deepak Kumar Dubey
Research Scholar, (Structural Engineering), Department of Civil Engineering, School of Engineering and Technology, K.K. University, Nalanda, Bihar
Mr. Deepak Kumar
Assistant Professor, (Structural Engineering), Department of Civil Engineering, School of Engineering and Technology, K.K. University, Nalanda, Bihar
Abstract— The comparative study of this paper reviews the analysis and design of steel members or sections to be used in construction of buildings in steel structure and its comparative study with RCC building. Latest techniques are studied to perform more fast and precise work on the site. In this work a G+4 storied apartment whose ground floor is considered as a parking lot, is situated in Buxar. Buxar city belongs to the earthquake zone-III. As the ground floor is considered as a parking floor, other floors have the same plan consisting of 8 2BHK flats on each floor. As a 4 storied building is earthquake dominating so keeping the wind analysis deprived and analyzing the building for various combinations of earthquake loads. Provision of IS: 1893(Part 1)-2016 is reviewed using software for the analysis of models. As earthquake forces are situated with inertia, they are related to the mass of the structure and so reducing the mass inevitably leads to lower seismic forces. The design work is using IS: 800-2007and IS: 456:2000 for steel and RCC work. This study consists of comparison of structural parameters such as shear force, reactions, displacements, moments, story drift, etc. at various junctions of both buildings.
Structural Stability of both buildings will be compared to get the clear idea and the behavior of the buildings under earthquake conditions. As the steel buildings are at risk of fire, fire provision is studied. The consumption of structural steel in construction of residential and commercial buildings is very low in India as compared to many other developing countries in the world. Experience of other countries which select structural steel as core and leading material indicates that it has many positive factors such as inherent strength, is biodegradable and recyclable with potential future applications.
Analysis and design of buildings for static forces is a routine affair these days because of the availability of affordable computers and specialized programs which can be used for the analysis. On the other hand, dynamic analysis is a time consuming process and requires additional input related to the mass of the structure, and an understanding of structural dynamics for interpretation of analytical results.
Keywords: Structural Analysis, Designing of Rcc, Steel Building Frame, Structural Stability, Shear Force, Reactions, Displacements, Moments, Story Drift.
1 INTRODUCTION
Developing countries like India are flourishing in different sectors. Out of which Infrastructure is one of the diverse sectors. But when discussion is specifically about buildings it comprises industrial, commercial, institutional and residential buildings. Industrial buildings are mainly constructed in steel structures while residential and commercial buildings are constructed in RCC. In this modern era the buildings are constructed to fulfill our basic needs and to provide better serviceability. It is not an issue to construct merely a building, however, it is important to build an efficient building which will serve for many years without any failure. In the 21st century due to proliferation in the
population the land area is decreasing day by day. So, to overshadow this problem the type of construction preferred nowadays is vertical expansion i.e., high rise buildings are constructed everywhere. In the analysis of such buildings various factors are needed to be considered such as its own height, SBC of soil, type of soil, self-weight of many materials, etc. Low rise building structures are surrounding and most of the building structures lie under the category. So, for these structures RCC members are used widely because the construction becomes quite convenient and economical. But since the population is growing exponentially and the land is limited, there is a need for vertical growth of buildings in the coming
246 future. For external forces that act on the
building, the beam, column, and the reinforcement should be designed in such a way that it efficiently counteracts these forces without any damage. This type of analysis is tedious for us to do manually, so another way is required, which is fulfilled by STAAD Pro.STAAD pro makes such analysis and design quite easy to carry out.
Steel is one of the most widely used materials for building construction in the world. Its inherent strength, toughness and high ductility are the characteristics which make it ideal to use it for building construction. When compared to other materials, steel has the highest rate of recyclability and recent research in earthquake regions shows that steel is the most reliable structural material against seismic loads. Its comparative study is to evaluate whether steel structure is feasible in terms of structural performance, construction time, durability, etc. RCC can take up immense compression but is weak in tension whereas steel is good in Withstanding both tension and compression. This is one Construction technique that made Construction very easy and brought a boom to the field of Construction. Every component is designed according to the load it carries and its position in the Structure. The study of the design of RCC and steel will help in understanding the basics of RCC and steel structure design and the method of its implementation.
Fig.1 Typical RCC Frame
Fig.2 Typical steel Frame
A noticeable movement of the surface of the earth is known as an earthquake. They are the result of an unexpected sudden release of enormous amounts of energy in the earth‘s crust which in turn generates seismic waves.
India is divided into 4 seismic zones according to the Indian earthquake zoning map. The four seismic zones are zone II, III, IV & V in which zone has lowest level of seismicity and zone V has highest level of seismicity. No structures will completely resist seismic forces without damage. Most of the structures will undergo minor or major damage due to the earthquake. The damage to the structure may be minor if the magnitude of the earthquake is small, whereas the structure may collapse if the magnitude of the earthquake is very high.
Therefore, nowadays all high rise buildings and some low rise buildings are also designed for earthquake resistance.
1.1 RCC Structural Frame
Construction, analysis and design of Commercial and residential building is influenced by many factors, including durability, long life and aesthetics. Now the method which is widely used in surroundings is Reinforced Cement Concrete (R.C.C.). In an RCC framed structure, the load is transferred from a slab to the beam, then to the columns, further to the lower columns, and finally to the foundation which transfers the load to the soil. The walls are constructed after the frame is prepared, most tall buildings use RCC technology.
This conventional method of RCC structure is best and durable, but in rural or some semi-urban localities people compromise with the quality of concrete which actually needs to be used. If it happens so, the building in its design life lacks in serviceability. Continuity and Speed of construction is also a factor of RCC. An over dependence on concrete is alarming to the environment. Once the building life is completed it is demolished and the remaining waste concrete is non- degradable and cannot be recycled. So it is important to find alternative options.
Reinforced Cement Concrete (RCC) occupies a leading position In modern construction.
Proper reinforced Concrete construction depends upon Understanding of the action of Structure, limitation and characteristics
247 of materials that are used in construction.
In Rcc framed Structure buildings the floor area is about 10% to 12% greater compared to a load bearing walled buildings. Hence, this type of building is preferably economical where the value of land is very high. Normal earthquake effects can also be resisted by providing required further design. Maintenance cost is also minimum which can be ignored and faster construction work saves time and early finishing of projects. Common examples of standard mixes are M20, M30, M40 concrete, where the number refers to the strength of the concrete in n/mm2 or newtons per square millimeter. Therefore M30 concrete will have a compressive strength of 30 n/mm2. A standard mix may also specify the maximum aggregate size.
Aggregates are the stone chips used in concrete. If an engineer specifies M30 / 20 concrete, he wants M30 concrete with a maximum aggregate size of 20mm.
Fig.3 RCC Structural Frame 1.2 Steel Structural Frame
Steel buildings first gained popularity in the early 20th century. Their use became more widespread during World War II and significantly expanded after the war when steel became more available. Steel buildings have been widely accepted, in part due to cost efficiency. The range of applications has expanded with improved materials, products and design capabilities with the availability of computer aided design software. Steel structure is a need to make it possible in construction of residential and commercial buildings also. It is used on a large scale in many construction areas like the commercial and industrial sector. Steel framed structure can overcome the above mentioned flaws. The steel frame structure section which will be formed will not be much heavier, either they can be easily transported from plant to construction site or can be fabricated on site. The most important advantage and best thing is that
the speed of construction will be much faster than other prevailing work.
Compared to the other structural building materials in use today steel is the most used and versatile material for engineering construction. Steel being lightweight it has supremacy, that steel structures are generally light in comparison to those constructed using other available materials.
The durability and potency that steel provides is not matched by concrete or wood. A steel building is a metal structure fabricated with steel for the internal support and for exterior cladding, as opposed to steel framed buildings which generally use other materials for floors, walls, and external envelope. Steel buildings are used for a variety of purposes including storage, work spaces and living accommodation. They are classified into specific types depending on how they are used.
Fig. 4 Steel Structural Frame 1.3 Objectives
To perform structural analysis and design G+4 storied apartment building in steel structural system and its comparative study with conventional RCC structure.
To study the behavior of steel structure against dead load, live load, seismic load and their various combinations.
To study the variation in results of both structural systems and evaluate it to get satisfactory outcomes.
To study comparison of both the systems in aspect of structural performance, construction methodology and economy of project.
To study the various types of forces during their lifetime, such as static forces due to dead and live loads and dynamic forces due to the wind and earthquake.
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To study which structure is better, RCC or Steel.
To study the bending moment of RCC and steel structure.
To study the shear force of RCC and Steel structure.
To study the maximum displacement, support reaction in the structure
1.4 Methodology
To conduct the intended research work, an architectural layout plan of a G+4 story residential (apartment) building has been prepared.
Following the plan, a RCC structure with beam supported two-way and one-way slab floor system is formed.
Again following the same plan, steel structure with steel girder beam floor topping RC slab on corrugated steel deck is formed. Hollow rectangular sections are used as steel columns.
Then three dimensional structural modeling and static and dynamic analysis have been performed using commercial software for the two types of structural system.
Loads are assigned as per different parts of IS 1893. Load combinations are generated accordingly.
From analytical results,
RC structure is designed using the limit state of design method as per IS 456:2000.
Steel structure is designed as per IS 800:2007, IS 806:1968, IS 808:1989, IS 4000:1992.
Complete construction cost excluding electro-mechanical cost has been prepared. Comparison of structural behavior, construction method, and other related parameters have been prepared to evaluate a better/ effective structural system for the building used for this research.
2 LITERATURE REVIEW
Saadatmanesh. al. (1994) Confinement reinforcement is generally applied to compressive members as lateral reinforcement with the aim of increasing their strength and durability. In addition
lateral confinement payments slippage and buckling of the longitudinal enforcement.
Frangou and Pilakoutas (1995) Lateral reinforcement can be provided by using circular hoops, rectangular ties, jacketing by steel, FRP, ferrocement, etc.
Because the total cost of replacement of the vulnerable structures is so overwhelming, the development of innovative rehabilitation and strengthening techniques is required to extend the life expectancy of many existing buildings and bridges. A number of repair and strengthening techniques are currently in use of reinforcement concrete structures.
Unfortunately the majority of them are very expensive, time consuming and require the interruption of the structure while works are carried out.
Dilgeret. al. (2000) Recent earthquakes have revealed an urgent need to develop retrofit techniques for the existing buildings and bridges designed in accordance with the old seismic codes so as to meet the requirements of current seismic design standards. Some of the common problems revealed by earthquakes such as Kobe (Japan 1995), Athens (Greece 1999) and Kocaeli (Turkey 1999) include inadequate confinement of concrete, leading to shear, Anchorage and splice failures. It is well known and proven that lateral confinement improves the strength and durability of concrete.
Sonuvaret.al.(2004) Nowadays, most of a strengthening strategies are based on global strengthening schemes as per which the structure is usually strengthened for limiting lateral displacement in order to compensate for the load durability in this scheme's global behavior of the system is transformed. Another approach is modification of the deficient elements to increase ductility so that the deficient elements will not reach their limit state conditions when subjected to design loads However, the latte strategy is more expensive and harder to implement in case of many deficient elements which is the region that the global strengthening methods have been more popular than element strengthening.
Albanese et.al.(2006) Among the global strengthening method addition of RC In infill is the most popular one. Many researchers have focused on this subject and found that in the subject and found that installation of RC infills greatly
249 improve lateral load capacity and stiffness
of the structure even in case of application to damaged buildings the infill method yields satisfactory results.
Kaplan et. al.(2009) The precast panel infill method, which causes less disturbance for the building occu-pants, has been investigated and found to be an efficient solution for the strengthening of existing structures. Despite causing some architectural problems some other researchers perpendicularly installed RC shear walls outside the building. The kind of shear walls were also applied to precast skeletal structures with an external at the roof level.
T.Nagaeet.al.(2012) Analyzed a three- dimensional earthquake simulation test on full-scale four-story, prestressed concrete building was conducted using the E-Defense shake table facility. The seismic force resisting system of the test building consisted of post tensioned (PT) frames in one direction and two unbonded PT precast walls in the other direction.The test building was subjected to several earthquake ground motions, ranging from serviceability level to near collapse.
V.GKiran Kumar et al. (2014) explained through their paper the use of ETABS for the high rise building load calculation, wind load calculations, seismic load calculation and the design of a postrensioned slab can be studied. With the use of post-tensioning methods, the thickness of the slab is reduced. If the thickness of the lab is reduced, this creates a chain reaction i.e number of columns and beams is reduced which leads the structure being more economical and eco friendly.
B.Anjaneyulu et al. (2016) explained the importance of the flat slab in India as this construction is developing technology. Flats slap can be built by both conventional reinforced concrete as well as post-tensioning. However for a span up to 10 meters confessional concrete design is used in India.
Jnanesh Reddy et al. (2017) Gave us a compression between post tensioned and RCC flat slab in a multi-storey post tensioning building. The need of concrete in RCC flat slab each is comparatively more than PT slab. Cost of steel required is also more than the combined price of steel and tendons in PT slab construction. Stiffness and strength of structure will also be more
than the modern of the RCC Flat slab. As thickness is reduced in PT slab aesthetic looks can be increased and also be structured lighteras the dead load gets reduced.
3 MATERIALS DESCRIPTION
(i) Rcc Building- Structural Components In RCC Framed Structure:
Slab: The Flat Roof Of A Storey Is Known As A ‗Slab‘.
Beam: The Peripheral Horizontal Members Supporting The Slab Are Referred To As
‗Beams‘.
Plinth Beams: In RCC Framed Structure, The Beam On The Ground Level Or Plinth Level (The Lowest Liveable Level) Is Known As ‗Plinth Beams‘.
Column: The Vertical Members Supporting The Beam Are Referred To As ‗Columns‘.
Foundation: The System Under The Ground That Transfers All The Weight Of The Structure To The Soil Known As
‗Foundation‘.
Cantilever: A Slab Or A Beam Is Supported Only On One Side And Projected
Horizontally On The Other Side, Called A Cantilever Slab Or Beam, E.G. Balconies, Lofts And Canopies. Following four materials are required for making R.C.C:
1) Cement 2) Aggregates 3) Steel 4) Water 4 ANALYSIS
The apartment building is modeled in commercial software. This building is modeled for two different types of structural systems and the results of analysis are described and are compared between.
Here the present works (problem taken) are on a G+4 storied regular building. These buildings have the plan area of 63.2m x 29.5m with a storey height 3.6m each and depth of foundation is 1.5 m. & total height of chosen building including depth of foundation is 18 m. The static and dynamic analysis has done on computer with the help of STAAD-Pro software using
The parameters for the design as per the IS- 1893- 2002-Part-1 for the zones- 3 and the post processing result obtained has summarized.
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The proposed work of the project includes a residential building at Nashik to be analyzed and designed for comparative study. Below shown is a 3D model of analysis in commercial software and the architectural plan of a typical flat as rest others are similar to it..
Fig. 5 3-D Model in Software
Fig. 6- RCC Beam Layout For Typical Flat
5 RESULTS AND DISCUSSION
(i) 5.1 Maximum Displacement ( For G + 4)
(ii) Maximum Reinforcement (for G + 4)
6 CONCLUSION
On the following work carried out we conclude that,
Firstly, the structure analysis of similar building models was done for RCC structure and steel structure.
Results from the analysis of two identical models were compared based on their mass by Material, storey drift, base shear, storey displacement and so on.
Steel structures are expected to show superior performance under earthquakes due to higher ductility than the conventional RCC structure.
Construction of Structure with RCC consumes large amount of Raw materials. hence the mass materials for RCC is greater than for steel Structure.
Axial forces are lower in steel structure due to lower weight of steel structure compared to RCC structure. Due to this the reaction obtained in steel is lesser than RCC, which gives better response during earthquake conditions.
According to the results of analysis when maximum displacement and story drift is compared it is quite higher in steel structure than in RCC. This shows that RCC is more durable and sturdy.
Bending moment and Shear force in beams of RCC structures is more as compared to that of steel structures.
Preferred boards fire protection system simultaneously helps the building for resisting fire cause and hides all the exposing structural members.
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Center of mass was the same for both and Center of rigidity was more for Steel.
Maximum storey stiffness was greater for Steel than concrete.
Story displacement was more for RCC Frame model than Steel frame model.
Base shear is considerably less for Steel structures as compared to RCC, which gives better response during earthquakes.
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