This document compares the economical aspects of long span flat slabs and grid slabs. Flat slabs are modeled using the direct design method, while grid slabs are modeled using plate theory. The cost is calculated based on the quantity of steel, concrete volume, and formwork costs. For spans ranging from 5-13 meters, the cost per square meter is determined for different slab designs. The results show that flat slabs are more economical for smaller spans, but grid slabs become more economical for longer spans above 9 meters.
a space frame or space structure is a rigid, lightweight, truss-like structure constructed from interlocking struts in a geometric pattern. Space frames can be used to span large areas with few interior support
a space frame or space structure is a rigid, lightweight, truss-like structure constructed from interlocking struts in a geometric pattern. Space frames can be used to span large areas with few interior support
Portal frame construction by Rhythm MurgaiRhythm Murgai
This is the seconed part of slide from Portal fram.
If you want to see the previous slide,then go to my account and search for portal frame.
For queries : http://www.facebook.com/rhythmmurgai
or +919872297936
FOLLOW US ON http://www.instagram.com/jsrkofficial
Definition Where this system can be used
Features of the Grid Slab
Decorative grid slabs in historical structures
Types of Grid Slab
Comparison: Long Span Structures
Construction
Technique
Formwork Required
Reinforcements Details
Modification in Grid Slab for Utility
Services Provided in Grid Slab
Benefits
Iconic Landmarks using Grid Slabs
The lecture is in support of:
(1) The Design of Building Structures (Vol.1, Vol. 2), rev. ed., PDF eBook by Wolfgang Schueller, 2016: chapter 9.
(2) Building Support Structures, Analysis and Design with SAP2000 Software, 2nd ed., eBook by Wolfgang Schueller: chapter 11.
A presentation with exhaustive information about the general idea of formwork, the various types, the newest introductions and a comparative study between the conventional and modern-day formwork.
It also includes the study of causes of failure of formwork and the safety measures to be taken for preventing failure.
What are the types of structural steel framingnajeeb muhamed
Different types of structural steel framing systems for buildings such as skeleton, wall bearing and long span framing systems and their applications and configurations are discussed.
Portal frame construction by Rhythm MurgaiRhythm Murgai
This is the seconed part of slide from Portal fram.
If you want to see the previous slide,then go to my account and search for portal frame.
For queries : http://www.facebook.com/rhythmmurgai
or +919872297936
FOLLOW US ON http://www.instagram.com/jsrkofficial
Definition Where this system can be used
Features of the Grid Slab
Decorative grid slabs in historical structures
Types of Grid Slab
Comparison: Long Span Structures
Construction
Technique
Formwork Required
Reinforcements Details
Modification in Grid Slab for Utility
Services Provided in Grid Slab
Benefits
Iconic Landmarks using Grid Slabs
The lecture is in support of:
(1) The Design of Building Structures (Vol.1, Vol. 2), rev. ed., PDF eBook by Wolfgang Schueller, 2016: chapter 9.
(2) Building Support Structures, Analysis and Design with SAP2000 Software, 2nd ed., eBook by Wolfgang Schueller: chapter 11.
A presentation with exhaustive information about the general idea of formwork, the various types, the newest introductions and a comparative study between the conventional and modern-day formwork.
It also includes the study of causes of failure of formwork and the safety measures to be taken for preventing failure.
What are the types of structural steel framingnajeeb muhamed
Different types of structural steel framing systems for buildings such as skeleton, wall bearing and long span framing systems and their applications and configurations are discussed.
This document presents an example of analysis design of slab using ETABS. This example examines a simple single story building, which is regular in plan and elevation. It is examining and compares the calculated ultimate moment from CSI ETABS & SAFE with hand calculation. Moment coefficients were used to calculate the ultimate moment. However it is good practice that such hand analysis methods are used to verify the output of more sophisticated methods.
Also, this document contains simple procedure (step-by-step) of how to design solid slab according to Eurocode 2.The process of designing elements will not be revolutionised as a result of using Eurocode 2. Due to time constraints and knowledge, I may not be able to address the whole issues.
This resource material is exclusively for the purpose of knowledge dissemination for the use of Civil engineering Fraternity, professionals & students.
This file contains state of art techniques adopted & practiced as per IS456 code provisions for analysis design & detailing of flat slab structural systems.
The presentation aims to provide clear,concise, technical details of flat slabs design.
The presentation deals with structural actions & behavior of flat slabs with visual representations obtained through finite element analysis.
The knowledge gained can be used for designing building structures frequently encountered in construction.
The presentation covers an important feature of slab systems supported on rigid & flexible support & clearly demarcates the minimum beam dimensions required to consider the supports to be either rigid or flexible.
The presentation alsoincludes clear technical drawings to highlight the importance of detailing w.r.t. rebar lay out - positioning & curtailment. Typical section drawing through middle & column strips are also included for visualizing rebar patterns in 3 -d views.
This presentation is an outcome of series of lectures for undergrad & grad students studying in civil engineering.
My next presentation would be on Analysis & design of deep beams.
Kindly mail me ( vvietcivil@gmail.com) your questions & valuable feedback.
Determination of load transfer in reinforced concrete solid slabs by finite e...IOSR Journals
According to the ACI building code, the concrete slab can be divided into two types depending on
the ratio of the long side to the short side. Regarding the results of the ratio, the concrete slab can be divided as
one-way and two-way slabs. The main objective of this paper is to study the stress or moments distribution in
solid slab panel in its two directions and compare with ACI code assumption that the load is transferred mainly
in short direction and most of the load is transferred in one direction only if the ratio of the longer span to the
shorter span is greater than one. This will be discussed by analyzing one panel of solid slab using the computer
software SAP2000. Two types of panels will be used; the first one a panel that is supported simply on its four
sides and the second panel is supported only by four pin supports and beams. This paper shows that the gravity
load on the slab is transferred to long and short direction. This means that one-way concrete solid slab doesn't
exist and all concrete solid slabs work as a two-way concrete slab.
NONLINEAR FINITE ELEMENT ANALYSIS FOR REINFORCED CONCRETE SLABS UNDER PUNCHIN...IAEME Publication
This paper presents an implementation of a three-dimensional nonlinear finite element model for evaluating the behavior of reinforced concrete slabs under centric load. The concrete was idealized by using eight-nodded solid elements. While flexural reinforcement and the shear were modeled as line elements, a perfected bond between solid elements and line elements was assumed. The nonlinear behavior of concrete in compression is simulated by an elasto-plastic work-hardening model, and in tension a suitable post-cracking model based on tension stiffening and shear retention models are employed. The steel was simulated using an elastic-full plastic model. The validity of the theoretical formulations and the program used was verified through comparison with available experimental data, and the agreement has proven to be good. A parametric study has been also carried out to investigate the influence of the slab thickness on column-slab connection response
Effects of longer span floor system in the constancy of the multistoried stru...eSAT Journals
Abstract The main objective of this study is to investigate the structural integrity, stability and their comparison due to the effects of longer span floor systems considering some constancy in the multi-storied commercial and residential mixed-used structures. In recent times, mixed-use developments and buildings have created an up surging demand in perspective of relatively small area of lands like Bangladesh. But, the commercial developments consisting of underground basement required maximize serviceable column free open-floor spaces for more flexibility, marketability and uninterrupted executive car parking of the end-users. Now, the column free open-plan floor spaces, usually ranges from 18~27 ft, even up to 45 ft. or more [5], offers a bulky change in span length of the slab that results the longer span structure. Again, the longer span structure is directly related with the beam length which promptly affects the thickness of the slab as well as the sizes of beams, columns and the foundations. In this study, two different span lengths of the mixed-use structural Models are considered based on the economical range [18ft-30ft] of the RC floor systems. Then, both of the structural Models are compared based on the following parameters: design aspects, reduction in the number of components, sizes & thickness, weight of steel and volume of concrete. It is found that, longer span structure keeps highest effects on the RC columns and increase in size by 104.3%. This study will also be helpful for a designer to select an appropriate size of the structural components within the economical ranges of these types of particular RC structures in future Keywords: Regular Span Structure, Longer Span Structure, Flat Plate Slab, Flat Slab, Edge Supported Slab Andmat Foundation.
Between Filth and Fortune- Urban Cattle Foraging Realities by Devi S Nair, An...Mansi Shah
This study examines cattle rearing in urban and rural settings, focusing on milk production and consumption. By exploring a case in Ahmedabad, it highlights the challenges and processes in dairy farming across different environments, emphasising the need for sustainable practices and the essential role of milk in daily consumption.
Dive into the innovative world of smart garages with our insightful presentation, "Exploring the Future of Smart Garages." This comprehensive guide covers the latest advancements in garage technology, including automated systems, smart security features, energy efficiency solutions, and seamless integration with smart home ecosystems. Learn how these technologies are transforming traditional garages into high-tech, efficient spaces that enhance convenience, safety, and sustainability.
Ideal for homeowners, tech enthusiasts, and industry professionals, this presentation provides valuable insights into the trends, benefits, and future developments in smart garage technology. Stay ahead of the curve with our expert analysis and practical tips on implementing smart garage solutions.
1. Study on Economical Aspects of Long Span Slabs
Ibrahim. S. Vepari
M.E Student, Applied Mechanics Department,
L. D. College of Engineering,
Ahmedabad, India
ebrahim.vepari@gmail.com
Dr. H.S.Patel
Associate Professor, Applied Mechanics Department,
L. D. College of Engineering,
Ahmedabad, India
dr.hspatel@yahoo.com
Abstract— Economical aspects of long span slabs between flat
slab and grid slab is presented here. The objective function is to
come on the proper method of selecting the slab forms on
variable span. The flat slab is modeled and analyzed using the
direct design method and grid slab is modeled and analyzed
using plate theory method. The costing is calculated in three
stages, which contain quantity of steel, volume of concrete to be
used in slabs & beams and the cost of form work. By adding all
these parameters, cost of slabs per square meter is determined.
Keywords-Flat slab, grid slab, economical, comparison, long
span
I. INTRODUCTION
A slab is a flat, two dimensional, planar structural element
having thickness small compared to its other two dimensions.
It provides a working flat surface or a covering shelter in
buildings. It supports mainly transverse loads and transfers
then to support primarily by bending element just like beam.
A reinforced concrete flat slab is one of the type which is
used for long span, it is also called as beamless slab, is a slab
supported directly by columns without intermediate beams or
wall supports. Flat slab is a type of reinforced concrete
construction that transmits the floor or roof load directly on
columns without the aid of supporting beams. The flat slab is
often thickened close to the supporting columns to provide
adequate strength in shear and to reduce the amount of
negative reinforcement in the support regions. Columns are
flared at top to provide structure economical the portions of
the slab near the columns are thickened. In some cases, the
section of the column at the top as it meets the floor slab or a
drop panel, is enlarged so as to increase, primarily the
perimeter of critical section for shear and hence, increasing the
capacity of the slab for resisting punching shear and to reduce
negative bending moment at the support. Such enlarged or
flared portion of Column at their tops are called the column
head or the column capital. Flat slabs, now very common in
the world, are originally an American development. The first
patent for a recognizable reinforced concrete slab was given to
C.A.P.Turner in year 1903, flat slab construction were
described as “Mush rooms”.
Grids or coffered floor systems consisting of beams spaced
at regular intervals in perpendicular directions, monolithic
with a slab are generally employed for architectural reasons
for large rooms such as auditoriums, vestibules, theatre halls,
show rooms of shop where column free space is often the
requirement.
The rectangular or square voids formed in the ceiling
are advantageously utilized for concealed lighting. The size of
the beams running in perpendicular directions is generally
kept the same. Instead of rectangular beam grid, a diagonal
grid can also be used with the beams inclined at 45o
to the
sides.
II. FLAT SLAB
A. Behaviour of Flat Slab
Two way slab, flat plates and flat slabs are very identical in
their behavior. It is observed that maximum shear force and
bending moment will be induced very near to the column face.
To calculate the shear force and bending moment the slab is
considered panel wise and to locate the points of negative and
positive moments the slab is divided into column strips and
middle strips.
The strips along the column lines are considered to act as a
beam and are designed as a column strips. Deflection of these
strips at column is zero and that at mid span is maximum as
shown in fig 1.
The column strips behave as a continuous beam
supported on column and deflects as shown in figure. The
deflections at column supports A, B, C, and D are zero and
maximum at mid – span E, F, G and H. The middle strip also
behaves as a continuous beam supported on column strip and
deflects as shown in figure. The deflection are minimum at the
supports E, F, G and H of middle strips provided by column
strips and maximum at mid span I. Thus point A, B, C, and D
will have zero deflection and point I will have maximum
deflection points E, F, G and H shall have intermediate value
of deflection. The deflected flat slab at the centre of the panel
shall have a saucer shape and shape around the column shall
be convex upward. Hence there will be a point of inflection on
such deflection profiles that pass through the column. The
locus of point of inflection has been shown by dotted curves in
the figure. The column strip AHD will have negative moment
at point A and D and positive moment at H. The middle strip
EIG will have negative moment at point E and G and positive
moment at point I.As the middle strip are supported by the
loads are transferred from the middle strip to the column strip
which in turn transfer the loads on the columns. Thus the
13-14 May 2011 B.V.M. Engineering College, V.V.Nagar,Gujarat,India
National Conference on Recent Trends in Engineering & Technology
2. column strips are more heavily loaded than the middle strips
resulting in a higher value of moments in the column strips
than that in the middle strip.
The transfer of load from slab to column causes excessive
shear stress in the slab adjacent to the column as shown in fig
below. This causes initiation of shear cracks at a distance of
effective depth of the slab from the face of the column. These
cracks propagate towards the top. The failure occurs at the
bottom compressed edge of the slab surrounding the column
through punching
Fig. 1 Behaviour of flat slab
B. Direct design method
It is simple and easy method of obtaining the moments in
two way continuous slabs. The development of this method is
based on the test results available for two way slabs and flat
slabs. To ensure the two way slab behavior it is necessary to
impose limitations. If the limitations are prescribed below are
not satisfied then alternative solution is use
C. Limitations of Direct Design Method
There shall be minimum of three continuous spans in
each direction.
The panels shall be rectangular, and the ratio of the
longer span to the shorter span within a panel shall not
be greater than 2.0
It shall be permissible to offset columns to a maximum
of 10% of the span in the direction of the offset
notwithstanding the provision in above.
The successive span lengths in each direction shall not
differ by more than one – third of the longer span. The
end spans may be shorter but not longer than the
internal spans.
The design live load shall not exceed three times the
design dead load.
D. Atomization of Design
For the analysis and design procedure excel worksheet are
prepared. In this work sheet only certain essential data are to
be supplied and all the calculations are done on its own.
In the worksheet yellow color blocks denotes the data to be
supplied and green color blocks denotes the results through
calculations.
Input data at the starting of the excel worksheet are as under
1. Live load (kN/m2
)
2. Dead load (kN/m2
)
3. Floor finish (kN/m2
)
4. Panel size in X and Y direction (m)
5. Grade of concrete (N/mm2
)
6. Grade of steel (N/mm2
)
7. Length of column (m)
8. Cover (mm)
9. Modification factor.
In the starting phase modification factor is to be assumed.
Later on after analysis and design new modification factor is
obtained based on percentage of steel. By replacing new
modification factor with old, minimum thickness can be
obtained. For the economical aspects, the flat slab is designed
considering column with column head and with drop. The
following are the output parameters which are obtained using
developed excel sheet.
1 Drop (m)
2 Thickness of drop (mm)
3 Size of column head (m)
4 Design moments (kN.m)
5 Moments in longer direction with exterior and interior
panels (kN.m)
6 Moments in shorter direction with exterior and
interior panels (kN.m)
7 Check for deflection criteria
8 Shear checks are also done at corner column, edge
column and interior column.
The design of slab is carried out to satisfy strength and
serviceability criteria. The quantity assessment is carried out
for designed slab and rate analysis is performed. Cost in terms
of per meter2 are derived of various slab forms for span
ranging from 5 to 13 m as per table 1
TABLE I. COST OF FLAT SLAB PER M
2
Flat slab
Panels Total cost of 9
panels
Unit
cost/m2
Rs Rs
5X5 201921 897
7X7 516602 1171
9X9 1083989 1487
11X11 2021558 1856
13X13 3527418 2319
Reference of rates S.O.R .R &B 2008 -2009
13-14 May 2011 B.V.M. Engineering College, V.V.Nagar,Gujarat,India
National Conference on Recent Trends in Engineering & Technology
3. III. GRID SLAB
A. Analysis of Grid Floors
Analysis of grid floors can be carried out by three different
methods which are
Approximate methods
Plate theory method
Stiffness matrix method using computer
In present work the analysis and design of grid slab is
carried by plate theory method. Different span slab form are
selected and designed for span ranging from 5 to 13 meters.
Total 5 slab forms are designed with span 5X5, 7x7, 9x9,
11x11, and 13x13 m
B. Atomization of Design.
For the analysis and design procedure excel worksheet are
prepared. In this work sheet only certain essential data are to
be supplied and all the calculations are done on its own.
In the worksheet red colour text denotes the data to be
supplied and blue colour text denotes the results through
calculations.
Input data at the starting of the excel worksheet are as
under
1. Length of beam Lx, Ly (m)
2. Number of beams Nx, Ny (No’s)
3. Spacing of ribs (m)
4. Depth of beam (mm)
5. Width of beam (mm)
6. Width of flange (mm)
7. Grade of concrete and steel (N/mm2
)
8. Dead load (kN/m2
)
9. Live load (kN/m2
)
10. Floor finish (kN/m2
)
From the above supplied data we will get the total dead
load of slab, beams in X and Y direction from this load per
square meter is calculated. The following are the output
parameters which are obtained using developed excel sheet.
1. Moment of inertia (mm4
)
2. Flexural rigidity of ribs
3. Modulus of shear (kN/m2
)
4. Torsional constants (cu-m)
5. Torsional rigidity
6. Central deflection check (mm)
7. Long term deflection (mm)
8. Span/deflection (mm)
9. Maximum bending moments (kN.m)
10. Maximum torsional moments (kN.m)
11. Shear forces (kN)
The design of slab is carried out to satisfy strength and
serviceability criteria. The quantity assessment is carried out
for designed slab and rate analysis is performed. Cost in terms
of per meter2
are derived of various slab forms for span
ranging from 5 to 13 m as per table 2
TABLE II. COST OF GRID SLAB PER M
2
Fig. 2 Cost comparison of flat and grid slab
IV. CONCLUSIONS
From the graph of costing, it can be concluded that
1. In flat slab as the span range increases, there is steady
increase in the unit cost.
2. In grid slab as the span range increases, the increase in
the unit cost is not significant.
3. Flat slab with smaller spans are proved to be economical
but as the span range increases the grid slab becomes
economical
4. Thus Grid slab is proved to be more economical for long
span slab in comparison to Flat slab
REFERENCES
[1] N. Krishnaraju., “Advanced Reinforced Concrete Design” S.I.Units
[2] H.J. Shah., “Reinforced concrete Vol II”.
[3] S.N. Sinha., “Reinforced concrete Design”.
[4] V.P. Lunjha., “Computer Aided Analysis Design and drafting of R.C.C
Flat Slab”, -Thesis.
[5] IS : 456 – 2000 “Plain And Reinforced Concrete - Code Of Practice” (
Fourth Revision )
[6] SP- 16., “Design Aids for Reinforced Concrete to IS : 456 – 1978”
[7] SOR : 2008-09, “R&B Department, Govt of Gujarat”
Grid slab
Panels Total cost of 9
panels
Unit
cost/m2
Rs Rs
5 X 5 339744 1510
7 X 7 683518 1550
10 X 10 1143353 1568
11 X 11 1742564 1600
13 X 13 2579744 1696
Reference of rates S.O.R .R &B 2008 -2009
13-14 May 2011 B.V.M. Engineering College, V.V.Nagar,Gujarat,India
National Conference on Recent Trends in Engineering & Technology