Download Design Assessment Of A Reinforce Concrete Building Through Non

Design Assessment Of A Reinforce Concrete Building Through Non-Linear Analysis
May 2013
Geometry of the RC Building
An additional action, in order to
redesign the frame, was to include
beams. As seen in Fig.8, the beams that
were added had a section size of 35x70
cm except the parimetric beams that had
a 20x25 cm section which was not
modified according to the initial design.
Numerical results derived from the
pushover curve:
Fig.2 Ground floor plan view.
Fig.4 Pushover curve of the
frame.
Fig.1 Section View of the
RC building.
Fig.3 Typical floor plan view.
Abstract:
Given the recent earthquake activity in the UAE, seismic
excitation and the dynamic behavior of our structure became a
very popular subject. As it is known our structures are being
designed according to certain code provisions, which do not
force the accounting of significant seismic loads given that UAE
is considered to be a non-seismically active country.
This Thesis will study the design of a reinforced concrete (RC)
building that was designed by accounting low seismic loads and
considers a flat slab framing system. The main objective of this
work is to determine whether the structure is capable of
carrying a medium seismic excitation according to Euro code,
through the use of push over analysis.
To achieve this goal finite element models are constructed in
Etabs and Sap 2000 commercial software through which the
seismic assessment of the under RC structure is performed.
Fig.5 Deformed shape and
plastic hinges prior to failure.
Fig.6 Additional Shear walls.
As shown in Fig.9, after the redesign
was completed and the pushover
analysis was re-executed, the new
push over curve of the building
revealed that the carrying capacity of
the frame was increased.
The computed carrying capacity of the
redesigned frame was 22688.135kN.
Which satisfies the demand of the
seismic code.
Fig.9 Pushover curve of the
redesigned frame.
Redesign:
Conclusions:
As seen in Fig.6, an additional row of
35X300 cm shear walls were added to the
front and back of the building. These
shear walls extend from the ground to the
top roof. In case of a seismic excitation the
shear walls will resist to the horizontal
loads thus will increase the structures
carrying capacity.
1. Assessing our structures by using software such as ETABS
and SAP2000, is of significant importance in terms of safety
and accuracy. ETABS and SAP2000 automatically generate
and assign code-based loading conditions for gravity,
seismic, wind, and thermal forces thus performing the
design and assessment becomes a very efficient procedure.
2. Our numerical results and overall experience showed that
modeling RC structures is a procedure that requires both
theoretical knowledge and practical experience.
3. After performing a modal analysis it was found that the 1st
mode was rotational thus the geometry of the frame and
the stiffness distribution of the shear walls were irregular.
In addition to that, we found that the 1st fundamental
period was equal to 1.83 seconds that underlines the fact
that the flat slab system used derived a flexible mechanical
behavior despite the use of relatively large shear walls.
4. The 12-storey RC building was found inadequate in
carrying the 22.62MN seismic load according to EC8
according to the numerical results that derived from the
non-linear analysis. For this reason a redesign of the frame
was performed so as to overcome this issue.
Fig .7 columns to shear walls.
Mohammed Mohideen
200710322
Fig.8 Beams used throughout
RC frames.
Plastic hinges were assumed along the
whole structure so as to account material
nonlinearities in both beam and shell
elements. It is important to note here that
the results derived in the previous
sections were through the use of Etabs
software. The pushover analysis was
performed in SAP2000. Fig.5 shows the
developed plastic hinges prior to failure.
As seen in Fig.7, a closer view is given to
show the exact location where three
columns located at the ground floor and
mezzanine
were also converted into
shear walls so as to increase the stiffness
of these floors.
The main objectives were:
• Study the mechanical behavior of the RC structure
• Preform Pushover analysis
• Redesign the building so as to achieve a seismically resistant
behavior
Software used:
Etabs is a structural and earthquake engineering software
produced for the analysis and design of multi-story
buildings. Sap2000 is integrated software for structural
analysis and design it harnesses an analytical method.
The reason two software's were used was because
problems were faced with shell elements regarding Etabs
As we can see from Fig.4, the first
plastic hinges occur for a total
horizontal load of 5.1 MN and the
maximum current capacity of our
structure was found to be 17 MN with
a total displacement of 6.1 cm at the
top floor. The seismic demand
according to Ec8 was 22.6 MN thus the
structure requires to redesigned.
Presented by:
Adnan Mayassi
Moiad Jumaa
200910018
200710497
Supervised by:
Dr. George Markou
Ahmad Khier
201010540