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Cyprus International UniversityCivil Engineering Department
CVL548 HIGH RISE BUILDING
Title : Rigid Frame systems Submitted to : Dr. Alireza Rezaei
By Group 1 : Ali Ezreg ID :20153333 ID :20153680 Muftah Aljoat
ID :20153312 Adel Milad
May/2016
Outline History Introduction What is a Rigid Frame system? Applications of Rigid Frame system Material Properties How is Connect the Rigid Frame system? Considerations of Rigid Frame Design Behavior of rigid frames under Lateral loads Methods of Rigid Frame Design Advantages disadvantages Environment and Health Safety Case Study Conclusion
A tall building boom in the late 1920s and early 1930s in urban centers
Chicago and New York .
In the 1960s and 1970s, Professor Egor Popov at the University of
California at Berkeley and other researchers began to perform cyclic
laboratory testing of steel moment framing.
As a result of the apparent high performance of these structures, the
building codes from the 1960s adopted preferential design criteria for
steel moment frames.
Historic Development
Cont …
Fig 1: Fracturing of the column at welded beam-to-column connection in Northridge
earthquake.
In the aftermath of the 1994
Northridge, California
earthquake, damage to steel
special rigid frame connections
, spawned concern about the
reliability of established design
and construction procedures.
Rigid frame systems, also called moment frame systems, are used in steel and reinforced concrete buildings. This system consists of beams and columns .
Reinforced concrete and steel in rigid frames are used In earlier high-rise buildings, while concrete were under development, steel frames were predominated.
A rigid frame is an unbraced frame, that is capable of resisting both vertical and lateral loads by the bending of beams and columns.
Stiffness of the rigid frame is provided mainly by the bending rigidity of beams and columns that have rigid connections.
Introduction
A rigid frame system are comment system using in high rise
building in this years on the world that has more stability and less
damage due to Natural disasters like earthquake and wind load.
A rigid-frame structure is a structure made up of linear elements,
typically beams and columns, that are connected to one another
at their ends with joints that do not allow any relative rotation to
happen between the ends of the members.
What is a Rigid Frame system?
Fig 2 Rigid frame structure under construction
of Rigid Frame system ApplicationsSome examples of tall buildings using the rigid frame system with steel
structural material include:
Fig 4 The 12-storey, 55m high Home Insurance Building (Chicago,1885)
Fig 3 The 21-storey, 94m high Lever House (New York, 1952)
Cont…
Fig 5 Ingalls Building, Cincinnati, USA, 1903
The 16-storey, 65m high Ingalls Building (Ohio, USA 1903) (Figure 5)
Example of tall buildings using the rigid frame system with reinforced
concrete structural material include:
Fig 6 building height with structure form
SteelThe seismic design category AISC 341 is requires that structural steel
used in steel special moment frames meet the requirements of AISC 360 .
The specified minimum stress to be used for members in which inelastic
behavior is expected cannot exceed 50,000 psi, unless the suitability of
the material is determined by testing in accordance with AISC 341.
Material Properties
ConcreteConcrete used in composite components and in supporting
foundations must meet the requirements of ACI 318, requires a
minimum concrete compressive strength, f’c , of 3,000 psi.
Cont…
The design of a rigid frame building is not much different from
others, essentially. Considering by held together and made
stable by very tight junctions of the members (column & beam).
Similar to this, the structure of a rigid frame building is
characterized by its rigid connections of straight or tapered
columns and beams. That can be steel rigid frame or concrete
rigid frame as clarify in (fig 7).
How is Connect the Rigid Frame system?
A rigid frame derives its lateral stiffness mainly from the bending rigidity of frame members interconnected by rigid joints. The joints shall be designed in such a manner that they have adequate strength and stiffness and negligible deformation.
Modules of rigid steel frame connection
• Using angles or split tees to connect top and bottom beam flanges to columns to refuse the wind load
• By the 1960-1970, began to use the connection type as the welded unreinforced flange - bolted web, this modules couldn't refuse the lateral load
Post Northridge Special
Moment Resisting
connection (welded and
bolted) in one direction
and simple connection in
the orthogonal direction
Cont…
Considerations of Rigid Frame Design
Decrease Moment (Affects member size) Increasing Stiffness :
• Redistributes Moments • Limits Deflections
Joint Rigidity Support Types
Beam behavior (Fig 8)
Beam-to-column connections
Depending on the type of connection used,
This might trigger any of the following failure
modes:
• Fracture in or around welds.
• Fracture in highly strained base material.
• Fractures at weld access holes.
• Fracture at bolt holes.
• Shearing and tensile failure of bolts.
Cont…
Fig 8: Typical local buckling of beam flanges and web in zone of plastic hinging at high
levels of inelastic rotation.
Joint panel zone behavior
Column behavior (Fig 9).
Column splices
Column bases
Side sway Collapse
Structure P-delta Effects
Cont…
Fig 9: Formation of a single story frame mechanism, also called a "weak story"
mechanism.
The sizes of many columns also are drift-controlled because the strong-column/weak-beam provisions discussed earlier demand larger columns if larger beams are used.
Exceptions are end columns in steel special rigid frames, which often have high axial load demands and in most cases are controlled by strength design criteria.
when designed for strength considerations only, the biggest disadvantage in rigid frame systems is the size of lateral drift, which causes discomfort to residents and damage to non-structural elements.
Design Consideration - Drift
1) The first is the deformation due
to cantilever bending of the
building (bending deformation),
which is approximately 20 per
cent of the total lateral drift
(Figure 10 a).
Cont…
There are two causes of lateral drift:
Fig 10 Lateral drift in rigid frame systems
2) The second is that of the deformation
due to bending of the beams and
columns (shear deformation),
approximately 65% is due to the
bending of the beams, and 15% to the
columns, totaling approximately 80 %
of the total lateral drift (Figure 10 b).
Cont…
Fig 10 Lateral drift in rigid frame systems
The drifts of rigid, comparison with others
From the structural design point of view, tall (high-rise) buildings, because of their
unusual height, show a greater sensitivity to wind and earthquake induced lateral
loads than low-rise buildings. Estimating those lateral loads which play an important
role in the design of tall buildings is more difficult than estimating vertical loads.
Earthquake loads increase according to the building weight, and wind loads increase
according to the building height. For this reason, wind loads, while they are generally
an unimportant issue in the design of structural systems for low- and mid-rise
buildings, play a decisive role in that of tall buildings, and can even be a cause of
large lateral drift (sway) that is more critical than that from earthquake loads.
Behavior of rigid frames under Lateral loads
Fig 11: Differences between hinged frame and rigid frame structure.
Fig 12: Differences between post & beam structure and rigid-frame structure
The deflection of rigid, comparison with others
Distribution of moment on the rigid and hinged frame
• Decrease the axial load on the column, gives smaller cross section of column
• Increase the buckling at column
• Small deflection at beams • Resists lateral deformation
• More drift • Increase the axial load on
the column, gives large cross section of column
• Increase the buckling at column
Rigid frames are used when the architectural
design will not allow a braced frame to be
used. This type of lateral resisting system
generally does not have the initial cost
savings as a braced frame system but may
be better suited for specific types of
buildings.
Figures 13 & 14 show a floor plan and
building line elevation of a rigid frame system.
Methods of Rigid Frame Design
Fig 13 : Typical floor plan with rigid frames
Figure 13 indicates the solid triangle
designation typically used to show rigid
connections between beam and column
as well as girder and column.
The building elevation shown in Figure 14
indicates the same solid triangular symbols
at the floor line beam to column joints.
Cont …
Fig 14: Rigid frame building elevation
Connections between the beam and column typically consist of a shear
connection for the gravity loads on the member in combination with a field
welded flange to column flange connection. Column stiffener plates may be
required based on the forces
transferred and column size.
This type of joint is illustrated
in figure 15.
Cont …
Fig 15: Typical rigid (moment) connection
Moments get redistributed.
Deflections are smaller .
Effective column lengths are shorter .
The main advantage of rigid frame structures is that they do not have
structural walls or vertically oriented diagonal braces.
Rigid frames are provide architectural freedom in design.
rigid frames typically impose smaller forces on foundations than do
other structural systems.
Advantages of Rigid Frames
Rigid frames not specifically detailed for seismic resistance have no
special detailing criteria .
These frames are not permitted as seismic force resisting systems in
Seismic Design Categories D, E, or F .
The added cost results from the use of heavier sections in the rigid
resisting frames, requiring increased steel usage and more labor
intensive connections than is common in braced structures.
Disadvantages of Rigid Frames
The property itself can influence the design team's structural system.
Site layout and soil conditions can pose certain issues with
foundations and building geometry.
The proposed building geometry can limit the available structural
schemes due to the complexities that can result from acute angles .
Earthquake and wind impacts are always considered in choosing
frames.
Environment and Health Safety
CASE STUDY
In this study, a new lateral resistant system called hybrid frame, which is
a combination of semi-rigid and fully rigid steel connections used in 20-
story SAC frames, is presented herein : Several different patterns and locations of semi-rigid connection replacements within
the frame were examined in order to identify hybrid frames with the best seismic
performance.
The effective connection stiffness was identified by performing a parametric study on
the initial stiffness of the semi-rigid connections. Then, the cyclic behavior of the
connections with the most effective Stiffness was obtained, using nonlinear element
analysis.
Abstract Summary for the case study
The simplified model of a rigid frame
The simplified model of a hybrid frame
A rigid frame in high rise structure typically consists of parallel or orthogonally arranged bents consisting of columns and beams with moment-resistant joints.
Its unobstructed arrangement, clear of structural walls, allows freedom internally for the layout .
Rigid frames are considered economical for buildings of up to about 25 stories, above which their drift resistance is costly to control.
If, however, a rigid frame is combined with shear walls, the resulting structure is very much stiffer so that its height probability may extend up to 50 stories or more.
Conclusion
Tall Buildings: structural systems and aerodynamic Form Journal of Constructional Steel Research ( Earthquake resistance frames
with combination of rigid and semi-rigid connections )ACI (2008). Building code requirements for structural concrete (ACI 318-08) and commentary, American Concrete Institute, Farmington Hills.
AISC (2006). Seismic design manual, American Institute of Steel Construction, Inc., Chicago, IL.
AISC (2005a), ANSI/AISC 341-05. Seismic provisions for structural steel buildings, American Institute of Steel Construction, Inc., Chicago.
AISC (2006). Seismic design manual, American Institute of Steel Construction, Inc., Chicago, IL.
References