Phage 1
Diagrid Structural System
Binh K. Nguyen and Hasim Altan
School of Architecture
The University of Sheffield
Abstract—
The study focuses on strategies to enhance the performance of a
building against lateral forces and earthquake. The strategies range
from aerodynamic modifications to structure reinforcement to adopting
auxiliary damping devices/systems. The study’s direction was toward
Diagrid structural systems – the latest trend in high-rise projects.
Keywords-component; lateral forces; tall-buildings; high-rise;
diagrid, damping strategies.
INTRODUCTION
The
evolution of tall-building structural systems, based on new structural
concepts with newly adopted high-strength materials and construction
methods, has been towards ‘stiffness’ and ‘lightness’. Structural
systems are becoming stiffer and lighter. Diagrid1, acknowledged
worldwide as a very light structure and one of the best when it comes to
withstanding lateral forces, has been leading the trend. The lighter a
structure is, the higher it can rise. On the other hand, it is also
easier to blow away a light subject than a heavy one. Diagrid can save
from 20% to 30% the amount of structural steel in a high-rise building.
Moreover, high-strength material technology has come a long way since
the invention of modern high-rise building in 1930s. Materials
themselves are stronger and lighter. It is common knowledge that, rather
than directly standing the forces, it is better to reduce them and
dissipate the magnitude of vibrations. A high-rise structure needs both
stiffness and damping characteristics. The strategies to enhance
tall-buildings’ lateral performance can be divided into 3 categories:
(1) Aerodynamic Modifications; (2) Structural Reinforcements; and
(3)
Using Auxiliary Damping Devices/Systems. The strategies presented below
are the ones that can be used for that use Diagrid structure. However,
most of the strategies can be applied to other types of tall-building
structures.
Diagrid
(or diagonal grid) is a design for constructing large buildings with
steel that creates triangular structures with diagonal support beams. It
requires less structural steel than a conventional steel frame. It also
obviates the need for large corner columns and provides a better
distribution of load in the case
of a compromised building.
AERODYNAMIC MODIFICATIONS
A) Aerodynamic Shapes
The
form of a tall-building is usually limited to rectangular prisms. From
geometrical point of view, this form is rather susceptible to lateral
drift. Other building shape such as cylindrical, elliptical, crescent,
triangular and like, offer better lateral performance due to inherent
strength in their geometrical form. They provide higher structural
efficiency and allow greater building height at lower cost. Building
codes permit a reduction of the wind pressure design loads for circular
or elliptical buildings by 20%-40% of the usual values for comparably
sized rectangular building.
B) Corner Modification
Investigations
have established that corner modifications such as chamfered corners,
horizontal slots, and slotted corners can significantly reduce the along
wind and across wind responses when compared to a basic perpendicular
building shape.Chamfers of the order of 10% of the building width makes
40% reduction in the along wind response and 30% reduction in the across
wind response. Excessive rounding of corners
of the cross
section, approaching a circular shape in the cross section,
significantly improves the response against wind. With a building of
roughly 70 stories, peak deflection of the model in circular cross
section was about half of the one with square cross section.
Fin Vented Fin Slotted Corners Chamfered Corners Stair-step Corners