Concrete Filled Tubular ( Cft ) Column

ACI 318-63 requires that the minimum ratio of longitudinal bars shall be at least 1.0%. Also, The vertical center-to-center spacing of the lateral ties shall be one of the smallest of: (1) 16 longitudinal bar diameters to restrain longitudinal bars from buckling, (2) 48 tie diameters to ensure sufficient tie area to restrain the lateral displacement of the reinforcing bars, and (3) the least lateral dimension of the column to develop the maximum strength of the concrete core. As shown in Fig. 1, The dimensions and steel reinforcement details of the columns involved in this experimental program were particularly selected to represent relatively older columns. In this experimental program, the longitudinal reinforcement ratio, ρl, was constant

Introduction : To determine the strength, maximum load can be applied and workability of concrete mixture.

The improvement of the skyscraper structures starts from 10 floor stories to high as 150 floor stories high. The Reliance Building Chicago, USA, in 1895, 15 stories high used the semi-rigid steel frame. The semi-rigid steel frame was held together with steel beams and connected by rivets. (Bennett, P.42) The 60 stories high First Wisconsin Center, Milwaukee, USA in 1974 employed the steel belt truss with framed shear truss. This structure used the horizontal trusses at the upper and lower stories to enhance the framed shear truss. (Bennett, P.44) The Sears Tower, Chicago, USA, in 1974, 110 stories high used the Bundled tube. The bundled tubes were made up of a cluster of connected frame tubes, reinforced by steel beams at each story to increase the strength of the structure. Various tubes terminated at different level to further strengthen the bundled tubes at the center. (Bennett, P.44) The future structure was the Superframe, which can reaches at least 150 stories high. It used the concept of the Eiffel Tower with framed tubes connected by horizontal trusses. (Bennett, P.45) It was the innovation of the structural design that enables skyscrapers to reach new height. These methods include the use of

When designing a building, the load that must be supported is a very important consideration. Various building materials will each have their own levels of strength and ability to support loads. In addition to this, the way in which the building material is utilized may also play a role in the ability of the building to support large loads. The implementation of concrete as a building material led to much stronger walls and supports in Roman buildings. Additionally, the development of the arch was revolutionary in its ability to support loads. The types and sizes of structures that the Romans could build became unlike anything seen before, and they also became very interested in working with interior spaces, as well (Ambler, n.d.).

Every construction material and system has its own characteristics which to a greater or lesser extend influence the layout, span length, construction depth, stability system, etc. This is also the case for precast concrete, not only in comparison to steel, wood and masonry structures, but also with respect to cast in-situ concrete. Theoretically, all joints between the precast units could be made in such a way

Proc., 7th Int. Conf. on Fracture Mechanics of Concrete and Concrete Structures. Korea Concrete Institute,

Rigid frame systems are not efficient for buildings taller than 30 stories, because lateral defection due to the bending of columns causes the drift to be too large. On the other hand, steel bracing or shear walls with or without rigid frame (brace systems and shear wall systems), increases the total rigidity of the building and the resulting system is named as braced frame or shear-walled frame system. These systems are stiffer when compared to the rigid frame system, and can be used for buildings over 30 stories, but mostly applicable for buildings about 50 stories in height. However, there are examples for these systems reaching over 100-storey

When reinforced concrete columns are axially loaded, the reinforcement steel and concrete experiences stresses. When the loads are high compared to cross-sectional area of the column, the steel and concrete reach the yield stress and column fails without undergoing any lateral deformation. The concrete column is crushed and collapse is due to the material

Concrete is the second most utilized substance in the world after water and is the most widely used construction material with an annual global production of about 10 billion tonnes. It is preferred in most structures because of its unique properties such as durability and high compressive strength. It is however relatively weak in tension, its tensile strength being about 10-15 % of its compressive strength requiring that it be reinforced with materials such as steel rods, glass or plastic fibers in order to improve its ductility. It is also prone to slight shrinkage during the drying process and may lead to cracking especially in normal strength concretes. (R. I. Gilbert, 2001). As defined by the Portland Cement Association, the durability of concrete is its ability to counteract abrasion, weathering action and chemical attack, and still maintain its desired engineering properties. The proportioning and interactions between concrete ingredients, placement and curing practices as well as the service environment determine this ultimate durability and life. The ideal situation therefore in any construction project is to choose the correct concrete type which will be more durable based on the project requirements.

G. Jeenu, U. R. Reji, and V. Syam Prakash, “Flexural Behaviour of Hybrid Fibre Reinforced Self Compacting Concrete”, 32nd Conference on OUR WORLD IN CONCRETE & STRUCTURES: 28 - 29 August 2007

Increasingly, engineers are designing composite and mixed building systems of structural steel and reinforced concrete to produce more efficient structures than realized using either material alone. Recent literature has pointed out a need for greater understanding of the interaction of structural steel and reinforced concrete in such systems. In this paper, the behavior of composite beam-column connections is examined through results of an experimental research program where15 two-thirds scale joint specimens were tested under monotonic and cyclic loading.

There are many differences that play a major role between reinforced concrete and post tensioned concrete. The reinforced concrete is a very time consuming system. Each and every steel bar has to be individually placed and tied together. Whereas in the post tension system is not as time consuming. Due to the tendons taking most of the load, the steel quantity is cut down by more than half (usually).

Adorno (2004) developed his studies using Concrete and reinforced concrete submitted to straight flexure-compression with the same dimensions. Their experimental program was divided into two Series, PSA (non-reinforced columns) and PCA4 (strengthened columns). They are shown in Figures 2.14 and 2.15. Although the PSA series is made of simple concrete columns, a Nominal diameter equal to five millimeters, was used at the ends of the models, with the Purpose of avoiding localized ruin of these regions, because of the concentration of stresses. Adorno (2004) concluded on the rupture load and the ultimate moment that:

Shear walls are structural members used to elongate the strength of R.C.C. structures. These shear walls will be construct in each level of the structure, to form an effective box structure. Equal length shear walls are placed symmetrically on opposite sides of outer walls of the building. Shear walls are added to the building interior to provide more strength and stiffness to the building when the exterior walls cannot provide sufficient strength and stiffness. It is necessary to provide these shear walls when the tolerable span-width ratio for the floor or roof diaphragm is exceeded. The present work deals with a study on the improvement location of shear walls in symmetrical high rise building. Position of shear walls in symmetrical buildings has due considerations. In symmetrical buildings, the center of gravity and center of rigidity coincide, so that the shear walls are placed symmetrically over the outer edges or inner edges (like box shape). So, it is very necessary to find the efficient and ideal location of shear walls in

.1.8.1.1.3. Stress-strain curves for normal and lightweight concrete for the design of cross-sections in Euro code: