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Showing 1-5 of 13 Abstracts search results

Document: 

SP97-05

Date: 

February 1, 1987

Author(s):

S.K. Ghosh

Publication:

Symposium Papers

Volume:

97

Abstract:

This paper discusses the design of reinforced concrete flat plate slab sys-tems, commonly used in high-rise construction, against punching shear. A number of newly devised charts are introduced to facilitate such design. A significant problem with a new ACI Code requirement concerning shear due to moment transfer at an exterior flat plate-column joint (Sect. 13.6.3.6 of ACI 318-83) is pointed out. The problem is illustrated through a design example.

DOI:

10.14359/6899


Document: 

SP97-11

Date: 

February 1, 1987

Author(s):

John Albinger and Jaime Moreno

Publication:

Symposium Papers

Volume:

97

Abstract:

The ready-mix concrete for high-rise structures in Chicago is unique in reference to the special concretes that have been developed for this type of construction. However, the overall picture of the ready-mix industry is similar to what is happening to the ready-mix industry in other areas of the world. The ready-mix concrete business is a dynamic resource for the construction industry, which must periodically reevaluate its position in relation to the economy, the nation, local industry, and especially with the customer. Highly-developed economies bring changes in market conditions. A change which has been occurring is the change from a product to a service-related market. This change occurs earlier in mass consumer products and lags behind in more static products like those in the construction industry. This conversion from product to service is taking place now in the construction industry. The ready-mix industry has traditionally made its profit in the volume of regular concrete with strengths from 3000 to 5000 psi. This is a product that does not require special quality control or special technology, consequently it can be handled by concrete technicians and salesmen with limited technical knowledge. This is also a product which does not require special promotion, is simple for code compliance, has abundant analysis and design information for the users, and does not require special mixing and transportation equipment. It is not difficult to sell when the price is right. It is usually sold with a questionable margin of profit which will continue diminishing until management makes the decision to make some changes. Management realizes that the ready-mix industry cannot survive in the mature economy of large metropolitan areas where the large concentration of ready-mix producers and their geographical proximity has brought their profit to a minimum return on their investment. Consequently, the search for changes becomes imperative to survive in a highly technological and competitive economy. However, changes are expensive in this high capital industry. The changes required to bring the ready-mix industry to high-technology levels are expensive because they involve management, equipment, quality control and marketing concepts. Aside from being expensive, they are difficult to accomplish because they require a total commitment from management and a clear understanding of a long range plan for its proper implementation.

DOI:

10.14359/6905


Document: 

SP97-07

Date: 

February 1, 1987

Author(s):

Albert J. Gouwens

Publication:

Symposium Papers

Volume:

97

Abstract:

A simplified method to calculate the moment mag-nification factor and the critical buckling load for a laterally unsupported story of a building is discussed. The method is a hand calculation technique which has nearly the same results as a computerized P A method. The method is a substitute for the effective length method. A practical designer% definition of a braced frame is given. A practical designer's definition of frame instability is given. Several design examples are given toillustrate the application of the procedures.

DOI:

10.14359/6901


Document: 

SP97-06

Date: 

February 1, 1987

Author(s):

Kolbjorn Saether

Publication:

Symposium Papers

Volume:

97

Abstract:

A large amount of prestressed concrete is being used in high-rise building construction. Unlike the prestressed concrete channel liners in Italy where concrete is transferred into a fully flexible material (see Fig. l), and unlike the finely detailed, thin-webbed girders used in a hanger con-struction in England as shown in Fig. 2, the prestressed concrete used in high-rise construction where used for office and commercial buildings consists mainly of shallow slabs and beams, one-way joists, skipped joists 1 or waffle slabs. In residential buildings,the more common type of pre-L stressed member is the flat plate. Plain and simple-looking to the outside, the flat plate is nevertheless quite a sophisticated structure, presenting to the structural engineer a challenge as far as its structural behavior is concerned. In fact, a visual expression of what is happening within the flat plate is given by the analogues and very sophisticated and different-looking structure: The Structural Membrane. The following gives a short description of the prestressed structural membrane,helping the engineer to understand the design of prestressed flat plates. The main characteristic of the structural membrane is its ability to carry uniformly-distributed loads to point supports through uniform stresses within its thin-shell surface. In the structural mem-brane, the resisting bending moments are developed by this uniform stress times the variable distance of the membrane to the thrust surface. The thrust surface is defined as the surface in which all the prestressing ten-dons lie. The analogy between the structural membrane and the mild steel-reinforced flat plate consists of the fact that in the flat plate, the bending moment capacity or the force couple has a level arm, or distance II II D , which is constant and a stress that is variable. In a prestressed flat plate,one further feature to be recognized is that a portion of the load is balanced by the prestressing cables. This portion, often 80% of the dead load, has the same characteristics as that of a structural1 membrane; that is, the prestress in the tendons stays constant as does the concrete stress, but the level arm of the draped tendon varies. The other portion of the load (often 20% of the dead load and all of the superimposed dead load and live load) causes stresses to build up within the plate much in the same manner as it does within the mild steel-reinforced flat plate. These con-ditions will be discussed later in this paper. It should be noted that high peak moments occur near the column supports corresponding to the funnels in the structural membrane.

DOI:

10.14359/6900


Document: 

SP97-02

Date: 

February 1, 1987

Author(s):

Jaime Moreno and John Zils

Publication:

Symposium Papers

Volume:

97

Abstract:

The optimum design of high-rise buildings should satisfy architectural and engineering performance criteria according to codes and local regulations at the most economical cost. The large variety of construction materials and structural systems makes the task of obtaining the optimum solution difficult for the designers. This study is related to the structural variables influencing the economical choice of materials and systems in cast-in-place multi-story construction. An efficient and economical structural system can evolve only through an understanding of the significant factors affecting the design of a tall building. This optimization study has considered a number of these factors in order to evaluate their in-fluence on the optimization process. These factors can be summarized as follows: Design lateral force (wind) Height-to-width ratio of building, Ratio commonly known as Aspect 30 Criteria for lateral stiffness (Drift Ratio) 4 l Type of occupancy (office vs. apartment) Influence on foundation system Fire rating considerations Local availability and cost of primary construction materials The final choice of a structural system depends upon the factors mentioned above. It should be obvious that there cannot be any single structural system that is valid for all cases. It is this philosophical attitude that is essential for the architect and engineer in evaluating the best possible structural system for a particular project, time. for a particular location, at a particular The most common types of multi-story construction are residential and office buildings. Architectural layouts for residential' buildings have their maximum performance from spans of 15 to 24 eet, and for office buildings from spans of 24 to 30 feet. Be-sides the column, caisson, and floor system considerations for these two types of buildings, the lateral load consideration is an important concept in the design of high-rise structures. A maximum recommended drift of l/500 of the height of the building allows the buildings without shear walls (frame buildings) to be built to a certain number of stories depending on the slab thickness and column sizes. When shear walls are added to the frame buildings, they can be built still taller, satisfying the maximum drift limitations.

DOI:

10.14359/6896


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