International Concrete Abstracts Portal

Spreadsheet programming is presented as a new programming alternative for solving daily calculations in the engineering design office. Two spreadsheet programs with different applications are used to introduce the reader to this technique. A retaining wall template demonstrates the advantage of altering one design parameter and seeing the results propagate instantly, thus leaving the engineer with a very responsive tool. A prestressed bridge template organizes in separate windows the engineering design process involved in the prestress design. The template is written according to the design requirements of AASHTO. It allows the engineer to verify different alternatives in the design of the concrete girder, hence leading to a manually optimized section.

Presents an algorithm for a program code for the analysis of concrete columns reinforced with nonprestressed reinforcement, prestressed reinforcement, or both. The algorithm can be used to generate the coordinates of the load-moment interaction diagram for the section chosen in terms of shape; material properties; and type, amount and location of nonprestressed and prestressed reinforcement. Three shapes--namely rectangular, T, and I--can be analyzed. Hollow-core wall panels can be analyzed by converting them to equivalent I-sections. The lateral reinforcement could be ties, spirals, or none. The program can also be coded to reanalyze the section for revised partial input. This capability aids the designer in generating the loads and moment for, say, a different compressive strength of concrete without reinputting the entire design data. The load-moment values can be printed to look like the load-moment interaction diagram. The various assumptions involved, the equations, and the sequence of calculations are explained using a number of flow charts. A procedure is outlined for using the program for design purposes. Example problems are provided to illustrate the input-output variables. The program code, written in BASIC for Apple desktop computer, can be obtained from the author. The algorithm deals with only the strength aspect. The serviceability aspect, especially for prestressed columns, should be checked separately.

SP-98 Because the design of concrete structures and proportioning concrete mixtures can be complex, you need state-of-the-art knowledge when selecting structural systems and construction materials. Computer Applications in Concrete Technology has been especially prepared to aid designers and engineers in all facets of concrete design and technology. Providing a source of "know-how" for the entire civil engineering community, this symposium volume of 13 papers covers a broad spectrum of computer applications. Some of the subjects include: expert systems for selecting concrete constituents, analysis of reinforced concrete shear walls, analysis and design of load-bearing tilt-up walls, decision support systems for design, and spreadsheet programming for structural design. Other topics include: monitoring construction with microcomputers as you build, analysis and design of reinforced and prestressed concrete compression members using desktop computers, and integrated design environment for concrete structures.

With the aid of modern digital computers and sophisticated computational techniques such as the finite element method, it is now possible to simulate the structural behavior of an arbitrary reinforced concrete shell structure under general loading through its elastic, cracking, inelastic, and ultimate load ranges, taking into account nonlinear material, nonlinear geometry and time-dependent effects of creep and shrinkage. In this paper, a method of analysis and a computer program based upon a composite layered finite element displacement model are briefly described. The analysis recognizes the nonlinearities due to cracking, nonlinear stress-strain behavior in concrete, yielding of the steel reinforcement and the tension stiffening between cracks. The effects of the countinuously changing structural geometry are taken into account by an updated Lagrangian formulation. The time dependent effects of creep and shrinkage are also included by an initial strain procedure. Numerical results for reinforced concrete shells obtained with the computer program are presented which indicate that in some cases an increase and in other cases a large reduction in the calculated ultimate load occurs as each of the nonlinear factors is included in the computer analysis.

A finite element procedure is presented for the analysis of reinforced concrete shearwalls. The wall is idealized as a two-dimensional structure, and the global behavior of the wall under static loading conditions is emphasized. A combination of a new family of higher-order quadrilateral elements and beam elements is employed in the finite element discretization of the wall. Constitutive models of material behavior are based on the nonlinear elasticity. The main material nonlinear effects accounted for in the analysis are the tensile cracking, the biaxial compressive response of concrete, and the yielding of steel reinforcement. A smeared approach is used in the representation of concrete cracking and steel bars. Simplified uniaxial and biaxial material models for reinforced concrete are developed and presented in detail. The incremental-iterative nonlinear solution techniques employ both constant and variable stiffness with the option of selective updating of the stiffness matrix in the load increment. Numerical examples are presented and compared with other existing solutions.