In-home code

VTOP is a computer application that optimizes the pre-stress force and the longitudinal geometry of steel rods in a pre-stressed or post-stressed concrete beam. The aim of the program is to reduce the maximum pre-stress force required to support the structural loads. This is done by working out the optimum geometry of the tendons in the design.

The load assumptions of the VTOP are:

• Single load applied at the centre of the beam
• Uniformly distributed load along the beam
• Two concentrated loads applied at equal distances
• Three concentrated loads applied at equal distances

When the actual loads are none of the above mentioned, the program allows users to input envelopes of positive or negative moment values associated with the loads.

In general, the program assumes the beam to be designed with three rods; an upper rod of uniform eccentricity, an intermediate one with a variable eccentricity and a lower one with a fixed eccentricity.

Depending on the circumstances, the beam can be designed without one or two of the rods, considering only the ones you wish to include.

In the design process, the ultimate strength of the concrete under compression and tension and the design limits related to the maximum eccentricity for the rods have to be specified. Furthemore, the users can limit the radius of curvature of the rods along the beam.

From the optimum structural design point of view, VTOP solves linear optimization problems which obtain their solutions by means of the well-known SIMPLEX algorithm as described in the text called "Methods of Optimal Design of Structures", Santiago Hernández, Roads, Canals and Ports Engineer, Madrid (Spain), 1990.

At this moment, “La Ciudad de la Cultura”, which consists of six buildings of irregular geometry and the roofs simulating the ground contour is under construction in the suburbs of Santiago de Compostela, in Galicia, Spain. To accomplish this project, various conditions were considered, such as a flow condition (jet-wind flow phenomenon), a topographical condition (location on a hill), and a meteorological condition (wind gusts). In order to meet all the conditions, a special study was carried out on wind loads on the roofs and the façades of the buildings in this area. In this manner, we dealt with a special case like this one that the actual Standard does not cover. First of all, we determined the extreme wind conditions of the city of Santiago by obtaining the logarithmic wind profiles. Then these profiles were varied depending on the ground characteristics. Finally, a computer application was created to obtain maximum pressure results and their maximum and average variations by entering data such as period and ground type using the Spanish Standard, AE-88 for façades and roofs.

BASO is a computer application that optimizes the laminated steel profiles of the most common Spanish series or any other profile in double T-shape so as to take advantage of the maximum strength of a given material.

The program considers different cross-sectional dimensions such as the length and the thickness of the flanges and the web as design variables in all cases, while maintaining the essential features of each profile. For instance, the program keeps the flange length and the web height equal for the HEB profile to preserve the feature of this particular profile type.

BASO solves two sorts of problems:

1. Profile optimization of double T-shape under pure bending
2. Profile optimization of a bar under a generic combination of inner forces

The conditions considered in optimization problem number 1 are included in the Spanish Standard, EA-95, for sections under pure bending:

• Local buckling of the compressed flange
• Web buckling
• Yielding of material

The conditions considered in the optimization problem No.2 are included in the Standard for any type of loading:

• Absence of elastic fatigue in any point of the bar cross sections (9 conditions)
• Non-existence of global instabilities (3 conditions)
• Security under local instabilities (3 conditions)

The methods used for this problem may be found in the book named, "Métodos de Diseño Óptimo de Estructuras (Santiago Hernández, 1990)".

BASO provides a data table of Spanish profile series, HEA, HEB, HEM, IPE as well as the optimized profiles with efficiency indexes.

The BASO optimization module is the DOT program (VMA Engineering) containing three optimization algorithms.

PADO is an optimization program of portal frame structures. The employed method makes PADO different from other common structural analysis and dimensioning of steel structures. When a designer introduces an initial design along with the applied load, a common program gives back the displacements and the stress status. If some of them show inadequate values, the designer himself should make some changes in the design until the disadvantages are gradually eliminated by an iterative trial and error process depending only on his experiences. This way, the quality of the end-result depends on the ability of the user and the time available to identify the changes.

An optimization program is something more than just a mere structural analysis. In addition to its analysis capability, it accomplishes design improvements in a more rational manner than conventional methods which process it in a subjective manner as mentioned before.

Therefore, with a given type of a portal frame structure and taking the initial prototype and its loads into account, PADO generates changes in the design automatically until it identifies those that satisfy all the restrictions with greater excellence in a logical way.