PORTUGUESE ENGINEER CREATES BOLD NEW DESIGNS WITH ALGOR

If you take a vacation to Madeira Island, a popular tourist spot situated in the Atlantic Ocean about 300 km west of Casablanca, you will probably use one of the unusual structures analyzed by Jos?C. Calixto da Silva, a civil engineer in Lisbon, Portugal.

Mr. Calixto da Silva's analyzed designs include a runway built out over the sea and an 800 foot elevator up the side of a cliff. Designing these "out of the ordinary" civil engineering projects required extensive use of Algor stress, heat transfer, natural frequency (modal), buckling and random vibration analyses.

This model represents a mere 200 meters of the Madeira Island International Airport extension over the Atlantic Ocean. The complete runway extension will be 2000 meters in length.

Air Traffic Makes Runway Extension Necessary

The runway of Madeira Island International Airport is currently 1600 meters long. It can accommodate smaller aircraft such as Boeing 737s and Airbus type planes. However, it is now necessary to find a way to land larger planes, such as Boeing 747s and McDonnell-Douglas DC10s.

Tourism, a major local source of income, and frequent visits from the island's many natives who live abroad make great demands on Madeira Island International Airport. Smaller planes are not meeting that demand.

"Visitors have to suffer in the inconvenience of taking indirect flights, without the certainty of getting a transit connection between mainland Portugal and the Island," said Mr. Calixto da Silva. "It is not uncommon for a traveler to have to wait for a day or two at the Lisbon Airport before a connecting flight is available, especially in times of high traffic or bad weather."

The Runway over the Ocean

Mr. Calixto da Silva and Jos?Pacheco Silveira work as consultants for J. L. C鈔cio Martins - Projectos de Engenharia, Lda., which is part of a design-build bidding consortium organized to present a proposal for the design and construction of the runway extension and related works at Madeira International Airport. Unfortunately, there is a limited area in which to build. Building out over the ocean is a daring and complicated solution.

"Algor software allows different models, all of them quite big and complex, to be created and analyzed in a minimum of time and with little effort," said Mr. Calixto da Silva. The more solutions it is possible to analyze, the better the chance that the optimum solution can be found and used in the proposal. This gave C鈔cio Martins and its consortium the edge over other bidders. In fact one of Mr. Calixto da Silva's models was chosen to be presented as the proposed solution.

This von Mises stress contour shows a small section of the runway surface.

The 2000 meter runway extension over the Atlantic Ocean will be 180 meters wide and will rise over 60 meters above the ocean surface. It will rest on hundreds of three meter diameter columns founded on the sea bed by piles. The cost of the runway extension, together with the cost of upgrading airport buildings and adjoining roads, is estimated to be around $400 million. Construction is expected to begin soon.

Analyzing for the Worst

Mr. Calixto da Silva first tested the base project given to him by the consortium. As part of the design process, he tested for disasters such as hurricanes, earthquakes, airplane crashes and shipwrecks into the base, as well as the "normal" stresses of landing large aircraft. Stress, heat transfer, natural frequency (modal), buckling and random vibration analyses were all conducted.

"The results of the Algor analyses helped to identify possible problems and allowed us to deal with them at an early stage, rather than late in the bidding process, where the consequences might have been very costly," said Mr. Calixto da Silva.

The Panoramic Elevator

In a separate project, Mr. Calixto da Silva and J. Ribeiro da Silva were appointed by Hidroenergia, Lda. to design a panoramic elevator up a highly irregular cliff on the west side of Madeira Island. The 250 meter structure also included a steel penstock to control the flow of water into a small hydro-electric power station at the top of the cliff.

A number of factors had to be taken into account, such as wind, thermal stress from the afternoon sun, vibration and the force of gravity for such a huge and weighty object in proportion to the supporting structure.

Jos? C. Calixto da Silva and J. Ribeiro da Silva at work on the panoramic elevator.

The Analyses

The analyses performed on the model of the elevator/penstock structure included an elastic linear static stress analyses of the gravity, wind induced and thermal induced loads, as well as a buckling analysis for the worst loading situations.

A modal analysis was also performed to determine the natural periods and modes of vibration of the structure. Seismic effects were determined by a power density spectral analysis. A frequency response analysis determined the possible alternating forces generated by wind fluttering.

The Results

A heat transfer analysis helped the engineers determine that the supports had to be modified and provisions had to be made to allow for additional longitudinal thermal deformation. In addition, supports near the base of the support structure were modified to increase the safety margin, based on the results of the buckling analysis.

The results of the analyses proved that the structure was feasible without being overly-expensive, and that safety could be satisfied under the applicable regulations.

"For example, wind excitation and seismic activity would not endanger people traveling along the cliff wall in the elevator at the time of such an event," said Mr. Calixto da Silva.

This analysis shows the displacement of the elevator's support structure when force is applied.

About Algor

"Algor software has the great advantage of ease-of-use, yet is remarkably accurate. The software incorporates several specialized modules, enabling several different types of analysis which must be performed for 'out of the ordinary' civil engineering structures," said Mr. Calixto da Silva.

"This makes Algor quite suitable for design offices that deal with state-of-the-art civil engineering structures and venture into bold new designs.

"In the past, Algor has been seen mostly as a mechanical engineering oriented program; however, it is a package better suited than most to meet the needs of civil and structural engineering analysis."

These pictures show the panoramic elevator under construction. The elevator has been completed and is currently in use.