PSI - Issue 84

Galileo Tamasi et al. / Procedia Structural Integrity 84 (2026) 709–716

710

Keywords: structural analysis; girder bridge decks; 1970s software; strength and stiffness; infrastructure heritage.

1. Introduction In the contemporary engineering landscape, advanced numerical modeling marks a significant departure from the early digital revolution in Italy (Ausiello and Gambosi, 2021; De Marco et al., 1999; Gadducci and Cignoni, 2013). However, modern computational complexity can often obscure the core mechanical principles and design rationale underpinning our infrastructural heritage (Benvenuto, 1991; Kurrer and Ramm, 2018; Wells, 2010). This study re examines the 1970s analytical framework for girder bridges, demonstrating how a "simulated design" based on historical tools provides a transparent validation of existing structures. During the 1970s, structural analysis relied on an intimate connection between the engineer and calculation logic. Software routines were published as open-source listings for manual entry into programmable calculators from Olivetti, Hewlett-Packard, and Texas Instruments. Utilizing magnetic card storage - pioneered by the Olivetti Programma 101 - this "manual-digital" workflow ensured that structural models were built upon a rigorous understanding of mathematical assumptions and hardware limitations. Today, recreating these pathways is a necessity for the "clinical history" of bridges with incomplete documentation. Adopting the original analytical logic allows engineers to predict reinforcement placement; when corroborated by field investigations, this achieves higher Confidence Levels (LC) under current Italian standards. Ultimately, grasping the original design philosophy is fundamental for the informed inspection, maintenance, and strategic reinforcement of aging bridge stocks that form the backbone of modern transportation networks. 2. From desktop units to handheld programmables: the 1970s computational landscape The shift from purely mechanical or early electronic devices to the modern personal computing era was bridged by the emergence of programmable calculators, which became the computational backbone for engineering firms in the 1970s. A landmark in this evolution was the 1965 introduction of the Olivetti Programma 101, designed by Pier Giorgio Perotto, Giovanni De Sandre, Gastone Garziera, Giancarlo Toppi e Giuliano Gaiti (Campbell-Kelly and Aspray, 2000; Perotto, 2015). Although it lacked portability, the P101 pioneered the use of magnetic cards for archiving and executing routines, facilitating a primitive yet effective form of software sharing. With a capacity of 120 program steps and eight memory registers, it allowed for sophisticated operations (Penserini, 1973). As the 1970s progressed, industry saw a surge in portable units from Hewlett-Packard and Texas Instruments, which revolutionized the speed and accuracy of scientific computations. Hewlett-Packard (HP) distinguished its devices through Reverse Polish Notation (RPN), a stack-based logic that improved calculation efficiency (Mier-Jedrzejowicz and Power, 2022; Mier-Jedrzejowicz and Wales, 2002). Before the rise of handheld units, the HP 9800 series - specifically desktop models like the HP 9810A (1971) - provided the power necessary for matrix manipulation. The subsequent release of the HP-35 (1972) as the first pocket scientific calculator was followed by the HP-65 (1974), which introduced programmability to a handheld format. This was further expanded by the HP-67 (1976) and its desktop counterpart, the HP-97 (1977), which provided a thermal printer for the documented verification of results essential for professional practice. The lineage culminated in the HP-41C (1979), setting a new standard with its alphanumeric interface and expandable memory modules. In contrast, Texas Instruments (TI) favored the Algebraic Operating System (AOS). After entering the market with the SR-50 (1974), TI released the programmable SR-52 (1975), featuring magnetic card storage. The subsequent TI 58 (1977) introduced "Solid State Software" via interchangeable ROM modules, while the flagship TI-59 (1977) provided an unprecedented 960 program steps and 100 registers. Meanwhile, Olivetti continued to evolve its desktop line with the Logos 68 and 75 series and the P6040 (1975), which featured minidisk storage. By the close of the decade, these diverse computational tools had fundamentally restructured the engineering workflow, replacing tedious manual iterations with automated, reproducible routines. This historical reconstruction is corroborated by the extensive bibliographic data (Gross, 2025). This archive confirms that the mid-1970s represented the global peak for the dissemination of structural engineering routines via printed media, providing a verifiable map of the "open-source" logic of that era (see Fig. 1). As noted by Gross, this