PSI - Issue 78

Galileo Tamasi et al. / Procedia Structural Integrity 78 (2026) 883–890

886

the era (Bianco, 1979; De Miranda, 1971; Petrangeli, 1980; Raithel, 1964; Rinaldi, 1974). Slide rules were still common (Pastore, 2006), though scientific and programmable calculators (like the HP67/97) were emerging, significantly reducing computation tim e for sequential routines. Specialized handbooks such as Santarella’s Prontuario (Santarella, 1975), the Beton- Kalender (Zoccoli and Andreon, 1972), Kleinlogel’s frame studies (Kleinlogel and Haselbach, 1973), and Guldan’s elastic frame analysis (Guldan, 1 959, 1956) were also crucial for quick estimations. While early structural software existed, it was typically in-house, mainframe-based, and used for more complex analyses like spatial frames or shell structures. The prefabrication industry, notably RDB of Piacenza, provided valuable technical guides and design aids for prestressed concrete elements. Professional associations (e.g., AICAP) and journals like L’ Industria Italiana del Cemento also helped keep engineers updated on evolving practices. The design process was highly iterative. After defining the structural scheme (simply supported beams, continuous beams, Gerber beams, etc.), preliminary sizing was performed using established formulas. Load analysis included dead loads, traffic, seismic actions (via equivalent static methods), and prestressing forces with losses. Classical methods were employed for stress calculations, often with the aid of programmable calculators for solving linear systems and iterations. Even simple modal analyses for longitudinal dynamic behavior were possible with the limited memory of these calculators. Section checks ensured stresses remained within material limits, often using nomograms for early limit state criteria. Tendon profiles were optimized, and shear reinforcement designed. Foundations and bearings were sized for vertical and horizontal loads, and construction details for reinforcement, cables, expansion joints, and damping devices were specified. Seismic verification focused on static equivalent horizontal forces. For simpler prestressed concrete bridges, such as short-span highway viaducts, prefabricated precalculated precast beams were a common choice, supplied by specialized companies like RDB Piacenza along with design manuals. For conventional reinforced concrete bridges, comprehensive field design manuals were commonly used by engineers (Frangipani, 1950; Monti and Briani, 1971). 5. Birth and evolution of programmable calculators Programmable calculators represented a crucial transitional period between traditional mechanical/electronic calculators and the advent of personal computers. A significant early development was the Olivetti Programma 101 in 1965, conceptualized by Perotto (Campbell-Kelly and Aspray, 2000; Perotto, 2015). Although not portable, this machine introduced programmability through magnetic cards, enabling the storage, execution, and sharing of routines — a nascent form of software exchange. It featured eight memory registers and could handle up to 120 program steps, with the capability to link multiple cards for more intricate operations. Programming was straightforward, achieved by recording key sequences (Penserini, 1973). The widespread availability of portable programmable calculators truly began in the early 1970s with offerings from Hewlett-Packard and Texas Instruments, paving the way for their extensive use in engineering and scientific disciplines (see Fig.3).

Fig. 3. Hewlett Packard calculators timeline.