Abstract

The equilibrium of spherical domes is a fundamental topic in structural engineering, particularly for masonry structures, where the material’s inability to resist tension influences the force distribution. This study proposes an integral formulation for the equilibrium of a spherical dome, incorporating normal stresses and shear stresses, explicitly considering their spatial variations. The formulation extends classical membrane and bending theories by integrating the effects of stress gradients and torsional moments, providing a more detailed understanding of force equilibrium. The proposed approach aligns with and extends the concept of thrust surfaces, as discussed by Sajtos et al. (2020), introducing a framework that accommodates general force distributions and possible cracking patterns. The results suggest that the inclusion of moment equilibrium considerations leads to a more precise determination of the structural safety of cracked domes. This study contributes to the ongoing research on the stability and failure mechanisms of domes by offering a more comprehensive analytical framework.

Abstract

This paper addresses the concept of structural robustness in buildings, particularly focusing on progressive collapse, a phenomenon where localized damage leads to widespread structural failure. Resilient buildings are designed to maintain adequate performance during unexpected extraordinary events, such as explosions, impacts, or earthquakes, yet defining "adequate" performance remains complex. Design codes often refer to the "proportion" between accidental events and their consequences, highlighting the need for a deeper understanding of progressive collapse. This collapse occurs through a series of failures in structural elements, such as beams and columns, which trigger a dynamic load redistribution and result in a catastrophic domino effect. Examples of progressive collapse, such as the Ronan Point Building collapse in 1968 and the World Trade Center collapse in 2001, have driven research and regulatory efforts in this field. While strengthening all structural elements could improve a building's damage tolerance, this approach is costly. Alternative strategies, such as redundancy and compartmentalization, are commonly used, but their effectiveness is still debated. Similarly, although anti-seismic design enhances progressive collapse resistance, it does not represent the optimal strategy for maximizing resistance. This study emphasizes the limitations of current design codes and the need for improved analytical models of progressive collapse. The paper introduces a new simulation method based on the Discrete Element Method (DEM) to conduct large-scale parametric studies. This approach is used to identify collapse mechanisms and develop kinematic models to analyze and generalize simulation results. By extending the P-Δ method to both intact and damaged structures, simplified formulas are derived for calculating collapse loads and progressive collapse resistance. The methodology is applied to investigate the progressive collapse of 2D reinforced concrete frames subjected to the sudden removal of beams and columns. The findings highlight the importance of designing structures that can redistribute and dissipate loads, utilizing the ductility of components to avoid fragile failure behavior. Robustness Interpretation of Intact and Damaged Framed Structures EUR ING Alessandro Calvi

Abstract

This paper deals with the issue of structural collapse considering an analogy between ductilebrittle transition of materials, taking into account the current literature which also considers the number of fragility and the stress intensification factor in the presence of crack, with extension on a larger scale involving framed structures subjected to increasing vertical loads. It is evaluated the ductile-fragile transition in relation to concrete frames with different structural hierarchy (2x2, 5x5, 11x11).

Abstract

Hydropower plant future production estimation is based on hydrological-hydraulic data. The present metholodogy validates the median as the reference parameter to be used for a better interpretation of statistical series, because it is a centered value where duration curves and their complementary curves intersect. Then, it is not affected by extreme events, providing a well representation of the whole dataset.

Abstract

The Himalayan region, characterized by complex geological formations and high tectonic activity, presents significant challenges for tunnel construction. This paper examines geomechanical issues such as tunnel squeezing, stress-induced instability, and rock bursting, with a focus on hydropower and railway tunnel projects in Nepal and India. Case studies, including the Chameliya Hydroelectric Project, Parbati II Hydroelectric Project, Nilgirikhola Hydroelectric Project, and railway tunnels in the Garhwal Himalaya, highlight the impact of weak, schistose rock masses and extreme overburden pressures. Various engineering methodologies, including empirical, semianalytical, analytical, and numerical modeling approaches, are discussed to assess stress states and deformation behavior. The study underscores the need for adaptive excavation techniques, such as the New Austrian Tunneling Method (NATM) and rock mass classification systems, to ensure tunnel stability. By integrating probabilistic analysis and advanced support systems, this research contributes to optimizing underground construction strategies in geologically challenging terrains.

Abstract

This thesis is divided into two parts: in the first part the collapse of the WTC1, WTC 2 (Twin Towers) and WTC 7 buildings following the terrorist attacks of 11 September 2001 is analysed. In the second part, the collapse type and strength of frame buildings with different topological characteristics. What links the two parts is structural robustness. Below is an overview of the work with a description of the topic covered in each Chapter. Chapter 1: description of the structural and fire protection characteristics of the WTC 1, WTC 2 and WTC 7 buildings. Chapter 2: timeline of the terrorist events of September 11, 2001. Chapter 3: description of the types of fire, the performance of structures and the behavior of the main building materials (steel, concrete) to fire. Chapter 4: analysis of the main hypotheses of the collapse of the Twin Towers present in the literature. Chapter 5: definition of structural robustness, structural toughness, vulnerability. Description of project strategies to prevent progressive collapses. Chapter 6: measurement of the structural strength of buildings with a reinforced concrete frame structure. through Discrete Element simulations (DEM). Chapter 7: discussion of progressive collapse due to impacts from an analytical and bibliographical point of view.

Abstract

Tunnel collapse is a critical issue in geotechnical engineering, affecting the safety, functionality, and economic viability of underground structures. This study examines the primary failure mechanisms of tunnels, including roof instability, shear failure of sidewalls, base heave, wedge failure, and progressive collapse, with a particular focus on hydropower tunnels. The role of principal stress directions and stress redistribution in failure processes is analyzed, highlighting the effects of excavation-induced unloading, in situ stress concentration, and external influences such as groundwater infiltration and seismic activity. Special attention is given to hydropower tunnels, where transient hydrostatic pressure variations, mineralogical degradation, and high in situ stresses increase the likelihood of collapse. The study integrates limit analysis and fracture mechanics to model tunnel failure mechanisms, emphasizing how plastic deformation and crack propagation contribute to instability. Numerical simulations and real-world case studies illustrate the interaction between stress conditions and structural response. The findings suggest that tunnel stability is rarely governed by a single factor but rather by a combination of geological, structural, and environmental influences that evolve over time. Future research should focus on the development of real-time monitoring systems using artificial

Abstract

In this paper, a number of innovative technologies are presented that have the potential to improve the efficiency and utilization of hydropower. These technologies include new turbine designs, improved efficiency, small hydro.

Abstract

Robustness plays a relevant role in the capacity of a structure to sustain abnormal loads or to deal with unexpected events with large effects, such as explosions and terroristic attacks. Such situations on dams may have extremely large consequences. For buildings, the design approach that best implements robustness concepts is represented by the so called “Consequence Based Design”: even if nothing is known about the cause, selective element removals and extreme load on the structure are modeled, and their effects are determined with respect to progressive collapse and damage arrest. In the paper we try to set-up a “Consequence Based Assessment” of a typical example of a gravity dam built between the ‘30s and ‘40s of the last century in the northwestern Italian Alps. A simplified model of the structure is adopted. Removal of parts of the dam cross-section is assumed to occur: the effects of the extent of damage is discussed on the bases of the tension generated within the body of the dam