Collapse Analysis of a Two-Span Reinforced Concrete Bridge Model

The continuous girder bridge is the main type of small- and medium-sized bridges; however, it has poor collapse resistance and suffers frequent earthquake damage. In order to grasp its collapse mechanism and clarify the internal and external factors affecting its collapse resistance, a 1:3-scaled, two-span bridge model subjected to shaking table test research was taken as the research object. The factors such as seismic characteristics, multi-directional seismic coupling, span, pier height, and structural system type were analyzed to determine the influences on the collapse mode of the bridge. The numerical results showed that different ground motion characteristics led to different collapse modes. Vertical ground motion had little effect on the structural response of the bridge. The change of span and pier height significantly changed the collapse resistance. A seismic isolation design could improve the anti-collapse performance, but the collapse mode varied with the system. The final anti-collapse design suggestions could provide reference for the seismic reinforcement of existing continuous girder bridges and the seismic design of continuous girder bridges that will be constructed.

THE “FLU SEASONS” AND THE MISSING DATA: A MATCHED-PAIR ANALYSIS FOR THE PANDEMIC SEASON 2019_2020

The unit cell from the McNemar’s 2x2 Table denotes the week with col (1, 2) and the Public Health Region with Row (1, 2). We calculate the standard normal statistic (z) for A(H1), A(H3), Influenza B. Each one categorical unit is in fact a pair of matched-pair data within its own partial table. The Cochran-Mantel-Haenszel Test collapses these partial tables to summate these 2n observations in a 2x2 x n contingency table to yield the marginal counts of the McNemar’s test. The open data for Europe/Asia began this SARS-CoV2 pandemic, from week 3 to week 14, with the normal statistic (z) entering into an identical collapse mode. These all assumed the same “V” curve as the general collapse pattern and they rippled together without overlapping. During this period China applied mandatory lockdown and they mandated masks. We should strive to be more evidence-based so that we can convince more of the general public to accept the public health measures to survive.

PROGRESSIVE COLLAPSE RESISTANCE OF STEEL FRAMED BUILDINGS UNDER EXTREME EVENTS

This paper presents experimental and theoretical investigations on progressive collapse behavior of steel framed structures subjected to an extreme load such as fire, blast and impact. A new capacity-based index is proposed to quantify robustness of structures. An energy-based theoretical model is also proposed to quantify the effect of concrete slabs on collapse resistance of structures. The experimental results show that the dynamic amplification factors of frames subject to impact or blast are much less than the conventional value of 2.0. The collapse process of frames in fire can be either static or dynamic depending on the restraint conditions and load levels. It is necessary to account for the failure time and residual strength of blast-exposed columns for assessing the collapse resistance of structures subject to explosion. Two collapse modes of steel frames under blast or impact are found: connection-induced collapse mode and column-induced collapse mode. In case of fire, a frame may collapse due to either column buckling or pulling-in effect of beams. The energy dissipation from elongation of slab reinforcement and additional resultant moment greatly contribute to the collapse resistance of structures.

Rehabilitation of Masonry Buildings with Fibre Reinforced Mortar: Practical Design Considerations Concerning Seismic Resistance

Historic masonry buildings experience a high seismic vulnerability: innovative intervention strategies for strengthening, based on the use of fibre-based composite materials are gradually spreading. In particular, the coupling of fibre-based materials with mortar layers (Fibre Reinforced Mortar technique - FRM) evidenced a good chemical and mechanical compatibility with the historical masonry and proved to be effective for the enhancement of both in-plane and out-of-plane performances of masonry, contrasting the opening of cracks and improving both resistance and ductility. The resistant mechanisms that arise in FRM strengthened masonry walls subjected to in-plane horizontal actions are analyzed in the paper and a practical design approach to evaluate their performances is illustrated, evidencing the dominant collapse mode at the varying of the masonry characteristics. Some masonry walls are analyzed numerically and analytically, as “case study”.

A Review on Analytical Modeling for Collapse Mode Capacitive Micromachined Ultrasonic Transducer of the Collapse Voltage and the Static Membrane Deflections

Analytical modeling of capacitive micromachined ultrasonic transducer (CMUT) is one of the commonly used modeling methods and has the advantages of intuitive understanding of the physics of CMUTs and convergent when modeling of collapse mode CMUT. This review article summarizes analytical modeling of the collapse voltage and shows that the collapse voltage of a CMUT correlates with the effective gap height and the electrode area. There are analytical expressions for the collapse voltage. Modeling of the membrane deflections are characterized by governing equations from Timoshenko, von Kármán equations and the 2D plate equation, and solved by various methods such as Galerkin’s method and perturbation method. Analytical expressions from Timoshenko’s equation can be used for small deflections, while analytical expression from von Kármán equations can be used for both small and large deflections.

Influencing Factors for the Instability and Collapse Mode of the Goaf Structure in a Gypsum Mine

Large-area goafs in a gypsum mine tend to collapse after 10 or more years, but the influencing factors are still unclear, and the effects of multiple factors have not been comprehensively considered. In this study, the failure mechanism and collapse mode of the room-pillar goaf structure were analyzed, and the uniaxial compressive strength tests of the pillars under different conditions were carried out in a laboratory. The influences of water, temperature, and time on the strength of the gypsum rock were considered. These three factors weakened the gypsum rock in different degrees. After 120 days of immersion, water had the greatest effect with a strength-weakening rate of 52.61%. After 20 temperature cycles, changes in temperature had little effect with a strength-weakening rate of 12.60%. After 25 years of aging, the strength-weakening rate of time was 25.13%. These results show how different factors affect the instability and collapse of the goaf structure, which are of great significance for predicting and preventing this from happening.

Least-thickness symmetric circular masonry arch of maximum horizontal thrust

This analytical note shall provide a contribution to the understanding of general principles in the Mechanics of (symmetric circular) masonry arches. Within a mainstream of previous research work by the authors (and competent framing in the dedicated literature), devoted to investigate the classical structural optimization problem leading to the least-thickness condition under self-weight (“Couplet-Heyman problem”), and the relevant characteristics of the purely rotational five-hinge collapse mode, new and complementary information is here analytically derived. Peculiar extremal conditions are explicitly inspected, as those leading to the maximum intrinsic non-dimensional horizontal thrust and to the foremost wide angular inner-hinge position from the crown, both occurring for specific instances of over-complete (horseshoe) arches. The whole is obtained, and confronted, for three typical solution cases, i.e., Heyman, “CCR” and Milankovitch instances, all together, by full closed-form explicit representations, and elucidated by relevant illustrations.