2,243 publications from this institution
The results of a testing campaign are presented for rolled steel equal angle sections strengthened with Carbon Fiber Reinforced Polymers (CFRP) plates, targeting the strengthening of existing steel lattice towers. Three-point bending and compression tests have been carried out in order to determine the mechanical properties of members, specifically the bending capacity to principal and geometric axis loading and the buckling strength in the absence or presence of loading eccentricity arising from the connection in one leg. The experimental data include actual material properties, geometrical imperfections, the recorded response to loading in terms of displacements, end-rotations, twist of section, strains in steel or CFRP material, and photos. Also, the experimental set-up, the instrumentation, as well as simple experimental results to indicate the strengthening effect and utility of them to further analyses are provided.
Abstract Duchenne muscular dystrophy ( DMD ) is an X‐linked muscle disorder characterized by progressive and irreversible loss of muscular function. As muscular disease progresses, the repair mechanisms cannot compensate for cellular damage, leading inevitably to necrosis and progressive replacement by fibrous and fatty tissue. Cardiomyopathy and respiratory failure are the main causes of death in DMD . In addition to the well‐described muscle and heart disease, cognitive dysfunction affects around 30% of DMD boys. Myocardial fibrosis, assessed by late gadolinium enhancement ( LGE ), using cardiovascular magnetic resonance imaging ( CMR ), is an early marker of heart involvement in both DMD patients and female carriers. In parallel, brain MRI identifies smaller total brain volume, smaller grey matter volume, lower white matter fractional anisotropy and higher white matter radial diffusivity in DMD patients. The in vivo brain evaluation of mdx mice, a surrogate animal model of DMD , showed an increased inorganic phosphate (P(i))/phosphocreatine ( PC r) and pH . In this paper, we propose a holistic approach using techniques of magnetic resonance imaging, spectroscopy and diffusion tensor imaging as a tool to create a “heart and brain imaging map” in DMD patients that could potentially facilitate the patients’ risk stratification and also future research studies in the field.
Summary The seismic design of an eight‐story reinforced concrete space frame building is undertaken using a yield frequency spectra (YFS) performance‐based approach. YFS offer a visual representation of the entire range of a system's performance in terms of the mean annual frequency (MAF) of exceeding arbitrary global ductility or displacement levels versus the base shear strength. As such, the YFS framework can establish the required base shear and corresponding first‐mode period to satisfy arbitrary performance objectives for any structure that may be approximated by a single‐degree‐of‐freedom system with given yield displacement and capacity curve shape. For the eight‐story case study building, deformation checking is the governing limit state. A conventional code‐based design was performed using seismic intensities tied to the desired MAF for safety checking. Then, the YFS‐based approach was employed to redesign the resulting structure working backwards from the desired MAF of response (rather than intensity) to estimate an appropriate value of seismic intensity for use within a typical engineering design process. For this high‐seismicity and high‐importance midrise building, a stiffer system with higher base shear strength was thus derived. Moreover, performance assessment via incremental dynamic analysis showed that while the code‐design did not meet the required performance objective, the YFS‐based redesign needed only pushover analysis results to offer a near‐optimal design outcome. The rapid convergence of the method in a single design/analysis iteration emphasized its efficiency and practicability as a design aid for practical application. Copyright © 2017 John Wiley & Sons, Ltd.
The incorporation of industrial by-products such as fly ash (FA) into cementitious materials plays a vital role in promoting environmental sustainability during cement production. This study evaluates the feasibility of using siliceous fuel fly ash, sourced from thermal power stations in the Rhenish region of Germany, as a partial cement replacement in mortar formulations. Mortar specimens with FA replacement levels ranging from 5 wt% to 30 wt% were prepared and tested. Data were collected through standardized laboratory testing of mechanical properties (compressive and flexural strength), physical characteristics (porosity, sorptivity) and microstructural analysis via SEM and XRD. The results showed that increasing FA content generally led to reductions in strength and increases in porosity and sorptivity, due to the mineralogical composition and higher water demand linked to the porous FA structure. However, when FA was used at levels not exceeding 10 wt%, the physical and mechanical properties remained within acceptable limits for construction applications. Additionally, the use of plasticizing admixtures proved effective in mitigating workability and strength issues by reducing the water-to-binder ratio. These findings highlight that, despite certain limitations, siliceous FA can be safely and effectively used in low percentages, contributing to sustainable mortar production and reducing reliance on Portland cement. In addition, the use of fly ash contributes to reduced CO2 emissions and lower production costs, promoting sustainable and cost-efficient construction solutions.
This chapter considers the linear and nonlinear dynamic of discrete systems having more than one degree of freedom in the time domain. Linear elastic systems are those that experience small deformations, in which the stiffness is constant. The chapter develops the equation of motion for the simplest multi-degree-of-freedom (MDOF) system. It considers the effect of motion of the reference frame, which could be due to earthquake-induced ground motion. The chapter addresses nonlinearity in the force-displacement response of structural components and geometric effects. It discusses drawbacks associated with using Rayleigh damping for linear systems—mainly that the ß term introduces unrealistically high amounts of damping in higher modes and the a term lacks physical plausibility. As nonlinearity develops, softening causes a reduction in the instantaneous modal frequencies.
Five different design approaches are compared on a single mid-rise reinforced concrete building, pitting two performance-based designs against three conventional methods in delivering a solution that satisfies different sets of performance objectives. Two of the conventional designs stem from the literature, and they represent 2003 IBC compatible solutions. Another employs the yield point spectra to deliver a code-like solution, satisfying the design norms without needing iterations. The final two are based on the yield frequency spectra to offer a design that can satisfy more detailed performance objectives in a single step. Overall, all five methods are shown to deliver what is expected. Conventional methods can safely capture the code requirements, yet they are disadvantaged when treading in beyond-life-safety territory, where Immediate Occupancy or Collapse Prevention objectives cannot be easily satisfied, a problem that is not shared by performance-based approaches.
In this paper a robust method for simplified prediction of peak floor acceleration (PFA) demands in inelastic structural walls is established.In structural walls the plastic mechanism is usually confined to the domain right above the foundation.It is, thus, reasonable to assume that in wall structures only the response contribution related to the fundamental mode is significantly affected by inelastic deformations.Based on this assumption, a readily developed complete-quadratic-combination (CQC) modal superposition rule for elastic median PFA demand prediction is specialized to inelastic structural walls.In this approach, only the first mode contribution on the PFA demand is affected by inelastic deformations, related to the lateral strength reduction factor identified from the outcomes of a first mode pushover analysis.Since the response contribution of the higher modes is assumed to be elastic, for these modes the relations derived for unlimited elastic structural behavior enter the specialized response spectrum method.Application on a 12-story shear wall shows the accuracy of the predicted median PFA demands derived by the proposed procedure.
A seismic‐resistant steel frame with energy‐dissipating, chevron‐type braces is proposed. The braces are equipped with replaceable hourglass‐shaped pins made of duplex stainless steel. Under design seismic loading, energy is dissipated through inelastic deformations confined in the replaceable pins while the other members remain essentially elastic. As a result, the frame exhibits high post‐yield stiffness due to the inherent properties of the stainless‐steel pins. A Eurocode‐8‐based design methodology is adopted for the frame and assessed following the Eurocode‐8‐compatible INNOSEIS approach. Specifically, the overstrength factor is evaluated through nonlinear pushover analysis while the behaviour factor is assessed through incremental dynamic analysis considering high and medium seismicity site‐specific ground motion suites. The determined behaviour factor satisfies the global collapse prevention and life safety objectives while also keeping the maximum residual inter‐storey drifts below 1/300 to permit an easy substitution of the damaged pins after the design level earthquake.
