Strengthening of Rural Bridges using Rapid-Installation FRP Technology: Route 63 Bridge No. H356, Phelps County

This report presents the use of externally bonded fiber reinforced polymers (FRP) laminates for the flexural strengthening of a concrete bridge. The bridge selected for this project is a two-span simply supported reinforced concrete slab with no transverse steel reinforcement located in Phelps County, MO. The original construction combined with the presence of very rigid parapets caused the formation of a 1-inch wide longitudinal crack, which resulted in the slab to behave as two separate elements. The structural behavior was verified using a finite element model (FEM) of the bridge. The bridge analysis was performed for maximum loads determined in accordance with AASHTO 4th edition. The strengthening scheme was designed in compliance with the ACI 440.2R-08 design guide for externally bonded FRP materials, to avoid further cracking and such that the transverse flexural capacity be higher than the cracking moment. The FRP strengthening technique was rapidly implemented. After the strengthening, a load test was performed to validate the bridge model and evaluate the structural behavior according to the AASHTO specifications. The bridge deck was retrofitted after the longitudinal crack was injected with epoxy to allow continuity in the cross section

Design, Construction and Load Testing of the Bridge on Arnault Branch, Washington County, Missouri using Innovative Technologies

The superstructure and instrumentation designs of a three-span bridge are presented in this report. The three spans include a precast box-girder bridge, a precast deck on steel girder and a precast deck on concrete girder. They were designed to compare the performance of various bridge decks reinforced with fiber reinforced polymers (FRP) through field instrumentations. A wireless monitoring system was designed to facilitate the collection of field data after the completion of bridge construction. The collected data will allow the study of FRP bars and stay-in-place FRP grid systems

Condition Assessment of Bill Emerson Memorial Cable-Stayed Bridge under Postulated Design Earthquake

In this study, a three-dimensional finite element model of the Bill Emerson Memorial cable-stayed bridge was developed and validated with the acceleration data recorded during the M4.1 earthquake of May 1, 2005, in Manila, Arkansas. The model took into account the geometric nonlinear properties associated with cable sagging and soil-foundation-structure interaction. The validated model was used to evaluate the performance of a seismic protective system, the behavior of cable-stayed spans, and the accuracy of two simplified bridge models that have been extensively used by the structural control community. The calculated natural frequencies and mode shapes correlated well with the measured data. Except that the hollow columns of two H-shaped towers were near yielding immediately above their capbeams, the cable-stayed spans behaved elastically as expected under the design earthquake that was scaled up from the recorded rock motions at the bridge site. The minimum factor of safety of all cables is 2.78, which is slightly greater than the design target

The Gross-Pitaevskii Model of Spinor BEC

The Gross-Pitaevskii model of spinor Bose-Einstein condensates is studied. Using the abstract results obtained for infinite-dimensional Hamilton system, we establish the mathematical theory for the model of spinor BEC. Furthermore, three conservative quantities of spinor BEC, that is, the energy, total particle number, and magnetization intensity, are also proved

IEEE Access Special Section Editorial: Secure Modulations for Future Wireless Communications and Mobile Networks

Security has become an extremely important research topic in wireless networks over the last decade, as it is intimately related to both individual privacy and national security. Directional modulation, as a conventional type of secure modulations, transmits confidential information along the desired directions of legitimate receivers, and artificial noise in other directions, to deliberately confuse eavesdroppers in line-of-sight channels. Recently, artificial noise is also introduced into spatial modulation, leading to a secure spatial modulation strategy. In this Special Section in IEEE A CCESS, secure modulation is defined broadly as any secure modulation method, which includes, but is not limited to, secure directional modulation, secure spatial modulation, and secure index modulation

Assessment of the Bill Emerson Memorial Cable-Stayed Bridge based on Seismic Instrumentation Data

In this study, both ambient and earthquake data measured from the Bill Emerson Memorial Cable-stayed Bridge are reported and analyzed. Based on the seismic instrumentation data, the vibration characteristics of the bridge are investigated and used to validate a three-dimensional Finite Element (3-D FE) model of the bridge structure. The 3-D model is rigorous and comprehensive, representing realistic dynamic behaviors of the bridge. It takes into account the geometric nonlinear properties caused by cable sagging and soil-foundation-structure interaction in the Illinois approach of the bridge. The FE model is successfully verified and validated by using the natural frequencies and mode shapes of the bridge extracted from the measured data. With the calibrated model, time history analyses were performed to assess the condition of the bridge structure under a postulated design earthquake. Since the FE model is developed according to as-built drawings, the calibrated model can be used as a benchmark for safety evaluation and health monitoring of the cable-stayed bridge in the future

Concrete Surface with Nano-Particle Additives for Improved Wearing Resistance to Increase Truck Traffic

This study focused on the use of nanotechnology in concrete to improve the wearing resistance of concrete. The nano materials used were polymer cross-linked aerogels, carbon nanotubes, and nano-SiO2, nano-CaCO3, and nano-Al2O3 particles. As an indirect measurement of the concrete wearing resistance, the tensile and compressive properties and the permeability of concrete were evaluated for various mix designs. The optimal amount of nano material additives were determined following the American Society of Testing Methods (ASTM) standard test methodologies. The test results from the materials were compared for their mechanical behaviors. This type of technology may potentially improve the comfort level of passengers, the safety of highway operations, and the efficiency of fuel consumptions. It may also reduce the emission of CO2 associated with the poor condition of roadways

Elastic recovery of monocrystalline silicon during ultra-fine rotational grinding

Micromachining of brittle materials like monocrystalline silicon to obtain deterministic surface topography is a 21st Century challenge. As the scale of machining has shrunk down to sub-micrometre dimensions, the undulations in the machined topography start to overlap with the extent of elastic recovery (spring back) of the workpiece, posing challenges in the accurate estimation of the material's elastic recovery effect. The quantification of elastic recovery is rather complex in the grinding operation due to (i) randomness in the engagement of various grit sizes with the workpiece as well as (ii) the high strain rate employed during grinding as opposed to single grit scratch tests employed in the past at low strain rates. Here in this work, a method employing inclination of workpiece surface was proposed to quantify elastic recovery of silicon in ultra-fine rotational grinding. The method uniquely enables experimental extraction of the elastic recovery and tip radius of the grits actively engaged with the workpiece at the end of the ultra-fine grinding operation. The proposed experimental method paves the way to enable a number of experimental and simulation endeavours to develop more accurate material constitutive models and grinding models targeted towards precision processing of materials. It can also be shown that using this method if the tip radius distribution of active grits is measured at different time instances, then this data can be used to assess the state of the grinding wheel to monitor its wear rate which will be a useful testbed to create a digital twin in the general framework of digital manufacturing processes