Effect of vehicular loading on suspension bridge dynamic properties

Journal ArticleSince the 1970s, many researchers have attempted to use changes in natural frequencies as means for condition assessment of large civil engineering structures such as bridges, but have faced the challenge of decoupling frequency variations apparently caused by changing operational conditions. In the case of the Tamar Bridge in southwest England, the time series of natural frequencies exhibit diurnal variations resulting from a combination of thermal and vehicular loading, the effects of which would need to be compensated for in dynamics-based assessment. By examining monitored data for several years, the effects of traffic mass have been characterised and compared with other operational effects. While temperature changes appear to have a greater influence for lateral modes, traffic mass is a strong factor in all modes and the dominant factor for the vertical and torsional modes evaluated. Physics-based explanations for the variable effects of vehicle mass have been sought using a finite element model calibrated against experimental data. As a caution for performance prediction in structural dynamics, while acceptable reconciliation of natural frequencies from FE model and measurements was achievable, reconciling simulated effects of changing mass with observed behaviour has not been straightforward due to the complexity of the retrofitted suspension bridge structure studied.EPSRCEU Framework

Using quantum effects in nanomaterials for unique identification

Authentication and identification are critical to information security systems. Traditionally, these processes are achieved with the use of secret keys that are stored in electronic memories, or with difficult-to-clone systems (e.g., fingerprints or holograms). The persistent development of technology, however, means that the barrier to cloning such systems is becoming lower. Moreover, counterfeiting, device spoofing, and identity fraud are formidable problems in all markets. The ideal solution, therefore, would be to produce a nano-fingerprint from the atomic arrangement of a structure embedded within a device. By shrinking down to the atomic scale, the challenge of cloning the system becomes as difficult as possible, i.e., the density of secure information is maximized and the number of resources required to read the fingerprint is minimized

Effect of solar radiation on suspension bridge performance

© 2014 American Society of Civil Engineers.Observations of a U.K. suspension bridge show that thermal expansion and contraction cycles do not follow simple linear relationships with a single temperature value and that time lag and temperature distribution can be significant factors. This investigation explores these effects by simulating the transient thermal and quasistatic response of the Tamar Bridge with separate finite-element models of the bridge and suspension cables. Thermal loads are determined by calculated solar radiation intensities and temperature data from the bridge monitoring system. Because cloud cover plays an important role in the levels of solar radiation, cloud coverage was estimated indirectly using monitored temperature differences between the top and bottom of the suspended structure. The results demonstrate that peak temperatures of the suspended structure and cables occur at different times. The lag is caused by differing material properties and the surfaces' ability to absorb and lose heat. Transient phenomena manifest in the structural responses such as the tower sway.EU FP7 project IRISEngineering and Physical Sciences Research Council (EPSRC

Understanding the dynamics of attitudes within a design and business focused collaboration

This paper aims to advance understanding about design’s unique contributions within collaborations between the disciplines of design and business. Collaboration between design and business functions is increasingly utilised as organisations seek to capitalise on a variety of knowledge and perspectives during the innovation process. Despite this increasing prevalence, the discipline of design can often be misunderstood by other disciplines within this particular interdisciplinary scenario due to the implicit knowledge that is central to the nature of design, which is often intangible and tacit in nature, yet provides designers with the capability to propose novel solutions to complex problem situations. This paper takes a deeper look at design attitude, which has previously been suggested to be one of the differentiators between design and other disciplines. The paper reflects on the results of a case study focusing on a collaboration between a multinational consumer goods company and a team of postgraduate students working out of a UK University. Data was obtained through observation, a reflective workshop and repertory grid based interviews. The originality of the paper lies in the way in which it categorises attitudes of different disciplines, in order to capture aspects of the design attitude that appear to be both unique and difficult for business focused people to adopt.Keywords: design attitude, multidisciplinary innovation, design knowledge

Separation, Fractionation and Mineralogy of Clays in Soils

This paper describes a working method for separation, fractionation and identification of colloid and colloidal clay minerals in soils. Technical information pertains to super-centrifugation, electron-microscopy and X-ray diffraction. On the basis of these techniques, twenty-two samples have been investigated in conjunction with a soil stud of pumping pavements. Soils were first dispersed and separated by gravity sedimentation. Fractionation was accomplished by controlled super-centrifugation. The separated fractions were purified and then analyzed by X-ray diffraction. Computed size fractions were checked by shadow castings and lineal dimensions on electron micrographs. Results include identification of the mineral or minerals present and the properties of the natural sample from which the colloidal fractions were extracted. These methods furnish a basis for more extensive research relating the behavior of the clay minerals and their contributions to the properties of soils

Calcium and magnesium absorption and retention by growing goats offered diets with different calcium sources

Calcium addition is necessary in order to balance the high phosphorus concentrations that are characteristic of high-concentrate ruminant diets. However, calcium sources differ in their bioavailability. Our objective was to determine apparent calcium and magnesium absorption and retention in goats offered diets containing different sources of calcium. Spanish-Boer goats (n = 18; 19.6 ± 1.88 kg) were stratified by body weight (BW) and sex and randomized to dietary treatments consisting of Purina Antlermax 16 containing either calcium carbonate (CC), Calmin (CM) or Milk Cal (MC). Goats were adapted to a control, corn-based high-concentrate diet on pasture and then moved to individual 1.0 × 1.5-m pens with plastic coated expanded metal floors, and adjusted to their respective diets along with removal of hay from the diet over a 7-d period. Goats were then offered their respective diets at a total of 2% of BW in equal feedings at 8:30 AM and 5:00 PM for an additional 14-d adaption period to diet and facilities followed by a 7-d collection of total urine and feces. Data were analyzed using PROC MIXED of SAS. Calcium and magnesium intake were not different (P ≥ 0.12) among diets. Calcium and magnesium apparent absorption and retention (g/d and % of intake) were greatest (P \u3c 0.05) in goats offered CC and did not differ (P ≥ 0.20) between goats offered the CM and MC diets. Therefore, calcium and magnesium were more available for goats from the diet containing calcium carbonate compared with diets containing Calmin and Milk Cal

The Mid-IR Spectral Effects of Darkening Agents and Porosity on the Silicate Surface Features of Airless Bodies

We systematically measured the mid-IR spectra of different mixtures of three silicates (antigorite, lizardite, and pure silica) with varying effective porosities and amounts of darkening agent (iron oxide and carbon). These spectra have broad implications for interpretation of current and future mission data for airless bodies, as well as for testing the capabilities of new instruments. Serpentines, such as antigorite and lizardite, are common to airless surfaces, and their mid-IR spectra in the presence of darkening agents and different surface porosities would be typical for those measured by spacecraft. Silica has only been measured in the plumes of Enceladus and presents exciting possibilities for other Saturn-system surfaces due to long range transport of E-ring material. Results show that the addition of the IR-transparent salt, KBr, to simulate surface porosity affected silicate spectra in ways that were not predictable from linear mixing models. The strengthening of silicate bands with increasing pore space, even when only trace amounts of KBr were added, indicates that spectral features of porous surfaces are more detectable in the mid-IR. Combining iron oxide with the pure silicates seemed to flatten most of the silicate features, but strengthened the reststrahlen band of the silica. Incorporating carbon with the silicates weakened all silicate features, but the silica bands were more resistant to being diminished, indicating silica may be more detectable in the mid-IR than the serpentines. We show how incorporating darkening agents and porosity provides a more complete explanation of the mid-IR spectral features previously reported on worlds such as Iapetus

Suspension bridge response due to extreme vehicle loads

Journal ArticleThis is an Accepted Manuscript of an article published online by Taylor & Francis Group in Structure and Infrastructure Engineering on 5th March 2003, available online: http://www.tandfonline.com/10.1080/15732479.2013.767844A 269 tonne trailer travelled across the Tamar Suspension Bridge in October 2010, and the authors monitored the response of the structure to the load. The following investigation documents the deflection of towers and the deck during the vehicle's passage, as well as the change in cable tensions. This was achieved by studying monitored data from the bridge collected by accelerometers and strain gauges attached to the stay cables, as well as two robotic total stations that measured the deflection of the mid-span and the sway of the tower saddle. These results were subsequently compared to the response predicted by a finite element (FE) model of the bridge, indicating an accurate match. The FE model was also used to simulate the variation of the dynamic response of the structure, which suggests that the natural frequencies vary depending on the vehicle's location to each mode shape's anti-nodes. © 2013 © 2013 Taylor & Francis

Bedrock Geology of the Upper Iowa River Watershed Phase 4: Dorchester (Iowa) 7.5\u27 Quadrangle,

https://ir.uiowa.edu/igs_ofm/1058/thumbnail.jp