Robustness of steel truss bridges: laboratory testing of a full-scale 21-metre bridge span

[EN] This study aimed to experimentally analyse the robustness of riveted steel bridges based on truss-type structures and to define practical recommendations for early detection of local failures before they cause progressive structural collapse. Although there are many experimental studies on robustness and progressive collapse on buildings, those on bridges are either theoretical or deal with actual collapses. This paper describes a unique case of a 21m full-scale bridge span tested under laboratory conditions with an extensive monitoring system, together with an experimental study to evaluate structural behaviour and robustness as damage or failure progressed in its elements. A linear-static finite-element analysis was also included to examine other possible causes not included in the experiment. The results proved the structural redundancy of this type of truss structure based on the joints¿ resistance to bending moments and gave rise to a series of practical structural health recommendations to identify early failures and avoid progressive or sudden bridge collapse. The study carried out and the recommendations it produced are now being applied in three similar bridge case studies.We would like to express our gratitude to the FGV (Ferrocarrils de la Generalitat Valenciana) and FCC Construcción S.A., CHM Obras e Infraestructuras S.A., Contratas y Ventas S.A. and CALSENS S.L. for giving us the opportunity to test a bridge at the ICITECH facilities, also to Juan Antonio García Cerezo, of FGV, for his invaluable cooperation and recommendations. We also wish to show our gratitude for the magnificent work on the bridge by Jesús Martínez, Eduardo Luengo and Daniel Tasquer. The tests on the bridge meant that much of the Structures Laboratory was out of service for other work, for which we owe a debt of gratitude to our ICITECH colleagues for their infinite patience and understanding.Buitrago, M.; Bertolesi, E.; Calderón García, PA.; Adam, JM. (2021). Robustness of steel truss bridges: laboratory testing of a full-scale 21-metre bridge span. Structures. 29:691-700. https://doi.org/10.1016/j.istruc.2020.12.005S69170029Ghali, A., & Tadros, G. (1997). Bridge Progressive Collapse Vulnerability. Journal of Structural Engineering, 123(2), 227-231. doi:10.1061/(asce)0733-9445(1997)123:2(227)Cha, E. J., & Ellingwood, B. R. (2012). Risk-averse decision-making for civil infrastructure exposed to low-probability, high-consequence events. Reliability Engineering & System Safety, 104, 27-35. doi:10.1016/j.ress.2012.04.002Zhuang, M., & Miao, C. (2020). RETRACTED: Fatigue reliability assessment for hangers of a special-shaped CFST arch bridge. 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J Acquir Immune Defic Syndr

BackgroundCervical cancer is a major public health problem in resource-limited settings, particularly among HIV-infected women. Given the challenges of cytology-based approaches, the efficiency of new screening programs need to be assessed.SettingCommunity and hospital-based clinics in Gaborone, Botswana.ObjectiveTo determine the feasibility, and efficiency of the \u201cSee and Treat\u201d approach using Visual Inspection Acetic Acid (VIA) and Enhanced Digital Imaging (EDI) for cervical cancer prevention in HIV-infected women.MethodsA two-tier community-based cervical cancer prevention program was implemented. HIV-infected women were screened by nurses at the community using the VIA/EDI approach. Low-grade lesions were treated with cryotherapy on the same visit.ResultsFrom March 2009 through January 2011, 2,175 patients were screened for cervical cancer at our community-based clinic. 253 (11.6%) were found to have low-grade lesions and received same-day cryotherapy. 1,347 (61.9%) women were considered to have a normal examination and 575 (27.3%) were referred for further evaluation and treatment. Of the 1,347 women initially considered to have normal exams, 267 (19.8%) were recalled based on weekly quality control assessments. 210 (78.6%) of the 267 recalled women and 499 (86.8%) of the 575 referred women were seen at the referral clinic. Of these 709 women, 506 (71.4%) required additional treatment. Overall, 264 CIN stage 2 or 3 were identified and treated, and six micro-invasive cancers identified were referred for further management.ConclusionsOur \u201cSee and Treat\u201d cervical cancer prevention program using the VIA/EDI approach is a feasible, high-output and high-efficiency program, worthy of considering as an additional cervical cancer screening method in Botswana, especially for women with limited access to the current cytology-based screening services.20122014-01-08T00:00:00ZP30 AI045008/AI/NIAID NIH HHS/United StatesU2G PS001949/PS/NCHHSTP CDC HHS/United States1U2GPS001949/PHS HHS/United StatesIP30 AI 45008/AI/NIAID NIH HHS/United States22134146PMC388408

Measurements of absolute hadronic branching fractions of Λc+\Lambda_{c}^{+} baryon

Using $567\rm{pb}^{-1}$ of $e^+e^-$ collisions recorded at $\sqrt{s}=4.599\rm{GeV}$ with the BESIII detector, we report first measurements of absolute hadronic branching fractions of Cabibbo-favored decays of the $\Lambda_{c}^{+}$ baryon with a double-tag technique. A global least-square fitter is utilized to improve the measured precision. Among the measurements for twelve $\Lambda_{c}^{+}$ decay modes, the branching fraction for $\Lambda_{c}^{+} \rightarrow pK^-\pi^+$ is determined to be $(5.84\pm0.27\pm0.23)\%$, where the first uncertainty is statistical and the second is systematic. In addition, the measurements of the branching fractions of the other eleven Cabbibo-favored hadronic decay modes are significantly improved

Measurement of azimuthal asymmetries in inclusive charged dipion production in e+e−e^+e^- annihilations at s\sqrt{s} = 3.65 GeV

We present a measurement of the azimuthal asymmetries of two charged pions in the inclusive process $e^+e^-\rightarrow \pi\pi X$ based on a data set of 62 $\rm{pb}^{-1}$ at the center-of-mass energy $\sqrt{s}=3.65$ GeV collected with the BESIII detector. These asymmetries can be attributed to the Collins fragmentation function. We observe a nonzero asymmetry, which increases with increasing pion momentum. As our energy scale is close to that of the existing semi-inclusive deep inelastic scattering experimental data, the measured asymmetries are important inputs for the global analysis of extracting the quark transversity distribution inside the nucleon and are valuable to explore the energy evolution of the spin-dependent fragmentation function.Comment: 7 pages, 5 figure

Observation of e+e−→ωχc1,2e^+e^- \rightarrow \omega \chi_{c1,2} near s\sqrt{s} = 4.42 and 4.6 GeV

Based on data samples collected with the BESIII detector operating at the BEPCII storage ring at center-of-mass energies $\sqrt{s} >$ 4.4 GeV, the processes $e^+e^- \rightarrow \omega \chi_{c1,2}$ are observed for the first time. With an integrated luminosity of $1074 pb^{-1}$ near $\sqrt{s} =$ 4.42 GeV, a significant $\omega \chi_{c2}$ signal is found, and the cross section is measured to be (20.9 \pm 3.2 \pm 2.5)\pb. With $567 pb^{-1}$ near $\sqrt{s} =$ 4.6 GeV, a clear $\omega \chi_{c1}$ signal is seen, and the cross section is measured to be (9.5 \pm 2.1 \pm 1.3) \pb, while evidence is found for an $\omega \chi_{c2}$ signal. The first errors are statistical and the second are systematic. Due to low luminosity or low cross section at other energies, no significant signals are observed. In the $\omega \chi_{c2}$ cross section, an enhancement is seen around $\sqrt{s} =$ 4.42 GeV. Fitting the cross section with a coherent sum of the $\psi(4415)$ Breit-Wigner function and a phase space term, the branching fraction $\mathcal{B}(\psi(4415)\to\omega\chi_{c2})$ is obtained to be of the order of $10^{-3}$.Comment: 7 pages, 3 figure

Measurement of the e+e−→π+π−\mathrm e^+\mathrm e^-\rightarrow\mathrm\pi^+\mathrm\pi^- Cross Section between 600 and 900 MeV Using Initial State Radiation

We extract the $e^+e^-\rightarrow \pi^+\pi^-$ cross section in the energy range between 600 and 900 MeV, exploiting the method of initial state radiation. A data set with an integrated luminosity of 2.93 fb$^{-1}$ taken at a center-of-mass energy of 3.773 GeV with the BESIII detector at the BEPCII collider is used. The cross section is measured with a systematic uncertainty of 0.9%. We extract the pion form factor $|F_\pi|^2$ as well as the contribution of the measured cross section to the leading order hadronic vacuum polarization contribution to $(g-2)_\mu$. We find this value to be $a_\mu^{\pi\pi,\rm LO}(600-900\;\rm MeV) = (368.2 \pm 2.5_{\rm stat} \pm 3.3_{\rm sys})\cdot 10^{-10}$.Comment: 14 pages, 7 figures, accepted by PL

Fabrication of Ce-doped MnO2 decorated graphene sheets for fire safety applications of epoxy composites: flame retardancy, smoke suppression and mechanism

Ce-doped MnO2–graphene hybrid sheets were fabricated by utilizing an electrostatic interaction between Ce-doped MnO2 and graphene sheets. The hybrid material was analyzed by a series of characterization methods. Subsequently, the Ce-doped MnO2–graphene hybrid sheet was introduced into an epoxy resin, and the fire hazard behaviors of the epoxy nanocomposite were investigated. The results from thermogravimetric analysis exhibited that the incorporation of 2.0 wt% of Ce-doped MnO2–graphene sheets clearly improved the thermal stability and char residue of the epoxy matrix. In addition, the addition of Ce–MnO2–graphene hybrid sheets imparted excellent flame retardant properties to an epoxy matrix, as shown by the dramatically reduced peak heat release rate and total heat release value obtained from a cone calorimeter. The results of thermogravimetric analysis/infrared spectrometry, cone calorimetry and steady state tube furnace tests showed that the amount of organic volatiles and toxic CO from epoxy decomposition were significantly suppressed after incorporating Ce–MnO2–graphene sheets, implying that this hybrid material has reduced fire hazards. A plausible flame-retardant mechanism was hypothesized on the basis of the characterization of char residues and direct pyrolysis-mass spectrometry analysis: during the combustion, Ce–MnO2, as a solid acid, results in the formation of pyrolysis products with lower carbon numbers. Graphene sheets play the role of a physical barrier that can absorb the degraded products, thereby extend their contact time with the metal oxides catalyst, and then promote their propagate on the graphene sheets; meanwhile pyrolysis fragments with lower carbon numbers can be easily catalyzed in the presence of Ce–MnO2. The notable reduction in the fire hazards was mainly attributed to the synergistic action between the physical barrier effect of graphene and the catalytic effect of Ce–MnO2

Measurement of the branching fractions of Ds+→η′XD_{s}^{+}\rightarrow \eta'X and Ds+→η′ρ+D_{s}^{+}\rightarrow \eta'\rho^{+} in e+e−→Ds+Ds−e^+e^-\to D^+_{s}D^-_{s}

We study $D_{s}^{+}$ decays to final states involving the $\eta'$ with a 482$\,$pb$^{-1}$ data sample collected at $\sqrt{s}$ = 4.009$\,$GeV with the \mbox{BESIII} detector at the BEPCII collider. We measure the branching fractions $\mathcal{B}(D^+_{s}\rightarrow \eta'X)$ = (8.8$\pm$1.8$\pm$0.5)$\%$ and $\mathcal{B}(D_{s}^{+}\rightarrow \eta'\rho^{+})$ = ($5.8\pm1.4\pm0.4$)$\%$ where the first uncertainty is statistical and the second is systematic. In addition, we estimate an upper limit on the non-resonant branching ratio $\mathcal{B}(D_{s}^{+}\rightarrow \eta'\pi^+\pi^0)<5.1\%$ at the 90$\%$ confidence level. Our results are consistent with CLEO's recent measurements and help to resolve the disagreement between the theoretical prediction and CLEO's previous measurement of $\mathcal{B}(D_{s}^{+}\rightarrow \eta'\rho^{+})$