Reaction Spectrum Comparative Analysis of Seismic Performance of 62 m CFST Bridge with Curved-String Truss before and after Reinforcement

Taking a 62 m CFST bridge with a curved-string truss as the research object, according to its reinforcement scheme, the spatial finite element models of the bridge before and after reinforcement were established by using the general finite element software ANSYS. The natural frequencies of the bridge before and after reinforcement were calculated, and the seismic performance of the bridge was analyzed by using the response spectrum method. The results show that the frequencies of the reinforced bridges increase in varying degrees, especially the vertical and torsional frequencies. Before and after reinforcement, the maximum axial force in the upper chord of the bridge is the largest, and the shear force and bending moment are small. The maximum internal force appears at the two ends of the upper chord. This position should be regarded as the weak link of the bridge seismic resistance. Under the same conditions, the axial force of the bridge after reinforcement is reduced by about 30% compared with that before reinforcement, and the displacement of the bridge after reinforcement is reduced in varying degrees. The reinforcement measures can improve the lateral and vertical stiffness of the bridge, especially the stiffness of the deck system

Comparative analysis of seismic performance of 122-meter long concrete-filled steel tube arched chord truss bridge before and after reinforcement

Finite element analysis of a 122-meter concrete-filled steel tube arched chord truss bridge was performed using ANSYS to obtain the natural vibration characteristics of the bridge, both before and after reinforcement. In addition, the response spectrum and dynamic time history methods were used to analyze and compare its seismic performance. The results show that the transverse stiffness of the bridge’s main truss was relatively low. After the reinforcement, the vertical and the torsional frequencies of the bridge significantly increased by 24% and 32%, respectively. under the same condition, the axial force at the fixed end of the top chord of the strengthened bridge was reduced by roughly 29%, and the transverse and the vertical displacement at the middle of the top chord span were reduced by roughly 10% and 20%, respectively. Thus, the reinforcement measures significantly improved the vertical stiffness of the bridge. For this bridge, the dynamic time history analysis played a more controlling role in the seismic design. Among the three types of seismic waves, the El Centro wave yielded the largest transverse displacement result and hence, should preferably be used to assess the deflections

Summary table of the impact of intervention at various outbreak thresholds that triggered school-based vaccination.

<p>At each threshold level, we defined the “Maximum outbreak size” as the size of the largest outbreaks from 2014 to 2015, based on the simulation median. “Case reduction” was the percentage of varicella cases reduced due to the school-based vaccination strategy. “Reduction in Size of Outbreaks” was the percentage reduction in the size of the maximum outbreak compared with the baseline scenario. “Proportion of effective control” was the proportion of simulation runs that have simulated cases smaller than the reported cases, a proxy measure that the intervention could effectively bring the number of reported cases under control.</p

Summary table of parameters.

<p>Summary table of parameters.</p

A summary table of the adjusted average number of schools, classes, and distribution of students in Shenzhen.

<p>Students per class, <i>N</i>_{<i>j</i>,<i>i</i>}, was given by <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0177514#pone.0177514.e003" target="_blank">Eq (2)</a>). The information was obtained from Shenzhen Education Bureau [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0177514#pone.0177514.ref020" target="_blank">20</a>].</p

Number of weekly varicella confirmations from 2010 to 2015 per 1,000,000 population in Shenzhen from 2013 to 2015.

<p>Weekly population is computed using <i>loess</i> model. School holidays are shaded in yellow.</p

The ABM simulation results of varicella reported cases in Shenzhen from 2013 to 2015.

<p>The simulation median is plotted in red, reported cases are in black dashed line, the fitted transmission rate, <i>β</i>(<i>t</i>), is the blue line at the bottom and the 95% Confidence Interval (C.I.) is in grey. School holidays are shaded in yellow.</p

Table of beta (or <i>β</i>) multiplier (<i>θ</i>) with respect to different age groups.

<p>Table of beta (or <i>β</i>) multiplier (<i>θ</i>) with respect to different age groups.</p

The structural diagram of the ABM-SEIR in Shenzhen.

<p>Within each classes, SEIR model structure is applied (see ODE <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0177514#pone.0177514.e002" target="_blank">System (1)</a>). Within a school, if a class reaches the pre-defined outbreak threshold, there will be possible disease transmission to non-outbreak classes, to which we name “class-class transmission”. This transmission will vanish whenever the number of cases in the outbreak classes becomes lower than the outbreak threshold.</p

Boxplot of the number of varicella school outbreaks from 2010 to 2015, which displays similar patterns as in Fig 2.

<p>The number of school outbreaks per 30 days is displayed, to adjust for the variations of the number of days in each month.</p