Implementation of a Long-Term Bridge Weigh-In-Motion System for a Steel Girder Bridge in the Interstate Highway System

This technical paper discusses the implementation of a long-term bridge weigh-in-motion system for use in determining gross vehicle weights of trucks crossing steel girder bridges. The system uses strain data to determine truck weights using an existing structural health monitoring system installed on a interstate highway bridge. The applied system has the advantage of not using any axle detectors in the roadway; and instead all analyses are performed using strain gauges attached directly to the steel girders, providing for a long-term monitoring system with minimal maintenance. Long-term data has been used to demonstrate that this method can be readily applied to gain important information on the quantity and weights of the trucks crossing the highway bridge.     

Seismic Retrofit of State Street Bridge on Interstate 80

The State Street Bridge, in Salt Lake City, was designed and built in 1965 according to the 1961 AASHO specifications; the design did not include earthquake-induced forces or displacements since only wind loads were considered. The bridge consists of four reinforced concrete (RC) bents supporting composite welded steel girders; the bents are supported on cast-in-place concrete piles and pile caps. A vulnerability analysis of the bridge was conducted that determined deficiencies in (1) confinement of column lap splice regions, (2) anchorage of longitudinal column bars in the bent cap, (3) confinement of column plastic hinge zones, and (4) shear capacity of columns and bent cap–column joints. Seismic retrofit designs using carbon-fiber-reinforced-polymer (CFRP) composites and steel jackets were performed and compared for three design spectra, including the 10% probability of exceedance in 250 years earthquake. The CFRP composite design was selected for implementation and application of the composite was carried out in the summer of 2000 and 2001, while the bridge was in service. The paper describes the CFRP composite design, which, in addition to column jackets, implemented an “ankle wrap” for improving joint shear strength and a “U-strap” for improving anchorage of column bars in the bent cap; other retrofit measures were implemented, such as bumper brackets and a deck slab retrofit. A capacity versus demand evaluation of the as-built and retrofitted bents is presented.     

Long-Term Durability of State Street Bridge on Interstate 80

Destructive and nondestructive techniques were employed to evaluate the long-term durability of the carbon fiber reinforced polymer (CFRP) composite and externally CFRP-reinforced concrete of the State Street Bridge. Nondestructive evaluation was conducted through strain gauges, tiltmeters, thermocouples, and humidity sensors installed on the bridge bents for real-time health monitoring. Destructive tests were performed to determine the ultimate tensile strength, hoop strength, concrete confinement enhancement, and bond-to-concrete capacity of the CFRP composite for 3 years of exposure. Thermographic imaging was used for detection of voids between CFRP composite and concrete. Although environmental conditions were found to have an effect on the durability of the CFRP composite and CFRP-reinforced concrete substrate, no evidence of steel reinforcement corrosion was observed, and the CFRP composite retrofit is still effective after 3 years.     

Oil and Grease Measurement in Highway Runoff—Sampling Time and Event Mean Concentrations

An event mean concentration (EMC), usually collected with an automatic, flow-weighted composite sampler, is often used to characterize stormwater pollutants. Automatic samplers are not recommended for collecting oil and grease (O&G) samples due to possible biases associated with interactions with tubing and pumps. To measure the EMC without sampler interferences, a series of grab samples (often over ten samples) must be collected along with the flow measurement to compute the EMC. This paper examines 22 O&G pollutographs from small, impervious highway sites, to determine when a single O&G grab sample most closely approximates a flow-weighted composite sample. Samples collected within the first hour of a storm event overestimated the O&G EMC by 20?mg/L or more, while samples collected toward the end of the event underestimated the EMC. The best time to collect a single grab sample ranged from 1 to 6 h after the beginning of runoff, and was related to site or storm-specific factors. Results obtained from this study also showed that strong correlations (R2 = 0.9) exist between O&G and other organic constituents, such as chemical oxygen demand (COD) and dissolved organic carbon (DOC). Correlations also exist between O&G EMC, antecedent dry days, and total rainfall. Depending upon site and regulatory specific factors, using COD or DOC EMCs in lieu O&G samples may be a better strategy.     

Effects of a Permeable Friction Course on Highway Runoff

This project documents the impact of a porous asphalt overlay on the quality and quantity of highway storm-water runoff. A permeable friction course, also known as open graded friction course, is a layer of porous asphalt approximately 50?mm thick, which is often applied on top of conventional asphalt or concrete highways to enhance safety and reduce noise. Storm-water runoff from a four-lane divided highway in the Austin, Texas area was monitored at two sites before and after the installation of a PFC. Observed concentrations of total suspended solids and pollutants associated with particulate material were much lower in the runoff from the PFC than that derived from the conventional asphalt surface. Concentration reductions were observed for total suspended solids, total lead, total copper, and total zinc at both monitoring locations. In addition to the above-mentioned constituents, concentrations of chemical oxygen demand and total Kjeldahl nitrogen were also lower in the runoff from the PFC at a site collecting paired samples from both pavement types. Concentrations of dissolved constituents were not significantly different and concentrations of polycyclic aromatic hydrocarbons were below the detection limit for both pavement types. The runoff coefficient for the PFC appears to be higher than for conventional pavements.     

Thermal Effects on Skewed Steel Highway Bridges and Bearing Orientation

An investigation is conducted to characterize and quantify external effects in composite steel highway bridges under thermal loading. Based on the results of a literature review, including thermal and thermoelastic analyses as well as current design code provisions, a simple but realistic thermal loading is developed for winter and summer conditions for AASHTO load and resistance factor design (LRFD) Zone 3. Three cases of bearing orientation, representative of current design practice, are examined. Parametric studies are then conducted. Hypothetical bridges are designed for a range of different span lengths, section depths, widths, and skews. Each bridge model is tested under all three constraint cases and both winter and summer thermal loading. Variations in structural response with each parameter are plotted, and the relative influence of each parameter is discussed. Design equations to predict the observed displacements and restraint forces at the bearings are then developed by a systematic regression procedure. The applicability of these proposed design equations is demonstrated by examples.     

Detailed Forensic Investigation and Rehabilitation Recommendation on Interstate Highway-30

The main objective of this study is to identify the cause of the punchouts observed on Interstate Highway 30 (IH-30), and to identify possible rehabilitation alternatives. Several nondestructive tests, as well as coring and trenching, were conducted in both distressed and nondistressed areas. Middepth horizontal cracks were found during routine repair and by the trenching performed in this study. It is believed that due to temperature variation at an early stage, horizontal cracks developed at the middepth interface between the steel and concrete. The truck traffic caused the horizontal cracks to deteriorate further. Repetitive truck traffic and thermal loading forced the concrete to crack vertically from the middepth where there were horizontal cracks. The closely spaced transverse and longitudinal cracks, along with the delamination, caused punchouts. Although the problem is not imminent, an immediate seal plus a 75 mm heavy-duty stone matrix asphalt (SMA) overlay will probably provide the most cost-effective remedy for this section of IH-30. Existing distressed areas should be repaired before the rehabilitation. To slow the deterioration, the district should use a latex modified chip seal or asphalt rubber seal (AC15-5TR) followed by a 75 mm heavy duty SMA. This is to provide bonding between the concrete and SMA overlay. If the district chooses to do nothing at this time, it will become costly in 2–3 years if current environmental and traffic conditions hold. The cost to repair a severely deteriorated continuously reinforced concrete pavement (CRCP) would be several times more than the 75 mm heavy duty SMA overlay.     

Case Study of Urban Concrete Pavement Reconstruction on Interstate 10

Many urban concrete pavements in California need to be reconstructed, as they have exceeded their design lives and require frequent maintenance and repair. Information is needed to determine which methodologies for pavement design, materials selection, traffic management, and reconstruction strategies are most suitable to achieve the objectives of California Department of Transportation’s (Caltrans) long-life pavement rehabilitation strategies (LLPRS) program. To develop construction productivity information for several construction windows, a case study was performed on a Caltrans concrete rehabilitation demonstration project near Los Angeles on Interstate-10, where 20 lane-km was successfully rebuilt using fast setting hydraulic cement concrete (FSHCC) with one weekend closure for 2.8 lane-km and repeated 7- and 10-h nighttime closures for the remaining distance. The concrete delivery and discharge controlled the overall progress. In terms of the number of slabs replaced per hour, the 55-h weekend closure was 54% faster than the average nighttime closure. An excellent traffic management strategy helped to reduce the volume of traffic during the weekend closure and minimize the traffic delay through the construction zone.     

Effects of Nonnormal Distributions on Highway Construction Acceptance Pay Factor Calculation

Percent within limits (PWL) is a commonly used quality control/quality assurance measure of highway pavement materials and construction, and it is a popular index for adjusting pay factors. However, PWL is based on the assumption of normal distribution of quality characteristics (e.g., concrete compressive strength and asphalt air voids). Skewness and kurtosis, which are common forms of statistical nonnormal distributions, can potentially bias the acceptance pay factor calculations. To examine this potential pay bias, simulations were performed to investigate the magnitude and the direction (overestimation or underestimation) of pay factor calculations. The study revealed that for both one-sided and two-sided specification limits, bias in pay factors not only did vary in magnitude but also reversed in direction over various ranges of PWL. These analyses showed that for a one-sided upper specification limit, on average, a positive skewness and kurtosis can underestimate the pay factor of an acceptable quality level population by 0.90%, and overestimates a rejectable quality level population by 3.8%. This leads to falsely penalizing acceptable products and rewarding bad products. The same was true for two-sided limits, which again varied based upon the percent of defective materials at the tails of the distribution. This is a very important issue because these biases in pay factors can easily upset the relative profit margins of the contractor. Furthermore, this may not be easily detectable without a detailed and sophisticated analysis as outlined in this paper. For multiple quality characteristics based pay factors, analyses showed that the combined magnitude of these biases was not linearly cumulative. Findings of the study indicate that bias in pay was higher for lots with fewer sublots and higher skewness and kurtosis.     

Predictions of Resuspension of Highway Detention Pond Deposits in Interrain Event Periods due to Wind-Induced Currents and Waves

The paper presents a numerical study of resuspension of deposits from highway detention ponds based on a previous experimental study. The resuspension process is evaluated in dry weather periods with baseflow/infiltration flow through the ponds only. The resuspension is caused by the bed-shear stress induced by the return flow near the bed and waves both generated by the wind. Wind statistics for 30 years have been applied for prediction of the annual discharged bulk of suspended solids and associated pollutants; fluoranthene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene, dibenzo(a,h)anthracene and indeno(1,2,3-cd)pyrene (PAHs) and the heavy metals of cadmium, chromium, copper, lead, nickel, and zinc. The current and wave-generated bed-shear stresses entail a discharged bulk of pollutants corresponding to approximately 10% of the annual accumulation of pollutants in the present pond due to the baseflow in the pond. The mean outlet concentration of suspended solids is well correlated with the wind speed. To reduce the resuspension of deposited materials, two mechanisms are prevailing; either by increase of the water depth of the pond to minimize the effect of the wind in the near-bed region or by reduction of the wind to some degree. The most efficient action for reducing the wind impact on the shallow waters is the establishment of shelterbelts as known from the agriculture. Just a 20% reduction of the yearly wind speeds will reduce the outlet mass with 70% and a 50% reduction with almost 100%. A 50% reduction of the wind speed is far from impossible to achieve with relatively small investments.     

农村公路交通对水稻生理特性的影响

[目的]研究农村公路交通对水稻(Oryza sativa L.)生理特性的影响.[方法]通过在公路边不同距离进行盆栽试验,测定水稻叶片的净光合速率(Pn)、气孔导度(Gs)、胞间CO2浓度(Ci)、蒸腾速率(Ti)、叶片细胞质膜透性、游离脯氨酸和可溶性糖含量.[结果]农村公路交通对至路肩距离为10、50 m处水稻都有不同程度的影响,但至路肩距离150 m处污染相对较少.至路肩不同距离水稻的Pn、Gs、Tr和可溶性糖含量为150 m>10m>50 m,叶片细胞质膜透性为50 m>10m>150 m,而Ci和游离脯氨酸含量随距离增大而变小.[结论]该研究可为提高水稻产量和品质及制定农作物生产区规划提供科学依据.     

Experimental Evaluation of Dynamic Effects for a Selected Highway Bridge

The paper presents an experimental study of the actual dynamic effects for a preselected typical highway bridge. Knowledge of the dynamic impact factors is important for accurate determination of the ultimate load capacity and performance assessment of constructed bridges. Static and dynamic field tests were performed on a two-lane concrete highway bridge built in 1999 on U.S. 90 in northwest Florida. During the tests, one or two fully loaded trucks crossed over the bridge, which was instrumented with strain gauges, accelerometers, and displacement transducers. A wooden plank was placed across the lanes for some runs to trigger extensive dynamic vibration and to simulate poor road surface conditions. Data collected from the tests were used for comprehensive assessment of the bridge under dynamic loading. Impact factors obtained from the tests with higher speeds were found larger than corresponding values recommended by bridge codes. Analysis revealed that stiff vehicle suspension, road surface imperfection, and “bouncing” of the truck loading contributed to the high impact factors. Experimental data were also used for validation of the finite-element models developed for the vehicle–bridge system.     

聊城市一次雨雪天气分析

使用常规的高空、地面资料以及非常规的卫星云图、闪电定位仪资料,对2010年2月28日雨雪天气过程进行了分析,揭示这种雨雪、霰、雷电多种天气现象并存的天气发生、发展的物理机制.结果表明,南方气旋和西风槽相结合,容易在山东省形成较大降水;700 hPa西南急流为降水的产生提供了充沛的水汽条件;降水多发生在垂直速度的上升区和大值区;低层辐合、高层辐散的抽吸机制,有利于形成较大的降水;闪电活动越频繁越容易出现强对流天气,正闪的出现是强对流结束的一个重要标志.     

本溪地区一次大到暴雪天气过程分析

[目的]探讨本溪地区一次大到暴雪天气过程的形成和发展.[方法]利用常规资料,从天气形势演变、物理量场特点着手,对2009年12月4-5日本溪地区一次大到暴雪天气过程的形成和发展进行了分析.[结果]此次大雪到暴雪天气过程是由高空槽和华北气旋共同影响产生.此次过程中,本溪地区上空高层辐散、低层辐合,低层暖、高层冷;低层西南急流将渤海水汽向本溪所处的辽东地区输送,为降雪提供了很好的水汽条件,但由于上升动力不足,过程雪量未达到暴雪.乌拉尔山高脊的发展在这次降雪过程中起了重要作用,高脊加强北抬时有利于冷空气的南下和高空槽的加深.物理量场的分析对此次过程的起止时间和强度预报起了很好的参考作用.[结论]该研究为以后此类天气的预报提供一些依据.     

Indirect Learning of Event Sequences: The Effects of Divided Attention and Stimulus Continuity.

In a serial reaction time (SRT) task, the learning curve is steeper when the stimuli are presented in a repeating sequential manner rather than in random order (Nissen & Bullemer, 1987). This is true even when subjects report being unaware of the presence of the repeating sequence. The present study examines the nature of this learning under conditions designed to reduce attentional resources and to disrupt the continuity of stimuli. In the first three experiments, subjects were trained in the SRT task, with or without the addition of a secondary tone counting task, and with repeating or non-repeating sequences. The results suggest that some sequence learning occurred despite the presence of a secondary task. Experiment 4 examined the extent of sequence learning when the inter-stimulus interval was varied between trials. The overall results suggest that despite reduced attentional allocation and discontinuous stimulus presentation, some sequence learning occurs. This result supports other work suggesting a dissociation between learning when measured explicitly, and when assessed through performance indicators. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Impact of Posted Load Limits on Highway Bridge Reliability

The effectiveness of posted load limits in reducing annual maximum live load effects, thus enhancing bridge reliability, is investigated for 12 and 40 m simple span highway bridges. Novel analytical expressions are derived for event gross vehicle weight (GVW) distributions that account for violation of posted load restrictions, and the corresponding annual maximum GVW distributions are presented. Annual reliability indices associated with load restrictions computed using typical bridge posting criteria and different compliance levels are compared to the target reliability index. For the case of perfect compliance, a posted load restriction can significantly reduce maximum annual live load effects and so enhance the reliability. Under imperfect compliance, however, a violation rate as low as 2.5% (i.e., one illegal truck in 40 ignores the posting) causes the mean value and variability of the annual maximum live load effect distribution to increase significantly, resulting in a significant loss in reliability. Thus, unless posted loads are strictly enforced, the effectiveness of enhancing existing bridge reliability with a posted load restriction is questionable.     

Seismic Effect on Highway Bridges in Chi Chi Earthquake

This paper reports the bridge damage in the Chi Chi earthquake. Damage to bridge structures may occur in the superstructure, the substructure, or the approaches. Typical types of damage are discussed and illustrated in this paper. A review of the design specifications in Taiwan is also presented to give the background on the seismic design of highway bridges in Taiwan.     

高速公路汽车自动测速模块FPGA的设计

文章提出了一种基于现场可编程门阵列(FPGA)的速度检测器的硬件实现,并将其应用于车道测速系统中.在实验中表明,测速器的运行频率可达到200兆以上,这样的运行频率可以使系统的反应更加灵敏、快捷,而且测出的速度也更加准确.在传输中,还可以利用基于现场可缩程门阵列(FPGA)的优势,在FPGA里面生成所需要的接口,而无需再增加其他器件,使得成本大大的降低.如对测速器进行一定的修改,其通用性会更加完善,可以应用于更多的领域中.     

Impact of Rainfall on the Productivity of Highway Construction

Heavy rainfall often leads to complete suspension of highway construction due to saturated and unworkable soil conditions. Therefore, quantifying the impact of rainfall on the productivity of highway construction is essential in preparing realistic schedules and cost estimates for the preconstruction stage and in analyzing weather-related claims for the postconstruction stage. This paper presents a decision support system for quantifying the impact of rainfall on productivity and duration of common highway construction operations, namely: earthmoving, construction of base courses, construction of drainage layers, and paving operations. The system incorporates a knowledgebase and a database. The knowledgebase includes if∕then type rules, acquired from experts in highway construction operations, and the database contains hourly records of weather parameters from the closest weather station to the construction site. The system, named WEATHER, is a software system that provides user-friendly interface, including menus, dialog boxes, and graphical capabilities to facilitate data input and output.     

江淮流域一次急流暴雪的成因分析

采用NCEP/NCAR再分析资料和常规天气学资料,对2008年1月27～28日江淮流域出现的急流暴雪过程进行分析.结果表明,低空西南急流是影响大暴雪的主要系统,急流的加强北抬导致江淮流域动力辐合和水汽辐合的加大,有利于降雪强度的加大.降雪强度的增加与低空急流出口处正涡度的增长关系密切,高空正涡度厚度的增加对暴雪增幅期的预报有一定的指示意义,高空抽吸作用也是降雪加强的动力学机制.高低空垂直螺旋度绝对值高值区和低空水汽通量高值区的叠加区域与暴雪落区关系密切.