The reuse potential of tire chips as coarse aggregates in pavement concrete was examined in this research by investigating the effects of low- and high-volume tire chips on fresh and hardened concrete properties. One concrete control mixture was designed, which well exceeds CDOT Class P concrete requirements. The coarse aggregate component of the mixture was replaced in 100%, 50%, 30%, 20%, and 10% by volume using tire chips. The fresh concrete properties, compressive strength, flexural strength, splitting strength, permeability, and freeze/thaw durability were tested in the lab to evaluate the potential of including tire chips in concrete paving mixes. The testing results indicate tire chips can be used to replace coarse aggregate in concrete pavement mixtures. Two mixtures with 10% coarse aggregate replaced by tire chips had the best performance. The workability was comparable to the control mixture, and the air content reached 6%. At 28 days of age, the average compressive strength of the two mixtures was significantly less than the control but still exceeded CDOTs specification of 4200 psi; the averaged flexural and splitting tensile strengths were higher than 900 psi and 590 psi respectively. In addition, the two mixtures exhibited moderate resistance to chloride-ion penetration at 28 days of age and high freeze/thaw durability. The rubberized mixtures investigated in this study sustained a much higher deformation than the control mixture when subjected to compressive, flexural, and splitting loadings.

关键词：金属芯片；回收材料；比较分析

查看摘要 索取原文[47页]

In this study, we have conducted modeling of the energy demands and supply systems of an actual small-scale housing complex and evaluated the effect of CGS installation from the standpoint of environmental and the economic aspects. Then, we have developed a new CGS operational algorithm that controlled the CGS generator by following the temperature of the heat storage medium in the storage tank and we have demonstrated the advantageous effects of this method. In addition, we have discussed the appropriate heat storage tank capacity for the proposed method.

关键词：能源管理系统；热电联产系统；设施规划

查看摘要 索取原文[6页]

In this research, twenty batches of concrete with six different mixture proportions were tested with VERIFI to evaluate 1) accuracy and repeatability of VERIFI measurements, 2) ability of VERIFI to adjust slump automatically with water and admixture, and 3) effects on concrete properties when water and admixture are added continuously during transit instead of adding whole at the plant or jobsite. For each batch, concrete was sampled every 30 minutes up to 90 minutes and tested for slump, temperature, air content, unit weight, water content, bleeding (select batches), and rheology (select batches). Cylindrical concrete specimens were cast at 90 minutes and were tested for compressive strength at 3 and 28 d (or 3 and 14 d for IDOT mixes).

关键词：土木工程；混凝土；混凝土行业；建筑

查看摘要 索取原文[54页]

The paper is focused on issues related to the behavior of reinforced soil walls at working stress and near failure, and the prediction accuracy of internal stability working stress and limit equilibrium (LE) design methods. The paper identifies the key variables, principles and assumptions that affect the accuracy of these methods considering the full range of conditions from working stress to failure. The strain at peak strength of a granular soil wall backfill is identified as a key parameter for understanding the differences between working stress and LE design methods. Both geosynthetic and steel reinforced wall systems are examined using measured reinforcement strain and loads taken from full-scale walls under both working stress (operational) conditions and at incipient collapse (failure).

关键词：工作压力；加筋土墙；钢铁

查看摘要 索取原文[15页]

Structural Health Monitoring has great potential to provide valuable information about the actual structural condition and can help optimize the management activities. However, few effective and robust monitoring methods exist which hinders a nationwide use of SHM in structural condition evaluations. The objective of this project was to research and develop methods for structural identification and damage detection based on strain monitoring using long-gauge fiber-optic sensors. In particular two universal parameters of beam-like structures were studied in detail: the neutral axis and deformed shape. Data from two structures were used for validation purposes: from on-site monitoring of the US202/NJ23 overpass and from lab testing of a scale-model of a similar structure. The conclusions are that while the neutral axis varies during dynamic events, it changes the location due to damage, and it can be located accurately using a probabilistic approach. Thus, it can be used as a damage sensitive feature. At least two sensors per cross-section are necessary for an accurate evaluation of the location of the neutral axis. The vertical displacement of beams can be calculated by double integration of the curvature. However, the double integration method affects the accuracy of the evaluation, and to achieve the most accurate result a linear combination of integration methods is recommended. At least three locations along each girder should be instrumented with two parallel sensors for accurate evaluation of the vertical displacement. The methodologies researched in this project are presented in this report and recommendations for the use of the methods provided.

关键词：复合材料；纤维光学；钢筋混凝土；钢铁

查看摘要 索取原文[20页]

The 2007 edition of AASHTO LRFD Bridge Design Specifications contains prescriptive requirements for the quantity and placement of confinement reinforcement located in the bottom bulb of pretensioned concrete Ⅰ-girders. The proposed model can be used to design confinement reinforcement as an alternative to AASHTO's prescriptive requirements. The model considers a range of Ⅰ-girder conditions and variations, yet is intended to be practical enough for use by bridge design engineers. Variables in the design model include flange and bearing geometry, strand size and placement, effective prestress force, concrete and steel material properties, and the effects of steel bearing plates. The model is based on strut-and-tie and shear-friction concepts and considers the lateral-splitting failure mode. Derivation of the model is presented, and the model is compared with experimental results from the published literature.

关键词：桥梁设计；钢铁；混凝土

查看摘要 索取原文[9页]

Chloride ion ingress is an important parameter that helps estimate the durability and service life of reinforced concrete (RC) and prestress concrete (PC) structures, especially in those structures exposed to marine environments and salts applied during the winter season for traffic safety. Current techniques used to detect chloride content and monitor the level of corrosion in RC and PC structures, such as acoustic emission (AE), fiber optics, and electrochemical measurements, are time consuming, and invasive. In addition, they require external power sources, complex test setups, are expensive to implement, and often, it is difficult to interpret the data recorded in the field. In an effort to overcome these restrictions, an inexpensive, wireless corrosion detector sensor based on commercial radio frequency identification (RFID) technology that does not need to be powered by a local source of energy, has been developed by an Oklahoma State Universitys research team. The purpose of the first phase of this project was to implement this innovative RFID corrosion sensor into a new bridge construction to collect data during monitoring to study both the reliability and field performance of the sensor in-situ and under laboratory conditions. The laboratory work attempted to correlate the sensors sensitivity to the level of corrosion in the structure. Phase II of this work will be focused on the long-term monitoring of the sensors installed in the field for a period of approximately 10 years.

关键词：外加剂；氯化物；混凝土路面；钢铁

查看摘要 索取原文[31页]

Accurate estimates of bearing stiffnesses are often necessary for bridge design and construction calculations. In the case of steel-reinforced elastomeric bearing pads, the compression stiffness or roll stiffness is sometimes difficult to estimate because of complex deformations of the elastomer. A method of numerical analysis for estimating the axial and roll stiffnesses of bearing pads is presented. To validate the axial calculation method, experimental compression tests were performed on pad specimens constructed in accordance with Florida design standards. A method for calculating roll stiffness is also presented in which the pad is modeled as a grillage of compression-only axial springs. The grillage method was partially derived from roll stiffness data measured in a separate experimental study. The grillage method was demonstrated to accurately capture both the nonlinear moment-rotation behavior caused by liftoff of the girder from the pad and the observed sensitivity of roll stiffness to initial compressive loading caused by self-weight of the girder. Reductions in roll stiffness that are caused by girder slope relative to the pad were also examined.

关键词：轴承刚度；精确估计；钢铁

查看摘要 索取原文[11页]

The French five-point bending (5PB) test provides a laboratory-scale test that allows studying the fatigue resistance of surfacing systems on orthotropic steel deck (OSD) bridges. The surfacing structure for OSD bridges in the Netherlands is mostly a multilayer system: top porous asphalt (PA) layer, guss asphalt (GA) layer, steel deck, and two membrane layers. In this paper, an analytical solution for the 5PB test setup is presented first. To understand better the influence of geometrical, mechanical, and structural parameters on the performance of the typical multilayer surfacing system of OSD bridges in the Netherlands, the 5PB test specimens with five structural layers have been investigated. The parametric study was performed at the numerical platform CAPA-3D, which was developed at the Section of Structural Mechanics of the Delft University of Technology. The thicknesses of the top PA layer, middle GA layer, and the steel plate were varied. The influences of the mechanical properties of both top and bottom membrane layers were studied. The sensitivities of those influence factors were evaluated by examination of the maximum tensile stress at the top surface of the PA layers and the strain distributions through the entire thickness of the specimen at two cross sections.

关键词：五点弯曲；钢铁；抗疲劳性

查看摘要 索取原文[8页]

A data base of 84 pile load tests was developed for steel pipe piles, driven in clay (small amounts of sand near the surface for a few tests), where there was sufficient data to estimate effective overburden pressures with reasonable accuracy, where soil strengths were well defined, and where a load-settlement curve was available for the load test. Measured pile capacities were compared with values predicted using five methods that have been, are being, or potentially may be used in engineering practice. The two lambda methods had the least scatter but tended to overpredict capacities by about 20%. The current API method had slightly more scatter but overpredicted capacities by only about 13% on the average. The two alpha methods had the largest scatter and the greatest differences between measured and predicted capacities.

关键词：荷载试验；钢铁；负载沉降曲线

查看摘要 索取原文[19页]