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LINE-HAUL TRUCKING COSTS IN RELATION TO VEHICLE GROSS WEIGHTS 线路运输成本与车辆总重的关系
Pub Date : 1962-01-01 DOI: 10.4271/620060
H. Stevens
A REPRESENTATIVE SCHEDULE IS PRESENTED OF VEHICULAR OPERATING COSTS. THE DIFFERENCES BETWEEN WHICH ARE CAUSED ONLY BY CHANGES IN VEHICLULAR GROSS WEIGHT, AND/OR CHANGES IN TYPES OF TRAILER COMBINATIONS. SUCH REPRESENTATIVE VEHICULAR COST DATA LATER CAN BE RELATED TO REPRESENTATIVE COSTS FOR HIGHWAY FACILITIES WITH DIFFERENT LOAD-CARRYING CAPABILITIES. THE REPORT DESCRIBES HOW THE DIFFERENT COST FACTORS WERE ADJUSTED FOR DIFFERENCES IN PRICES PAID FOR FUEL, WAGES, FRINGE BENEFITS, DEPRECIATION AND INTEREST CHARGES, AND NEW VEHICLES. THE DATA ARE PRESENTED IN AN EXTENSIVE SERIES OF CHARTS SHOWING THE VARIATIONS IN VEHICLE-MILE COSTS BY LOADED GROSS WEIGHT FOR ALL THE 23,384 TRAILER COMBINATIONS, ALL THE GASOLINE ENGINE POWERED TRAILER COMBINATIONS AND ALL THE DIESEL POWERED COMBINATIONS USING EITHER GASOLINE OR DIESEL ENGINES. OTHER CHARTS AND TABLES SHOW HOW UNIT COSTS ARE AFFECTED BY BODY TYPE, TYPE OF TERRAIN, AVERAGE DAILY TRAVEL MILEAGE, AVERAGE LOAD SPEED, AND OTHER OPERATING VARIABLES.
提出了车辆运行费用的代表性进度表。两者之间的差异仅由车辆总重的变化和/或拖车组合类型的变化引起。这些具有代表性的车辆成本数据以后可以与具有不同承载能力的公路设施的代表性成本相关联。报告描述了不同的成本因素是如何根据燃油、工资、附加福利、折旧和利息费用以及新车的价格差异进行调整的。数据以一系列广泛的图表形式呈现,显示了所有23,384种拖车组合、所有汽油发动机驱动的拖车组合和所有使用汽油或柴油发动机的柴油动力组合按装载毛重计算的车辆英里成本变化。其他图表和表格显示了单位成本如何受到车身类型、地形类型、平均每日行驶里程、平均负载速度和其他操作变量的影响。
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引用次数: 6
Forced vibration of continuous highway bridges 公路连续桥的强迫振动
Pub Date : 1962-01-01 DOI: 10.31274/RTD-180813-636
D. A. Linger, C. L. Hulsbos
A CORRELATION IS PRESENTED OF FORCED VIBRATION THEORY WITH DYNAMIC IMPACT TESTS FOR THREE CONTINUOUS HIGHWAY BRIDGES AND A SIMPLE SPAN HIGHWAY BRIDGE. THE EXPERIMENTAL IMPACT WAS DETERMINED AT THE CENTERLINE OF THE SINGLE SPAN HIGHWAY BRIDGE AND IN THE OUTER AND INNER SPANS AND AT THE INTERIOR SUPPORTS FOR THE THREE TYPES OF CONTINUOUS FOUR-SPAN HIGHWAY BRIDGES. THE EFFECT OF THE VEHICLE IS ASSUMED TO BE AN OSCILLATING FORCING FUNCTION WHOSE FREQUENCY IS THE FREQUENCY OF AXLE REPETITION AND WHOSE FORCE IS THE OSCILLATING LOAD EFFECT OF A CONSTANT FORCE TRAVERSING A BEAM. THE CORRELATION OF THE THEORETICAL AND EXPERIMENTAL IMPACT INDICATES THAT THE SIMPLIFICATIONS MADE IN THE EFFECT OF THE VEHICLES ARE JUSTIFIED FOR THE BRIDGES TESTED AND THE EXPERIMENTAL VEHICLE VELOCITIES USED. THESE RESULTS SHOW QUALITATIVELY THAT THE AMOUNT OF IMPACT IS A FUNCTION OF THE RATIO OF THE FREQUENCY OF AXLE REPETITION TO THE LOADED NATURAL FREQUENCY OF THE STRUCTURE. /AUTHOR/
提出了强迫振动理论与三座连续桥梁和一座简单跨径公路桥梁动力冲击试验的相关性。对三种类型的连续四跨公路桥在单跨公路桥中心线、内外跨和内支座处的试验冲击进行了测定。假设车辆的作用是一个振荡强迫函数,其频率为轴重复频率,其力为通过梁的恒定力的振荡载荷效应。理论冲击与实验冲击的对比表明,对于所测试的桥梁和所使用的实验车速,车辆影响的简化是合理的。这些结果定性地表明,冲击量是轴重复频率与结构加载固有频率之比的函数。/作者/
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引用次数: 2
EXPERIMENTAL PAVING PROJECTS USING CURTISS-WRIGHT'S COAL- MODIFIED, COAL-TAR BINDER 采用柯蒂斯-赖特的煤改性煤焦油粘结剂的试验性铺装工程
Pub Date : 1962-01-01 DOI: 10.13023/KTC.RR.1962.173
W. B. Drake
THE OBSERVATION AND EVALUATION OF 13 SECTIONS OF EXPERIMENTAL PAVEMENT CONSTRUCTED IN KENTUCKY USING COAL- MODIFIED, COAL-TAR BINDER ARE DISCUSSED. THESE ARE COMPARED WITH THE PERFORMANCE OF CONTROL SECTIONS IN WHICH NORMAL SPECIFICATION ASPHALT CEMENTS WERE USED. THE RESULTS OF LABORATORY AND FIELD TESTS ARE ALSO REPORTED TO SUPPORT AND SUPPLEMENT THE VISUAL SURVEYS. /AUTHOR/
对美国肯塔基州13段使用煤改性煤焦油粘结剂的试验路面进行了观察和评价。这些与使用普通规格沥青水泥的控制段的性能进行了比较。还报告了实验室和实地试验的结果,以支持和补充目测调查。/作者/
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引用次数: 2
A THEORY OF TRAFFIC FLOW FOR EVALUATION OF GEOMETRIC ASPECTS OF HIGHWAYS 公路几何方面评价的交通流理论
Pub Date : 1962-01-01 DOI: 10.5703/1288284313592
M. Harr, G. A. Leonards
AN ANALYTIC APPROACH IS DEVELOPED WHEREBY THE VARIOUS ASPECTS OF A HIGHWAY (SUCH AS CURVES, GRADES, LANE WIDTH, TRAFFIC CONTROL DEVICES, TYPE AND CONDITION OF SURFACING) CAN BE EVALUATED QUANTITATIVELY UNDER VARYING TRAFFIC DENSITY AND WEATHER CONDITIONS PROVIDING A RATIONAL BASIS FOR GEOMETRIC DESIGN. IN THE PRESENT ANALYSIS IT IS POSTULATED THAT TRAFFIC REACTS TO A MOTIVATING PRESSURE POTENTIAL IN A PATTERN THAT DETERMINES THE BEHAVIOR OF ANY PARTICULAR VEHICLE TRAVERSING A GIVEN SECTION OF ROADWAY. THIS CONCEPT CAN BE EXPRESSED QUANTITATIVELY IN A MANNER ANALOGOUS TO THAT USED IN DESCRIBING ONE-DIMENSIONAL VISCOUS FLOW IN A COMPRESSIBLE FLUID. SOLUTION OF THE RESULTING DIFFERENTIAL EQUATION YIELDS A PARAMETER WHICH IS A NUMERICAL MEASURE OF THE SALIENT CHARACTERISTICS OF A ROAD. PROCEDURES ARE THEN PROPOSED TO DETERMINE THIS PARAMETER, USING MEASURABLE VEHICULAR VELOCITIES, WHICH ELIMINATE THE NEED FOR EVALUATING THE MOTIVATING PRESSURE POTENTIAL.
在不同的交通密度和天气条件下,高速公路的各个方面(如弯道、坡度、车道宽度、交通控制装置、路面类型和状况)可以定量地进行评估,从而为几何设计提供合理的基础。在本分析中,假设交通对激励压力势的反应模式决定了任何特定车辆穿越给定路段的行为。这个概念可以用类似于描述可压缩流体中的一维粘性流动的方式定量地表示。由此产生的微分方程的解产生一个参数,该参数是道路显著特征的数值度量。然后提出了确定该参数的程序,使用可测量的车辆速度,从而消除了评估激励压力势的需要。
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引用次数: 3
DRIVER RESPONSE TO AMBER PHASE OF TRAFFIC SIGNALS 驾驶员对交通信号琥珀色相位的反应
Pub Date : 1961-10-01 DOI: 10.1287/OPRE.9.5.650
P. L. Olson, R. Rothery
OBSERVATIONS OF MOTORIST RESPONSE TO THE AMBER PHASE OF TRAFFIC SIGNALS OBTAINED AT FIVE INTERSECTIONS, REPRESENTING THREE SPEED ZONES, ARE PRESENTED. THE DATA GIVE AN ESTIMATE OF THE PROBABILITY OF STOPPING FOR VEHICLES AS A FUNCTION OF THEIR DISTANCE FROM THE INTERSECTION AT THE ONSET OF THE AMBER PHASE OF THE TRAFFIC SIGNAL. THE RESULTS LEAD NO SUPPORT TO A POPULAR HYPOTHESIS: THAT IS, THAT DRIVERS TEND TO TAKE ADVANTAGE OF A LONG AMBER PHASE BY TREATING IT AS AN EXTENSION OF THE GREEN. THE RESULTS OF THE STUDY ARE COMPARED WITH OTHER INVESTIGATIONS PERTAINING TO AMBER PHASE LENGTHS AND INPLICATIONS OF THIS WORK FOR THE DESIGN OF AMBER PHASES ARE DISCUSSED. /AUTHOR/
在五个十字路口,代表三个速度区,给出了驾驶员对交通信号琥珀色相位的反应观察。该数据给出了车辆在交通信号琥珀色阶段开始时距离十字路口距离的函数的停车概率估计。研究结果没有支持一个流行的假设:即司机倾向于利用长琥珀色阶段,将其视为绿色的延伸。将研究结果与其他有关琥珀相长度的研究进行了比较,并讨论了这项工作对琥珀相设计的影响。/作者/
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引用次数: 78
Injury-producing private motor vehicle accidents among airmen 飞行员中造成伤害的私人机动车辆事故
Pub Date : 1961-07-01 DOI: 10.1080/00223980.1961.9916500
J. E. Barmack, D. E. Payne
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引用次数: 26
MEASUREMENT AND INTERPRETATION OF SURFACE VIBRATIONS ON SOIL AND ROADS 土壤和道路表面振动的测量和解释
Pub Date : 1960-08-01 DOI: 10.1088/0031-9112/11/8/001
R. Jones
THE ROAD RESEARCH LABORATORY IS DEVELOPING NONDESTRUCTIVE TECHNIQUES FOR MEASURING THE DYNAMIC MECHANICAL CHARACTERISTICS AND THICKNESSES OF THE LAYERS FORMING A ROAD. THE MATHEMATICAL THEORY FOR COMPUTING STRESSES AND DEFORMATIONS REQUIRES KNOWLEDGE OF THESE DATA AND THE DEVELOPMENT OF THESE TESTING TECHNIQUES IS A NECESSARY STEP TOWARDS A SYSTEM OF PAVEMENT DESIGN BASED ON THE STRESSES ENCOUNTERED IN THE ROAD AND THE MECHANICAL PROPERTIES OF THE MATERIALS. APART FROM THIS, THE TECHNIQUES ARE ALREADY ABLE TO PROVIDE INFORMATION OF IMMEDIATE VALUE IN THAT THEY PROVIDE DATA OF ASSISTANCE IN APPRAISING THE PERFORMANCE OF EXPERIMENTAL AND OTHER ROADS UNDER TRAFFIC, THEY CAN BE USED TO LOCATE AREAS WHERE VARIATIONS OF MECHANICAL PROPERTIES OR THICKNESS OCCUR, AND THEY CAN BE USED TO STUDY THE CHANGES PRODUCED BY TRAFFIC AND WEATHER. THE FIRST PART OF THIS PAPER DEALS WITH THE EXPERIMENTAL TECHNIQUE FOR MEASURING THE WAVE LENGTH AND PHASE VELOCITY OF MECHANICAL VIBRATIONS PROPAGATED ALONG THE SURFACE OF SOIL OR ROAD CONSTRUCTIONS. THE VIBRATIONS ARE PRODUCED ELECTRO-MECHANICALLY BY APPARATUS WORKING WITHIN THE FREQUENCY RANGE FROM 40 TO 60,000 C/S AND HAVE WAVE LENGTHS RANGING FROM A FEW INCHES TO SEVERAL FEET. THE RESULTS ARE NORMALLY EXPRESSED GRAPHICALLY AS THE RELATION BETWEEN PHASE VELOCITY AND THE WAVE LENGTH OBTAINED AT SELECTED FREQUENCIES. THIS CURVE HAS A NUMBER OF CHARACTERISTICS WHICH DEPEND ON THE ELASTIC PROPERTIES AND THE THICKNESSES OF DIFFERENT PARTS OF THE CONSTRUCTION: THE SECOND PART OF THE PAPER DISCUSSES THEORETICAL ANALYSES TO CALCULATE THESE PARAMETERS. SO FAR, MOST OF THE WORK HAS BEEN LIMITED TO EXPERIMENTAL CONSTRUCTIONS AND ALL THE RELEVANT DATA CONCERNING THICKNESSES AND TYPE OF MATERIAL HAVE BEEN KNOWN, WHILE VIBRATORY EXPERIMENTS HAVE ALSO BEEN MADE, WHERE NECESSARY, ON LABORATORY SPECIMENS OF THE MATERIALS TO DETERMINE THEIR ELASTIC PROPERTIES. THESE DATA HAVE ENABLED CHECKS TO BE MADE OF THE VALIDITY OF PREDICTIONS FROM THE VIBRATIONAL EXPERIMENTS. /AUTHOR/
道路研究实验室正在开发无损技术,用于测量形成道路的各层的动态力学特性和厚度。计算应力和变形的数学理论需要这些数据的知识,这些测试技术的发展是朝着基于道路遇到的应力和材料的机械性能的路面设计系统迈出的必要一步。除此之外,这些技术已经能够提供具有直接价值的信息,因为它们为评估实验道路和其他交通道路的性能提供了帮助数据,它们可以用来定位发生机械性能或厚度变化的区域,它们可以用来研究交通和天气产生的变化。本文第一部分讨论了测量沿土壤或道路建筑表面传播的机械振动的波长和相速度的实验技术。振动是由工作在40到60000摄氏度/秒频率范围内的设备产生的,其波长从几英寸到几英尺不等。结果通常用图形表示为相速度与在所选频率下获得的波长之间的关系。该曲线具有许多特征,这些特征取决于结构不同部位的弹性性能和厚度,本文的第二部分讨论了计算这些参数的理论分析。到目前为止,大部分工作都局限于实验结构,所有有关材料厚度和类型的相关数据都是已知的,而在必要时,也对材料的实验室样品进行了振动实验,以确定其弹性特性。这些数据可以用来检验振动实验预测的有效性。/作者/
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引用次数: 5
A Study of Chert and Shale Gravel in Concrete 混凝土中燧石和页岩砾石的研究
Pub Date : 1960-01-01 DOI: 10.5703/1288284314407
R. Schuster
CERTAIN CHERT AND SHALE GRAVELS HAVE LONG BEEN RECOGNIZED AS HARMFUL WHEN INCLUDED IN PORTLAND CEMENT CONCRETE EXPOSED TO FREEZING AND THAWING. MANY ORGANIZATIONS HAVE SPECIFICATIONS LIMITING PERCENTAGES OF THESE MATERIALS IN CONCRETE AGGREGATES, BUT FEW OF THESE SPECIFICATIONS DISTINGUISH BETWEEN TYPES OF CHERT AND SHALE FROM DIFFERENT GEOGRAPHICAL AREAS NOR DO THEY ALWAYS TAKE INTO ACCOUNT THE BASIC PHYSICAL PROPERTIES OF THESE MATERIALS. IN THIS STUDY, PORE CHARACTERISTICS, MINERALOGY, TEXTURE, AND STRUCTURE WERE DETERMINED FOR CHERTS AND SHALES FROM NINE INDIANA GLACIAL GRAVEL DEPOSITS BY MEANS OF MICROSCOPIC PETROGRAPHY, X-RAY DIFFRACTION, AND THE COMMON SPECIFIC GRAVITY AND ABSORPTION TECHNIQUES. BLENDS OF 2, 4, 6, AND 10 PERCENT OF CHERT OR SHALE FROM EACH SOURCE WERE MADE WITH A STANDARD DURABLE CRUSHED LIMESTONE COARSE AGGREGATE, AND THESE BLENDS WERE USED IN 3- X 4- X 16-IN. AIR-ENTRAINED CONCRETE BEAMS SUBJECTED TO UP TO 300 CYCLES OF FREEZING AND THAWING. A MEASURE OF THE AMOUNT OF DEEP-SEATED DETERIORATION OF THE BEAMS WAS PROVIDED BY DURABILITY FACTORS CALCULATED FROM THE RESULTS OF NON-DESTRUCTIVE SONIC TESTING OF THE BEAMS AT INTERVALS DURING FREEZE-THAW TESTING. SEVERITY OF SURFACE DETERIORATION WAS ALSO EVALUATED. THE INFLUENCE OF THE BASIC PROPERTIES OF THE CHERT AND SHALE GRAVELS ON THE RESULTS OF THE FREEZE-THAW TESTS WAS THEN DETERMINED. ON THE BASIS OF THE RESULTS OF THESE TESTS, THE EXISTING SPECIFICATIONS ON CHERTS AND SHALES WERE STUDIED TO DETERMINE WHETHER THE SPECIFICATIONS REALISTICALLY CATEGORIZE THESE MATERIALS. DESPITE SIGNIFICANT DIFFERENCES IN THEIR MINERALOGIES, NO DIFFERENCE WAS NOTED IN THE FREEZE-THAW DURABILITIES OF THE VARIOUS CHERT SAMPLES. FOR ALL THE CHERTS, SIGNIFICANT DEEP- SEATED AND SURFACE DETERIORATION OCCURRED ONLY IN BEAMS CONTAINING 6 TO 10 PERCENT OF MATERIAL WITH A BULK SPECIFIC GRAVITY (SATURATED SURFACE-DRY BASIS) OF LESS THAN 2.45. ALTHOUGH THE BASIC PROPERTIES OF THE SHALES VARIED EVEN MORE WIDELY THAN THOSE OF THE CHERTS, NONE OF THE SHALES CAUSED DEEP-SEATED FAILURE OF THE CONCRETE. HOWEVER, THE MOST POROUS SHALES CAUSED POPOUT DAMAGE, WHICH WAS ESPECIALLY SEVERE AT THE 6 AND 10 PERCENT LEVELS. /AUTHOR/
某些燧石和页岩砾石长期以来一直被认为是有害的,当波特兰水泥混凝土暴露在冷冻和解冻中。许多组织都有限制这些材料在混凝土骨料中的百分比的规范,但这些规范很少区分来自不同地理区域的燧石和页岩类型,也很少考虑到这些材料的基本物理性质。本文采用显微岩石学、x射线衍射、常见比重和吸收技术,对9个印第安那冰川砾石矿床中的燧石和页岩进行了孔隙特征、矿物学、结构和结构分析。将每种来源的燧石或页岩的2,4,6和10%的混合物与标准耐用的碎石灰石粗骨料混合制成,这些混合物用于3- x 4- x 16-in。受300次冻融循环影响的含气混凝土梁。在冻融试验期间,每隔一段时间对梁进行无损声波测试,通过耐久性系数计算出梁的深层劣化程度。还评估了表面恶化的严重程度。然后确定了燧石和页岩砾石的基本性质对冻融试验结果的影响。在这些试验结果的基础上,研究了现有的岩质岩和页岩的规范,以确定规范是否真实地对这些材料进行了分类。尽管矿物学有显著差异,但不同燧石样品的冻融耐久性没有差异。对于所有的岩质,只有在含有6 - 10%体积比重(饱和表面-干基)小于2.45的材料的梁中才会发生显著的深层和表面劣化。尽管页岩的基本性质比燧石的差异更大,但没有一种页岩导致混凝土的深层破坏。然而,最多孔的页岩会造成弹出损害,在6%和10%的水平下尤其严重。/作者/
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引用次数: 6
An Engineering Soil Survey of Fayette County, Kentucky 肯塔基州费耶特县工程土壤调查
Pub Date : 1959-01-01 DOI: 10.13023/KTC.RR.1958.131
R. Deen
AGRICULTURAL SOIL SCIENTISTS HAVE DEVELOPED A SYSTEM OF SOIL CLASSIFICATION AND MAPPING THAT HAS BEEN AND IS CONTINUING TO BE OF GREAT VALUE TO THE SOILS ENGINEER IN RECONNAISSANCE AND MAPPING. THIS REPORT COVERS A STATISTICAL METHOD OF CORRELATION USED IN A PILOT STUDY CONDUCTED IN ORDER TO MAKE ENGINEERING SOILS DATA AVAILABLE FROM A PEDOLOGICAL MAP OF FAYETTE COUNTY, KY. ASSUMING THAT THE RELIABILITY OF PEDOLOGICAL CLASSIFICATIONS HOLDS TRUE FOR ENGINEERING PROPERTIES, THE ENGINEERING TEST CONSTANTS FOR A GIVEN HORIZON OF A GIVEN SOIL SHOULD FALL WITHIN A NARROW RANGE, AND THE LIMITS OF THIS RANGE SHOULD BE REASONABLY DETERMINABLE FROM THE RESULTS OF TESTS ON A SMALL NUMBER OF RANDOM SAMPLES. IN THE PRESENT STUDY A RANGE WITH A CONFIDENCE COEFFICIENT OF 0.90 WAS DETERMINED BY THE STATISTICAL METHOD USED. /AUTHOR/
农业土壤科学家已经开发了一套土壤分类和制图系统,该系统一直并将继续对土壤工程师在侦察和制图方面具有重要价值。本报告涵盖了在试点研究中使用的相关统计方法,以便从肯塔基州费耶特县的土壤学地图中获得工程土壤数据。假设土壤学分类的可靠性适用于工程性质,则对于给定土壤的给定层位,工程试验常数应落在一个狭窄的范围内,并且该范围的极限应从少量随机样本的试验结果中合理确定。在本研究中,采用统计学方法确定置信系数为0.90的范围。/作者/
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引用次数: 3
Stresses and Deflections in Concrete Pavements Continuously Reinforced with Welded Wire Fabric 焊接丝织物连续加固混凝土路面的应力和挠度
Pub Date : 1959-01-01 DOI: 10.5703/1288284314391
M. J. Gutzwiller, J. L. Waling
LABORATORY EXPERIMENTS ON SIMULATED CONTINUOUSLY- REINFORCED CONCRETE SLABS ARE SUMMARIZED, WITH EXPERIMENTAL RESULTS PERTAINING TO SLAB DEFLECTIONS, CRACK WIDTHS, AND STRESSES IN WELDED WIRE FABRIC REINFORCEMENT. SOME OF THE SIGNIFICANT FINDINGS OF THESE LABORATORY EXPERIMENTS ARE COMPARED WITH FIELD OBSERVATIONS REPORTED IN THE LITERATURE AND SEVERAL CRITERIA ARE SUGGESTED FOR OPTIMUM STRUCTURAL DESIGN OF CONTINUOUSLY-REINFORCED PAVEMENTS. SOME OF THE CONCLUSIONS REACHED AS A RESULT OF THIS RESEARCH, SUBJECT TO THE LIMITATIONS IMPOSED BY THE RANGE OF VARIABLES STUDIED ARE: (1) IN ADEQUATELY-REINFORCED CONTINUOUS PAVEMENTS, TEMPERATURE DECREASES OF MORE THAN 30 DEG. BELOW CASTING TEMPERATURE TEND TO INCREASE THE DEFLECTIONS DUE TO VERTICAL (WHEEL) LOADS. TEMPERATURE DECREASES LESS THAN 30 DEG. TEND TOWARD A SLIGHT DECREASE IN DEFLECTIONS. (2) THE PERCENTAGE OF MID-DEPTH REINFORCEMENT HAS AN INFLUENCE ON MAXIMUM DEFLECTIONS DUE TO VERTICAL LOADS, BUT THE MAXIMUM DEFLECTIONS VARY SOMEWHAT INVERSELY WITH THE PERCENTAGE OF REINFORCEMENT. (3) UPPER SURFACE CRACK WIDTHS VARY LINEARLY WITH TEMPERATURE DECREASES IN SLABS INADEQUATELY REINFORCED WITH WELDED WIRE FABRIC BUT WITH ADEQUATE SPLICE LAPS. PAVEMENTS WITH ADEQUATE AMOUNTS OF REINFORCEMENT FORM NEW CRACKS DURING SIZABLE TEMPERATURE DECREASES AND OLD CRACKS DO NOT CONTINUE TO WIDEN IN DIRECT PROPORTION TO TEMPERATURE DROP. (4) MAXIMUM ACTIVE CRACK WIDTHS (DUE TO TEMPERATURE DROPS AND WHEEL LOADS) AT THE UPPER AND LOWER SURFACES OF THE SLAB CAN BE EQUALIZED AND MINIMIZED BY PROPER PLACEMENT OF THE STEEL REINFORCEMENT. LABORATORY EXPERIMENTS SUGGEST THAT TOP AND BOTTOM SURFACE ACTIVE CRACK WIDTHS MIGHT BE APPROXIMATELY EQUALIZED BY PLACEMENT OF THE FABRIC ABOUT 3/4 IN. BELOW MID-DEPTH. (5) AN INCREASE IN THE AVERAGE STEEL STRESS AT A CRACK ACCOMPANIES INCREASED TEMPERATURE DROPS (BELOW CONCRETE CASTING TEMPERATURE), FURTHERMORE THE STRESSES VARY INVERSELY WITH PERCENTAGE OF LONGITUDINAL REINFORCEMENT AT MID-DEPTH. (6) VERTICAL LOADS CONTRIBUTE SIGNIFICANTLY TO STRESSES IN THE REINFORCEMENT. (7) REINFORCEMENT PLACED 1-1/2 IN. ABOVE MID-DEPTH MUST RESIST STRESSES CONSIDERABLY GREATER THAN THE SAME AMOUNT OF REINFORCEMENT PLACED AT MID-DEPTH OR BELOW. /AUTHOR/
总结了模拟连续钢筋混凝土板的室内试验,并给出了有关板挠度、裂缝宽度和焊接钢丝织物钢筋应力的实验结果。将这些实验室实验的一些重要发现与文献中报道的现场观察结果进行了比较,并提出了连续加筋路面优化结构设计的几个准则。受研究变量范围的限制,本研究得出的一些结论是:(1)在适当加筋的连续路面上,温度下降超过30度,低于浇铸温度往往会增加垂直(车轮)荷载引起的挠度。温度下降小于30度时,挠度会有轻微的下降。(2)中深配筋比例对竖向荷载作用下的最大挠度有影响,但最大挠度随配筋比例的增大而呈负相关。(3)焊丝布加固不足但搭接圈数充足的板坯,其上表面裂缝宽度随温度降低呈线性变化。配筋量足够的路面在温度大幅度下降时形成新的裂缝,旧的裂缝不会随着温度下降而继续扩大。(4)板坯上下表面的最大活动裂缝宽度(由于温度下降和车轮荷载)可以通过适当放置钢筋来平衡和最小化。室内实验表明,将织物放置在3/4 in左右,可以使上下表面活动裂纹宽度大致相等。中间深度以下。(5)裂缝处钢的平均应力随温度下降(低于混凝土浇筑温度)的增加而增加,并且应力随中深度纵向配筋百分比的增加呈反比变化。(6)竖向荷载对钢筋应力的贡献较大。(7)钢筋放置1-1/2英寸。中深以上的钢筋必须比同样数量的中深或以下的钢筋承受更大的应力。/作者/
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引用次数: 2
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Highway Research Board bulletin
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