1.1 该测试方法使用荷载-挠度曲线得出的参数评估纤维增强混凝土的弯曲性能，该曲线是通过使用闭环伺服控制测试系统在第三点荷载下测试简支梁而获得的。 1.2 该试验方法用于确定第一峰值和峰值荷载以及通过将其插入中给出的断裂模量公式中计算的相应应力 Eq 1 。它还要求确定规定挠度下的残余载荷，通过将其插入中给出的断裂模量公式中计算出相应的残余强度 Eq 1 看见 注1 ). 它规定了根据达到规定挠度的载荷-挠度曲线下的面积来确定试样韧性（见 注2 )以及相应的等效抗弯强度比。 注1: 残余强度不是真正的应力，而是使用简单的工程弯曲理论计算的线弹性材料和总（未开裂）截面特性的工程应力。 注2: 以荷载-挠度曲线下面积表示的试样韧性是特定试样能量吸收能力的指标，其大小直接取决于试样的几何形状和荷载配置。 1.3 该试验方法采用两种优选的试样尺寸，即在300 mm[12 in.]跨度上试验的100 mm×100 mm×350 mm[4 in.×4 in.×14 in.]，或在450 mm[18 in.]跨度下试验的150 mm×150 mm×500 mm[6 in.×6 in.×20 in.]。允许使用与两种首选样本尺寸不同的样本尺寸。 1.4 单位-- 以国际单位制或英寸磅单位表示的数值应单独视为标准。每个系统中规定的值可能不是完全相等的；因此，每个系统应独立使用。将两个系统的值合并可能导致不符合标准。 1.5 本标准并不旨在解决与其使用相关的所有安全问题（如有）。本标准的使用者有责任在使用前制定适当的安全、健康和环境实践，并确定监管限制的适用性。 1.6 本国际标准是根据世界贸易组织技术性贸易壁垒委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认的标准化原则制定的。 ====意义和用途====== 5.1 第一峰值强度表征了纤维增强混凝土在开裂开始前的弯曲行为，而特定挠度下的残余强度表征了开裂后的残余承载力。试样韧性是衡量试样能量吸收能力的指标。 每个参数的适当性取决于拟议应用的性质以及可接受的开裂和挠度适用性水平。纤维增强混凝土受到混凝土中纤维数量和类型的不同影响。在某些情况下，纤维可以增加指定挠度下的残余载荷和韧性，同时产生等于或仅略大于无纤维混凝土的弯曲强度的第一峰值强度。在其他情况下，纤维可能会显著增加第一峰值和峰值强度，同时在特定挠度下影响残余承载能力和试样韧性的相对较小的增加。 5.2 通过该试验方法确定的第一峰值强度、峰值强度和残余强度反映了纤维增强混凝土在静态弯曲载荷下的行为。在该试验中获得的能量吸收的绝对值与纤维的性能几乎没有直接关系- 钢筋混凝土结构，因为它们直接取决于试样的尺寸和形状以及荷载布置。 5.3 该试验方法的结果可用于比较各种纤维增强混凝土混合物的性能或用于研究和开发工作。它们还可用于监测混凝土质量，验证是否符合施工规范，获得纯弯曲纤维增强混凝土构件的抗弯强度数据，或评估使用中的混凝土质量。 5.4 该标准试验方法的结果取决于试样的尺寸。 注5: 使用单一尺寸的成型试样获得的结果可能与较大或较小的成型试样、大型结构单元中的混凝土或从此类单元锯切的试样的性能不一致。这种差异可能是因为在含有与十字架相比相对较长的纤维的模塑样品中，优先纤维排列的程度变得更加明显- 模具的截面尺寸。此外，对于给定的跨中挠度，厚度明显不同的结构构件会经历不同的最大裂缝宽度，结果是纤维会经历不同程度的拔出和延伸。

1.1 This test method evaluates the flexural performance of fiber-reinforced concrete using parameters derived from the load-deflection curve obtained by testing a simply supported beam under third-point loading using a closed-loop, servo-controlled testing system. 1.2 This test method provides for the determination of first-peak and peak loads and the corresponding stresses calculated by inserting them in the formula for modulus of rupture given in Eq 1 . It also requires determination of residual loads at specified deflections, the corresponding residual strengths calculated by inserting them in the formula for modulus of rupture given in Eq 1 (see Note 1 ). It provides for determination of specimen toughness based on the area under the load-deflection curve up to a prescribed deflection (see Note 2 ) and the corresponding equivalent flexural strength ratio. Note 1: Residual strength is not a true stress but an engineering stress computed using simple engineering bending theory for linear elastic materials and gross (uncracked) section properties. Note 2: Specimen toughness expressed in terms of the area under the load-deflection curve is an indication of the energy absorption capability of the particular test specimen, and its magnitude depends directly on the geometry of the test specimen and the loading configuration. 1.3 This test method utilizes two preferred specimen sizes of 100 mm by 100 mm by 350 mm [4 in. by 4 in. by 14 in.] tested on a 300 mm [12 in.] span, or 150 mm by 150 mm by 500 mm [6 in. by 6 in. by 20 in.] tested on a 450 mm [18 in.] span. A specimen size different from the two preferred specimen sizes is permissible. 1.4 Units— The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard. 1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee. ====== Significance And Use ====== 5.1 The first-peak strength characterizes the flexural behavior of the fiber-reinforced concrete up to the onset of cracking, while residual strengths at specified deflections characterize the residual capacity after cracking. Specimen toughness is a measure of the energy absorption capacity of the test specimen. The appropriateness of each parameter depends on the nature of the proposed application and the level of acceptable cracking and deflection serviceability. Fiber-reinforced concrete is influenced in different ways by the amount and type of fibers in the concrete. In some cases, fibers may increase the residual load and toughness capacity at specified deflections while producing a first-peak strength equal to or only slightly greater than the flexural strength of the concrete without fibers. In other cases, fibers may significantly increase the first-peak and peak strengths while affecting a relatively small increase in residual load capacity and specimen toughness at specified deflections. 5.2 The first-peak strength, peak strength, and residual strengths determined by this test method reflect the behavior of fiber-reinforced concrete under static flexural loading. The absolute values of energy absorption obtained in this test are of little direct relevance to the performance of fiber-reinforced concrete structures since they depend directly on the size and shape of the specimen and the loading arrangement. 5.3 The results of this test method may be used for comparing the performance of various fiber-reinforced concrete mixtures or in research and development work. They may also be used to monitor concrete quality, to verify compliance with construction specifications, obtain flexural strength data on fiber-reinforced concrete members subject to pure bending, or to evaluate the quality of concrete in service. 5.4 The results of this standard test method are dependent on the size of the specimen. Note 5: The results obtained using one size molded specimen may not correspond to the performance of larger or smaller molded specimens, concrete in large structural units, or specimens sawn from such units. This difference may occur because the degree of preferential fiber alignment becomes more pronounced in molded specimens containing fibers that are relatively long compared with the cross-sectional dimensions of the mold. Moreover, structural members of significantly different thickness experience different maximum crack widths for a given mid-span deflection with the result that fibers undergo different degrees of pull-out and extension.