Fracture Mechanics in Pavement Engineering: The Specimen-Size Effect

1997 ◽  
Vol 1568 (1) ◽  
pp. 10-16 ◽  
Author(s):  
Anastasios M. Ioannides
Keyword(s):  
Fracture Mechanics ◽  
Size Effect ◽  
Specimen Size ◽  
Pavement Design ◽  
Crack Model ◽  
Design Procedures ◽  
Engineering Discipline ◽  
Pavement Engineering ◽  
Slow Progress ◽  
Mechanics Concepts

Application of fracture mechanics concepts developed in various branches of engineering to the pavement problem can address current limitations, thereby advancing considerably existing pavement design procedures. The state of the art in fracture mechanics applications to pavement engineering is summarized, and an in-depth discussion of one of the major concerns in such applications, the specimen-size effect, is provided. It is concluded that the fictitious crack model proposed by Hillerborg appears most promising for computerized application to pavements. The similitude concepts developed by Bache will be very useful in such efforts. Both the desirability and the scarcity of suitable candidates to replace Miner’s cumulative linear fatigue hypothesis in conventional pavement design are confirmed. Fracture mechanics is shown to be a very promising engineering discipline from which innovations could be transplanted to pavement activities. Nonetheless, it is pointed out that rather slow progress characterizes fracture mechanics developments in general. Pavement engineers clearly need to remain abreast of and involved in fracture mechanics activities.

STRENGTH SIZE EFFECT IN FIBER COMPOSITES FAILING UNDER LONGITUDINAL AND TRANSVERSE COMPRESSION

2021 ◽  
Author(s):  
JING XUE ◽  
KEDAR KIRANE
Keyword(s):  
Fracture Mechanics ◽  
Size Effect ◽  
Fiber Composites ◽  
Crack Model ◽  
Carbon Fiber Composites ◽  
Compressive Failure ◽  
Transverse Compression ◽  
Longitudinal Compression ◽  
Kink Bands ◽  
Matrix Cracks

The size effect in the structural strength of fiber reinforced composites has been typically analyzed for tensile failures. However, this is not true for the equally important compressive failures, primarily due to the difficulties in conducting compression tests on specimens of multiple sizes. These size effects are analyzed here numerically for two important compressive failure mechanisms in composites, viz. (i) fiber kink bands forming under longitudinal compression (typically accompanied by axial splitting matrix cracks) and (ii) inclined shear cracks forming under transverse compression. The former mechanism is modeled by a semi-multiscale microplane model, while the latter by the fixed crack model. Both models are calibrated and verified using available test data on carbon fiber composites and then used to predict the failure and load bearing capacities of geometrically scaled pre-cracked specimens of different sizes. In all cases, the predicted failure is found to be of a propagating nature, accompanied by release of strain energy from the specimen causing a distinct size effect in the nominal strength. For the composite considered here, under longitudinal compression, the fracture process zone (FPZ) is found to be fairly small (<1 mm) and the strength size effect is seen to follow linear elastic fracture mechanics (LEFM). The size effect deviates from LEFM for smaller specimen sizes due to increased flaw size insensitivity but cannot be fitted by Bažant's size effect law since the geometric similarity of the failure mode is lost. On the other hand, under transverse compression the FPZ is found to be much larger (34 to 42 mm) and the size effect is found to obey Bažant's size effect law, deviating from LEFM. The failure is geometrically similar despite being inclined to the pre-crack. These findings provide evidence of the general applicability of fracture mechanics-based size effect laws to compressive failure in fiber composites, and prompt suitable experimental investigations.

Softening Curve of Dam Concrete by Inverse Analysis and Size Effect of Softening Curve

2012 ◽  
Vol 446-449 ◽  
pp. 64-68
Author(s):  
Zhi Fang Zhao ◽  
Qiu Yu Wang ◽  
Zhi Hua Yang ◽  
Yang Yang
Keyword(s):  
Size Effect ◽  
Inverse Analysis ◽  
Specimen Size ◽  
Crack Model ◽  
Three Point Bending ◽  
Softening Curve ◽  
Increasing Trend ◽  
Maximum Crack ◽  
Fictitious Crack ◽  
Dam Concrete

The softening curves of four groups specimens with different sizes were obtained by inverse analysis based on the fictitious crack model（FCM）and the P-CMOD curve achieved by a three-point bending notched beam (TPB) test. According to the softening curves obtained by inverse analysis, size effect of softening curves was investigated，which shows both the tail of calculated softening curve, namely the maximum crack width wcand fracture energy GFhave an increasing trend with the increase of the specimen size, but no longer to increase when the specimen size attains to a certain level.

scholarly journals Experimental data on strength properties of mussel shell concretes and specimen size effect

Data in Brief ◽  
2021 ◽  
Vol 35 ◽  
pp. 106954
Author(s):  
Costas A. Anagnostopoulos ◽  
Denis Cabja ◽  
Chrysi A. Papadimitriou
Keyword(s):  
Experimental Data ◽  
Size Effect ◽  
Strength Properties ◽  
Specimen Size ◽  
Mussel Shell

scholarly journals Fracture and Size Effect of PFRC Specimens Simulated by Using a Trilinear Softening Diagram: A Predictive Approach

Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 3795
Author(s):  
Fernando Suárez ◽  
Jaime C. Gálvez ◽  
Marcos G. Alberti ◽  
Alejandro Enfedaque
Keyword(s):  
Reinforced Concrete ◽  
Size Effect ◽  
A Priori ◽  
Plain Concrete ◽  
Specimen Size ◽  
Bending Test ◽  
Orientation Factor ◽  
Fibre Reinforced Concrete ◽  
Softening Function ◽  
Three Point Bending

The size effect on plain concrete specimens is well known and can be correctly captured when performing numerical simulations by using a well characterised softening function. Nevertheless, in the case of polyolefin-fibre-reinforced concrete (PFRC), this is not directly applicable, since using only diagram cannot capture the material behaviour on elements with different sizes due to dependence of the orientation factor of the fibres with the size of the specimen. In previous works, the use of a trilinear softening diagram proved to be very convenient for reproducing fracture of polyolefin-fibre-reinforced concrete elements, but only if it is previously adapted for each specimen size. In this work, a predictive methodology is used to reproduce fracture of polyolefin-fibre-reinforced concrete specimens of different sizes under three-point bending. Fracture is reproduced by means of a well-known embedded cohesive model, with a trilinear softening function that is defined specifically for each specimen size. The fundamental points of these softening functions are defined a priori by using empirical expressions proposed in past works, based on an extensive experimental background. Therefore, the numerical results are obtained in a predictive manner and then compared with a previous experimental campaign in which PFRC notched specimens of different sizes were tested with a three-point bending test setup, showing that this approach properly captures the size effect, although some values of the fundamental points in the trilinear diagram could be defined more accurately.

Use of Long-Term Pavement Performance Data to Develop Traffic Defaults in Support of Mechanistic-Empirical Pavement Design Procedures

2003 ◽  
Vol 1855 (1) ◽  
pp. 176-182 ◽  
Author(s):  
Weng On Tam ◽  
Harold Von Quintus
Keyword(s):  
Pavement Design ◽  
Vehicle Classification ◽  
Pavement Performance ◽  
Traffic Data ◽  
Design Procedures ◽  
Load Spectra ◽  
State Highway ◽  
Pavement Structures ◽  
Empirical Design

Traffic data are a key element for the design and analysis of pavement structures. Automatic vehicle-classification and weigh-in-motion (WIM) data are collected by most state highway agencies for various purposes that include pavement design. Equivalent single-axle loads have had widespread use for pavement design. However, procedures being developed under NCHRP require the use of axle-load spectra. The Long-Term Pavement Performance database contains a wealth of traffic data and was selected to develop traffic defaults in support of NCHRP 1-37A as well as other mechanistic-empirical design procedures. Automated vehicle-classification data were used to develop defaults that account for the distribution of truck volumes by class. Analyses also were conducted to determine direction and lane-distribution factors. WIM data were used to develop defaults to account for the axle-weight distributions and number of axles per vehicle for each truck type. The results of these analyses led to the establishment of traffic defaults for use in mechanistic-empirical design procedures.

Modeling of Size Effects on the Flow Stress of Type 304 Stainless Steel and Application in Coining Process

2007 ◽  
Author(s):  
Gap-Yong Kim ◽  
Muammer Koc ◽  
Jun Ni
Keyword(s):  
Grain Size ◽  
Stainless Steel ◽  
Flow Stress ◽  
Size Effect ◽  
Size Effects ◽  
Specimen Size ◽  
304 Stainless Steel ◽  
Length Scales ◽  
Type 304 ◽  
Type 304 Stainless Steel

Application of microforming in various research areas has received much attention due to the increased demand for miniature metallic parts that require mass production. For the accurate analysis and design of microforming process, proper modeling of material behavior at the micro/meso-scale is necessary by considering the size effects. Two size effects are known to exist in metallic materials. One is the “grain size” effect, and the other is the “feature/specimen size” effect. This study investigated the “feature/specimen size” effect and introduced a scaling model which combined both feature/specimen and grain size effects. Predicted size effects were compared with experiments obtained from previous research and showed a very good agreement. The model was also applied to forming of micro-features by coining. A flow stress model for Type 304 stainless steel taking into consideration the effect of the grain and feature size was developed and implemented into a finite element simulation tool for an accurate numerical analysis. The scaling model offered a simple way to model the size effect down to length scales of a couple of grains and extended the use of continuum plasticity theories to micro/meso-length scales.

Implementing the Mechanistic–Empirical Design Guide Procedure for a Hot-Mix Asphalt–Rehabilitated Pavement in Indiana

2005 ◽  
Vol 1919 (1) ◽  
pp. 121-133 ◽  
Author(s):  
Khaled A. Galal ◽  
Ghassan R. Chehab
Keyword(s):  
Hot Mix Asphalt ◽  
Pavement Design ◽  
Design Parameters ◽  
Design Procedures ◽  
Design Concepts ◽  
Asphalt Overlay ◽  
Design Guide ◽  
Strategic Goals ◽  
And Performance

One of the Indiana Department of Transportation's (INDOT's) strategic goals is to improve its pavement design procedures. This goal can be accomplished by fully implementing the 2002 mechanistic–empirical (M-E) pavement design guide (M-E PDG) once it is approved by AASHTO. The release of the M-E PDG software has provided a unique opportunity for INDOT engineers to evaluate, calibrate, and validate the new M-E design process. A continuously reinforced concrete pavement on I-65 was rubblized and overlaid with a 13–in.-thick hot-mix asphalt overlay in 1994. The availability of the structural design, material properties, and climatic and traffic conditions, in addition to the availability of performance data, provided a unique opportunity for comparing the predicted performance of this section using the M-E procedure with the in situ performance; calibration efforts were conducted subsequently. The 1993 design of this pavement section was compared with the 2002 M-E design, and performance was predicted with the same design inputs. In addition, design levels and inputs were varied to achieve the following: ( a) assess the functionality of the M-E PDG software and the feasibility of applying M-E design concepts for structural pavement design of Indiana roadways, ( b) determine the sensitivity of the design parameters and the input levels most critical to the M-E PDG predicted distresses and their impact on the implementation strategy that would be recommended to INDOT, and ( c) evaluate the rubblization technique that was implemented on the I-65 pavement section.

Sign in / Sign up

Export Citation Format

Share Document