scholarly journals On the need of distinguishing ductile and brittle failure modes in timber connections with dowel-type fasteners

2021 ◽  
Vol 242 ◽  
pp. 112496
Author(s):  
Miguel Yurrita ◽  
José Manuel Cabrero
Keyword(s):  
Brittle Failure ◽  
Failure Modes ◽  
Timber Connections

scholarly journals Evaluation of Seismic Demand for Substandard Reinforced Concrete Structures

2018 ◽  
Vol 12 (1) ◽  
pp. 9-33
Author(s):  
Nicholas Kyriakides ◽  
Ahmad Sohaib ◽  
Kypros Pilakoutas ◽  
Kyriakos Neocleous ◽  
Christis Chrysostomou ◽  
...  
Keyword(s):  
Reinforced Concrete ◽  
Seismic Performance ◽  
Performance Prediction ◽  
Brittle Failure ◽  
Failure Modes ◽  
Shaking Table ◽  
Equivalent Linearization ◽  
Diagram Method ◽  
Capacity Curves ◽  
Non Linear

Background: Reinforced Concrete (RC) buildings with no seismic design exhibit degrading behaviour under severe seismic loading due to non-ductile brittle failure modes. The seismic performance of such substandard structures can be predicted using existing capacity demand diagram methods through the idealization of the non-linear capacity curve of the degrading system, and its comparison with a reduced earthquake demand spectrum. Objective: Modern non-linear static methods for derivation of capacity curves incorporate idealization assumptions that are too simplistic and do not apply for sub-standard buildings. The conventional idealisation procedures cannot maintain the true strength degradation behaviour of such structures in the post-peak part, and thus may lead to significant errors in seismic performance prediction especially in the cases of brittle failure modes dominating the response. Method: In order to increase the accuracy of the prediction, an alternative idealisation procedure using equivalent elastic perfectly plastic systems is proposed herein that can be used in conjunction with any capacity demand diagram method. Results: Moreover, the performance of this improved equivalent linearization procedure in predicting the response of an RC frame is assessed herein. Conclusion: This improved idealization procedure has been proven to reduce the error in the seismic performance prediction as compared to seismic shaking table test results [1] and will be further investigated probabilistically herein.

scholarly journals Damage Detection of Common Timber Connections Using Piezoceramic Transducers and Active Sensing

Sensors ◽  
2019 ◽  
Vol 19 (11) ◽  
pp. 2486 ◽  
Author(s):  
Fang Han ◽  
Jinwei Jiang ◽  
Kai Xu ◽  
Ning Wang
Keyword(s):  
Damage Detection ◽  
Lead Zirconate Titanate ◽  
Failure Modes ◽  
Low Cost ◽  
Energy Levels ◽  
Stress Waves ◽  
Active Sensing ◽  
Timber Structures ◽  
Signal Energy ◽  
Timber Connections

Timber structures have been widely used due to their low-cost and environmental-friendly properties. It is essential to monitor connection damage to ensure the stability and safety of entire timber structures since timber connection damage may induce catastrophic incidents if not detected in a timely manner. However, the current investigations on timber connections focus on mechanical properties and failure modes, and the damage detection of timber connection receives rare attention. Therefore, in this paper, we investigate the damage detection of four common timber connections (i.e., the screw connection, the bolt connection, the decussation connection, and the tooth plate connection) by using the active sensing method. The active sensing method was implemented by using a pair of lead zirconate titanate (PZT) transducers: one PZT patch is used as an actuator to generate stress waves, and the other works as a sensor to detect stress waves after propagating across the timber connection. Based on the wavelet packet energy analysis, the signal energy levels of received stress waves under different damage extent are quantified. Finally, by comparing the signal energy between the intact status and the damage status of the timber connection, we find that the energy attenuates with increasing severity of the connection damage. The experimental results demonstrate that the active sensing method can realize real-time monitoring of timber connection damage, which can guide further investigations.

Brittle failure in compression: splitting faulting and brittle-ductile transition

1986 ◽  
Vol 319 (1549) ◽  
pp. 337-374 ◽  
Keyword(s):  
Mathematical Models ◽  
Closed Form ◽  
Brittle Failure ◽  
Failure Modes ◽  
Ductile Failure ◽  
Singular Integral Equations ◽  
Quantitative Model ◽  
Experimental Results ◽  
Laboratory Model ◽  
Brittle Ductile Transition

The micromechanics of brittle failure in compression and the transition from brittle to ductile failure, observed under increasing confining pressures, are examined in the light of existing experimental results and model studies. First, the micromechanics of axial splitting and faulting is briefly reviewed, certain mathematical models recently developed for analysing these failure modes are outlined, and some new, simple closed-form analytic solutions of crack growth in compression and some new quantitative model experimental results are presented. Then, a simple two-dimensional mathematical model is proposed for the analysis of the brittle—ductile transition process, the corresponding elasticity boundary-value problem is formulated in terms of singular integral equations, the solution method is given, and numerical results are obtained and their physical implications are discussed. In addition, a simple closed-form analytic solution is presented and, by comparing its results with those of the exact formulation, it is shown that the analytic estimates are reasonably accurate in the range of the brittle response of the material. Finally, the results of some laboratory model experiments are reported in an effort to support the mathematical models.

Cutting force as an index to identify the ductile-brittle failure modes in rock cutting

2021 ◽  
Vol 146 ◽  
pp. 104834
Author(s):  
Xianwei Dai ◽  
Zhongwei Huang ◽  
Huaizhong Shi ◽  
Xiaoguang Wu ◽  
Chao Xiong
Keyword(s):  
Cutting Force ◽  
Brittle Failure ◽  
Failure Modes ◽  
Rock Cutting

scholarly journals Study on the Mechanical Properties of BFRP Tube Confined Concrete Short Columns under Axial Compression

2020 ◽  
Author(s):  
Xindong Ding ◽  
Shuqing Wang ◽  
Yu Liu ◽  
Zepeng Zheng
Keyword(s):  
Axial Compression ◽  
Brittle Failure ◽  
Failure Modes ◽  
Concrete Strength ◽  
Steel Tube ◽  
Confined Concrete ◽  
Test Results ◽  
Compression Tests ◽  
Short Columns ◽  
Square Steel Tube

Axial compression tests were carried out on 6 square steel tube confined concrete short columns and 6 BFRP square pipe confined concrete axial compression tests. The concrete strength grades were C30, C40, and C50. The test results show that the failure modes of steel pipe and BFRP pipe are obviously different, and the BFRP pipe undergoes brittle failure. Compared with the short columns of concrete confined by BFRP pipes, the ultimate bearing capacity of axial compression is increased by -76.46%, -76.01%, and -73.06%, and the ultimate displacements are -79.20%, -80.78%, -71.71%.

scholarly journals Uniaxial Dynamic Compressive Behaviors of Hydraulic Asphalt Concrete under the Coupling Effect between Temperature and Strain Rate

Materials ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 5348
Author(s):  
Rui Tang ◽  
Zhenpeng Yu ◽  
Guoqing Liu ◽  
Furong Li ◽  
Wenbin Tang
Keyword(s):  
Quantitative Analysis ◽  
Strain Rate ◽  
Temperature Effect ◽  
Asphalt Concrete ◽  
Brittle Failure ◽  
Failure Modes ◽  
Strain Softening ◽  
Coupling Effect ◽  
Peak Stress ◽  
Stress Strain

To investigate the compressive dynamic properties of hydraulic asphalt concrete under various temperatures, four temperatures and four strain rates have been set to perform the uniaxial compression experiments using hydraulic servo machine in this paper. The influence of temperature and strain rate on the failure modes, stress-strain curves and mechanical characteristic parameters of hydraulic asphalt concrete is analyzed and the results reveal that the failure modes and stress-strain curves have significant temperature effect. When the temperature is between −20 °C and 0 °C, the failure mode is dominated by brittle failure of asphalt binder, and hydraulic asphalt concrete shows obvious strain softening. With the addition of temperature, the failure modes of specimens are transferred from brittle failure to ductile failure since the asphalt changes from elastic-brittleness to viscoelasticity. Influenced by temperature effect, the compressive stress-strain curves of hydraulic asphalt concrete show strain hardening while the peak stress of hydraulic asphalt concrete is obviously decreased, and the variation coefficient of peak stress has a power relation with temperature. With successive increases in strain rate, the stress-strain curves of hydraulic asphalt concrete gradually are transferred from strain hardening to strain softening. The peak stress and stiffness modulus of specimens under compression gradually increase, and the dynamic increase factor of peak stress is linearly related with the logarithm value of strain rate after dimensionless treatment. In terms of the quantitative analysis of the experimental data, two relationship models of the coupling effect between temperature and strain rate are proposed. The proposed models have good applicability to the quantitative analysis of the experimental results in the manuscript. This paper offers important insights into the application and development of hydraulic asphalt concrete in hydraulic engineering.

Fragmentation Characteristics of Rocks Under Indentation by a Single Polycrystalline Diamond Compact Cutter

2021 ◽  
Vol 143 (10) ◽  
Author(s):  
Zhaosheng Ji ◽  
Huaizhong Shi ◽  
Xianwei Dai ◽  
Hengyu Song ◽  
Gensheng Li ◽  
...  
Keyword(s):  
Contact Force ◽  
Brittle Failure ◽  
Failure Modes ◽  
Polycrystalline Diamond ◽  
Rake Angle ◽  
Von Mises Stress ◽  
Rock Interaction ◽  
Initiation Point ◽  
Pdc Bit ◽  
Polycrystalline Diamond Compact

Abstract Polycrystalline diamond compact (PDC) bit accounts for the most drilling footage in the development of deep and geothermal resources. The goal of this paper is to investigate the PDC cutter-rock interaction and reveal the rock fragmentation mechanism. A series of loading and unloading tests are conducted to obtain the curves of contact force versus penetration displacement. A single practical PDC cutter is fixed on the designed clamping devices that are mounted on the servo experiment system TAW-1000 in the tests. The craters morphology and quantified data were obtained by scanning the fragmented rock specimen using a three-dimensional morphology scanner. Finally, a numerical model is established to get the stress and deformation fields of the rock under a single PDC cutter. The results show that there are two kinds of failure modes, i.e., brittle failure and plastic failure, in the loading process. Marble is more prone to brittle fracture and has the lowest specific energy, followed by shale and granite. The brittle failure in marble mainly occurs behind the cutter while that happens ahead of the cutter for shale. Curves of contact force versus penetration displacement illustrate that a cutter with a back rake angle of 40 deg has a better penetration result than that with a back rake angle of 30 deg. Enhancing loading speed has a positive effect on brittle fragmentation. The distribution of von Mises stress indicates the initiation point and direction, which has a good agreement with the experiment. The research is of great significance for optimizing the PDC bit design and increasing the rate of penetration.

Strength Demand Issues Relevant for the Seismic Design of Moment-Resisting Frames

2005 ◽  
Vol 21 (2) ◽  
pp. 415-439 ◽  
Author(s):  
Ricardo A. Medina ◽  
Helmut Krawinkler
Keyword(s):  
Seismic Design ◽  
Brittle Failure ◽  
Failure Modes ◽  
Shear Forces ◽  
Moment Resisting Frames ◽  
Weak Beam ◽  
Moment Resisting ◽  
Nonlinear Static ◽  
Current Code ◽  
Code Provisions

This paper deals with the evaluation of strength demands relevant for the seismic design of columns that are part of moment-resisting frames. Regular frames with fundamental periods from 0.3 sec. to 3.6 sec. and number of stories from 3 to 18 are investigated. An evaluation of the relationships between strength demands (e.g., story shear forces, story overturning moments, and moments in columns), ground motion intensity, fundamental period, and number of stories is the focus of this paper. The results from this study demonstrate that the magnitude and distribution over the height of maximum axial and shear forces in columns exposed to severe earthquakes often are not adequately estimated by current seismic design and analysis procedures (e.g., the nonlinear static pushover). Moreover, the potential of plastic hinging in columns is high for regular frames designed according to the strong-column/weak-beam requirements of current code provisions, and more stringent strong-column/weak-beam criteria appear to be called for. The presented results are intended to provide guidance for improvement of seismic design provisions to avoid brittle failure modes in columns of moment-resisting frames.

scholarly journals Study on the Mechanical Properties of BFRP Tube Confined Concrete Short Columns under Axial Compression

2020 ◽  
Author(s):  
Xindong DING ◽  
Shuqing Wang ◽  
Yu Liu ◽  
Zepeng Zheng
Keyword(s):  
Axial Compression ◽  
Brittle Failure ◽  
Failure Modes ◽  
Concrete Strength ◽  
Steel Tube ◽  
Confined Concrete ◽  
Test Results ◽  
Compression Tests ◽  
Short Columns ◽  
Square Steel Tube

Axial compression tests were carried out on 6 square steel tube confined concrete short columns and 6 BFRP square pipe confined concrete axial compression tests. The concrete strength grades were C30, C40, and C50. The test results show that the failure modes of steel pipe and BFRP pipe are obviously different, and the BFRP pipe undergoes brittle failure. Compared with the short columns of concrete confined by BFRP pipes, the ultimate bearing capacity of axial compression is increased by -76.46%, -76.01%, and -73.06%, and the ultimate displacements are -79.20%, -80.78%, -71.71%.

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