elastic stage
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2022 ◽  
Vol 4 (2) ◽  
Author(s):  
Chen Wen-qiang ◽  
Li Yi-jia

AbstractExisting analytical models usually fail to match with the actual conditions due to ignoring the nonlinear behavior of the surrounding material reaction force, which changes progressively with the joint shear displacement from elastic stage to yield stage. To tackle this problem, this study proposes a new analytical model to describe the bolt deformation and bolt contribution from elastic stage to plastic stage. The developed model is verified by available experimental direct shear tests of bolted joints and compared with existing models. Then, based on this model, the effects of the joint dilation angle, the bolt installation angle, the friction angle, and the surrounding material strength on bolt contribution are also analyzed and its implication is further discussed. Our results show that the proposed model can precisely describe the evolution of bolt contribution from elastic stage to plastic stage. Compared with surrounding material strength, the augmentation of the joint dilation angle and friction angle is more beneficial to increase the bolt contribution and the optimal installation angle. The work presented is to attempt to provide a reference for the understanding of bolting mechanism of jointed rock mass, the development of bolting theories and the practice of bolting engineering.


2021 ◽  
Vol 1 (74) ◽  
pp. 62-64
Author(s):  
B. Zimin ◽  
A. Khitrina

Observations of a solid body with internal stresses have been carried out, this model allows us to describe the energy dissipation during the change of the elastic stage of deformation to the plastic one. The dependence of heat release on the heat physical properties of the contacting structures is noted.


2021 ◽  
Author(s):  
Wengui Li ◽  
Bin Lei ◽  
Zhiyu Luo ◽  
Fuzhi Yang

Applying of demolished concrete lumps (DCLs) in the pier foundation is an effective way to improve the efficiency of construction waste resource utilization. Fifty-two cylindrical specimens with the size of ∅ 250 mm × 500 mm were fabricated by mixing of DCLs with the fresh concrete (FC) and used to investigate the influence of two key factors, the gradation of the DCLs and the height setting of layered “steel mesh,” on the uniaxial compression and flexural strength properties of the compound concrete specimens. Results indicate that the layered “steel mesh” in the specimens can restrain the settlement and segregation of the DCLs and improve the compressive and flexural strength of the specimens significantly. Normally, there are two types of failure damage mode of the test pieces, the failure of the interface between DCLs and the FC and the fracture failure of the DCLs. When the stress level is below 0.5, the test piece is in the elastic stage. Crack development occurs when stress level further increase to 0.7–0.9. The pieces with the layered pouring height of H2 and the DCLs of R3 present the optimum compressive strength and flexural strength and also best construction effect.


2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Qiupeng Yuan ◽  
Guangxiang Xie ◽  
Lei Wang ◽  
Zhenhua Jiao ◽  
Peng Zou ◽  
...  

In this study, a uniaxial impact compression test was performed on coal samples with length-to-diameter L / D ratios of 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, and 1 using a Φ 50 mm split Hopkinson pressure bar (SHPB) test system. This study researched the stress uniformity and deformation behavior of coal samples with different L / D ratios during dynamic compression, defined the stress equilibrium coefficient ξ , proposed a new method for determining whether a sample meets the stress uniformity hypothesis, and obtained the critical L / D ratio of 0.6 and the optimal L / D ratio of 0.3 or 0.4 for coal samples to obtain the stress equilibrium. The experimental results showed that the dynamic stress-strain curve of coal had an elastic stage, a plastic stage, and a failure stage. As the L / D ratio increased, the proportion of the elastic stage to the prepeak curve of the samples declined progressively; with an increase in the L / D ratio, the peak part of the curve also changed from “sharp” to “stagnated,” while an increase in the plasticity led to strain softening. As the L / D ratio of the samples increased, the average strain rate decreased approximately as a power function, and the decreasing trend was gradually reduced from 296.49 s−1 ( L / D =0.3) to 102.85 s−1 ( L / D =1), with a reduction of approximately 65.31%. With an increase in the L / D ratio, the peak strain gradually decreased exponentially. This study concluded that the SHPB test protocol design is of a certain reference value for low-density, low-strength, heterogeneous brittle materials, such as coal.


Author(s):  
Jiang Guan ◽  
Feng Zhongju ◽  
Ruixin Zhao ◽  
Zhangzhengxu Zhangzhengxu ◽  
Junqiang Wen

The Unloading Pull-out Test Method (UPTM) is proposed to evaluate the residual stress of existing anchorage systems and explore the actual stable state of the slope before excavation. A series of destructive pull-out tests are applied to detect the working state of the existing rock bolts. The working load and ultimate load of the existing bolts are determined by field test measurement of the P-S curve. The experimental result showed that a displacement increment of the bolts was present in the elastic stage, the elastoplastic stage, the slip stage, and the debonding stage. The working load and the ultimate load were in the elastoplastic stage and the debonding stage respectively. The working load of the bolts is closely related to the sliding deformation. The ultimate load of the bolts, however, is only related to the design parameters, slope lithology and other factors. After 20 years of natural forces acting on the bolts in the slope, their ultimate bearing capacity had a stress loss of 24.0% ~ 32.0%.


2021 ◽  
Vol 2021 ◽  
pp. 1-18
Author(s):  
Liyun Li ◽  
Junyan Han ◽  
Xiangjian Wang

The previous soil spring model cannot describe the nonlinear characteristics of soil in elastic stage, and there are some shortcomings in the selection of soil spring parameters in some published codes. Meanwhile, the literatures about the spring model for pipe and silty clay interaction are rare. Thus, a series of pipe-silty clay interaction tests are conducted, and some corresponding experimental results are obtained. The effects of soil properties, pipe diameter, and embedment depth on the horizontal resistance of soil are studied. Based on the experimental results, the failure modes of soil are analysed, and a formula to calculate the peak resistance of soil and the corresponding displacement to peak resistance are proposed. Finally, a method to describe the nonlinear spring stiffness coefficient of silty clay is recommended.


2021 ◽  
Vol 30 (1) ◽  
pp. 71-74
Author(s):  
A. Morgun ◽  
◽  
I. Met ◽  
I. Shevchenko ◽  
◽  
...  

The main mission of civil engineer is to ensure he reliability of the structure with maximum efficiency of time, materials and energy. In construction, everything must be provided in the design workshop - both strength and economic feasibility. Balancing on the "edge of the abyss" requires a precise mathematical apparatus. The modern mathematical apparatus of soil mechanics is based on the solutions of the theory of elasticity and the theory of limit equilibrium. In this case, the calculation of the bases is carried out from the conditions of purely elastic connection and the ultimate loads are determined without connection with deformations. Most of the elastic-plastic deformation - from the end of the elastic stage to the loss of stability is not covered by the calculation models. At the same time, the reserves of the elastic-plastic zone allow to increase the load on the foundation, provided that the subsidence of the elastic stage does not yet reach the maximum allowable value for this structure. The boundary element method (BEM) allows to solve problems of this kind. The main disadvantage of foundations on a natural basis is the complexity of its manufacture and high material consumption. These shortcomings can be eliminated by building foundations in cavities of a predetermined shape, which are formed in the soil. These include foundations in compacted ditches, which are arranged in wells with expansion at the bottom. The soil retains its full-fledged composition, so that the work includes a side surface that receives part of the vertical load and provides significant resistance to horizontal forces. The paper presents a method of integration of a mathematical model of behavior under load of foundations in a compacted pit with a numerical BEM. A theoretical study presents the effect of the addition of sand-gravel mixture on the bottom of the compacted pit on the bearing capacity of pyramidal piles.


Metals ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 28
Author(s):  
Hui Guo ◽  
Yunlai Deng ◽  
Shitong Fan ◽  
Renjie Pan

Crushing performance is being widely investigated because it is the key performance indicator of the thin-walled beam structure in automobile safety components. In this study, five kinds of ageing state with different yield strengths were prefabricated with a self-developed KHC63 alloy. Using a rectangular tube profile, the physical relationship between crushing properties and mechanical properties, and the structure of the profile, were studied. According to variation characteristics, the crushing curve was divided into four typical stages: elastic stage, bending stage, compaction stage and folding stage. In the elastic stage, the peak load of the component is related to material elasticity and structure elasticity, and the relationship is approximately linear. In the bending stage, the driving factor of plastic hinge deformation is the bending moment, and it is always constant. In the compaction stage, the crushing curve correlates well with the cosine function. In the folding stage, the crushing process begins to lose stability and is hard to predict. The mathematical relationships between force and displacement were established according to the characteristics of each stage, and the calculated results were close to the measured results except for the folding stage. The deviation of the calculated energy absorption from the measured data in the first three stages is only 4.3%, but it is 10.6% in the folding stage. The calculation method used for the first three stages is, therefore, suitable.


2020 ◽  
Vol 2020 ◽  
pp. 1-18
Author(s):  
Jun Chuai ◽  
Zhilong Hou ◽  
Zhenqing Wang ◽  
Lumin Wang

Reliable joint connection is key to designing prefabricated structures. To study the mechanical properties of the vertical joints in the designed prefabricated underground silo steel plate concrete composite wall and verify their reliability, flexural and compressive experiments were conducted using two groups of six full-scale steel plate concrete composite wall specimens; the mechanical properties between jointed and jointless specimens were compared and analyzed. The experimental results indicate that all specimens are in the elastic stage during the entire loading process; further, they exhibit large stiffness and high bearing capacity without damages. Thus, the designed vertical joints of the steel plate concrete composite wall provide a reliable connection that is safe and applicable. Further, the flexural and compressive properties of jointed and jointless specimens were found to be similar; the newly designed prefabricated underground silo steel plate concrete composite wall could be designed using the “equivalent principle” that the combined wall design calculation with the joint could be equivalent to that without the joint.


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