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For this study, the geological engineering features and possible failure modes of the Dabenliu quarry slope in the Jinping-I Hydropower Station were qualitatively analyzed before a method for setting viscous boundary and an algorithm for modeling pre-stressed cables were embedded into a DDA (Discontinuous Deformation Analysis) computer code to analyze the deformation of the slope under seismic loading. Our simulation results revealed that the middle and upper parts of the slope slipped along the bedding joints (interlayer shear zones) and that the lower part buckled and collapsed after the slope was excavated. This is a typical slipping–buckling failure mode characterized by upper-slipping followed by lower-buckling. Based on the distribution of the simulated internal force of the anchor cables, the reinforcement scheme was adjusted by strengthening the support for the middle and lower parts of the slope, whereas the length and pre-stress of the anchor cables were reduced for the upper part of the slope. The adjusted reinforcement scheme can ensure the stability of the slope under the action of a magnitude 7 earthquake, and the slope may lose stability with no evident collapse under the action of a magnitude 8 earthquake. Finally, the simulation results were verified via a comparison with the monitoring data regarding the slope. [ABSTRACT FROM AUTHOR]

For this study, the geological engineering features and possible failure modes of the Dabenliu quarry slope in the Jinping-I Hydropower Station were qualitatively analyzed before a method for setting viscous boundary and an algorithm for modeling pre-stressed cables were embedded into a DDA (Discontinuous Deformation Analysis) computer code to analyze the deformation of the slope under seismic loading. Our simulation results revealed that the middle and upper parts of the slope slipped along the bedding joints (interlayer shear zones) and that the lower part buckled and collapsed after the slope was excavated. This is a typical slipping–buckling failure mode characterized by upper-slipping followed by lower-buckling. Based on the distribution of the simulated internal force of the anchor cables, the reinforcement scheme was adjusted by strengthening the support for the middle and lower parts of the slope, whereas the length and pre-stress of the anchor cables were reduced for the upper part of the slope. The adjusted reinforcement scheme can ensure the stability of the slope under the action of a magnitude 7 earthquake, and the slope may lose stability with no evident collapse under the action of a magnitude 8 earthquake. Finally, the simulation results were verified via a comparison with the monitoring data regarding the slope.

In the process of deep coal mining, roadway deformation and collapse are very easy to occur, seriously affecting the working environment in the underground and personnel safety. Therefore, it is very important to promote roadway stability analysis and support scheme design to ensure safety and environmental stability of coal mining. Based on this, this paper firstly analyzes the stability of roadway and surrounding rock in the process of deep coal mining by designing the roadway deformation mechanics model, and finds that the deformation of roadway and surrounding rock will gradually deteriorate with the development of coal mining operation, and transverse deformation and longitudinal deformation finally are 1.100m and 0.486m respectively. Such a huge deformation of surrounding rock will badly threaten the stability of roadway and the safety of coal mining workers, so it is of great engineering significance to carry out the corresponding support design. At the same time, the simulation analysis of roadway stability also found that the collapse and yield of surrounding rock will first appear in the two roadway bottom angles, and gradually spread upward and finally through. Combined with the actual mining engineering, the design length of roadway support bolt should not be less than 1.95m, and its diameter should not be less than 22mm, the length of anchor cable and row spacing should be designed as 8.0m and 3.25m respectively. In addition, the reinforcement support after mining needs constant group large deformation anchor cable technology, and the diameter of the anchor cable should not be less than 24mm, and the length still needs to be designed as 8.0m. The research can provide guarantee for the stability of deep coal mining roadway and underground working environment. [ABSTRACT FROM AUTHOR]

Abstract This paper presents two shear tests of ¾-in. diameter cast-in anchors embedded in the plastic hinge zone of reinforced concrete columns. Design codes, such as ACI 318-14, require special reinforcement for concrete anchors in concrete that could be substantially damaged during an earthquake. The test anchors in this study were equipped with the anchor reinforcement recommended and verified in the literature. The column specimens were subjected to quasi-static cyclic loading before the test anchors were loaded in shear. Steel fracture was achieved in both test anchors despite cracks and concrete spalling occurred to the concrete within the plastic hinge zones. Meanwhile, the measured anchor capacities were smaller than the code-specified capacity, especially for the anchors subjected to cyclic shear. Concrete cover spalling was found critical to the observed capacity reduction, which caused combined bending and shear action in the anchor bolts. Measures should be developed to mitigate such adverse impact. In addition, further studies are needed for post-installed anchors before practical applications.

This paper presents a study of cast-in anchors in reinforced concrete subjected to both monotonic and cyclic tension. Laboratory tests using 25 mm [1 in.] diameter anchor bolts showed that the code-conforming anchor reinforcement may not ensure anchor steel failure though it effectively prevented concrete breakout. Based on the observations and other tests in the literature, recommendations for the design of anchor tension reinforcement were proposed, which consists of (1) load-carrying reinforcement in the direction of the anchors; (2) crack-controlling reinforcement in all directions that have a limited edge distance; and (3) local confining reinforcement near the anchor head if side-face blowout may control the failure. The proposed anchor reinforcement was proven effective using additional laboratory tests. Further studies are needed to verify the reinforcement design for anchor connections. [ABSTRACT FROM AUTHOR]

The proper design and execution of joints is one of the basic preconditions for efficient functioning of precast concrete frames. Headed reinforcement bars are an efficient technique to anchor tensile forces in beam-to-column joints. In comparison to traditional anchorage techniques that consist in developing tensile bars in the form of a bend or a hook, headed bars allow for optimization of the amount of steel and prevent congestion of reinforcement in the column. The present paper deals with tests of short headed bars anchoring tensile forces in compact columns. Practical benefits yielding from the research are shown on examples of industrial building products. [ABSTRACT FROM AUTHOR]

In calculation of steel and concrete foundation joints, design of anchors in concrete is significantly important. Currently, design of anchors in concrete is based on the Technical Specification CEN/TS 1992-4: Design of fastenings for use in concrete which has already a status of a pre-standard. This theoretical study is focused on modification factors which influence characteristic resistance of headed steel anchor group embedded in concrete and subjected to axial tension only. The effect of overlapping of the concrete failure cones of individual anchors within the group on characteristic resistance modification factors was considered. The aim of the paper is to show influence of particular modification factors considered in case of the narrow RC-members and in case of disturbance of the distribution of stresses in concrete due to boundary edges. These two effects usually influence resistance in tension of anchors embedded in the columns (edge breakout). Also, the additional strength due to presence of so called “anchor reinforcement” extended into the area of the concrete breakout cone is mentioned. [ABSTRACT FROM AUTHOR]

• Concrete breakout failure can limit moment transfer of column-foundation connection. • Distributed shear reinforcement can increase concrete breakout strength. • Novel design methodology is proposed for shear-reinforced concrete breakout. • Alternative to current anchor reinforcement or supplementary reinforcement concepts. Recent studies have shown that the strength of column-foundation connections carrying moment can be limited by the concrete breakout failure mode. Distributed shear reinforcement in the concrete breakout cone region has been observed to increase the strength and displacement capacity of structural connections governed by breakout. However, the ACI 318–19 building code does not allow designers to consider this strength increase. Rather, the code allows the use of anchor reinforcement provided that the concrete contribution to strength is ignored. This paper proposes a design methodology to calculate the breakout strength considering the additive effect of concrete and reinforcement. Physical test data and finite element simulations from previous studies were used to calibrate the proposed strength equations. Detailing requirements are discussed. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a study of the failure analysis of anchors in shear in simulated seismic loads. Ductile failure is critical for anchor design in seismic applications to avoid brittle catastrophe while existing design codes and guidelines that usually accept steel failure as ductile failure are insufficient, and may overestimate shear capacities and ductility. In this study ductility was evaluated based on both effective confinement due to anchor reinforcement and ductile steel. Those anchors with the proposed reinforcement showed a significantly high strength and exhibited great ductility due to effective confinement. Three types of anchor steel were also evaluated. The influences of failure modes, shear capacities and ductility of anchors were taken in account by defining exposed length. Test results indicated both effective confinement and specified ductile steel could ensure anchor have good seismic performance. [Copyright &y& Elsevier]

Existing design codes recommend hairpins and surface reinforcement consisting of hooked bars encasing an edge reinforcement to improve the behavior of anchor connections in shear. Concrete breakout is assumed to occur before anchor reinforcement takes effect in the current design methods. This paper presents an alternative design method for anchor shear reinforcement. The proposed anchor shear reinforcement consists of a group of closed stirrups proportioned to resist the code-speciied anchor steel capacity in shear and placed within a distance from the anchor bolt equal to the front-edge distance. Steel fracture was achieved in the tests of twenty 25 mm (1 in.) reinforced anchors with a front-edge distance of 152 mm (6 in.). Meanwhile, the observed anchor capacities were smaller than the code-speciied anchor steel capacity in shear because concrete cover spalling caused combined bending and shear action in the anchor bolts. Reinforcing bars are needed along all concrete surfaces to minimize concrete damage in front of reinforced anchors for consistent seismic behavior in shear. [ABSTRACT FROM AUTHOR]

Abstract: The roof collapse accident happens frequently in the mining affected roadway reinforced by anchors, which makes the roadway unsafe. Based on the damage analysis of roof strata, composite material mechanic rationale is adopted to deduce the calculating formulas of anchor reinforcing potential coefficient which is represented by the ratio of the limit roof collapse span between after anchor reinforcement and before anchor reinforcement. By using anchor reinforcing potential coefficient, this paper puts forward a new anchor support calculating method for the roadway affected by mining. It has been tested in Yanzhou mining area and Xinwen mining area. The results show that the new method is safe and reliable, and valuable for generalization [Copyright &y& Elsevier]