scholarly journals Seismic Performance of Deposit Slopes With Underlying Bedrock Before and After Reinforcement by Stabilising Piles

2021 ◽  
Author(s):  
Zhiliang Sun ◽  
Kong Lingwei ◽  
Bai Wei ◽  
Wang Yong
Keyword(s):  
Seismic Performance ◽  
Seismic Waves ◽  
Bending Moment ◽  
Resultant Force ◽  
Shaking Table ◽  
Slope Instability ◽  
Dynamic Responses ◽  
Seismic Excitation ◽  
Ground Acceleration ◽  
Response Characteristics

Abstract The seismic performance of stabilising piles used to reinforce underlying bedrock in a deposit slope is a complex soil-structure interaction problem, on which there is limited design guidance on the optimum use of a single row of rock-socketed piles to reinforce such slopes. Two centrifuge shaking-table model tests at a geometric scale of 1:50 were conducted to ascertain the dynamic responses of the underlying bedrock deposit slopes without and with the use of stabilising piles during an earthquake. Multi-stage seismic waves with various peak accelerations were applied from the bottom of each model. Under seismic excitation, the differences in the response accelerations between the deposit and bedrock increase significantly with the increase in amplitude of the input seismic waves. The two are prone to uncoordinated movement, which leads to slope instability. Setting stabilising piles reduces the crest settlement and angular deformation and changes the natural frequency of the slope crest. The presence of the rock-socketed stabilising piles can bridge the uncoordinated movement of the bedrock and the overlying deposit to some extent. According to the mobilised pile bending moment, shear force, lateral pile-soil load distribution, and pile displacement, the dynamic response characteristics of stabilising piles under continuous multi-level seismic excitation were analysed. The resultant force arising from a distributed load increment on the piles caused by an earthquake is mainly concentrated in the upper part (the point of action of the resultant force is 1.54m below the slope surface). With increases in the peak ground acceleration (PGA) of the input motion, the resistance of the bedrock in front of the stabilising piles increases; moreover, with the increase of PGA, the peak resistance under the bedrock surface of the stabilising piles gradually moves downwards. This finding indicates that the strong seismic motion significantly changes the embedded working state of the stabilising pile.

scholarly journals Seismic Performance of Deposit Slopes with Underlying Bedrock before and after Reinforcement by Stabilizing Piles

2021 ◽  
Vol 11 (12) ◽  
pp. 5664
Author(s):  
Zhiliang Sun ◽  
Lingwei Kong ◽  
Wei Bai ◽  
Yong Wang
Keyword(s):  
Seismic Performance ◽  
Seismic Waves ◽  
Shaking Table ◽  
Dynamic Responses ◽  
Ground Acceleration ◽  
Stabilizing Piles ◽  
Multi Stage ◽  
Before And After ◽  
Table Model ◽  
Input Motion

The seismic performance of stabilizing piles used to reinforce underlying bedrock in a deposit slope is a complex soil–structure interaction problem. Two centrifuge shaking table model testswere conducted to ascertain the dynamic responses of the underlying bedrock deposit slopes without and with the use of stabilizing piles during an earthquake. Multi-stage seismic waves with various peak accelerations were applied from the bottom of each model. The differencesin the response accelerations between the deposit and bedrock increase significantly with the increase in amplitude of the input seismic waves. The presence of the rock-socketed stabilizing piles can bridge the uncoordinated movement of the bedrock and the overlying deposit to some extent. The resultant force arising from a distributed load increment on the piles caused by an earthquake is mainly concentrated in the upper part. With increases in the peak ground acceleration of the input motion, the resistance of the bedrock in front of the stabilizing piles increases and the peak resistance under the bedrock surface of the stabilizing piles gradually moves downwards.This finding indicates that the strong seismic motion significantly changes the embedded working state of the stabilizing pile.

Shaking Table Test on Seismic Performance of L- and V-Sectioned Reinforced Concrete Columns

2015 ◽  
Vol 09 (04) ◽  
pp. 1550010
Author(s):  
Xuan-Huy Nguyen ◽  
Xuan-Dat Pham ◽  
Xuan-Chieu Luong
Keyword(s):  
Reinforced Concrete ◽  
Seismic Performance ◽  
Shaking Table Test ◽  
Absorption Capacity ◽  
Shaking Table ◽  
Experimental Program ◽  
Ground Acceleration ◽  
Cross Sectional ◽  
Response Characteristics ◽  
Current Test

This paper presents an experimental program to investigate the effects of cross-sectional shape on the seismic performance of irregularly shaped reinforced concrete (RC) columns. Five groups of specimens that were one-quarter of typical columns of a prototype medium-rise building were tested to failure using shaking table. The loading procedure was successively increasing peak ground acceleration until the test structure collapsed. The specimens were designed with the same cross-section area but different flange width and flange thickness. The seismic response characteristics of all specimens such as drift capacity, energy absorption capacity and failure mechanisms of each specimen group are evaluated, compared and discussed in detail. Based on the current test data, design recommendation is provided to assist engineers in designing such irregularly shaped columns.

Dynamic Response Characteristics of Underground Powerhouse Caverns for Sandaowan Hydropower Station

2011 ◽  
Vol 382 ◽  
pp. 80-83 ◽  
Author(s):  
Zhen Zhong Shen ◽  
Hua Chun Ren
Keyword(s):  
Seismic Waves ◽  
Low Frequency ◽  
Time History ◽  
Element Model ◽  
Frequency Characteristics ◽  
Dynamic Responses ◽  
Principal Stresses ◽  
Underground Powerhouse ◽  
Response Characteristics ◽  
Set Up

According to the practical situation, the 3-D finite element model of Sandaowan underground powerhouse caverns on Taolai River is set up for analyzing the behaviors under earthquake action. Based on static stress field of the surrounding rock mass, and with the selection of appropriate seismic waves for dynamic time-history analysis method, the dynamic responses of underground powerhouse caverns are analyzed. It is shown that the time-history waveform of dynamic displacement of given points has a very similar variation regularity with that of acceleration, and the wave phases of both are almost synchronous. The dynamic displacements and principal stresses of the given points on rock walls are with the vibration of low-frequency characteristics, the acceleration response is with the vibration of high-frequency characteristics.

scholarly journals Shaking Table Test for Evaluating the Seismic Performance of Steel Frame Retrofitted by Buckling-Restrained Braces

2021 ◽  
Vol 2021 ◽  
pp. 1-17
Author(s):  
Tingting Wang ◽  
Jianhua Shao ◽  
Chao Zhao ◽  
Wenjin Liu ◽  
Zhanguang Wang
Keyword(s):  
Seismic Performance ◽  
Shear Force ◽  
Seismic Waves ◽  
Shaking Table Test ◽  
Steel Frame ◽  
Shaking Table ◽  
Frame Structure ◽  
Acceleration Response ◽  
Buckling Restrained Brace ◽  
Interstory Drift

To investigate the seismic performance of buckling-restrained braces under the earthquake action, the shaking table test with a two-story 1/4 scale model is carried out for the ordinary pure steel frame and the buckling-restrained bracing steel frame with low-yield-point steel as the core plate. The failure modes, dynamic characteristics, acceleration response, interstory drift ratio, strain, shear force, and other mechanical properties of those two comparative structures subjected to different levels of seismic waves are mainly evaluated by the experiment. The test results show that under the action of seismic waves with different intensities, the apparent observations of damage occur in the pure frame structure, while no obvious or serious damage in the steel members of BRB structure is observed. With the increase in loading peak acceleration for the earthquake waves, the natural frequency of both structures gradually decreases and the damping ratio gradually increases. At the end of the test, the stiffness degradation rate of the pure frame structure is 11.2%, while that of the buckling-restrained bracing steel frame structure is only 5.4%. The acceleration response of the buckling-restrained bracing steel frame is smaller than that of the pure steel frame, and the acceleration amplification factor at the second story is larger than that at the first story for both structures. The average interstory drift ratios are, respectively, 1/847 and 1/238 for the pure steel frame under the frequent earthquake and rare earthquake and are 1/3000 and 1/314 for the buckling-restrained bracing steel frame, which reveals that the reduction rate of lateral displacement reaches a maximum of 71.71% after the installation of buckling-restrained brace in the pure steel frame. The strain values at each measuring point of the structural beam and column gradually increase with the increase of the peak seismic acceleration, but the strain values of the pure steel frame are significantly larger than those of the buckling-restrained bracing steel frame, which indicates that the buckling-restrained brace as the first seismic line of defense in the structure can dramatically protect the significant structural members. The maximum shear force at each floor of the structure decreases with the increase in height, and the shear response of the pure frame is apparently higher than that of the buckling-restrained bracing structure.

scholarly journals Effect of Embedment on Generated Bending Moment in Raft Foundation under Seismic Load

2020 ◽  
Vol 26 (4) ◽  
pp. 161-172
Author(s):  
Abeer A. A Hanash ◽  
Mahmoud D. Ahmed ◽  
Abdulmotalib I. Said
Keyword(s):  
Reinforced Concrete ◽  
Physical Model ◽  
Sandy Soil ◽  
Excitation Frequency ◽  
Bending Moment ◽  
Shaking Table ◽  
Seismic Excitation ◽  
Seismic Load ◽  
Embedment Depth ◽  
Raft Foundation

This research shows the experimental results of the bending moment in a flexible and rigid raft foundation rested on dense sandy soil with different embedded depth throughout 24 tests. A physical model of dimensions (200mm*200mm) and (320) mm in height was constructed with raft foundation of (10) mm thickness for flexible raft and (23) mm for rigid raft made of reinforced concrete. To imitate the seismic excitation shaking table skill was applied, the shaker was adjusted to three frequencies equal to (1Hz,2Hz, and 3Hz) and displacement magnitude of (13) mm, the foundation was located at four different embedment depths (0,0.25B = 50mm,0.5B = 100mm, and B = 200mm), where B is the raft width. Generally, the maximum bending moment decreased with increasing the embedment depth from zero to B, by (75%,41%, and 43%) for the flexible raft under (1, 2 and 3) Hz respectively, for the rigid raft the maximum bending moment decreased by (62%, and 37%) under (1and 2) Hz respectively, for 3Hz excitation frequency, the direction of behavior wasn't the same for the case of the rigid raft foundation as the maximum bending moment increased with increasing the embedment depth from zero to (0.25B,0.5B and B) by (142% , 268% and 5%) compared with the surface raft foundation.

Seismic performance of semi-tenon joints reinforced by steel angle in traditional timber buildings

2020 ◽  
Vol 23 (11) ◽  
pp. 2318-2332
Author(s):  
Jianyang Xue ◽  
Guoqi Ren ◽  
Jiaheng Zhang ◽  
Dan Xu
Keyword(s):  
Seismic Performance ◽  
Numerical Study ◽  
Bending Moment ◽  
Flexural Capacity ◽  
Response Characteristics ◽  
Steel Angle ◽  
Rotation Stiffness ◽  
Joint Connection ◽  
Reversed Loading ◽  
Steel Angles

This article presents an experimental and numerical study on seismic performance of semi-tenon joints reinforced by steel angle in traditional timber buildings. Five specimens with two different reinforced connections and one unreinforced connection subjected to low-cyclic reversed loading on the bending moment are examined. The unreinforced connection consists of left and right beams inserted into the column that has been used in setting up the mortise before assembly. The first type of reinforced connection is formed by bottom steel angles bolted to the column and jointed to the beam by means of bolts. The second type of reinforced connection is made up of top and bottom steel angles bolted to the column and connected to the beam relying on vertical and transverse bolts. Moreover, two reinforcement techniques aimed at enhancing the seismic performance of semi-tenon joints are investigated, including the change of steel angle limb length and the variation of steel angle limb thickness. The test setup, joint connection, reinforced conditions, and material properties are introduced through detailed account of the experimental results and observations. The key behavioral patterns are identified from the experiments and the main response characteristics such as hysteresis, stiffness, flexural capacity, energy dissipation, and the failure mechanism. This article demonstrates that the steel angle can enhance the flexural capacity of the semi-tenon joints significantly. Besides, the use of greater limb thickness steel angle is shown to be an effective detail for adequately increasing the flexural capacity and rotation stiffness of the joints. Finite element simulations of experiments are also conducted, together with a detailed description of the modeling methods, so as to gain further insight into the influence of various factors on the behavior of joints.

scholarly journals Shaking Table Tests on Sliding Displacements of Loess Slope under Coupling Effect of Rainfall and Earthquake

2019 ◽  
Vol 2019 ◽  
pp. 1-11
Author(s):  
Xiaojun Yin ◽  
Lanmin Wang
Keyword(s):  
Seismic Waves ◽  
Coupling Effect ◽  
Test System ◽  
Shaking Table ◽  
Slope Instability ◽  
Shaking Table Tests ◽  
Loess Slope ◽  
Artificial Rainfall ◽  
Similarity Ratio ◽  
Slope Design

Shaking table tests were performed to investigate whether the coupling effect of rainfall and earthquake induces the loess slope instability. The loess slope model was made by using the similarity ratio based on a real slope. Artificial rainfall was carried out, and then seismic waves were loaded step by step to adopt a large shaking table of 4∗6 m. The displacement in x, y, and z directions and absolute displacement of loess slope (ux, uy, uz, and ua) were measured to use the XTDIC displacement test system in 50 s when the seismic waves at peak acceleration were loaded to 600 gal, 700 gal, 800 gal, 976 gal, and 1300 gal, respectively. The results showed that the acceleration of one point was much larger than the other. ua occurred when seismic waves were loaded to 700 gal, and uamax was obtained when seismic waves were loaded to 1300 gal finally. The umax would reach in 20∼25 s, which was the period of amplitude peak. The theoretical value was larger than the test value for the critical seismic acceleration coefficient. Loess liquefaction appeared along the slope top under 976 gal loading condition. The change of displacement in y direction is the main reason for the curve trajectory of the sliding block, and the displacement differences of adjacent measuring points are the main reason for the formation of the sliding block. This study can provide a theoretical basis for loess slope design and risk management.

scholarly journals An Analysis of the Impact Exerted on Bearing Capacity of Pier and Pile after Increasing Pile Cap Height

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Xianbin Huang ◽  
Chenyang Liu ◽  
Song Hou ◽  
Chunyang Chen ◽  
Yahong Wangren ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Bearing Capacity ◽  
Seismic Waves ◽  
Bending Moment ◽  
Simulation Method ◽  
Ground Acceleration ◽  
Numerical Simulation Method ◽  
River Bed ◽  
Pile Cap ◽  
The Impact

An analysis was carried out in this paper on the bearing capacity of pier pile and seismic performance rule when the low-pile cap is increased by 1 meter, 2 meters, and 3 meters. The bottom of the pile cap of pier no. 11 of Minjiang River bridge faces three “lows”: 7.6 meters lower than island, 4.6 meters lower than natural river bed, and 6.5 meters lower than low water level. The numerical simulation method is adopted to input three seismic waves of Wolong, Bajiao, and EL to evaluate the bearing capacity of pier and pile under strong earthquakes. Using the standard formula and numerical simulation method, it is observed that the bending moment and axial force of bridge pier show an insignificant change under different seismic waves when the pile cap is increased by 0–3 meters. With peak ground acceleration increased to 0.35 g, the vertical bearing capacity and flexural capacity of pier and pile gratify the requirements; however, the pile foundation will be subject to compression and bending damage.

Seismic response characteristics of multi-story subway station through shaking table test

2021 ◽  
pp. 136943322199329
Author(s):  
Zhiyi Chen ◽  
Pengfei Huang ◽  
Wei Chen
Keyword(s):  
Seismic Response ◽  
Shaking Table Test ◽  
Earth Pressure ◽  
Frequency Component ◽  
Shaking Table ◽  
Dynamic Responses ◽  
High Frequency Component ◽  
Subway Station ◽  
Response Characteristics ◽  
Dynamic Earth Pressure

A series of shaking table tests were carried out to investigate the seismic response characteristics of a multi-story subway station. Dynamic responses, including accelerations of the soils and the underground structure, layer drift, dynamic earth pressure, and lateral deformation of soils were recorded and analyzed. Several seismic characteristics of multi-story subway station structures are figured out. It is found that in addition to the racking deformation, the rotation vibration is observed for the multi-story subway station subjected to acceleration waves. From the viewpoint of frequency, the low-frequency component and high-frequency component of the acceleration response of the subway station represent the translation and rotation component of the multi-story subway structure, respectively. In addition, the rotation vibration of the deep-depth structure leads to the local squeezing and detachment from the surrounding soils alternately at both top and bottom ends of the sidewalls. This results in the hump-shaped distribution of dynamic earth pressure. The racking deformation of the multi-story subway station has a linear relationship with the dynamic earth pressure at a certain area along the sidewall, where the top of hump-shaped distribution of dynamic earth pressure is.

scholarly journals Dynamic Response of Seismic Dangerous Rock Based on PFC and Dynamics

2020 ◽  
Vol 2020 ◽  
pp. 1-19
Author(s):  
Yun Tian ◽  
Linfeng Wang ◽  
Honghua Jin ◽  
Biao Zeng
Keyword(s):  
Dynamic Response ◽  
Low Frequency ◽  
Peak Stress ◽  
Slope Instability ◽  
Dynamic Responses ◽  
Distribution Model ◽  
Distribution Models ◽  
Response Characteristics ◽  
Crack Propagation Process ◽  
The Impact

Rock slope instability by earthquakes results in substantial economic and property losses. The calculation method of interlayer load and stability coefficient of horizontal complex layered rock slopes in high-intensity areas is established from material mechanics, fracture mechanics, and dynamics. The stability of horizontal layered dangerous rock is calculated after combining it with PFC simulation technology to verify the rationality of the calculation in the Wenchuan area of Sichuan Province. The dynamic response characteristics of dangerous rocks under different weathering degrees are also analyzed. The results show that both methods have an excellent early warning effect on earthquake dangerous rocks. Among the PGA amplification factors, Model 1 has a relatively uniform distribution, Model 2 has a zigzag distribution, Models 3 and 4 have a “U”-shaped distribution, and the most severe acceleration dynamic responses are 4-1 and 4-2 rock blocks. The dynamic acceleration response of mudstone is affected by the crack propagation process of the upper sandstone and exhibits a particular elevation amplification effect. The peak stress gradually decreases with the increase in weathering and elevation. The stress change of the inner chain No. 2 in the horizontal x and y directions is severe, and the stress response of the outer chain No. 1 in the vertical z-direction is severe. It recommends that earthquake disaster protection projects should pay attention to the impact of low-frequency (0–10 Hz) and high-frequency (250 Hz) earthquakes on slope stability.

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