Study On Earthquake Response Of PHC Pipe Pile Considering Soil-Pile-Structure Interaction

PHC pipe pile (Prestressed high-strength concrete pipe pile) due to its hollow sections in terms of stiffness and shear strength was significantly weaker than the same size entity pile, and its seismic capacity is also weak. China is earthquake country, there are wide high seismicity regions, and it restricts the popularization and application of PHC piles. Therefore, the study of the earthquake response of PHC pile, especially its applicability in high seismicity region is essential. In this paper, the study of earthquake response of PHC pile considering Soil-Pile-Structure interaction is presented. A. In this paper, study works include a shake table model test mainly and finite element analysis supplemented is presented.1. On the basis of access to a large number of domestic and foreign literatures, theoretical study and calculation methods and test progress of the earthquake response of pile research considering soil-pile-structure interaction is summaried and analysis.2. A PHC Pile-Soil-Structure Interaction shake table test is design and implementation. A layer shear deformation soil box container is selected used. There are three layers foundation soil:clay and silt and sand. There are three pile models:single pile and three piles and six piles, and the six piles model superstructure twice increase different counterweight. There are three input seismic waves:El Centro wave and Taft wave and artificial wave, and there are five different sizes of peak acceleration for each seismic wave. In addition, liquefaction test also carried out for each model.3. Use of large-scale finite element software ABAQUS, PHC Pile-Soil-Structure Interaction three-dimensional computational model is established, dynamic calculation and analysis is carried out. B. Shaking table model test data is comprehensive collection and analysis, and compared with finite element results, some important conclusions are obtained:1. To single-pile model and three-pile model, the maximum strain occurr in the top of pile, and down fast decay along the pile, at about6times pile diameter from the top of pile, strain of single pile reduced by80%-90%, strain of three piles reduced by55%-75%, and continue down gradually decay until the bottom of the pile.2. To six-pile model, the maximum strain occurr in the top of pile in weak earthquakes, and down fast decay along the pile, at about6times pile diameter from top of pile, strain reduced by35%-50%, and continue down gradually decay until the bottom of the pile. There are2-3strain mutation point along the pile, with the increase in vibration intensity, strain of each mutant point increases rapidly, exceed the strain in top of pile gradually. Especially the strain of point about11times pile diameter from top of pile increases the most prominent, and become the largest strain point when the conditions of strong earthquakes.3. With increase in the number of pile, model dynamic response gradually weakened, the strain and bending moment of the pile reduce gradually, distribution of strain and bending moment more linear along the pile, the maximum and minimum differential is gradually reduced. It is shown that compared to the single-pile model, the maximum tensile strains of the three-pile model and six-pile model drop by10%-50%and40%-80%respectively, whereas the maximum bending moment drop by30%-55%and70%-80%respectively, the soil-pile interface pressure reduces by20%-70%and30%-80%respectively, superstructure lateral displacement reduces by6%-25%and15%-40%respectively.4. To the single-pile and three-pile and six-pile models, the peak strain distribution on both sides of every pile is asymmetry. Especially to six-pile model, the strain distribution on both sides of pile is huge difference.5. With the vibration continued, model system natural frequency decreases, damping increases. With the increase in vibration intensity, soil-pile-structure interaction effects increase, nonlinearity effects of soil enhancement. The nonlinearity effects of soil between piles is weaker than soil beside pile, the nonlinearity effects of soil beside pile are weaker than soil far from pile. The damage behaviors for systems with more piles are less severe than those with fewer piles.6. The affect of superstructure weight gradually increased to structural system is complex interactions; include the dynamic response of structural system, the size and distribution of pile strain and bending moment, the upper structure displacement.7.With the saturation of the soil, vibration caused by the liquefaction of the sand layer, the nonlinearity effects of liquefied soil enhancement, transmitted vibration diminished capacity, and the liquefied soil lead to a certain amount of shock absorption and isolation. After soil liquefaction, strain and bending moment of the piles overall generally increases, the distribution are more linear along the pile. In liquefied soil, pile-soil interface contact pressure significantly reduced. In a amount of weak shock conditions, the lateral displacement of structure is slightly smaller, but in the rest conditions, the lateral displacement of structure generally increases.8. The results of the shaking table model test and finite element analysis is compared, and the reasonable of calculation and the reliability of shaking table test is verified.9. The results of this preliminary investigation further indicate the feasibility of exploiting PHC piles in8degree high seismicity regions. It is also suggested that more research efforts are required for extensive application of PHC piles in such areas.