Test and Finite Element Analysis of Gravity Load Designed Precast Concrete Wall Under Reversed Cyclic Loads

This research studies the lateral behavior of precast concrete wall panel applicable for a 2-story building. The specimens consist of precast and cast in-situ reinforced concrete bearing wall with 3/4 scaled. The precast wall panel was designed for gravity load only. The specific connection in this study was the welded connection between dowel bar and steel plate embedded in precast wall which was the famous one of the connection for precast bearing wall system in Thailand. The specimens are tested under reversed cyclic loadings through hydraulic actuator in laboratory. The tested results reveal that the precast concrete wall can resist maximum lateral load and show almost the same behavior as cast in-situ RC wall. The cracks of precast wall panel are concentrated around the connection while cast in-situ RC wall are flexural and shear cracks dominant 500 millimeters above the footing of wall. The superimposed technique of the element in FEM analysis is used to model the connection of precast wall. The prediction by FEM analysis for cyclic behavior, hysteretic loop and maximum load are matched with the test results for both specimens

Lateral Loading Test of Reinforced Concrete Bored Pile in Stiff Clay and Near Slope

Staff residence of University of Phayao has been constructed near slope. The inhabitants in the residence are concerned about the lateral strength of the pile foundation during earthquake. This paper involves the evaluation of reinforced concrete bored piles of the residence under lateral loading. In field experiment, two full-scale bored piles were built near the slope of 1:1.5 adjacent to the residence. Two lateral load patterns that push the piles in and out were applied at the pile head. The maximum value of the lateral force was 65 kN representing the base shear force due to earthquake in Thailand. The test results show that the lateral displacements of the pile do not exceed 3 mm and stress in the longitudinal reinforcement is below the yield point. It is implied that the bored piles of staff residence can resist the lateral load imposed on the structure during an earthquake. For the analysis, the pile is modeled using frame elements and the surrounding soil is assigned by horizontal springs. The stiffness of springs is validated by comparing to the test results of the previous researches and this study. It is found that using the proper soil spring stiffness and flexural rigidity values in the structural pile analysis can capture elastic responses including the lateral displacement, bending moment and depth of inflection point

Tests of Inclined Concrete-Filled Steel Tubular Stub Columns under Vertical Cyclic Loading

This paper presents an experimental study on the cyclic behavior of fifteen concrete-filled steel tubular columns subjected to vertical cyclic loading. All test samples’ cross-sectional area is 75 × 75 mm2 square, and they are 500 mm long. The main variables in the test are the thickness of the steel tube (1.8 and 3.0 mm with the width-to-thickness ratios (b/t) of 41.7 and 25), the strength of the infilled concrete (no-fill, 23 MPa, and 42 MPa), and the inclined angle (0, 4, and 9 degrees). The results show that all samples failed due to local buckling in compression followed by tearing of the steel tube in tension. The inclination angles of 4 and 9 degrees decreased the vertical compressive capacity of the 1.8 mm vertical hollowed steel column by 34 and 39 percent, respectively. However, the infilled concrete and thicker tube (3.0 mm) could substantially reduce the adverse effect of the inclination angle. The compressive ductility of the hollowed column with the thinner tube was significantly enhanced by the infilled concrete as well

Performance of Concrete Confined with a Jute–Polyester Hybrid Fiber Reinforced Polymer Composite: A Novel Strengthening Technique

The strengthening and rehabilitation of concrete members is an important issue which arises worldwide. Carbon, aramid and glass fiber reinforced polymer (FRP) composites are mainly used for strengthening and rehabilitation. However, its use is limited on a small scale because of its high price, lack of availability and environmental impacts. The solution of this issue gives rise to the use of locally available natural fibers and low-cost synthetic fibers. This paper presents the experimental and analytical results of circular and square concrete columns confined with jute–polyester hybrid FRP composites. The main objective of this study is to evaluate the viability and performance of concrete confined with the hybridization of jute and polyester (FRP) composite sheets to utilize its superior properties. A novel hybrid technique has been applied for the wrapping of fiber sheets. The fiber sheets were applied in such a way that a uniform bond between the inner and outer layer was achieved. A total of 32 plain, standard size circular and square concrete specimens, externally wrapped with a jute–polyester FRP (JPFRP) composite, were tested under monotonic axial compressive loads. The result shows that JPFRP confinement increased the strength, strain and ductility index ranged between 1.24 and 2.61, 1.38 and 8.97, and 4.94 and 26.5 times the un-jacketed specimen, respectively. Furthermore, the wrapping has a significant effect on the low-strength specimens, having a circular cross-section. For high strength specimens, the post-peak stress-strain behavior was dominated by the outer polyester jacket because of its large rupture strain. Additionally, the test results were used to evaluate the existing strength-strain models derived for conventional FRPs. The models predicted values either underestimating or overestimating the compressive strength and strain of JPFRP-confined specimens. However, the strength models performed better than the strain models. The JPFRP wrapping significantly enhanced the strength, fracture energy, ductility index, and post-peak response. Therefore, JPFRP confinement can be used for a small-scale application, where little strength and high ductility is demanded. Moreover, it can be used to prevent the peeling of the concrete cover and moisture penetration into the concrete

การประเมินกำลังต้านแผ่นดินไหวของอาคารโดยคำนึงถึงโครงสร้างฐานรากเสาเข็มSeismic Evaluation of Building Considering Pile Foundation

บทความนี้นำเสนอผลการศึกษาเปรียบเทียบผลการประเมิน และผลตอบสนองของโครงสร้างอาคารต้านแผ่นดินไหวโดยใช้สเปกตรัมในพื้นที่จังหวัดพะเยา ด้วยแบบจำลองโครงสร้างอาคารที่มีเฉพาะโครงสร้างด้านบนเพียงอย่างเดียว และแบบจำลองที่มีทั้งโครงสร้างด้านบนและโครงสร้างฐานรากพร้อมกัน โดยโครงสร้างฐานรากได้ใช้เสาเข็มและสปริงเพื่อแทนผลของดินที่อยู่ด้านข้างเสาเข็ม ผลการศึกษาพบว่า แบบจำลองอาคารที่มีทั้งโครงสร้างด้านบนและโครงสร้างเสาเข็มพร้อมกัน ทำให้คาบธรรมชาติในโหมดพื้นฐานเพิ่มขึ้น และมีรูปแบบและสัดส่วนการสั่นไหวที่แตกต่างจากแบบจำลองที่ไม่มีเสาเข็ม แบบจำลองที่มีเสาเข็มมีสติฟเนสการต้านแรงด้านข้างลดลงแต่ไม่ได้ลดแรงต้านสูงสุดของอาคาร และถูกประเมินด้วยแรงแผ่นดินไหวที่ลดลงจึงพบระดับความเสียหายที่ลดลงด้วย ผู้วิจัยได้ทดลองเปลี่ยนลักษณะชั้นดินให้มีความแตกต่างกันพบว่า การคำนึงถึงการวิเคราะห์โครงสร้างอาคารที่คำนึงถึงโครงสร้างฐานรากจะช่วยลดแรงแผ่นดินไหวที่ใช้ประเมินได้มากในกรณีดินที่อ่อน แต่โครงสร้างอาคารจะมีการเสียรูปที่มากขึ้น ดังนั้นการจำลองโครงสร้างอาคารจำเป็นต้องพิจารณาโครงสร้างฐานรากในกรณีที่อาคารอยู่บนดินอ่อนเพื่อให้ประเมินสมรรถนะของของอาคารได้อย่างเหมาะสมThis article presents a comparative study of the evaluation results and responses of the building under seismic load using Phayao Province spectrum. The comparisons are made from the two different building models consisting of the model with the only super structure and the one with both super structure and pile foundation. The foundation model is constructed with frame elements and springs representing pile embedded in soil under lateral load. Based on the study results, the building model with pile foundation has higher natural frequency in fundamental mode shape and has different mode shapes and modal participation ratios compared with the building model without pile. The building model with pile tend to reduce the lateral stiffness but does not reduce the maximum lateral resistance. It was also assessed by the reduced seismic force and the lower level of damage was also found. The parametric study of the building model with pile foundation embedded in various types of soil indicated that, the model will significantly reduce seismic evaluation force, especially in case of soft soil but the model has more deformation. The building model should consider sub structure, especially in case of soft soil, in order to evaluate the seismic performance of the building properly