• Geomechanics and Engineering
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• v.38 no.1
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• pp.15-28
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• 2024

The rapid development of the economy has compelled the widen of highways, and the main challenge of this undertaking lies in the uneven settlement of road embankments. Through field and numerical experiments, this study explores the deformation mechanism of shallow buried pipelines due to road widening. The utilization of Plaxis3D software, which is adapt at simulating complex engineering geological conditions, enables the simulation of the settlement of both the central and right-side road embankments. Comparing with other numerical software such as ABAQUS and COMSOL, Plaxis provided more constitutive models including HS, HSS and Hoek-Brown model. The work concludes that the uneven settlement of road cross-sections is positively correlated with the horizontal distance from the pipeline, with a maximum settlement of 73 mm observed after construction. Furthermore, based on the Winkler's assumption, theoretical settlement and stress calculation methods are established. Results indicate that the maximum difference between the calculated values of this formula and simulated values is 1.9% and 7%, respectively. Additionally, the study investigates the stress and settlement of the pipeline's top under different angles to understand its behavior under various conditions. It finds that with traffic loads applied to the new embankment, a lever effect occurs on the lower pipeline, with the fulcrum located within the central isolation zone, leading to a transition in curve type from "single peak and single valley" to "double peak and single valley." Moreover, the settlement of pipelines on both sides of the central isolation zone and the normal stress of the pipeline's top section are symmetrical.

• Earthquakes and Structures
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• v.22 no.6
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• pp.539-548
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• 2022

Steel plate shear walls (SPSWs) are one of the most important and widely used lateral load-bearing systems. The reason for this is easier execution than reinforced concrete (RC) shear walls, faster construction time, and lower final weight of the structure. However, the main drawback of SPSWs is premature buckling in low drift ratios, which affects the energy absorption capacity and global performance of the system. To address this problem, two groups of SPSWs under cyclic loading were investigated using the finite element method (FEM). In the first group, several series of circular rings have been used and in the second group, a new type of SPSW with concentric circular rings (CCRs) has been introduced. Numerous parameters include in yield stress of steel plate wall materials, steel panel thickness, and ring width were considered in nonlinear static analysis. At first, a three-dimensional (3D) numerical model was validated using three sets of laboratory SPSWs and the difference in results between numerical models and experimental specimens was less than 5% in all cases. The results of numerical models revealed that the full SPSW undergoes shear buckling at a drift ratio of 0.2% and its hysteresis behavior has a pinching in the middle part of load-drift ratio curve. Whereas, in the two categories of proposed SPSWs, the hysteresis behavior is complete and stable, and in most cases no capacity degradation of up to 6% drift ratio has been observed. Also, in most numerical models, the tangential stiffness remains almost constant in each cycle. Finally, for the innovative SPSW, a relationship was suggested to determine the shear capacity of the proposed steel wall relative to the wall slenderness coefficient.

• Structural Engineering and Mechanics
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• v.56 no.6
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• pp.899-916
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• 2015

Upgrading or strengthening of existing reinforced concrete (RC) infrastructure is an emerging demand nowadays. Near Surface Mounted (NSM) technique is very promising approach for flexural strengthening of RC members. However, premature failure such as concrete cover separation failure have been a main concern in utilizing this technique. In this study, U-wrap end anchorage with carbon fiber reinforced polymer (CFRP) fabrics is proposed to eliminate the concrete cover separation failure. Experimental programs were conducted to the consequence of U-wrap end anchorage on the flexurally strengthened RC beams with NSM-steel. A total of eight RC rectangular beam specimens were tested. One specimen was kept unstrengthened as a reference; three specimens were strengthened with NSM-steel bars and the remaining four specimens were strengthened with NSM-steel bars and U-wrap end anchorage using CFRP fabrics. A 3D non-linear finite element model (FEM) was developed to simulate the flexural response of the tested specimens. It is revealed that NSM-steel (with and without end-anchors) significantly improved the flexural strength; moreover decreased deflection and strains compared with reference specimen. Furthermore, NSM-steel with end anchorage strengthened specimens revealed the greater flexural strength and improve failure modes (premature to flexure) compared with the NSM-steel without end anchorage specimens. The results also ensured that the U-wrap end anchorage completely eliminate the concrete cover separation failure.

• The Journal of Korean Academy of Prosthodontics
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• v.46 no.5
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• pp.479-489
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• 2008

Statement of the problem: Under anatomical limitations on maxillary posterior region, a poor crown-to root ratio acting on dental implants can result in undesirable stress in surrounding bone, which in turn can cause bone defects and eventual failure of implants. Purpose: The purpose is to compare stress distribution due to different crown-root ratio and effect of splinting between natural teeth and implants in maxillary molar area under different loads. Material and methods: Analysis of stress arising supporting bone of the natural teeth and the implant was made with 3-dimensional finite element method. The model simulated naturel teeth was made with 2nd premolar and 1st molar in the maxillary molar region (Model T). The model simulated implants placed on same positions with two parallel implants of Straumann Dental Implant cemented abutment (Model I). Each model was designed in different crown-root ratio (0.7:1, 1:1, 1.25:1) and set cement type gold crown to make it non-splinted or splinted. After that, 300 N force was loaded to each model in five ways (Load 1: middle of occlusal table, Load 2: middle of buccal cusp, Load 3: middle of lingual cusp, Load 4: horizontal load to buccal cusp of anterior abutment only, Load 5: horizontal load to middle of buccal cusp of each abutment), and stress distribution was analyzed. Results and conclusion: On all occasions, stress was concentrated at the cervical region of the implant. Under load 1, 2 and 3, stress was not increased even when crown-root ratio increases, but under load 4 and 5, when crown-root ratio increases, stress also increased. There was difference in stress values between natural teeth and implants when crown-root ratio gradually increases; In case of natural teeth, splinting decreased stress under vertical and horizontal loads. In case of implants, splinting decreased stress under vertical loads 1,2 and 3, but increased maximal stress under loads 2 and 3. Under horizontal loads, splinting decreased stress, however the effect of splinting decreased under load 5 than load 4. Furthermore, the stress was increased, when crown-root ratio is 1.25:1. Clinical implications: This limited finite element study suggests that the stress on supporting bone may be increased under non-axial loads and poor crown-root ratio. Under poor crown-root ratio, excessive stress was generated at the cervical region of the implant, and decreased splinting effect for stress distribution, which can be related to clinical failure.

• International Journal of Highway Engineering
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• v.9 no.1 s.31
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• pp.1-15
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• 2007

The objective of this paper is the establishment of finite element analysis frame work for pavement research. Finite element analysis results simulating various loading experiments are verified with sensor measurements obtained from the KHC Test Road. The accuracy of the finite element analysis can be supported by these efforts so that it helps spread out the finite element analysis to pavement research and design processes. The finite element model used in this research is the full 3D nonlinear model including concrete slab, lean concrete base, subbase, shoulder, dowel, and tie-bar. In order to accomplish the accurate verification, the loading condition and the pavement temperature distribution are exactly simulated with field measured data. The curling behavior and the strain distribution are compared with measured responses from the loading tests with a truck and the FWD. Strain and curling predictions from the concrete slab are matched well with measured responses but the strain prediction from the lean concrete base is not matched with measured response. In addition, the magnitude of permanent curling is evaluated with the finite element analysis.

• Journal of the Korean Arthroscopy Society
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• v.16 no.2
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• pp.160-166
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• 2012

Purpose: The aim of this study was to determine the patterns of the stress distribution within the reconstructed anterior cruciate ligament (ACL) double bundles in response to an anterior tibial load and rotatory load at $45^{\circ}$ flexed knee model by use of a 3-dimensional finite element analysis (FEM). Materials and Methods: The $0^{\circ}$ and $45^{\circ}$ flexed 3-D knee model were reconstructed based on the high resolution computed tomography (CT) images from the right knee of a healthy male subject. To simulate double bundle ACL reconstruction, in $0^{\circ}$ analytic model, four 7 mm diameter tunnels were created at the center of each anteromedial (AM) and posterolateral (PL) footprints on the femur and tibia. The grafts were inserted into the corresponding bone tunnels and then reconstructed knee model was flexed to $45^{\circ}$. As a next step, the 5 mm anterior tibial load and internal rotational load of $10^{\circ}$ were applied on the final Computer aided design (CAD) model. And then stress patterns of each bundle were assessed using a finite element analysis. Results: In response to the 5 mm of anterior tibial load, the AM bundle showed increased stresses around the tibial and femoral attachment sites; especially in the anterior aspect of the bundle. In the PL bundle, the highest stress concentration was also noticed on the anterior aspect of the bundle. Under $10^{\circ}$ internal rotational load, the stress concentration was predominant around the anterior aspect of the tibial attachment site within the AM bundle. The PL bundle also showed highest stress concentration on the anterior aspect of the bundle. Conclusion: Although the stress patterns were not identical among the AM and PL bundle, there were common trends in the stress distribution. The stress concentration was predominant on the anterior aspect of both bundles in response to the anterior tibial load and rotatory load.

• Journal of Biomedical Engineering Research
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• v.31 no.3
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• pp.199-209
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• 2010

The locking compression plates-distal femur(LCP-DF) are being widely used for surgical management of the extra-articular complex fractures of the distal femur. They feature locking mechanism between the screws and the screw holes of the plate to provide stronger fixation force with less number of screws than conventional compression bone plate. However, their biomechanical efficacies are not fully understood, especially regarding the number of the screws inserted and their optimal configurations. In this study, we investigated effects of various screw configurations in the shaft and the condylar regions of the femur in relation to structural stability of LCP-DF system. For this purpose, a baseline 3-D finite element (FE) model of the femur was constructed from CT-scan images of a normal healthy male and was validated. The extra-articular complex fracture of the distal femur was made with a 4-cm defect. Surgical reduction with LCP-DF and bone screws were added laterally. To simulate various cases of post-op screw configurations, screws were inserted in the shaft (3~5 screws) and the condylar (4~6 screws) regions. Particular attention was paid at the shaft region where screws were inserted either in clustered or evenly-spaced fashion. Tied-contact conditions were assigned at the bone screws-plate whereas general contact condition was assumed at the interfaces between LCP-DF and bone screws. Axial compressive load of 1,610N(2.3 BW) was applied on the femoral head to reflect joint reaction force. An average of 5% increase in stiffness was found with increase in screw numbers (from 4 to 6) in the condylar region, as compared to negligible increase (less than 1%) at the shaft regardless of the number of screws inserted or its distribution, whether clustered or evenly-spaced. At the condylar region, screw insertion at the holes near the fracture interface and posterior locations contributed greater increase in stiffness (9~13%) than any other locations. Our results suggested that the screw insertion at the condylar region can be more effective than at the shaft during surgical treatment of fracture of the distal femur with LCP-DF. In addition, screw insertion at the holes close to the fracture interface should be accompanied to ensure better fracture healing.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.3C
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• pp.143-155
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• 2006

SPT-Uphole tomography method was introduced for the evaluation of near subsurface shear wave velocity (Vs) distribution map. In SPT-Uphole method, SPT (Standard Penetration Test) which is common in geotechnical site investigation was used as a source and several surface geophones in line were used as receivers. Vs distribution map which is the triangular shape around the boring point can be developed by tomography inversion. To obtain the exact travel time information of shear wave component, a procedure using the magnitude summation of vertical and horizontal components was used based on the evaluation of particle motion at the surface. It was verified that proposed method could give reliable Vs distribution map through the numerical study using the FEM (Finite Element Method) model. Finally, SPT-Uphole tomography method was performed at the weathered soil site where several boring data with SPT-N values are available, and the feasibility of proposed method was verified in the field.

• Journal of Biomedical Engineering Research
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• v.24 no.5
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• pp.401-410
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• 2003

This study investigates the biomechanical efficacies of various cement augmentation techniques with or without pressurization for varying degrees of osteoporotic femur. For this study, a biomechanical analysis using a finite element method (FEM) was undertaken to evaluate surgical procedures, Simulated models include the non-cemented(i.e., hip screw only, Type I), the cement-augmented(Type II), and the cemented augmented with pressurization(Type III) models. To simulate the fracture plane and other interfacial regions, 3-D contact elements were used with appropriate friction coefficients. Material properties of the cancellous bone were varied to accommodate varying degrees of osteoporosis(Singh indices, II∼V). For each model. the following items were analyzed to investigate the effect surgical procedures in relation to osteoporosis of varying degrees : (a) von Mises stress distribution within the femoral head in terms of volumetric percentages. (b) Peak von Mises stress(PVMS) within the femoral head and the surgical constructs. (c) Maximum von Mises strain(MVMS) within the femoral head, (d) micromotions at the fracture plane and at the interfacial region between surgical construct and surrounding bone. Type III showed the lowest PVMS and MVMS at the cancellous bone near the bone-construct interface regardless of bone densities. an indication of its least likelihood of construct loosening due to failure of the host bone. Particularly, its efficacy was more prominent when the bone density level was low. Micromotions at the interfacial surgical construct was lowest in Type III. followed by Type I and Type II. They were about 15-20% of other types. which suggested that pressurization was most effective in limiting the interfacial motion. Our results demonstrated the cement augmentation with hip screw could be more effective when used with pressurization technique for the treatment of intertrochanteric fractures. For patients with low bone density. its effectiveness can be more pronounced in limiting construct loosening and promoting bone union.