• Earthquakes and Structures
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• v.24 no.1
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• pp.53-64
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• 2023

Earth fissures with several kilometers will inevitably approach or cross the metro line, significantly threatening the safety of the underground structure in the earth fissure site. However, the influence of the earth fissure site's amplification effect on the metro station's dynamic response is still unclear. A representative earth fissure in Xi'an was taken as an example to establish a numerical model of a metro station in the earth fissure site. The dynamic response characteristics of the metro stations at different distances from the earth fissure under various seismic waves were calculated. The results show that the existence of the earth fissure significantly amplifies the dynamic response of the nearby underground structures. The responses of the axial force, shear force, bending moment, normal stress, horizontal displacement, inter-story drift, and relative slip of the metro station were all amplified within a specific influence range. The amplification effect increases with the seismic wave intensity. The amplification effect caused by the earth fissure has relatively weak impacts on the axial shear, shear force, bending movement, normal stress, and horizontal movement; slightly larger impacts on the inter-story drift and acceleration; and a significant impact on the relative slip. The influence ranges of the axial force and normal stress are approximately 20 m. The influence ranges of the acceleration and inter-story drift can reach 30 m. Therefore, the seismic fortification level of the underground structure in the earth fissure site needs to be improved.

• Geomechanics and Engineering
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• v.17 no.3
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• pp.253-259
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• 2019

Concrete-to-concrete bedding planes (CCBP) are observed from time to time due to the multistep hardening process of the concrete materials. In this paper, a series of direct/cyclic shear tests are performed on CCBP under static and dynamic normal load conditions to study the frictional behavior effect by the shear velocities, normal impact frequencies, horizontal shear frequencies, normal impact force amplitudes, horizontal shear displacement amplitudes and normal load levels. According to the experimental results, apparent friction coefficient k ($k=F_{Shear}/F_{Normal}$) shows different patterns under static and dynamic load conditions at the stable shear stage. k is nearly constant in direct shear tests under constant normal load conditions (DCNL), while it is cyclically changing with nearly constant peak value and valley value for the direct shear tests under dynamic normal load conditions (DDNL), where k increases with decreasing normal force and decreases with increasing normal force. Shear velocity has little influence on peak values of k for the DCNL tests, but increasing shear velocity leads to increasing valley values of k for DDNL tests. It is also found that, the valley values of k ascend with decreasing impact normal force amplitude in DDNL tests. The changing pattern of k for the cyclic shear tests under constant and dynamic normal load conditions (CCNL and CDNL tests) are similar, but the peak value of k is smaller in CDNL tests than that in CCNL tests. Normal load levels, shear displacement amplitudes, vertical impact frequencies, horizontal shear frequencies and normal impact force amplitudes have little influence on the changing pattern of k for the cyclic shear tests. The tests of this study provide useful data in understanding the frictional behavior of the CCBP under distinct loadings, and these findings are very important for analyzing the stability of the jointed geotechnical structures under complicated in situ stress conditions.

• Journal of the Korean Wood Science and Technology
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• v.39 no.5
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• pp.429-436
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• 2011

The selected physical and mechanical properties of non-certificated LVL circulated in domestic lumber market were investigated and compared to relevant standards. The tested LVL passed the moisture content and the soaking delamination rate limit as per domestic (KS) and Japanese standard (JAS). The evaluated mechanical properties were flatwise/edgewise bending strength, modulus of elasticity (MOE), horizontal shear and compressive strength. The 30 mm-thick LVL showed significantly higher bending strength than that of the 25 mm-thick LVL. The modulus of elasticity (MOE) showed same tendency in the results of bending strength. The edgewise bending strength and MOE were higher than that of flatwise bending strength and MOE. The horizontal shear strength values were also showed similar results to bending strength values. The tested results were compared each other and each products were graded according to JAS 701 grade specification. The failure mode of LVL in bending test showed the similar failure mode of solidwood that failed in a simple tension manner (splintery tension). The glue line failure was severe in 25 mm-thick specimens due to concentration of shear stress in layer discontinuity containing small voids and starved glue lines. In horizontal shear strength test, failure mode of LVL showed the typical horizontal shear failure. Compressive specimens failed with fiber crushing in company with apparent delamination that splitted along the length of the specimens. From the results, the complete bonding between lamination and consistency in thin veneer layer were considered as a critical factor in the mechanical properties of LVL. Moreover, the standard test procedure and specification for non-certificated LVL should be required to check the performance of uncertificated materials.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.1C
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• pp.33-39
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• 2009

Vertical soil stress near a pile subjected to negative skin friction (NSF) may be reduced due to shear transfer at the pile-soil interface. A three-dimensional finite difference analysis has been performed to clarify the influence of vertical and horizontal stress reductions on the pile behavour. In addition, a simple equation has been proposed to estimate vertical stress reduction of the soil near the pile. The vertical and horizontal stresses are reduced by substantial amount compared to corresponding stress components at the Greenfield condition. The horizontal extent of vertical stress reduction of the soil near the pile is rather limited to about up to 4-8 D, where D is the pile diameter. The findings from the current research indicate that widely used $\beta$-method may result in over-estimation of dragload (compressive force on piles due to NSF) and hence stress reduction needs to be incorporated in the original equation.

• Proceeding of KASS Symposium
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• 2006.05a
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• pp.110-117
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• 2006

This study presents an effective stiffness-based optimal technique to consider floor rigid diaphragm action and a technique to evaluate the structural behavior characteristics and efficiency for tall shear wall outrigger system subject to horizontal loads. To this end, isoparametric plane stress element with rotational stiffness is used for shear wall element and stiffness gradient is calculated. Also, the approximation concept to solve effectively the large scaled problems, member grouping technique and resizing technique are considered. To verify the effectiveness and usefulness of this technique, the efficient evaluation method for three types of 50 story model with core and outrigger system is presented.

• Journal of Korean Association for Spatial Structures
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• v.24 no.1
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• pp.37-45
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• 2024

Steel plate shear walls (SPSWs) have been recognized as an effective seismic-force resisting systems due to their excellent strength and stiffness characteristics. The infill steel plate in a SPSW is constrained by a boundary frame consisting of vertical and horizontal structural members. The main purpose of this study was to investigate deformation modes and hysteretic characteristics of steel plate shear walls (SPSWs) to consider the effects of their aspect ratios and width-to-thicness ratios. The finite element model (FEM) was establish in order to simulate cyclic responses of SPSWs which have the two-side clamped boundary condition and made of conventional steel grade. The stress distribution obtained from the FEA results demonstrated that the principal stresses on steel plate with large thickness-to-width ratio were more uniformly distributed along its horizontal cross section due to the formation of multiple struts.

• Earthquakes and Structures
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• v.23 no.3
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• pp.297-313
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• 2022

Composite steel plate shear wall (CSPSW) is a relatively novel structural system proposed to improve the performance of steel plate shear walls by adding one or two layers of concrete walls to the infill plate. In addition, the buckling of the infill steel plate has a significant negative effect on the shear strength and energy dissipation capacity of the overall systems. Accordingly, in this study, using the finite element (FE) method, the performance and behavior of composite steel shear walls using T-shaped stiffeners to prevent buckling of the infill steel plate and increase the capacity of CSPSW systems have been investigated. In this paper, after modeling composite steel plate shear walls with and without steel plates with finite element methods and calibration the models with experimental results, effects of parameters such as several stiffeners, vertical, horizontal, diagonal, and a combination of T-shaped stiffeners located in the composite wall have been investigated on the ultimate capacity, web-plate buckling, von-Mises stress, and failure modes. The results showed that the arrangement of stiffeners has no significant effect on the capacity and performance of the CSPSW so that the use of vertical or horizontal stiffeners did not have a significant effect on the capacity and performance of the CSPSW. On the other hand, the use of diagonal hardeners has potentially affected the performance of CSPSWs, increasing the capacity of steel shear walls by up to 25%.

• Journal of the Korea Concrete Institute
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• v.18 no.3 s.93
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• pp.425-429
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• 2006

Horizontal cracks at the mid-depth of concrete slabs were observed at a section of the continuously reinforced concrete pavement(CRCP) structures on the Korea Highway Corporation's Test Road. To investigate the existence and the extent of horizontal cracks in the concrete slab, a number of cores were taken from the section of CRCP. To identify the causes of horizontal cracks, numerical analyses were conducted. Several variables relative to design, material, and environment were considered in the studies to evaluate possible causes of horizontal cracking. A numerical model of CRCP was developed using the finite element discretization, and the shear and normal tensile stress distributions in CRCP were investigated with the model. Numerical analysis results show that the maximum shear and normal tensile stresses develop near the depth of steel bars at transverse cracks. If those maximum stresses reach the strength of concrete, horizontal cracks occur. The maximum stresses become higher as the environmental loads, coefficient of thermal expansion of concrete, and elastic modulus of concrete increase.

• Restorative Dentistry and Endodontics
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• v.19 no.2
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• pp.549-567
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• 1994

Restoration of severly damaged teeth after endodontic treatment had been an interest to many dentists, and it is a fact that there have been lots of studies about it. In these days, although we have used Para-Post, pins, threaded steel post, cast gold post and core, and so on, as a method of restoration frequently, it has been in controversy with the influence of them on the teeth and surrounding periodontal tissue. In this study, we assume that the crown of the upper incisor have severly damaged, so, after the root canal therapy, 4 types of restoration had been carried out; 1) coronal-radicular amalgam restoration, 2) after setting up the Para-Post, restore with composite resin core only, 3) after setting up the Para-Post; restore with amalgam core, then cover with the PPM crown 4) after setting up the Para-Post, restore with composite core, then cover with the PPM crown. After restoration, in order to observe the concentration of stress at internal portion of the teeth and the sourrounding periodontal tissue, developing a 2-dimensional finite element model of labiopalatal section, then loading forces from 3 direction - direction of 45 degrees from lingual side near the incisal edge, horizontal direction from labial height of contour, vertical direction at the incisal edge-were applied. The analyzed results were as follows: 1. Stress of the normal central incisor was concentrated on the dentin aroundpulp chamber, labiocervical portion of a tooth and root apex, but with the alveolar bone, in the case of load from the direction of 45 degrees from lingual side near the incisal edge showed remarkable concentration of stress: 2. Coronal-radicular amalgam technique -showed less concentration of stress on the root and surrounding periodontal tissue than the restoration with the Para-Post. 3. The von Mises equivalent stress on the Para-Post showed maximum value at root-core junction rather than both ends and model with PPM restoration with amalgam core showed the least concentration of stress. Only the force from horizontal direction showed large shear stress on internal portion of the root, root apex and alveolar bone. 4. PPM crown with composite core rarely showed the concentration of stress on root and periodontal tissue. 5. As for alveolar bone, remarkable shear stress was concentrated on labial and palatal side by horizontal load.

• Journal of Welding and Joining
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• v.15 no.4
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• pp.143-153
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• 1997

In this study, bending test was performed on the real-scale, built-up beam test model fabricated by the $CO_2$ arc spot welding to evaluate the applicability of the welding method to the production of the stiffened plate in car-carrying ship. The built-up beam models which were fixed at both ends in longitudinal direction or simply supported to the rigid foundation, depending on the restraint condition of the corresponding car decks considered, were subjected to simulated design vehicle loads or concentrated point loads. During the test, the central deflection and the longitudinal bending stresses were measured from several points on the longitudinal flange face to predict the section properties of the built-up beams. The longitudinal bending stress on each spot weld were also measured to calculate the average horizontal shear force subjected to spot welds. Test results revealed that the shear strength of spot welds with their current weld nugget size and welding pitch was adequate enough to withstand the horizontal shear forces under the design vehicle loads. Although the built-up beam fabricated by the arc spot welding was a discontinuous beam, its mechanical behavior was well explained by the continuous beam theory using the effective breadth of plate. Based on test results, the criterion for the size of spot weld of which the average shear stress might meet the allowable stress requirement of AWS Code could be established.