• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2000.04a
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• pp.178-185
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• 2000

A set of tests were accomplished in order to get better insight of the basic material properties of masonry made of normal concrete brick and different type of mortar compositions. Three different types of test were performed. Masonry unit and prism were tested by compressive strength test, Masonry wallets were tested by compressive strength test. Masonry wallets were tested in diagonally under tension. A significant influence of different mortar compositions on compression strength of masonry prism was observed, The tests have shown that for diagonal compression three different mode of failure were possible : tension crack along the loaded diagonal sliding along a mortar joint and combined sliding and diagonal crack according to the adhesive strength of a mortar.

• Computers and Concrete
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• v.8 no.1
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• pp.59-70
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• 2011

A theoretical model known as the modified rotating-angle softened-truss model (MRA-STM), which is a modification of Rotating-Angle Softened-Truss Model and Modified Compression Field Theory, is presented for the analysis of reinforced concrete membranes in shear. As an application, shear strength and behaviour of reinforced concrete exterior beam-column joints are analysed using the MRA-STM combining with the deep beam analogy. The joints are considered as RC panels and subjected to vertical and horizontal shear stresses from adjacent columns and beams. The strut and truss actions in a beam-column joint are represented by the effective transverse compression stresses and a softened concrete truss in the proposed model. The theoretical predictions of shear strength of reinforced concrete exterior beam-column joints from the proposed model show good agreement with the experimental results.

• Steel and Composite Structures
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• v.34 no.6
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• pp.803-818
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• 2020

Semi-rigid connections with blind bolts could solve the difficulty that traditional high strength bolts were unavailable to splice a steel/composite beam to a closed section column. However, insufficient investigations have focused on the performance of semi-rigid connection to square concrete filled double-skin steel tubular (CFDST) columns. In this paper, a component model was developed to evaluate the mechanical behavior of semi-rigid composite connections to CFDST columns considering the stiffness and strength of column face in compression and column web in shear which were determined by the load transfer mechanism and superstition method. Then, experimental investigations on blind bolted composite joints to square CFDST columns were conducted to validate the accuracy of the component model. Dominant failure modes of the connections were analyzed and this type of joint behaved semi-rigid manner. More importantly, strain responses of CFDST column web and tubes verified that stiffness and strength of column face in compression and column web in shear significantly affected the connection mechanical behavior owing to the hollow part of the cross-section for CFDST column. The experimental and analytical results showed that the CFDST column to steel-concrete composite beam semi-rigid joints could be employed for the assembled structures in high intensity seismic regions.

• Steel and Composite Structures
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• v.23 no.1
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• pp.17-29
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• 2017

The seismic performance of steel beam to concrete-encased composite column with unsymmetrical steel section joints is investigated and reported within this paper. Experimental and analytical evaluation were conducted on a total of 8 specimens with T-shaped and L-shaped steel section under lateral cyclic loading and axial compression. The test parameters included concrete strength, stirrup ratio and axial compression ratio. The response of the specimens was presented in terms of their hysterisis loop behavior, stress distribution, joint shear strength, and performance degradation. The experiment indicated good structural behavior and good seismic performance. In addition, a three-dimensional nonlinear finite-element analysis simulating was conducted to simulate their seismic behaviors. The finite-element analysis incorporated both bond-slip relationship and crack interface interaction between steel and concrete. The results were also compared with the test data, and the analytical prediction of joint shear strength was satisfactory for both joints with T-shaped and L-shaped steel section columns. The steel beam to concrete-encased composite column with unsymmetrical steel section joints can develop stable hysteretic response and large energy absorption capacity by providing enough stirrups and decreased spacing of transverse ties in column.

• Tunnel and Underground Space
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• v.5 no.1
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• pp.1-10
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• 1995

The behavior of a jointed rock mass depends mainly on the geometrical and mechanical properties of joints. The failure mode of a rock mass and kinematics of rock blocks are governed by the orientation, spacing, and persistence of joints. The mechanical properties such as dilation angle, shear strength, maximum closure, strength of asperities and friction coeffiient play important roles on the stability and deformation of the rock mass. The normal and shear behaviour of a joint are coupled due to dilation, and the joint deformation depends also on the boundary conditions such as stiffness conditons. In this paper, the joint constitutive law including the dilatant behaviour of a joint is numerically modelled using the edge-to-edge contact logic in distinct element method. Also, presented is the method to quantify the input parameters used in the joint law. The results from uniaxial compression and direct shear tests using the numeical model of the single joint were compared to the analytic results from them. The boundary effect on the behaviour of a joint is verified by comparing the results of direct shear test under constant stress boundary condition with those under constant stiffness boundary condition. The numerical model developed is applied to a complex jointed rock mass to examine its performance and to evaluate the effect of joint dilation on tunnel stability.

• Geomechanics and Engineering
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• v.15 no.5
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• pp.1113-1124
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• 2018

Geological dynamic hazards during deep coal mining are caused by the failure of a composite system consisting of the rock and coal layers, whereas the joint in coal affects the stability of the composite system. In this paper, the compression test simulations for the rock-coal combined body with single joint in coal were conducted using $PFC^{2D}$ software and especially the effects of joint length and joint angle on strength and failure characteristics in a rock-coal combined body were analyzed. The joint length and joint angle exhibit a deterioration effect on the strength and affect the failure modes. The deterioration effect of joint length of L on the strength can be neglected with a tiny variation at ${\alpha}$ of $0^{\circ}$ or $90^{\circ}$ between the loading direction and joint direction. While, the deterioration effect of L on strength are relatively large at ${\alpha}$ between $30^{\circ}$ and $60^{\circ}$. And the peak stress and peak strain decrease with the increase of L. Additionally, the deterioration effect of ${\alpha}$ on the strength becomes larger with the increase of L. With the increase of ${\alpha}$, the peak stress and peak strain first decrease and then increase, presenting "V-shaped" curves. And the peak stress and peak strain at ${\alpha}$ of $45^{\circ}$ are the smallest. Moreover, the failure mainly occurs within the coal and no apparent failure is observed for rock. At ${\alpha}$ between $30^{\circ}$ and $60^{\circ}$, the secondary shear cracks generated in or close to the joint tips, cause the structural instability failure of the combined body. Therefore, their failure models present as a shear failure along partial joint plane direction and partially cutting across the coal body or a shear failure along the joint plane direction. However, at ${\alpha}$ of $60^{\circ}$ and L of 10 mm, the "V-shaped" shear cracks cutting across the coal body cause its final failure. While crack nucleations at ${\alpha}$ of $0^{\circ}$ or $90^{\circ}$ are randomly distributed in the coal, the failure mode shows a V-shaped shear failure cutting across the coal body.

• Steel and Composite Structures
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• v.34 no.1
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• pp.1-15
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• 2020

This paper presents experimental and numerical studies on effects of local damages on the in-plane elastic-plastic buckling and strength of a fixed parabolic steel tubular arch under a vertical load distributed uniformly over its span, which have not been reported in the literature hitherto. The in-plane structural behaviour and strength of ten specimens with different local damages are investigated experimentally. A finite element (FE) model for damaged steel tubular arches is established and is validated by the test results. The FE model is then used to conduct parametric studies on effects of the damage location, depth and length on the strength of steel arches. The experimental results and FE parametric studies show that effects of damages at the arch end on the strength of the arch are more significant than those of damages at other locations of the arch, and that effects of the damage depth on the strength of arches are most significant among those of the damage length. It is also found that the failure modes of a damaged steel tubular arch are much related to its initial geometric imperfections. The experimental results and extensive FE results show that when the effective cross-section considering local damages is used in calculating the modified slenderness of arches, the column bucking curve b in GB50017 or Eurocode3 can be used for assessing the remaining in-plane strength of locally damaged parabolic steel tubular arches under uniform compression. Furthermore, a useful interaction equation for assessing the remaining in-plane strength of damaged steel tubular arches that are subjected to the combined bending and axial compression is also proposed based on the validated FE models. It is shown that the proposed interaction equation can provide lower bound assessments for the remaining strength of damaged arches under in-plane general loading.

• International journal of steel structures
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• v.18 no.5
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• pp.1525-1540
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• 2018

A test rig with multi-functional purposes was specifically designed and manufactured to study the behavior of multi-planar welded tubular joints subjected to multi-planar concurrent axial loading. An experimental investigation was conducted on full-scale welded tubular joints with each consisting of one chord and eight braces under monotonic loading conditions. Two pairs or four representative specimens (two specimens for each joint type) were tested, in which each pair was reinforced with two kinds of different internal stiffeners at the intersections between the chords using welded rectangular hollow steel sections (RHSSs) and the braces using rolled circular hollow steel sections (CHSSs) and welded RHSSs. The effects of different internal stiffeners at the chord-brace intersection on the load capacity of joints under concurrent multi-planar axial compression/tension are discussed. The test results of joint strengths, failure modes, and load-stress curves are presented. Finite element analyses were performed to verify the experimental results. The study results show that the two different joint types with the internal stiffeners at the chord-brace intersection under axial compression/tension significantly increase the corresponding ultimate strength to far exceed the usual design strength. The load carrying capacity of welded tubular joints decreases with a higher degree of the manufacturing imperfection in individual braces at the tubular joints. Furthermore, the interaction effect of the concurrent axial loading applied at the welded tubular joint on member stress is apparent.

• Structural Engineering and Mechanics
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• v.13 no.3
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• pp.313-328
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• 2002

Based on the orthotropic hypoelasticity formulation, a triaxial constitutive model of concrete is proposed. To account for increasing ductility in high confinement of concrete, the ductility enhancement is considered using so called the strain enhancement factor. It is also developed a three-dimensional finite element model for reinforced concrete structural members based on the proposed constitutive law of concrete with the smeared crack approach. The concrete confinement effects due to the beam-column joint are investigated through numerical examples for simple beam and structural beam member. Concrete at compression fibers in the vicinity of beam-column joint behaves dominant not only by the uniaxial compressive state but also by the biaxial and triaxial compressive states. For the reason of the severe confinement of concrete in the beam-column joint, the flexural critical cross-section is observed at a small distance away from the beam-column joint. These observations should be utilized for the economic design when the concrete structural members are subjected to high confinement due to the influence of beam-column joint.

• The Journal of Korean Academy of Orthopedic Manual Physical Therapy
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• v.24 no.1
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• pp.77-83
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• 2018

Background: The purpose of this study is to investigate that effect of manual therapy using pelvic compression belt on hip abductor strength and balance ability in total knee replacement (TKR) patients. Methods: The subjects consisted of twenty two post-TKR patients. Participants were randomly assigned to a pelvic belt group (n=11) and a placebo group (n=11). All participants underwent manual therapy including range of motion exercise, soft tissue mobilization around knee joint, strengthening exercise (Quad set, SLR, sidelying hip abduction, standing hamstring curls, sitting knee extension, step-up, wall slide to $45^{\circ}$ knee flexion). Manual therapy was executed five times a week for 2 weeks. Outcome measures included hip abductor strength by using Biodex system 4 pro, anterior to posterior balance, medial to lateral balance, total balance by using Biodex balance system SD. Results: After the completion of the manual therapy, hip abductor strength was showed statistically significant improvements in pelvic belt group (p<.05). Anterior to posterior balance, medial to lateral balance, total balance were showed statistically significant improvements in pelvic belt group and placebo group (p<.05). There was a statistically significant difference between the two groups in hip abductor strength and there was no statistically significant difference in balance. Conclusions: This results suggest that manual therapy using pelvic compression belt has could be used for selective muscle activation of the hip abductor muscle and has useful in hip abductor strength and balance ability in TKR patients.