• Earthquakes and Structures
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• v.15 no.5
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• pp.499-511
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• 2018

This paper aims to investigate the seismic performance of the prestressed steel strips retrofitted RC beam-column joints. Two series of joint specimens were conducted under compression load and reversed cyclic loading through quasi-static tests. Based on the test results, the seismic behavior of the strengthened joints specimens in terms of the failure modes, hysteresis response, bearing capacity, ductility, stiffness degradation, energy dissipation performance and damage level were focused. Moreover, the effects of the amount of the prestressed steel strips and the axial compression ratio on seismic performance of retrofitted specimens were analyzed. It was shown that the prestressed steel strips retrofitting method could significantly improve the seismic behavior of the RC joint because of the large confinement provided by prestressed steel strips in beam-column joints. The decrease of the spacing and the increase of the layer number of the prestressed steel strips could result in a better seismic performance of the retrofitted joint specimens. Moreover, increasing the axial compression ration could enhance the peak load, stiffness and the energy performance of the joint specimens. Furthermore, by comparison with the specimens reinforced with CFRP sheets, the specimens reinforced with prestressed steel strips was slightly better in seismic performance and cost-saving in material and labor. Therefore, this prestressed steel strips retrofitting method is quite helpful to enhance the seismic behavior of the RC beam-column joints with reducing the cost and engineering time.

• Steel and Composite Structures
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• v.19 no.4
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• pp.861-876
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• 2015

Composite sections design consists on checking that the point defined by axial load and bending moment keeps included within the surface enclosed by the section interaction curve. Eurocode 4 suggests a method for tracing this diagram based on the plastic stress distribution method. However curves obtained according to this criterion overvalue concrete encased sections bearing capacity, especially when axial force comes with high bending moment values, so a correction factor is required. This article proposes a method for tracing this diagram based on the strain compatibility method. When stresses on the section are integrated by considering the Navier hypothesis, the use of the materials nonlinear constitutive equations provides curves much more adjusted to reality. This process requires the use of rather complex software which might reveal as too complex for practitioners. Preserving the same criteria of an elastic-plastic stress distribution, this article presents alternative expressions to obtain the failure internal forces in five significant points of the interaction diagram having considered five different positions of the neutral axis. These expressions are simply enough for their practical application. Concordance of curves traced strictly relying on these five points with those obtained by computer assisted stress integration considering the strain compatibility method and even with Eurocode 4 weighted curves will be presented for three different cross-sections and two different concrete strengths, revealing very good results.

• Steel and Composite Structures
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• v.18 no.6
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• pp.1423-1450
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• 2015

The paper presents the details and results of an experimental study on bolted end-plate joints of industrial type steel building frames. The investigated joints are commonly used in Lindab-Astron industrial buildings and are optimized for manufacturing, erection and durability. The aim of the research was to provide an experimental background for the design model development by studying load-bearing capacity of joints, bolt force distribution, and end-plate deformations. Because of the special joint details, (i.e., joints with four bolts in one bolt-row and HammerHead arrangements), the Eurocode 3 standardized component model had to be improved and extended. The experimental programme included six different end-plate and bolt arrangements and covered sixteen specimens. The steel grade of test specimens was S355, the bolt diameter M20, whereas the bolt grade was 8.8 and 10.9 for the two series. The end-plate thickness varied between 12 mm and 24 mm. The specimens were investigated under pure bending conditions using a four-point-bending test arrangement. In all tests the typical displacements and the bolt force distribution were measured. The end-plate plastic deformations were measured after the tests by an automatic measuring device. The measured data were presented and evaluated by the moment-bolt-row force and moment-distance from centre of compression diagrams and by the deformed end-plate surfaces. From the results the typical failure modes and the joint behaviour were specified and presented. Furthermore the influence of the end-plate thickness and the pretension of the bolts on the behaviour of bolted joints were analysed.

• Earthquakes and Structures
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• v.12 no.1
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• pp.79-89
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• 2017

As a new type of energy dissipation component with excellent mechanical performance, the Buckling-Retrained Braces (BRBs) were gradually applied in retrofitting and improving seismic performance of reinforced concrete structures in China. In order to investigate the seismic performance of reinforced concrete structures retrofitted with BRBs, quasi-static test of two single-bay and 3-story reinforced concrete frames specimens was conducted and introduced in this paper. Two 1/2 scaled specimens were designed to reflect real prototype structure. For comparison, one control specimen was designed without BRBs, and the other specimen was retrofitted with BRBs. And particularly, for the specimen retrofitted with BRBs, the BRBs were eccentric layout instead of usually concentric or x-shaped layout, aiming to be more suitable for large-span frames. In the test, the failure mode, carrying capacity, deformability, ductility and energy dissipation ability of both two specimens were investigated. Based on the test results of the measured hysterical curves, skeleton curves, the seismic performances such as bearing capacity, plastic deformability, energy dissipation ability and ductility of two specimens were fully studied. And from the test results, it was indicated that the specimen retrofitted with BRBs showed much better seismic performance than the control specimen without BRBs, and the BRBs could effectively improve the seismic performance of the reinforced concrete frame. For the specimen retrofitted with BRBs, the BRBs firstly yielded before the beam-ends and the column-ends, and an expected yielding process or yielding mechanism as well as good seismic performance was obtained. For the specimens without BRBs, though the beam-ends yielded prior to the column-ends, the seismic performance was much poor than that of the specimen with BRBs.

• Journal of Korean Tunnelling and Underground Space Association
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• v.14 no.3
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• pp.215-230
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• 2012

An experimental research on the possibility of using high-strength concrete with the design strength of 60 MPa and high-tension rebar with the yielding strength of 600 MPa instead of conventional reinforced concrete segment to reduce its production cost was performed. Full-scale bending tests on both conventional and high-strength reinforced concrete segments were carried out to compare their mechanical and structural behaviors of the segments under flexural action. From the experiments, it was shown that the failure load of high-strength reinforced concrete segment was approximately 30% higher than that of the conventional segment even though reinforcements in high-strength segment were reduced by 26%. The test result showed that the bearing capacity of high-strength segment highly increased by high-strength concrete and high-tension rebar. It also verified the high possibility of high-strength reinforced concrete segment as a technical alternative to reduce the production cost of segments in a shield tunnel.

• Journal of Veterinary Clinics
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• v.34 no.6
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• pp.463-466
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• 2017

A 3-year-old, 26 kg, castrated male Chow Chow was presented for assessment of weight-bearing lameness of the left hind limb. The patient had a history of triple pelvic osteotomy on the left side to correct hip dysplasia 2 years prior to his presentation of clinical signs and underwent total hip replacement on the right coxofemoral joint 1 year later. Upon physical examination, pain and crepitus were noted on the left hip joint during extension. Radiological examination revealed coxofemoral joint subluxation and moderate degenerative bone changes on the left hip joint and pelvic axis, which relates to acetabular angles that were changed after triple pelvic osteotomy (TPO). Preoperative computed tomography was used for 3-dimensional printing to establish an accurate surgical plan. The changed angles of the acetabulum after TPO were evaluated, and rehearsal surgery was performed using a 3-demensional printing bone model. Three months after the THR surgery, the function of the affected limb had improved, with no lameness. Complications, such as luxation and implant failure, were not observed until 6 months after the operation. Accurate evaluation of acetabulum angles and rehearsal surgery using a 3D-printed bone model is effective for total hip replacement after unsuccessful TPO.

• Journal of Korean Society of Steel Construction
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• v.24 no.2
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• pp.189-197
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• 2012

The cold-formed steel stud, which has been used as a load-bearing member of wall panels for steel houses, poses a significant problem in insulation due to heat bridging of the web. Therefore, some additional thermal insulating materials are required. In order to solve this problem, the cold-formed steel thermal stud with slits in the web was developed. However, estimating the structural strength of thermal studs is very difficult because of the arrangement of perforations. In this paper, an analytical and experimental research on thermal studs is described. Three types of studs with different length, pitch and arrangement of slits were tested to failure. A simple design approach was proposed based on the test results. The proposed method adopted the direct strength method, based on the elastic local and distortional buckling stress of plain studs with equivalent thickness in the web instead of thermal studs. The predictions using the proposed method were compared with test results for verification and the adequacy of the proposed method was confirmed.

• Geotechnical Engineering
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• v.3 no.1
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• pp.7-24
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• 1987

Preloading surcharge method along with vertical drains was adopted to improve the performance of a very soft marine clay deposit. The onshore deposit, located in the Ulsan Bay area, consists of a 2 to 10m thick, very soft, highly compressible marine clay layer developed just below. the sea water level. The initial undrained shear strength of the clay layer was about 0.6 ton/m2. But, the deposit was designed after treatment to support some auxiliary facilities for a new ilo refinery plant, requiring bearing capacities of 3.6 to 5.4 ton/m2 and maximum allowablee settlement of less than 7.5cm. A total of 35, 000 wick drains Ivas installed to expedite drainage during preloading, and surcharge loads of up to 5m above the original ground level were applied in a step-by-step loading sequence to prevent ground failure by excess surcharge loads. An extensive program of field instrumentation was implemented to monitor the behavior of the clay deposit. Measurers!ends included settlements, excess pore pressure and its dissipation, ground farmer level fluctuation, and lateral movement of the so(t clay layer under the preloads. This paper describes the design concepts, construction methods and control procedures used for improvement of the clay layer. It also presents the ground behavior measured during construction, rind comparisons with theoretical predictions.

• Journal of the Korean Geotechnical Society
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• v.16 no.4
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• pp.31-42
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• 2000

In this study, the stability of group piles installed in deep sea to the seaquake was studied by performing the calibration chamber model tests for open-ended pipe piles, grouted piles under soil plug and close-ended piles installed in the simulated deep sea. For each case (a single pile, 2-pile and 4-pile groups), series of seaquake tests were performed. While, during the simulated seaquake, the compressive capacity of the single open-ended pile depended on pile penetration depth(=7m), were found to be stable. But, a single grouted pile with penetration depth of 13m kept "mobility" state, the one with penetration depth of 20m was stable and grouted pile groups with penetration depth of 7m were stable regardless of pile penetration depth. By grouting soil plug of open-ended piles and soil under the pile toe of open-ended pipe piles installed in the deep sea, failure of soil plugging was prevented. Thus, close-ended piles were more stable than open-ended pile against the seaquake motionake motion.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.117-120
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• 2008

The bridge bearings are devices absorbing the displacements of the superstructure. KS F 4420 relative to the design of elastomeric bearings in Korea allows shear deformation up to 70% of total rubber height. For the elastomeric bearings to fulfill their shear function required in the design, the stability of allowable shear strain of elastomeric bearings relative to the shear failure should be guaranteed. Moreover considering the possibility that elastomeric bearings are applied to the seismic design together with isolation devices, elastomeric bearings is supposed to display higher shear performance. In this paper ultimate shear performance tests were performed. The measured ultimate shear strains were over 200%. Therefore an allowable shear strain provision becomes safe. But elastomeric bearings expected to show their performance in one united body reveled the separation of components near 200% shear strain. These separation in elastomeric bearing can cause unexpected impact or concentrated stress to bridge system considering to application of seismic design. Therefore provision relevant to separation problem is necessary.