• Steel and Composite Structures
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• 제18권6호
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• pp.1369-1389
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• 2015

In order to investigate the behaviour of lying multi-stud connectors in cable-pylon anchorage zone, twenty-four push-out tests are carried out with different stud numbers and diameters. The effect of concrete block width and tensile force on shear strength is investigated using the developed and verified finite element model. The results show that the shear strength of the lying multi-stud connectors is reduced in comparison with the lying single-stud connector. The reduction increases with the increasing of the number of studs in the vertical direction. The influence of the stud number on the strength reduction of the lying multi-stud connectors is decreased under combined shear and tension loads compared with under pure shear. Yet, due to multi-stud effect, they still can't be ignored. The concrete block width has a non-negligible effect on the shear strength of the lying multi-stud connectors and therefore should be chosen properly when designing push-out specimens. No obvious difference is observed between the strength reductions of the studs with 22 mm and 25 mm diameters. The shear strengths obtained from the tests are compared with those predicted by AASHTO LRFD and Eurocode 4. Eurocode 4 generally gives conservative predictions of the shear strength, while AASHTO LRFD overestimates the shear strength. In addition, the lying multi-stud connectors with the diameters of 22 m and 25 mm both exhibit adequate ductility according to Eurocode 4. An expression of load-slip curve is proposed for the lying multi-stud connectors and shows good agreement with the test results.

• Steel and Composite Structures
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• 제48권2호
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• pp.207-233
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• 2023

Steel-concrete composite box girder bridges are widely used in the construction of highway and railway bridges both domestically and abroad due to their advantages of being light weight and having a large spanning ability and very large torsional rigidity. Composite box girder bridges exhibit the effects of shear lag, restrained torsion, distortion and interface bidirectional slip under various loads during operation. As one of the most commonly used calculation tools in bridge engineering analysis, one-dimensional models offer the advantages of high calculation efficiency and strong stability. Currently, research on the one-dimensional model of composite beams mainly focuses on simulating interface longitudinal slip and the shear lag effect. There are relatively few studies on the one-dimensional model which can consider the effects of restrained torsion, distortion and interface transverse slip. Additionally, there are few studies on vehicle-bridge integrated systems where a one-dimensional model is used as a tool that only considers the calculations of natural frequency, mode and moving load conditions to study the dynamic response of composite beams. Some scholars have established a dynamic analysis model of a coupled composite beam bridge-train system, but where the composite beam is only simulated using a Euler beam or Timoshenko beam. As a result, it is impossible to comprehensively consider multiple complex force effects, such as shear lag, restrained torsion, distortion and interface bidirectional slip of composite beams. In this paper, a 27 DOF vehicle rigid body model is used to simulate train operation. A two-node 26 DOF finite beam element with composed box beams considering the effects of shear lag, restrained torsion, distortion and interface bidirectional slip is proposed. The dynamic analysis model of the coupled composite box girder bridge-train system is constructed based on the wheel-rail contact relationship of vertical close-fitting and lateral linear creeping slip. Furthermore, the accuracy of the dynamic analysis model is verified via the measured dynamic response data of a practical composite box girder bridge. Finally, the dynamic analysis model is applied in order to study the influence of various mechanical effects on the dynamic performance of the vehicle-bridge system.

• Steel and Composite Structures
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• 제50권3호
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• pp.319-336
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• 2024

Ultra-high-performance concrete (UHPC) has attracted increasing attention in prefabricated steel-concrete composite beams as achieving the onsite construction time savings and structural performance improvement. The inferior replacement and removal efficiency of conventional prefabricated steel-UHPC composite beams (PSUCBs) has thwarted its sustainable applications because of the widely used welded-connectors. Single embedded nut bolted shear connectors (SENBs) have recently introduced as an attempt to enhance demountability of PSUCBs. An in-depth exploration of the mechanical behavior of SENBs in UHPC is necessary to evidence feasibilities of corresponding PSUCBs. However, existing research has been limited to SENB arrangement impacts and lacked considerations on SENB geometric configuration counterparts. To this end, this paper performed twenty push-out tests and theoretical analyses on the shear performance and design recommendation of SENBs. Key test parameters comprised the diameter and grade of SENBs, degree and sequence of pretension, concrete casting method and connector type. Test results indicated that both diameters and grades of bolts exerted remarkable impacts on the SENB shear performance with respect to the shear and frictional responses. Also, there was limited influence of the bolt preload degrees on the shear capacity and ductility of SENBs, but non-negligible contributions to their corresponding frictional resistance and initial shear stiffness. Moreover, inverse pretension sequences or monolithic cast slabs presented slight improvements in the ultimate shear and slip capacity. Finally, design-oriented models with higher accuracy were introduced for predictions of the ultimate shear resistance and load-slip relationship of SENBs in PSUCBs.

• Structural Engineering and Mechanics
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• 제81권3호
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• pp.305-316
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• 2022

Externally bonded ultrahigh performance fiber-reinforced concrete (UHPFRC) is commonly used as a strengthening material for reinforced concrete (RC) structures. This study reports the results of an experimental program investigating the bonding behavior between concrete and prefabricated UHPFRC plates. The overall experimental program is consisting of five RC specimens, which are strengthened using the different lengths and widths of prefabricated UHPFRC plates. These specimens were analyzed using the pull-pull double-shear test. The performance of each strengthened specimen is presented, discussed and compared in terms of failure mode, maximum load, load-slip relationship, fracture energy and strain distribution. Specimen C-25-160-300 which bonded along the whole width of 160 mm recorded the highest maximum load (109.2 kN) among all the analysed specimens. Moreover, a 3D numerical finite element model (FEM) is proposed to simulate the bond behavior between concrete and UHPFRC plates. Moreover, this study reviews the analytical models that can predict the relationship between the maximum bond stress and slip for strengthened concrete elements. The proposed FEM is verified against the experimental program and then used to test 36 RC specimens strengthened with prefabricated UHPFRC plates with different concrete grades and UHPFRC plate widths. The obtained results together with the review of analytical models helped in the formation of a design equation for estimating the bond stress between concrete and prefabricated UHPFRC plates.

• Steel and Composite Structures
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• 제25권6호
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• pp.705-716
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• 2017

The objective of this study is to investigate the actual behavior of studs in structures under earthquake load through laboratory tests and numerical simulation. A test program including eighteen specimens was devised with consideration of different concrete strengths and stud diameters. Six of specimens were subjected to monotonically increasing loading while the others were subjected to cyclic loading. Mechanical behavior including the failure mechanism, load-slip relationship, stiffness degradation, energy dissipation and the damage accumulation was obtained from the test results. An accurate numerical model based on the ABAQUS software was developed and validated against the test results. The results obtained from the finite element (FE) model matched well with the experimental results. Furthermore, based on the experimental and numerical data, the design formulas for expressing the skeleton curve were proposed and the simplified hysteretic model of load versus displacement was then established. It is demonstrated that the proposed formulas and simplified hysteretic model have a good match with the test results.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1994년도 가을 학술발표회 논문집
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• pp.113-120
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• 1994

Large Concrete Panel Structures behave quite differently from frame or monolithic shear wall structures because of the weakness of Joint in stiffness and strength. The joint experiences large deformation such as shear-slip in vertical and horizontal joint and rocking and crushing in horizontal joint because of localized stress concentration, but the wall panels behave elastically under cyclic loads. In order to describe the nonlinear behavior of the joint in the analysis of PC structures, different analysis technique from that of RC structures is needed. In this paper, for analysis of large concrete panel subassemblage subjected to cyclic loads, the wall panels are idealized by elastic finite elements, and the joints by nonlinear spring elements with various load-deflection relationship. The analytical results are compared with the experimental results on the strength, stiffness, energy dissipation and lateral drift, and the effectiveness of this computer analysis modelling technique is checked.

• 콘크리트학회논문집
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• 제28권4호
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• pp.419-426
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• 2016

이 연구에서는 다양한 콘크리트를 갖는 전단계면에서의 전단마찰거동에 대한 횡보강근 및 압축응력의 영향을 평가하였다. 12개 직접전단실험체로부터 균열진전, 전단하중-상대 미끄러짐 관계, 균열발생시 전단응력, 최대전단내력 및 횡보강근의 전단저항력 등이 측정되었다. 실험결과 동일 전단하중에서 상대 미끄러짐 제어에 대한 횡보강근 배근형상 및 콘크리트 압축강도의 영향은 미미하였다. 작용 압축응력의 증가와 함께 콘크리트의 전단전달력을 증가하는 반면, 횡보강근의 전단전달력은 감소하였는데, 횡보강근의 전단저항은 배근형태에 의해 영향을 받지 않았다. AASHTO-LRFD, Mattock 및 Hwang and Yang의 모델은 콘크리트의 전단마찰내력을 과소평가하였다. 반면, Hwang and Yang의 모델은 실험결과와의 비교에 대한 평균과 표준편차 값이 각각 1.02과 0.23으로서 기존 모델에 비해 다양한 변수의 영향을 적절히 고려하면서 콘크리트의 전단마찰내력을 잘 예측하였다.

• 한국강구조학회 논문집
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• 제27권4호
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• pp.359-370
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• 2015

본 연구에서는 AFRP 스트립과 강재사이의 부착거동에 관한 실험적 연구를 수행하였다. 실험적 연구를 통해 AFRP 판과 강판사이의 계면부착거동을 관찰하고, 계면부착응력을 산정하는 것이 본 연구의 목표이다. 실험변수로는 부착길이와 AFRP의 두께를 선택하였으며, 18개의 일면전단시편 제작하여 실험을 수행하였다. 실험결과 부착길이와 AFRP 두께가 증가함에 따라 하중값을 증가하였으며, 부착길이와 AFRP 두께가 증가함에 따라 각각 63%, 86%의 하중값이 증가하였다. 끝으로 강재와 AFRP 사이의 부착응력-슬립관계를 산정하였다. 부착응력-슬립관계는 탄성선형거동을 보이고 있으며, 부착길이와 AFRP 두께는 부착응력과 파괴에너지에 영향을 덜 미치는 것으로 나타났다.

• Steel and Composite Structures
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• 제20권3호
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• pp.651-669
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• 2016

The behavior of shear connectors plays a significant role in maintaining the required strength of a composite beam in normal and hazardous conditions. Various types of shear connectors are available and being utilized in the construction industry according to their use. Channel connectors are a suitable replacement for conventional shear connectors. These connectors have been tested under different types of loading at ambient temperature; however, the behavior of these connectors at elevated temperatures has not been studied. This investigation proposes a numerical analysis approach to estimate the behavior of channel connectors under fire and compare it with the numerical analysis performed in headed stud and Perfobond shear connectors subjected to fire. This paper first reviews the mechanism of various types of shear connectors and then proposes a non-linear thermo-mechanical finite element (FE) model of channel shear connectors embedded in high-strength concrete (HSC) subjected to fire. Initially, an accurate nonlinear FE model of the specimens tested at ambient temperature was developed to investigate the strength of the channel-type connectors embedded in an HSC slab. The outcomes were verified with the experimental study performed on the testing of channel connectors at ambient temperature by Shariati et al. (2012). The FE model at ambient temperature was extended to identify the behavior of channel connectors subjected to fire. A comparative study is performed to evaluate the performance of channel connectors against headed stud and Perfobond shear connectors. The channel connectors were found to be a more economical and easy-to-apply alternative to conventional shear connectors.

• Steel and Composite Structures
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• 제36권1호
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• pp.103-118
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• 2020

The static behavior of grouped large-headed studs (d = 30 mm) embedded in ultra-high performance concrete (UHPC) was investigated by conducting push-out tests and numerical analysis. In the push-out test, no splitting cracks were found in the UHPC slab, and the shank failure control the shear capacity, indicating the large-headed stud matches well with the mechanical properties of UHPC. Besides, it is found that the shear resistance of the stud embedded in UHPC is 11.4% higher than that embedded in normal strength concrete, indicating that the shear resistance was improved. Regarding the numerical analysis, the parametric study was conducted to investigate the influence of the concrete strength, aspect ratio of stud, stud diameter, and the spacing of stud in the direction of shear force on the shear performance of the large-headed stud. It is found that the stud diameter and stud spacing have an obvious influence on the shear resistance. Based on the test and numerical analysis results, a formula was established to predict the load-slip relationship. The comparison indicates that the predicted results agree well with the test results. To accurately predict the shear resistance of the stud embedded in UHPC, a design equation for shear strength is proposed. The ratio of the calculation results to the test results is 0.99.