Analisis Perbandingan Kapasitas Balok Komposit Baja-Beton dengan Steel Headed Stud dan UNP Stud

Penghubung geser atau stud memiliki peranan penting dalam menghasilkan perilaku komposit baja-beton. Terdapat dua jenis stud yang direkomendasikan, yaitu steel headed stud atau paku berkepala dan UNP stud atau kanal. Penelitian ini menganalisis perbandingan kapasitas balok komposit baja-beton dengan penghubung geser jenis steel headed stud dan UNP stud. Pemodelan menggunakan program elemen hingga dipilih sebagai metode dalam analisis perilaku non-linier. Luas permukaan kedua jenis penghubung geser dibuat sama sehingga kuat nominal, jumlah, dan jarak pemasangan penghubung geser pun juga akan sama untuk kedua jenis pemodelan ini. Kapasitas yang ditinjau meliputi tegangan pada balok baja WF, tegangan pelat beton, tegangan pada stud, konsentrasi tegangan pada balok baja dan pelat beton, serta defleksi pada balok komposit. Sebelum melakukan pemodelan dengan program elemen hingga, proses desain sesuai SNI 1727:2015 dilakukan terlebih dahulu untuk menentukan dimensi struktur yang akan digunakan. Validasi diperlukan untuk melihat tingkat keakuratan pemodelan yang dilakukan. Metode validasi dilakukan dengan membandingkan nilai tegangan lentur pada serat bagian bawah dan atas balok komposit baja-beton. Persentase pemodelan mencapai 86,95% untuk model steel headed stud dan 87,4% untuk UNP stud. Hasil pemodelan menunjukkan bahwa balok komposit dengan UNP stud memilik kapasitas yang lebih baik karena menghasilkan nilai tegangan-tegangan dan defleksi yang lebih kecil. Tegangan lentur balok baja UNP stud dan steel headed stud adalah 19,129 MPa dan 19,556 MPa (perbedaan 2,18 %). Tegangagan lentur pelat beton UNP stud dan steel headed stud adalah 1,21 MPa dan 1,194 MPa (perbedaan 1,34 %). Defleksi balok komposit dengan UNP stud dan steel headed stud adalah 0.478 mm dan 0,435 mm (perbedaan 8,99 %)

Headed stud shear connectors in solid slabs and in slabs with wide ribbed metal deck

This thesis summarizes the results of an experimental investigation of the behaviour of headed stud connectors in push-out specimens with headed studs embedded in solid slabs and in slabs with wide ribbed metal deck oriented parallel to the beam. The experimental investigation involved the testing of 104 push-out specimens and was conducted in three phases. The first phase involved a study of the effects of transverse stud spacing on the shear strength of headed studs in push-out specimens with solid slabs and those with wide ribbed metal decks. The objectives of the second phase were to conduct a parametric study of the behaviour of headed studs in push-out specimens with solid slabs and to propose new equations for predicting the ultimate stud capacity for this case. A similar study involving specimens with wide ribbed metal decks formed the third phase. For specimens with 150 mm solid slabs, there is an increase in the shear capacity of headed studs when the transverse stud spacing is increased from 3 times the stud diameter to 4 times the stud diameter (d) beyond which the strength-transverse stud spacing curve forms a plateau. The percentage increase in stud shear capacity is higher when failure is concrete related than when shank shear of studs is the mode of failure. For specimens featuring 150 mm slabs with wide ribbed metal decks, the shear capacity of headed studs attains a maximum value when the transverse spacing is 3d and decreases when the transverse spacing is increased to 4d beyond which the strength-transverse stud spacing curve forms a plateau. For specimens with solid slabs, there is an increase in the stud shear capacity with the increase in longitudinal stud spacing, up to a transition point, beyond which the strength-longitudinal stud spacing curve forms a plateau. This transition point occurs at a longitudinal stud spacing of approximately 5d when the concrete compressive strength is approximately 25 MPa and at 4.5d when the compressive strength of concrete is over approximately 30 MPa. In general, the failure modes of specimens with closely spaced studs was concrete related. When the stud spacing was increased, the failure mode changed to shank shear of studs. The effect of concrete compressive strength on the shear capacity of studs was found to vary approximately in proportion to the square root of the increase in the compressive strength of concrete. The effect of transverse reinforcement is more pronounced for specimens with concrete related failure than those with shank shear failure of studs. A new equation proposed by the author for predicting the shear capacity of headed studs in solid slabs provides much better correlation to test results than those obtained using CSA and Eurocode 4 provisions. Unlike these code provisions, the proposed equation takes into account the effects of longitudinal and transverse stud spacing, and transverse reinforcement. For the specimens with wide ribbed metal deck, the relationship between longitudinal stud spacing and stud capacity was nonlinear and the strength-longitudinal stud spacing curve did not attain a plateau within the range of longitudinal stud spacings considered. Within the range of the flute widths considered, the deck geometry does not appear to have any significant influence on the stud capacity for specimens with 150 mm slabs as well as for those with 103 mm slabs. The most common failure mode for the specimens with wide ribbed metal decks was concrete shear plane failure. A new equation proposed by the author for predicting the shear capacity of studs in wide ribbed metal deck provides better correlation to test results than those obtained using CSA and Eurocode provisions

Innovative Steel Pennon Plate-Headed Stud of Shear Connectors for Composite Structures

This study proposes an innovative pennon plate-headed stud of shear connectors. The proposed stud consists of two triangular-shaped steel plates on both sides of the headed stud; it is expected to increase the shear capacity of a steel-concrete composite connection. Nonlinear finite element analysis is carried out using ABAQUS to analyze the response of 54 models of PPH studs. A full factorial design and the analysis of variance are employed in the design of experiments (DOE). The impacts of factors and their interactions, such as the thickness and height of the pennon plates, concrete grades, and stud diameters, are captured by using 33 × 21 DOE with a 5% significance level. The results show that the ultimate shear resistance is increased apparently. Additionally, the concrete grade and stud diameter significantly influence the capacity of the connection. Moreover, connection slip is greatly affected by concrete grade, the height of the plate, and the interaction between plate thickness and height

Resistance of stud shear connectors in composite beams using profiled steel sheeting

In composite beam design, headed stud shear connectors are commonly used to transfer longitudinal shear forces across the steel-concrete interface. This paper describes the structural performance of shear connection in composite beams with profiled steel sheeting. An accurate and efficient nonlinear Finite Element (FE) model was developed to study the behavior of headed stud shear connectors welded through the deck. The concrete slab considered in this article uses profiled steel sheeting with ribs perpendicular to the longitudinal axis of the steel beam. The material nonlinearities were included in the FE model. The concrete was modeled considering a damaged plasticity model available in ABAQUS software. The results obtained from FE analysis were verified against experimental results. A parametric study was conducted to observe the effects of changing of both the stud position inside the rib of profiled steel sheeting and the concrete strength on the resistance of the stud shear connector. The shear resistance of stud connectors obtained from the FE analysis and many experimental push-out tests whose results are available in the literature were used as a database to compare with design shear resistance calculated using AISC-LRFD and Eurocode 4. It is found that the shear resistance of stud connectors, obtained from the design rules specified in these codes, in some cases is greatly underestimated, and in other cases significantly overestimated.Peer ReviewedPostprint (author's final draft

Shear Capacity of Headed Studs in Steel-Concrete Structures: Analytical Prediction via Soft Computing

Headed studs are commonly used as shear connectors to transfer longitudinal shear force at the interface between steel and concrete in composite structures (e.g., bridge decks). Code-based equations for predicting the shear capacity of headed studs are summarized. An artificial neural network (ANN)-based analytical model is proposed to estimate the shear capacity of headed steel studs. 234 push-out test results from previous published research were collected into a database in order to feed the simulated ANNs. Three parameters were identified as input variables for the prediction of the headed stud shear force at failure, namely the steel stud tensile strength and diameter, and the concrete (cylinder) compressive strength. The proposed ANN-based analytical model yielded, for all collected data, maximum and mean relative errors of 3.3 % and 0.6 %, respectively. Moreover, it was illustrated that, for that data, the neural network approach clearly outperforms the existing code-based equations, which yield mean errors greater than 13 %

Design value of a headed stud shear resistance in composite steel – concrete beams – probability-based approach to evaluation

[EN] Conventional standard procedure used to determine the design value of a headed stud shear resistance in composite steel-concrete beams is very simple but, in fact, mathematically incorrect, particularly in the case when such connector is automatically welded and when it is working in a solid slab. According to this approach the considered value is specified as a minimum of two separate design values. One of them is related to the resistance of the stud itself while the other is associated with the failure of the surrounding concrete. In the paper presented by the authors a new algorithm which allow to evaluate this value is recommended and discussed in detail. It seems to be more accurate because it is based on the fully probabilistic inference. In such approach a new random variable is introduced, being a minimum of two other, statistically independent, random variables. Analogously as it is in the concept previously mentioned, the first random variable quantifies now the steel stud shear resistance whereas the second one – the resistance of the adjacent concrete. Consequently, the sought design value is determined as a suitable quantile of this new random variable, characterized by log-normal probability distribution. It is shown that the design value of a headed stud shear resistance, calculated in this manner, strongly depends on the variability of strength parameters, relating both to the steel of which the connecting stud is made and to the concrete of the slab. In addition, it is found that in the case when the variability of concrete strength is too high, the safety factor recommended to use in European standards is not able to provide the required safety level, acceptable by the building users. The considerations presented in the article are illustrated by a detailed computational example.Maslak, M.; Domanski, T. (2018). Design value of a headed stud shear resistance in composite steel – concrete beams – probability-based approach to evaluation. En Proceedings of the 12th International Conference on Advances in Steel-Concrete Composite Structures. ASCCS 2018. Editorial Universitat Politècnica de València. 237-242. https://doi.org/10.4995/ASCCS2018.2018.6950OCS23724

Post-fire Behaviour of Innovative Shear Connection for Steel-Concrete Composite Structures

YesSteel-concrete composite structures are commonly used in buildings and bridges because it takes advantage of tensile strength of steel and compressive strength of concrete. The two components are often secured by shear connectors such as headed studs to prevent slippage and to maintain composite action. In spite of its popularity, very little research was conducted on steel-concrete composites particularly on headed stud shear connectors in regards to its post-fire behaviour. This research investigates the post-fire behaviour of innovative shear connectors for composite steel and concrete. Three type of connectors were investigated. They are headed stud shear connectors, Blind Bolt 1 and Blind Bolt 2 blind bolts. Push-out test experimental studies were conducted to look at the behaviour and failure modes for each connector. Eighteen push tests were conducted according to Eurocode 4. The push test specimens were tested under ambient temperatures and post fire condition of 200˚C, 400˚C and 600˚C. The results in ambient temperature are used to derive the residual strength of shear connectors after exposing to fire. Findings from this research will provide fundamental background in designing steel-concrete composites where there is danger of fire exposure

On the Fatigue of Headed Shear Studs in Steel-Concrete Composite Bridge Girders

Shear connectors are commonly used in steel bridges to join the concrete deck and steel superstructure, providing a mechanism for shear transfer across the steel-concrete interface. The most common shear connector is the headed shear stud. In the current AASHTO LRFD Bridge Specifications on composite design, shear stud fatigue often governs over static strength, and a large number of shear connectors often result. This dissertation investigates headed shear stud fatigue capacities and demands, and provides insight into conservancies in existing design specifications through examination of existing high-traffic bridge performance. To investigate stud capacity, a total of six high-cycle fatigue tests are conducted on stud pushout specimens at low stress ranges and combined with existing experimental data to develop probabilistic S-N fatigue capacity curves. Results from composite push-out specimens tested at stress ranges between 4.4 and 8.7 ksi suggest a fatigue limit of 6.5 ksi, which is near the existing limit of 7 ksi. Recommendations for modification of the existing AASHTO finite-life shear stud S-N fatigue capacity curve are proposed. In addition to experimental testing, a finite element parametric study considers the effects of stud pitch, girder depth, and girder span on shear flow demands. Results from the parametric study indicate that the shear forces within stud clusters are not captured by current AASHTO shear flow demand estimations. A new design method and updated formulation for predicting stud demands are presented. To examine high-traffic bridge performance, residual fatigue life is investigated by further fatigue testing, as well as magnetic particle inspection and dye penetrant testing on two existing bridges. The lack of discovered fatigue cracks within the studs of the bridges investigated suggests that the shear stress range estimation in AASHTO specification is higher than what is actually experienced. This discrepancy is likely due to shear transfer through adhesion and friction, which are not considered in AASHTO design calculations. Fatigue tests from sections of the decommissioned bridge exceeded the design life expectancy of approximately 850,000 cycles (at 11.6 ksi) by over 2,500,000 cycles. This evidence further indicates that stud fatigue is an unlikely failure mode during service loading

Finite element modelling of shear connection for steel-concrete composite girders

The main objective of this thesis is to develop effective 3-dimensional finite element models to trace the behaviour of headed stud shear connectors in composite girders with solid slabs and precast hollow core slabs. The finite element package ABAQUS was used to conduct the analysis. Push-off tests with both types of slabs were simulated taking into consideration all material nonlinearities of the components. The models are able to predict the headed shear stud capacity, the load-slip characteristic of the shear connection and modes of failure. The results obtained show good agreement with specified data from Codes of practice and results of available numerical and experimental literature. Parametric studies were carried out using both models to investigate the effects of the change in different parameters on the behaviour of shear connections. Full-scale push-off tests with solid and precast hollow core slabs have been carried out to verify the finite element models. The shear connection capacity, load-slip curves and modes of failure were detected from experimental investigation. Both numerical and experimental results were compared and good agreement has been achieved. The comparison has shown that the model is able to predict accurately the behaviour of headed studs in composite girders with both types of slabs. The non-linear load-slip characteristics of the headed shear stud connector obtained from FE models of push-off tests were used in modelling the structural behaviour of composite steel-solid slab concrete and steel-precast hollow core slab girders. A finite element model has been developed for the analysis of each type. The models took into account the non-linear behaviour of concrete slab, steel beam and shear connectors. The accuracy and efficiency of the models have been demonstrated by comparing finite element results with available published experimental and numerical research. An effective parametric study for the evaluation of the effective width for steel-precast concrete slab composite girders is presented