The influences of the number of concrete dowels to shear resistance based on push out tests

To reduce the depth of floor-beam structures and to save the cost of headed-shear studs, many types of shallow composite beam have been developed during the last few years. Among them, the shallow-hollow steel beam consists of web openings, infilled with in-situ concrete (named concrete dowel) has been increasingly focused recently. In this new kind of structure, this concrete dowel plays an important role as the principal shear connector. This article presents an investigation on the shear transferring mechanism and failure behavior of the trapezoid shape concrete dowel. An experimental campaign of static push-out tests has been conducted with variability in the number of web openings (WOs). The results indicate that the mechanical behavior of concrete dowel could be divided into crushing, compression, and tension zones and exhibits brittle behavior. The longitudinal shear resistance and specimen's stiffness are strongly affected by the number of considered WOs

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

<p>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 %.</p>

Numerical investigation on early age performance of ultra-high-performance concrete shear keys between an adjacent prestressed concrete box beams

Adjacent precast prestressed concrete box beam bridges have been widely utilized for decades and have shown satisfactory performance. However, significant issues regarding to the longitudinal shear key cracking have been noted by bridge maintenance personnel. The cracks are typically initiated at beam-shear key interfaces due to shrinkage and temperature and propagate due to applied load. Recently, ultra-high-performance concrete (UHPC) was employed in the shear keys with the anticipation to prevent joint cracking. Although the field-collected data at early age from bridge utilizing UHPC shear keys indicated promising performance, the results only reflected the early age joint behavior at locations which were instrumented during the field test. In the current study, a 3D finite element (FE) model was developed to calculate the early age stresses due to shrinkage and temperature. The results indicated that the UHPC material associated with a specific shear key configuration created a “self-locked” phenomenon that generated compression on the upper level shear key. The early age tensile stress during the first couple of days near the end of the joint was relatively small compared to the tensile strength of UHPC material. Although the interface had sufficient capacity to resist the early age stresses, it is still a critical component and needs to be designed with sufficient capacity.

Investigations on Interface Shear Fatigue of Semi-Precast Slabs with Lattice Girders

Due to their high cost efficiency and flexibility, semi-precast concrete slabs with lattice girders are widely used in constructions all over the world. Prefabricated concrete slabs, combined with in situ concrete topping, exhibit a quasi-monolithic structural behavior in which lattice girders serve as vertical shear reinforcement and ensure the transfer of longitudinal shear within the interface, acting in combination with concrete-to-concrete bonding mechanisms. To be applicable in industrial and bridge construction, semi-precast slabs need to have sufficient resistance against fatigue failure. To improve and expand the limits of application, theoretical and experimental investigations are conducted at the Institute of Structural Concrete (IMB), RWTH Aachen University. To investigate the fatigue behavior of lattice girders, small size tests with lattice girder diagonals were carried out. These test results have been used to derive an S–N curve (S: stress, N: number of load cycles) for lattice girders for a more refined fatigue design. Subsequently, the fatigue behavior of semi-precast slabs with lattice girders was investigated by fatigue tests on single-span slab segments. The fatigue design regulations of lattice girders according to technical approvals can generally be confirmed by this test program; however, they tend to be conservative. The use of the derived S–N curve leads to significantly improved agreement of fatigue behavior observed in tests and design expressions.

Comparative theoretical study of the resonance frequencies of the longitudinal-shear and torsion modes of the magnetoelectric effect in a two-layer magnetostrictive-piezoelectric structure Metglas / GaAs

The article is devoted to a comparative theoretical study of the frequencies of the electromechanical resonance (EMR) of the magnetoelectric (ME) effect in the magnetostrictive-piezosemiconductor structure Metglas / GaAs of the longitudinal-shear and torsional modes. It is found that the resonance frequencies for the torsional mode are approximately 2 times higher than the corresponding frequencies for the longitudinal-shear mode. Therefore, it is quite possible to observe the torsional mode of the ME effect against the background of the longitudinal-shear mode, since the resonance frequencies are well distinguishable. The results obtained can find application in the construction of new ME devices.

Optimal hole shape for arrest of longitudinal shear crack

Рассматривается задача об отыскании оптимальной формы отверстия в вершине трещины продольного сдвига. Искомая форма отверстия удовлетворяет условию минимальной концентрации напряжений на его контуре. Исследуется влияние отверстия оптимальной формы на торможение трещины. Дается критерий и метод решения задачи по предотвращению хрупкого разрушения тела, ослабленного прямолинейной трещиной продольного сдвига. Используется минимаксный критерий. Получено условие хрупкого разрушения. The problem of finding optimal hole shape at the tip of a longitudinal shear crack is considered. The desired hole shape satisfies the condition of the minimum stress concentration on the contour. The effect of the optimal hole shape on deceleration of a crack is studied. A criterion and solution method for the problem of preventing brittle fracture of the solid weakened by rectilinear longitudinal shear crack is given. The minimax criterion is used. The brittle fracture condition is obtained.

Longitudinal shear in composite deck slabs using corrugated steel sheets

Profile deck steel sheets are used in composite deck slabs. These sheets are standard in dimensions and shapes besides they are supplied with embossments and indentations. Such sheets are not available in Iraqi markets nowadays therefore people used another type of sheets which are corrugated without embossments or indentations in very wide range. This study covers the use of such sheets in composite slabs as decks instead of standard profiled steel sheets. The study comprises testing slabs of dimensions 0.9 × 2.5 m reinforced by steel fabric mesh and rested on corrugated sheets. Two types of shear spans are selected shorter and longer to study the longitudinal shear force transmitted due to the applied loads according to the Eurocode 4. The shorter shear spans are 600, 500 and 400 mm while longer one is 800, 750 and 700 mm. The study extended to support the requirements of design equation of the Eurocode by shear bond method also known as m–k method. The evaluated values of m and k are 0.094 and 65 respectively. The result of k which plays a very important role in shear transfer is small compared to what available in literature, therefore it is recommended to make use of shear connectors in such construction or any else method.