Search Results (9)

Rainfall can easily cause local sliding and collapse of carbonaceous mudstone deep road cut slopes. In order to study the strength characteristics of carbonaceous mudstone under different water environments, large-scale horizontal push shear tests were conducted on carbonaceous mudstone rock masses in their natural state and after immersion in saturated water. The push shear force–displacement relationship curve and fracture surface shape characteristics of carbonaceous mudstone samples were analyzed, and the shear strength index of carbonaceous mudstone was obtained, and numerical simulations on the stability and support effect of carbonaceous mudstone slopes were conducted. The research results indicate that carbonaceous mudstone can exhibit good structural properties and typical strain softening characteristics under natural conditions. The fracture surface, shear strength, and shear deformation process of carbonaceous mudstone samples will undergo significant changes after being soaked in saturated water. The average cohesion decreases by 33% compared to the natural state, and the internal friction angle decreases by 15%. The numerical simulation results also fully verify the attenuation of mechanical properties of carbonaceous mudstone after immersion, as well as the effectiveness of prestressed anchor cables and frame beams in supporting carbonaceous mudstone slopes. The research results provide an effective method for understanding the shear performance of carbonaceous mudstone and practical guidance for evaluating the stability and reinforcement design of carbonaceous mudstone slopes. Full article

Timber–concrete composites are established structural elements to combine the advantageous properties of both materials by connecting them. In this work, an innovative flexible adhesive connection in different configurations is investigated. Load-bearing capacity, stiffness, and the failure modes were first experimentally investigated by performing push-out tests. Subsequently, a numerical evaluation using ABAQUS 2017/Standard software was carried out in order to develop a three-dimensional numerical model. The Cohesive Zone Model (CZM) is employed to represent the adhesive characteristics at the contact areas between the Cross-Laminated Timber (CLT) and concrete elements. Three different connection configurations were evaluated, each consisting of five push-out specimens. The study investigates the impact of bonding surface area and the alignment of prefabricated glue strips with the load direction on the connection’s longitudinal shear load-bearing capacity, stiffness, and slip modulus. In addition, the impact of cyclic loads and the impact of time on displacements were analyzed. The average load capacity of the full surface connection (type A) is 44.5% and 46.2% higher than the vertical adhesive strips (type B) and the horizontal adhesive strips (type C), respectively. However, the initial stiffness of the tested joints depends on the orientation of the prefabricated adhesive fasteners, being approximately 20% higher when the bonding elements are aligned parallel to the load direction compared to when they are oriented perpendicularly. Full article

Current formulas to assess the shear capacity of headed steel stud anchors and post-installed (PI) anchors in case of pryout failure (sometimes known as pull-rear failure) have been derived either based on the indirect-tension resistance model or are fully empirical based on push-out test results. In both cases, the predicted pryout capacity is clearly conservative and underestimates the true pryout capacity of anchorages, especially for stiff anchors with low embedment-to-diameter ratios (h_ef/d < 4.5). This paper proposes an empirical and a semi-empirical formula to predict the concrete pryout capacity of headed steel studs and PI anchors. They were derived based on an improved indirect-tension model which accounts for the stud diameter and the stud spacing in a group of anchors. Furthermore, a database of 214 monotonic shear tests from the literature, including own tests (push-off and horizontally shear tests), is reevaluated and compared to the provisions of EN1992-4. The scope of this assessment proposal includes single and group of headed steel studs and PI anchors attached to a stiff steel plate as well as shear connectors in composite structures without metal deck embedded in normal-weight concrete. Full article

An innovative horizontal-arranged shear stud was proposed for prefabricated composite beams, in response to the engineering demand for accelerated precast decks construction on steel–concrete composite bridges. In order to verify the shear behavior of the studs, a push-out test was performed in which two groups of specimens were designed, and each group included three specimens. In addition, a finite element method based on the ABAQUS2020 software was adopted to analyze the influence factors of the prefabricated studs, which reveals the most influential factor, to provide a guide for optimum design. Therefore, 10 models were established, including one finite element model with the same parameters as the push-out test, and 9 models based on an orthogonal testing design. The results showed that, firstly, the prefabricated shear studs had longitudinal shear resistance, the same as conventional shear studs. Secondly, the ultimate load capacity, as well as the ductility of the prefabricated studs, was better than conventional studs. Thirdly, the modeling results were in good agreement with the push-out test results, which indicated the validity of the modeling method. Lastly, by analyzing the calculated results of the nine orthogonal models, it was found that the stud diameter was the most influential factor for the shear capacity, and the shear capacity was directly proportional to the stud diameter, while it was not proportional to the other factors. This study is evidence that the orthogonal testing design has a high efficiency in finite element modeling, which will provide a guide for the optimum design of prefabricated shear studs. Full article

The PBL (Perfobond Leiste) shear connector has the advantages of high bearing capacity and strong constraint ability; however, the traditional PBL shear connector has strong and weak axis problems, and its stiffness is large, resulting in weak deformation ability. To this end, this paper proposes a new type of flange triple-web shear key and obtains the new shear key’s mechanical properties and failure mechanism through the push-out test. The results show that the failure mode of the new shear key is the deformation of the steel plate on the web and the edge of the opening, which has a high bearing capacity, outstanding deformation ability, and good integrity with concrete, showing obvious semi-rigid characteristics. Through numerical analysis, the effects of flange width, web height, and steel plate thickness on the mechanical properties of shear keys are obtained. Based on the fitting analysis method, the calculation formula of shear key bearing capacity is proposed. Finally, the horizontal seismic performance of the shear key is numerically simulated. It is found that the hysteretic curve of the shear key is full and shows good energy dissipation capacity. Full article

This study investigates the complex load-bearing mechanism of the reinforced concrete tower of large wind turbines through a structural model test. MTS electro-hydraulic servo loading system was used to load two reinforced concrete tower models for the push-out test. The ultimate bearing capacity of the reinforced concrete tower was found to be 8.894 kN. The test findings revealed that the top of the tower is subjected to unilateral shear as the horizontal load increases. As a result, the concrete strain in the compression zone of the test piece increases to its highest level in the bottom plastic hinge area. The concrete in the compression zone is being crushed in the meantime. The reinforcement achieves its yield point and deforms within the range of plastic failure when subjected to extreme loads. The outcomes of this study serve as a foundation for the running of wind turbines in extreme conditions. Full article

In a precast concrete (PC) composite beam, the horizontal interface between the PC beam and the cast-in-place (CIP) slab is located either on the compression side or on the tensile side of the cross-section. If the CIP slab is on the compression side, it becomes C-type interface, and if it is on the tensile side, it becomes T-type interface. Tensile cracks in the CIP slab may cause the horizontal shear strength of composite beams to decrease because of the reduced anchorage performance of shear reinforcements as well as the sliding on the interface. Such a tendency can be found from previous test results of specimens having T-type interface. In this study, the results of the push-off test and the beam flexure test were collected and analyzed to evaluate effects on the horizontal shear strength depending on the interface conditions, such as the interface location, surface roughness, concrete compressive strength, and clamping stress by shear connectors. The horizontal shear strength equations of ACI, PCI, AASHTO LRFD, and MC 2010 were evaluated with a database composed of 84 push-off tests and 95 beam tests from previous studies. According to the evaluation, evaluation results show that the design codes predict the horizontal shear strength conservatively for conditions other than the interface location. The horizontal shear strength deviated largely depending on the interface locations. The design codes conservatively estimate the horizontal shear strength for C-type interface, but the horizontal shear strength of T-type interface is overestimated. Based on current studies, it is recommended to use a friction coefficient of 0.7 as MC 2010 when calculating the horizontal shear strength of a composite beam with roughened T-type interface. Full article

This paper develops a new type of shear connection for steel-concrete composite bridges using Ultra-High Performance Concrete (UHPC) as the connection grout. The UHPC-grout strip shear connection is fabricated by preforming a roughened slot in the concrete deck slab, welding an embossed steel rib longitudinally to the upper flange of the steel girder, and casting the strip void between the slot and the steel rib with UHPC grout. The structural performance of the new connection was validated by two sets of experimental tests, including push-out testing of shear connectors and static and fatigue testing of composite beams. The results of push-out testing indicate that the UHPC-grout strip shear connection exhibits a significant improvement of ductility, ultimate capacity, and fatigue performance. The interface shear strength of the UHPC-grout strip connection is beyond 15 MPa, which is about three times that of the strip connection using traditional cementitious grouts. The ultimate capacity of the connection is dominated by the interface failure between the embossed steel and the UHPC grout. The results of composite-beam testing indicate that full composite action is developed between the precast decks and the steel beams, and the composite action remained intact after testing for two million load cycles. Finally, the trail design of a prototype bridge shows that this new connection has the potential to meet the requirements for horizontal shear. Full article

The beam-column joints are very restricted areas in which the internal forces, generated by boundary elements, act on the concrete core and reinforcing bars with a very high gradient. They are the link between horizontal and vertical structural elements, and therefore, they are directly involved in the transfer of seismic forces. Thus, they are crucial to study the seismic behavior of reinforced concrete (RC) structures. To fully understand the seismic performances and failure modes of beam-column joints in RC buildings, a simplified analytical model of joint behavior is proposed and theoretical simulations are performed. The aim of the model, focusing on internal perimetric joints, is to identify the strength hierarchy in terms of capacity for different failure modes (namely failure of cracked joint, bond failure of passing through bars, flexural/shear failures of columns or beams). It could represent a tool for the designers of new joints to quantify the performance of new structures, but also as a tool for the designers of external strengthening of existing joints in order to calculate the benefits of the retrofit and pushing the initial failure to a more desirable failure mode. Further, some experimental results of tests available in the scientific literature are reported, analyzed and compared. Full article