Search Results (15)

The dynamic behavior of three-layer composite beams, consisting of concrete slabs and steel beams, is influenced by the structural configuration of each layer as well as the shear connectors. The interlayer shear stiffness in three-layer composite beams governs their global dynamic behavior, while interlayer slippage-induced localized vibration effects represent a key limiting factor in practical applications. Based on the dynamic test results of steel–concrete double-layer composite beams, the feasibility of a finite element solid model for composite beams, which accounts for interlayer shear connectors and beam body characteristics, has been validated. Utilizing identical modeling parameters, an analytical model for the inherent vibration characteristics of three-layer steel–concrete composite beams has been developed. This study encompasses two types of composite beams: concrete–steel–concrete (CSC) and concrete–concrete–steel (CCS). Numerical simulations and theoretical analysis systematically investigated the effects of interface shear connector arrangements and structural geometric parameters on dynamic performance. Research indicates that the natural frequency of steel–concrete three-layer composite beams exhibits a distinct two-stage increasing trend with the enhancement in interlayer shear stiffness. For CSC-type simply supported composite beams, the fundamental vertical vibration frequency increases by 37.82% when achieving full shear connection at both interfaces compared to the unconnected state, while two-equal-span continuous beams show a 38.06% improvement. However, significant differences remain between the fully shear-connected state and theoretical rigid-bonding condition, with frequency discrepancies of 24.69% for simply supported beams and 24.07% for continuous beams. Notably, CCS-type simply supported beams display a 12.07% frequency increase with full concrete-to-concrete connection, exceeding even the theoretical rigid-bonding frequency value. Longitudinal connector arrangement non-uniformity significantly impacts dynamic characteristics, while the transverse arrangement has minimal influence. Among structural parameters, steel flange plate thickness has the most significant effect, followed by concrete slab width and thickness, with steel web thickness having the least impact. Based on the observation that the first-order vertical vibration frequency of three-layer composite beams exhibits a two-stage decreasing trend with an increase in the span-to-depth ratio, it is recommended that the span-to-depth ratio of three-layer steel–concrete composite beams should not be less than 10. Full article

Traditional stone masonry walls are structural elements in most historic buildings. To preserve them and improve their ability to withstand extreme events, such as earthquakes, it is necessary to implement effective reinforcement solutions. This paper presents the modeling of traditional Portuguese rubble stone masonry walls, reinforced with external steel mesh, sprayed micro-concrete layers and transverse confinement by steel connectors, which were developed and tested experimentally in uniaxial compression. The modeling is carried out using micro-modeling through a 2D particle model (PM). The process of calibrating the properties of both micro-concrete and concrete is presented, the methodology for generating the numerical models is described and the numerical response is compared with the experimental results. The numerical results show that the PM can adequately reproduce the experimentally observed behavior of this type of reinforcement solution. Full article

The behavior of steel–concrete composite structures is significantly influenced by the efficiency of the shear connections that link the two materials. This research examines the performance of stud shear connectors, with an emphasis on analyzing the effect of different geometric design parameters. A computational model was created utilizing Python 3.13 to enable thorough digital monitoring of the influence of these parameters on the structural performance of composite connections. Developed within the ABAQUS framework, the model integrates geometric nonlinearity and the Concrete Damage Plasticity (CDP) approach to achieve detailed simulation of structural behavior. Essential design aspects, including stud diameter, stud height, head dimensions, and spacing in both longitudinal and transverse directions, were analyzed. The Python-based parametric model allows for easy modification of design parameters, ensuring efficiency and minimizing modeling errors. The significance of stud diameter changes was analyzed in accordance with Eurocode standards and previous studies. It was found that stud length has a reduced effect on structural performance, particularly when considering the concrete properties used in bridge construction, where compressive failure of the concrete zone is more critical at lower concrete strengths. Additional factors, such as stud head dimensions, were investigated but were found to have minimal effect on the behavior of steel–concrete composite connections. Longitudinal stud spacing emerged as a critical factor influencing structural performance, with optimal results achieved at a spacing of 13d. Spacings of 2d, 3d, and 4d demonstrated overlapping effects, leading to significant performance reductions, as indicated by comparisons of ultimate load and force–displacement responses. For transverse spacing, closer stud arrangements proved effective in reducing the likelihood of slip at the steel–concrete interface, enhancing composite action, and lowering stress concentrations. Additionally, reducing the transverse distance between studs allowed for the use of more shear connectors, increasing redundancy and enhancing performance, especially with grouped-stud connectors (GSCs). Full article

A depth precast deck panel (FDDP) is one element of the prefabricated bridge element and systems (PBES) that allows for quick un-shored assembly of the bridge deck on-site as part of the accelerated bridge construction (ABC) technology. This paper investigates the structural response of full-depth precast deck panels (FDDPs) constructed with new construction materials and connection details. FDDP is cast with normal strength concrete (NSC) and reinforced with high modulus (HM) glass fiber reinforced polymer (GFRP) ribbed bars. The panel-to-girder V-shape connections use the shear pockets to accommodate the clustering of the shear connectors. A novel transverse connection between panels has been developed, featuring three distinct female-to-female joint configurations, each with 175-mm projected GFRP bars extending from the FDDP into the closure strip, complemented by a female vertical shear key and filled with cementitious materials. The ultra-high performance fiber reinforced concrete (UHPFRC) was selectively used to joint-fill the 200-mm transverse joint between adjacent precast panels and the shear pockets connecting the panels to the supporting girders to ensure full shear interaction. Two actual-size FDDP specimens for each type of the three developed joints were erected to perform fatigue tests under the footprint of the Canadian Highway Bridge Design Code (CHBDC) truck wheel loading. The FDDP had a 200-mm thickness, 2500-mm width, and 2400-mm length in traffic direction; the rest was over braced steel twin girders. Two types of fatigue test were performed: incremental variable amplitude fatigue (VAF) loading and constant amplitude fatigue (CAF) loading, followed by monotonically loading the slab ultimate-to-collapse. It was observed that fatigue test results showed that the ultimate capacity of the slab under VAF loading or after 4 million cycles of CAF exceeded the factored design wheel load specified in the CHBDC. Also, the punching shear failure mode was dominant in all the tested FDDP specimens. Full article

Given the widespread use of lightweight composite wall panels in building structures, it is crucial to comprehend their seismic performance. This paper proposes a new lightweight concrete composite exterior wallboard (LCEW) featuring truss-type thermal barrier connectors (TBCs). Through the proposed static test, the damage morphology and hysteresis curve of the specimen are obtained; the hysteresis characteristics, skeleton curve, stiffness degradation, etc., are investigated; and the damage modes are summarized. The results demonstrate that the steel frame structure can effectively adapt to the use of LCEW, resulting in an approximately 20% increase in the frame structure’s bearing capacity. Second, the wall panels with a uniform transverse arrangement of TBCs could not perform as well, as they could only delay the crack opening. To give full play to its effect, it should be combined with the direction of the main tensile zone of the wall panels. Meanwhile, the sliding gusset connections effectively released the frame action at the system level. Full article

The narrow-width steel box girder is an important type of steel–concrete composite bridge structure, which is usually composed of reinforced concrete wing plates, narrow steel boxes partially injected with concrete, and shear connectors that promote shear force transfer. The utilization of narrow-width steel box girders, augmented by partially filled concrete, embodies the synthesis of steel and concrete elements, fostering structural efficiency. Moreover, its attributes, including reduced structural weight, diminished vertical profile, enhanced load-bearing capacity, and augmented stiffness, have prompted its gradual integration into bridge engineering applications. In this study, the calculated values of shear strength under three current design codes were reviewed, and the shear failure phenomena and its determinants of narrow-width steel box–ultra-high-performance concrete (UHPC) composite beams under negative bending moment conditions were investigated, which were mainly determined by shear span ratio, concrete wing plate, UHPC steel fiber content, UHPC plate thickness, and transverse partition inside the box. Concurrently, this paper evaluates two innovative structural designs, including a double-narrow steel box girder and a three-narrow steel box girder. In addition, strategies to reduce crack formation under the negative bending moment of long-span continuous narrow and wide box girder abutments are discussed, and we show that this measure can effectively control the formation of cracks to support the negative bending moment zone. At the same time, the scope of the application of a narrow-width steel box girder composite bridge is reviewed, and the conclusion is that a narrow-width steel box girder is mainly used in small-radius flat-curved bridges or widened-ramp bridges with a span of 30 m or more in interworking areas and in the main line with a 60–100 m span in mountainous or urban areas. Finally, the research direction of the shear resistance of the UHPC–narrow steel box girder under negative bending moments is proposed. Full article

Due to the shear strain in the plane of the slab, the parts of the slab remote from the steel beam lag behind the part of the slab located in its proximity. This shear lag effect causes a non-uniform stress distribution across the width of the slab. As a result, several standards have introduced the concept of an effective flange width to simplify the analysis of stress distribution across the width of composite beams. Both the computed ultimate moment and serviceability limit states are directly impacted by the effective width. The effect of using a large number of contact points as shear connectors on the effective width of a steel beam flange has not been investigated. A three-dimensional finite element analysis is carried out in this paper. The ABAQUS software (version 6.14) is used for this purpose, where several variables are considered, including the surface area connecting the steel beam and concrete slab, the transverse space, and the number of shear connectors. It was discovered that the number of shear connectors on the steel beam flange has a major impact on the effective width. The many connectors work together to provide a shear surface that improves the effective width by lowering the value of the shear lag. Full article

The structural rehabilitation of historic/traditional rubble masonry wall constructions requires consolidation and retrofitting solutions to be employed in order to withstand dynamic loads, high vertical loads, and differential settlements. One of these strengthening techniques is based on the use of steel bar connectors perpendicular to the wall, considered individually or integrated into more complex strengthening techniques. The aim of this study is to evaluate numerically the strengthening effect of transverse steel connectors on rubble masonry walls. With this purpose, a 2D particle-reinforced model (2D-PMR) was devised and applied to model uniaxial compression tests. The results presented show that predictions calculated using the proposed 2D-PMR model are very close to known experimental results, particularly in the corresponding failure modes, the increase of the maximum uniaxial compression value, and ductility. Parametric studies are also conducted by varying the diameter of the steel bars and the level of strengthening to assess the influence of the bar-bond effect and lateral plates. The presented parametric numerical studies show that (i) a two-level strengthening solution guarantees a similar response to the three-level strengthening solution adopted in the experiments; (ii) it is not relevant to apply a grout injection during the application process of the steel connectors if lateral plates are adopted; and (iii) the 2D-PMR model can be used in the definition of the steel bar diameter and properties; as shown, a smaller (8 mm) bar diameter predicts a similar strengthening effect to the (12 mm) bar size adopted in the experiments. Given the performance of the proposed 2D-PMR model, further work is underway that will allow the 2D-PMR model to numerically assess other reinforcement techniques, namely, reinforced micro-concrete layers and textile reinforced mortar. Full article

As the standards of bridge design and construction continue to improve, more and more combination bridges are being put into use. The public’s demand for aesthetically pleasing bridges is also increasing, making it necessary to use the special structure of steel–concrete combinations, continuous V-shaped piers, and continuously stiffened bridges. This structure has the structural and mechanical characteristics of both a continuous girder and a V-shaped pier bridge. The span can be reduced to a certain extent because the support of the V-shaped piers can be applied directly to the main girder. The spanning capacity of the bridge is generally greater than that of a combined steel–concrete girder bridge with vertical piers. The whole bridge is continuous, without expansion joints, making it more stable and safe for traffic. At present, research on this structural bridge type is not yet complete. In this paper, the structural system and dynamic characteristics of this bridge are investigated in the context of real-life engineering. Firstly, the self-vibration characteristics of the three structures were analyzed, and their effects on the self-vibration characteristics were studied by varying the height of the crossbeam at the V-shaped piers’ support, the main beam stiffness, and the V-shaped piers’ stiffness in the three structures. The results show that the increase in main beam stiffness can effectively improve the vertical stiffness of the three structures, with the most obvious effect on structure one and the least effect on structure two; the increase in V-shaped pier stiffness causes a huge improvement in the transverse stiffness of the three structures. Subsequently, a two-unit rod system model of the background bridge was established using the finite element method, and the original model was improved by calculating the equivalent shear stiffness of the shear nail group so that it could simulate the shear joints more accurately. The effects of the shear connectors on the self-vibration characteristics of the steel–concrete combined continuous beam–V-shaped piers and continuous rigid-frame bridge were investigated through theoretical analysis and finite element simulation. It was found that due to the existence of flexible shear connectors, the interface between the steel beam and concrete slab in the combined beam has a slippage effect which causes the deformation to become unsynchronized, and there is a certain difference between vibration patterns. The stiffness of the shear connectors has a certain effect on the self-vibration frequency of the bridge. The damage to the local shear connectors does not have a large effect on the self-vibration frequency of the overall structure, but the damage to the shear connectors at the beginning of the connection between the V-shaped piers and the main beam is greater than that of the other areas. Damage to shear joints should be given special consideration in comparison to other areas. Full article

Assembled steel-composite bridges generally use stud connectors to achieve the connection between the deck slab and the steel main girders. However, the commonly-used cluster studs weaken the integrity of the precast deck slabs and are not conducive to reducing the size of the precast deck slabs. Based on the excellent mechanical performance of UHPC, a precast steel-concrete composite bridge system consisting of precast bridge deck slabs, bonding cavities, and steel girders was proposed in this study. The system was named PSCC (Precast Steel-Concrete Connectors). To verify the applicability of PSCC connectors in engineering, push-out tests and finite element analysis were carried out in this paper to investigate the shear performance and influence parameters of PSCC connectors. The results showed that compared with the full bonding at the steel-UHPC interface, the shear bearing capacity of the specimens with 30% debonded area rate (the ratio of defect area to total interface area) and the shear bearing capacity of the specimens with 60% debonded area rate decreased by 0.35% and 9.74%, the elastic stiffness decreased by 14.86% and 21.72%, and the elastic-plastic stiffness decreased by 1.6% and 12.8%, respectively. When the steel-UHPC percentage of debonded area is less than 30%, the shear resistance of PSCC connectors is affected very little. However, when the steel-UHPC percentage of debonded area is 60%, the shear resistance of PSCC connectors is greatly affected. Therefore, adequate filling of the UHPC connection layer should be ensured in the project. In addition, the PSCC connectors have excellent ductility, their characteristic slip value $S_u$ is much higher than the EC4 specification of 6 mm, and they have better shear performance than conventionally installed stud connectors. According to the results of the parametric analysis, it was found that the failure mode of the PSCC connectors was shear reinforcement fracture when the area ratio of shear reinforcement to stud was less than 1.55, under the premise of the same material strength. On the contrary, the failure mode of PSCC connections was stud fracture. When the transverse spacing of both studs and shear reinforcement is 4d, the PSCC connectors can maintain a high ultimate load capacity while reducing the amount of UHPC in the bonding cavity. Therefore, 4d was chosen as the best spacing for both studs and shear reinforcement. Full article

Poplar laminated veneer lumber (poplar LVL) is made of fast-growing poplar veneer and structural adhesive, which owns the advantages of sustainability and stable quality. Here an innovative poplar LVL floor diaphragm is presented, mainly made up of orthogonal rib beams fitted together using L-shape steel connectors. The paper mainly deals with an experimental study on the bending behavior of the floor under transverse uniform load. Full-scale testing on eight 3.6 m × 4.8 m specimens shows that the damage phenomena of the floor mainly exhibited as the separation between the rib beams and pulling out from the rib beam for the tapping screw. Though some local damage phenomena appeared before the preset maximum loading level, the load-deflection curves basically kept linear for most of the specimens. Under the service load level of 2.5 kN/m², the distribution of deflection and strain for the full-length rib beam substantially exhibited the characteristic of a two-way slab. In contrast, for the segmented rib beam, the situation was much more complex. Due to the parametric design of the specimens, testing results illustrated that the rib beam height played the most important role in floor stiffness. Next was the sheathing panel, while the role of segmented rib beam spacing was relatively unremarkable. At last, a revised pseudo-plate method was proposed to evaluate the maximum deflection of the novel floor, which considered the composite action by rigidity factors. Full article

(1) Background: Mandibular deficiency is one of the most common growth disorders of the facial skeleton. Recently, distraction osteogenesis has been suggested as the treatment of choice for overcoming the limitations of conventional orthognathic surgery; (2) Methods: A new custom-manufactured dental-anchored distractor was built and anchored in the first molar and lower canine. It consists of a stainless-steel disjunction screw, adapted and welded to the orthodontic bands through two 1.2 mm diameter connector bars with a universal silver-based and cadmium-free solder; (3) Results: The distractor described can be a useful tool to correct mandibular retrognathia and is better tolerated by patients, especially in severe cases; (4) Conclusions: The dental-anchored distractor increases the anterior mandibular bone segment without affecting the gonial angle or transverse angulation of the segments and avoids posterior mandibular rotation, overcoming the limitations of conventional surgical treatment. Full article

Industrialization of construction makes building operation more environmental friendly and sustainable. This change is necessary as it is an industry that demands large consumption of water and energy, as well as being responsible for the disposal of a high volume of waste. However, the transformation of the construction sector is a big challenge worldwide. It is also well known that the largest proportion of the material used in multistory buildings, and thus its carbon impact, is attributed to their slabs being the main contributor of weight. Steel-Concrete composite beams with precast hollow-core slabs (PCHCSs) were developed due to their technical and economic benefits, owing to their high strength and concrete self-weight reduction, making this system economical and with lower environmental footprint, thus reducing carbon emissions. Significant research has been carried out on deep hollow-core slabs due to the need to overcome larger spans that resist high loads. The publication SCI P401, in accordance with Eurocode 4, is however limited to hollow-core slabs with depths from 150 to 250 mm, with or without a concrete topping. This paper aims to investigate hollow-core slabs with a concrete topping to understand their effect on the flexural behavior of Steel-Concrete composite beams, considering the hollow-core-slab depth is greater than the SCI P401 recommendation. Consequently, 150 mm and 265 mm hollow-core units with a concrete topping were considered to assess the increase of the hollow core unit depth. A comprehensive computational parametric study was conducted by varying the in situ infill concrete strength, the transverse reinforcement rate, the shear connector spacing, and the cross-section of steel. Both full and partial interaction models were examined, and in some cases similar resistances were obtained, meaning that the same strength can be obtained for a smaller number of shear studs, i.e., less energy consumption, thus a reduction in the embodied energy. The calculation procedure, according to Eurocode 4 was in favor of safety for the partial-interaction hypothesis. Full article

This study presents an experimental investigation into the mechanical performance of built-up columns composed of four cold-formed square steel tubes under axial load. The four tubes were assembled together with several C-shaped connectors through two self-tapping screws in each junction. The influence of parameters including spacing between tubes, type of connectors and transverse diaphragm were analyzed based on the failure modes, ultimate loads, load-displacement relationships and load-strain relationships measured in the tests. Moreover, a further numerical analysis was carried out to study the effect of the number of connectors, web height of connectors and installing connectors at column ends by means of the verified finite element models. Finally, the numerical results were compared with the strengths predicted by the AISI-S100-2012 code. Results show that the performance of built-up columns can be influenced by the change in the number of connectors and ratio of web height of connectors to spacing between tubes as well as the installation of connectors at column ends. In addition, the current AISI-S100-12 specifications do not provide a good prediction of the built-up columns composed of four cold-formed square steel tubes. Full article

Shear connectors are used in steel beam–concrete slabs of composite frame and bridge structures to transfer shear force according to design loads. The existing Y-type perfobond rib shear connectors are designed for girder slabs of composite bridges. Therefore, the rib and transverse rebars of the conventional Y-type perfobond rib shear connectors are extremely large for the composite frames of building structures. Thus, this paper proposes stubby Y-type perfobond rib shear connectors, redefining the existing connectors, for composite frames of building structures; these were used to perform push-out tests. These shear connectors have relatively small ribs compared to the conventional Y-type perfobond rib shear connectors. To confirm the shear resistance of these stubby shear connectors, we performed an experiment by using transverse rebars D13 and D16. The results indicate that these shear connectors have suitable shear strength and ductility for application in composite frame structures. The shear strengths obtained using D13 and D16 were not significantly different. However, the ductility of the shear connectors with D16 was 45.1% higher than that of the shear connectors with D13. Full article