Uniform Vertical Load Research Articles

Influence of Connector Design on Displacement and Micromotion in Tooth-Implant Fixed Partial Dentures Using Different Lengths and Diameters: A Three-Dimensional Finite Element Study.

The literature presents insufficient data evaluating the displacement and micromotion effects resulting from the combined use of tooth-implant connections in fixed partial dentures. Analyzing the biomechanical behavior of tooth-implant fixed partial denture (FPD) prothesis is vital for achieving an optimum design and successful clinical implementation. The objective of this study was to determine the relative significance of connector design on the displacement and micromotion of tooth-implant-supported fixed dental prostheses under occlusal vertical loading. A unilateral Kennedy class I mandibular model was created using a 3D reconstruction from CT scan data. Eight simulated designs of tooth-implant fixed partial dentures (FPDs) were split into two groups: Group A with rigid connectors and Group B with non-rigid connectors. The models were subjected to a uniform vertical load of 100 N. Displacement, strain, and stress were computed using finite element analysis. The materials were defined as isotropic, homogeneous, and exhibiting linear elastic properties. This study focused on assessing the maximum displacement in various components, including the bridge, mandible, dentin, cementum, periodontal ligament (PDL), and implant. Displacement values were predominantly higher in Group B (non-rigid) compared to Group A (rigid) in all measured components of the tooth-implant FPDs. Accordingly, a statistically significant difference was observed between the two groups at the FPD bridge (p value = 0.021 *), mandible (p value = 0.021 *), dentin (p value = 0.043 *), cementum (p value = 0.043 *), and PDL (p value = 0.043 *). Meanwhile, there was an insignificant increase in displacement values recorded in the distal implant (p value = 0.083). This study highlighted the importance of connector design in the overall stability and performance of the prosthesis. Notably, the 4.7 mm × 10 mm implant in Group B showed a displacement nearly 92 times higher than its rigid counterpart in Group A. Overall, the 5.7 mm × 10 mm combination of implant length and diameter showcased the best performance in both groups. The findings demonstrate that wider implants with a proportional length offer greater resistance to displacement forces. In addition, the use of rigid connection design provides superior biomechanical performance in tooth-implant fixed partial dentures and reduces the risk of micromotion with its associated complications such as ligament overstretching and implant overload, achieving predictable prognosis and enhancing the stability of the protheses.

Performance Optimization of Piled Raft Foundations in Layered Soil under Uniform Vertical Loading Using Plaxis 3D

Piled raft foundations are composite foundations that combine piles and raft to support civil engineering structure and to reduce the settlement. The data were obtained from Addis Ababa, Ethiopia. In this study, the effects of raft thickness, number of piles, pile length, spacing of piles, and pile diameter on the response of piled-raft foundations were investigated using the finite element-based program Plaxis 3D for layered soils (medium to very stiff high plastic silty clay and medium to very dense silty sand soil) subjected to uniform vertical loading. The results showed that increasing the thickness of the raft from 0.7 m to 1.7 m reduced the differential settlement by 78.21% when there were 16 piles. However, the maximum settlement also increased by 2.81%. Increasing the number of piles from 4 to 16 reduced the maximum settlement by 22.09% for a pile spacing of 4D. Moreover, increasing the pile length from 9 m to 15 m contributed to a 19.49% reduction in the total settlement for a pile spacing of 5D. Therefore, the current study provides a useful framework for analyzing and designing large piled-raft foundations.

Experimental and theoretical research on flexural performance of truss reinforced concrete two-way composite slab with prefabricated baseplate

This paper presents experimental and theoretical research on a novel truss reinforced composite concrete two-way slab using full-scale testing. In contrast to conventional composite slabs, the precast concrete layer with a thickness greater than 60 mm is replaced by a high toughness prefabricated inorganic baseplate with a thickness of 12 mm. The baseplate options include glass fiber and magnesium cement board, as well as fiber cement board. Four full-scale two-way slabs were subjected to eight points simulated uniform vertical loads, comprising one conventional truss reinforced concrete two-way slab (RCS) and three truss reinforced concrete composite two-way slabs with prefabricated baseplates (RCSB). The test results indicate that the failure mode of the truss reinforced concrete composite two-way slab with baseplate is similar to that of a common truss reinforced concrete two-way slab. However, a rectangular yielding region appears at the central part, instead of a single yielding line. The cracking load and ultimate load are increased due to the effect of prefabricated baseplate. Moreover, the beneficial effect of glass fiber and magnesium cement board is superior to that of fiber cement board. Finally, the calculation methods for determining the cracking load and ultimate bearing capacity of truss reinforced concrete composite two-way slabs with baseplates were improved, and the calculated results are in good agreement with experimental data.

Time-harmonic loading over a piezoelectric layered half-space

Mathematical modeling of multilayered piezoelectric (PE) ceramic substantially acquires attention due to its distinctive advantages of fast response time, positioning, optical systems, vibration feedback, and sensors, such as deformation and vibration control. As such, fundamental solution of a PE structure is essential. This paper presents three-dimensional (3D) static and dynamic solutions (i.e. Green’s functions) in a multilayered transversally isotropic (TI) PE layered half-space. The uniform vertical mechanical load, vertical electrical displacement, and horizontal mechanical load are applied on the surface of the structure. The novel Fourier-Bessel series (FBS) system of vector functions (which is computationally more powerful and streamlined) and the dual-variable and position (DVP) method are employed to solve the related boundary-value problem. Two systems of first-order ordinary differential equations (i.e. the LM- and N-types) are obtained in terms of the FBS system of vector functions, with these expansion coefficients being the Love numbers. A recursive relation for the expansion coefficients is established by using DVP method that facilitates the combination of two neighboring layers into a new one and minimizes the computational effort to a great extent. The corresponding physical-domain solutions are acquired by applying the appropriate boundary/interface conditions. Several numerical examples pertaining to static and dynamic response are solved, and the efficiency and accuracy of the proposed solutions are validated with the existing results for the reduced cases. The solutions provided could be beneficial to better developments of PE materials, configurations, fabrication, and applications in the future.

In-Plane Failure Mechanism and Strength Design of Plate-Tube-Connected Circular Steel Arches

The in-plane elastoplastic failure mechanism of plate-tube-connected steel circular arches with inverted triangular cross sections is investigated in this study by using theoretical derivation and numerical simulation. First, the in-plane elastic buckling load formula of the arch under full-span uniform radial load (FSURL) is presented. Then, the limited conditions of avoiding the connecting plate and chord local failure before global elastic instability are derived. Lastly, the elastic–plastic failure mechanisms of arches are studied under FSURL, full-span uniform vertical load (FSUVL), and half-span uniform vertical load (HSUVL). It is found that the arch will experience global failure, chord local failure, combined connecting plate and chord failure, and connecting plate local failure under FSUVL and HSUVL. The failure mode is mainly related to the stiffness of the connecting plate. The corresponding design formulas are proposed for the global failure of arches and local failure of the chord. The proposed formulas and FE results are in good agreement.

Effect of defects and reinforcements on the mechanical behaviour of a bi-layered panel

This paper investigates the mechanical behaviour of a bi-layered panel containing many particles in one layer and demonstrates the size effect of particles on the deflection. The inclusion-based boundary element method (iBEM) considers a fully bounded bi-material system. The fundamental solution for two-jointed half spaces has been used to acquire elastic fields resulting from source fields over inclusions and boundary-avoiding multi-domain integral along the interface. Eshelby’s equivalent inclusion method is used to simulate the material mismatch with a continuously distributed eigenstrain field over the equivalent inclusion. The eigenstrain is expanded at the centre of the inclusion, which provides tailorable accuracy based on the order of the polynomial of the eigenstrain. As a single-domain approach, the iBEM algorithm is particularly suitable for conducting virtual experiments of bi-layered composites with many defects or reinforcements for both local analysis and homogenization purposes. The maximum deflection of solar panel coupons is studied under uniform vertical loading merged with inhomogeneities of different material properties, dimensions and volume fractions. The size of defects or reinforcements plays a significant role in the deflection of the panel, even with the same volume fraction, as the substrate is relatively thin.

Experimental and analytical studies on stability of ultra-strong thin-walled steel tube and coupler scaffolds

In this study, to improve the erection efficiency and reduce the weight of structures, an ultra-strong thin-walled steel tube and coupler scaffold (UTSTCS) is developed and investigated. Notably, the weight of this UTSTCS is ∼60% that of traditional scaffolds. Six ultra-high full-scale UTSTCS specimens are constructed and tested to determine the bearing capacity of the UTSTCS. A finite element model is built considering the initial member imperfection and semi-rigid behavior of right-angle couplers, based on which parametric studies are then conducted to investigate the method for determining the ultimate bearing capacity and influence of various geometric properties on the stability behavior of UTSTCSs. Compared with that of traditional scaffolds, the vertical bearing capacity of UTSTCSs does not decrease appreciably when the weight of the steel tube is reduced by 40%. Under a uniform vertical load, the main failure modes of UTSTCSs are top coupler slipping, top horizontal tube bending, and post bending. The joint type of the upper layer members, story height, and post spacing have evident influences on the bearing capacity. Moreover, the results of the proposed method for predicting the ultimate bearing capacity of UTSTCSs are in good agreement with the numerical simulation and experimental results.

Consolidation settlement of vertically loaded pile groups in multilayered poroelastic soils

Pile groups are commonly used as the foundations of many structures including those used in transportation infrastructures. Consolidation settlement of a pile foundation is an important design parameter. A theoretical model is developed in this study to estimate the consolidation settlement and axial load transfer of vertically loaded pile groups in multilayered poroelastic soils. The multilayered saturated soil is modeled according to Biot’s poroelasticity theory. In order to determine quasi-static response of pile groups, the interaction problem is first formulated in the Laplace transform domain. Vertical displacement compatibility is enforced at the pile-soil interface to simulate the pile group-soil interaction. Axial deformation of each pile is represented by an exponential series with undetermined coefficients, which are obtained from a variational approach. Vertical displacement influence functions due to a buried uniform vertical load applied to the layered soil are required in the formulation. The application of an exact stiffness matrix method yields the required influence functions. Time-domain solutions are obtained by employing a numerical Laplace inversion method. Numerical results for time-dependent vertical stiffness and consolidation settlement are presented for different pile group configurations, layer profiles, pile elastic moduli and pile lengths.

Designing funicular grids with planar quads using isotropic Linear-Weingarten surfaces

The design of curved structural building envelopes such as gridshells or cable-net roofs is challenging as it requires to account for a wide variety of constraints. In particular, the chosen shape must be mechanically efficient, fabricable, and fit the site geometry. This article shows how a family of surfaces, called isotropic Linear Weingarten (iLW) surfaces, may fulfil all these constraints together, and be used as an intuitive design tool. We start by showing that these shapes are funicular for a uniform vertical load, and that principal projected stress lines form a conjugate net. This allows in particular for the design of gridshells with planar faces and low bending moments or for the design of self-stressed cable-nets cladded by planar glass panels. We then propose a discrete model of iLW surfaces based on recent advances in discrete differential geometry. We use this model to propose an optimization-based generation method, for which the inputs are the boundary curves and two control parameters. We demonstrate the shape potential on several examples.

Shear Property and Uniform Vertical Load Capacity of Bamboo I-Beams

Bamboo oriented strand boards (BOSB) are very suitable for application in construction structures because of their excellent mechanical properties. This research investigated the shear performance of bamboo I-beams composed of BOSB to verify the structural performance of I-beams. Short beam shear tests and uniform vertical load capacity tests were performed to investigate the effects of various factors on the properties of bamboo I-beams. The results showed that shear bearing capacity and uniform vertical load capacity of bamboo I-beams exceeded the requirements for performance-rated I-Joists in APA PRI-400-2021. The shear bearing capacity, stiffness, and failure types of bamboo I-beams were determined by the web materials, flange–web joint type, and beam depth. Increasing the bamboo I-beam depth without changing the flange dimensions had no significant effect on the shear bearing capacity and stiffness of bamboo I-beams. The shear bearing capacity and stiffness of wooden orientated strand board webbed I-beams were almost half of those of bamboo I-beams with the same depth. The shear bearing capacities of specimens calculated based on the shear bearing capacity calculation formula of I-beams recommended in the Canadian standard were reasonably close to the experimental results. The uniform vertical load capacity of bamboo I-beams gradually decreased as the depth of the bamboo I-beam increased from 300 mm to 500 mm.

Flexural performance of assembly integral floor structure voided with steel mesh boxes

Enhancing the ease of construction of fillers and large-span floors and their overall mechanical performance is critical for prefabricated hollow slabs in modular building structures. Therefore, we propose a novel assembly integral two-way hollow floor structure (8.4 × 8.4 m) consisting of permanent fillers (BDF ribbed steel mesh box) and three precast one-way hollow-core slabs with I-shaped flexural sections to address the above problem. This report evaluates the overarching flexural mechanism of a large-span full-scale model of the proposed system under uniform vertical loads. The experiment supports that the structure possesses a high bi-directional vertical bearing capacity and achieves the purpose of turning three one-way precast slabs into a two-way integral floor. The deflection value of the cast-in-site concrete frame beam, as the junction between the precast and cast-in-situ sections, is 88% below the damage limit value in GB/T 50152–2012. The strain of the bottom rebars in the ribbed girder of the precast hollow slab is identical to in the hidden girder. The strain profile in the mid-span of the frame beam reveals a noticeable membrane effect, strengthening the bending resistance of the system. Additionally, the original structure was modeled using ABAQUS to study the damage mechanism further. The analysis of the plastic development history and stress-strain distribution of the specimen reveals that upgrading the concrete strength has a slight improvement on the stiffness but could lessen its damage. While rationalizing the steel configuration is a more cost-effective option. Based on the pseudo-plate method and simulation results, the deflection and internal force equations were also recommended for preliminary design.

Funicularity of conics

Funicular structures can resist a given load with pure axial forces and therefore tend to use material very efficiently. One main challenge in their design is form finding, which often requires advanced numerical methods. In this article, we show analytically that a very common family of curves, conics, is funicular for a particular load case: a uniform radial load emanating from a focus. The result is a generalization of the well-known funicularity of parabolas and arcs of circles, respectively, under uniform vertical load and constant normal pressure. It can be used to design self-stressed structures by hand without the need for calculations. Portions of conics can be combined to obtain original shapes.

Buckling Load Estimation of Two-way Grid Domes Stiffened by Diagonal Braces Under Vertical Load

The present study proposes an efficient scheme to estimate elastic-plastic buckling load of a shallow grid dome stiffened by diagonal braces. The dome is circular in plan. It is assumed to be subject to a uniform vertical load and to be supported by a substructure composed of columns and anti-earthquake braces. Based on FEM parametric studies considering various configurations and degrees of local imperfections, a set of formulations are presented to estimate the elastic-plastic buckling load. In the scheme, the linear buckling load, elastic buckling load, and imperfection sensitivity are first presented in terms of related parameters, and the elasticplastic buckling load is then estimated by a semi-empirical formula in terms of generalized slenderness ratio using a corresponding plastic load. For the plastic load, the present scheme adopts a procedure that it is calculated by a linear elastic FEM analysis, while an alternative formula for the plastic load is also proposed based on a shell membrane theory. The validity of the estimation scheme is finally confirmed through comparison with the results based on FEM nonlinear analysis. The formulations are so efficient and simple that the estimation may be conducted for preliminary design purposes almost with a calculator. .

Stability analysis of slope in soil with strength mobilization

Considering the strength parameters cohesion c and internal friction angle < of the soil constitutive model are mobilized non-simultaneously. By gradually applying uniform vertical loads on the top of the slope, the progressive failure process of the slope is simulated by the FLAC3D software. The failure state of the slope is judged by monitoring the maximum unbalance force in the slope system, and the slope sliding surface is determined based on the maximum shear strain increment, and the safety factor is calculated by the slope critical height ratio method. The numerical simulation shows that when the strength parameters are not synchronicity come into play, the safety factor is less than that of two cases, which consider the synchronous mobilization of strength parameters and the traditional Strength Reduction Method (SRM). Finally, the influence of residual cohesion and plastic strain threshold on the position of sliding surface and safety factor are discussed by numerical analysis.

In-plane failure mechanisms and strength design of circular steel tubular Vierendeel truss arches with rectangular section

This paper investigates the in-plane failure mechanisms and strength of circular steel tubular Vierendeel truss arches with a rectangular section by using the finite element models. Firstly, the analytical solution for the in-plane elastic buckling load of pin-ended circular steel tubular Vierendeel truss arches with a rectangular section under a uniform radial load is obtained. Then, limiting conditions of avoiding chord local buckling before the global elastic buckling of the arch are also derived. Lastly, the in-plane instability mechanisms and failure modes of the arch under a uniform radial load, a full-span uniform vertical load (FSUVL) and a half-span uniform vertical load (HSUVL) are investigated. It is found that the arch may undergo a global failure mode or three local failure modes under FSUVL and HSUVL. Based on the theoretical and finite element results, a design equation for the global strength of arches subjected to uniform compression is proposed. Strength design equations for global failure and local failure of arches subjected to FSUVL and HSUVL are also proposed. There is a good agreement between the prediction of the proposed design equations and the FE results.

A numerical analysis on the effect of pile head connections on piled raft foundation subjected to vertical and static horizontal load

A numerical analysis has been performed on the piled raft subjected to uniform vertical load and static horizontal load on piled raft foundation. The applied horizontal load was about 6%, 8%, 9% and 12% of vertical applied load. A constant spacing and uniform length to diameter ratio of 3x3 pile group of piled raft models have been adopted in the present study. These models were validated first and then analysis of adopted finite element models resting on cohesion less soil has been carried out. The rigid and hinged pile head connectivity with raft has been considered. The effect of raft-soil stiffness has been adopted in the study. Normalized axial forces, normalized bending moment and normalized lateral displacement of piles throughout its length have been studied. In the case of rigidly connected piles of piled raft, the maximum positive moment of the piles was reached near the top and the maximum negative moment was found at the middle one-third section of the pile depth. The bending moment at the top was zero in case of hinged connected piles of piled raft and the highest positive moment was reached at one-third portion of pile depth from the top. Furthermore, at the bottom end of the pile it decreased to about zero. The influence of increment of horizontal load on vertically loaded piled raft has been examined too. With an increase in horizontal load from 6% to 12% of applied vertical load, the piled raft with rigid connected piles displaced 8 percent −20 percent lower than the piled raft with hinged connected piles at a constant value of relative raft rigidity.

Behavior of a Two-Way Lightweight Steel-Concrete Composite Slab Voided with Thin-Walled Core Boxes towards Sustainable Construction.

High-performance engineered structural systems are crucial for sustainable development in the field of construction. In our previous research, a novel steel–concrete composite beam with transverse and longitudinal hidden girders exhibited good flexural behavior and desirable ductility. However, there is a dearth of studies on the flexural response of a steel–concrete composite slab voided with thin-walled core boxes. Therefore, in this study, we investigated the overarching flexural mechanism of the proposed structure when subjected to uniform vertical loads. The experimental detection results illustrated that the deflection value of the composite beam was 95.75% less than the GB/T 50152-2012 recommendation. Numerical results further validated this observation. The recorded data from the strain profile at the mid-span of the frame girder indicated that there was a considerable membrane effect, which delayed the strain growth of rebars, yielding appreciable bearing capacity. Thus, two original approaches to predicting the ultimate load of this novel structure are proposed, considering limit analysis using the upper-bound method and the membrane effect, with the latter closely linked to the experimental results. The findings can promote the extensive application of similar sustainable systems and inspire further advancements in advanced engineering structures.

A Stress Distribution of Thin Rectangular Steel Wall Under a Uniform Compression

The stress distribution of a steel wall is important in the determination of its shear capacity, e.g. under a wind load or an earthquake load. Since the wall has also to simultaneously carry the gravity load, the influence of this uniform vertical load on the stress distribution is relevant. For a simple-supported thick and square wall, a stress distribution in a cosine form was adequate. However, for an extremely thin wall, a cosine distribution is no longer valid, especially in the post-buckling condition. In this work a three-segment distribution is proposed, i.e. at both edge segments a cosine distribution from edge stress to buckling stress and in the middle segment a constant distribution of buckling stress. To evaluate the proposed distribution, a finite element model using the software ANSYS/LS-DYNA is developed. This model has been verified using the results obtained from own experiments and works done by others. The results show that the proposed stress distribution is able to describe the behavior of thin walls for different aspect ratios and slendernesses. The cosine distribution and the effective width model are also discussed.

A gradient elastic homogenisation model for brick masonry

The elastic macro-mechanical properties of masonry are investigated herein by taking into account the presence of a weakly non-local heterogeneity within a simple gradient elasticity model. Masonry has a heterogeneous structure composed of masonry units bound by mortar. The homogenisation of masonry walls is a challenging task but also a very appealing method for modelling heterogeneity effects exhibited by masonry elements. In particular, it allows the use of smeared mechanical properties, thus avoiding the need of knowing the exact unit-to-unit and joint-to-joint geometry. Current codes provide very simplified empirical expressions to estimate an isotropic elastic modulus of masonry on the basis of its strength properties. The respective equations which do not take into account the anisotropy of masonry, present high scatter resulting in ambiguous safety. The homogenization argument employed in this work is based on a simple procedure utilising Aifantis’ gradient elasticity (GradEla) model. The GradEla model is a straight-forward extension of Hooke’s law by enhancing it with the addition of the Laplacian of the classical expression of the Hookean stress multiplied by an internal length accounting for the local heterogeneity. It has been successfully used to eliminate singularities from dislocation lines and crack tips, as well as in interpreting size effects. However its use in masonry structures has not yet been explored. A first step in this direction is attempted in this paper with emphasis on obtaining practical easy-to-use results rather than exhausting all other possibilities and complexities encountered in GradEla and its generalisation, as well as in more involved homogenisation procedures. In our analysis uniform vertical, horizontal and shear loads are assumed to act on the boundaries of the representative volume/surface element. The components of masonry are assumed to follow a gradient elastic stress distribution resulting in a gradient elastic homogenised model (GREHM). GREHM comprises a set of closed-form concise equations which estimate the elastic moduli in the longitudinal and transverse directions, the shear modulus and the Poisson’s ratio. The aforementioned orthotropic material properties are verified using experimental results and also, compared to other homogenisation models. The validation shows that the proposed equations can effectively estimate with considerable precision the elastic properties of masonry walls. To illustrate the resulting estimation of the orthotropic elastic properties, normalised graphs are provided.

In-plane failure mechanism and stability bearing capacity design of planar plate-tube-connected circular steel arches

ABSTRACT: This study investigates the failure mechanisms and strength of plate-tube-connected circular steel arches. The upper and lower chord of the arch are joined by a series of uniformly distributed steel plates in a radial direction. The chord of the arch mainly bears bending moment, shear force and axial force. The connecting plates mainly resist bending moment, so its failure mechanisms and strength design are different from the traditional truss arch with diagonal tubes and web-opening arches. In this paper, the finite element (FE) software ABAQUS is used to study the in-plane failure mechanism and stability bearing capacity of planar plate-tube-connected circular steel arches, which is subjected to full-span uniform radial load (FSURL), full-span uniform vertical load (FSUVL) and half-span uniform vertical load (HSUVL). The elastic buckling load formula of two-hinged plate-tube-connected circular steel arches is proposed under FSURL.. Also, the limited condition of avoiding local buckling is also proposed under FSURL. The stability bearing capacity design formula of the arch under FSURL is proposed. Studies have shown that under FSURL, the arch will be subjected to global elastoplastic failure, and the upper chord will exhibit a full-section yield at the scope of 1/4 L span and the lower chord will exhibit a full-section yield at the scope of 3/4 L span. Under F(H)SUVL, the global failure mode may occur. The global failure stability bearing capacity design formulas of the arch under FSUVL and HSUVL are also proposed. The FE results are in good agreement with these formulas. Finally, the design suggestions of plate-tube-connected circular steel arches are proposed.