Single Concentrated Load Research Articles

Calculation Method for Structural Dynamics of Material Ropeway under Startup and Shutdown Conditions with Single Concentrated Loads and Distributed Multiple Loads

In light of the unique structural features of material ropeway of transmission line, this paper presents a calculation method for the structural dynamics of material ropeway when subjected to single concentrated loads and distributed multiple loads. Taking into account the geometric nonlinearity and significant flexible deformation features of carrying rope and pulling rope in material ropeways, a finite mass point method is utilized for theoretical derivation to investigate the effects of varying load weights and speeds on tension fluctuations in carrying rope and pulling rope during the startup and shutdown processes. The results indicate that the proposed method can accurately calculate the tension and structural variations in carrying rope and pulling rope of multi-span material ropeway when subjected to single concentrated loads and distributed multiple loads. This method not only satisfies the requirements for transmission line engineering applications but also offers insights into the safe utilization of material ropeway of transmission line.

Behavior study of the steel plate girder with a cellular honeycomb web

Based on the experimental test results of the authors, this investigation is concerned with the finite element analysis to examine and compare the load values and failure modes of the authors’ results. This research was conducted using the Abaqus software. The experimental work included the fabrication of twelve plate girders with honeycomb and flat web plate corrugation patterns, which were then tested under a single concentrated load at the midspan. According to the corrugation dimension or outer honeycomb web thickness, the honeycomb steel plate web girder is divided into three groups (60 mm, 80 mm and 100 mm). The specimens also involved plate girders with a flat web. The specimens were created with three lengths (600 mm, 1,200 mm and 1,800 mm). The Abaqus software was used in finite element models to simulate the concentrated load. The numerical results demonstrated that the 60 mm thick honeycomb web provides a greater load-bearing capacity and shear strength than other girders. The 20 mm honeycomb corrugation on the steel plate girder indicates the increased and improved shear resistance. The conclusion was that as the width of the corrugation increased, so did the steel web’s ultimate load and shear strength, resulting in a positive relationship between the critical shear buckling load of the web and the moment of inertia at the strong axis. When the dimension of the corrugation increases, the moment of inertia of the Y axis (Iy) decreases; thus, the plate girder will fail with a less critical buckling load (Pcr). Also, it can be concluded that as the steel plate thickness of the honeycomb web increases, the shear resistance increases as well. However, the spacing between the intermediate stiffener or the horizontal spacing of the web panel can enhance the shear resistance of honeycomb web girder if it was decreased due to increasing the action of tension field force that resists the diagonal tension developed at the web panel by the applied midspan concentrated force.

Flexural behavior of prefabricated high-strength steel-concrete composite beams with steel block connectors

To study the flexural behavior of high-strength steel-precast concrete slab (HSS-PCS) composite beams with steel block shear connectors (SBSCs), seven HSS-PCS beam specimens subjected to a single concentrated load were tested, considering the parameters of concrete strength, steel strength, and shear connection degree. Through this experiment, the primary specimen information of vertical load, deflection, mid-span section strain, and interface slip were established. The HSS-PCS composite beam with steel block shear connectors has good overall working performance with high bending capacity and stiffness, and three failure modes are recorded including cracking at the tongue and groove joints, crushing of mid-span concrete slab, and failure of shear connections. The composite beams show a high degree of brittleness under these three failure modes, which should be considered in practical design. The existing design theory and standards are generally suitable for predicting the bending capacities of the novel prefabricated composite beams, in which the Eurocode 4 is slightly conservative, while the Chinese design specification has relatively good prediction results for the composite beams with partial shear connections.

Impact of sulfate damage on the behavior of full-scale concrete bridge deck slabs reinforced with FRP bars

This paper is aimed to analyze the performance of reinforced-with-FRP, sulfate-damaged concrete bridge deck slabs under concentrated loads, using the nonlinear finite element analysis (NLFEA) method. For experimentation purposes, twenty-seven full-scale models have been prepared to simulate concrete bridge deck slabs, with a length of 3000 mm and a width of 2500 mm. The parameters of the study were: (i) type of reinforcement, as three types were tested: glass FRP (GFRP), carbon FRP (CFRP), and steel; (ii) bottom transverse reinforcement ratio (ρ = 0.38, 0.46, and 0.57); and (iii) sulfate damage level, which consisted of three levels: Level 0 (undamaged), level 1 (73 days), and level 2 (123 days). All of the slabs models were equipped with two parallel girders of steel as supporters. To be able to analyze the models' performance up till failure, the load exerted by sustained truck wheels (87.5 kN CL-625 truck) was simulated by subjecting each slab model to a monotonic single concentrated load, with a contact area of 600 × 250 mm, at the center of the models. The simulated models encountered a punching shear mode of failure. The analysis showed that the models that were strengthened with CFRP and GFRP bars exhibited a remarkable improvement in the models': ultimate load, elastic stiffness, post-cracking stiffness, elastic energy absorption, and post-cracking energy; whereas, there was less influence on the models' ultimate deflection, compared to the ones strengthened with steel.

A FUNDAMENTAL SOLUTION FOR AN ANISOTROPIC PLATE ON AN INERTIAL FOUNDATION

The work is devoted to the construction of a new fundamental solution for a thin elastic anisotropic unbounded Kirchhoff plate on an inertial Winkler foundation. The fundamental solution is a function of the normal movement of two spatial coordinates and time in response to the impact of a single concentrated load, mathematically modeled by the Dirac delta function. The anisotropy model considered in this article has one plane of symmetry that geometrically coincides with the median plane of the plate and is characterized for the Kirchhoff plate model by six independent components of the tensor of elastic constants of the material. The problem statement includes the equations of motion of an anisotropic plate in displacements and initial conditions. The solution of the corresponding initial problem for the fundamental solution is constructed using integral Laplace transformations in time and two-dimensional integral Fourier transform in spatial coordinates. The inverse integral Laplace transform is found analytically with a preliminary analysis of the invertible function. The original fundamental Fourier solution is constructed using the numerical method of integrating rapidly oscillating functions. The parameters of numerical integration are calculated with a given accuracy when analyzing the quality of the desired functions by a continuous norm. For the constructed new fundamental solution, a numerical analysis of the nature of the propagation of nonstationary disturbances is carried out, and the influence of the parameters of the inertial Winkler foundation on the behavior of the normal deflection of an anisotropic plate in time at the point of action of the delta function is investigated. The asymmetric nature of unsteady plate oscillations consistent with the model of the elastic medium under consideration is demonstrated. The constructed fundamental solution makes it possible to investigate the nonstationary normal deflection of an anisotropic plate on an inertial basis under the action of arbitrary loads using an integral operator of the convolution type in spatial coordinates and time. In addition, the fundamental solution has versatility with respect to the properties of the plate materials and the parameters of the foundation, namely: isotropic, transversally isotropic and orthotropic materials can act as the plate material. In this case, the foundation may be inertialess or absent altogether.

Theoretical prediction of the shear strength of reinforced concrete slabs under concentrated loads close to linear supports

A mechanical model has been developed by the authors in order to predict the shear strength of reinforced concrete slabs under concentrated loads close to linear supports. The model takes into account a significant number of variables involved in the phenomenon, such as the clear shear span, the concrete compressive strength, the reinforcement ratio, the effective depth, the load spreading angle, the size effect and the size of the loaded area. It is applicable to simply supported slabs, cantilever slabs and situations with partial restraint to the rotation, such as intermediate supports. It has been validated with a database of 90 shear test in slabs subjected to a single concentrated load in different supporting conditions, yielding results on the safe side and showing low scatter. A parametric analysis of the model is also presented, detailing how the different involved variables affect the shear strength. These results, along with the simplified expressions for the shear strength calculation, provide a useful tool for the assessment of the shear strength of reinforced concrete solid slabs in daily engineering.

Nonlinear finite element analysis of full-scale concrete bridge deck slabs reinforced with FRP bars

Bridges with reinforced concrete deck slabs are more vulnerable to environmental-induced deterioration mainly due to corrosion. Carbon and glass fiber reinforced polymer (FRP) bars are getting attention as an alternative to steel bars to enhance the overall performance of the concrete bridge deck slabs and minimize corrosion-induced deteriorations. This study presents a 3D nonlinear finite element analysis (NLFEA) simulating the response of full-scale concrete bridge deck slabs reinforced with FRP bars. A control slab model was developed initially and properly calibrated and validated against published independent experimental results. A parametric study was then conducted through creating 27 NLFEA models with different parameters: concrete compressive strength, reinforcement type (glass FRP, carbon FRP, and steel), and bottom transverse reinforcement ratio. Monotonic single concentrated load was applied at the center of the concrete deck slab over a contact area of 600 mm × 250 mm, simulating the footprint of sustained truck wheel load. The CFRP and GFRP bars reinforcement of bridge deck slabs had superior effects on the ultimate load, elastic stiffness, post cracking stiffness, elastic energy absorption and post cracking energy and a little impact on ultimate deflection compared with steel reinforcement. Punching shear failure with a very similar cracking pattern was observed almost in all slabs and the bottom transverse reinforcement ratio is the main parameter affecting the tensile strains. For all slabs reinforced with GFRP and CFRP bars, the maximum measured strains in the bars at failure were less than 50% of their ultimate strain. Increasing concrete compressive strength will increase the ultimate load capacity and corresponding deflection of the slab.

Analytical Method for Local Damage of Beams under Moving Vehicle Loading

In order to accurately identify damage of bridge under natural excitation, an analytical solution of local stiffness of simply supported beam structure is established by using structural mechanics method through establishing the moving load model of simply supported beam. On this basis, an accurate identification method of local damage of beam structure under vehicle load is proposed. Firstly, the local bending stiffness is described in terms of equal length intervals. Secondly, the corresponding loading methods are established for single concentrated load and two-axle vehicle respectively, and the local bending stiffness values of each interval are solved by analytic equation established by node displacement. Damage information can be identified by comparing the flexural stiffness values of simply supported beams before and after damage. Based on the discreteness of local bending stiffness of simply supported beams and the change of local bending stiffness caused by damage, the location and degree of local damage of beams can be accurately identified.

Punching Shear Performance of Steel Fiber Reinforced Geopolymer Concrete Slabs

This article provides performance of two way slabs under punching shear. The two way slabs are cast with dimensions of 600x600x75mm and to cast the slabs geopolymer concrete along with micro (13mm length (small fiber)) and macro steel fibers (50mm length (big fibers)) were used. Total four mixes were taken to the present study and for each mix three slabs were cast. The first mix without fibers, second mix with small fiber, the third mix with big fiber and fourth mix with small and big fibers are taken to the present study. All the slabs were tested under single point concentrated load and load is placed at the center of the slab. From the experimental investigation it is obvious that, the slab with combination of small and big fibers showed superior performance among all and it showed 157.1% higher strength carrying capacity than the slab without fibers.

Evaluation of Strengthening Steel Beams Using the Technique of Carbon Fiber Confinement by a Steel Plate (CFCSP)

Abstract This research concentrates on evaluating the effect of using two new techniques for strengthening steel beams with carbon fiber–reinforced polymer (CFRP) strips on the structural behavior of these beams at service and ultimate load stages by using a confining steel plate in two different configurations. Five steel beams with lengths of 1,500 mm were tested under a single concentrated load at midspan: the first (nonstrengthened) beam was used as a reference beam, the second beam was strengthened by only a CFRP strip located at the bottom flange (tension face), and the third beam was strengthened by only a steel plate, which is also located at the bottom flange. The first technique is represented in the fourth beam, which was strengthened by a CFRP strip confined by a steel plate welded at its ends, whereas the second technique is obtained by an amendment done on the first technique and is represented by the fifth beam, which was strengthened by a CFRP strip with the confining steel plate (welded at its ends) and glued with the CFRP strip by a suitable epoxy adhesive. Test results have shown that the first technique has led to less deflection, less tensile strain, and a higher yield load at the service load stage (i.e., elastic region), whereas the second modified technique has led to a further decrease in deflection and tensile strain and an additional increase in yield and ultimate loads, and both of those outcomes were higher than the algebraic sum of the increases resulting from beams strengthened by a “steel plate” and “CFRP strip” individually.

Interfacial stresses in reinforced concrete cantilever members strengthened with fibre-reinforced polymer laminates

Fibre-reinforced polymers have been increasingly used to strengthen reinforced concrete structures. However, premature brittle debonding failures may occur at the ends of externally bonded fibre-reinforced polymer laminates due to interfacial stress concentrations caused by stiffness imbalances. Although many studies exist on fibre-reinforced polymer-strengthened simply supported beams and slabs, the interfacial stress distributions in fibre-reinforced polymer-strengthened cantilever members are very different from those in simply supported members. Based on the assumptions of linear elasticity, deformation compatibility and static equilibrium conditions, the interfacial stresses in fibre-reinforced polymer-strengthened reinforced concrete cantilever members under arbitrary linear distributed loads were analysed. In particular, closed-form solutions were obtained to calculate the interfacial stresses under either a uniformly distributed load or a single concentrated load located at the overhanging end of the cantilever member. Existing test results on cantilever slabs strengthened by carbon fibre–reinforced polymer sheets were used to verify the model. According to the parametric analysis, the maximum interfacial stresses can be reduced by decreasing the fibre-reinforced polymer thickness, increasing the fibre-reinforced polymer bonding length and increasing the adhesive layer thickness, and by using less rigid fibre-reinforced polymer laminates with high tensile strengths. These results are useful for engineers seeking to optimize strengthening design parameters and implement reliable debonding prevention measures.

Fatigue Testing of Transversely Prestressed Concrete Decks

In the Netherlands, slab-between-girder bridges with prestressed girders and transversely prestressed decks in between the girders require assessment. Static testing showed that compressive membrane action increases the capacity of these structures and that the decks fail in punching shear. The next question is if compressive membrane action also increases the capacity of these decks under repeated loads. Therefore, the same half-scale bridge structure as used for the static tests was subjected to repeated loads at different fractions of the maximum static load, different loading sequences, and for single and double concentrated loads. A relationship between the load level and number of cycles at failure (S-N curve) for the assessment of these bridges is proposed, but the influence of the loading sequence was not successfully quantified yet. The conclusion of the experiments is that compressive membrane action enhances the punching capacity of transversely prestressed thin decks subjected to repeated loads.

Kelakuan Beban Muktamad Galang Plat Komposit Keluli-Konkrit dengan Pengukuh Condong

This paper focuses on the ultimate load behaviour of steel-concrete composite plate girders with inclined stiffeners. For this research, non-linear modelling and analyses were carried out on ten simply supported composite plate girders using a commercial finite element software, LUSAS. The girders are of practical design size and subjected to a single concentrated load applied at the centre of the girder span. Effects of different inclination angles of intermediate stiffeners and web-depth to thickness (d/t) ratios on the post-buckling behaviour of the girders are investigated. Five different angles of stiffeners, measured from the bottom flange, were considered in the research, viz., 90°, 75°, 60°, 45° and 30° while the web thickness, tw used in this study are 2 mm and 3 mm. With the effects of such inclinations, the variations of ultimate load, load-deflection response and failure characteristics were obtained. The load carrying capacity was found to rise significantly of about 32%, as the angle of inclination reduced from 90° to 30°. The ultimate strength of the composite girder also shows a maximum increase of 28%, when the web thickness, tw rises from 2 mm to 3 mm.

Effect of (B/D) ratio on ultimate load capacity for horizontally curved box steel beam under out of plane concentrated load

The intended of this research is to prepare an analytical study to investigate the best width to depth section ratio (b/d) of horizontally curved steel box beam with constant cross-sectional area (without stiffeners) under single concentrated load at mid-span of the beam. The research adopts three – dimensional nonlinear finite element analysis of steel box -section horizontally curved beams exposed to static load. The isoparametric brick element of twenty-node has been used to represent the steel element; also, the yield criterion used to compute the stress level of plastic deformation is Von-Mises. The simulation model of the behavior of steel under tension and compression stresses is elastic-perfect plastic. A semi-circular two-span continuous horizontally curved steel box beam was fabricated and tested under two point loads at midspan of the beam, the results was compared with the results of the computer program (NFHCBSL) used in this study. In general, it is found that the adopted finite element model to predict the structural response of horizontally curved steel box beam has a good agreement with the test results concerning estimate load-deflection response.The effect of b/d ratio is considered by taken different values (20–100) % with the identical area of cross-section. Also, the effect of curvature was studied by considering different values from beam with half circle to straight beam. The results appear that the best (b/d) ratio is in between (0.3 and 0.4) at curvature between (0° and 90°) and the best (b/d) ratio is in between (0.4 and 0.5) at curvature between (90° and 180°). Also, the result showed that the decrease in carrying load capacity as the beam curvature increased is independent on the value of b/d ratio.

The spread of concentrated loads on AAC using digital image correlation techniques

AbstractBackgroundThere has debate around the way in which the spread of concentrated loads is assumed in masonry codes in masonry. In addition, there is no data available to assess the spread of loads across the joints of storey height AAC elements.AimsThe aim was to reconfirm the angle of spread in masonry from a concentrated load and to assess whether this could be applied to storey height elements.Materials and MethodsA project took to study the strain development in AAC masonry walls subjected to a single concentrated load. A second project studied walls made from AAC storey height panels subjected to uniform vertical load on one element within a set of 3. Test work was carried out using Digital Image Correlation (DIC).ResultsThe results clearly justified the current design assumptions in Eurocode 6. In the case of storey height elements, the load effects were transmitted across the vertical joint.ConclusionsThe tests carried out on AAC masonry showed that the spread of concentrated loads is in line of the current recommendations of Eurocode 6. The results justify the when designing with storey height elements, for vertical loading the principals of masonry design can be used.

Investigation of the behaviour of SCC bridge deck slabs reinforced with BFRP bars under concentrated loads

Self-compacting concrete (SCC) with high-volume industrial wastes, such as fly-ash, reinforced with fibre-reinforced polymer (FRP) bars is anticipated to address the concerns on the usage of traditional reinforced concrete structures, such as corrosion of internal steel reinforcement, costly repair and development to low-carbon footprint infrastructures. However, few studies deal with the combined use of these sustainable materials and this has been the key motivation of this undertaking. This paper presents an experimental study investigating the behaviour of SCC bridge deck slabs reinforced with basalt fibre reinforced polymer (BFRP) bars, which is aimed at extending previous research using the combination of BFRP reinforcement and SCC in deck slabs of a real bridge named as Thompson Bridge. A total of six half-scale deck slabs were conducted and tested up to failure over single concentrated loads acting on the centre of each slab. The observed model failure for all the test deck slabs was punching failure. The punching capacity of the test deck slabs was validated with the predicted capacity from the existing theoretical methods in the literatures. The experimental and analytical results are discussed and conclusions on the behaviour of the BFRP reinforced SCC deck slabs are presented.

The interaction of periodically distributed parallel cracks in anisotropic materials subjected to concentrated loads

Parallel median cracks can be generated on the subsurface layer of brittle materials in engineering. The interaction of periodically distributed parallel cracks in an infinite anisotropic material subjected to a concentrated load is examined. The interaction problem is reduced to the solution of a longitudinal crack in a plate strip with zero normal displacement of longitudinal edges. Solutions for the Mode I stress intensity factors (SIFs) at the tips of the crack under a single concentrated load are found by the superposition of the SIFs due to the two pairs of concentrated loads, symmetric and anti-symmetric loads. Besides, the solutions of the parallel cracks under three kinds of distributed loads with a power function form are obtained using Green’s function. Results show that the SIFs increase gradually with the increase of the normalized distance between the parallel cracks, which is the cracks shielding effect.

Flexural characteristics of lightweight ferrocement beams with various types of core materials and mesh reinforcement

Sixteen reinforced concrete beams having the cross-sectional dimensions of 100 × 200 × 2000 mm and clear span of 1800 mm were cast and tested until failure under a single mid-span concentrated load. Ferrocement beams in this research contained either an Autoclaved Aerated lightweight brick Core (AAC), Extruded Foam Core (EFC), or a Lightweight Concrete Core (LWC); and were reinforced with either Expanded Metal Mesh (EMM), Welded Wire Mesh (WWM) or Fibre Glass Mesh (FGM). Structural behaviour of studied beams, including first crack, ultimate load, deflection, ductility index, strain characteristics, crack pattern and failure mode were investigated. Experimental work results showed that ferrocement beams exhibited higher ductility indices than those of the control normal and lightweight test beams to different degrees. Ferrocement beams made of EFC core generally gave the lowest ductility index while the highest ductility index was found for beams made of AAC and LWC cores. Ferrocement beams demonstrated better crack control and did not undergo spalling as opposed to the conventional beams. Specimens reinforced by EMM showed better ductility than those reinforced by WWM and even after increasing the reinforcement ratio of WWM, the situation did not change. Specimens reinforced by FGM had the lowest ductility compared to specimens reinforced by steel mesh. Cracks were found to develop more rapidly in beams reinforced by EMM, while beams reinforced by FGM exhibited the least amount of cracks. The results of this research showed that ferrocement beams of light weight cores may be promising as an alternative to conventional beams and may be viable alternatives especially for low cost residential buildings.

Distribution of peak shear stress in finite element models of reinforced concrete slabs

Existing reinforced concrete solid slab bridges in the Netherlands are re-assessed for shear based on a Unity Check: the ratio of the shear stress caused by the applied loads to the shear capacity of the concrete cross-section. The governing shear stress resulting from the self-weight, weight of the wearing surface, distributed and concentrated live loads, can be determined with a simplified spreadsheet-based method, the Quick Scan (Level of Assessment I) as well as with a linear finite element model (Level of Assessment II). When a finite element model is used, a distribution of shear stresses over the width of the slab bridge is automatically found. To compare the governing shear stress caused by the loads to the shear capacity, it is necessary to determine over which width the peak shear stress from the finite element model can be distributed. To answer this question, a finite element model is compared to an experiment. The experiment consists of a continuous, reinforced concrete slab subjected to a single concentrated load close to the support. Seven bearings equipped with load cells that measure the reaction force profile along the width of the slab are used to compare to the stress profile obtained from the finite element model. From this analysis, it is found that the peak shear stress in a linear finite element model can be distributed over 4dl with dl the effective depth to the longitudinal reinforcement of the slab. The comparison of measured reaction force profiles over the support to the stress profile from a finite element model results in a research-based distribution width that replaces the rules of thumb that were used until now.

Extended Strip Model for slabs subjected to load combinations

The loads that are used for the assessment of existing reinforced concrete slab bridges are the self-weight, superimposed loads, and distributed and concentrated live loads. As such, the shear capacity of reinforced concrete slabs under a combination of distributed and concentrated live loads is a topic of practical relevance. For slabs subjected to a single concentrated load, a plastic model for assessment exists: the Extended Strip Model, developed based on the Strip Model for concentric punching shear. A further adaptation of the model to assess slabs subjected to distributed and concentrated loads is presented in this paper. The proposed model is compared to experiments on slabs subjected to a single concentrated load and a line load. The conclusion of this comparison is that the Extended Strip Model results in a safe estimate of the maximum concentrated load on the slab, and that the method can be used for the assessment of existing bridges subjected to heavy truck loads.