Single Concentrated Load Research Articles

SHEAR STRENGTH OF PERFORATED PLATE GIRDERS WITH INCLINED STIFFENERS

A series of experimental tests on perforated steel plate girders with inclined stiffeners is presented herein. Ten simply supported girders of practical size were tested for failure under a single concentrated load applied at the center of gravity of the section. Circular web openings of various diameters were introduced at the middle panels of the girders. Effects of different inclination angles of intermediate stiffeners on the ultimate load behavior are the main focus of the present study. Five different angles, measured from the bottom flange, were considered in the tests, viz., 90°, 75°, 60°, 45°, and 30°. Variations of strength, failure characteristic, and load-deflection response have been observed. The ultimate strength was found to increase considerably from 21% to 92% as the angle of inclined stiffeners reduced from 90° to 30°.

Experimental Testing of Concrete Bridge-Deck Slabs Reinforced with Basalt-FRP Reinforcing Bars under Concentrated Loads

AbstractAdvances in fiber-reinforced polymer (FRP) technology have led to the introduction of new basalt-fiber-reinforced-polymer (BFRP) bars. This paper presents a research project investigating the behavior of edge-restrained concrete bridge-deck slabs reinforced with BFRP bars. The tests included six full-scale edge-restrained concrete deck slabs simulating a slab-on-girder bridge deck commonly used in North America and one full-scale unrestrained concrete deck slab. The deck slabs measured 3,000 mm long × 2,500 mm wide × 200 mm thick. The test parameters investigated were (1) reinforcement type (BFRP and steel); (2) BFRP bar size (12 and 16 mm); (3) reinforcement ratio in each direction (0.4–1.2%); and (4) edge-restraining [restrained or unrestrained (free)].The slabs were tested up to failure over a center-to-center span of 2,000 mm under a single concentrated load acting on the center of each slab over a contact area of 600 × 250 mm to simulate the footprint of a sustained truck wheel load (87.5-kN ...

FINITE ELEMENT INVESTIGATION OF THIN-WEBBED PLATE GIRDERS WITH INCLINED STIFFENERS

This paper is concerned with the ultimate load behavior of thin-webbed steel plate girders with inclined stiffeners. Non-linear analyses were carried out on the simply supported plate girders using a commercial finite element code, LUSAS. The girders are of practical size and subjected to a single concentrated load applied at the centre of gravity of the section. Effects of inclination degree of stiffeners and central web openings on the performance and behavior of such girders are investigated. Variations of ultimate strength, buckling characteristic and load-deflection response are obtained. The ultimate strength is found to increase significantly when the inclined stiffeners were provided to the girders, regardless the effect of openings in the web.

면외변형하의 압전재료에 대한 침투 쐐기균열

In this study, we analyze the problem of wedge cracks, which are geometrically unsymmetrical in transversely piezoelectric materials. A single concentrated antiplane mechanical load and inplane electrical load are applied at the point of the wedge surface, while one concentrated antiplane load is applied at the crack surface. The crack surfaces are considered as permeable thin slits, where both the normal component of electric displacement and the electric potential are assumed to be continuous across these slits. Using Mellin transform method, the problem is formulated and the Wiener-Hopf equation is derived. By solving the equation, the solution is obtained in a closed form. The intensity factors of the stress and the electric displacement are obtained for any crack length as well as inclined and wedge angles. Based on the results, the intensity factors are independent of the applied electric loads. The electric displacement intensity factor is always dependent on that of stress intensity factor, while the electric field intensity factor is zero. In addition, the energy release rate is computed. These solutions can be used as fundamental solutions which can be superposed to arbitrary electromechanical loadings.

Strength of Jack-Beams with slender webs and mono-symmetric sections

Jack-Beams (J-Beams) are used to support discontinued columns that do not extend to lower floors, satisfying space requirements in large stores and workshops. Often large concentrated loads are acting on the laterally unsupported J-Beam top. Built-up I-sections are often used in designing J-Beams. Lateral-torsional buckling (LTB) is crucial in designing J-Beams as it is one of the main requirements in controlling the ultimate bending strength of steel J-Beams carrying loads on top flange. This study investigates the ultimate bending strength of commonly used J-Beams with different sections and classes including slender webs. A numerical model is developed to accurately estimate the ultimate load of J-Beams. The strengths of the selected J-Beams are calculated for different models of unsupported lengths and different section types according to detailed finite element model (FEM) for this type of system. The goal is to investigate the performance of the J-Beams for the selected section types and beam lengths. Single concentrated loads at the top flange of the J-Beams are applied at the FE models. Imperfections of different values are implemented to examine their sensitivity and to find out their effect on the LTB of J-Beams at failure, and hence, their effect on the ultimate strength of J-Beams. The study also introduces simplified procedure and gives recommendations for designing J-Beams using the numerical results of the selected sections.

A THIRD-GENERATION OPTICAL FIBRE TRANSDUCER FOR LANDSLIDE MONITORING

Monitoring an unstable slope is quite important for environmental safety. Based on our previous studies, this paper presents a third-generation distributed optical fibre transducer. The operating mechanism of this novel transducer was analysed for its response to a single concentrated and uniform load, and a theoretical study was conducted on the elongation of the bottom-surface fibres of a bending resistance model at the phases of linear elasticity and total cross-section cut-off stage. A bending resistance test was conducted when this transducer was grouted with concrete C40 and two types of base materials - expanded polystyrene (EPS) and polyvinyl chloride (PVC). Experimental and theoretical studies results indicate that the minimum diameter of the second coiling of a single mode fibre is more than 20 cm at wavelength 1310 nm. The ratio of the measured value to theoretical value for elongation of optical fibres on the bottom surface is greater than 0.9, indicating significant correlation. The transducer with EPS as its base material provides a better response than the one with PVC, because of its higher initial measurement precision, larger sliding distance, and greater dynamic range. However, sliding is bound to produce shear force; therefore, further research on the performance of the transducer and its grout under shearing loads should be conducted.

Testing of full-scale concrete bridge deck slabs reinforced with fiber-reinforced polymer (FRP) bars

This paper presents an experimental study investigating the behavior of FRP-reinforced concrete bridge deck slabs under concentrated loads. A total of eight full-scale deck slabs measuring 3000-mm long by 2500-mm wide were constructed. The test parameters were: (i) slab thickness (200, 175 and 150 mm); (ii) concrete compressive strength (35–65 MPa); (iii) bottom transverse reinforcement ratio (1.2–0.35%); and (iv) type of reinforcement (GFRP, CFRP, and steel). The slabs were supported on two parallel steel girders and were tested up to failure under monotonic single concentrated load acting on the center of each slab over a contact area of 600 × 250 mm to simulate the footprint of sustained truck wheel load (87.5 kN CL-625 truck). All deck slabs failed in punching shear. The punching capacity of the tested deck slabs ranged from 1.74 to 3.52 times the factored load ( P f ) specified by the Canadian Highway Bridge Design Code (CHBDC) CAN/CSA S6-06. Besides, the ACI 440.1R-06 punching strength equation greatly underestimated the capacity of the tested slabs with an average experimental-to-predicted punching capacity ratio ( V exp / V pred ) of 3.17.

Shear Strength of Fiber-Reinforced Polymer Reinforced Concrete Beams Subject to Unsymmetric Loading

This study is concerned with the determination of the effects of shear span-to-depth ratio (a/d) and beam depth, or size, on the concrete contribution to the shear resistance of beams longitudinally reinforced with carbon fiber-reinforced polymer (CFRP) bars. One of the distinguishing features of the study is the unsymmetrical nature of the applied load, which creates two distinct a/d ratios in the same beam and allows the effect of the a/d ratio on shear strength to be clearly seen. Six simply supported large size CFRP reinforced concrete beams without shear reinforcement were tested, each under a single concentrated load. The test variables were the a/d ratio, varying from 1.0–11.5, and the beam depth varying from 200–500 mm. All the beams failed in shear, but the failure load and location for some of these beams could not be predicted by the shear design recommendations of American Concrete Institute (ACI) Committee 440. The reason is that these recommendations do not account for the effects of a/d and beam size on shear strength. Suggestions are made for the inclusion of these parameters in the shear design equations.

Research on Transverse Load Distribution Factors for Jointless Bridges

AbstractThe FEM of the jointless bridge were established with the program ANSYS considering the soil-structure interaction. The pattern of different loads influencing on the transverse load distribution of the middle section and the change of transverse load distribution factors along longitudinal direction were studied. Different transverse load distribution factors were compared with the simple beam bridge, and the influence of structure parameters was analyzed. The practical tables calculating transverse load distribution factors were provided and validated by the example. The researching results indicate that, transverse load distribution factors can be studied by the transverse distribution influence line of the deflection with the loading format of the single concentrated load adopted for jointless bridge, the transverse load distribution factors of the middle section can be adopted as the one of the all span, that the transverse load distribution factors of the side beam of the jointless bridge is ...

Behavior of Concrete Bridge Deck Slabs Reinforced with Fiber-Reinforced Polymer Bars Under Concentrated Loads

While the expansive corrosion of steel reinforcement is a major concern in reinforced concrete bridge deck slabs, the noncorrosive fiber-reinforced polymer (FRP) composite bars provide an excellent alternative reinforcement. In this paper, the behavior of edge-restrained concrete bridge deck slabs reinforced with glass FRP and carbon FRP bars was investigated. Six full-scale deck slabs 3000 mm long x 2500 mm wide x 200 mm deep were constructed and tested to failure in the laboratory. Three deck slabs were reinforced with glass FRP (GFRP) bars, two deck slabs were reinforced with carbon FRP (CFRP) bars, and the remaining slab was reinforced with steel bars as control. The test parameters were the reinforcement type and ratio in the bottom transverse direction. The deck slabs were supported on two steel girders spaced at 2000 mm center-to-center and were subjected to a monotonic single concentrated load over a contact area of 600 x 250 mm to simulate the footprint of sustained truck wheel load (87.5 kN CL-625 truck) acting on the center of each slab. The experimental results were presented in terms of cracking, deflection, strains in concrete and reinforcement, ultimate capacity, and mode of failure. It was observed that the mode of failure for all deck slabs was punching shear with carrying capacities of more than three times the design factored load specified by the Canadian Highway Bridge Design Code. It was also concluded that the maximum measured crack widths and deflections at service load level were below the allowable code limits. In addition, a new empirical model to predict the punching shear capacity of restrained FRP-reinforced bridge deck slabs was introduced and verified against the available models and experimental results of others researchers. The proposed model showed goad agreement with the available test results.

PARAMETERIZATION OF DAMAGE IN REINFORCED CONCRETE STRUCTURES USING MODEL UPDATING

This paper describes the application of finite element model updating to reinforced concrete beams in order to detect and quantify damage. Three simply supported beams are considered in this study: two of them are subjected to a single concentrated load while the third one to two concentrated loads. The static loading system is applied in different steps up to failure so that dynamic measurements can be carried out after each load step. The measured modal parameters are used afterwards to update a finite element model in order to localize and to quantify the damage. The updating algorithm is based on the sensitivity approach in which the discrepancies between the analytical and experimental modal data are minimized in an iterative manner. A new concept for damage parametrization is introduced. A damage function characterized by three parameters is proposed. In such a function, only three parameters are used to describe the damage pattern of the reinforced concrete beams. These parameters are related to the bending stiffness of the beams and updated so that the measured natural frequencies are reproduced. The results demonstrate the efficiency of the proposed technique to quantify the damage pattern.

Gear Stress Analysis by the Hybrid Finite Element Method. Deviation Technique for the Global Local Finite Element Method.

A new numerical technique using the global local finite element method (GLFEM) has been proposed for analyzing a gear subjected to a single concentrated load. The GLFEM is a kind of deviational technique which combines the conventional finite element solutions and the analytical solution like Kelvin's one. One of the most interesting features of this method is considerable reduction in the data required in the modeling process in comparison to that based only on conventional finite elements. Clearly, the nature of the solution and the degree of approximation depend on the characteristics of the element equations. In this study, although there are many ways of formulation, the deviation technique and hybrid method combining the domain type and boundary type solutions are especially used for formulating the properties of elements. Then the GLFEM formulated in this study is applied to the gear tooth stress analysis to show the validity of this technique.

Service Load Test of 1:3 Scale Shell Bridge Model

Due to lack of maintenance, increase in legal loads, and increased traffic volumes, several thousands of deficient bridges in the surface transportation system needed to be rehabilitated or replaced. One potential solution to several of today's bridge problems is the shell bridge. This system consists of integrated shell-deck concrete segments that are posttensioned together to form a bridge. A 1:3 shell-bridge model was fabricated and service-load tested to determine its behavior when subjected to various load patterns. The model was tested under the effect of single concentrated loads as well as simulated American Association of State Highway and Transportation Officials (AASHTO) HS20-44 truck loading. The model was analyzed using the ANSYS finite element program. The buckling potential due to the posttensioning forces was also investigated with ANSYS. Fabrication and construction of the 1:3 model verified the feasibility of constructing segmental shell bridges. The integrated shell-deck section exhibit...

Moments in Deck Slabs Due to Cantilever Loads

A simplified method is presented for analyzing hogging moments in internal deck slab panels of slab‐on‐girder bridges due to single concentrated loads on the deck slab overhangs. This analysis will be found useful for designing the curtailment of the hogging moment reinforcement extending from the overhang into the internal panel of the deck slab. Tables of coefficients needed for the proposed simplified analysis are provided to cover almost all of the cases likely to be encountered in practice. The tables of coefficients are applicable not only to the analysis of the deck slab in the internal panels but also in the overhangs. These coefficients were developed from the results of a large number of carefully performed finite‐element analysis. A simple technique is also presented, by which the transverse moments in the internal panels and overhangs of deck slabs can be determined when the overhangs are edge‐stiffened.

Non-linear bending of a corrugated annular plate with a plane boundary region and a non-deformable rigid body at the center under compound load

In this paper, based on the non-linear bending theories of isotropic and anisotropic annular plates, the non-linear bending of a corrugated annular plate with a plane boundary region and a non-deformable rigid body at the center has been investigated under the combined action of uniform pressure and a single concentrated load at the center. For two kinds of outer edges, namely, rigidly and loosely clamped edges, analytical solutions of the plate have been obtained by the modified iteration method.

Critical loads of thin-walled beams containing web openings

This paper is concerned with an experimental investigation of lateral buckling behaviour of thin-walled beams of narrow rectangular and I-section containing web openings and subjected to a single concentrated load applied at the centroid of the cross-section. Experiments carried out to determine the effect of openings on the elastic critical load are described. Parameters such as support conditions, size, shape, location and number of openings are considered in the investigation. Experimental critical loads are compared with those obtained numerically using the energy approach. Good agreement between the results has been observed.

Load Capacity of lsotropically Reinforced, Cast-in-Place and Precast Panel Bridge Decks

104 R. E. Klingner Phil M. Ferguson Professor in Civil Engineering The University of Texas at Austin Austin, Texas A 20 x 50 (6.10 x 15.24 m), full scale bridge deck (both cast-in-place and precast panel), detailed using Texas SDHPT provisions for decks with Ontario-type isotropic reinforcement, was constructed in the laboratory. The ultimate load performance of the deck was investigated. Under single and tandem concentrated loads, the deck failed in punching shear. The ultimate concentrated load capacity of the deck was closely predicted by a proposed general punching shear model. Both the current ACI and AASHTO punching shear formulas were very conservative.

Analysis of a beam on random elastic support : Soils Found V29, N2, June 1989, P24-36

Lack of information about the spatial distribution of the modulus of subgrade reaction results in significant uncertainty with respect to the true value of the calculated displacements, shear forces and moments in the analysis of beams of elastic support. In order to incorporate this uncertainty into the analysis, the spatial distribution of the modulus of subgrade reaction is modeled here as a homogeneous low pass normal random function of the space coordinate along the beam, and an approximate solution of the resulting random differential equation is derived. The paper considers the case of an infinite beam acted upon by a single concentrated load. For this case explicit solutions are presented for the spatial distributions of standard deviations of displacements, moments, and shear forces at every point along the beam. In addition the correlation coefficient between displacement at different points is evaluated. This information is sufficient for the determination of probability distributions of settlements, differential settlements, shear forces, and moments, at every point along the beam, thus making it possible to carry out a complete probabilistic design of such beams.(a)

Analysis of a Beam on Random Elastic Support

Lack of information about the spatial distribution of the modulus of subgrade reaction results in significant uncertainty with respect to the true value of the calculated displacements, shear forces and moments in the analysis of “beams on elastic support”. In order to incorporate this uncertainty into the analysis, the spatial distribution of the modulus of subgrade reaction is modeled here as a homogeneous low pass Normal random function of the space coordinate along the beam, and an approximate solution of the resulting random differential equation is derived. The paper considers the case of an infinite bean acted upon by a single concentrated load. For this case explicit solutions are presented for the spatial distributions of standard deviations of displacements, moments, and shear forces at every point along the beam. In addition the correlation coefficient between displacement at different points is evaluated. This information is sufficient for the determination of probability distributions of settlements, differential settlements, shear forces, and moments, at every point along the beam, thus making it possible to carry out a complete probabilistic design of such beams.

Stability of the human spine: a biomechanical study

The influences of curvatures and of physical properties on the mechanical stability of the spine were analysed by means of a three-dimensional, geometrical, nonlinear biomechanical model. According to the model, the initial buckling load decreases with increasing lordotic and kyphotic curvatures. When the body weight is taken into account as a load distributed along the whole spine, the calculated initial buckling load is twice the value that it is in the case of a single concentrated load acting at the top of the spine. Applying the large deflection theory, no relation is found between the increased slenderness of a spine and a ‘buckled’ configuration of a scoliotic spine.