Single Layer Of Reinforcement Research Articles

Wire laser additively reinforced blanks: Effect of the laser power on the bending strength of a single layer reinforcement

This study investigates the application of Wire Laser Metal Deposition (w-LMD), a form of Directed Energy Deposition (DED) additive manufacturing, to enhance the production process of automotive components, specifically through the development of patchwork blanks with localized reinforcements. The research focuses on reinforcing 22MnB5 steel sheets with beads of 316L steel using a laser beam at various power levels, aiming to achieve maximum strength with minimal use of material. The resulting components, referred to as wire-Laser Additively Reinforced Blanks (w-LARB), demonstrated a substantial increase in strength, up to 87%, as verified by bending tests. Notably, the study reveals that a relatively low laser power can still yield significant mechanical improvements, underlining the efficiency of the process in terms of material usage and energy consumption. Furthermore, the high repeatability of the w-LMD process confirms its potential for widespread industrial adoption in automotive manufacturing.

Influences of number of geosynthetic reinforcement layers on soil arching under cyclic loading

Geosynthetic-reinforced pile supported (GRPS) embankments have been widely used in highways and railways on soft subsoil. During the operation period, these embankments are often subjected to cyclic loading, such as traffic loading. Considering that soil arching is a key load transfer mechanism in these embankments, the development of soil arching under cyclic loading is vital important to operational safety of these embankments. Conventional trapdoor system cannot represent actual conditions of soil arching in GRPS embankments because it have a forcibly-moved trapdoor and cannot simulate load-induced subsoil settlement. Hence, this paper used a self-moving trapdoor supported by compression springs that moved up and down dependent on its overburden pressure. To investigate influences of number of geosynthetic reinforcement layers on soil arching under cyclic loading, two self-moving trapdoor tests were conducted, including a single layer and two layers, where the total reinforcement stiffness were approximately same. The trapdoor test results show that the inclusion of two reinforcement layers with a fill layer of a certain height in between reduced surface settlement of the fill and tensile forces of reinforcement, as compared with a single reinforcement layer. It also enhanced soil arching effect and improved the stability of soil arching under cyclic loading.

IMPROVEMENT OF SOIL USING GEOGRIDS TO RESIST ECCENTRIC LOADS.

IMPROVEMENT OF SOIL USING GEOGRIDS TO RESIST ECCENTRIC LOADS.

DIC assessment of foundation soil response for different reinforcement between base and soft subgrade layer – Physical modeling

This paper presents insights from small-scale model tests on statically loaded strip footing on dense base sand supported by a single reinforcement layer. The selected reinforcement includes various lengths of wire mesh and a non-woven geotextile placed on soft subgrade sand. The influence of these inclusions on base and subgrade response (deformations and failure mechanism) is evaluated from the displacement pattern obtained by the digital image correlation (DIC) technique. The benefits of the reinforcement and geotextile were assessed by comparing the results obtained for the improved and unreinforced soil model. Additionally, the confining effect of the reinforcement was experimentally analyzed by comparing the sand displacements around the wire mesh reinforcement with different aperture geometry and geotextile without apertures. These systematically selected reinforcement geometries enabled the investigation of the aperture size influence on base and subgrade behavior during surcharge loading. Results confirm the contribution of reinforcement inclusions to the improved behavior of base and subgrade layers compared to the unreinforced soil. The test results with different reinforcement confirm the influence of the aperture geometry on the model response during the surcharge load application. Compared to large apertures, enhanced confining and membrane actions were obtained for reinforcement with relatively small apertures.

Torsional behavior of GFRP-reinforced concrete pontoon decks with and without an edge cutout

Using glass fiber-reinforced polymer (GFRP) bars in precast concrete pontoon decks in aggressive marine environments would eliminate corrosion problems encountered with steel reinforcement. Although wave action usually subjects pontoon decks to torsion, but little is known about the behavior of such structures. Moreover, nothing is known about the effects of cutouts on the torsional behavior of pontoon decks. This study experimentally investigated the torsional behavior of GFRP-reinforced concrete (RC) pontoon decks in terms of the effect of edge cutouts, reinforcement-bar distribution, and rotation direction. The results show that the bar configuration affected the failure behavior and torsional capacity of the GFRP-reinforced concrete decks under torsion. The decks with double-layer reinforcement exhibited slower and narrower cracking growth in the post-cracking stage than the decks with single-layer reinforcement. In addition, the edge cutouts reduced the cracking torque of the solid rectangular decks by an average 17%. The torsional behavior of the GFRP-reinforced planks can be accurately described by the ACI318-14 equation in the cracking stage, while the decks’ post-cracking torsional rigidity can be predicted accurately from the contribution of the GFRP bars.

Experimental and numerical modelling studies of slender reinforced concrete walls with single-layer reinforcement in Peru

The deficit in affordable residential construction in Lima has generated the construction of several mid to high-rise buildings using the structural system of Slender Reinforced Concrete (RC) Walls. In Peru, this system is known as ‘walls of limited ductility’ and their main characteristics are a fast construction time and an affordable price. Due to the expected non-ductile behaviour, Peruvian RC slender wall buildings follow the same seismic design criteria as traditional RC wall buildings but with a smaller reduction factor of elastic seismic forces and minor permissible story displacement drift. However, there is limited experience of the seismic response of such buildings in severe earthquakes and seismic design criteria have been obtained from just a few experimental tests. This work presents an experimental program of cyclic in-plane testing, developed at the Pontificia Universidad Católica del Perú (PUCP) to obtain more knowledge about the lateral behaviour of typical Peruvian slender walls. According to quasi-static tests, the slender walls reached a maximum story drift of 1.27% after damage occurred, including diagonal tension, diagonal compression, sliding shear, concrete crushing, and buckling of the vertical reinforcement. Experimental results for the slender RC walls were computed to obtain the Damage States, Equivalent Lateral Stiffness (Keff), Ductility (μ), Equivalent Damping Ratio (ξeq) and Bending/Shear/Sliding deformations. In this work, a calibration process on numerical models was developed using OpenSees software. This work shows that slender RC walls in Peru show the typical hysteretic response of structural walls until a maximum drift of 1.27%, despite their deficiencies in slenderness, squat geometry, and the absence of confinement zones.

Simulation of the crack width in reinforced concrete beams based on concrete fracture

The concrete cracking is simulated by the finite element method combined with the constitutive model based on the nonlinear fracture mechanics. The model uncertainties for mean and maximum crack widths are found by comparing the simulated crack widths with data obtained by laboratory testing of 18 reinforced concrete beams. The reinforcement arrangement, dimensional simplification, and numerical discretisation effects on the model uncertainty are investigated. Two reinforcement types, i.e. steel and glass fibre-reinforced polymer bars, are considered. The shrinkage effect on the cracking predictions is included. The fracture energy parameter according to fib Model Code 2010 is used in the simulations. The numerical model offers an adequate prediction of crack widths for the beams with a single layer reinforcement and exhibits less accuracy for the multilayer bar arrangement. The presented numerical model represents an advanced tool for the crack width assessment in the design of reinforced concrete structures in serviceability limit states.

Experimental Study of Strength Development in Black Cotton Soil and Granular Material Reinforced with Geogrid and Non-Woven Geotextile

Reinforcement of flexible pavements using geosynthetics is gaining widespread application. However, there is inadequate understanding of strength development for non-woven geotextile and geogrid as reinforcement in Black Cotton Soil (BCS) and granular material in relation to cement stabilization method. Therefore, this paper presents experimental study to investigate strength development for BCS and granular material reinforced with geogrid and non-woven geotextile using California Bearing Ratio approach. The categories of samples tested were; neat, reinforced and cement stabilized. All samples were tested after 4 days’ soak. Placement of reinforcement material in BCS was done at 0.3H and 0.6H for single layer reinforcement while for double layer reinforcement, it was done at both 0.3H and 0.6H. In granular soil, single layer reinforcement condition only was considered at 0.2H, 0.4H and 0.6H. Cement stabilization for both BCS and granular soil was done by the following percentages of cement increment; 1%, 2%, 3% and 4%. From the study, the strength improvement considering single layer reinforcement by geogrid and non-woven geotextile in BCS was 37.5% and 45% respectively. In granular material, CBR strength increased by 21% and 14% due to geogrid and non-woven geotextile respectively. Percentage increase in CBR of reinforced BCS corresponded to that of over >1% cement stabilization. To further enhance decision making between these strength development alternatives, it is recommended to advance it to cost analysis.

Seismic performance of mid-rise thin concrete wall buildings lightly reinforced with deformed bars or welded wire mesh

The increasing demand of housing in urban areas in Latin America has driven the construction of a significant number of buildings using reinforced concrete (RC) walls with thickness equal or lower than 100 mm, with a single layer of reinforcement provided by a welded-wire mesh (WWM) or by deformed bars (DB). Several concerns related to the lack of ductility, scarce evidence on its behavior during earthquakes, and the lack of clarity of design guidelines in earthquake-resistant codes for this structural system have risen in recent years. This research aims at providing evidence on the seismic risk of thin concrete wall buildings reinforced with two types of reinforcement. A six-story building, constructed in Bogotá, Colombia with walls having 100 mm thickness and detailed with WWM is used as case study. After gathering relevant information from the building structural drawings, a nonlinear model was created in OpenSees using the shear-flexure interaction multiple vertical line element (SFI-MVLEM). To evaluate the effect of steel ductility, a second benchmark model of the studied building was created using deformed bars (DB) as reinforcement. Incremental dynamic analyses were conducted on the models using the far field ground motion suite provided by the FEMA P-695 and a set ground motions for subduction zones, which served as input for the development of fragility functions for the building. The results show that the fracture of reinforcing steel is a frequent failure mode of the building reinforced with WWM, whereas the failure of the building reinforced with DB was controlled by the drift limit of the walls. The findings also show that probabilities of failure for the ground motions scaled to the maximum credible earthquake are 41% and 25% for the building reinforced with WWM and DB, respectively. These large probabilities suggest that the use of thin RC walls for mid-rise buildings should be limited in seismic prone areas, especially those detailed with WWM.

Behaviour of geocell-reinforced strip footings on slopes

ABSTRACT This study presents the results of a series of reduced scale model tests carried out to investigate the bearing capacity and displacement behaviour of strip footings resting near both unreinforced and geocell-reinforced sand slopes. Impacts of some contributing factors such as slope angle, depth of geocell embedment, geocell pocket size and the arrangement of double layer reinforcement are presented and discussed thoroughly. Results indicate that placing a single geocell layer at a depth to footing width ratio of 0.1 (d/B = 0.1) leads to the highest bearing capacity and the lowest settlement ratio. It was observed that steepening the reinforced slope always reduces the bearing capacity and this reduction is remarkable if the slope angle approaches the soil internal friction angle. The optimum depth of the first geocell layer (µ) in a double-layer reinforced slope was found to be approximately 0.5B. At large settlements (s/B > 25%) double geocell reinforcement is always superior to single-layer reinforcement. However, at smaller settlements (s/B < 15%), double geocell reinforcement is effective provided that the spacing of the geocell layers is smaller than 0.5B.

RC U-shaped walls subjected to in-plane, diagonal, and torsional loading: New experimental findings

Although reinforced concrete U-shaped walls are popular in construction practice internationally, there is a paucity of experimental research investigating the seismic performance of such salient elements. The present paper summarizes an experimental campaign on two slender U-shaped reinforced concrete walls detailed with a single-layer of reinforcement. State-of-the-art instrumentation was used to capture the three-dimensional displacement field of the wall surfaces using digital image correlation techniques. Experimental findings are presented, including strain profiles, equivalent plastic hinge lengths, longitudinal strains at the base, cracking distributions and widths, and out-of-plane deformations. Approximately half of the yielding zone length was found to be equal to the equivalent plastic hinge lengths, which were found to decrease as a function of drift. The longitudinal strains at the base of these walls showed some shear lag effects when subjected to in-plane or diagonal loading. For most directions of loading, the largest crack widths were found to be associated with flexural-shear or shear cracks. When subjected to a pure torque, the vertical strain distribution at the base of the wall correlated with the theoretical distribution for an open section governed by warping torsion. The out-of-plane deformations were primarily concentrated within a small region towards the ends of the flanges prior to the local buckling failures that were observed experimentally.

Seismic performance of slender RC U-shaped walls with a single-layer of reinforcement

Reinforced concrete walls are commonly used to resist the lateral loading induced by wind and earthquake actions. While most walls include two vertical reinforcement layers, some regions of the world construct slender, non-rectangular concrete walls with a single vertical layer of reinforcement. The seismic performance of such elements is largely unknown given the paucity of experimental research. This paper presents the results of two slender reinforced concrete U-shaped walls tested at the Earthquake Engineering and Structural Dynamics Laboratory (EESD Lab), École Polytechnique Fédérale de Lausanne (EPFL) in Switzerland. Both wall specimens, designed similar to construction practice in Colombia, were tested using quasi-static cyclic loading to observe if out-of-plane instability would develop when deformations were limited to prevent the flange boundary ends crushing. Initial failure of both wall specimens corresponded with local out-of-plane buckling in the boundary ends of the flanges occurring on load reversal. The buckling lengths were approximately 700–800 mm, which corresponded to 44–50 bar diameters. The crack patterns were observed to be steepest in the web of the walls, demonstrating the increased shear demand in comparison to that of a rectangular wall. Both wall specimens reached ultimate drifts larger than 2.5–3.0% before global failure occurring in the web-flange intersection due to crushing. A small twist was subjected to one of the walls when centered and loaded diagonally, which showed that the decay in torsional stiffness is proportional to the decay in translational stiffness.

Effect of Multi-Directional Reinforcements on the Settlement and Heave Characterstics of Foundations on Sand

Laboratory plate load tests are conducted on model footings resting on sand bed reinforced with plastic multi-directional reinforcements. The bearing capacity, settlement and heave are evaluated and the effect of depth to first layer, spacing between reinforcements in a layer, number of layers and spacing between layers are investigated. The bearing capacity at 25 mm settlement improved by almost 1.3 times for a single layer of reinforcement, placed at an optimum depth of 0.5B. An increase in number of layers beyond four resulted in a reduction in improvement of bearing capacity. Three layers of reinforcement, spaced vertically apart at 0.5B resulted in a maximum increase of 185% in the bearing capacity. For the same area, the multi-directional reinforcing elements provide additional confinement to the soil mass due to the three dimensional projections. Comparing the economic aspects, the multi-directional elements prove to be a viable alternative to the conventional planar geosynthetics. An artificial neural network based model has been developed in order to effectively predict the ultimate bearing capacity and settlements of the model footing, resting on reinforced sand.

Investigation of the behavior of shallow machine foundation resting on a saturated layered sandy soil subjected to a dynamic load

In liquefying soils, Shallow foundations may experience an increase in settlement and displacement due to dynamic loading. Therefore, the machine footing may settle and tilt excessively. In this paper, the settlement of shallow foundation and inner displacement on liquefiable of unreinforced and reinforced saturated multi-layered sandy soils (medium-dense sand MD) will be studied. The relative density of the first and second layers is 50% and 85% corresponding to medium sand soil and dense sand soil respectively. The tests have been carried out on 20 models. The amplitudes of the applied harmonic load are 0.25, 1 and 2 tons with frequencies of 0.5, 1 and 2 Hz. The used foundation was with dimension 200*200*20 mm and the geogrid was used as reinforcement material. For each amplitude and frequency of load, the sand models were tested without and with reinforcement in various configurations (0.5B, 1B using single reinforcement layer and 0.5B, 1B using double reinforcement layers) where B is the square footing width. The results showed the high susceptibility for liquefaction and its potential which increased with increasing amplitude load and amplitude frequency. Also, the surface settlement and displacement were increased in the first layer and reduced with increasing relative density. The results also showed the high effect of reinforcement material and its configuration and number of layers by maintaining the little settlement values when fixing other parameters.

Instability of Thin Concrete Walls with a Single Layer of Reinforcement under Cyclic Loading: Numerical Simulation and Improved Equivalent Boundary Element Model for Assessment

ABSTRACT Thin reinforced concrete walls may fail due to out-of-plane instability when subjected to seismic loading. While previous numerical studies on wall instability have focused on the behaviour of members with two layers of vertical reinforcement, this work addresses the response of walls with a single layer of rebars. Such walls are particular prone to out-of-plane failure when subjected to cyclic in-plane loading. The numerical investigations herein performed simulate the aforementioned local behaviour and validate it against experimental measurements. A parametric study on the effect of boundary conditions shows that imposing an out-of-plane displacement or a rotation at the storey height increases the vulnerability to instability. It is also seen that the storey height itself is an influencing variable. The second part of this study proposes an improved equivalent boundary element model for the assessment of wall instability. Existing mechanical models, based on pinned-pinned boundary conditions, represent the boundary element over the height of the plastic hinge. This work shows that such models often underestimate the critical tensile strain triggering out-of-plane failure. A new equivalent boundary element model is proposed where a bilinear axial displacement profile defined a priori is applied. The latter is shown to satisfactorily approximate the vertical strain profile in wall boundary elements and to lead to better estimates of the critical strain triggering out-of-plane failure.

Seismic performance of squat thin reinforced concrete walls for low-rise constructions

Thin reinforced concrete (RC) walls with single layer reinforcement have been used for houses and buildings in several Latin American countries. Although some design codes include recommendations for squat thin walls in low-rise constructions, its seismic performance has not been validated adequately in past earthquakes. This article presents the results of an experimental campaign of nine full-scale specimens conducted to characterize the influence of the steel type, the reinforcement ratio, and the wall thickness on the seismic behavior of squat thin RC walls with single layer reinforcement. Both welded wire and deformed bars were used as web reinforcement. Experimental results are used to develop nonlinear models to assess the seismic behavior of a prototype two-story house with welded wire reinforcement and deformed bars by means of incremental dynamic analyses. The experimental results show that the type of steel has the largest influence on wall seismic performance. The numerical results suggest that RC walls with single layer reinforcement are suitable for housing applications up to two stories in high seismicity regions, particularly walls detailed with deformed bars.

Load-bearing characteristics of square footing on geogrid-reinforced sand subjected to repeated loading

A series of dynamic model tests that were performed on a geogrid-reinforced square footing are presented. The dynamic (sinusoidal) loading was applied using a mechanical testing and simulation (MTS) electro-hydraulic servo loading system. In all the tests, the amplitude of loading was ±160 kPa; the frequency of loading was 2 Hz. To better ascertain the effect of reinforcement, an unreinforced square footing was first tested. This was followed by a series of tests, each with a single layer of reinforcement. The reinforcement was placed at depths of 0.3B, 0.6B and 0.9B, where B is the width of footing. The optimal depth of reinforcement was found to be 0.6B. The effect of adopting this value versus the other two depths was quantified. The single layer of geogrid had an effective reinforcement depth of 1.7B below the footing base. The increase of the depth between the topmost geogrid layer and the bottom of the footing (within the range of 0.9B) did not change the failure mode of the foundation.

Probabilistic bearing capacity of strip footing on reinforced anisotropic soil slope

The probabilistic bearing capacity of a strip footing placed on the edge of a purely cohesive reinforced soil slope is computed by combining lower bound finite element limit analysis technique with random field method and Monte Carlo simulation technique. To simulate actual field condition, anisotropic random field model of undrained soil shear strength is generated by using the Cholesky-Decomposition method. With the inclusion of a single layer of reinforcement, dimensionless bearing capacity factor, N always increases in both deterministic and probabilistic analysis. As the coefficient of variation of the undrained soil shear strength increases, the mean N value in both unreinforced and reinforced slopes reduces for particular values of correlation length in horizontal and vertical directions. For smaller correlation lengths, the mean N value of unreinforced and reinforced slopes is always lower than the deterministic solutions. However, with the increment in the correlation lengths, this difference reduces and at a higher correlation length, both the deterministic and probabilistic mean values become almost equal. Providing reinforcement under footing subjected to eccentric load is found to be an efficient solution. However, both the deterministic and probabilistic bearing capacity for unreinforced and reinforced slopes reduces with the consideration of loading eccentricity.

Thin slender concrete rectangular walls in moderate seismic regions with a single reinforcement layer

Some Latin-American countries, including Colombia, Peru, Panamá and the Dominican Republic, have adopted an industrialized system for the construction of buildings using thin slender reinforced concrete walls. The main advantage of this system is that it can increase the construction speed and reduce the use of nonstructural walls, as all architectonical spaces are defined by the structural walls. Additionally, designers tend to use thin structural walls with low steel reinforcement ratios, which is reflected in a reduction of the construction cost. The typical wall section for 6 to 10-story buildings is characterized by a thickness of around 100 mm and a single layer of welded wire mesh acting as longitudinal and transverse reinforcement. Additional reinforcing bars may be placed at the wall edges to increase moment capacity, but in most cases, there are no confined boundary elements along the edges. Despite the system's popularity, experimental data for these types of walls is still scarse. In addition to this, structural walls of low thickness and high aspect ratio with unconfined or poorly confined boundary elements have shown structural deficiencies in the 2010 Central Valley Chile earthquake. In this paper, existing and new experimental data from representative thin slender walls, used in moderate seismic regions, was analyzed to evaluate the structural system under lateral loads. Two unconfined reinforced concrete walls with typical section detailing were tested. Additionally, these tests were complemented with an experimental database of 28 rectangular wall units of thickness less than 100 mm, as reported in the literature. This data was used to analyze the behavior of rectangular thin slender walls in terms of axial load ratio, boundary elements conditions, plastic hinge length, and maximum drift capacity. The experimental data shows a significant reduction in drift capacity as axial load, clear interstory height to wall thickness ratio, or wall length increases. It is also evident that plasticity is concentrated at the base of the walls, mainly due to the low vertical reinforcement ratios. Finally, a capacity vs. demand stochastic analysis was carried out to evaluate the performance of buildings up to 10 stories in a moderate seismic zone. These analyses show that for moderate seismic regions the probability of reaching a severe damage limit state is low for buildings configured with rectangular walls having a single layer of reinforcement.

Improvement of bearing capacity of soil by using natural geotextile

An experimental study has been carried out to improve the bearing capacity of soils by using geotextile. In the present study geojute (gunny bags) is used as geotextile, whereas sand is used as soil media. This research presents the results of laboratory load tests on model square footings supported on reinforced sand beds. A total of 32 load tests are conducted to evaluate the effects of single layer reinforcement placed below square model footings. Parameters of testing programme of the research are the depth of reinforcement, the plan area of reinforcement and the footing size. The test results indicated that the maximum gain in ultimate bearing capacity (UBC) of footings on reinforced soil (by using geojute) is found to be increased by a factor of 3.37 as compared to soil without geojute. Also, the optimum size of reinforcement is found to be 3.5B × 3.5B irrespective of the type of reinforcing materials used. The optimum placement position of geotextile is found to be 0.5B from the base of the footing. At low settlement rates, the study on the values of BCR reveals almost the same results with regard to optimum depth and size of reinforcement mentioned above. It is found that with increase in the settlement rate, BCR increases. Also, the improvement in bearing capacity is found to increase with increase in footing size.