Welded Wire Fabric Research Articles

Flexural performance evaluation of slab using welded bar mat

ABSTRACT This is an experimental study on flexural performance evaluation when welded bar mats (WBM), which improve the rib shape, strength, and diameter limits of the existing structural welded wire fabric (WWF), are applied to slabs. The purpose of this study was to verify the change in behavior and structural performance when a new material was applied to a structural member. Flexural tests were performed with a total of 10 slab specimens using various variables. The load-deflection relationship and crack patterns of the slab specimens were analyzed to evaluate the applicability of WBM as a structural reinforcement. The results of the structural test were compared with the proposed design formula of the current design standards to check the safety, and the serviceability were verified by comparing the performance with the case of using the conventional rebar. According to the material test results, the yield strength of the steel wires applied to the WBM did not appear clearly, the elastic modulus of the material increased by about 8% compared to that of normal rebar, so that the yield strain and elongation decreased compared to that of normal rebar. When WBM were used for slabs, the nominal strength of the member was found to sufficiently satisfy the design flexural strength. However, as the strength of the material increased, bond failure occurred due to stress concentration between orthogonal steel wires so that deflection and crack concentration phenomena increased.

Behavior of Composite Floor Assemblies Subject to Fire: Influence of Slab Reinforcement

AbstractA series of fire experiments are being conducted on the 2‐story steel framed building with composite floors in the National Fire Research Laboratory. This paper presents a brief overview of experimental design and discusses some results of the first test conducted on 6.1 m by 9.1 m composite floor assembly exposed to a standard fire. The test floor slab was constructed with lightweight concrete cast on 7.7 cm deep formed steel deck units and welded wire fabric (60 mm/m2) as the minimum shrinkage reinforcement required in the U.S. practice. The structural steel beams and girders were sprayed with a cementitious fire resistive material for a 2‐hour restrained fire resistance rating. While the test floor assembly resisted mechanical loads (2.7 kN/m2) applied using hydraulic actuators, its underside was exposed to a natural gas‐fueled compartment fire that was equivalent to the standard gas temperature‐time relationship. The study revealed that the test floor assembly could withstand an imposed load at a large vertical deflection on the order of span / 16, but the concrete slab failed due to limited ductility and strength prior to 2 hours in a standard fire. Simple post‐test predictions were performed incorporating tensile membrane action in the floor slab to compare with the measured behavior. Limited comparisons discuss the contribution of steel decking and slab reinforcement to the load‐carrying capacity of a floor assembly in fire.

Study on Cyclic Response of Circular Spiral Confined Exterior Beam–Column Joints with Welded Wire Fabric

The experimental results of four exterior beam–column joints (CS, CS1, CS2 and CS3) with circular spiral confinement and various reinforcement detailing under reversed cyclic loading are presented. All the four specimens were detailed according to ductile detailing code for reinforced concrete structures IS 13920. CS1 was provided with additional reinforcement from column to beam. CS2 and CS3 were provided with welded wire mesh. CS2 had welded wire mesh in the joint region, and CS3 had welded wire mesh both in the joint and beam region. The intention of these detailing schemes was to relocate the plastic hinge and to explore the potential of welded wire mesh as additional joint confinement (CS2 & CS3) and means to relocate plastic hinge (CS1& CS3). The seismic behaviour was evaluated in terms of load–displacement relation, ductility, stiffness, energy dissipation, viscous damping ratio, load ratio, beam rotation and crack pattern. Out of the four test specimens, seismic performance of CS1 was better than that of CS, CS2 and CS3 in terms of all parameters.

The effect of Welded Wire Fabric (WWF) confinement on axial capacity of hollow columns

The aim of the study was to determine the effect of installing different sizes of Welded Wire Fabric (WWF) as a concrete restraint on axial carrying capacity of hollow columns. WWF is used with a wire spacing of 12.2 times 12.2 mm, 19 times 19 mm, 25 times 25 mm, with a diameter of 0.7 mm. A hole of 1 inch in the column causes a decrease in compressive strength of the column of 5.62 percent, i.e., from compressive strength of 226.697 kg per square cm (specimen A) to its compressive strength 214, 065 kg per square cm (specimen B). The percentage increase in axial carrying capacity of the perforated column type C is 13.16 percent, W1 is 2.96 percent, W2 is 11.33 percent, W3 is 13.27 percent, SW1 is 0.51 percent, SW2 is 5.51 percent and SW3 is 9.08 percent. WWF is able to increase compressive strength of hollow concrete columns by W1 is 7.08 percent, W2 is 12.41 percent, W3 is 14.36 percent, SW1 is 4.53 percent, SW2 is 9.73 percent and SW3 is 14.59 percent.

Perilaku Runtuh Balok Beton Bertulang dengan Sengkang Welded Wire Fabric (WWF)

The use of Welded Wire fabric (WWF) has been widely tested and proven to behave very well as stirrups in a column, but its behavior has not been widely known when used on beams. This research was conducted to evaluate the behavior of beams with stirrup reinforcement of WWF M4 grid. A total of nine beam specimens with dimensions of 330mm x 180mm x 1500mm were made and tested under monotonic loading until failure loads with three variations of stirrup, where each variation was made of three beam specimens and four concrete cylinders. The concrete was a ready mix concrete with an average compressive strength of 22,875 kN at 28 days. Beams were tested on simply supported with two concentrated loads at a distance of 500 mm from each support. The loads was applied incrementally and the middle span deflections were recorded for each increase in loads. The test results show that the stirrups of WWF M4 grid on beam specimens can increase the shear capacity, stiffness and control the occurrence of the first inclined crack. When compared to conventional stirrups (BJTP ∅ 6mm), beams with WWF M4 stirrups show better behavior.

Combining Traditional Materials-Concrete and Reinforcement - in a Modern Manner-SCC and WWF - for Cost Effective and Zero Defects Construction

The paper describes how two traditional construction materials-Concrete and Steel Reinforcement can contribute better value to RCC and Precast Concrete structures by modernizing their forms as Self-Compacting Concrete (SCC) and Welded Wire Fabric (WWF). SCC is widely accepted by infrastructural, industrial, commercial and even individual house builders – due to its assured quality delivery, especially for cast–in-situ RCC construction. Many defects with conventional vibrated concrete -- honeycombing, segregation and bleeding, loss of workability, choking in concrete pump pipelines and overheating -- have been eliminated or at least minimized by using SCC. For any type of congested reinforcement, mainly in beam – column junctions, edges and corners, SCC has delivered satisfactory filling and honeycomb free densification. Also due to the absence of the use of vibrators, formworks have been spared from joint leakages – saving both the concrete and the formwork itself. But however, even in many advanced construction companies, due to poor detailing practices, and non-mechanized bar-bending (or mechanization limited to only cutting and bending of rebars ), reinforcement laps, splices and bends, hooks, pose an additional burden on the free flow, filling and densification of SCC. Thus using SCC alone may not ensure defect free construction in RCC. The changes should be wholesome and comprehensive. This paper describes how SCC and WWF enhance the quality of RCC construction and ensuring defect free construction. The effects of WWF and SCC are elaborated in detail considering all the physical properties and practical issues. Along with the technical analysis, the commercial and sustainable benefits of SCC and WWF are discussed.

A numerical-experimental evaluation of beams composed of a steel frame with welded and conventional stirrups

Reinforced concrete structures are widely used in civil engineering projects around the world in different designs. Due to the great evolution in computational equipment and numerical methods, structural analysis has become more and more reliable, and in turn more closely approximates reality. Thus among the many numerical methods used to carry out these types of analyses, the finite element method has been highlighted as an optimized tool option, combined with the non-linear and linear analysis techniques of structures. In this paper, the behavior of reinforced concrete beams was analyzed in two different configurations: i) with welding and ii) conventionally lashed stirrups using annealed wire. The structures were subjected to normal and tangential forces up to the limit of their bending resistance capacities to observe the cracking process and growth of the concrete structure. This study was undertaken to evaluate the effectiveness of welded wire fabric as shear reinforcement in concrete prismatic beams under static loading conditions. Experimental analysis was carried out in order compare the maximum load of both configurations, the experimental load-time profile applied in the first configuration was used to reproduce the same loading conditions in the numerical simulations. Thus, comparisons between the numerical and experimental results of the welded frame beam show that the proposed model can estimate the concrete strength and failure behavior accurately.

Numerical investigation on the structural behavior of two-way slabs reinforced with low ductility steel

A numerical investigation of the impact of steel ductility on the strength and ductility of two-way corner and edge-supported concrete slabs containing low ductility welded wire fabric is presented. A finite element model was developed for the investigation and the results of a series of concurrent laboratory experiments were used to validate the numerical solution. A parametric investigation was conducted using the numerical model to investigate the various factors that influence the structural behavior at the strength limit state. Different values of steel uniform elongation and ultimate to yield strength ratios were considered. The results are presented and evaluated, with emphasis on the strength, ductility, and failure mode of the slabs. It was found that the ductility of the flexural reinforcement has a significant impact on the ultimate load behavior of two-way corner-supported slabs, particularly when the reinforcement was in the form of cold drawn welded wire fabric. However, the impact of the low ductility WWF has showed to be less prominent in structural slabs with higher levels of structural indeterminacy. The load-deflection curves of corner-supported slabs containing low ductility WWF are brittle, and the slabs have little ability to undergo plastic deformation at peak load.

Analysis of Box Culvert with Different Aspect Ratio

Box culverts are the default buried structure type, where pipe solutions are not suitable. Their larger openings are often required to provide adequate hydraulic capacity. Box culverts are also frequently used for pedestrian or cattle underpasses. The reinforcement used in concrete box culverts can be either conventional bar reinforcement or welded wire fabric. Welded wire fabric has yield strength slightly larger than conventional bar reinforcement. Standard designs for precast concrete box culverts are available with spans varying from 6 to 16 feet and rises varying from 4 to 14 feet. Standard precast concrete box culverts are characteristically invented in 6 foot sections; however larger boxes are fabricated in 4 foot sections to reduce section weight. The designs utilize concrete strengths are suitable for fill heights ranging from less than 2 feet to a maximum of 25 feet. Box culverts outside of the standard size ranges must be custom designed. Each culvert size has three or four classes. Each class has specified wall and slab thicknesses, reinforcement areas, concrete strength, and fill height range to which it applies. To prevent corrosion at the ends of welded wire fabric, nylon boots are required on the ends of every fourth longitudinal wire at the bottom of the form. A maximum of two layers of welded wire fabric can be used for primary reinforcement. If two layers are used, the layers may not be nested. The first box culverts built in Minnesota were made of cast-in-place concrete. The activity of these structures over the years has been very good. Currently, most box culvert installations are precast due to the reduced time required for plan production and construction. Cast-in-place culverts continue to be an allowable option. Buried structures serve a variety of purposes. They are typically used for conveying water. At other times, they are used to provide a grade separated crossing for pedestrian and bicycle traffic. A variety of structure and material types are used. The most prevalent types are pipes and box culverts. Buried structures with horizontal dimensions less than 10'–0 are not classified as bridges. Typically, these smaller buried structures do not need widespread design and are selected from standard design tables. Buried structures with horizontal dimensions greater than or equal to 10'–0 are considered bridges and require a plan prepared by the Bridge Office. All box culverts need a Bridge Office equipped plan as well. In addition to pipes and box culverts, precast concrete arches, precast three-sided structures, and long-span corrugated steel structures are used as buried structures. Buried structures carry vertical loads through a mixture of internal capacity and soil arching around the structure; this is termed soil-structure interaction. The means by which a buried structure carries vertical load varies significantly between different structure types due to their relative stiffness. Concrete box culverts and rigid pipes are categorized as rigid culverts and are supposed to carry the design loads internally with limited requirements or benefit of the soil. Flexible pipe structures (corrugated steel, thermoplastic, etc.) carry loads through soil-structure interaction. For this reason, material and installation requirements of the pipe and soil are well defined including trench or embankment conditions and backfilling and compaction procedures to ensure that the assumed soil-structure capacity is provided and that settlements are not excessive.

Cyclic tests on slip resistance of squat heavyweight concrete shear walls with construction joints

The objective of this study was to examine the effectiveness of different slip-resistance bars (X-, W-, and Ω-shaped bars) on reducing sliding shear displacement at the base interface of squat heavyweight concrete (HWC) shear walls with construction joints. In addition, the structural applicability of welded wire fabric (WWF) reinforcement was investigated as an alternative to the individual deformed bars conventionally used for the shear reinforcement of shear walls. All the wall specimens had the same concrete dry density of 3380kg/m3, geometrical dimensions with barbell-shaped cross-sections, and shear ratio of 1.0. The ultimate failure of the walls subjected to under constant axial loads and reversed cyclic lateral loads was associated with a kinking in the longitudinal and vertical shear bars and splitting of the surrounding concrete at the base interface due to the dowel resistance of the bars. The slip-resistance bars were effective in reducing the shear slip displacement at the base interface after the peak load of the walls was reached. The WWF reinforcement performed comparably to the conventional shear reinforcements in enhancing the shear strength of the squat shear walls and preventing a rapid decrease in the applied loading after the peak strength. The shear strength of the squat HWC shear walls can be conservatively estimated using equations proposed by EC8 for earthquake resistance, even for avoiding sliding shear failure at high wall drift ratios.

Behavior of Concentrically Loaded Welded Wire Fabric Reinforced Concrete Columns with Varying Reinforcement Grids and Ratios

Behavior of Concentrically Loaded Welded Wire Fabric Reinforced Concrete Columns with Varying Reinforcement Grids and Ratios

Soil-Structure Interaction of Steel Fiber Reinforced Concrete Slab Strips on a Geogrid Reinforced Subgrade

Performance of slabs on grade is governed mainly by the mutual coupled performance of the slab stiffness and the subgrade support. The use of reinforcement geogrids to increase the stiffness and structural capacity of the subgrade support can be potentially advantageous, but is currently poorly understood, especially under frequent transient loading conditions. The objective of this experimental study is to investigate the beneficial use of geogrids as a reinforcing material in a loose subgrade. This paper presents the results of large scale laboratory tests on slab strips (300 mm wide × 150 mm thick × 2,500 mm long) supported on a reinforced subgrade. The slab strips contained either steel fibers or were reinforced with welded wire fabric (WWF), and are compared with earlier tests on an unreinforced subgrade. All slab strips were tested under a central point load and were restrained from uplift at the ends. Both monotonic and cyclic loads are considered. The geogrid increases the bottom surface cracking load of the slab strip, does not affect the top surface cracking load, and increases the ultimate load carrying capacity. The use of steel fiber reinforced concrete (SFRC) was successful in providing post-cracking strength to maintain slab integrity when compared to the WWF reinforced slab strip used in this investigation. A simplified analysis of beams on grade is carried out for the elastic and post-cracking regions, and predicted values for the SFRC slab strip under monotonic load are compared to the measured load-deformation response. The comparison indicates that the theoretical response underestimates the capacity of the SFRC slab strip.

Full-Scale Testing and Performance Evaluation of Rockfall Concrete Barriers

Rockfall hazards are present throughout the state of Ohio. The Ohio Department of Transportation (DOT) employs Test Level 3 standard concrete barriers along the edges of roadways to contain rockfalls in high-risk areas. The performance of these barriers under impact from rocks on the ditch side and their effectiveness for rockfall catchment are relatively unknown. Full-scale impact tests were performed on concrete barriers to simulate the effects of impacts from rocks of various sizes and shapes. Numerous impacts were made at different sections and levels of the barriers to test their structural integrity and energy absorption capacity. The results from this study revealed that 32-in.-high precast concrete barriers with current Ohio DOT details had an impact energy absorption capacity of up to 24 kJ under a single impact. The corresponding energy absorption capacity of 42-in.-high cast-in-place concrete barriers was about 56 kJ under a single impact. Moreover, these barriers experienced severe cracking and spalling of concrete under impact loading. Several design modifications were studied in this test program. These modifications included reducing the spacing of rebars and rebar sizes, using welded wire fabric, and using different types of fibers in the concrete. The tests conducted on the modified concrete barriers showed an impact energy increase of more than 100% with the modifications suggested in this study. Barriers made from the modified designs also experienced significantly reduced extent and severity of cracking and a reduction in spalling and splashing of concrete under impact loading.

Ductility of concrete slabs reinforced with low-ductility welded wire fabric and steel fibers

The use of low-ductility welded wire fabric (WWF) as a main tensile reinforcement in concrete slabs compromises the ductility of concrete structures. Lower ductility in concrete structures can lead to brittle and catastrophic failure of the structures. This paper presents the experimental study carried out on eight simply supported one-way slabs to study the structural behavior of concrete slabs reinforced with low-ductility WWF and steel fibers. The different types of steel fibers used were crimped fiber, hooked-end fiber and twincone fiber. The experimental results show that the ductility behavior of the slab specimens with low-ductility reinforcement was significantly improved with the inclusion of <TEX>$40kg/m^3$</TEX> of twincone fiber. Distribution of cracks was prominent in the slabs with twincone fiber, which also indicates the better distribution of internal forces in these slabs. However, the slab reinforced only with low-ductility reinforcement failed catastrophically with a single minor crack and without appreciable deflection.

Condition assessment and strengthening of residential units

About 40, ground plus one (G+1) residential units were designed using a hybrid structural framing system (RC frame and load bearing walls). A few months after the completion of the ground floor of the residential units, cracks appeared at several locations in the structure. Field and Laboratory testing was conducted to ascertain the in situ strength of concrete and steel reinforcement. The results of the experimental work were used in the analytical ETABS model for the structural stability calculations. The results indicated that residential units were marginally safe in the existing condition (completed ground floor), but the anticipated construction of the floor above the ground floor (G+1) could not be carried out as the strength of the structural system was inadequate. To increase the safety of existing ground floor and to provide the option of the construction of one floor above, rehabilitation and strengthening design was performed. The proposed strengthening design made use of welded wire fabric (WWF) and carbon fibre reinforced polymer (CFRP) laminates/sheets for the strengthening of walls, columns and slabs. The residential units will be strengthened in the near future.

Behavior of unreinforced masonry prisms and beams retrofitted with engineered cementitious composites

The impact of a thin layer of a ductile fiber-reinforced concrete referred to as engineered cementitious composites (ECC) on unreinforced masonry (URM) prisms and beams has been evaluated. The objective of the research was to characterize the performance and potential benefits of using ECC to retrofit URM with eventual application to masonry infill walls in non-ductile reinforced concrete frames. Compression tests of masonry prisms and flexural tests of masonry beams with different ECC retrofit schemes were conducted. The variables studied were the use of wall anchors to improve the ECC-masonry bond and alternate steel reinforcement ratios within the ECC layer in the form of welded wire fabric. The ECC retrofit was found to increase the strength and stiffness of URM prisms by 45 and 53 %, respectively compared to those of a plain specimen. When wall anchors were installed on the masonry specimens, the bond between the ECC layer and the masonry surface was improved. Four-point bending tests indicated that the strength and more importantly the ductility of an ECC retrofitted brick beam are increased significantly, especially when light reinforcement is added to the ECC layer, relative to an URM beam. Analytical models for estimating the strength and stiffness of ECC retrofitted masonry specimens are proposed and evaluated.

Experimental Research on Shear Behavior of Reinforced Concrete Beams with High-Strength Stirrup under Uniform Load

According to tests of 8 T concrete beams with HRB500 steel bars as stirrup, the shear behavior of beams was researched under uniform load, and the influencing factors of diagonal crack width were analyzed, such as the different concrete strength, stirrup spacing and the welded wire fabric. Experimental results show that concrete beams with HRB500 steel bars as stirrup show similar behavior to the beams with conventional stirrup, and the stirrups yield can be achieved which meets the requirement of shear behavior in structure. In addition, the welded wire fabric can be used as one of the new kinds of reinforcement to control diagonal crack width.

Experimental Behavior of Concrete Columns Confined by Welded Wire Fabric as Transverse Reinforcement under Axial Compression

This study examines the behavior of normal-strength concrete short columns confined by welded wire fabric (WWF) as transverse reinforcement under monotonically increasing concentric compression. The authors investigate the effects of volumetric ratio, spacing and lateral steel configuration, and distribution of longitudinal steel around the core perimeter or longitudinal reinforcement ratio on the uniaxial behavior of reinforced concrete columns. Tests were conducted on 22 short concrete columns reinforced with longitudinal steel and WWF or conventional ties under axial compression. The performance of columns laterally reinforced with WWF was compared with that of columns laterally reinforced with conventional ties. The findings show that WWF can be effective in confining the core concrete. Ductility increases of 130% and strength increases of at least 17% were found when compared with the corresponding specimens with conventional ties. The ductility of confined concrete columns improved with an increase of longitudinal reinforcement and decrease of transverse reinforcement spacing. Welded grids reduced the congestion of reinforcement and improved concrete quality in the members.

Axial Load Behavior of Concrete Columns with Welded Wire Fabric as Transverse Reinforcement

A new reinforcement system, Welded Wire Fabric (WWF), is proposed to perform the function of transverse steel in reinforced concrete columns. WWF is made from cold-drawn steel wires arranged in two orthogonal directions and is prefabricated in a production line. WWF reinforcement eliminates some of the detailing problems inherent in traditional rebar in the reinforced concrete construction resulting in easier and faster construction, and better economy and quality control. An experimental investigation on the behavior of square concrete columns confined by WWF was carried out. The confinement provided by WWF was investigated by comparing the results from 20 short column tests. The specimens were tested under axially loading. The effects of volumetric ratio, spacing and grid configuration of WWF reinforcement as well as the distribution of longitudinal reinforcement on the behavior of columns were investigated. Based on the observation, the results indicated that the use of WWF as transverse steel has resulted in considerable enhancement both in strength and ductility.

Investigation of Stress-Strain Models for Confinement of Concrete by Welded Wire Fabric

Various analytical models available in the literature for the confinement of concrete by conventional rectilinear ties and welded wire fabric are studied. These models are applied to the specimens tested by the authors as well as by other investigators to predict the results. Experimental results are compared with results predicted by various models. It is concluded that none of the analytical models could accurately predict the stress-strain curves for the full range of experimental data considered in this study. Most of the models were able to predict the peak strength but failed to predict satisfactorily the associated strain and the stress-strain curves. The predictions of the Akiyama et al. were generally in closest agreement with the experimental results. Since this model incorporates almost all the parameters of confinement.