Two-point Loading Research Articles

Performance of doubly reinforced concrete beams with GFRP bars

Abstract The study focused on examining the behavior of six concrete beams that were reinforced with glass fiber-reinforced polymer (GFRP) bars to evaluate their performance in terms of their load-carrying capacity, deflection, and other mechanical properties. The experimental investigation would provide insights into the feasibility and effectiveness of GFRP bars as an alternative to traditional reinforcement materials like steel bars in concrete structures. The GFRP bars were used in both the longitudinal and transverse directions. Each beam in the study shared the following specifications: an overall length of 2,400 mm, a clear span of 2,100 mm, and a rectangular cross-section measuring 300 mm in width and 250 mm in depth. To apply loads for testing, two-point static loads were placed at the middle third of the beam’s span, creating a shear span of 700 mm in length. The beams were categorized into three groups depending on the GFRP longitudinal reinforcement ratio in the tension and compression zones of the section. GFRP bars with a diameter of 15 mm were employed as longitudinal reinforcement, while closed GFRP stirrups with a diameter of 8 mm at 100 mm were utilized as transverse reinforcement throughout the structural element. Test results have indicated that the ultimate load capacity of doubly GFRP-reinforced concrete beams varies compared to singly GFRP-reinforced beams. The range of variation observed is between an increase of 8% and a decrease of 4%. Accordingly, the contribution of the GFRP bars in the compression zone is insignificant and could be ignored in design calculations. It was observed that the loading level at which crack spacing stabilized ranged between 31.3 and 87% of the experimental failure load. It seems that the crack spacing decreased with the increase in the reinforcement ratio.

Flexural behavior of steel fiber reinforced slag- based geopolymer concrete beams

This study includes tested nine reinforced concrete beams. It’s designed to fail in flexural under two-point load. All beams are classified according to the type of concrete and the percentage of PVA into three groups. The first group including four reinforced geopolymer concrete beams with percent of PVA was 0.2 %; second group including four reinforced geopolymer concrete beams with percent of PVA was 0.75 % and third group including one reinforced normal concrete beam. The results showed when comparing the geopolymer concrete beam with the normal concrete beam, noticed that the ultimate strength is equivalent to many times the normal concrete. The best percentage for improving the ultimate load for beam NO.6 (GSSB10) where the percentage of increase was 132% this beam is reinforced by steel bars 2ɸ12mm at top and 2ɸ16mm at bottom. As for the other beams, the percentage increase in ultimate load was for beam NO.1 (46%), beam NO.2 (99%), beam NO.3 (13%), beam NO.4 (60%), beam NO.5 (58%), beam NO.7 (32%) and beam NO.8 (66%). The maximum deflection in all samples was high compared with the normal concrete, where the ultimate deflection reached 30 mm, while in the normal concrete it was 9.65 mm.

Shear performance of lightweight SCC composite beam internally reinforced with CFRP laminate stirrups and GFRP bars: Experimental and analytical study

This research demonstrates the structure feasibility of using carbon fiber reinforced polymer (CFRP) laminate stirrups as a form of transverse reinforcement in shear deficient GFRP reinforced lightweight self-compacting concrete (LWSCC) beams. An experimental study performed on eight full-scale shear deficient beam specimens. One beam served as the reference specimen and remaining beam specimens were internally reinforced with impregnated CFRP laminate stirrups. The parameters investigated in this study were the stirrup configuration, number of layers, stirrup spacing and width. Specimen tested under two-point loading and all results in term of load-deflection response as well as their failure modes were reported. All tested specimens failed due to shear compression failure mode along with the rupture of CFRP laminate stirrups, and the inclusion of CFRP laminate stirrups has significantly enhanced the nominal capacity of LWSCC beams ranged from 91%− 200% over control specimen. Shear strengths of the tested specimens were also theoretically predicted using different design standards. Comparison between the experimental and predicted shear strength has shown that ACI 440.1R-15, CSA S806–12, and CSA S6–14 provided the closest prediction. Therefore, it has been concluded that CFRP laminate stirrups can be used as a transverse reinforcement in GFRP reinforced LWSCC beams.

Flexural Behavior of Rectangular Double Hollow Flange Cold-Formed Steel I-beam

This research experimentally investigates the flexural behavior of rectangular hollow flange cold-formed steel I-beam (RHFCFSIB) under two concentrated loads at the same distance from the support. All specimens were at a constant clear span of (L=1500mm), a constant beam specifications (t=4mm) web, flange thickness (h=300mm) for beam′s depth, and flange width of (bf=150mm). The connecting distance between the bolts, i.e., connects the web to the flanges, was (L/6), and eight stiffeners for each beam were placed under the load bearing points and at the support points on each side. The experimental program included assembling the parts to make beams and testing four specimens under two-point loads. The major parameters adopted in the current research included the flange depth, i.e., hf=30,60,90, and 120mm. The results showed that the beam with a flange depth of 30 mm had a higher ultimate load than other beams; however, it was the highest beam deflection. The beam with a flange depth of 120mm was the best section as a flexural member. The ultimate capacity of this beam increased by 15.34% and 6.4% compared to beams with flange depths of 60mm and 90mm and decreased by 12.9% compared to a beam with a flange depth of 30 mm. The maximum deflection at beam mid-span with a flange depth of 120 mm decreased by 53.8%, 44%, and 19.94% compared to beams with flange depths of 30 mm, 60mm, and 90mm, respectively. Therefore, the flange depth significantly influenced the flexural behavior by increasing the flange depth. Also, the ultimate capacity increased, and the deflection was reduced. The main conclusions drawn from the study were discussed and summarized. The research showed that the Hollow flanged sections gave the best results for flexural behavior.

Rehabilitation of reinforced concrete deep beams by near-surface-mounted steel reinforcement

Abstract This article describes an experimental investigation of the behavior of reinforced concrete deep beams repaired by near-surface-mounted (NSM) steel bars. The first beam was loaded under a two-point load up to failure, and the other six deep beams were loaded to 0.4 and 0.75 of ultimate load. Then, they were repaired by NSM steel bars. The bar orientation and angle were the main variables in these beams. The primary goal of this study is to determine whether it is possible to restore the reinforced concrete deep beam with shear reinforcement to its full load-carrying capacity by NSM steel bars as the method of repair. All deep beams were tested with a shear span-depth ratio of 0.8. The test findings showed that the NSM steel repair bars were very effective in restoring the loaded deep beams’ full capacity. Moreover, NSM steel bars enhanced the original deep beams’ strength capacity from 4.16 to 19.44%. The ultimate load, mechanisms of failure, load–crack width distribution, and load–deflection profile are tracked as results.

Enhancing the performance of precast hybrid concrete deep beams using curved and arched designs: Experimental investigations

In recent years, deep beam performance improvement has garnered significant interest, leading to several proposed solutions. This study introduces and compares two new models of hybrid concrete deep beams, aiming to outperform conventional designs. Nine experimental specimens were subjected to one-point and two-point static loadings. The specimens shared identical dimensions, with an overall span of 1700 mm, width of 180 mm, and overall depth of 450 mm. Response parameters such as cracking and failure loads, failure modes, crack propagation rates, toughness, stiffness, and ductility were evaluated. Results indicated substantial enhancements compared to the conventional hybrid model. The curved model achieved a 5 % and 12 % increase in failure load under one-point and two-point loading, respectively. The corresponding enhancements for the arched model were 13 % and 20 %. Notably, toughness improvements ranged from 32 to 39 % and 97 % under two-point loading for the curved and arched models, respectively. Ductility gains were 39 % and 45 % under two-point loading and (45–57)% and 74 % under one-point loading for the respective models. The findings highlight the potential of the curved model with reactive powder concrete-normal strength concrete (RN) composition, offering increased load-carrying capacity and the possibility of using low-strength concrete for cost and weight reduction. The arched model also demonstrated significant enhancements. Changing the loading configuration from two-point to one-point resulted in reduced capacity, but the proposed models mitigated this reduction. This study contributes valuable insights into the behaviour of precast hybrid concrete deep beams, showcasing the superior performance of the proposed curved and arched models.

Shear behavior of normal and high-strength concrete beams reinforced with BFRP bars and basalt macro fibers

This research examined the effect of basalt macro fibers (BMF) on the shear resistance and behavior of normal-strength concrete (NSC) and high-strength concrete (HSC) beams longitudinally reinforced with basalt fiber reinforced polymer (BFRP) bars. Twelve BFRP reinforced concrete beams (BFRP-RC) were cast and tested under two-point loads without and with BFRP stirrups. The volume fraction (Vf) of BMF, the concrete compressive strength (fc′), and the existence of stirrups were all evaluated. Three volume fractions of BMF were used (0 %, 0.75 %, 1.5 %) with three classes of concrete compressive strength (30 MPa, 60 MPa, and 90 MPa). The results indicated that adding BMF to BFRP-reinforced-NSC and BFRP-reinforced-HSC beams enhanced the shear resistance. For concrete classes C30 and C90 shear resistance increased by 38 % and 62 %, respectively, when 0.75 % BMF was added, and it increased by 81 % and 115 %, respectively, when 1.5 % BMF was added. The enhancement of shear resistance due to the addition of BMF to BFRP-reinforced-HSC beams was more effective than in BFRP-Reinforced-NSC beams. Moreover, the addition of BMF enhanced the shear resistance of both stirrup-equipped and stirrup-less beams. The experimental results showed that the shear resistance of BFRP-reinforced-HSC beams due to the addition of BMF rather than stirrups is comparable, if not better, with stirrups. For instance, the shear resistance of the beam reinforced with 1.5 % of BMF is more than the beam reinforced with the minimum amount of BFRP stirrups. The post-cracking stiffness of all beams remarkably increased due to BMF addition. Furthermore, the effect of novel BMF on the mechanical properties of concrete was investigated.Additionally, an equation to predict the concrete contribution to the shear strength of FRP-RC beams was developed using the experimental shear strength of the tested beams and the experimental results of 217 FRP-RC beams without stirrups published in the literature. The proposed equation is combined with Said et al. and Narayanan and Darwish expressions to account for FRP stirrups and BMF contributions in the shear strength of the BFRP-RC beams. The mean value and the coefficient of variance (CV) of experimental to predicted ultimate shear strength of the beams (Vu,exp/Vu,pred) were 1.12 and 7.64%, respectively.

Influence of Temperature on Shear Behavior of Lightweight Reinforced Concrete Beams Using Pozzolana Aggregate and Expanded Polystyrene Beads

The innovation inherent to employing expanded polystyrene (EPS) beads lies in its transformative impact on traditional concrete practices. Through the incorporation of EPS beads in concrete mixtures, a novel approach emerges that significantly alters the material’s characteristics, and opens up new avenues for construction and design. Studying the shear behavior of RC beams made with EPS beads is essential for advancing knowledge, improving design practices, ensuring structural integrity, and promoting the effective and responsible use of innovative materials in construction. This research experimentally investigated the effect of using EPS beads and pozzolana aggregate (PA) on the shear behavior of the RC beams. A total of 27 simply supported rectangular beams were cast, using three novel distinct mix designs, and were subjected to two-point load testing until failure. These three mixes were categorized as follows: a control mix, a mix with only EPS, and a mix with EPS, along with an additive. The ultimate failure load was experimentally recorded for all specimens, and the influence of the temperature (300 °C and 600 °C) on the RC beams made with EPS was examined. The findings revealed a reduction in the concrete compressive strength and density in the beams containing EPS and EPS with superplasticizers of (21.7%, 24.9%) and (11.3%, 16.2%), respectively. Additionally, EPS played a significant role in diminishing the ultimate shear capacity of the beams, compared to the control beams, by about 19.4%. However, the addition of a superplasticizer along with the EPS helped to maintain the beam capacity, to some extent. Conversely, the beams exposed to a temperature of 300 °C exhibited an almost similar capacity to that of the control beams without heating. Nevertheless, at 600 °C, the beams displayed a noticeable decrease in the ultimate load capacity, compared to the unheated control beams.

Using woven recycled plastic fibers in reinforced concrete beams

The modern lifestyle, along with the advancement of new technologies has produced plastic waste and the recycling of these waste materials has become an important challenge for human societies. Polyethylene terephthalate (PET) is one of the most consuming waste materials. A solution to repel these materials is to use them in the civil engineering industry and buried them in concrete. PET layers and strips were used in reinforced concrete beams instead of steel reinforcements by some researchers. But, in this study, the longitudinal and transverse steel bars were replaced by woven recycled plastic fibers and tested experimentally. These woven PET bars are produced by the authors and used as a structural element. Six beams with different combinations of steel and woven PET bars are tested under two-point loading and the experimental and analytical results are presented. The results show that using these fibers concludes to increases the ductility of reinforced concrete beams. By replacing PET ropes instead of one, two and three tensile steel reinforcements, the ductility ratios of the beams are about 1.73, 1.76 and 4.12 times of the reference reinforced concrete beam. Moreover, some theoretical formulation is presented and compared with experimental data.

Shear behavior of self-consolidating concrete deep beams reinforced with hybrid of steel and GFRP bars

This paper experimentally investigates the dowel action contribution of longitudinal reinforcement, a hybrid of steel and GFRP bars (usually adopted for avoiding corrosion of steel bars), in concrete deep beams for different reinforcement schemes. The self-consolidating concrete without and with steel fibers (0.9 % and 1.2 % by volume) was used. Sixteen simply supported deep beams of 140 × 300 (depth) × 1500 mm were tested under the two-point loads. A model is developed to predict the shear capacity of deep beams without web reinforcement, taking into consideration the dowel action contribution of longitudinal reinforcement, which is a hybrid of steel and GFRP rebars. The results showed a significant dowel action contribution of steel as well as GFRP rebars to beam shear strength. However, the use of a hybrid system of steel and GFRP bars caused a reduction in the dowel action of steel bars due to their combined action.

Geo-polymer Mortar as Retrofitting Material for R.C. Element

Geopolymer has been subject of research in recent years. There are many studies which are carried out to examine viability of geopolymer mortar as an alternative material to Ordinary Portland Cement. Geopolymer material mainly consist of replacement of cementitious material by industrial waste like fly ash, blast furnace slag, bottom ash, metakaolin, Silica fumes etc. so in such way industrial waste will be used judiciously and there will be low emission of CO2. The present investigation aims to develop geopolymer mortar as a repair material using metakaolin, fly ash, blast furnace slag as source materials. For the purpose of evaluation of the performance of geopolymer mortar as repair material, reinforced concrete beams were casted, and damaged in two different patterns i.e. wide and hairline cracked and tested under two-point load flexure testing machine. Geopolymer mortar (GPM) comprises of supplementary cementitious material as a primary binder material and mixing it with alkali activators. Sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) were used as Alkali activators. Their different concentrations were prepared to study the most suitable mixture and its properties. Alkali activators with 10 M, and 12 M with 1:2 and 1:2.5 concentration ratio was prepared and tested for checking compressive strength gain of geopolymer mortar cubes. After casting and compressive testing of geopolymer mortar cubes it was observed that among all different trial mix with varying binder ratio, the cubes with GGBS (Ground Granulated blast furnace slag) to Fly ash ratio of (80:20) showed relatively higher strength at 7 days. Hence that proportion of binder to fine aggregate was used in preparation of geopolymer paste (GPP) and that paste was used for repairing beams which were damaged by applying two-point flexure load to obtain its gain in load carrying capacity at 7 and 28 days respectively.

Flexural behavior of a box ferrocement beams consisting of self-compacted mortar reinforced by fiber glass mesh and GFRP bars after exposure to high temperatures

The subject of the study deals with the investigation into the bending response of box-ferrocement beams with cement mortar that is self-compacted after being exposed to elevated temperatures. Beams were reinforced by GFRP, consisting of rebars and mesh of fiber glass, and compared with beams reinforced by conventional steel rebars and steel wire mesh. The experimental program consisted of twelve beams have sizes (225 × 150 × 1000) mm, with a 50 mm thickness as well as hollow of (125 × 50) mm. Six beams were reinforced by GFRP, and the other six beams were reinforced with steel. The beams were subjected to different temperatures: ambient temperature, 200 °C, 300 °C, and 400 °C. The bending performance of all beams was tested under a two-point load after extracting them from the furnace and after they had cooled. The study showed that the beams with steel or GFRP, they lose their properties when exposed to high temperatures. At 400 °C, an ultimate load, ductility, and toughness of GFRP-hollow beams were reduced by 86.34%, 36.82%, and 92.25%, respectively compared with the same beam at ambient temperature. The reduction in steel-hollow beams was less than GFRP-hollow beams. At 400 °C, the ultimate load, ductility, and toughness steel-hollow beams were decreased by 24.78%, 17.6%, and 63.86%, respectively compared with the same beam at ambient temperature. These beams still have not completely lost their strength, so they are able to withstand temperatures of more than 400 °C. The results proved that ferrocement beams reinforced by conventional steel have good properties in regard to higher ductility, higher first crack load, lower deflection, better controlling crack width, and are better than beams reinforced by GFRP after exposed to heat, where the ferrocement beams reinforced by GFRP were inefficient for heat resistance. Although these beams were given a higher ultimate load at ambient temperature than steel-reinforced beams.

Experimental Study of Shear Performance of High-Strength Concrete Deep Beams with Longitudinal Reinforcement with Anchor Plate.

As a transfer member at the discontinuous place of vertical load, the deep beam has a complex stress mechanism and many influencing factors, such as compressive strength of concrete, shear span ratio, and reinforcement ratio. At the same time, the stress analysis principle of traditional shallow beams is no longer applicable to the design and calculation of deep-beam structure. The main purpose of this paper was to use the strut-and-tie model to analyze its stress mechanism, and to verify the applicability of the model. Nine high-strength concrete deep-beam specimens with longitudinal reinforcement with an anchor plate of the same size were tested by two-point concentrated loading method. The effects of shear span ratio (0.3, 0.6, and 0.9), longitudinal reinforcement ratio (0.67%, 1.05%, and 1.25%), horizontal reinforcement ratio (0.33%, 0.45%, and 0.50%), and stirrup reinforcement ratio (0.25%, 0.33%, and 0.50%) on the failure mode, deflection curve, characteristic load, crack width, steel bar, and concrete strain of the specimens were analyzed. The results showed that the failure mode of deep-beam specimens was diagonal compression failure. The normal section cracking load was about 15 to 20% of the ultimate load, and the inclined section cracking load was about 30~40% of the ultimate load. The shear span ratio increased from 0.3 to 0.9, and the bearing capacity decreased by 32.9%. When the longitudinal reinforcement ratio increased from 0.67% to 1.25%, the ultimate load increased by 42.6%. The shear span ratio and longitudinal reinforcement ratio have a significant effect on the bearing capacity of the high-strength concrete deep beams with longitudinal reinforcement with an anchor plate. The shear capacity of nine high-strength concrete deep-beam specimens with longitudinal reinforcement with an anchor plate was calculated by national standards, and the results were compared with the calculation results of the Tan-Tang model, the Tan-Cheng model, SSTM, and SSSTM. The analysis showed that the softened strut-and-tie model takes into account the softening effect of compressive concrete, and is a more accurate mechanical model, which can be applied to predict the shear capacity of high-strength concrete deep-beam members with longitudinal reinforcement with an anchor plate.

Shear strength of recycled aggregate concrete beams without shear reinforcement

Steel fibers have recently become increasingly popular for strengthening reinforced concrete members. This research contains a study of shear strength under the effect of replacing 50% of natural coarse aggregate (gravel) with recycled aggregate (crushed brick) as well as the effect of steel fibers for natural aggregate concrete and recycled aggregate concrete. Five concrete beams with dimensions of 2000 mm in length, 300 mm in depth, and 200 mm in width were tested to evaluate the effect of recycled aggregates and to evaluate the efficiency of steel fibers in improving the shear capabilities of concrete beams. Beams are designed to fail due to shear stresses (without shear strengthening). The specimens were reinforced with four 4" X 16" steel bars at the bottom and two 2" X 10" steel bars as top reinforcement. Three volumetric fractions of steel fibers were used: 0%, 0.5%, and 1%. The samples were subjected to a two-point loading test. The beam samples have a ratio of shear span to effective depth (a/d) equal to 2. The results showed that replacing 50% of natural aggregate with recycled aggregate decreased ultimate shear strength, but adding steel fibers by 1% by volume resulted in an increase of 31.8% in shear strength for a recycled concrete beam. For ordinary concrete, the final shear strength increased by 18.3% and 30.8% when steel fibers were added by 0.5% and 1%, respectively. Moreover, the results also showed that the failure mode of all samples is the shear failure mode.

EXPERIMENTAL FLEXURAL STRENGTH OF GLASS FIBER REINFORCED POLYMER (GFRP) HYBRID REINFORCED CONCRETE BEAMS

Materials technology is an excellent opportunity to be developed industrially and on a needs scale according to the demands of society, namely supporting the environment, low maintenance, and long-term use. Using composite materials with reinforced polymers is a hot topic of discussion in civil engineering as new materials, strength/stiffness enhancers, or applications in building rehabilitation or renovation. Fiber Reinforced Polymer (FRP) is excellent as a new material because, in addition to being lightweight, corrosion resistant, and easy to work with, it also has high flexural strength, so it is a consideration to replace and or strengthen steel materials that are high in cost value. However, until now there has not been found the correct pattern or variant and volume of fibre so that it can be an alternative to the use of steel. The purpose of the study was to experimentally determine the flexural strength of Glass Fiber Reinforced Polymer (GFRP) hybrid beams either with steel reinforcement, with GFRP reinforcement, or with steel and GFRP combination reinforcement and different GFRP ratios (variants) through two-point load bending tests.The designed model is a development of a previous study that used one layer of 4 mm and produced a flexural strength smaller than the targeted flexural strength, so in this study, two layers of 8 mm were used. In addition, other experimental data that has been carried out from the literature is also used where the results of parametric studies provide evidence of the positive effect of hybrid steel and GFRP reinforcement ratios when obtaining GFRP models and volumes.The materials used to manufacture concrete beam test specimens 53x15x15 cm3 with quality of fc'35MPa have been tested according to SNI standards and meet both the minimum and maximum requirements specified. Based on the results of the material test, it is planned that the characteristic concrete quality fcr'=40.31 MPa, and based on the compressive strength test, the quality fcr'=41.68MPa is produced.The hybrid designed material with concrete or concrete and steel has been tensile tested with a maximum arcing load for the two layers = 8 mm variant; the tensile strength of the GFRP woven roving type with two layers 2 x 4 mm is 92.66 MPa. While plain steel reinforcement Diameter 8mm quality 280 MPa has a minimum tensile strength of 350 MPa (3.8 times the tensile strength of GFRP 8 mm).The results of testing and calculating the effect of GFRP as a substitute for steel reinforcement contributed to the flexural strength of concrete beams on average by 47.52%. In comparison, the contribution of flexural strength produced by concrete with steel reinforcement was 107.09%. The concrete variant of hybrid steel reinforcement and GFRP contributes to an increase in the average flexural strength of 117.02% > 4.8% compared to steel-reinforced concrete beams alone.

Assessment of concrete shear resistance of lightweight SCC beams containing scoria aggregates

Lightweight self-consolidating concrete (LWSCC) has become a construction material that combines the benefits of lightweight concrete (LWC) and self-consolidating concrete (SCC). However, this combination may affect the shear resistance of structural members made with such concrete. This paper evaluates the shear resistance and performance of LWSCC beams. Eight full-scale beams without stirrups were fabricated and tested to failure. Seven beams were constructed using LWSCC and one was cast using normalweight self-consolidating concrete (NWSCC). Natural lightweight coarse and fine scoria aggregates were used in preparing the concrete mix. The beams were tested over a simply supported span in a two-point loading configuration. The test parameters comprised the type of aggregates, the reinforcement ratio of longitudinal steel bars, the shear span-to-depth ratio, and the depth of the beam. The experimental results showed that employing scoria aggregates in the mix resulted in beams with a reduced self-weight, where the obtained unit weight of LWSCC was 1800 kg/m3. Compared to the beam with NWSCC, the counterpart beam with LWSCC showed 25% lower shear strength. Additionally, the LWSCC beam experienced a reduction of 20% in the flexural cracking load while the beam showed a larger number of cracks at failure. The shear strength of the beams was predicted using the relevant shear design provisions of the American Concrete Institute building code ACI 318, the Canadian standard CSA-A23.3, and Eurocode 2. The ACI 318 method provided more reliable and conservative estimates for the shear capacity of the tested beams.

Model experiment and numerical analysis of horizontal subgrade reactions acting on flexible walls

A method of reinforcing breakwaters with piles has been proposed. In this structure, designing piles as passive piles is important. Although most previous studies on horizontal subgrade reactions have been limited to the deformation mode of walls, the subgrade reaction to the wall is known to depend on the deformation mode of the wall. Herein, we investigated the changes in the subgrade reaction due to different deformation modes of the wall using model loading experiments and finite element analysis. The model ground was simulated using an aluminum rod mass, and an aluminum plate was used for the wall model. The model ground height was set to the horizontal ground condition with a 200 mm step at the front and rear of the wall. Lateral loads were applied simultaneously to the wall at two different depths. By controlling the ratio of the two levels of the lateral load applied to the wall, the deformation mode of the wall was altered. The experimental results indicated that the magnitude of the subgrade reaction at the same deflection depended on the deformation mode of the wall. The elastoplastic finite element analysis results of the lateral pile-head loading experiment in the horizontal ground condition exhibited good agreement with the experimental results. Under the two-point loading condition, the behavior of the wall was significantly different for cases in which the deformation mode differed from that of the lateral pile-head loading condition. By comparing the behavior of the ground around the wall, we discovered that the shear deformation of the ground differed depending on the deformation mode.

Structural Strengthening of Insufficiently Designed Reinforced Concrete T-Beams using CFRP Composites

This study aims to compare the response of reinforced concrete (RC) T-beams strengthened with carbon fibre-reinforced polymer (CFRP) composite with that of non-strengthened control beams when subjected to monotonic two-point loading until failure for flexural once and shear again. The experimental programme tested eight RC T-beams, which included two reference beams without strengthening and six strengthened beams. The eight beams were divided into two main groups according to strengthening (flexural and shear). Experimental analysis was performed to study the effect of the CFRP laminate width in the flexural group and the spacing of CFRP U-wrap sheets in the shear group on the ultimate load capacity, load-strain relationship, and load-deflection relationship. Results show that increasing the width of the CFRP laminate in the flexural group improves the ultimate strengths to approximately 9.5%, 35%, and 41% for beams with CFRP laminate widths of 50, 100, and 150 mm, respectively, compared with the reference non-strengthened beam. The stiffness of the beams increases in direct proportion to the width of the CFRP laminate. In the meantime, decreasing the spacing of the CFRP laminate in the shear group increases the ultimate strengths to approximately 13.2%, 17.7%, and 23.5% for beams with CFRP U-wrap sheet spacings of 166, 125, and 100 mm, respectively, compared with the reference non-strengthened beam. Therefore, the spacing of the CFRP sheet is inversely proportional to the stiffness of the beam. Doi: 10.28991/CEJ-2023-09-08-05 Full Text: PDF

Behaviour of Steel-Concrete-Steel Sandwich Beams with Novel Enhanced C-Channels

As the load increases, most composite beams generally experience failure in both shear and flexural behavior. This outcome highlights the critical challenges of achieving sufficient strength and structural integrity in such beams. The proposed study has used the cold-formed behavior of an Enhanced C-channel (EC) shear connectors and Light Weight Concrete (LWC) to examine the new Steel-Lightweight Concrete-Steel sandwich Beams (SLCSB). The ECs have provided significant shear resistance at the faceplate-LWC interfacial interface and the tension separation resistance for faceplates (cold form steel) from the LWC core. Cold Form Steel (CFS) is the most often used substitute because of its high productivity and practicality in the field. Four different composite beams are examined in the proposed research with different ECs spacing. The beams’ top and bottom face plates are covered using CFS (1.6 mm). In addition to that, two different types of shear connectors are used. Two unique longitudinal spacing of 100 mm and 150 mm are also used for one with lipped ECs and without lipped ECs. Importantly, self-tapping screws are used to secure ECs in place between the top and bottom of the face plates. The effectiveness of the composite beams with various shear connector spacing subjected to a two-point load test is assessed through a series of experiments.

Flexural tests on composite basement walls with socket-type shear connectors

The effect of a recently developed socket-type shear connector (SSC) on the flexural behaviour of a composite basement wall (CBW) was examined in this work. To this end, 12 CBWs composed of cast-in-place (CIP) piles fabricated with H-shaped steel beams or reinforcing steel plates were prepared by varying the arrangement and amount of SSCs. Two-point loading was applied to simply supported CBW specimens. The CBW specimens with more SSCs had a higher effective stiffness in the elastic state and higher moment capacity in the ultimate state, irrespective of the cross-sectional details of the CIP piles. These trends were particularly prominent when a reinforcing steel plate was used in the SSCs. The post-peak behaviour of the CBW specimens subjected to a simulated load with a negative external moment tended to be more ductile. Consequently, a higher degree of composite action was fully exerted on the CBWs with greater numbers of SSCs. Using established equations for the sectional details of CBWs with SSCs, the nominal partially composite to full composite flexural capacity ratios of the CBW specimens subjected to simulated loads with positive and negative external moments were calculated to be, respectively, 0.83 and 0.91 for 0.5ηsc and 0.79 and 0.90 for 0.75ηsc, where ηsc is the normalised shear connector capacity specified in ANSI/AISC 360-16.