Web Reinforcement Research Articles

Experimental and theoretical analysis on truss construction robot: Automatic grasping and hoisting of concrete composite floor slab

AbstractThe development of various construction robots can significantly reduce the construction labor intensity and risk. We present an experimental task of a truss construction robot, including automatic grasping and hoist positioning of concrete composite floor slab. And, a control strategy matching the construction robot is proposed to solve the following problems: (a) Due to the widespread manufacturing errors of building components, the position deviation of diagonal web reinforcement on concrete composite floor slab may cause grasping failure. (b) The chaotic surface of the floor slab seriously affects the recognition accuracy of the grasping target. (c) The large mass and inertia of heavy‐duty hanger and concrete composite floor slab make it difficult for robot to achieve accurate positioning under eccentric load condition. The machine vision recognition system ensures that if the diagonal web reinforcement is detected more than half of the grasping path, the grapple hook can change the grasping path independently to prevent it from colliding with the offset diagonal web reinforcement. An anticollision and grasping path planning method based on machine vision is proposed to improve the success rate and efficiency of automatic grasping. The mean value of proportional speed and proportional position is introduced as the evaluation speed and evaluation position of driving wheel to improve the accuracy of multiwheel synchronization. Moreover, we analyzed the robot performance from actual grasping and hoist positioning process of the concrete composite floor slab. The experimental results show that the robot has a good performance on the automatic grasping and hoisting of the concrete composite floor slab.

Experimental study on shear performance of basalt fiber concrete beams without web reinforcement

In this study, we report the results of an experimental investigation conducted under a four-point bending loading in order to evaluate the shear performance of concrete beams reinforced with basalt fiber without web reinforcement. According to the experimental results, it is evident that the final failure morphology of concrete-basalt fiber concrete composite beams and conventional concrete beams was shear failure, whereas the failure morphology of concrete beams reinforced with full basalt fiber was bending failure. Moreover, the results also indicate that the cracking load and ultimate bearing capacity of concrete composite beams reinforced with concrete-basalt fiber are lower than those of conventional concrete beam. This is mainly due to the interface between ordinary post-cast concrete and concrete reinforced with hardened basalt fiber. Due to the superior tensile properties of fiber, composite beams and all basalt fiber concrete beams exhibit a higher degree of ductility than conventional concrete beams. Utilizing the existing calculation theory for concrete beams reinforced with fiber, it was calculated that the cracking load and ultimate load of basalt fiber beams were calculated, and the calculation results were consistent with the experimental results. Based on the results of the evaluation and the theoretical analysis, this study proposes a finite element modeling method for basalt fiber composite beams. The results of the analysis were consistent with the experimental results of all investigated beams. The established model was employed in order to investigate the influence of shear span ratio on the shear performance of basalt fiber beams.

Hysteretic Performance of Hybrid GFRP-Steel Reinforced Concrete Shear Walls: An Experimental Investigation

The vulnerability of steel reinforcement to corrosion is a severe problem affecting the overall performance and durability of concrete structures in aggressive environments. The interest in using alternative Glass fibre-reinforced polymer (GFRP) bars lies in their corrosion resistance and higher tensile strength-to-weight ratio. Nevertheless, experimental results on the seismic behaviour of GFRP-reinforced walls are scarce. This paper investigates the hysteretic performance of hybrid steel-GFRP reinforced concrete shear walls to provide valuable experimental evidence for such walls under seismic loading. Six RC shear walls with steel and GFRP reinforcement were tested under pseudo-static reversed-cyclic lateral load. Three shear walls were reinforced by GFRP bars as longitudinal and transversal reinforcement, and two walls were reinforced with hybrid GFRP-steel bars with different ratios of web reinforcement. A reference specimen, ordinary steel-RC shear walls, was also introduced to certify the capability of GFRP as reinforcement bars. The results indicated that the GFRP-reinforced concrete slender walls had a stable hysteretic response and slight residual drift up to failure. Lower residual deformations, higher displacement capacity, and increased lateral strength could be observed with the GFRP web reinforcement ratio increase. Moreover, the fundamental period of GFRP and hybrid GFRP-steel reinforced walls can reach more than twice its original value prior to failure.

Force mechanism and conceptual design of reinforced concrete short beam without web reinforcement

Force mechanism and conceptual design of reinforced concrete short beam without web reinforcement

Seismic response of acceleration-sensitive nonstructural components in a Thin Lightly-Reinforced Concrete Wall (TLRCW) mid-rise building

Experience in recent earthquakes has shown that Non-Structural Components (NSCs) in multi-story buildings exert a significant influence on economic losses. Different topics about the seismic behavior of NSCs have been investigated; however more research is needed in several areas such as the type of building structural system and the type of seismic hazard. Motivated by this observation, floor accelerations in a novel structural system, namely the Thin and Lightly-Reinforced Concrete Wall (TLRCW) building, are examined in this paper. The TLRCW system comprises thin and slender walls with deficient or nonexistent confinement at the wall edges, and web reinforcements made of welded-wire mesh with limited ductility. In this study, seismic demands on NSCs in a TLRCW building are analytically calculated and compared with current characterizations included in earthquake-resistant building codes and presented in the literature. Comparisons are performed in terms of peak floor accelerations, floor spectra, inelastic displacement ratios, and the still not completely characterized inelastic absolute acceleration ratios. Influence of elastic and inelastic behavior of NSCs as well as of the structure is also evaluated. Since the TLRCW system is becoming common in some South American countries prone (in part or wholly) to subduction earthquakes, possible influence of the type of seismic hazard (i.e., crustal earthquakes or subduction earthquakes) is accounted for. It was found that, under design-level seismic demands, floor accelerations can be very large even though the structure undergoes a significant level of inelastic excursion. It was also found that floor accelerations are, for the most part, reasonably approximated by current characterizations. Finally, the type of seismic hazard has a negligible qualitative influence on floor accelerations (only minor quantitative differences were found).

Shear behaviour of infra lightweight concrete (ILC) without stirrups

ILC stands for “Infra” Lightweight Concrete, a versatile construction material that contributes significantly to building sustainability and opens up innovative architectural prospects. The prefix “infra” reflects a level of lightness that falls below the range of the structural LC in international standards. The novelty of ILC arises from combining such lightness (dry density ≤ 800 kg/m3) with both moderate strength and good heat insulative characteristics, rendering its application in monolithic cross sections without additional insulation layers feasible. This implies that complex multilayer façade systems including highly insulative materials can be substituted with a single layer of ILC, resulting in substantial improvements in terms of planning and construction simplicity, energy savings and recyclability. Recently, ILC has received great research attention, allowing for a better understanding of its physical and mechanical properties, which resulted in the successful construction of several ILC buildings in Germany. However, the structural behaviour of ILC has not been completely investigated and some structural concerns remain unanswered. This paper focusses on the diagonal cracking of ILC without web reinforcement as part of a comprehensive study into understanding the overall shear behaviour. 26 simply supported beams were tested until failure in 4-point bending configuration tests in order to study the role the concrete strength, the longitudinal reinforcement ratio and the a/d ratio play in the diagonal cracking of ILC. It was found that the excessive shrinkage of ILC significantly reduces the diagonal cracking load and results in rather wider cracks. Therefore, a design approach has been developed, where the excessive shrinkage impact was processed by reducing the tensile strength of ILC based on the shrinkage strain value. The diagonal cracking load seemed to be connected to the reduced tensile strength and the depth of the compressed zone, with no influence of aggregate interlocking or dowel action.

Shear behaviour of composite beams with permanent UHPC formwork and high-strength steel rebar

• The shear behaviour of UHPC-NC composite beams reinforced by high-strength rebars was discussed, where the permanent UHPC formwork and no web reinforcement were adopted. • Test parameters included the presence of UHPC and steel grids, type and thickness of formwork, strength of the NC, size of the steel grids and shear span ratio. • Based on the superposition principle, the ultimate shear capacity of the UHPC-NC composite beam was formulated. This study investigated the shear behaviour of ultrahigh-performance concrete (UHPC)-normal concrete (NC) composite beams reinforced by high-strength rebar. In the proposed UHPC-NC composite beam, the UHPC was used as a permanent formwork, and no web reinforcement was adopted. A total of twelve beams, including one reference NC beam, nine beams with pure permanent UHPC formworks and two beams with steel grid-reinforced permanent UHPC formworks, were examined via a four-point bending test. The examined parameters included the presence of UHPC and steel grids, type and thickness of the formwork, strength of the NC, size of the steel grids and shear span ratio. Three failure modes were observed depending on the shear span ratio, i.e., diagonal compression failure for a shear span ratio < 1, shear-compression failure for a shear span ratio = 1–3, and diagonal tension failure for a shear span ratio > 3. No obvious debonding was found between the UHPC formwork and NC, indicating that the interface processing method adopted in this study was effective. The test results showed that under the same shear span ratio, the shear cracking loads and ultimate shear capacities of the UHPC-NC composite beams increased by approximately 11.8–94.1 % and 16–66.6 %, respectively, compared with the reference NC beam. Among the bottom, side and U-shaped UHPC formworks, the U-shaped formwork provided the greatest improvement in the ultimate shear capacity. Based on the superposition principle, the ultimate shear capacities of the UHPC-NC composite beams were predicted.

Mechanical properties and shear strength of rubberized fibrous reinforced concrete beams without stirrups

• Presenting the experimental shear strength results of sixteen rubberized RC beams with/without fibers. • Investigating the impact of crumb rubber on mechanical properties and shear strength of concrete beams. • Investigating the effect of fiber types and ratios on the shear strength of rubberized reinforced concrete beams. • Investigating the effect of shear span to depth ratio on the shear strength of rubberized RC beams with/without fibers. This study investigates the mechanical properties and shear strength of rubberized reinforced concrete (RC) beams with/without fibers with no web reinforcement. A total of 16 RC beams were cast and tested under four points bending to fail in shear. The study parameters are; replacement ratio by volume of fine aggregate by crumb rubber (CR) (0, 15, 30, and 40%), types of fibers (hooked long steel fiber, smooth short steel fiber, and polypropylene fiber), fiber volume fraction (0, 0.4, and 0.8%) and shear span to depth ratio a/d (2.5, 3.5, and 4.5). The results show that the mechanical properties of rubberized concrete and its weight are reduced with increasing the CR content due to the low strength, stiffness, and elastic modulus of CR, while the addition of different types of fibers, particularly hooked large steel fiber, significantly improves the mechanical properties of rubberized concrete. Using lightweight CR contributes to increasing the deformability of the tested beams and reducing their self-weight. However, increasing the CR content decreased their ultimate shear force, post-diagonal crack shear resistance, and energy absorption capacity. The inclusion of CR and fibers in concrete production can be considered as a potential technique to develop new types of eco-friendly concrete with decreased self-weight and exhibits higher shear strength than that of the control beam. Moreover, the comparison of experimental results with the predicted results of five codes and six equations from the literature showed that most of them overestimate the shear capacity of rubberized RC beams; therefore, a new predicted equation is required to predict the combined effect of rubberized fibrous RC beams.

Modified interactive strut-and-tie modeling of reinforced concrete deep beams and corbels

In this study, a strut-and-tie model (STM) for predicting the shear strength of reinforced concrete deep beams and corbels was proposed. The model was derived on the basis of two independent force-transferring mechanisms, namely, diagonal strut and truss mechanisms. The first mechanism was modified from the so-called interactive strut-and-tie model (ISTM). The novelty comprises the derivation of a new proposed failure criterion of concrete used to develop the strength contributed by the strut mechanism. The truss mechanism represents the strength contribution from the orthogonal web reinforcement. The combination of the strength contributions from the two mechanisms results in the predicted shear strength. The model was calibrated on a large database of 682 deep beams and 338 corbels and verified using tenfold cross-validation. The shear strength predicted by the proposed STM was benchmarked against those computed using the original ISTMs and other state-of-the-art models. The comparison indicates that the proposed STM affords a more accurate prediction than the benchmark approaches.

Strengthening Shear Resistance of Beams without Web Reinforcements Using Vertical Prestressed Steel Bars

Ensuring the shear capacity of concrete structures is crucial. The vertical prestressed steel bar (VPSB) strengthening method is effective for improving the shear behaviour of concrete structures. Four concrete beams are investigated to reveal the effect of VPSBs on the shear capacity of concrete beams without web reinforcement. Test results indicate that the shear capacity of the test beam strengthened by VPSBs in the beam is significantly increased by more than 95%, and the failure mode of the test beam changes from diagonal tension failure to shear compression failure. Additionally, the results provide insights into the strengthening mechanism of VPSBs, i.e., the shear contribution of the VPSBs can be categorised into two stages. The vertical compressive stress provides shear contribution in the first stage and provides control in terms of crack development; meanwhile, in the second stage, the stirrup action by VPSBs contributes to shear.

Effect of steel fibers on the shear behavior of Self-Compacting reinforced concrete deep Beams: An experimental investigation and analytical model

The shear behavior of reinforced concrete deep beams made of self-compacting concrete with different volume fractions of discrete macro steel fibers (0.5%,1.0%, and 1.5%) is studied. All the beams are tested at shear span to depth ratio of 1.0, and the effect of loading plate width on shear carrying capacity is also studied. Similarly, the effectiveness of steel fibers in improving the shear behavior is compared with the beams made of plain concrete and the beams with 0.3% web reinforcement in both horizontal and vertical directions. Test results revealed that the addition of macro steel fibers significantly improved the performance of deep beams, particularly first cracking load, ultimate shear capacity, ultimate deformation, and ductility. However, the addition of steel fiber more than 1.0% volume fraction did not increase the ultimate shear capacity. A simplified analytical model is proposed to predict the ultimate shear capacity of steel fiber reinforced concrete deep beams. The existing cracking strut and tie method (CSTM) is extended to include the effect of fibers, and a simplified fiber-reinforced cracking strut and tie method (FR-CSTM) is proposed. Predictions of FR-CSTM are compared with CSTM and two-parameter kinematic theory (2PKT). The comparisons of predictions with test results and existing models show that the proposed method can capture the ultimate shear capacity of deep beams with reasonable accuracy.

Shear strength of reinforced concrete flexural members without web reinforcement in compliance with mechanical analysis

Reinforced concrete (RC) beams are important components and critical bearing members in concrete structures. Owing to the complexity of shear behavior for RC beams, most current design approaches to predict shear capacity are highly empirical, which cannot physically explain the shear failure mechanism and, consequently, should only be used within the bounds of the testing regimes from which they were derived. To accommodate this issue, a mechanics-based shear model, which can explain the physical process of shear failure mechanism with a clear physical meaning, was established to quantify the shear capacity of RC beams without stirrups with any type of longitudinal reinforcement and concrete. In this study, the force on each part of the critical failure diagonal crack plane of the RC beams without web reinforcement was analyzed, and the variation of sliding strength with any given inclination angle of diagonal crack was derived. Furthermore, the inclination angle of the critical diagonal crack along which failure occurs with the shear-span ratio was determined by the correlation analysis. The model was validated using 9 test specimens with steel longitudinal reinforcement performed in this study, with a further 452 published shear tests of FRP-reinforced beams without web reinforcement. In addition, the selected design codes and available models were used to calculate the shear strength of test beams. The comparison result shows that a reduction to different degrees in both the mean and scatter of the ratio of the experimental-versus-predicted shear capacity result for the proposed mechanics-based model. Meanwhile, the proposed model can accurately reflect the influence of the main shear parameters, and the prediction accuracy shows no obvious correlation with the wide range variation of these shear parameters.

Effect of Web Reinforcement on Shear Strength of Deep Beams and Crack Propagation

Effect of Web Reinforcement on Shear Strength of Deep Beams and Crack Propagation

사인파형 웨브주름 보강재를 이용한 저층건물의 내진보강에 관한 연구

In this study, a general low-rise building was selected to compare the new shear wall reinforcement method, which is a general method among the existing reinforcement methods, and the reinforcement method using sinusoidal corrugated web reinforcement. And it was confirmed that the following effects can be expected. Sinusoidal corrugated web members can be carried out in a short period of time as it does not require the removal of the masonry filling wall, the reinforcement of reinforcing bars, and the curing period of the concrete. It is effective in preventing damage that may occur when masonry filling wall is overturned in the out-of-plane direction, and the burden of the foundation is also reduced, and thus the construction period and cost required for reinforcement can greatly be reduced. By adjusting the number of sinusoidal corrugated web member, details of joints, and reinforcement positions, the flow of load can be induced to have an advantageous effect on the building. It can be considered as the most suitable reinforcement plan in terms of life safety. Unlike the shear wall that fills between the columns, the sinusoidal corrugated web members, which has a width of 1.5m, can install openings between two columns depending on the purpose of use, and can be expected to have a great effect in terms of usability due to its free installation location. As mentioned above, the seismic reinforcement using a sinusoidal corrugated web members, can expect great effect compared to conventional reinforcement methods in terms of usability, economic feasibility, and stability.

Shear Capacity Stochasticity of Simply Supported and Symmetrically Loaded Reinforced Concrete Beams

For shear tests of reinforced concrete (RC) beams, a simply supported and symmetrical loading system is usually applied. In deterministic analysis, shear capacities of the paired shear spans of such beams are the same. However, considering the randomness of concrete strength, geometric dimension, and other factors, shear failure often occurs in the weaker one of the paired shear spans of a beam rather than occurring in the two shear spans simultaneously. Therefore, from the perspective of probability theory, the shear capacities of the paired shear spans of such simply supported and symmetrically loaded beams can be regarded as two random variables with the same distribution. The beam shear capacity, which is the minimum of the two random variables, is also a random variable. Hence, probabilistic differences exist between the shear capacities of shear spans and beams. In this paper, the transformation relationship between the stochasticities of shear span shear capacity and beam shear capacity is theoretically derived. By taking the RC beams without web reinforcement as an example, the shear capacity stochasticities of shear spans and beams, which are valuable for reliability-based design codes, are quantitatively analyzed based on three shear strength models in design codes and a reliable experimental database. Their probabilistic differences are identified and verified to have an impact on the model calibration in the reliability analysis. The results also show that there are obvious differences in the shear capacity stochasticities obtained by different models. It indicates that to obtain the real stochasticity of the shear capacity, it is not enough to consider the model uncertainty merely but to minimize it. Therefore, models based on a solid understanding of the shear mechanisms are urgently needed for practical design.

Vertical shear capacity of steel-concrete composite deck slabs with steel ribs

The design of steel-concrete composite (SCC) deck slabs is likely governed by the vertical shear under small shear span-depth ratios. This paper aims to propose the calculation method of the vertical shear capacity of the SCC deck slab (Vu). Firstly, Vu is computed as the summation of the contributions of concrete layer (Vc,u) and steel members (Vs,u). Vc,u is treated as the product of the shear capacity of an equivalent reinforced concrete member without web reinforcement and a coefficient that reflects the effects of steel ribs. The formula of Vs,u is developed based on the force equilibrium conditions between the concrete layer and steel members and the section analysis considering the steel-concrete slips. Later, an iterative calculation method is proposed and verified against experiments and finite element (FE) models established via validated simulation techniques. Lastly, an extensive parametric analysis is implemented using the iterative method, from which a simplified calculation method was proposed and proved. Results indicate the iterative method is able to capture the effects of material and geometric parameters, shear span-effective depth ratio, and the degree of steel-concrete interaction. The increases in the heights of concrete layer and steel rib, as well as the rib thickness, can effectively enlarge Vu, while the influences of the steel plate’s thickness and the steel-concrete slips are relatively minor. The iterative method produces accurate predictions with a mean error of 1% and a coefficient of variation of 0.05. The simplified method is more engineer-friendly and yields the average FE/test-predicted ratio being 1.11 as well as the percentage of safe predictions being 95%.

Theoretical and experimental study on shear behaviour of hybrid fibre-reinforced concrete deep beam

This paper proposes an analytical method for predicting the shear capacity of hybrid fibre-reinforced concrete (HFRC) deep beams based on the softened strut-and-tie model. Moreover, a test was conducted to evaluate the proposed method and further investigate the shear behaviour of HFRC deep beam. The shear and deformation capacities of HFRC deep beams increased with the steel fibre volume. The shear capacity also increased with the web reinforcement ratio; however, the deformation capacity first increased and then slightly decreased. The steel fibre volume slightly affected the HFRC deep beam stiffness, and the increase in web reinforcement ratio improved the stiffness retention. The strains in concrete and reinforcement in the HFRC deep beam were relieved by the increase in the steel fibre volume. Although the increase in the web reinforcement ratio reduced the strain in the HFRC deep beam reinforcement, it only slightly affected the strain in the concrete.

Efficiency of Strut-and-Tie Model for Design of Reinforced Concrete Deep Beams without Web Reinforcement

Efficiency of Strut-and-Tie Model for Design of Reinforced Concrete Deep Beams without Web Reinforcement

Shear Strength Estimation of Reinforced Concrete Deep Beams Using a Novel Hybrid Metaheuristic Optimized SVR Models

This study looks to propose a hybrid soft computing approach that can be used to accurately estimate the shear strength of reinforced concrete (RC) deep beams. Support vector regression (SVR) is integrated with three novel metaheuristic optimization algorithms: African Vultures optimization algorithm (AVOA), particle swarm optimization (PSO), and Harris Hawks optimization (HHO). The proposed models, SVR-AVOA, -PSO, and -HHO, are designed and compared to reference existing models. Multi variables are used and evaluated to model and evaluate the deep beam’s shear strength, and the sensitivity of the selected variables in modeling the shear strength is assessed. The results indicate that the SVR-AVOA outperforms other proposed and existing models for the shear strength prediction. The mean absolute error of SVR-AVOA, SVR-PSO, and SVR-HHO are 43.17 kN, 44.09 kN, and 106.95 kN, respectively. The SVR-AVOA can be used as a soft computing technique to estimate the shear strength of the RC deep beam with a maximum error of ±3.39%. Furthermore, the sensitivity analysis shows that the deep beam’s key parameters (shear span to depth ratio, web reinforcement’s yield strength, concrete compressive strength, stirrups spacing, and the main longitudinal bars reinforcement ratio) are efficiently impacted in the shear strength detection of RC deep beam.

Numerical and theoretical analysis of FRP reinforced geopolymer concrete beams

The current paper aimed to numerically and theatrically evaluate the flexural performance of polymer bars reinforced geopolymer concrete (FRP-GPC) beams based on applying numerical and theoretical investigations. The numerical study incorporates developing nonlinear finite element models, using ABAQUS software, validated with the data available in the literature. The developed model was then utilised to implement parametric studies for the parameters governing the structural behaviour of FRP-GPC beams, including compressive strength, FRP reinforcement type, shear reinforcement ratio, and shear span-to-depth (a/h) ratio. The results indicated to a reasonable agreement between the FE results and experiments collected from the literature concerning failure mode, failure load, and the load-deflection response. The statistical calculations showed that the mean, standard deviation, and the coefficient of variation between the measured and the FE failure loads are 1.03, 5.4%, and 5.3%, respectively. The FE results indicated that the compressive strength plays a considerable role in the load capacity for the specimens made without any web reinforcement, unlike those supported with web reinforcements. Moreover, the absence of web reinforcement and low a/h ratios resulted in a shear behaviour, which is more likely to be controlled by compressive strength rather than other parameters. The FE results also indicated that the web reinforcement ratio of 0.7% was sufficient to avoid the occurrence of shear failure, and therefore, the increase of the shear reinforcement beyond this level seems to have no considerable impact on the load capacity. Besides, the theoretical study included assessing the Canadian (CSA S806–12) and American (ACI-440–1R-15) codes to evaluate their performance in predicting the loading capacity of FRP-GPC beams investigated in the current study. The findings indicated that both codes provided conservative predictions when they are applied on FRP GPC beams, giving a mean value of 0.66 for the calculated-to-the FE results. Therefore, developing the existing design standards of ACI-440–1R-15 and Canadian CSA S806–12 is strongly recommended to improve the accuracy of applying these codes on FRP GPC beams.