Vertical Rebar Research Articles

Mechanics-based machine learning for failure classification of load-bearing walls

This paper presents novel methodologies that combine analytical mechanics with artificial intelligence to classify the failure mode of reinforced concrete walls under lateral loading. The adequacy of existing approaches is examined, including design equations and established machine learning algorithms, against experimental datasets consisting of 330 specimens. Findings indicate that the machine learning algorithms outperform the empirical design equations in terms of failure mode classification; however, the former lacks physical interpretability. To address this limitation, a new concept is proposed by integrating analytical and computational platforms for identifying attributes that dominate the failure characteristics of the walls. Non-dimensional features are derived and substituted into the machine learning algorithms. The aspect ratio of the walls and the amount of vertical rebars in boundary elements are found to be salient factors when categorizing failure modes, followed by the amount of horizontal rebars in the web. Through the application of decision boundaries stemming from the mechanics-based machine learning protocol, design recommendations are suggested to effectively classify the failure mode of load-bearing walls.

Study on seismic behavior of prefabricated shear wall with pressed cone sleeves (PCSs)

Current prefabricated shear walls predominantly utilize grouting sleeves for connection, whereas an in-depth review and summary of the current state of research have indicated a 26.7 % construction defect rate in these sleeves due to present construction techniques. To solve the problem of defects, this study introduced a novel prefabricated shear wall design using vertical rebars connected via pressed cone sleeves (PCSs). Three reinforced concrete (RC) prefabricated shear walls with different vertical rebars connected and tested under cyclic horizontal load and constant vertical load to study the seismic performance, including cast-in-situ shear wall (specimen SW1), partial sleeve grouting defects shear wall (specimen SW2) and shear wall with vertical rebars connected via PCSs (PCSs-SW, specimen SW3). Key performance indicators such as failure modes, hysteresis curves, shear capacity, stiffness, ductility, energy dissipation capacity and stress characteristics were evaluated. The results of the tests revealed that SW1 and SW3 failures resulted from a combination of bending moment and shear force, whereas SW2 failure in the area of grout sleeve defects connection. Compared to the specimen SW2, the SW3 owns better shear bearing capacity, ductility, stiffness, energy dissipating capacity and reliable seismic performance. Meanwhile, SW3 and SW1 exhibited the similar seismic performance, can primarily achieve the effect of “equivalent cast-in-situ”. Finite element (FE) model of specimen SW3 were developed by using software ABAQUS, and the precision and utility of FE models verified by testing data. Using proposed FE models, an extensive parametric study was conducted to investigate the influencing factors on the seismic performance of precast fabricated RC shear wall, including axial compression ratio, concrete strength, vertical rebar strengths and vertical rebar diameters.

Pullout test for PC column-capital grouted rebar connection with corrugated duct

Double-beam precast concrete (PC) structures require large capitals to support a wide PC girder. In this study, a segmented PC column-capital system is developed to overcome the disadvantages of conventional PC columns in terms of manufacturing, transportation, and construction. In the proposed segmented PC column-capital system, large PC capitals are assembled with PC columns using the proposed corrugated rebar connections filled with grouted mortar. To verify the load-transfer capacity of the proposed corrugated rebar connections, pullout load tests are conducted under various test parameters, including the mortar compressive strength, curing time, bond length, and embedment length. To enable rapid construction, a relatively short curing time of 1–2 days is addressed. The test results indicate that the pullout performance of the proposed corrugated rebar connection is primarily affected by the mortar compressive strength fm’ and embedment length ld. When fm’ > 7.9 MPa and ld = 800 mm, the proposed corrugated rebar connection transfers tensile loads corresponding to construction loads. When fm’ > 21.0 MPa and ld = 800 mm, the proposed rebar connection can resist the tensile yielding load of the connected vertical rebar even after one-day of curing. However, when ld is less than 800 mm, bond-slip failure occurs because of the insufficient bond length. Based on the test results, a parametric analysis is conducted using a finite-element model. Similar to the experimental result, the numerical result shows that the bond strength of the proposed rebar connections is significantly affected by fm’ and ld. Hence, a bond-strength model of less-hardened grouted mortar with a bond stress of τb = 0.20 fm’ is suggested based on the previous and present test results as well as parametric analysis results.

Bond Strength of Reinforcing Steel Bars in Self-Consolidating Concrete

This paper presents an experimental investigation of the bond strength of reinforcing steel bars in tension in self-consolidating concrete (SCC). The effects of the reinforcing bar’s location, orientation, size, and coating on the bond strength with SCC were studied and compared to those with conventionally vibrated concrete (CVC). Several SCC mixtures were developed to cover a wide range of applications/components and material types. The fresh properties of the SCC mixtures were determined to evaluate their filling ability, passing ability and stability. Two hundred and thirty-four pull-out tests of rebars embedded in cubes, wall panels and slabs were conducted. Almost half of the tests were conducted to evaluate the bond with SCC and the other half with CVC. Load–slippage relationships were measured for each test. Pull-out test results were analyzed, and the bond strength was reported in two values: critical strength, which corresponds to slippage of 0.01 in. *0.25 mm); and ultimate strength, which corresponds to the maximum load. The critical strength of SCC and CVC were compared against the ACI 318-19 provisions and comparisons between the ultimate strength of SCC and CVC were conducted. The comparisons indicated that SCC has lower bond strength with vertical rebars than CVC, and a 1.3 development length modification factor is recommended. A similar conclusion applies to epoxy-coated and large diameter rebars. Also, SCC with high slump flow has shown a less top-bar effect than that of CVC.

Seismic performance and deformation mechanism of precast single-face superposed shear wall

The application of single-face superposed (SFS) shear walls in high-rise residential buildings within seismic zones has attracted extensive attention in past years, but the seismic performance of SFS shear walls hasn't been well understood yet. This study presents the results of quasi-static cyclic tests on four precast SFS shear walls using different horizontal joints and one cast-in-place (CIP) shear wall. The main objective is to achieve a thorough knowledge of the deformation behavior and deformation mechanism of SFS shear walls by analyzing the experimental results describing the global and local deformation behaviors. In general, SFS shear walls behaved equivalently to or even slightly better than the CIP shear wall in terms of bearing capacities, ductility properties, stiffness degradations, and energy dissipation properties. However, unlike the flexure-shear-dominated deformation mode of the CIP shear wall, SFS shear walls were primarily dominated by rigid body rotation behavior and secondarily by flexural-shear deformation. Based on the experimental results, the significant influence of the strain development of vertical rebars, opening, and slip at the horizontal joint on the deformation behavior of SFS shear walls was discussed. It was found that the continuously increasing opening, the sequential yielding of vertical rebars, and the slip at the horizontal joint together led to the difference in deformation behavior between SFS shear walls and the CIP shear wall. Therefore, future work will investigate whether SFS shear walls could emulate well CIP shear walls if the severe deformation at the horizontal joint is greatly reduced.

Seismic performance of precast concrete shear wall using grouted sleeve connections for section steels reinforced at wall ends

A novel precast concrete (PC) shear wall was proposed by disconnecting the vertical rebars in the middle zone of the wall and using grouted sleeve connections for section steels at wall ends. The advantage of this method is to alleviate constructional difficulties when assembling traditional PC shear walls. As an extended study, this paper investigates the seismic performance of the PC shear walls. Four wall specimens of 1:2 scale were tested under pseudo-static loading, including two cast-in-place (CIP) specimens and two PC specimens with different axial compression ratios. Afterwards, parametric studies were performed using the finite element method, considering the axial compression ratio and yield strength of section steel. Test results indicated that the PC and CIP specimens had comparable ultimate resistances, and exhibited similar ductilities and stiffness degradations. The energy dissipation capacities corresponding to ultimate resistances of the PC specimens were 41% and 19% smaller compared to those of the CIP specimens under axial compression ratios of 0.3 and 0.5, respectively. Numerical results found that the ultimate resistances of the PC shear walls increased by 59% when the axial compression ratios increasing from 0.1 to 0.6. Increasing the yield strengths of section steels from 235 MPa to 460 MPa, the ultimate resistances of the PC shear walls slightly increased by 11%, and the energy dissipation capacities improved by 26%.

Cyclic loading test for lightly reinforced exterior wall with openings

Recently, slender and lightly reinforced exterior walls with large openings have been frequently used in high-rise residential buildings for economical construction. Although the exterior walls can be severely damaged by moderate earthquakes, minimum reinforcement is used, and the seismic details are not used in the current design practice because it is assumed that the seismic performance of the exterior walls is not significant in the entire structure. To investigate the strength and damage mode of the exterior walls, four exterior wall specimens with openings were tested under cyclic lateral loading. The main test parameters were the type of the openings (i.e., small, horizontal slot, vertical slot), and the reinforcement ratio in the horizontal components (horizontally 0.42–1.29%, and vertically 0.28–0.89%). The test results indicated that the peak strengths of the exterior walls with large depth of the horizontal components reached the nominal flexural strengths calculated by assuming solid walls and neglecting the opening effect. However, due to the premature tensile fracture of the vertical rebars, the lateral stiffness was significantly degraded, and the energy dissipation was limited. Further, the maximum crack width was affected by opening type and reinforcement ratio. A parametric study was conducted using a finite element (FE) model to investigate the effects of the design parameters. Based on the test and analysis results, a design recommendation for exterior walls with openings was provided. The exterior walls can be designed as solid walls under the following limited conditions: the total opening areas are less than 10% of the wall area in elevation, the relative flexural stiffness of the horizontal components is greater than the lateral stiffness of the walls, and the axial load ratio is less than 10%. Further, the allowable lateral drift ratio for permissible crack damage was suggested to be 0.10%.

STRUCTURAL PERFORMANCE EVALUATION BY FLEXURAL ANALYSIS ON RC DAMAGE-CONTROLLED FLAT WALLS RESTRAINED AXIAL ELONGATION

This paper proposes a method of flexural analysis for structural performance evaluation of the RC secondary flat walls without wall vertical rebar anchorage. An idealized deformation model for the walls restrained axial elongation was also proposed and applied to the flexural analysis. Consequently, the results from the flexural analysis had good agreements with the experimental results, which identified the failure mode in flexure of the tested specimens. Furthermore, a simple theoretical equation was proposed to quantitatively estimate the maximum compressive axial force applied on the flat walls based on the above idealized model.

A simple but effective capacity model for check and design of beam-column joints in RC seismic buildings

The design of beam-column joints is a crucial step of the design of seismic-resistant RC framed structures. Premature joint failure may prevent yielding of beams and the achievement of the target collapse mechanism. Hence, an effective capacity model is essential. In the past, Italian building code in force before NTC (2008) required that a minimum amount of ties, equal to that used in the column, be provided in the joint, but it did not stipulate any verification of the joint. Eurocode 8 (2005) and subsequently Italian NTC (2008 and 2018), recognize that shear in beam-column joint is higher than in columns and recommend the explicit verification of the joint. The suggested capacity model is based on stress analysis and is very demanding in terms of joint ties. The new draft of Eurocode 8 (2020) provides a different capacity model, based on research carried on by Fardis (2021), which better reflects the state of art on this topic under both theoretical and experimental point of view. This paper examines the capacity model for shear resistance of joints adopted in Eurocode 8 draft, underlining its advantages but also some difficulties in practical application. Based on a parametric analysis of a wide set of RC joints, it is showed that it is possible to assume that the joint rebars are yielded when the joint attains its ultimate limit state. This assumption does not determine any significant loss of precision in evaluating the shear resistance of the joint and leads to a capacity model consistent with other models adopted in Eurocode 8, e.g. those for shear resistance of RC beams. Furthermore, it allows a closed form solution of the problem that leads to a very simple procedure both for the verification of joint resistance and for the optimization of the design of horizontal and vertical rebars of the joint.

Detection of grout sleeve defects based on the time domain dimensionless indicators of component signals

In recent years, precast concrete structures have been widely used in building and bridge engineering. Grouted sleeve connectors (GSC) are extensively applied to connect vertical rebars between precast concrete members. In practical construction, defects, such as no grouting, insufficient grouting, and missing rebar, often exist in the GSC, which reduces the load-bearing capacity. Therefore, detecting GSC defects is important for the safety of precast concrete structures. In this paper, a numerical model of meso-scale GSC concrete was developed. The model was verified by test data from existing literature. The ultrasonic wave signals in the GSC with and without defects were compared in detail. The signals were decomposed based on wavelet packet transform and empirical mode decomposition. Then the time domain dimensionless indicators were extracted to examine the GSC defects. The proposed method was shown to be superior in detecting the GSC defects with high sensitivity.

Fibres as Replacement of Horizontal Ties in Compressed Reinforced Concrete Elements: Experimental Study

Steel fibres provide ductility to concrete structures. This, in turn, gives possibility to replace or reduce conventional reinforcement in structural elements. In this study, the focus is on structural walls and the fibres as potential replacements for horizontal reinforcement in areas where vertical rebars are needed. An experimental study was conducted, in which prismatic specimens with longitudinal rebars were subjected to centric loading. Ten samples with 12 specimens in each were tested. The parameters considered were: fibre content, concrete cover for the longitudinal bars, and presence of stirrups. Self-compacting concrete with 30 and 60 kg/m3 steel fibres was used. Relative and normalised values of the test results were calculated; correlation and analysis of variance was used to estimate the effect of fibres. The results show that the fibres eliminated brittle collapse and spalling of concrete at failure. A strong negative correlation (−0.72 to −0.92) between amount of fibres and load-bearing capacity was found. On average, the reduction of the capacity was 8% to 16% if compared to the specimens with no fibres. However, a positive effect of the fibres on the ductility was observed. Specimens with 30 kg/m3 fibres showed the same post-peak behaviour as specimens with minimum horizontal reinforcement required by Eurocode 2. The study suggests that combination of steel fibres and conventional rebars can lead to less qualitative compactness of the self-compacting concrete, which in turn may reduce load-bearing capacity and stiffness of the structure. Special attention on concrete cover and distance between rebars should be paid if self-compacting concrete structures with steel fibres are designed.

Flexural retrofit of existing reinforced concrete structural walls with various boundary element details under cyclic loading

A recent regulation in Korea allows the rehabilitation of aging apartment buildings, with vertical extensions up to three floors. To satisfy the increased flexural strength requirement, a method that places vertical reinforcements and re-casts concrete after crushing the boundary elements is proposed. In this study evaluates the flexural performance of shear walls to which the boundary element retrofit method was applied. Six real-scale specimens were fabricated and reversed cyclic loading tests were performed. The experiments showed that the flexural strength increased as the vertical rebar ratio of the boundary element increased. As the development length of the post-installed rebar was reduced, the anchorage of the rebar was effective. When using shear studs to connect the existing and the retrofitted wall, the flexural strength was similar; however, the deformation due to shear was controlled. It was confirmed that a discontinuous strain distribution occurred. Based on the experimental results, a flexural design model under limited conditions was proposed, which accurately predicted the flexural strength. However, because there is a tendency to overestimate the tensile rebar strain, future studies should develop a flexural design model that can make a more accurate prediction by further analyzing the variables affecting the boundary element retrofit method.

Seismic behavior of prefabricated steel reinforced concrete shear walls with new type connection mode

This paper proposed a new connection mode of prefabricated steel reinforced concrete (SRC) shear wall. The vertical rebars inside the edge concealed columns of the prefabricated SRC shear wall were welded by lap welding, the section steels inside the edge concealed columns of the prefabricated SRC shear wall were welded by ending plates, and the connection of the wall panel in the middle part of the shear wall was realized through the bolt connection between the wall footing unit and the connecting steel plate. Then the concrete was finally poured in the connecting area of the edge concealed column of the shear wall. In order to study the seismic behavior of this new type prefabricated SRC shear walls, the pseudo-static test and nonlinear finite element analysis were carried out. At the same time, parameterized analysis was carried out on the key factors affecting the new type prefabricated SRC shear wall, including axial compression ratio, concrete strength grade, steel ratio of edge concealed columns, reinforcement ratio of vertical rebar section and thickness of connecting steel plate. The research results show that the failure mode of the new type prefabricated SRC shear wall is the same as that of the integrally cast SRC shear wall, and the seismic behavior and bearing capacity are slightly lower, but the difference is very small and in an acceptable range. The increase of axial compression ratio, concrete strength grade and steel ratio of edge concealed column will increase the bearing capacity of the new type prefabricated SRC shear wall, but at the same time, it will reduce the ductility of the new type prefabricated SRC shear wall. The reinforcement ratio of vertical rebar section and the thickness of the connecting steel plate have little effect on the mechanical performance of the new type prefabricated SRC shear wall. Finally, the reasonable value range of the key parameters affecting the mechanical performance of the new type prefabricated SRC shear wall and the calculation method of the shear capacity of the horizontal connection was proposed, which provided a basis for the subsequent design.

A NDT Method for Location and Buried Depth Measurement of Rebars in Concrete Pole

Accurate measurement of buried depth of rebars can effectively judge the durability of the Reinforced Concrete (RC) structure. However, most of the existing measurement methods cannot determine the deflection of rebar and do not consider the influence of factors such as the diameter and spacing of rebars, which resulting in low buried depth measurement accuracy. Therefore, this article takes the vertical rebars in concrete pole as the research object, and proposes a non-destructive method for location and buried depth measurement based on the magnetization effect. First, this article analyzes the influence of the magnetization effect excited by the rebars on the original magnetic field, and then designs the sensor layout to measure the magnetic induction intensity at different positions. Secondly, the central axis position and deflection angle of rebars are determined through comparing the measured data, and the buried depth is derived by applying the Support Vector Regression (SVR) algorithm. In addition, the proposed method is verified through simulation and experiments. Finally, this article discusses the influence of the diameter and spacing of rebars on the buried depth measurement, and uses the influencing factors as the inputs of the SVR algorithm model to correct the prediction results, which effectively reduces the maximum measurement error from 2.15mm to 0.36mm.

Cyclic Loading Test for Composite Walls with U-Shaped Steel Boundary Elements

A steel–concrete composite wall with boundary elements of steel U-section was developed for high structural performance and efficient use of materials. Cyclic lateral loading tests were performed on the proposed walls to investigate the flexural and shear performances. The test parameters included the failure mode of specimens, type of boundary reinforcement, sectional area of steel U-sections, horizontal web reinforcement ratio, and wall thickness. In the flexural yielding specimens, the flexural strengths of the proposed walls were equivalent to those of conventional reinforced concrete (RC) walls with boundary elements of vertical rebars, even though the yield strength of steel plates was 24% less than that of rebars. Further, the use of steel U-sections increased displacement ductility and energy dissipation, providing lateral confinement to the boundary concrete and restraining shear cracking and sliding. In the shear failure-mode specimens, the use of steel U-sections increased the diagonal tension-shear strength of walls. Thus, the shear strength of the composite walls was greater than that of conventional RC walls. The existing design method of JGJ 138 reasonably predicted the shear strength of the proposed composite walls, considering the contribution of boundary steel U-sections.

Investigation of five different low-cost locally available isolation layer materials used in sliding base isolation systems

The isolation systems based on sliding friction have gained the attention of researchers recently due to their low cost and high efficiency. The isolation layer plays a vital role in the energy dissipation and enhancement of the seismic capacity of an isolation system and is one of the crucial components of the friction-based isolator, thus needs to be designed carefully. Therefore, in this study, five different low-cost and locally available materials were utilized to fabricate the isolation layer and studied analytically, experimentally, and verified numerically. The isolation system under study consists of a low-lateral stiffness material with specific thickness, placed on the surface of low friction Teflon sheet having 3 mm thickness and is sandwiched between the superstructure and foundation. Furthermore, vertical rebars were distributed throughout the isolation layer to ensure the re-centering process. The cyclic behavior of all isolation layer materials was studied by conducting cyclic loading tests, for which the proposed isolation layer materials were sandwiched between two hollow concrete blocks. As friction is the primary source of energy dissipation, so standardized testing methodology was adopted to find the friction among the sliding interface. A detailed analytical study and modal analysis were conducted to identify the response of fixed and isolated models and some important parameters such as fundamental time-period, frequencies, and mode shapes. Based on the experimental study, the rubberized mortar among the others was found as a feasible material for the isolation layer. Later on, a detailed numerical study was conducted in Abaqus by creating a fixed-base and isolated models, whose dynamic behavior was studied under multiple seismic excitations. From the numerical study, the acceleration response reduction of 40%–53% was noticed at the top floor level of an isolated model as compared to the fixed-based model. The low cost and higher effectiveness of the proposed isolation system make it more robust to be used for low-rise masonry structures in developing countries.

Shear-flexural cracking strength of RC beams with external vertical prestressing rebars: Theoretical investigation and numerical simulation

This paper presents a semi-theoretical empirical formula to predict the shear-flexural cracking strength of an RC beam enhanced with the external vertical prestressing rebar (EVPR) technique. Besides, nonlinear finite element models (FEM) created by software ABAQUS were used to analyze the effect of crucial parameters on the shear-flexural cracking strength. The parameters involve shear span-to-depth ratio, concrete strength, longitudinal tension reinforcement ratio, initial pulling force and spacing of EVPRs, and the vertical stiffness of the EVPR supports. Results show that the cracking strength increased linearly with the tensile strength of the concrete and the initial pulling force. The small shear span-to-depth ratio was predominantly conducive to the cracking strength. Adequate longitudinal tension rebars contributed to the cracking strength improvement. A reasonable EVPR spacing was recommended to ensure the cracking strength. Greater vertical stiffness of the EVPR supports can ensure higher compressive stress for the RC beam to improve the cracking strength.

Influence of restrainer bar chairs on the compression and flexural behaviour of reinforced masonry walls

Lateral restrainers are traditionally provided in reinforced masonry (RM) walls to prevent the vertical steel bars from buckling. In the current version of the Australian Masonry Standards (AS 3700–2018), the use of lateral restrainers in RM walls is relaxed, if the vertical rebars are surrounded by grout annulus of twice the diameter of the bars. However, it is challenging to maintain the verticality of the reinforcing bars in the block cores to satisfy the grout annulus requirement without lateral restrainers. To address this challenge, restrainer bar chairs can be used in the construction of RM walls which are easier to employ in comparison to lateral restrainer ties. However, the implications of adopting restrainer bar chairs as an alternative to restrainer ties in RM wall construction are not well verified. In this study, the influence of restrainer bar chairs and conventional lateral ties restraining methods on the axial compression and out-of-plane bending characteristics of RM walls have been investigated. In total, twelve RM walls of dimensions 1390 mm height × 590 mm length × 190 mm thickness were constructed and tested, of which, four walls each were tested under concentric and eccentric compression and four-point bending. The experimental results revealed that the performance of RM walls with restrainer bar chairs and conventional lateral ties were similar, in terms of the observed failure modes, strength, load–displacement characteristics obtained under both compression and out-of-plane loading conditions. Strain measurements on rebars indicated that a composite action was ensued in both restrainer configurations. The capacities of the RM walls under compression and out-of-plane bending were also verified with three different masonry standards provisions and were found adequate with reasonable safety. Overall, it can be concluded that the restrainer bar chairs can effectively be used in RM walls to enable quick and accurate vertical positioning of the rebars and ensure adequate grout annulus around them.

Seismic Performance of a New Type Steel-Concrete Composite Shear Wall

Using steel-concrete composite section is an efficient method for improving the behaviour of shear wall under seismic action. In consideration of the complex configuration of traditional composite shear wall and the time-consuming constructing process, based on the existing research, partially encased composite section was introduced into shear wall system. The partially encased composite shear wall (PECSW) is composed of a steel bone, some horizontal links and a group of concrete columns. The steel bone is a steel web, welded with vertical ribs and flanges in both side at certain interval. The horizontal links connect the flanges (or vertical ribs) and vertical ribs. Concrete is poured on both sides of steel web, between flanges (or vertical ribs) and vertical ribs, formulating several independent long concrete columns. The PECSW can be bulk prefabricated in the factory and transported to the site to install. Because of no vertical rebar in PECSWs, the PECSW structure, which consists of PECSWs and other precast concrete structural elements, can be assembled quickly. This paper reports an experimental study on the seismic behaviour of the PECSW under cyclic lateral loading. Two full-scale single-bay, single-story specimens were constructed. The bearing capacity, energy consumption, stiffness and other performance data had been discussed based on the results of experiment. To explore the possibility of simplifying configuration of PECSW, the web of one specimen was welded with stud shear connectors on both side while the web of another specimen wasn’t. The test results show that the PEC shear wall has a good seismic behaviour. Both specimens followed bending failure mode. The concrete columns offered the vertical bearing capacity as well as the flexural bearing capacity. The concrete and the horizontal links between flanges and ribs provided effective support against local buckling of the flanges, once broken occurred between the links and the flanges, the flanges buckled severely, and the bearing capacity of PECSW fell accordingly. The initial stiffness, yield drift, peak point bearing capacity, accumulated energy dissipation of the PECSW specimens with and without stud shear connectors was basically identical. Then, parametric studies were conducted through numerical simulation so that the contribution of links and the stud shear connectors can be evaluated. According to the research above, the concrete part in the PECSW can postpone local buckling of steel sheet. The horizontal links in the PECSW support interaction between steel and concrete, provide concrete anchorage to steel bone. In general, the PECSW has commendable seismic behaviours and deserve further study.

Influence of rebar geometry on the steel-concrete interface of reinforced concrete

This paper investigates the effects of rebar geometry, namely the rib and diameter of rebar, on the steel–concrete interface (SCI) and corrosion initiation of reinforcing steel. Cutting-induced damage on the SCI is also studied using various W/C ratios, cutting wheels and rebar diameters. Interfacial porosity and the distribution of chloride ions at different locations with respect to the rib of vertical rebar and the phase distribution of the SCI of horizontal rebar with various diameters is quantified. The results show that a macroscopic gap can be found below the rib of vertical rebar. Corrosion initiation of vertical rebar is associated with interfacial porosity at different locations with respect to the rib of vertical rebars. Local water content near the SCI of horizontal rebar is increased when using a larger rebar diameter. Cutting-induced damage can be reduced by decreasing the water to cement ratio and rebar diameter.